| moray james |
Am trying to get enough information to understand the necessary parameters for a ripole sub driver. Optimum characteristics for different size drivers. Seems that Qt increase as driver size decrease and decrease as driver size increases. What about cone stiffness and driver mass? What about acceptable linear excerssion? Larger cones would not have to move as far but what are the practical excursion ranges.? Would like to be able to search for suitable drivers but from looking at published designs it seems that there are no set parameters with many different drivers being used.
It would seem to me that dual ripole systems are the best compromise and that larger drivers in the 15 to 18 inch range would be the most practicle way to overcome the largest and most common complaint of this design which is output. Ripoles are not the most efficient design but they would seem to be the most compact. For home theate systems where outputs above 105 db at low frequencies are desired it would appear that either multiple dual 12 inch ripoles are required (and this makes good sense in terms of driving the room) or a smaller number of 15 - 18 inch dual ripoles. I am wondering where the turning point is. Larger drivers 15 - 18 inch usually end up costing more and long throw versions are not as common as the mechanics become more involved with the higher mass structures which is part of the increase in cost. The 12 inch driver would seem to be the best all round compromise in terms of moving a lot of air and keeping the cost from getting out of hand. For a given size of motor the 12 inch represents the best balance that I can see in the market place from a cost/performance point of view.
I understand that people want/need to generate large outputs of bass in HT systems and want to get as much as they can from as few boxes as is possible but really high output at low frequencies usually gets very large or very inefficient when made smaller. Interfacing large single cabinet subs into a room does not seem to be the answer.
I am also interested to know from those with hands on experience how much of an issue ported pole noise is in ripole sub designs. Hope that we can have a polite and useful intercourse here as this topic has had some heated differences of opinion in the past. I would like to get past that to discussing the reasons behind those differing opinions. Regards Moray James. |
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| Kensai |
I'll second the need for more detail information on this subject.
James - if you'll allow 12" drivers, I've been wanting to try this one - Cheap Pyle Woofer . Cheap enough to experiment with, really good reported specs for dipole use, and in ripole, you can hide just how ugly the thing is.
Another tidbit I want to throw out there is that I was told by one of the more active OB "authorities" here that the depth of the ripole chamber (the dimension of the space parallel to the driver face) has something to do with the unit's roll off point. He seemed to be able to predict what that point was, so there must be some mathematical work out there we can start from.
Kensai |
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| moray james |
| The Eminence series Alpha and Beta 15 inch units look promissing for inexpensive 15 inch units. Though these units do not have very high Xman they do have Qts values that would be better than average and this will help to bump the response at low frequencies. The fact that these are 15 inch units should also help matters. I guess the question is how much excurssion do you need to have good output with larger drivers like 15-18 inch? Regards Moray James. |
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| moray james |
This driver is not to expensive and I have found it discounted to about $115.00 Cnd. Fs-41 Hz., Qts-0.58, xmax-4.8 mm, xlim-16.5 mm cone mass 64 grams, efficiency is said to be 96 db. This a tad high (Fs) but ripole mounting should bring response down into the low 30's and a pair of these should move considerable air. Any comments. The big question is will the suspension handle being pushed on a ripole cabinet?
Does any one know when Peerless will release the 15 inch SLS, I have heard talk of Dec. this year? |
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| maudio |
I use the Peerless XLS 12 (830500) in my dipole (not ripole) subs, the same driver proposed by Linkwitz.
They don't come cheap, but they do have very large Xmax (25 mm lin, 40 mm max) which gives it a pretty good air displacement vs $$ ratio :D
Using only one per channel I can still reach very realistic SPL's. However it must be said that I am not using them for home cinema and I am not aiming for 105 dB @ 20hz...
Because of the open voicecoil construction there is no pressure building up under the dust cap, so no strange noises at large excursions. This is very important in D/Ripole application.
All in all I am very pleased with their performance.
I believe that for high-quality applications drivers > 12 " are not advisable...
just my 0.02 :) |
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| Klimon |
| quote: | | Another tidbit I want to throw out there is that I was told by one of the more active OB "authorities" here that the depth of the ripole chamber (the dimension of the space parallel to the driver face) has something to do with the unit's roll off point. He seemed to be able to predict what that point was, so there must be some mathematical work out there we can start from. |
That's the only cabinet variable so it would be great to know how it affects cut-off. I'm also planning a pair of ripoles using cheap 12" car subs. Easiest solution would be to take the chamber dimensions given on the lautsprecher.de website and measure the result, then try a bigger chamber and test that one, benefitting from the little work needed to build a ripole cab.
Simon |
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| Kensai |
Klimon,
I'm not meaning the width of the airspace from the driver face to the panel in front of it. That is the only variable, and from the same person I got the impression that that should be as shallow as possible, but more in a second.
What I was meaning was the "depth" or the across the driver face measurement. Like if you were using 8" drivers, it would be 8.5"-9", if you were using 15"ers, it would be 16"-18". That sort of thing.
Anyway, as for the width of the airspace chambers, I've gathered that narrower is better. What should be done is that the rear panel should have a hole cut in it to clear the driver's magnet. You'll want this panel to basically rest up against the joint of the basket and the magnet. Its also been recommended that the baffle, the middle panel that the driver is mounted to, be made thicker, to also compress this volume though you still have provide airflow clearance (rounding over or chamfering the back edge of the cutout). Then you simply make the front air chamber the same width (or possibly a bit less if you feel the magnet volume should be accounted for).
I'm sure there's a fairly early point of diminishing returns, but I think the cost is in driver efficiency, not distortion as these compressed air chambers actually act as partial acoustic suspensions, proping up the cone on both sides which will limit excursion to some degree.
As for drivers, I don't think the Peerless XLS are ideal. I know Linkwitz uses them in OB, but have you seen the amount of EQ he uses and amount of power he needs to feed them properly? Sure, they're pretty high quality drivers (not to mention pricey). They're rugged and can handle the high amp, heavily EQed abuse of drivers in OB that are intended for BR application. As long as you've got more power, you can get more dB out of them. There's another line of Peerless (can't remember the designation off hand) that is much cheaper (less than half), has less Xmax (about half), but has much higher Qts. If memory serves, the specs were very similar to the driver the ripole originator was using. Anyway, it looks like the quickest way to get in and try this out is really cheaper drivers, like the low end (and highest Qts with lowest Fs) Pyle Pro drivers, or various cheap car subs (again, some Pyle models come to mind first), providing you can find specs on them. As far as I can tell, you're looking for the highest Qts/lowest Fs combo you can get while making sure the driver is rugged enough to handle some mild abuse (though just from driving, as the ripole alignment is ideal for physically protecting a driver).
So, who's going to start building ;)
Kensai |
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| moray james |
I have found out that Eminence state thier Xmax figures as Peak values so doubel the distance if you are used to dealing in terms of peak to peak (as Peerless does). I am awaiting confirmation that they also state Xlim (mechanical limit (read damage)) in peak values as well and I will post that info as soon as I have a reply from Eminence tech support.
Maudio I am interested to hear your reasons for why you feel that larger than 12 inches for a dipole/ripole is not a good idea. Putting aside the size/cost issues I would think that with a suitable motor structure and with suitable parameters larger would in fact be better.
Klimon: yes this is the kind of information needed to be able to manipulate cabinets to work with available drivers. Kind of a working explaination or how to. Chamber size is the other variable and we need to understand the relationship between driver parameters and the cavity volumes. I have been told that the rear volume does not have the same degree of importance as the front cavity. This makes sense from a strictly dipole point of view in that the cabinet is simply a folded baffle. However the Ripole/BMC concept is so compact that chamber pressure must surely impact cone motion and symetry of load should be considered if minimum distortion figures are to be expected.
From what I can see a wide range of driver parameters can be used in a Ripole design but Qts values 0.6 to 0.7 would seem to be the ideal range and suspension stiffness which is progressive would also be a great benefit. The largest single concern I see is one of air turbulence and the resulting noise it causes. For this reason vents below the spider and smooth open basket designs will go a long way to reducing such noise which will be high in such long throw designs. Dust cap removal may also be worth considering for drivers that do not have vents below the spider assembly. Pole piece vent noise must also be a concern and wire screen covers which are often placed on the back and or front side of ported pole pieces would also probably be best removed.
