| zobsky |
Based on a recent thread of mine ( http://www.diyaudio.com/forums/show...25&pagenumber=1 ), I plan to use 4 Pyle Pro PPA15 woofers ( http://www.partsexpress.com/pe/psho...FTOKEN=26346424 )to build a pair of double (W profile) ripoles .
Background Theory on Ripoles:
http://www.lautsprechershop.de/hifi/ripol_en.htm
Driver Blurb:| code: |
Pyle PPA15
* Power handling: 250 watts RMS/800 watts max * Voice coil diameter: 2-1/2" * Impedance: 8 ohms * Frequency response: 27-4,000 Hz * Magnet weight: 70 oz. * Fs: 26.7 Hz * SPL: 90.2 dB 1W/1m * Vas: 11.36 cu. ft. * Qms: 2.69 * Qes: .89 * Qts: .67 * Xmax: 6 mm * Dimensions: Overall Diameter: 15.06", Cutout Diameter: 13.86", Mounting Depth: 6.02"
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JohnInCR suggested that I extend the rear of the ripole to form a U-baffle extenstion. I plan to do that later via a sliding sleeve.
Excuse me while go puy some plywood :) |
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| zobsky |
No, Ripole , .. apparently similar to a dipole except with more restricted front and rear cavities to load the driver better, decreasing Fs, at the expense of some efficiency.
My criteria for sizing the openings are
1. rear cavity cross sectional area approx = 1/3 x driver Sd
2. front common cavity cross sectional area = 2 x rear cavity cross sectional area.
Here are some of my calculations (rounded off where necessary)
All dimensions in inches
magnet diameter 7
driver cutout diameter 13.86
magnet clearance above frame 1.5
nominal mounting depth 5.5
Sd (estimate) 124
internal width 15 (approx)
rear slot height 2.755555556 , .. approx 3"
front slot height 2 x 3 = 6
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| Calvin |
Hi,
If You post the data in MKS-values I could do a precise simulation for You.
Anyway on first glance I´d rather use a smaller front opening and larger back chambers.
The TS-parameters look ok so far, apart from Fs and Qts.
Fs is quite low for such a dipole. Expect the Fb to be ~10Hz lower!
Qts is a bit high for a 15" driver. Experience showed that a Qts above 0.5 is ok with smaller drivers, but with drivers >12" Qts-values around 0.4 and even smaller simply sound more precise, tighter and cleaner.
If the driver is usable will show when it is built in and working, but from the datasheet it is ok so far.
jauu
Calvin |
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| chops |
| quote: | Originally posted by Calvin
1) Anyway on first glance I´d rather use a smaller front opening and larger back chambers.
2) The TS-parameters look ok so far, apart from Fs and Qts.
3) Fs is quite low for such a dipole. Expect the Fb to be ~10Hz lower!
4) Qts is a bit high for a 15" driver.
5) Experience showed that a Qts above 0.5 is ok with smaller drivers, but with drivers >12" Qts-values around 0.4 and even smaller simply sound more precise, tighter and cleaner.
6) If the driver is usable will show when it is built in and working, but from the datasheet it is ok so far.
jauu
Calvin |
1) The front and rear chambers I believe are supposed to match the surface area of the driver used for proper loading for Ripole use.
2) Actually, the PPA15's T/S parameters are near perfect for dipole/ripole use.
3) You WANT the Fs to be low or you will need loads of EQ and power and Xmax to compensate for the low end.
4) Again, for dipole/ripole use, the PPA15's Qts is just about perfect.
5) For a driver operating in a sealed or ported enclosure, this is true. However, for dipole use, these drivers are the most precise, tightest and cleanest I have ever heard. IOW, the PPA15's motor/suspension system has plenty of control over the cone's movement in OB designs.
6) The PPA15 is VERY usable, no doubt about it. Datasheets are worthless and inaccurate when trying to determind the sound of a loudspeaker or subwoofer. |
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| zobsky |
| quote: | Originally posted by Calvin
Hi,
If You post the data in MKS-values I could do a precise simulation for You.
Anyway on first glance I´d rather use a smaller front opening and larger back chambers.
The TS-parameters look ok so far, apart from Fs and Qts.
Fs is quite low for such a dipole. Expect the Fb to be ~10Hz lower!
Qts is a bit high for a 15" driver. Experience showed that a Qts above 0.5 is ok with smaller drivers, but with drivers >12" Qts-values around 0.4 and even smaller simply sound more precise, tighter and cleaner.
If the driver is usable will show when it is built in and working, but from the datasheet it is ok so far.
jauu
Calvin |
Whsat data do you want in MKS system, .. the TS parameters or my ripole dimensions, so far? I'm thinking the TS parameters. Here they are:
| code: |
Pyle PPA15
* Power handling: 250 watts RMS/800 watts max
* Voice coil diameter: 63.5mm
* Impedance: 8 ohms
* Frequency response: 27-4,000 Hz
* Magnet weight: 70 oz.
* Fs: 26.7 Hz
* SPL: 90.2 dB 1W/1m
* Vas: 0.321679377 cu meters
* Qms: 2.69
* Qes: .89
* Qts: .67
* Xmax: 6 mm
* Sd (approximate value for a 15" woofer with pleated surround) : 0.0856 m2
* Dimensions:
Overall Diameter: 0.382524 meters
Cutout Diameter: 0.352044 meters
Mounting Depth: 0.152908 meters
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I've adjusted my dimensions slightly, since the plywood in the store is 48" wide, . not 49" like I had expected it to be. I'l have be rebate away a little wood to allow the driver to fit |
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| zobsky |
This is what I'll have to do to make sure the driver frame fits . Ths top part won't be glued in, but will be held in place by threaded rod .
Calvin, I'll wait on your simulations and build the baffles in the mean time. I thought I followed the rule of thumb correctly ie.
1. opening cross sectional area (rear) = 1/3 x Sd
2. double the front cross sectional area to account for the fact that I'm using 2 drivers per ripole (facing each other).
What am I not accounting for? |
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| zobsky |
| quote: | Originally posted by chops
5) For a driver operating in a sealed or ported enclosure, this is true. However, for dipole use, these drivers are the most precise, tightest and cleanest I have ever heard. IOW, the PPA15's motor/suspension system has plenty of control over the cone's movement in OB designs.
6) The PPA15 is VERY usable, no doubt about it. Datasheets are worthless and inaccurate when trying to determind the sound of a loudspeaker or subwoofer. |
Chops, I think what Calvin means is that the ripole construction loads the driver more than a conventional open baffle design and accordingly, the motor has to be able to cope.
We'll find out soon enough. For starters, I'm not going to glue in any of the "spacers" that determine rear or front chamber height, so if the ripole doesn't work out, I'll just make spacers taller to morph the ripole into a conventional w-profile dipole design.
Calvin, if you need, here are the current dimensions in mm
Here's |
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| chops |
| quote: | Originally posted by zobsky
Chops, I think what Calvin means is that the ripole construction loads the driver more than a conventional open baffle design and accordingly, the motor has to be able to cope.
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Agreed, but still nowhere near as much as coping with the forces within a traditional sealed or vented enclosure.
I have one of these PPA15 drivers in a sealed 4.2cf enclosure for center channel duties, and it does a pretty decent job, considering... ;) |
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| zobsky |
| Nothing exciting yet, .. merely cut the panels to size and routed out the magnet pass-through holes. If you can keep the dimensions of the panels to just a little under 16", you should be able to build a pair of cabinets out of one 4 x 8 " sheet of plywood. |
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| y8s |
I dont want to hijack the thread, but is there any hard data on Ripole construction and calculations? I see numbers like "25% of Sd" and "lowers Fs by 15%" but is there any math that predicts this?
