Re: Ripoles - Honey, I shrunk the dipoles!
Hello there Rudolf!
Please, there's no need for apologies.
In fact, I have a confession to make to everyone.
Almost a year ago, I decomissioned those wonderful diploe subs I loved so much and I still miss them to this very day.
The reason I let them go is the simple fact that they were just entirely too large for my room and were totally destroying the imaging and soundstaging of my main loudspeakers.
I now have an SVS PB12-ISD/2 subwoofer which provides excellent bass all the way down to 12Hz in my room (114dB @ 16Hz) which gives me some spectacular earth moving experiences to say the least! That I can say is one thing those dipoles could never do, at least not to this degree.
On the other hand though, the SVS still doesn't provide the ultimate slam, ultra fast attact and complete open detail of those huge and ugly dipoles of mine.
However, thanks to you I am now very interested in these "Ripole" designs. The good news is that I still have those 15" Pyle drivers and they seem to be acceptable in the ripole designs as well.
I look forward to reading your new thread on this design. Who knows, I might be out in the front yard again soon building quad ripoles!! Not to replace my SVS, but just to play around with.
Also from what I have read so far in the last few posts of this thread, am I to understand that with these ripole designs, lower frequencies can be realised with the same drivers?!
Hmmmm......
Rudolf said:Since I didn´t want to hijack this thread any longer, I have started a new one with almost anything about ripoles I could provide:
http://www.diyaudio.com/forums/showthread.php?s=&postid=568432#post568432
Hope I can feed your curiosity
And my apologies to chops who started this in the first place.
Rudolf
Hello there Rudolf!
Please, there's no need for apologies.
In fact, I have a confession to make to everyone.
Almost a year ago, I decomissioned those wonderful diploe subs I loved so much and I still miss them to this very day.
The reason I let them go is the simple fact that they were just entirely too large for my room and were totally destroying the imaging and soundstaging of my main loudspeakers.
I now have an SVS PB12-ISD/2 subwoofer which provides excellent bass all the way down to 12Hz in my room (114dB @ 16Hz) which gives me some spectacular earth moving experiences to say the least! That I can say is one thing those dipoles could never do, at least not to this degree.
On the other hand though, the SVS still doesn't provide the ultimate slam, ultra fast attact and complete open detail of those huge and ugly dipoles of mine.
However, thanks to you I am now very interested in these "Ripole" designs. The good news is that I still have those 15" Pyle drivers and they seem to be acceptable in the ripole designs as well.
I look forward to reading your new thread on this design. Who knows, I might be out in the front yard again soon building quad ripoles!! Not to replace my SVS, but just to play around with.
Also from what I have read so far in the last few posts of this thread, am I to understand that with these ripole designs, lower frequencies can be realised with the same drivers?!
Hmmmm......
Highish Ots and low Fs (as you both want for a dipole sub driver) are somewhat contradicting requirements. The cheapiest way to do it is to raise the cone mass which surely will lower Fs. That way you may end with a heavy cone that is only marginally controlled by a weak magnet.JWFokker said:
So a reasonably low Mms is just a proof that some level of quality has been maintained.
chops,
yes, you will be able to lower the frequency compared to your "airy" older design. The reduced air volume in front and back of the drivers will act as a "radiaton resistance" - the less air, the more lowering.
If you are going to mount two speakers push-push to get impulse compensation, please do NOT mount them as recommended by Linkwitz. Try to keep the design as symmetrical as possible, because the facing speakers will be coupled tighter by the small air volume between them than in your old design. So both speakers should have the same air volume in front of the cone. Same for the back.
As an optimum the back of the cone should "see" about the same air volume as the front (symmetry here again). Remember that the air "inside" the cone adds to the front air volume and has to be subtracted (together with the basket and magnet) from the back air volume.