Chamber volume experiments would be best done with single drive Ripole cabinets to hasten construction time and to reduce cost. Perhaps those with experience can provide readers with a good general rule of thumb to find a reasonable starting point for cavity volumes.
Lastly I would point those who may be looking for a larger more powerful output Ripole to have a look at the Eminence Kilomax Pro 18. This driver is a Beast built like a tank and can be found for as little as $300.00 US funds each. I should think that for home applications These drivers in dual Ripole cabinets would be spectacular without breaking the bank. One of the badest drivers that I have come across for Riple use would be the McCauley 6174. While more than double the cost of the Kilomax I am sure these would be awsome in a Ripole or Dipole design. Something to drool over. Regards Moray James. |
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| MJK |
| What is a Ripole sub? What advantage does it offer compared to other subs? |
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| moray james |
is essentially a folded "W" dipole where the drivers are mounted face to face. The Ripole's polar response is moe cardioid than the figure of eight response of a true dipole. The Ripole claims to reduce both driver resonant point and cabinet size. See attached link. Typical driver Fs is reduced by 7 - 10 Hz. The Ripole is a velocity transducer rather than a pressure transducer.
http://www.boxenselbstbau.de/hifi/i.../aka_geh_en.htm
The Ripole is also said to further reduce driver distortions (running dual drivers) than will a more conventional nested driver configeration but I do not have any measured data to support that claim at this point. Most of the Ripole reseach and experimentation is going on in Europe at the present. Ripole's are less efficient by a margin than are dipoles and they will have somewhat less output however for normal home use dual 12 inch drivers can produce very low cutoff with acceptable levels with reasonable power requirements. So the main points are that of maximum low frequency cutoff in minimum volume. I have posted a number of links at the beginning of this list some of which pertain specifically to Ripole designs. I am also attempting to inlist several enthuiasts with experience in designing Ripoles to bring a broader base of information to this thread. It would seem that Ripole's require similar driver characteristics to those used in dipoles. Higher driver Qts helps with driver roll off and cabinet depth sets the frequency point where dipole cancelation occurs. That aside from some general rule of thumb guide lines is about as much information as I have at hand for the present. Given the small cabinet size and low cutoff for a given driver I am hoping that there will be enough interest here to start some local investigation on this side of the Atlantic.
Martin I appreciat your interest and look forward to your comments on this design be they for or against as they are sure to stimulate debate and discussion. Any assistance as to how to model a Ripole cabinet for a given driver would be most welcome. Regards Moray James. |
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| maudio |
Hi Moray,
the reason why I think that bigger isn't always better is that the bigger the driver, the more cone-breakup related problems it will have. I can't think of any high-end speaker using drivers >12" and there must be a good reason for that.. But of course a lot depends on the frequency range you are aiming for. And the 12" XLS isn't any good above 150 hz either...
But as I mentioned before, I wasn't aiming for earth-shaking spl's with my subs, I use them to assist my full-range esl's so quality not quantity was my first priority.
I looked at the ripole idea back then but in the end choose a simple H-baffle with only one driver to keep the costs down, keeping in mind I could always scale up to two drivers/channel if spl's would be insufficient (which they surely are not!).
Here's a small test you should perform when choosing your drivers:
Hold the driver in your hands and feed it a few volts of a clean 20 or 30 hz sine wave. Then listen for any noises it makes. As the unmounted driver will not produce any audible output at 20 or 30 hz it should be dead silent.
You'll find that most drivers will produce amazing amounts of hissing puffing breathing etc sounds, due to the air trapped under the dustcap. This air has to move in and out of the system through the very small voicecoil cap and/or a (not so big) hole in the magnet which can't be done quick enough at large excursions. Noises aside this also results in non-linear loading and distortion. Some drivers even manage to make strange flapping noises under this test. The only driver I could find at the time that was dead silent under this test was the XLS. This because it has an open spider so the air has a way out. This combined with it's air-moving capabilities and low distortion was decive for me.
Hope this is of any help,
Martin |
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| moray james |
I agree that the 12 inch driver is the standard in choice for large drivers (generally speaking) and I agree with your rational to a point. As I see it the reason that you give is correct in that bigger drivers do tend to have more cone break up problems. But that is not because of their size it is because they are not properly designed for their size. The simple reason for this is the associated cost of doing so. Past 12 inch in size all bets are off for the cost of build in other words everything has to ratchet up a notch or two in quality and size. So not only does the frame cone and suspension get larger so too must the motor and magnet assembly. All the costs go up (even packing and shiping) so designers try to cut back to save the added expense and so compromise. Properly designed large drivers can and do perfom every bit as well as their smaller brothers they just cost a lot more. Further to make a smaller driver perform as well as a larger (well designed) driver usually costs even more that the larger (well designed) driver. Take a look at some of todays super high performance 12 inch units and you will see that the special (uncommon) parts required push the cost up very high such that they can be replaced with good 15 or 18 inch drivers for less money and similar performance. The premiun you pay for the super 12 inch unit is all for the sake of size. Economy of scale factors in and you have to decide which things you really want to spend your money on or which specific criteria are most important to you. In the end I guess that you can have your cake and eat it too. Just happens that some cake costs more than others.
It would seem (for the moment) that the Peerless drivers are going to be hard to beat for value size and cost. But it never hurts to check out the options. Regards Moray James. |
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| Rudolf |
There has been stated a need for more detail information on the design of w- and n-dipoles, especially for construction or simulation programs. Actually it´s all there on the net – in English (mostly) and for free (restricted use). Lets have a look:
First there is “Akabak” http://www.akabak.de/Ak-English.htm . This is the very program Axel Ridtahler employed to do his “ripole” design. Akabak supposedly can do any acoustical computation you can think of, but be warned: Akabak is VERY complex and has a VERY steep learning curve as I was told.
Second is the “Horn Loudspeaker Response Analysis Program” aka “Hornresponse”, which can be downloaded at http://www.users.bigpond.com/dmcbean/
Further down I will explain how horn simulation programs can be used to do dipole/ripole simulations.
Third is aj-horn http://www.aj-systems.de/indexe.htm , another horn simulation program which is rather popular in Germany. You DEFINITELY should have a look into the English online manual on that website and the “Simulation of known enclosures” to see how w- and n-baffles could be simulated.
Last not least enter Basta! http://www.tolvan.com/basta/ , the loudspeaker sim prog of the man who gave us EDGE. In Basta! w- and n-baffles are simulated as a 2-ported band pass box, where the vents get the area and length of the dipole front and rear chamber.
Since there are no custom-made simulation applications for w-/n-baffles (yet), these di/ripoles are best simulated as either a front loaded horn with a vented rear chamber (if a vent can´t be simulated make the rear chamber as big as possible) or as a 2-ported band pass box. The trick is to give the horn or the reflex tube exactly the mouth/throat/tube area and the length of the di/ripole chambers.
All four programs have been reported to give comparable and quite accurate results. But remember: Some will include floor mirror and front/rear-wave influence at a chosen listening distance, others will only show plain free air performance.
I know that the above will do nothing for the quest of the best suitable driver, but it may help understand what varying the dimensions of the enclosure will effect. At least all programs take care of the driver TSP too, so you can estimate the influence of different Q-values.
Hope this is of help too.
Rudolf
I haven´t figured out yet, if any of MJKs worksheets http://www.quarter-wave.com/Models/MathCad_Models.html could do the job too. "Double bass reflex" possibly?? |
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| MJK |
| I don't think that any of the current worksheets will do the job. But it should not be too difficult to configure a worksheet that would do all of these and a few more, basically a driver loaded front and back with quarter wave pipes. Just a matter of finding the time and determining if there is enough interest to justify spending that time. Definitely interesting enclosure designs. |
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| Rudolf |
It´s a lazy day at work so I can contribute some more:
As MJK already stated those W/N baffles basically can be described as a driver loaded front and back with quarter wave pipes. That means: In the plane of the driver we get a quarter wavelength resonance between the closed and open ends of the enclosure. For a 12 inch long pipe this would excite a 286 Hz resonance nominally. Since the effective length of a quarter wave pipe is always longer than the nominal length the resonance will be more like 250 Hz or even 200 Hz. On his website http://www.linkwitzlab.com/faq.htm#Q28 Linkwitz has explained this in depth - mostly for H frames - and shown, that even for different drivers in the same W baffle this resonance frequency can be wildly different.