A few have quoted the MJK design worksheets as well as the dipole calculations, but only casually.
Other than experimentally, is there any way to "design for Ripole"?
Thanks!
Matt |
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| Rudolf |
| quote: | Originally posted by y8s
... is there any hard data on Ripole construction and calculations? I see numbers like "25% of Sd" and "lowers Fs by 15%" but is there any math that predicts this? |
AFAIK: A model for the Ripole configuration has been developed with
Akabak. This model is not published. So for a accurate calculation of a ripole you need someone with access to that model. The numbers you have mentioned have been published as ballpark numbers by people with access to that model. |
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| Calvin |
Hi,
don´t write ´perfect parameters for Ripole´ when Calvin says: "OK but not perfect" :D :D :D
If You´d plan a Linkwitz-type dipole or OB I´d agree with Chops, even if I´d still prefer a somewhat lower Qt (remember that a Qtb between 0.5 and 0.7 is recommended as best ). With Ripoles its a slightly different matter.
The original Ripole lowers the Fs typically between 10Hz and 15Hz.
Just building a dipole compartment doesn´t mean building a Ripole!
A Ripole always comes with a passive EQ, that lowers the Fb further!
So 27Hz together with very small chambers will probabely result in a subsonic Fb (~12-15Hz) which is not useful at all.
It´s the script Rudolph talks of that is in usage by A.Ridtahler and someone else ;) and the sim-results and actual measurements are quite consistent.
@Zobsky:
I need the dimensions of Your suggested dipole compartement.
jauu
Calvin |
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| zobsky |
| quote: | Originally posted by Calvin
Hi,
don´t write ´perfect parameters for Ripole´ when Calvin says: "OK but not perfect" :D :D :D
If You´d plan a Linkwitz-type dipole or OB I´d agree with Chops, even if I´d still prefer a somewhat lower Qt (remember that a Qtb between 0.5 and 0.7 is recommended as best ). With Ripoles its a slightly different matter.
The original Ripole lowers the Fs typically between 10Hz and 15Hz.
Just building a dipole compartment doesn´t mean building a Ripole!
A Ripole always comes with a passive EQ, that lowers the Fb further!
So 27Hz together with very small chambers will probabely result in a subsonic Fb (~12-15Hz) which is not useful at all.
It´s the script Rudolph talks of that is in usage by A.Ridtahler and someone else ;) and the sim-results and actual measurements are quite consistent.
@Zobsky:
I need the dimensions of Your suggested dipole compartement.
jauu
Calvin |
After cutting the square wood pieces down, trimming them to size etc
The realistic central compartment interior dimensions = 368 mm (W) x 387 mm (L)x 152 mm (H)
The 2 rear compartments dimensions = 368 mm (W) x 387 mm (L))x 76 mm (H)
I haven't cut the pieces of wood that make up the height of the individual compartments (the H pieces) so let me know what you think are optimal sizes (and why). For my initial estimates, I used Srear = 1/3 x Sd and Sfront = 2 x Srear (dual ripole)
From your post, I think that excessive driver loading will be unnecessary for these drivers since their Fs is low to begin with.
Thanks |
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| zobsky |
| Driver cutouts done |
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| Taterworks |
Essentially, all anyone with Akabak would need to do is model an acoustic compliance on either side of the driver, followed by an acoustic resistance (defined by the size of the slot).
Any word on how a Ripole would work with only the rear or the front of the driver resistively loaded? |
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| chops |
| quote: | Originally posted by Calvin
Hi,
don´t write ´perfect parameters for Ripole´ when Calvin says: "OK but not perfect" :D :D :D
If You´d plan a Linkwitz-type dipole or OB I´d agree with Chops, even if I´d still prefer a somewhat lower Qt (remember that a Qtb between 0.5 and 0.7 is recommended as best ). With Ripoles its a slightly different matter.
The original Ripole lowers the Fs typically between 10Hz and 15Hz.
Just building a dipole compartment doesn´t mean building a Ripole!
A Ripole always comes with a passive EQ, that lowers the Fb further!
So 27Hz together with very small chambers will probabely result in a subsonic Fb (~12-15Hz) which is not useful at all.
It´s the script Rudolph talks of that is in usage by A.Ridtahler and someone else ;) and the sim-results and actual measurements are quite consistent.
@Zobsky:
I need the dimensions of Your suggested dipole compartement.
jauu
Calvin |
Well I have to admit, since for some reason I find it very difficult to find any information on the Ripole concept and design on the net, I don't know a whole lot about them. Such as ripoles lowering the Fs... I know that they do, but I didn't know by how much.
You stated that ripoles can lower the Fs by as much as 10-15Hz. If that's the case (and I'm quite surprised that it's that much), then yeah, I'd say the PPA15's Fs might be too low. How would that differ from a driver with say a 40Hz Fs? That would get you down to 25-30Hz, but how would the overall bass output sound and perform compared to the PPA15's 12-17Hz Fs?
I've always thought that the lower the Fs is, the better, and that the driver would perform better throughout the bass range until it reached below its Fs in any style enclosure. Is this not the case?
I'm guessing that if I were looking to build a really good ripole with good bass extension, I would look for a driver with an Fs of about 35Hz, so that would get me down to 20-25Hz mounted to the ripole?
Also, how different are the Qts requirements for ripoles compared to dipoles? Does the Qts also shift in one direction when used in a ripole that we should be aware of?
And are there any good sites that really get into the guts of ripole designs and concepts?
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| zobsky |
In any case, I rigged together one last night with the side pieces pressure fit via threaded rod . I'll try and get some impedance measurements later tonight so we can see what's going on.
Subjectively, this thing is INEFFICIENT Agreed, all I have for now is a 100 W power amp (Mcintosh 2100)driving it fed off the LFE of my reciever, but I've had to max it out and at that point, it's subjectively just about able to keep up with the efficient arrays. The pure dipole seemed to work with the gain turned up around half as high. I haven't rigged up the 2nd ripole yet, .. those drivers are in the MDF board for now.
The bass is subjectively clean (though I think) the pure dipole bass has better attack . The ripole doesn't pressurize the room and is subjectively even ie. no annoying peaks, it's clean. Good for music. Individual notes on the bass / synth are well defined. Cone motion is evident but seems somewhat less than the flat dipole. SPL measurements seem fairly flat down to Fs taken at the mouth, ... but drop off in the 30s when taken at listening position. .
Big disappointment for home theater effects. Explosions are wimpy sounding. I was expecting a bit more in the "sock you in the chest" department. I'm guessing that this isn't what ripoles are designed for, though. It could also be that the motor isn't strong enough for a ripole, as suggested earlier in this thread.
Dimensions are similar to my sketchup models posted earlier in this thread. Maybe I should change those dimensions. Any suggestions?
The neat thing about the way things are set up right now is that I can easily change this to a linkwitz type W-baffle or a ripole of different dimenstions by cutting up new spacers (side pieces). I'm wondering if I should decrease the ripole loading. |
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| Calvin |
Hi,
@Zobsky
based on Your data the simu for 2 drivers (electricaly paralleled) says:
fb(wo.filter): 16.9Hz
Fb(w. filter): 16Hz
so we have indeed ~10Hz lower resonance than freeair!
upper resonance: 270Hz (~+15dB) ||| with filter: none
f-3dB with filter: 180Hz
Zmin: 2.7ohms @100Hz
Zmax: 11.7ohms on fb
suggested filter:
Lser: 3.9mH 0.4 plus minus 0.1ohms
Lpar: 1mH, 0.25ohms
Cpar: 320µF
excursions:
@20Hz, 7V, 5mm
@30Hz, 17V, 5mm
@40Hz, 32V, 5mm
@Chops
Your assumptions are quite right.