Don´t let those Pyles collect rust in some corner.
yes, you will be able to lower the frequency compared to your "airy" older design. The reduced air volume in front and back of the drivers will act as a "radiaton resistance" - the less air, the more lowering.
If you are going to mount two speakers push-push to get impulse compensation, please do NOT mount them as recommended by Linkwitz. Try to keep the design as symmetrical as possible, because the facing speakers will be coupled tighter by the small air volume between them than in your old design. So both speakers should have the same air volume in front of the cone. Same for the back.
As an optimum the back of the cone should "see" about the same air volume as the front (symmetry here again). Remember that the air "inside" the cone adds to the front air volume and has to be subtracted (together with the basket and magnet) from the back air volume.
Don´t let those Pyles collect rust in some corner.
O my gawd, where did my Sunday go? This one one monster thread...but v. interesting.
I got inspired to see what kind of driver I could find here in Oz, and my searching turned up the Pyle PLG15 available for AU$70 (I suspect it's a runout).
T/S Parameters from Pyle site look sweet:
Fs: 26.4Hz
Qes: 0.97
Qms: 3.06
Qts: 0.73
Sens: 90dB
Xmax: 24mm (hmm, suppose they mean 12 each way)
Now my question is this: If I can only afford 2 (both in terms of space and money), is my best bet to go for a U-frame design? My only concern is that distortion might be a bit high given the cut-price construction (compared with push-pull H-frame).
I have read about the N-Frames and Ripols but am too dense to determine which would be the best design for me (to cross over to SL PMTM1-like main panels).
Any advice would be much appreciated,
TIA,
//Adam F
I got inspired to see what kind of driver I could find here in Oz, and my searching turned up the Pyle PLG15 available for AU$70 (I suspect it's a runout).
T/S Parameters from Pyle site look sweet:
Fs: 26.4Hz
Qes: 0.97
Qms: 3.06
Qts: 0.73
Sens: 90dB
Xmax: 24mm (hmm, suppose they mean 12 each way)
Now my question is this: If I can only afford 2 (both in terms of space and money), is my best bet to go for a U-frame design? My only concern is that distortion might be a bit high given the cut-price construction (compared with push-pull H-frame).
I have read about the N-Frames and Ripols but am too dense to determine which would be the best design for me (to cross over to SL PMTM1-like main panels).
Any advice would be much appreciated,
TIA,
//Adam F
If I can only afford 2 (both in terms of space and money), is my best bet to go for a U-frame design?
For Me, it would depend on how high the target crossover was and how loud and how big.
If its a subwoofer that crossover at 100 or less, I might try a W first. A W is compact, the symmetry cancels some second harmonic distortion and it has minimum room interaction.
If I needed a higher crossover, the U or H would be better.
All 3 could share the same baffles, and its possible to make a "convertible" enclosure that can be either u or H, by removing screws and repositioning the baffle.
Those drivers sound like they were designed for OB use, and I am sure they will be a terrific value.
Good luck.
Doug
For Me, it would depend on how high the target crossover was and how loud and how big.
If its a subwoofer that crossover at 100 or less, I might try a W first. A W is compact, the symmetry cancels some second harmonic distortion and it has minimum room interaction.
If I needed a higher crossover, the U or H would be better.
All 3 could share the same baffles, and its possible to make a "convertible" enclosure that can be either u or H, by removing screws and repositioning the baffle.
Those drivers sound like they were designed for OB use, and I am sure they will be a terrific value.
Good luck.
Doug
When using cheap woofers it's always a good idea to pair them in a push/pull alignment to reduce distortion from imperfections from linear operation of the drivers. You could do this in a WBaffle, Ubaffle, or H baffle, but you'd have a single speaker with both drivers.
An H baffle is just a waste of wood. You can cut off all the wood extending in front of the driver baffle and lose zero bass extension. The only difference is a slight loss of pure dipole dispersion, but not enough for the 2 room modes eliminated by dipole to come into play.