At the resonance frequency we get a SPL peak of up to 10 dB followed by more dips and peaks as we get up in frequency. So we should stay well below that peak or even put a notch filter on that first resonance peak. As a rule of thumb one would try to stay one octave below that peak which would confine a 12 inch pipe to an upper limit of ~120 Hz.
Hopefully this explains why we don´t want the front and back pipes longer than the diameter of the driver demands. To make things complete: Orthogonally to the quarter wave resonance we get a half wave resonance between the upper and lower walls of the pipe. If we make our pipe a square one, that resonance frequency would be about twice the (nominal) quarter wavelength resonance. So no sweat there. But if we are going to stack those W or N baffles – don´t remove the horizontal division. It would halve the vertical resonance frequency and bring it well into the same magnitude as the horizontal one.
A short roundup: It´s counterproductive to make a ripole baffle any larger than the driver demands. Small is beautiful.
That´s it for the moment. I´ll cover the width issue of those quarter wave pipes later. Stay tuned. :D
Rudolf |
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| bibster |
For what I've understood from the various threads and sites is that
* The SURFACE of the 'front-chamber-outlet' should equal 25% to 30% of the driver's Sd. Let's call this the chamber's HEIGHT. This height should be smaller to achieve a lower Fs (right?)
* The baffle's WIDTH/LENGTH should be the driver's size + twice the wood's thickness + some margin, but as small as possible. (I used 30Cm for a 10" and 18mm MDF) (This if you build it like on the lautsrecherbau website, with the 'lids' covering the front/rear chamber )
* Either: The rear chamber's volume should equal the front chamber's. I'M NOT 100% SHURE ABOUT THIS
* OR: The rear chamber should be as small as possible. That's why the BMC's ripole enclosure has the magnet sticking out. I tried this, sealing my not-so-perfect-hole with caulking.
Driver-wise I haven't got a clue, except: Low Fs and Qts around 0.7. I can't afford to by drivers all the time, especially the 100$+ ones. There's another 100$ P&P to hav'em shipped by PartsExpress to France.... Pity...
I just just el-cheapo stuff, and I'm impressed with my double-single ripole. Very impressed. Verrrrrrry verrry imprrrressssssed... ;)
I used 10" sh-tty driver, 4.5 cm Front chamber Height, magnet through the back (about 7 cm back chamber thus) on the 1st, and
same driver, 4.3 cm Front, 8.9 cm back, magnet inside the backchamber on the 2nd.
Haven't compared them yet, not even by ear, 'cos I need them both (rather large living room, you see)
Just my 2 cents, Paul
PS: Keep this thread alive! |
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| Rudolf |
Well, I am not shure I should follow Paul´s nomenclature from the post above. I would still prefer to call the horizontal dimension of the ripole pipe opening it´s width. Otherwise he is mostly on topic. But maybe I can tell it even more precisely. :rolleyes:
When we look at the most prominent difference between a common Linkwitz style W frame and a ripole it optically boils down to less width. But that´s not for style, but with reason. One design target for the ripole was to achieve an almost flat frequency response with only marginal electronic bass EQ. This was done by kind of mass loading the driver and raising the system Q that way. In a wide pipe the air volume would move freely and SPL would drop early. In a narrow pipe the air is more resistive against cone movement. Thus the cone can couple its energy more efficiently to the air mass. Narrowing the pipe has it´s limit when efficiency drops radically and the moving air becomes noisy. Comparable to a BR tube becoming too small.
The rule of thumb here is: If the drivers Xmax (peak-to-peak) is >10 mm, the opening area of the pipe should be not less than 1/3 Sd. If Xmax is less, the area might be reduced down to 1/4 Sd.
The pipe opening at the rear of the driver should be between 1/2 Sd and 1 Sd. The performance of the ripole is predominantly determined by the front pipe. There is no real need to get both volumes equal. But if you add the cone volume to the front pipe volume and subtract the same cone volume from the rear pipe volume you will get comparable volumes in many cases anyway.
A second design target for the ripole was the lowering of Fs. This can easily amount to 10 Hz reduction. A bigger VAS will result in a bigger reduction of Fs. So it is no use to look for rock bottom Fs under ~25 Hz in a driver.
This is definitely everything I can tell you about the ripole dimensions. Tomorrow I will try to add some comments regarding driver parameters and the – too much neglected – passive equalising cum notch filter.
Rudolf |
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| Nuuk |
Moray asked me to mention a couple of drivers in connection with this subject of this thread.
The Max Pentivents are very well made, have a vented pole piece and from what I have heard testing a couple of 12 inchers in a W baffle, they work well for dipole bass.
Here are some specs.
I know of one member here who uses the PV1550!
I believe that the Pentivents are available on both sides of the Atlantic.
And Hemp acoustics are working on a 15 inch dipole woofer that will have an Xmax of 14 mm. :att'n: |
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| bibster |
Rudolf,
You seem, no, you ARE absolute way more informed/experienced on the subject, so I'll follow your nomenclature :o
(I called it HEIGHT becouse in many of the pictures I've seen the cabinets seem to be 'laying down', the driver's horizontal, get it?)
I didn't know the Sd/front-mouth relationship was related to the Xmax, nor the Sd/rear-mouth width relationship, thanks!
I'll try to make some spreadsheet tomorrow to figure some values based on our common knowledge. As a matter of fact I've allready made one, just to calculate the wood dimensions (Bored at 'work' you see... :D )
So, for this S-sheet's enhaced version we need: Sd, driver's outside diameter, driver's height (To get rid of the hole in the back, if possible. That's a pita to achive...), Xmax, wood thickness, right?
Is there, or rather, do we yet know how to predict the Fs lowering, based on Vas, chamber size and some other parameters?
Regards, Tschüß, doeg, a+, Paul |
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| v-bro |
I sometimes pity the fact that manufacturers are not at all clear on mechanical capabilities of their speakers, let alone noises produced by air displacement or cone breakup(flapping?wow, seems bad to me!).
Information on this shouldn't be limited to experience or guessing(knowing the materials and build).
Isn't there a way to produce free air specs based on showing all behavior other than desired?
Or don't they try becouse they're afraid of the results?
Or is it impossible to distinguish them that way becouse some flapping speaker can behave exellent in some enclosure design?
For a ripole I think a free air mechanical power capability graph(frequency related to max. electrical power connected in a sine-wave pattern keeping all within reasonable margins of distortion for example) might be helpfull. |
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| bibster |
Well,
Here's my Q'n'D ripole calc sheet, mainly for cabinet construction though...
It's a preliminary V0.0001 alpha release :D
Send comments/improvements etc. to my email rather than here, I don't want to mess up this usefull thread!
regards, (Ri)Paul |
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| Rudolf |
Since this thread is about drivers and parameters, I should contribute some too. :)
In general Axel Ridtahler and some other competent ripole guys recommend a target system Q of ~0.7 to 0.9. This will be best achieved with driver Qts 0.5-0.7. But any Qts from 0.35 to 1 may be taken into consideration too.
Fs should be between 25 and 45 Hz. Remember that Fs reductions of 10-15 Hz for the ripole system are quite common!
VAS is indicative for the stiffness of the suspension. A PA driver with stiff accordion surround and resulting lower VAS would get less Fs reduction than a driver with a “loose” rubber surround.
Mms should be within reason. So better no 10 inch driver with a 120 g cone! Even 12 inch drivers should need no more mms than 80-120 g to give good results. 15 inch drivers should be content with mms < 160 gr.
So for instance mms-wise the Peerless SLS series would be suited much better than the XLS drivers.