A large 15" or 18" driver with a Fs around 30-35Hz could reach down to ~20Hz in a small ripole.
From my experience it always showed that such drivers (You find a few of them with good parameters) can be found at professional manufacturers (PA). These drivers show regularly a better behaviour when asked to handle large amounts of power than those with a lower fs (because of a softer suspension), especially when the supsension is made stiffer (for higher Fs) and with progression.
The Qt rises a bit in ripole, but not much.
jauu
Calvin |
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| zobsky |
Hi Calvin,
Thanks for the info. I'll try and generate an ARTA impedance sweep later tonight.
Do you have any recommendations for front and rear volume values that I could try?
Thanks again |
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| chops |
Yes, thanks Calvin for the info!
Now all I need are some good links to sites about ripoles that get into the details of the concept and design. ;) |
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| Calvin |
Hi,
maybe I´ll provide a different set of dimensions later.
@Chops
I don´t know of any particular site for ripoles.
jauu
Calvin |
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| mashaffer |
This is great and I will be watching with interest. I had hoped we would see more action on the Ripole subject as I have a salvaged Wurlitzer organ speaker that I would like to use as part of my keyboard amplification system.
Unfortunately due to the Fs of 45Hz, Low Qts of about .3 and very large Vas (about 12cu ft if I remember right) any conventional cabinet I have come up with is rather large for portable use. It models very well in a TL but would be huge.
I am hoping that the lowering of Fs would get me into the 30s and that the loading will up the q a bit so that it doesn't roll off so quickly. I will be pairing it with either a 12" organ speaker and Piezo horn or possibly a 10" dual cone organ speaker.
mike |
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| zobsky |
I made some comparisons to different rigged up dipole alignments (woofers on flat board vs woofers facing each other in 90 degree W dipole vs woofers facing each other in ripole).
Firstly, I think Calvin was right when he said that the PPA15 Qts is too high for ripole. I get the sense that the woofer motor doesn't have what it takes to drive the ripole.
Comparing the ripole to the woofers on a flat board, the ripole does go deeper but is somewhat less efficient (in the test, the ripole was unfortunately a bit closer to the mic so the SPLs appear almost even, .. sorry about that). The woofers on a flat board had more mid bass punch, which is something I referred to in my earlier posts. See my UNCALIBRATED SPL curves for reference.
Rigging up a crude W-baffle, this gave me the best results, ... solid bass punch + extension. I decided to persist with the 90 degree "V" with both woofers firing forward for reasons of symmetry and to have both drivers fire at the listener. At the same time, I don't have the real estate to devote to a full U-baffle, hence the compromise.
I have one or two other drivers that I think will work in a ripole, .. my trusty adire shiva 12 and a big dog university C-15W woofer. A project for another time. The pyles however seem to perform best in more conventional baffles.
Construction in progress. :xfingers: Excuse the mess.
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| Rudolf |
@zobsky some questions:
Did you measure all three configurations at the same position in the room? What was the mic distance?
Did you compare the cone excursion at the same SPL level between the "ripole" and the other configurations? The "ripole" may have been less efficient due to mass loading, but should do the same SPL level with less cone movement. Since dipoles are almost always limited by xmax first and not by power, the "ripole" may have been the winner at max SPL without power considerations.
Rudolf |
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| bzfcocon |
Have you tried an Y-Dipole ? It's kind of an U-frame with inwards-shaped, narrower back cavity. I owe 2 of these with high Qt drivers (Eminence Alpha 15 A) and I am quite satisfied. IMHO, there are a few advantages over other topologies:
- lower extension and SPL, the driver "sees" a larger equivalent baffle
- "good" mass loading - one can search for a compromise in the back wings length w.r.t. quarter wave resonance, mass loading and SPL.
- lower space requirements (one has a front baffle with inward wings)
While there are reasons for not using inward "wings" in a fullrage OB, I see no problem with that for low frequency (mine are crossed over at 160Hz LR4). For music, I don't feel the need of more SPL or extension and the bass is powerful, clean and tight(yes, midbass also).
For HT...I wouldn't know, but one probably needs more. |
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| zobsky |
Hi Rudolph, ...
First of all, please understand that this set of measurements are just to confirm what I was hearing, .. and not the absolute truth in themselves. That said, ..
Q. Did you measure all three configurations at the same position in the room? What was the mic distance?
Mic distance was around 2 m with mic located at listening position . As I mentioned before, the ripole was a bit closer (around 0.5 m) than the other designs. The locations were a bit different (see my photos - the ripole somewhat closer to the side wall), .. as I don't have a lot of space in the room at this point. For all these expts, .. the horn sub in the background was made irrelevant by blocking off its mouth with the floor.
Q. Did you compare the cone excursion at the same SPL level between the "ripole" and the other configurations? The "ripole" may have been less efficient due to mass loading, but should do the same SPL level with less cone movement. Since dipoles are almost always limited by xmax first and not by power, the "ripole" may have been the winner at max SPL without power considerations.
Yes,.. comparatively, the ripole had less cone excursion, I would agree with you that it would probably have a higher power handling / max SPL. However, I still prefer the bass from the W baffle subjectively WITH THIS DRIVER .
From my little experience, I feel fairly confident that a more powerful amplifier AND / OR a driver with a stronger magnet will yield better results with ripoles.
Thanks |
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| ashok |
What are the cabinet dimensions ( of the Y shaped dipole ) ?
Front baffle width ( square I guess ), rear opening width , perpendicular depth from the front to back ? Are the top and bottom panels parallel or also sloped like the sides ?
Thanks. |
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| bzfcocon |
Assuming that the question was adressed to me:
- Front baffle : 46x46 cm (one could make it actually smaller)
- total depth : 32 cm
- rear opening width: 25 cm (I think I would make this a bit wider though , about 30cm. Anyway, not critical)
- rear opening depth (straight portion): 11 cm
Top and bottom are parrallel and so are the rear opening lateral walls (which continue the sloped wings). If enough woodworking skills and tools are present, one could make curved wings that slope inwards and the continue straight.
Interestigly, my units sound best with no stuffing whatsoever. I tried some stuffing to help damp the quarter wave resonance, but this took a lot of the extension and "life-like" away, so I gave up and removed the resonance electronically with a notch filter(at about 260 Hz, which is out of band, but was still audible).
The problem is that stuffing should behave resistive, which is kinda hard: one could use materials like steel wool. With acoustic resistor, the respunse would be closer to a cardioid. |
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| ashok |
Sorry bzfcocon ,
That question was addressed to you.
Thanks for your reply. I've been making up plans to build my dipole sub but wasn't able to decide which one would best suit my needs . Your preferences seem to coincide with mine and you feel the Y does the job.
I'll try it out as it's easy to do.
I guess you meant curved sloping sides to spread out and flatten the resonance peak. There must be some other way to kill it .
I'll try the straight sides first. Will post results when it is done.
Can you put up a picture ?
Thanks. |
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| ashok |
I'm unable to attach an image. Wonder what happened . The blurb says contact the administrator .
:confused: |
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| zobsky |
| try the ubiquitous imageshack.us if your image is too large or if you're too new to this site. |
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| ashok |
"....if you're too new to this site...."
