Drivers / parameters for ripole subs

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.
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.

possible driver choices

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.
Eminence Delta 15LFA...

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?

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 :)
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 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.


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 ;)

Thanks for your input

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.
the Ripole...

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.

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.
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,

thanks Martin...

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.
simulation programs for w-/n-baffle

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” . 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
Further down I will explain how horn simulation programs can be used to do dipole/ripole simulations.

Third is aj-horn , 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! , 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.

I haven´t figured out yet, if any of MJKs worksheets could do the job too. "Double bass reflex" possibly??
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.
About ripole dimensions

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 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

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!