Drivers that have been explicitly “approved” by those ripole guys or have been applied with good results are:
- Peerless SLS series
- Vifa 30 WN 380 RL/8 Fs=21 Hz, Qts=0.21, Mms=61 g, VAS=328 l, Sd=507 cm²
(This driver reportedly had been produced to Ridtahler´s specifications and doesn´t really comply with the “rules” above. So you don´t have to stick to those rules too much too)
- GBS 515 Fs=24 Hz, Qts=0.47, Mms=160 g, VAS=257 l, Sd=835 cm²
(This discontinued driver was offered at the German ebay and is clearly the bigger brother of the RBS 512. Don´t confuse it with the new GBS 515 or GBS 5115, which are offered by the same vendor). TSPs are taken from an independent source: http://www.hifi-selbstbau.de/text.php?id=119&s=read
- RBS 512 Fs=29 Hz, Qts=0.42, Mms=196 g, VAS=61 l, Sd=531 cm²
(This driver has been approved by Ridtahler himself - notwithstanding the high mms)
- A&D 1530 Fs=46 Hz, Qts=0.48, Mms=xx, VAS=142 l, Sd= ~900 cm²
http://www.traumboxen.de/ad-audio/r1530.htm
- A&D 1830 Fs=34 Hz, Qts=0.64, Mms=xx, VAS=265 l, Sd=~1400 cm²
http://www.traumboxen.de/ad-audio/r1830.htm
- Visaton W 300 Fs=32 Hz, Qts=0.55, Mms=43 g, VAS=190 l, Sd=490 cm²
I know most of these drivers are only sold in Europe, but they should just show what to look for.
Rudolf |
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| nilsomat |
Hello everybody,
very nice thread, and long overdue i would say.
I can second that the Peerless SLS-12 is indeed a great driver for that design, and it performs beautifully in my ripole.
I will post some more information soon.
Greetings,
Nils |
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| moray james |
Hope this attached data sheet on the 30 WN 380 RL/8opens. If not here is a copy of the data on this driver. Regards Moray James.
Characteristics:
30-cm-Tieftonlautsprecher with very hard, conical paper diaphragm.
50-mm-Schwingspule, 4 lagig. Large stroke reserve (large mechanical stroke).
Ventilated magnetic system.
Ideal low clay/tone driver. Been suitable for bass reflex housings or closed volumes
(e.g. as Subwoofer, actively entzerrt).
Chassis data:
External dimensions: 308 mm Schw. - reel Ø: 40 mm
Installation dimension: 297 mm Schw. - reeling height 14 mm
Depth: 128.6 mm Schw. - spulen-Träger
Front. Material: Air gap height mm
Basket material: Air gap filling:
Diaphragm type: Magnet Ø: mm
Diaphragm Sicke: conical Magnet height: mm
Diaphragm material: Paper Magnet weight g
Dustcap material: Magnet Ind. T
Thiele Small parameter:
Resonance fms: 21 Cycles per second Indulgence Cms mm/N
mechanical. Quality Qms: 2.3 moved mass Mms: 53 g
electrical quality Qes: 0.25 mechanical. Absorption Rms: kg/s ¹
Total quality Qts: 0.23 Diaphragm stroke Xmax: mm
A-volume Vas: 400 Litre Force factor Bl: 12.7 N/A
DC resistance RH: Ohm Diaphragm Ø MD:
Inductance Le: mH Diaphragm surface Sd: 513 cm ²
Electrical absorption Res: Ohm Max. separation frequency. fmax: 1 kHz
Efficiency Nref: % Nominal sound pressure SPL: 93 railways
Product folder (English): Pdf Download (33 KB) |
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| soundcheck |
Hi folks.
I finished my ripoles using 4* BD15 drivers of Bert Doppenberg some time ago.
These are 16R drivers with an efficiency of 97db each!
This a much higher efficiency than you're discussing here!
I am more than happy with them.
Read this:
http://www.bd-design.nl/forum/forum_entry.php?id=11047
\Klaus |
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| qi |
| quote: | Originally posted by MJK
I don't think that any of the current worksheets will do the job. But it should not be too difficult to configure a worksheet that would do all of these and a few more, basically a driver loaded front and back with quarter wave pipes. Just a matter of finding the time and determining if there is enough interest to justify spending that time. Definitely interesting enclosure designs. |
Hi Martin
I am sending you my money today.
Nothing speaks more loudly than MOOLA.
I am hoping others following this thread shall follow suit... |
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| Calvin |
Hi,
Rudolfs comments are correct so far so good. So I´ll add just a few words.
I can´t confirm his findings regarding drivers with stiff suspensions. My findings have been that especially those PA-drivers with stiff suspensions show high values of Fs-reduction even when the open area of the chambers is quite large compared to the Sd. Mostly the reduction lies within the range ~5Hz-10Hz, but with those stiff PA-drivers sometimes nearly 20Hz is possible! Too theses drivers normally show a better performance for infrasonics. The highest excursions happen on the fs and sinking values show below fs. Drivers with soft supensions show greater excursions values below fs.
In practise You can torture drivers with strongly progressive and/or stiff supensions much harder than drivers with sloppy suspensions.
The Vifa should best be forgotten. The reason why this driver was used was not because of its parameters, but because of a kind of OT-reason :apathic: Its usability for Ripoles is rather low and Axel and his partners were never really happy about it.
Peerless drivers have been intensively used in ripoles, from the older poly-types to the new SLS-series which have close to reference-parameter-sets. Those can be recommended wholeheartedly. Any other driver should be checked on its noise-performance. Many drivers with good sets of parameters lack in the noise departement. So unless tested no recommendation should be believed in!
jauu
Calvin
ps: @soundcheck: You´re claimed 97dB efficiency is worth nothing since it´s just applicable outside the working range of the driver :rolleyes: Just displacement volume counts for SPL here! |
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| soundcheck |
@ calvin
97db SPL is according to spec of course!
2 in parallel giving me a real 91db SPL at 8R ! To me it's worth a lot I'd say.
I don't need a power plant to get my drivers moving.
I havn't heard a more airy realistic bass yet.
And I heard the originals!
I just wanted to mention that there are alternative drivers
out there.
BR |
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| MJK |
I looked at the referenced German site with the U, H, A, W and the two Ripole enclosures. I believe that all of these can be modeled using my MathCad worksheets with some degree of accuracy. I already have older models of the U, H, and A frame dipoles that just need to be updated to the latest calculation scheme. Adding the W and Ripole enclosures will not be that difficult. The models would include the enclosures sitting on the floor with a movable rear wall boundary condition similar to my exisiting models.
I just uploaded new versions of my existing worksheets tonight that I have been updating for the past few weeks. These represent small updates and corrections to the previous versions. I am at a point of starting to work on my next topic, I was going to go back to working on horns but if there is enough interest I will spend the next month or two working on various additional "dipole" worksheets. I can see a set of worksheets that calculate the response of the driver/enclosure for a constant input voltage and then the user would need to decide on any boosting circuits to extend the low end response.
Is this what people want and is there enough support? |
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| qi |
| quote: | | a driver loaded front and back with quarter wave pipes. |
Hi Martin
This is what I am hoping to accomplish with your worksheets... |
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| Rudolf |
| quote: | Originally posted by MJK
Is this what people want and is there enough support? |
Hi Martin,
as you can see from the posters nationalities, ripoles seem to be an international affair. So basicly there is demand for H, W and N enclosure simulation worksheets in Europe too. But Mathcad still is a huge barrier here. And AJ-Horn is a potent contender. So I believe those dipole simulations would be a welcome extension of your portfolio, but will not rise the number of your supporters in Europe (at least on the continent) significantly.
Just to make shure it gets your attention: Those dipole simulations should include the low pass filter to attenuate the quarter wave resonance. It´s always good to know how much that resonance can be subdued without a notch filter. But I believe you already have taken care for that. :)
Rudolf |
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| moray james |
| I would be interested in a program to fix the numbers up right. Regards Moray James. |
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| soundcheck |
Hi folks.
Just another hint. If anybody is interested
I am running a DCX2496 digital crossover to control my Dipole Subs.