I guess most of us don't pay attention to the details of the members .;)
ashok
Registered: Jun 2002
:D |
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| bzfcocon |
| quote: | Originally posted by ashok
I'll try it out as it's easy to do.
I guess you meant curved sloping sides to spread out and flatten the resonance peak. There must be some other way to kill it .
I'll try the straight sides first. Will post results when it is done.
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Yeah, well, I don't know if curved sides REALLY help much, it's rather an aesthetical issue. The resonance will still be present, but one can at least push it out of band (by using a reasonable depth)
Here's a picture of mine:
Looks like I cannot attach it, although is small enough. I'll try again later. |
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| theAnonymous1 |
Well, I'm kind of disappointed the ripoles didn't turn out as expected. Not only because I suggested the drivers, but also because I had high hopes as well.:(
Maybe a more traditional N baffle with larger openings would be better. I have plenty of amp power available so that it no concern.
BTW, for hosting pics...
Imageshack = :down:
Tinypic = :up: |
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| bzfcocon |
| quote: | Originally posted by bzfcocon
Yeah, well, I don't know if curved sides REALLY help much, it's rather an aesthetical issue. The resonance will still be present, but one can at least push it out of band (by using a reasonable depth)
Here's a picture of mine:
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| ashok |
Thanks bzfcocon, that's just as I imagined it to be.
Are there any equations that can calculate the response of such an enclosure ? The rear enclosure must be acting as a resistive load . Would that be acting like an acoustic transformer ?
In an extreme case it would end up being just a Helmholtz resonator I guess. |
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| bzfcocon |
Unfortunately, I could not find any theory specifically on Y Frames. There was a project in a german magazine that inspired me, but they presented the whole as if only the pure dipole theory was applicable and ignored even the quarter wave resonance, which IS there (but they stuffed the rear cavity).
I agree with you that the rear cavity should be resistive. However, I guess the introduced effect and phase shift is quite weak and the response still resembles that of a dipole. That U-Frames are stuffing sensitive and how to stuff them properly is teached here (same would apply to Y-baffles, i think):
http://www.musicanddesign.com/u_frame.html
However, as I mentioned before, I liked it better with no stuffing at all. I admit I did not try the "proper" way because I could not measure. |
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| ashok |
| Sometimes not knowing or measuring can result in 'new discoveries' !:D |
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| zobsky |
Should I make this a hybrid W-U baffle by letting the wings extend beyond the "V" and stuff the cavity or should I truncate it at or near the "V" . Any practical advice from people who've tried both alternatives?
Also, would I benefit from making the wings unequal lengths? |
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| theAnonymous1 |
Zobsky, are you reading my mind or something. :eek:
I figured if these aren't ripole compatible I would try a sideways W like the one in your pic.
BTW, thanks for doing all the hard work for me. :D :clown: |
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| zobsky |
| quote: | Originally posted by theAnonymous1
Zobsky, are you reading my mind or something. :eek:
I figured if these aren't ripole compatible I would try a sideways W like the one in your pic.
BTW, thanks for doing all the hard work for me. :D :clown: |
Now you don't have to feel bad about not completing your project before mine.
I'm waiting to see if I can get any responses before I glue the first cab up. If not, I'll clamp up something and find out myself. |
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| ashok |
Zobsky ,
By making the wings different lengths you will probably distribute the resonant frequencies. If they are equal the frequencies will coincide and make the resonance worse. However turned on its side and kept on the ground should affect it as the wall on one side ( the ground ) would be semi 'infinite' as compared to the other smaller wooden sides.
Looks like lots of experimentation is called for.
Cheers. |
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| Rudolf |
| quote: | Originally posted by zobsky
Should I make this a hybrid W-U baffle by letting the wings extend beyond the "V" and stuff the cavity or should I truncate it at or near the "V". |
The radiation pattern would become more of a cardioid - which could be good or bad. Depends on what you want to achieve. I read from quite some people that they prefer their U baffles unstuffed.
If you want to go the U-way - why do you plan a W up front anyway? Just for impulse compensation?| quote: | | Also, would I benefit from making the wings unequal lengths? |
From practical experience I don´t see any significant distribution of resonance. It will just lock on another frequency. And as ashok stated: You already have unequal length by making the floor one side of the U. |
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| theAnonymous1 |
| quote: | Originally posted by Rudolf
If you want to go the U-way - why do you plan a W up front anyway? Just for impulse compensation? |
I'm not sure about zobsky, but I was thinking of this exact configuration to minimize the height. My mids/highs will be on top and two 15" drivers on the bottom will set them too high.
Whats is "impulse compensation" and why would a W have this and not a U? |
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| Rudolf |
| quote: | Originally posted by theAnonymous1
I'm not sure about zobsky, but I was thinking of this exact configuration to minimize the height. My mids/highs will be on top and two 15" drivers on the bottom will set them too high. |
Point taken :) | quote: | | Whats is "impulse compensation" and why would a W have this and not a U? |
The cones moving forward and backward will make the frame react with a movement in the opposite direction. In the W frame the tilted cones are moving half forward/backward and half up/down. Since in the vertical plane the cones are always moving in opposite directions there is no resulting vertical force into the W frame - only the horizontal fraction. |
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| bzfcocon |
I always wondered whether and to which degree "impulse compensation" is audible.
Clearly, it cannot harm (one can als achieve "perfect" impulse compensation by mounting 2 woofers such that their cones move in exact opposite direction).
My Y-baffles are single woofers and are not very heavy (aroung 10 kg) - although rigid enough, also because of their shape. When I put my hand on them on significant low frequency content, they to "tremble" a lot(even though they sit on spikes). I am thinking of making them heavier by adding a heavy top plate. |
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| zobsky |
| quote: | Originally posted by Rudolf
Point taken :)
The cones moving forward and backward will make the frame react with a movement in the opposite direction. In the W frame the tilted cones are moving half forward/backward and half up/down. Since in the vertical plane the cones are always moving in opposite directions there is no resulting vertical force into the W frame - only the horizontal fraction. |
Thanks, .. I don't have a lot of room (floor space specifically), so some sort of compaction is necessary when working with these large drivers to avoid ending up with a wall of speakers, literally speaking !! .
Thanks for clarifying what you mean by impulse compensation. A real W (drivers facing each other would work better but I like the aesthetics of the design with drivers at 90 degrees better. ... sacrifices !!
Would both the arrangements below exhibit it - I still don't get what the advantage of magnet to cone mounting is, compared to cone to cone mounting, as the net moment of force should be similar (though not identical) in both cases?
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| bzfcocon |
It's not mainly on magnet to cone or cone to cone - although that also plays a part.
It's the direction of cone movement, which generates a force in the opposite direction. If both cones moves in the same direction (like in a 2 woofer U frame) the forces will sum up. If cones move in opposite directions(as in a ripole), the forces will cancel. Anything else will result in a force that is the vector sum of the two - like in your W baffle. |
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| zobsky |
| quote: | Originally posted by bzfcocon
It's not mainly on magnet to cone or cone to cone - although that also plays a part.
It's the direction of cone movement, which generates a force in the opposite direction. If both cones moves in the same direction (like in a 2 woofer U frame) the forces will sum up. If cones move in opposite directions(as in a ripole), the forces will cancel. Anything else will result in a force that is the vector sum of the two - like in your W baffle. |
I agree and understand that. I'm aware that my 90 degree mounting will result in a net force acting in the horizontal plane. What I want to understand is the pros / cons of symmetric cone to cone (one of my figures, ripole etc ..) vs cone to magnet (linkwitz W) mounting. |
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| bzfcocon |
I think that is a totally different issue.