If instead of cutting the wood off, you move the baffle to the front, then you have a U baffle and pick up 6db at the bottom. A Wbaffle is a great idea as long as you are staying below 100hz or so, because you cancel the mechanical vibrations as well and the most compact cab. The W gives you the same extension as a similar depth H baffle. Then you can always pick up more extension with the Wbaffle layout by turning it into a U baffle by adding 50% more depth (only at the back) and pick up 6db of max output at the bottom.
If you go with a 2 driver U or H, build it just large enough for the drivers to fit on the baffle. Anything more is a waste of wood and will lower the frequency where resonances can occur due to the parallel surfaces. Also, plan on laying them on their side because you will get more bass that way due to the increased infinite baffle effect of the floor.
An H baffle is just a waste of wood. You can cut off all the wood extending in front of the driver baffle and lose zero bass extension. The only difference is a slight loss of pure dipole dispersion, but not enough for the 2 room modes eliminated by dipole to come into play.
If instead of cutting the wood off, you move the baffle to the front, then you have a U baffle and pick up 6db at the bottom. A Wbaffle is a great idea as long as you are staying below 100hz or so, because you cancel the mechanical vibrations as well and the most compact cab. The W gives you the same extension as a similar depth H baffle. Then you can always pick up more extension with the Wbaffle layout by turning it into a U baffle by adding 50% more depth (only at the back) and pick up 6db of max output at the bottom.
If you go with a 2 driver U or H, build it just large enough for the drivers to fit on the baffle. Anything more is a waste of wood and will lower the frequency where resonances can occur due to the parallel surfaces. Also, plan on laying them on their side because you will get more bass that way due to the increased infinite baffle effect of the floor.
Yes. For all the reasons that johninCR stated.
If building the sub in the house is an option, check out this site:
Cult of the Infinitely Baffled
Doug
Thanks guys, more reading to do
Does this statement:
"For an IB, the Qtc of the system is approximately the Qts of the driver. If you like very tight bass, chose a lower Qts driver. If you like the "HT" sound, then chose a driver with a higher Qts."
...hold true for dipole woofers? There is another driver I can get for the same price called an MTX RT12-04, with following params:
Fs: 31.3Hz
Xmax: 8.13mm
Qts: 0.502
Sens: 93.5dB
Obviously the output would be greatly reduced, but is it likely to have much better transient response? It also has a nicer spider design:
Given that quality and integration with the main panels is my main concern rather than SPL, which should I choose?
//Adam F
Does this statement:
"For an IB, the Qtc of the system is approximately the Qts of the driver. If you like very tight bass, chose a lower Qts driver. If you like the "HT" sound, then chose a driver with a higher Qts."
...hold true for dipole woofers? There is another driver I can get for the same price called an MTX RT12-04, with following params:
Fs: 31.3Hz
Xmax: 8.13mm
Qts: 0.502
Sens: 93.5dB
Obviously the output would be greatly reduced, but is it likely to have much better transient response? It also has a nicer spider design:
An externally hosted image should be here but it was not working when we last tested it.
Given that quality and integration with the main panels is my main concern rather than SPL, which should I choose?
//Adam F
From the data on paper I would stay with the Pyles. My reasons:
Qts~0,7 is perfect for good transients and you will have to equalise less. BTW. If you equalise both drivers to have the same frequency response, the resulting Qt (from driver plus EQ) will be the same too.
The single virtue you will need most is Xmax. There is a clear leader in that!
You shoudn´t try to push the driver below Fs. So 26,4 Hz seems to be better than 31,3 Hz.
Since any dipoles will reach their mechanical limits WAY before the electrical, 3 dB difference in efficiency is no issue at all.
Qts~0,7 is perfect for good transients and you will have to equalise less. BTW. If you equalise both drivers to have the same frequency response, the resulting Qt (from driver plus EQ) will be the same too.
The single virtue you will need most is Xmax. There is a clear leader in that!