Gives you phantastic options to manipulate the frequency repsonse and the dipole integration if needed.
Slopes of 48db/oct can be configured.
Paramteric equalizers are at hand with flexible Q configurations.
Phase and timing can be even automatically adjusted by the crossover itself on per inch/cm basis.
Not to forget the level adjustment.
I crossing my dipoles over at 100Hz just the right frequency to avoid getting in trouble with the unlinear dipole response.
With a 48db slope I finally got rid of the very negative subwoofer response in the mids. The poor quality of any woofer compared to your mid-woofer or fullrange driver will alwas badly impact your lower mids. These days are over!
There is no way to get the Dipoles easier integrated in your setup and to your room.
Highly recommended.
\Klaus |
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| Rudolf |
Soundcheck,
guess what? I got my brand new DCX2496 delivered yesterday. :D
It will allow for much more flexibility than the CX 2310 active X-over that did the job until now.
Rudolf |
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| MJK |
| quote: | | So I believe those dipole simulations would be a welcome extension of your portfolio, but will not rise the number of your supporters in Europe (at least on the continent) significantly. |
Actually, what has surprised the me most is the number of Europeans that have subscribed to the worksheets. By far the largest percentage of users. The US users have been a small minority. Most of my correspondence comes from Europe also.
MathCad does scare off a lot of first time users. However, once people get past that initial turn-off they really learn to use MathCad very quickly and become productive. I have had very few people give up because of MathCad once they get started. |
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| soundcheck |
@Rudolf
I got my DCX for almost a year now. And I use it for the stereo sub-woofers only . From timing perspective it was great to have everything including the upper range connected to it. Soundwise it was much of a step back.
That's why I took the upper range off the DCX.
OFF TOPIC:
By the way. Nice Homepage. Lot of interesting stuff over there.
You forgot to mention the Bastanis Dipole speakers on your page. I am running a Bastanis Kingtone. One of the few very dynamic high sensivity Dipoles.
I'll give it try with the wings on the baffle as you mention on your homepage. Sounds interesting.
By the way, which city are you from? You can drop me mail! If you like;-)
@MJK
Let see if I can do some backward engineering on my dipole-woofers.
Would be nice to see if the quarter-wave calculation works
also for a double-ripole such as mine.
As i understood I'd have to subscribe for a year though to get the sheet. Is this correct ;-) |
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| MJK |
| quote: | Let see if I can do some backward engineering on my dipole-woofers.
Would be nice to see if the quarter-wave calculation works
also for a double-ripole such as mine. |
I am always looking for test cases to analyze. If you send me your geometry (sketch or drawing) and driver parameters I will make it the default set-up for a worksheet. If you have measured data it is always good to see how it correlates with the calculations. Obviously the calculations are always the correct answer. ;)
| quote: | As i understood I'd have to subscribe for a year though to get the sheet. Is this correct ;-)
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That is correct, a one year subsription is required. |
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| moray james |
long and hard it seems that the SLS series of drivers that Calvin has recommended is still about the very best suited to Ripoles. Visaton also have a similar series of excellent drivers as well. For folks who do not have to keep a small budger the Volt series of Radial 15 and 18 drivers are impressive.
I have had some simulations run that showed that there are a few Eminence drivers that are cost effective and may work as long as they can be confirmed to be suitable with respects to low frquency noise generation. Since I do not have any of these driver I cannot comment on this but perhaps there are some here who own these units and can check them and comment. First an least (but still good bang for the buck) is the Beta 15 A this shows pretty goo results and is inexpensive and will move a lot of air. Second is the Delta 15 LFA which is only a little more money than the Beta and sims quite well and coud be a strong performer if it it does not make much noise at LF. Third is the Killomax Pro 18 A is a monster and should be capable of most impressive performance again the caveat is to check it for LF noise. The Volt series of Radial drivers is impressive and will work well in Ripoles but the price is also impressive. Regards moray James.
Peerless SLS data can be found here http://www.tymphany.com/
Visaton data here http://www.visaton.de/en/index.html
Volt Radial series data here
http://www.voltloudspeakers.co.uk/A...s/about_us.html |
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| moray james |
It would seem that not only are the T/S patameters important for Ripole/dipole drivers but also the drivers response curve will tell you a big part of the storey. With Ripole/Dipole cabinet you must depend upon the drivers ability to make bass as you do not have the benefit of a low tuned reflex vent to augment bass output. So the driver does what it does and you get what you get. I think that the response curve of the driver will tell you more than the T/S perametes will. If you are going to choose between two drivers where the T/S numbers are about the same choose the one that has the best low frequency response curve. If you look at the curves of most bass drivers they will show a significant roll off between 100 and 20 Hz. typically as much as 20 db or more. Many sub woofers drop like a rock starting as high as 100 - 200 Hz. The best drivers show only a 10 - 15 db drop in response between 100 and 20 Hz. These are the drivers that you want to consider for use in a Ripole/Dipole system as you will have the most amount of output where you want (need) it with the least amount of EQ.
I have noticed that the drivers with really big strong motors with BL above about 15 tend to be over damped and do not typically have the best LF curves. Just something to keep in mind. Auto sound drivers in the 8" to 10 " size may well be worth looking into at 12" and larger the pro drivers seem to have the largest selection but price starts to go up. Regards Moray James. |
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| moray james |
| since driver noise is a greater concern in all dipole designs than it is in box designs I am wondering at what point (in terms of excurssion) one needs to move from non vented spider design to a driver with a vented spider? Any thoughts or comments? This would seem to impact driver considerations especially with smaller diameter drivers (8 - 10 inch) where longer excursions are required. Regards Moray James. |
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| Rudolf |
| quote: | Originally posted by moray james
It would seem that not only are the T/S parameters important for Ripole/dipole drivers but also the drivers response curve will tell you a big part of the story. |
Moray,
if TSP are good for anything then it´s for EXACTLY predicting the bass response of a driver. If you see different diagrams for drivers with the same TSPs, then it exclusively stems from different measuring conditions (different baffle size, anechoic/not anechoic, microphone distance etc.) or from manipulated TSP (that happens too!).
The only excuse would be a driver with a cone so floppy that it breaks up below ~200 Hz, since T/S assume the cone to be a flat rigid piston. I don´t dare to suppose that such a bad driver would ever find it´s way into your home. :D
Rudolf |
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| maudio |
| quote: | Originally posted by moray james
since driver noise is a greater concern in all dipole designs than it is in box designs I am wondering at what point (in terms of excurssion) one needs to move from non vented spider design to a driver with a vented spider? |
I would definitely say that you must use open spider for all bass applications.
Excursion is much larger in open baffle and efficiency is much lower, add these two and you're there... My first dipole experiments with cheap and too small budget woofers actually produced so much other noises that the bass output was completely swamped by it :bigeyes:
In my search for the perfect driver I once was allowed to perform the 'noise-test' on a whole range of 10 and 12" drivers in a local loudspeaker shop (the owner was very interested as well). I don't remember exactly, but I tested drivers from most popular manufacturers on the (European) DIY market, Visaton, Vifa, Monacor, Peerless, Seas, Scanspeak, some budget stuff, ..... These tests clearly revealed that only very few drivers are suited for open baffle use at all and that a vented spider is a must for real quiet operation, even at excursions of only a few mm
I also looked at cheap car woofers but found that in general they are of very poor quality. The better ones often cost more than a decent unit for home-use.
Drivers with very strong motors (Q<0.5) can be used with no problem and will allow you to set the final Q of your system according to your preferences. But this will require additional EQ in the filter. Using active EQ (which is mandatory anyway IMHO) that's no big deal.
BTW the ultimate dipole driver is probably the Cabasse 55 ND, a 22" and 40 mm stroke unit. Don't know if it's still available. Not a cheap one either :clown: |
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| Rudolf |
Two heretical comments concerning venting:
1. It´s all or nothing.
My Visaton W250 (http://www.visaton.de/en/chassis_zu...ton/w250_8.html) in H-frames have no venting whatsoever. Air is completely trapped behind the spider. While this does not help to improve Qm, it definitely keeps the driver from generating air noise. First unwanted noise you hear in the dipole application is the stamped steel basket vibrating.