The cone to magnet arrangement in Linkwitz's subwoofer should reduce even order distortion, by making one cone move out of the magnet, while the other cone moves into it. The magnetic field in the gap is not perfectly symmetrical around the cone stop position and this arrangement helps correct this to some degree. |
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| zobsky |
| quote: | Originally posted by bzfcocon
I think that is a totally different issue.
The cone to magnet arrangement in Linkwitz's subwoofer should reduce even order distortion, by making one cone move out of the magnet, while the other cone moves into it. The magnetic field in the gap is not perfectly symmetrical around the cone stop position and this arrangement helps correct this to some degree. |
Thank you, . that is what I wanted to know (".. The magnetic field in the gap is not perfectly symmetrical ..") , .. same operating principle as the so called"push pull" amplifiers. |
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| EUVL |
Calvin,
You seem to have quite some experience with the Ripol. Would you be kind enough to give us some advice ?
My friend & I built a Ripol based on the Ripol 12/2 from HobbyHiFi a couple of months ago, but with full side and bottom walls as per Linkwitz (see attached Drawing). Passive LC, & Mivoc AW3000 chasses. First impression deep base very impressive, but lacks dynamics.
Could be the amp (700W at 2 ohms) or cables, but could also be the Mivoc's .... Or are we loading the chasses too much (front opening about 106mm, 2x rear openings about 140mm each) ?
http://www.lautsprechershop.de/hifi...i/disub12_2.htm
(We wanted to be sure with the design before spending the money on a pair of Peerless'es.)
Thanks & Regards,
Patrick |
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| Calvin |
Hi Pat,
what do Youmean with ´lacks dynamics´?
Is it the maximum SPL? Then You should know that 2x 12" drivers with medium throw capability are acceptable for listening to music (no HT) in smaller rooms up to 20-25m˛.
Is it the impression of a slow and sloppy bass?
Well then.....Mr. Timmermann´s concepts seem quite often to be more promotional projects than reasonable ones. The usage of drivers which are probabely ´pushed´ by the distributor, but are not neccessarily the right drivers for the application is very obvious.
In the first case a solution is to add more dipoles, in the latter case it is very probabely a matter of the driver, maybe a bit of the cabinets dimensions and definitely not a matter of the cables or amplification.
jauu
Calvin |
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| EUVL |
Hello Calvin,
By lack of dynamics I meant slow & sloppy (not enough punch).
I also tend to think the chassis makes the difference. If I read your various posts correctly, you would also recommend Peerless SLS or XXLS, right ?
The room is about 20 sq m.
May I also pick your brains on a few questions I have in mind :
1) Any comments on the 106mm front exit and 140mm rear exit dimensions (height 330mm, depth 375mm, excluding all walls)?
2) How can I calculate the transmission line resonance frequency of the cavities in order to set the LC values of the EQ network?
Thanks in advance,
Patrick |
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| bzfcocon |
If I'm allowed to make a few comments:
1. I haven't listened a lot of dipole bass units, but from what I've listened it looks like you're better off with larger diameter, higher Q drivers than smaller, long-throw cheap woofers needing lots of equalisation. I listen to a pair of Eminence Alpha 15A woofers in Y-Frames and there's plenty of both punch and extension. However, better and more expensive woofers like the Peerless might be better, but at another price.
WRT this, there an interesting topic on Zaph's site:
http://www.zaphaudio.com/lowxmax.html
2. I would suggest to actually measure the TL resonance rather than estimate it. It's safer. Actually, in a W frame, doesn't one have two resonances corresponding to the front and rear cavities ?
Cheers
Liviu |
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| EUVL |
> If I'm allowed to make a few comments:
Of course, most welcome.
> looks like you're better off with larger diameter, higher Q drivers than smaller, long-throw cheap woofers needing lots of equalisation.
There are a few reasons I chose 12". First is how much room I want to allow for my subwoofer in a 4m x 4m sitting room. Secondly I do not need VERY loud base. So probably Peerless SLS is sufficient. XXLS is just to give it extra headroom, just like 100W class A power amps, when you use <10W 99% of the time.
And I don't have a TV, so no problem with magnets. :)
> I would suggest to actually measure the TL resonance rather than estimate it. It's safer.
That assumes that one has measuring equipment which has been well calibrated. Equipment we have, calibration we have not time to get round to yet, especially against room acoustics. Calculation gives a quick estimate and a good starting point.
> Actually, in a W frame, doesn't one have two resonances corresponding to the front and rear cavities ?
Is the frequency not only a function of the depth (length) of the cavity, and not dependent on the cross section ?
Patrick |
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| bzfcocon |
| quote: | Originally posted by EUVL
There are a few reasons I chose 12". First is how much room I want to allow for my subwoofer in a 4m x 4m sitting room. Secondly I do not need VERY loud base. So probably Peerless SLS is sufficient. XXLS is just to give it extra headroom, just like 100W class A power amps, when you use <10W 99% of the time.
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My subjective impression is that, with dipoles, one comes close to the speaker limits very quickly (especially with lots of EQ ). The limit is alway Xmax rather than power.
How big are your enclosures ? Like in the linked project ? My 15" have a footprint of 46x32cm, not to mention the Y shape which allows to "stick" them between other things in the room. Of course, you also need a reasonable distance to the back wall.
| quote: |
Is the frequency not only a function of the depth (length) of the cavity, and not dependent on the cross section ?
|
You're right, I had different lenghts in mind. Regarding resonance estimation: in my case, matching the notch filter at the exact right frequency made a significant difference !
Guestimating, one has to consider that the actually effective TL length is not exactly the length of the cavity - I've seen something on Linkwitz site, but I don't remember where. |
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| ashok |
| Bass reflex ducts are effectively slightly longer than the measured size. I think the termination , sharp edge or rounded off , also matters . Fastest and accurate method is to build one and try it out. Is this affected by the proximity of the boundary walls ? |
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| Rudolf |
Patrick,
when simulating W frames with the TML functions of AJHorn, I always found
- different resonance frequencies for front and back chamber (not surprising since the cross areas are different)
- a real life resonance peak that did NOT correspond well enough with the simulated peaks. :rolleyes:
For measuring the peak you only need to measure the impedance. No microphone necessary, just a multimeter and some sort of tone generator. So there is - almost - no excuse for not doing it yourself.
There is absoutely no need to have any calibration applied. :smash: |
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| bzfcocon |
| quote: | Originally posted by Rudolf
For measuring the peak you only need to measure the impedance. No microphone necessary, just a multimeter and some sort of tone generator. So there is - almost - no excuse for not doing it yourself.
There is absoutely no need to have any calibration applied. :smash: [/B] |
Hmm..that way you will certainly get the resonant frequency, but how do you get the acoustic Q and size from the impedance curve? Is it the same as the electrical ? I doubt it, since the speaker itself will also show some impedance variation. Please correct me if I am wrong ! |
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| Rudolf |
| quote: | Originally posted by bzfcocon
I listen to a pair of Eminence Alpha 15A woofers in Y-Frames and there's plenty of both punch and extension.
Liviu |
I am looking for a source for those Alpha 15As in Germany. Where did you buy yours?