You shoudn´t try to push the driver below Fs. So 26,4 Hz seems to be better than 31,3 Hz.
Since any dipoles will reach their mechanical limits WAY before the electrical, 3 dB difference in efficiency is no issue at all.
The only issue with the Pyle PLG15 as I pointed out in this thread http://www.diyaudio.com/forums/showthread.php?s=&threadid=59359
is vent noise when used as a dipole (I have 2 PLG15s bought a while back for dipole use). The solution (or compromise, since VC temp will rise) is the either remove the dustcap http://www.diyaudio.com/forums/showthread.php?s=&threadid=59843
or drill maybe a 1.5" hole in the center of the cap (the VC is 2.5" dia. - another reason I bought the driver) then glue an disc of the type of foam used in the back that allows "breathing". This will slow the air velocity within the gap and cut down on the noise. As I stated before, it comes at the price of increased VC temp. However (yet another reason I chose this driver) it also has vents around the spider. I don't think the VC temp will be an issue under "normal" listening, since, "normally" this driver would be in a box (higher temp) and booming bass that can be herad half a mile away(aka "car" stereo)
Here is a pic from the original thread of the cooling vents.
Cheers,
AJ
is vent noise when used as a dipole (I have 2 PLG15s bought a while back for dipole use). The solution (or compromise, since VC temp will rise) is the either remove the dustcap http://www.diyaudio.com/forums/showthread.php?s=&threadid=59843
or drill maybe a 1.5" hole in the center of the cap (the VC is 2.5" dia. - another reason I bought the driver) then glue an disc of the type of foam used in the back that allows "breathing". This will slow the air velocity within the gap and cut down on the noise. As I stated before, it comes at the price of increased VC temp. However (yet another reason I chose this driver) it also has vents around the spider. I don't think the VC temp will be an issue under "normal" listening, since, "normally" this driver would be in a box (higher temp) and booming bass that can be herad half a mile away(aka "car" stereo)
Here is a pic from the original thread of the cooling vents.
Cheers,
AJ
That would be fine, you would retain greater stiffness in the cap that way. But you also increase your chances of a slip up - so be careful! Also make sure you do this with the driver facing downwards (kinda like working underneath your car). You must be careful not to get debris in the gap. A vacuum of some sort going at the same time would not hurt either. BEFORE you do any of this of course, you should mount the driver on a baffle and drive it hard so you see if you find the noise objectionable. If you are mounting in a W-frame, it may not even be an issue. Again, be careful, it won't take that much power to drive it to Xmax @ 20hz mounted free-air.
Cheers,
AJ
Cheers,
AJ
Due to the drastically lower power handling in a dipole configuration, what's wrong with just plugging up the vented pole, or at least stuff something in the vent to slow the air movement and eliminate noise that way. Won't opening up the dust cap end just increase the air flow and give you another source of noise?
Hi John,
Perhaps a little driver internals 101 is needed. Look at the pic below of a dustcap removed (not a PLG15 btw). Now you just have a hole running through the pole. There is nothing forcing air through the hole when the cone moves. With the cap on, you would have a (almost) sealed cavity of air under the the cap. The cones outward motion would pull air into the vent as the size of the cavity increases, then push air out as the cone/cap moves backwards and the size of the cavity decreases. thats one of the many functions of the cap. Another is stiffness added to the cone structure. Removing it will reduce stiffness - and affect the drivers performance. Multiple small holes, or one bigger one in the center won't be quite as bad. It's all about compromises, which is why I stressed in my post above to try the driver without any mods 1st, then decide. Luckily, if you wreck the Pyle, its $37! Still my reigning value champ
Cheers,
AJ
- no, no, no - you definately don't want to do that! Plugging/stuffing the pole vent would increase pressure underneath the dustcap cavity are force the air out through the small vent holes drilled into the base of the cone near the spider (sorry, no pics of those). Not good!