So IMHO you should keep the driver as airtight as possible or as amply vented as possible.
2. Do your own tracheotomy.
I have never done it myself, but it sounds worthwhile and the soldering iron will be your friend: By burning some holes into the spider (be careful to do that symmetrically) you get the back of the spider vented. And by cutting a hole into the dustcap you get the pole vented to the front of the speaker. Obviously all holes have to be wide enough to cope with the air flow. And obviously the TSP will change (slightly) by manipulating the respiration tract.
Anyone cares to do the reality check here??:rolleyes: |
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| Rudolf |
I had promised to close my general ripole rant with some notes regarding passive EQ. Doing this I will mostly rehash what I have learned from Axel´s and Calvin´s postings on other forums. And Calvin certainly will correct me where and when I get off the point. ;)
The main reason for equalisation certainly is the first quarter wave resonance peak at the upper end of the ripole transmission range. This can be well done with a standard serial LCR notch filter in parallel with the driver. The values of this notch filter only depend on the required frequency and notch Q.
http://www.diyaudio.com/forums/atta...tamp=1107611565
To work properly this notch filter needs to see a resistive load (L1 in the diagram). This could be anything between 0.47-0.68 Ohm. Obviously this resistor must be a heavy duty one, since it is in line with the driver. A very clever solution is to join this resistance with a load impedance which will work as a low pass filter from ~100 Hz. So a coil of 6.8 mH / R=0.5-0.7 would be perfect for a driver impedance of 4 Ohm (or two 8 Ohm drivers in parallel). For a single 8 Ohm driver the load impedance should be halved to ~2-5 mH.
This low pass filter helps to subdue the resonance peaks and dips of the quarter wave pipe as well as possible noise from the subwoofer amp. Because the resistance of L1 becomes part of the system Qes, the system Qts will rise too – resulting in a slightly extended bass range.
Implementations of this passive ripole filter have been published at http://www.lautsprechershop.de/hifi/ripol_bau_en.htm and http://www.diyaudio.com/forums/show...8430#post568430
Attention:
Since the position of the first quarter wave resonance peak is a function of driver AND ripole frame, its exact value can only be determined by measurement. Being off 10 % can render the notch filter useless. So interpolating notch filter values from different published ripole dimensions or drivers is trial and error – well, mostly error.
Rudolf |
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| moray james |
Rudolf: I have a number of odd 12 & 15 inch car driver kicking around for so long now I think that if one died for a test it would not be a hardship. I will have to look for my test disk with sine wave tones and then I can take my iron to a spider to see how much reduction in noise there is pre and post operation. I can also test to see what happens with dust cap venting.
I think that most of the noise you hear with sealed spiders is from air making its way through the spider as most spiders are porus. One might consider sealing the spider to make it air tight but this would to some degree affect stiffness (but not too much I think) as well as the Mms (I think). Have I got this right venting spider and dust cap reduces Mms and sealing the spider and dust cap (making them air tight) will increase Mms? Thanks Moray James. |
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| Rudolf |
| quote: | Originally posted by moray james
Have I got this right venting spider and dust cap reduces Mms and sealing the spider and dust cap (making them air tight) will increase Mms? |
Hello Moray,
if I remember correctly you alter Cms with those alterations. But since Cms is part of the equation for Mms, it should effectively turn out as a change in Mms too. I will check that out tomorrow in the morning (in my part of the globe) ;)
Rudolf |
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| moray james |
I was thinking mostly about the impact of air mass loading with the spider vents decreasing the air load somewhat. You are right as suspension stiffness will also be impacted as the two are hand in hand together. So if the air load is reduced some then the suspension stiffness will behave as if it were a little stiffer when presented with the lighter load.
Venting or removing the dust cap will reduce/eliminate the compression of air that would normally occur beneath the dust cap and also impact both Cms and Mms with the bigger affect on Cms (I am guessing here) which would most likely result in a reduction of Fs.
Removal of the dust cap will probably have as great an impact upon driver noise (reduction of compression inside the voice coil system) as would some vents under the spider. Just a guess but the volumes involved (under the dust cap and under the spider) are probably close in volume). Holes in the vioce coil former above the spider have been used as heat pumps which also help to equalize the pressure on both sides of the voice coil in the motor structure. I have not seen heat pump holes in large high power pro bass drivers and I must assume that perhaps this is because they would compromise the former integrity under very hard drive conditions. It is well known that even solid heavy formers can buckle under severe stress due to the impact of the shock wave generated by the voice coil/motor. This is of course an extreem example but it does happen. I have often wondered why designers do not simply do away with the former all together as it limits heat disapation toward the pole piece (acts as a thermal insulator). There are companies (18 Sound) that wind voice coils on both the outside and the inside of the former to address this very issue but I wonder why the do not just wind a flat ribbon voice coil instead and do away wit the former alltogether. Note that the issue of multiple windings with this design suggestion could be dealt with by winding a flat bifilar ribbon coil. In this way the voice coil is able to thermally sink to both the top plate and the pole piece without any thermal insulation from a former. Just some ramblings regards Moray James. |
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| Paul Ebert |
Very interesting thread. I really appreciate the information.
How about the Dayton Reference series subwoofers?
RSS315 12" subwoofer
RSS390 15" subwoofer
Neither driver really needs a Fs reduction, but other than that they seem suitable and not too expensive.
Thoughts?
Thanks.
Paul Ebert |
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| maudio |
This MAW 12 driver seems good value for money, parameters are just about right. Too bad it doesn't seem to have an open spider, as far as I can see from the pictures. Well it's cheap enough to risk some hole drilling...
Btw how do you want to compensate for the 6db/oct slope using only passive filtering? You need a truly massive coil for that.
| quote: | | I will have to look for my test disk with sine wave tones |
maybe this will be quicker: http://www.marchandelec.com/fg.html :D |
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| moray james |
This letter was posted elsewhere and I thought that the comments would be of use and interest here. Regards Moray James.
Driver considerations are the same as for a normal open baffle. Therefore high surface area (think of 12, 15 or 18 inch) low fs, highish qts (>0.4), and preferably high xmax with a lot of power or high efficiency + reasonable xmax (8 mm).
The only addition a ripole yields is that the baffle is more or less folded and the chamber behind and in front of the woofer generates a lower fs of the complete system.
When some parameters are off spec (say a low qts of a typical PA woofer) you need more eq in the filter. In my case (Visaton BGS 40) I wasted the efficiency of two times 98 dB/w/m resulting in a inroom efficiency of about 93.
In addition I've to say that the room dictates the lower threshold of the FR response as shown in one of the papers on the website of JohnK.
By the way, I forgot to mention the ripole resonance, this needs atleast a parallel LCR circuit in combination with a >3rd order electrical filter. The resonance is typically in the 200-300 Hz range so a lot of uF and mH are in order (typically >10 mH and >300 uF). The design can only be finalized when you atleast can measure the impedance (resonance is easily recognizable in the impedance curve) but IMHO to be able to design a proper loudspeaker you also need to measure the FR.
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| moray james |
| Paul: both the Dayton drivers that you mention will probably work very well in a dipole design. You will want to watch out if you run dual units as in a W or ripole configuration as the load to your amp is going to get low. You might want to opt for an H baffle or a U baffle with a single 15 inch unit to maximise your output and still maintain a healthy load for your amplifire(s). Regards Moray James. |
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| moray james |
Here are some Beyma drivers that would be suitable for dipole use. The number at the end of each driver (in brackets) is the driver's EBP which is the ratio of Fs devided by Qts which tells you the kind of enclosure the driver is intended for. An EBP close to 100 suggests a vented enclosure and a EBP close to 50 indicates a driver intended for a closed box. Dipoles would seem to prefer drivers with a EBP closer to 50 but there are numerous sucsessful designs with driver EBP close or over 100 so there is room to play. Most high efficiency pro driver are designed for reflex venting so you will see higher EBP's with them for the most part. You can find high excurssion car drivers with EBP's below the 50 range. Regards Moray James.