Thanks, Rudolf |
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| bzfcocon |
You got me :D
I no longer live in Germany, but was too lazy to change my avatar. Here in Romania, there's a local Eminence dealer. Should actually be one also in Germany, have you looket at their site ? |
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| Rudolf |
| quote: | Originally posted by bzfcocon
Hmm..that way you will certainly get the resonant frequency, but how do you get the acoustic Q and size from the impedance curve? Is it the same as the electrical ? I doubt it, since the speaker itself will also show some impedance variation. Please correct me if I am wrong ! |
The resonance will not be very symmetrical, so you can´t notch it out perfectly. You could take the acoustic Q from published Ripole diagrams of comparable size and adjust the resistance of the applicable notch filter for a minimised SPL peak on resonance. This is just meant as first aid if you have no access to decent equipment. |
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| Rudolf |
| quote: | Originally posted by bzfcocon
Here in Romania, there's a local Eminence dealer. Should actually be one also in Germany, have you looket at their site ? |
Sure. They don´t list 15" Alphas at all. Even Google does not show any german source for the 15A. :( |
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| bzfcocon |
Weird...the dealer would be:
http://www.adamhall.com/de/AH_K--Em..._2__k--77__f--1
but, as you said, they don't list 15A. Maybe you can call and ask ?
There is a possible reason why Alphas are not always available. As I bought mine, the dealer looked at me and asked if I really want that speaker, as it has a small magnet and is not very powerful.
There is not much use in the pro area for them, except maybe for guitar/bass speakers. |
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| Calvin |
Hi,
@euvl. I´m quite short of time in the moment and bzf and rudolf have answered already. For more I suggest PNs
jauu
Calvin |
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| diymax62 |
Hello Rudolf,
first of all thanks a lot for your investigation about the dipole speakers, unfortunately I don't understand German language (well, I have some difficulties with english, too...:xeye: ) and I can't appreciate deeply the content of your site.
Have you ever thinked about a translation in English (google translator is really funny, but not completely useful in most cases)?
Some times ago I asked to a german dealer a quote for two Eminence Delta 15", that really inspired me for building a "rude" dipole associated with a Sica full-range.
It seems that they have the item that you need still in the catalog, try a little search here:
http://www.jh-akustik.de/shop/
I hope this will help you.
I need an help, too, but I'm afraid it's a too long story, and it's due to my confusion about the theory of the dipole (but I simply love how it sounds), and I'd don't want to bore DIY members with question probably already treated.
Can I contact you in a pm?
a great hello |
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| DAMIC |
I checked almost all topics about Ripoles on this site, and have several questions. It seems that I missed the simplest thing, I am still not sure, whether the 2 drivers in BMC(BMS) Ripole design are connected parallel in phase (as I think) or out of phase.
Few days ago, I sow an interesting article on
http:mitglied.lycos.de/MundU/audio/dipolsubwoofer.htm?
Dipole (Ripole) with Kef B139. I don’t speak German, but from the text, it seems that this vintage driver is suitable for Ripole. Btw, I have the pair of B139, the oldest model SP6171 and want to try this design.
But, on my Kef B139 version SP6171 fundamental resonance is only 20Hz. According to theory the Ripole design reduces the resonance frequency about 6-7dB or even more and I am wonder that this design could lead me to low freq. that I don’t wont.
Is there any rule for Ripoles (smallest cavities gives deepest fund.res. and opposite) as in this particular case I would like to Fs stays where it is, on 20Hz.
Thanks in advance, |
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| zobsky |
| quote: | Originally posted by DAMIC
I checked almost all topics about Ripoles on this site, and have several questions. It seems that I missed the simplest thing, I am still not sure, whether the 2 drivers in BMC(BMS) Ripole design are connected parallel in phase (as I think) or out of phase.
Few days ago, I sow an interesting article on
http:mitglied.lycos.de/MundU/audio/dipolsubwoofer.htm?
Dipole (Ripole) with Kef B139. I don’t speak German, but from the text, it seems that this vintage driver is suitable for Ripole. Btw, I have the pair of B139, the oldest model SP6171 and want to try this design.
But, on my Kef B139 version SP6171 fundamental resonance is only 20Hz. According to theory the Ripole design reduces the resonance frequency about 6-7dB or even more and I am wonder that this design could lead me to low freq. that I don’t wont.
Is there any rule for Ripoles (smallest cavities gives deepest fund.res. and opposite) as in this particular case I would like to Fs stays where it is, on 20Hz.
Thanks in advance, |
Yes,
the drivers are connected in phase if they are facing each other i.e. cone to cone.
I think the rule of thumb was to have the front chamber area opening = around 1/3 of driver area and the rear chamber area as small as possible . Maybe some of the experts can run simulations for you.
Reducing the cavity size reduces Fs at the expense of efficiency and vice versa.
I think fairly low Qts drivers are preferred for ripoles - the stronger motor is needed to drive the air mass |
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| DAMIC |
| quote: | Originally posted by zobsky
Yes,
the drivers are connected in phase if they are facing each other i.e. cone to cone..........
Reducing the cavity size reduces Fs at the expense of efficiency and vice versa........
|
Zobsky, thank you very much for reply what confirm my assumptions. As soon as this awfully bad cold weather in my country pass, I will made 4 square MDF boards, two with openings for drivers, and several spacers, different width. The connections would be the simplest with 4 threaded metal rods for easy assembling-disassembling. Starting point should be your rule of thumb with 1/3…. . So, maybe I will find the combination Fs to stay about 20Hz.
I wish if I could contact the guy from mitglied.lycos.de site concerning the dimensions for enclosure concerning B139, but it is a bit complicated due to German language. Any way, I will copy the app. dimensions from the photos.
I just found some more info about Kef B139 SP6171
Weight: 10lb, 4,5 kg flux density10500 oersted, total flux 137000 maxwells. I have not any idea how much it is in new system measurements, but judging to weight it could be sufficient.
Best regards,
:) |
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| mmaudio |
| Damic - did you build this design. I'm thinking of doing same and would be interested in your opinion. |
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| moray james |
| it was ok but ran out of gas sooner than I would have liked. With dipole bass the two key elements are Sd and Xmax. The B139 does not have much in either department so it will not take much eq. If you wanted to experiment with the B139 you could try a TAP horn. I think that someone worked out a design for a B139 based TAP at the Colaberative Tapped Horn Project see this link http://www.diyaudio.com/forums/show...&threadid=97674 |
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| DAMIC |
Hi mmaudio,
Two weeks ago, I spent few afternoons and made ripol with two Kef B139.
Actually I used the photos from link:
http://www.tech-diy.com/Dipol-Subwoofer.pdf
where are shown cross sections of the sub and copied the dimensions.
The enslosure is made by venered 20mm high density chipboard, the material I already have. All sides are glued and secured with several screws. The design looks almost the same as on the photos from a.m. link.
Now, what about sound? Well, the sound is realy very nice, as other diyers reports on various sites. I used the electronic x-over at 80Hz, 24dB/LR and fed the combination with separate amp. My main speakers are hybrids, Apogee Centaur Minor, 26inch ribbon working in dipol and 6,5 inch Audax mid-woofer in modified DBR enclosure.
All my friends are pleased with sound. On low volume, the sound is fantastic but there are problems on the medium and higher volumes. The fact is that mine B139 version SP6171 is the one made at late 60's or beganing of 70's and the power handling is very low, about 25-30 watt only. The older forum members probably remember the first B139 version with wide alloy casted frame/basket.
As said, on the low power, sub works very nice but since the volume is increased the speakers run in clipping. I beleive that the project from german link works better, as later version of Kef B139 were made upto 100watt handling power.
I dont have any special measuring equipment, but playing the test CD I visualy noticed that membrane starts to move from 10Hz.