- the opposite! Lets put it this way. If you removed the cap entirely, there would be NO airflow in/out the vent. Thats what the dustcap is doing. When the cone moves back and forth, the dustcap is pushng and pulling air through the vent. By opening the cap and allowing it to breathe (see my post about puting a foam disc on), you get much reduced pressure inside the cavity above the pole and less air is going to be pushed/pulled along the vent.
Perhaps a little driver internals 101 is needed. Look at the pic below of a dustcap removed (not a PLG15 btw). Now you just have a hole running through the pole. There is nothing forcing air through the hole when the cone moves. With the cap on, you would have a (almost) sealed cavity of air under the the cap. The cones outward motion would pull air into the vent as the size of the cavity increases, then push air out as the cone/cap moves backwards and the size of the cavity decreases. thats one of the many functions of the cap. Another is stiffness added to the cone structure. Removing it will reduce stiffness - and affect the drivers performance. Multiple small holes, or one bigger one in the center won't be quite as bad. It's all about compromises, which is why I stressed in my post above to try the driver without any mods 1st, then decide. Luckily, if you wreck the Pyle, its $37! Still my reigning value champ
Cheers,
AJ
An externally hosted image should be here but it was not working when we last tested it.
Hmm I've just taken delivery of my Pyle drivers (heh) and re-read page 39 of this thread.
Rudolf recommends a symmetrical arrangement for a W-frame like the one at the bottom of this page: http://www.linkwitzlab.com/woofer3.htm
I was planning to build the other one just above, but this comment has given me pause. Can someone please explain in lay terms why Linkwitz only recommends the symmetrical arrangement for stacked woofers and not a single W-frame?
SL says:
"the two drivers in each of the stacked cabinets can be mounted for a cleaner front-to-rear acoustic path. In that case even order distortion reduction is obtained by reversing one of the cabinets as shown below."
Does this imply that the a single symmetrical w-frame as recommended by Rudolf (I think) is going to have higher even-order distortion?
Finally I am going to have to connect these drivers in series or to separate channels due to the load on the amp - does that make a difference to which design I should choose?
As a better informed contributor once said, thanks for your patience
//Adam F
Rudolf recommends a symmetrical arrangement for a W-frame like the one at the bottom of this page: http://www.linkwitzlab.com/woofer3.htm
I was planning to build the other one just above, but this comment has given me pause. Can someone please explain in lay terms why Linkwitz only recommends the symmetrical arrangement for stacked woofers and not a single W-frame?
SL says:
"the two drivers in each of the stacked cabinets can be mounted for a cleaner front-to-rear acoustic path. In that case even order distortion reduction is obtained by reversing one of the cabinets as shown below."
Does this imply that the a single symmetrical w-frame as recommended by Rudolf (I think) is going to have higher even-order distortion?
Finally I am going to have to connect these drivers in series or to separate channels due to the load on the amp - does that make a difference to which design I should choose?
As a better informed contributor once said, thanks for your patience
//Adam F
Hi Adam,
The Linkwitz 2 driver Wbaffle isn't symetrical with regard to the left and right pathways not being equal, because he uses push/pull to reduce distortion. What he is saying about stacking is that with a stacked pair (4 drivers), you can build them symmetrically (cones facing each other and equal size pathways left and right). Then you just turn one around and swap the wiring to end up with push/push in one cab and pull/pull in the other cab, which nets to push/pull and you get the distortion reduction benefit and symmetrical pathways.
The Linkwitz 2 driver Wbaffle isn't symetrical with regard to the left and right pathways not being equal, because he uses push/pull to reduce distortion. What he is saying about stacking is that with a stacked pair (4 drivers), you can build them symmetrically (cones facing each other and equal size pathways left and right). Then you just turn one around and swap the wiring to end up with push/push in one cab and pull/pull in the other cab, which nets to push/pull and you get the distortion reduction benefit and symmetrical pathways.
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