SM118/N (67)
21L50 – 73
18LX60 – 71
15LX60 – 97
12LX60 – 135
10LW30/N – 158
12BR70 (79.5)
10BR60 (72.5) |
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| Paul Ebert |
Moray,
I plan to put two of them in series, resulting in a nominal 8 Ohm load. I will not get any efficiency benefit that way, but that's OK.
Paul |
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| johninCR |
I finally got around to testing the best cheap candidate that I could find locally in a 6"x9". They ended up being more than I hoped at $22/pr, but the performance exceeded my expectations primarily because it takes getting them up past 14mm of point to point excursion before they start behaving badly (sonic operation, etc.). That means that I can count on a solid 5mm of Xmax, and 4 drivers approximates the Sd of a 15". Yes, the Fs is high in the 50's, but that's where the ripole limited airway approach helps, although I may need to mass load the cones to get down below 40hz. Push/pull operation is a given due to the cheap construction.
The real beauty of 6x9's is how closely I can pack their Sd together. I plan to use 8 per side. It looks like I'll be able to fit 8 (equal to a pair of 15's) in a W cab that is 10" wide (maybe less), 10.5" deep, and 27" tall. Of course I'll add 4-5" of depth since it's a 2 for 1 value (4 for 1 compared to flat baffle width), and to achieve some U effects on dispersion.
For those not looking for high max output and/or low end extension, just think how compact 4 drivers could be. You could still do push/pull, and if you alternate the front pathways on the left and right sides, you can cancel most of the mechanics too using the typical Ripole alignment and have only a 7" width.
Another good alignment would be 6 drivers in a W (although you'd have to work at it to get reasonable symmetry). Then you stack them with the 9" driver dimension vertical, resulting in only 6" deep manifolds (higher extension possible). Then a 10"W by 12"D by 29"H would have the bass potential an 18" woofer on a 36" diameter baffle in free space, plus it would be a great compact stand for a main driver on a small baffle on top. I may have to rethink my plans as I'm not sure the extra 3db of potential is worth the extra pair of drivers and larger cab, not to mention less top end extension. |
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| moray james |
You probably want to consider segmenting the drivers into vertical sets of two side by side drivers per baffle section (vertical or horizontal) to keep the baffle dimensions from getting too far out of square. You don't want to have different resonant points for depth Vs width set up in your 1/4 wave resonant lines. That's why round drivers with square baffles just big enough to fit the drivers are used and why not making the lines any deeper is advised.
I think this will be a very interesting project. The drivers are very compact, inexpensive and with multiple sets you can build up a large Sd. Your power handling should be excellent as should efficiency. As you said you can use a tallish sub cabinet as the base for a dipole mid/top unit.
You do want to try to keep your options open so here is a link for a 12 inch driver ($47.28 CND) with good perameters for a dipole sub which is very inexpensive and has lots of xmax. Cutting lots multiple holes in a baffle for 6x9 units has to be considered. Regards Moray James.
http://www.mach5audio.com/product_i...ea425a028ed2259 |
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| johninCR |
Moray,
1/4 wave resonances come into play with depth. Other parallel dimensions can result in standing wave type resonances, which are 1/2 wavelength. I do plan a triangle divider between each vertical driver pair and to splay the drivers baffles at a slight angle resulting in each each cavity being only 6" deep by 9" tall with no parallel surfaces. The backside will have damping, which is required for U alignments. Plus I'll err on the side of larger pathways in the rear, and use stuffing to balance the airmass load and achieve the tuning I want at no sonic detriment. Believe me when I say that I take into consideration far more variables than the commerial ripoles used as an example.
Be careful not to follow dipole purists too closely, especially when it comes to bass. A good example is dipole use as subs. How many of them warn about dipole bass being room limited in extension? Have you built a Linkwitz W-baffle woofer? I didn't even use high excursion woofers and panel vibrations are a real problem. Fire a high excursion driver into an even narrower cavity, and it becomes a problem which must be considered. I think an awful lot of people have been lulled to sleep by what OB's do better than boxes. As a result, a lot of the basic construction requirements of boxed speakers are overlooked with almost all OB's, but for the most part the needs still exist.
BTW, as I've been typing this I had just 1 pair of the 6x9's in a shallow U baffle that I rigged as bottom end fill for a set of horns playing reggae and some other bass heavy music in the background. I've definitely decided to go with the 6 woofers per side compact alignment. That should be plenty for most listening, and I have 2 pairs of higher excursion pro type 15's to use in a high performance OB speaker pair that I have planned (100db at 30hz outside).
I have a digital camera now, and will start a big construction effort of a number of final form cabs along with test cabs, so expect lots of pics very soon, plus measurements shortly after. |
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| moray james |
JohninCR: sorry my braain has frozen on this one. Are you building dual ripole style or U frame? If you can do a sketch or send a pic when you build it will help a lot.
The 6x9 driver was where I started with this thing thinking about saving a lot of money if the right driver could be found. Had thought about looking for a bunch of discounted units as the car bus is all about whats new and the volume huge. Still thinkthat it is a good idea but there is more work to be done with all the cut outs mounting and wiring.
6x9 units (or cheap 8's) could be built into a dual ripole structure which could be vertically extended into a floor to ceiling tower. The foot print of which would be very small yet house a lot of driver surface area. Easy to intigrate a pair of these into a room as they occupie such a small area but pack a wack of Sd. The determining factor would be the driver cost. Given the huge potential for Sd in this type of design hi xmax would not be an issue so lots of drivers to choose from. You could expect about the same piston area of about 4.5 15 inch units per collum. Not bad and lots of power handling. Something to think about. Regards Moray James. |
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| johninCR |
W-baffle with a U extension added in back. I will use the ripole approach to lower Fs and reduce size. That's why I posted to this thread. Yes multiple holes are a pain, and wiring less so, but for performance requires multiple drivers even if you use larger ones. The reduced size and much shallower cavities are a tremendous advantage.
Also, with OB bass, the primary concern is Xmax. Sd and Xmax are the 2 specs of critical importance as long as you stay away from the typical high Le big subwoofer drivers (another item of little concern using smaller drivers).
After hearing how good just a pair sounds, a column of 8 per side has a ton of potential, and I'm considering that too due to my narrow room.
Here's a top view of the baffle, not to scale and I may have to go with less splay to get the ripole effect, but I need to try a test manifold first. The blue panels are the driver mounting baffles.
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| Kensai |
John,
I like that concept. The little bit of splay will make the driver faces visible. Done up in a nice, contrasting baffle material, it should be attractive. If built stacked, will create quite a decent line. Another advantage would be that you could actually build the enclosure, well braced. and then mount the drivers (a standard ripole requires that the drivers be "built into" the enclosure as there is no clearance in the design for slipping the magnet structures/baskets into the cutouts, let alone getting a tool in there to screw them down).
Anyway, a simple yet elegant design which is spawning ideas. Thanks. Oh, and I'm so happy you have a digicam now. Can't wait to see pics of your construction.
Kensai |
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| johninCR |
Kensai,
With push pull I'll have ugly baskets and magnets to hide, so I'll paint everything possible inside the manifold a flat black and put a grill on the front painted gloss black to hide everything nicely. Since I'm using cheap drivers, and I want to go as compact as possible, the drivers will probably have to be mounted at least before the side panels go on. The pair of 6x9's I have go surprisingly low, so I don't need the maximum ripole effect of lowering Fs. I don't listen to pipe organ music or trance type stuff, so solid output into the low 30's is fine for me, since HT gets a proper sub.
The end result will be something similar to those below, but with less odd angles to torture myself (that pair has no screws or fasteners and were a real pain to glue with pressure for a good joint). I'll go with only enough cavity on top to hide the magnet of whatever main driver I use.
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| Kensai |
Those things still fascinate me with the completely asymmetrical top. Almost like an art object instead of a speaker cabinet.
Kensai |
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| johninCR |
| quote: | Originally posted by Kensai
Those things still fascinate me with the completely asymmetrical top. Almost like an art object instead of a speaker cabinet.