What else, I like is the compactness of the design. Mine enclosure is about 34 liter, for two drivers. Just to say that Vas for B139 goes upto 160 liter, it meens that in this design you can go nearly 10 times down comparing to BR design what sometimes can be a great benefit.
The only negative side I see is of course, reduced eficiency of the system, between 6 to 7 dB per driver, as other reports.
The whole project was the trial one and this sub is not actually usable in my present sistem due to problem with limited power handling, but I am glad that there is realy a great potential in ripole design. Personaly, it cost me nothing as I had all components as a surplus and making it was a great fun for me. We comes again to known fact that use of cheap, high sensitivity, high Qtc PA drivers like Eminence 15 Alfa could be maybe the best way for ripole.
Regards,
p.s. I forgot to mention that integration with main speakers is superb. BTW for years, I could not manage to integrate properly my amplified Mission 73AS sub. Could be due to radiation pattern. |
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| moray james |
| you could probably get some fair change for your B139's on the used market. Why not consider two pairs of Peerless SLS12 drivers. Or for not a lot more you could use 15 or 18 inch Eminence drivers for some serious area and output down low. |
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| DAMIC |
Hi moray james
Yes, I am considering to try another project with bigger and more sensitive drivers. Perless are not on the market in my area but Eminence 15 Alphas are available in Belgrade for about 50 Euros/pc. Btw, my best man are so pleased with sound and want invest money in 2 pairs of Alphas, of course I will assist him in making of the enclosure.;)
Best regards |
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| planet10 |
| quote: | Originally posted by moray james
you could probably get some fair change for your B139's on the used market |
I got $100 for the last pair of racetrack B139 that i sold...
daVE |
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| zobsky |
| quote: | Originally posted by DAMIC
Hi moray james
Yes, I am considering to try another project with bigger and more sensitive drivers. Perless are not on the market in my area but Eminence 15 Alphas are available in Belgrade for about 50 Euros/pc. Btw, my best man are so pleased with sound and want invest money in 2 pairs of Alphas, of course I will assist him in making of the enclosure.;)
Best regards |
I thought that high Qts drivers (such as the alpha 15) were NOT ideal for ripole OBs . Be careful. |
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| DAMIC |
Hi zobsky,
You are probably right, but I consider ripole/dipole as very similar designs and have in mind Martin J.King last study:
Designing a passive two way open baffle speaker system, where on the page 15 he said that his recommendation is to use woofer drivers that are at least 6 do 10 or more dB efficient than the rest of the speaker system and Qts values to be between 1 and 1,2.
This is the reason, I think Eminence 15 Alphas could maybe good for ripole.:xeye:
Regards |
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| moray james |
| you can have a listen and see. Remember the Ripole will lower the driver resonance buy a fair amount. If things do not work with the high Qt drivers then you can be sure to obtain excellent results with the Delta or Kilomax. It will cost you your time to sell the drivers that are not wanted and what ever loss you take for them being sold as used. |
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| Calvin |
Hi,
the Alpha is just a cheap driver. I wouldn´t recommend it for the small folded Baffle dipoles. The excursion limit is rather small. If the parameters on the website are true You could expect at least ~5Hz of reduction in Fs. As MJ pointed outthere are other drivers on the website that look far more promising than the Alpha....costier though.
jauu
Calvin |
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| DAMIC |
Hi and thank you very much for warning .
A few days ago I found s/h, but in very good condition 2 pc. Electro Voice woofers, model Force 15. Basic parameters are:
Fs - 40Hz
Qts - 0,51
Vas - 297,4 liter
Xmax - 3,3 mm
Sensitivity - 100 dB :)
Power rating 150 Watts
more info on http://www.usspeaker.com/ev%20force15-1.htm
I am just wonder whether maybe this driver could be good in ripole. The guy is asking 200 euros/pair, well not cheap for s/h, but I could partly trade in some of my stuff. Sensitivity is great, but again Xmax and Fs so, so.
Any opinions will be much appreciated. Thank you in advance. |
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| zobsky |
I still wouldn't consider mid. or high Qts drivers for ripoles, speaking from experience. Maybe for other open baffles, but not for ripoles. I learnt this the hard way.
Best of luck, whatever you chose. |
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| DAMIC |
It is really sometimes funny, I checked this german site a several times and just now realized the driver, Axel Ridtahler actually recomends for ripole, or as it is said in the text:
Quote The following bass drivers are regarded by him as particularly suited. unquote
http://www.lautsprechershop.de/hifi...fi/ripol_en.htm
So, the target parameters for ripole driver should be probably close to this one
• Power handling (continuous/programme) = 100/200 W
• Resonance frequency fs = 29 Hz
• Impedance R = 4 Ohm
• SPL = 87 dB (2.83V; 1m)
• DC resistance Re = 3.5 Ohm
• Electro-magnetic force factor BL = 16 N/A
• Voice coil inductance L = 2.5 mH
• Effective piston radiating area Sd = 531 cm2
• Effective mechanical mass incl. air load 196 g
• Equivalent volume of compliance Vas = 61 l
• Q due to overall loss Qts = 0.42 (Qms=6.63, Qes=0.45)
• Linear excursion xlin = +/- 6 mm
• Cut-out diameter d = 287 mm
• Overall diameter d = 311 mm |
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| Calvin |
Hi,
the conclusion is wrong.
If You´d know the circumstances of how the linked project came to life You´d know better ;) The chromed pole plate and low height of the driver were two of the major points in the decision process :clown:
Anyway....there is not such a thing as a universally perfect set of parameters. For example I prefer a rather highish Qt for smaller drivers, and a lower value for bigger drivers. If You use a bigger casing like the Linkwitz type lower Fs and Qm can be helpful. With the ripol-type a elevated Fs and higher value of Qm is preferable.
I´ve got different experiences than Zobsky and have probably seen and heard nearly every dipole Axel has built, among those were examples featuring drivers with Qts>1. High Qt-drivers can work excellent in ripoles. If they don´t, I assume that something else didn´t match.
The listed values of the 12" driver are so far ok and the ripol works well with them.
jauu
Calvin |
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| illnastyimpreza |
| looks awesome ! |
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| Bluto |
Zobsky -
Just happened to open right at your last post.
In a jist, why not? I could use being saved from another useless experiment. Too much coloration?
Space constraints had me thinking about this with higher QTS drivers.
Plannin a move so thinking to eliminate IB and other thoughts have me considering simple single driver scoop horn.
Thanks - Bluto |
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| Empee |
Hi all !
you guys seem to know a lot about Ripole's
What cabinet dimentions do you advise for cheap 8" drivers like this:
Revc=7.9 Ohm
Fo=47.634Hz
Sd=15.416msqM
BL=3.851TM
Qms=4.621
Qes1.291
Qts=1.009
No=0.376%
SPLo=87.8dB
Vas=46.507mcuM
Cms=1.378mM/N
krm=170.017uOhm
Erm=1.003
Mms=8.101g
Mmd=7.000mkg
Kxm=2.701mH
Exm=0.792
Qts is a bit high, but I understand that might even help keeping it
passive (no eq needed ?)
Cheers,
Empee |
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| Rudolf |
Empee,
since the Fo of that driver is quite high for a subwoofer, you want to lower it as much as possible. This can be achieved by making the front and back channel area really small. Try a front channel area of 1/4 Sd (for each driver) or even 1/5 Sd. Back channel area as small as the basket allows.
A small area will lower the sensitivity of the subwoofer and raise the lambda/4 resonance peak of the channel. So while you may not need to EQ the 6 dB/oct dipole loss, you certainly need a notch filter for that resonance peak. It could be up to 15 dB tall!
Height and depth of the cabinet should be just large enough to acommodate the drivers. You will need a bunch of those drivers to get decent SPL. I would reckon 8+ at least. |
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| Chris8sirhC |
| How high in frequency can ripoles play up to? |
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| Bierbauch2000 |
Hi,
i think 150 to 200hz
it depends on the driver
Bernd |
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| Rudolf |
| quote: | Originally posted by Chris8sirhC
How high in frequency can ripoles play up to? |
It mainly depends on the size (depth) of the channels, which mainly depends on the size of the driver. You want to stay below the lambda/4 resonance of the channel. |
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| Dr.EM |
Ok, I built a quick and nasty Ripole with a pair of Hi-Vi D10G's (I shall name it the "Ripole-mess" due to it's low construction values :D ). No maths used, just fitted it together with whatever was convenient. Sorry, no pics as camera was elsewhere.
Got to listen for a couple of hours this morning, actually quite impressed. Not as inefficient as I expected, these 10" drivers in a W profile could create quite a lot of output! Didn't actually get them near full excursion today. Never got the filter sorted though to correct for baffle loss, so I had it up louder than it should have been in relation to the mains making higher bass ranges excessively loud.
Kick drums sound great, transient response is generally very good. Not as audible outside of the room as a typical closed/ported speaker (this is my first OB experiment). Will an OB speaker excite less room nodes too? I couldn't tell for sure as the crossover was not ideal and as mentioned I didn't have the corrective filter in place.
What do you think of using drivers like these:
http://cgi.ebay.ph/ws/eBayISAPI.dll...em=260280390035
Sorry, manufacturers page doesn't seem to be working :(
They are also available in 15". Have decent Xmax and are cheap enough to build 2 W-frame subs, or 3 if desired, have heard it is advantageous to have multiple subs to help control room nodes.
Is there any special criteria for designing Ripoles yet? Are ideal driver parameters known? |
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| Dr.EM |
Ok, I have managed to get a couple of pictures of my sub. The more I read the more I think that what I have built is in fact a W-Profile OB speaker rather than a Ripole since the chambers are relatively large. The width of the front opening is 130mm, the rear openings are around 100mm each.
These drivers are quite shallow but it would be impossible to allow the magnet system to protrude due to thier construction, so the rear chamber has been constructed to accomodate.
I can't find much information relating to W-Profile subs. Is there an optimum sizing and ratio of sizes for the openings? Presumably a W-Profile sub requires 6db compensation as other types of OB do (H and U frames etc) whereas a Ripole claims not to require so much. Listening to this sub it does sound better with compensation, otherwise higher bass ranges are too loud compared to low kick drums etc.
Any help appreciated! I like what I'm hearing but want refinement and understanding! :)
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| Rudolf |
How much did you block off any pole vent?
What is the Sd of the drivers? Could not find it in the specifications at PE.
Did you make the front opening area anywhere near Sd/2? It does not look like it in your picture. But hard to guess.
Don´t bother about the area of the back openings. I see that the basket construction would make it too complicated to make it smaller. It´s less relevant than many people think.
How did you manage the notch filter for the resonance? |
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| Dr.EM |
Hi, thanks for replying :)
Full driver specs are here:
http://www.swanspeaker.com/product/htm/view.asp?id=64
The pole vent is blocked off a bit I guess. From the "grille" it is probably only about 1cm. I doubt its an issue in terms of cooling, these drivers have big 4" voice coils and in this configuration are xmax limited way before thier 150W power handling. The vent makes noises at the highest levels (could be heard on massive attack - angel, where the large transient kick sound is very solo) but this is an artifact of the driver and it does it outside of any box too :(
Sd is 430cm^2; your suggestion is to make the front opening half of this size? Say if it were 32cm tall (roughly), it should be 6.7cm wide (as opposed to 13cm)? This would make it a Ripole rather than whatever else it is at the moment :D . Creates a fair pressure as it is.
I haven't actually got notch filtering yet, probably need to measure response to find the point? I have merely implemented a 6db lowpass at about 22hz to raise the low frequency level in respect (its all very "test" stage at the moment!). Crossover is 110hz I think, just something I had ready made, is all active :) |
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| Rudolf |
| quote: | Originally posted by Dr.EM
The pole vent is blocked off a bit I guess. From the "grille" it is probably only about 1cm. I doubt its an issue in terms of cooling, ... |
I did not think of the heat, but the air flow from the vent. Just to make shure it is not obstructed too much.
| quote: | | The vent makes noises at the highest levels (could be heard on massive attack - angel, where the large transient kick sound is very solo) but this is an artifact of the driver and it does it outside of any box too |
So NOT opening the wall for the magnet might even have been the better strategy :)
| quote: | | Sd is 430cm^2; your suggestion is to make the front opening half of this size? Say if it were 32cm tall (roughly), it should be 6.7cm wide (as opposed to 13cm)? This would make it a Ripole rather than whatever else it is at the moment |
Yes, that was, what I was thinking. But if you get sufficient bass as is, than there is no need to narrow the opening.
| quote: | | I haven't actually got notch filtering yet, probably need to measure response to find the point? I have merely implemented a 6db lowpass at about 22hz to raise the low frequency level in respect (its all very "test" stage at the moment!). Crossover is 110hz I think, just something I had ready made, is all active |
So I don´t see any reason to refine anything, except getting some measurement and looking for the appropriate EQ - and obviously - getting the optics of the enclosure right. :D
BTW: There really is no single/universal optimum size or proportion for those W frames. By narrowing the front opening you just change efficiency for lower bass . At the same time the resonance peak will rise. It´s up to you to decide where your personal optimum is. |
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| Dr.EM |
Great, that helps a lot :)
The front opening is conveniently just about the minimum size where I can still install the 2 drivers from the front, so the enclosure can all be glued (allen bolts essential!). Would probably build from either 25mm MDF or perhaps better 12mm MDF+12mm Ply laminate; could add the bars/spokes accross the openings as is popular too. Aesthetically would probably have grille material around all sides and some sort of wood finish top and bottom, although the basket is quite attractive on these drivers imo.
Really would need 3 units (6 drivers) to get enough output for a medium living room I feel. Fairly costly unfortunately but with just one I get the motor noises at high levels on music where it isn't "covered". Any ideas on how positioning 3 subs can help reduce room node problems? Is that true, I have heard it said and it makes some sense.
Other options might be to add a sub-sub woofer (:confused: ) to reduce excursion of these dipoles, just to cover below about 30hz. Perhaps a low tuned TL with a low fs driver; bandpass would be great but none work in this range that I have found. Means more amplifiers and crossovers though and 5 way is getting a bit crazy :eek: |
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| Rudolf |
| quote: | Originally posted by Dr.EM
Great, that helps a lot :) |
:D
| quote: | | Really would need 3 units (6 drivers) to get enough output for a medium living room I feel. Fairly costly unfortunately but with just one I get the motor noises at high levels on music where it isn't "covered". Any ideas on how positioning 3 subs can help reduce room node problems? Is that true, I have heard it said and it makes some sense. |
It made sense to me too when Earl Geddes explained his method with 3 subs in the "Nathan" thread. How about building another W frame and then a monopole frame with a bigger single driver for some punch down low? I have not tried it myself yet, but mixing dipole and monopole may give you the best of both worlds. I sent you a PM regarding more info. |
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