Kensai |
Thanks, I'm going to rip those manifolds out and put four 6x9's in instead. They sound great as is, but only capable of moderate volumes, so I don't use them much. Also, I wish I could have retained the light color of the front pictured. Clear varnish darkened them way too much as you can tell from the rear pic. I'm quite pleased with proportions of the cab, though. It took some tinkering during construction because nothing had a firm plan, just a mental pic of what I wanted. The wing angles and top cap were critical to achieve what I felt was well proportioned, and the only "looks over sonics" compromise was the diffraction effects of the top cap overlapping the front baffle.
When I upgrade the bass section, I'll probably have to add more air flow resistance on the back side to equally load both sides of the woofer cones. 2.5 years ago when I built them, I was getting some ripole behavior without understanding it because those little 6's play much deeper in the manifold alignment, even though they aren't very restricted in the pathway. |
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| Paul Ebert |
John,
What are the coax's in this speaker? How do they sound?
Thanks.
Paul |
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| johninCR |
| quote: | Originally posted by Paul Ebert
John,
What are the coax's in this speaker? How do they sound?
Thanks.
Paul |
They began life as Adire HE8.1 kits based on the Eminence Beta8CX in the recommended BR. They were a little sterile for my tastes, but once I freed them of the confines of a box the sound came to life. They're low Q and definitely need bass augmentation, but I'll never forget the day I finished them and did a head-to-head with one in the box and one in my Flintstone OB. My 9yro daughter came and danced around while music played, and she asked "Daddy, why does one speaker sound so much better than the other?". Of course without the benefit of the stereo illusion, it's always a no contest comparing one OB to one box. |
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| moray james |
That there are a couple of great posts by djk in the following thread on the last page which pertain to OB and dipole design.
http://www.diyaudio.com/forums/show...239#post1018239
DJK is an experienced designer when it comes to speakers and his comments are well worth reading and of use here. The first and foremost driver consideration he says is "driver noise" after that the T/S numbers will depend upon your actual application.
Thanks to djk and lets hope there are further installments here. Regards Moray James. |
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| johninCR |
I'd have to agree with that silent operation is a must. The 6x9's I tested really surprized me that they were totally silent with low frequency tones.
I didn't recall DJK talking about OB's, but he did mention some good stuff regarding push/pull and use of manifolds. |
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| moray james |
What are the associated trade offs when choosing the Qts of a subwoofer? If you choose a hi Qts driver the bass response will hump and there will be less need (or little) to EQ the system bass response. If you choose a lower Qts driver then the re will be more roll off and a need to EQ the system response.
Since hi Qts drivers have large powerful motors and lo Qts drivers have smaller motors then would it be fair to assume that a hi Qts driver would yield stronger more controlled (less distortion) bass response? I am under the impression that lo Qts drivers will maximum efficiency, minimum box size, and lowest cut-off point, if so does the reverse hold true for hi Qts drivers?
Regards Moray James. |
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| planet10 |
| quote: | Originally posted by moray james
Since hi Qts drivers have large powerful motors and lo Qts drivers have smaller motors |
Typically the other way around
dave |
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| moray james |
| I thought I typed it the other way around, my fingers bad sorry. Never the less. You can off set some EQ with a high Q driver but can you really? Have not found a free lunch yet so what are the trade offs? |
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| johninCR |
The trade off is a bigger box, but wait there is no box, so it's kind of free. Qts is the measure of a driver's ability to control it's cone at resonance. Big drivers with high Q can start to flop around in the lower frequencies, especially with amps that have a low dampening factor. That's why you see the big motors on high excursion sub drivers, along with smaller box requirements of lower Q.
That's one of the reasons you have to start with your performance goal using OB bass. With Linkwitz's SPLmax spreadsheet you can figure out exactly what you need to get to your goal. Then it's a matter of driver selection, but mid/high Q drivers with high excursion are rare, and EQ or lots of drivers end up required for high performance, because in the bottom octave it's only about how much air you can move. |
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| moray james |
that the determining factor would be that of not exceeding xmax at your desired low frequency cut off. Somehow that seems too simple. A stronger better damped motor system must produce bass with less distortion. I feel like I am missing something important here. I think that in a dipole the trade offs will be different than if you wanted a reflex box. The dipole would be closer to the kind of driver specs that you would be looking for in a sealed box driver. Does anybody specify driver EBP for dipoles? I know that the standard rule for vented boxes is an EBP close to 100 and close to 50 for sealed cabinets (EBP = Fs/Qts).
If we look at accepted quality drivers in W framed dipoles like the Peerless SLS 10 we see an EBP of 65, the SLS 12 has an EBP of 59, the xls 12 a EBP of 90 and the xxls 12 an EBP of 47. So the acceptable range would seem to be 45- 90.
Obviously if you don't want to do any EQ then higher Qts drivers would be the way to go but if EQ is going to be employed then lower Qts drivers would be more desireable and also probably offer a wider selection of possible candidates.
Comments would be most welcome. Perhaps Rudolf or Calvin could address this. Thanks Moray James. |
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| moray james |
| not having a good day EBP should have been posted as Fs / Qes NOT Qts. Sorry about that The numbers still come in pretty close as those I calculated (close ball park) but I was in error. Regards Moray James. time for bed. |
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| johninCR |
Moray,
Overdamping is not a requirement. Think about a driver like the B200 fullranger. Qts of .7 Fs in the 40's, but it plays great up past 10khz.
To me, if you want a perfect OB woofer for sub use, then look for a Qes of .7, Qms of 10, an Fs of 10hz, an Xmax of 20+mm, and an Xmech of 40mm, in small sizes with square or rectangular frames and cones that fill the frames for efficient stacking of your Sd in any configuration. |
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| moray james |
I was talking to Rudolf about the positive sims on the Kilomax Pro 18 A driver by Eminence. He knows of two diffeerent builders who have used this driver one with zero baffle. Both have had no problems with back side driver noise. So I think that we can place the Kilomax on the positive list of big bad dipole drivers. Simulations show Kilomax (pair) output limit of 107.9 db @ 20 Hz., 115 @30 Hz. and 120db @ 40 Hz.
The Eminence Delta 15 LFA also looked excellent on simulations but still no confirmation of low noise yet. These drivers would be well worth a try in either a Ripole or "W" frame dipole if anybody has a pair. A pair are capable of high levels of bass output at 20 Hz. (98.4 db), 106.5db@ 30 Hz. and 111.5 db@ 40 Hz.. This is very respectable for such an inexpensive driver in such a small package. |
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| miksin |
Hi,
To me it looks like this guy
http://www.rcf.it/VediMacro.phtml/IDMacro/1627/L15P530/
could be a possible candidate for ripole experiments:
with the following TPS:
Resonance frequency, Fs 45 Hz
DC resistance Re 5.1 Ohm
Mechanical factor Qms 7.5
Electrical factor Qes 0.51
Total factor Qts 0.48
BL factor BL 15.3 T - m
Effective Moving Mass Mms 83 gr
Equivalent Cas air load Vas 160 liters
Effective piston area Sd 0.085 m2
Max. linear excursion (mathematical) Xmax 6.5 mm
Voice - coil inductance @ 1kHz Le1k 1.45 mH
Half-space efficiency Eff 2.76 %
driver, with
What's your opinion, all more experienced builders? |
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| Paul Ebert |
I'm not a more experienced builder, but I'd be a bit concerned about the 'sealed spider' causing noise.
Nice, efficient driver, though. |
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| miksin |
Closed spider might be a problem, yes.
OTOH I somehow got an impression that those problems were mostly connected only to cheapest drivers.
You wont know unless you try....
Wouldn't anyway consider tracheostomy wiht my pair of them :D
( Yes, I have a pair of them in my current active OB, so I am thinkin mostly N-frame ) |
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| moray james |
| as mentioned previously a driver with a sealed spider does not necessarilly it will have a lot of spider noise. The Eminence Kilomax Pro 18A is an example. I would imagine that xmax would certainly come into play with respect to this. That said I think that a hands on physical test is what is required to determine if driver noise will be a design issue. |
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