I suspect most people criticizing the PPSL have never hear one.
Complaints about 3rd harmonics, if valid, would also apply to all servo-feedback woofers.
When Les Hudson listened to his first PPSL he imediately remarked that it sounded like a servo woofer. So if you detest the Infinity, Velodyne, etc. servo subs you should probably not build a PPSL.
Shorting rings in the magnet structure are largely ineffective at reducing distortion in the bottom octave, they do work well above 100hz or so.
Complaints about 3rd harmonics, if valid, would also apply to all servo-feedback woofers.
When Les Hudson listened to his first PPSL he imediately remarked that it sounded like a servo woofer. So if you detest the Infinity, Velodyne, etc. servo subs you should probably not build a PPSL.
Shorting rings in the magnet structure are largely ineffective at reducing distortion in the bottom octave, they do work well above 100hz or so.
Thanks for summarizing. I just need to build one now. I have a pair of 8" subs and a pair of 10's that need a nice cabinet. I am doing multiple subs in my listening area, so one or two small PPSL would fit in nicely 
Do you have the acronym PPSL copyrighted? I was thinking of making an (isobaric) IBPPSLPR
Do you have the acronym PPSL copyrighted? I was thinking of making an (isobaric) IBPPSLPR
You can de-select "lock Vb" by selecting "lock dimensions". Just take note of your desired Vb and adjust dimensions accordingly. I'm going off of memory, so I hope I ....remembered correctly
I'm just curious - what part of the tapped horn system turns you off/do you frown upon or not understand?
ppsl vs tapped horn vs tcb enclosures
I am very interested in Scott's adaptation of this design to use with a horn. While I too have trouble designing a tapped horn, I have made them and feel their benefit is to get a lot out of smaller drivers. I am curious what others think about them. I believe a pr of 15" drivers like the jbl 2226h can work well in a tapped horn, but size and build difficulty need to be worth it in terms of the ultimate sound.
Lots of thoughts here, I hope some others have something to share.
Phil
I think you did, its been a week or so since I last modeled, but through trial and error I did finally figured it out. Thanks for the follow up, it is really appreciated.. I also got some addl modelng help from djk, and once I build these, I intend to post my results and especially thank djk who has really made this all happen. I was very close to building a triple chamber bandpass which would have been much bigger, heavy, tougher to build and most importantly, not as good sounding. I will also be able to compare the sound directly against the jbl bass reflex version which sound a bit muddy to me, not as clean or fast as I think it can be with the right box. It needs to blend well with horns, and it appears that Les Hudson has implemented this very well.You can de-select "lock Vb" by selecting "lock dimensions". Just take note of your desired Vb and adjust dimensions accordingly. I'm going off of memory, so I hope I ....remembered correctly
I am very interested in Scott's adaptation of this design to use with a horn. While I too have trouble designing a tapped horn, I have made them and feel their benefit is to get a lot out of smaller drivers. I am curious what others think about them. I believe a pr of 15" drivers like the jbl 2226h can work well in a tapped horn, but size and build difficulty need to be worth it in terms of the ultimate sound.
Lots of thoughts here, I hope some others have something to share.
Phil
figured it out
Actually the problem was that I had selected shape = prisim square opt. If you just choose prisim sq. the software lets you chose all the dimensions and only changes the Vb.
Actually the problem was that I had selected shape = prisim square opt. If you just choose prisim sq. the software lets you chose all the dimensions and only changes the Vb.
You can de-select "lock Vb" by selecting "lock dimensions". Just take note of your desired Vb and adjust dimensions accordingly. I'm going off of memory, so I hope I ....remembered correctly
I have never built a PPSL Woofers, but
"My Daddy done told me"
"When I was a schoolboy"
"That multi-woofers need multi-ports to distribute pressure"
"Or uneven angular air pressures can tilt a cone and cause voice coil rub"
My Daddy liked Elvis. My Daddy could not rhyme.
Old school Altec woofers with paper surrounds had much more fragile spiders than modern subwoofers with thick rubber surrounds. A bass cabinet with multiple woofers will generate unequal forces from the different air mass from each speaker bouncing off walls, and this imbalance can cause angular rocking of a voice coil until it rubs on the pole piece. It was not uncommon for old school multi-woofer cabinets to distribute multiple ports in order to equalize air pressure inside the cabinet. Round ports with large radius terminations are proven superor(1-1.5 higher peak SPL before audible huffing) to equal area square ports.
Would a PPSL woofer with four ports help equalize the angular pressures on the cone spiders? The 18Sounds manifold has four corner ports?
Does a minor slant of the slot deliver a superior coherent wave launch plus a spreading of slot resonances??
"My Daddy done told me"
"When I was a schoolboy"
"That multi-woofers need multi-ports to distribute pressure"
"Or uneven angular air pressures can tilt a cone and cause voice coil rub"
My Daddy liked Elvis. My Daddy could not rhyme.
Old school Altec woofers with paper surrounds had much more fragile spiders than modern subwoofers with thick rubber surrounds. A bass cabinet with multiple woofers will generate unequal forces from the different air mass from each speaker bouncing off walls, and this imbalance can cause angular rocking of a voice coil until it rubs on the pole piece. It was not uncommon for old school multi-woofer cabinets to distribute multiple ports in order to equalize air pressure inside the cabinet. Round ports with large radius terminations are proven superor(1-1.5 higher peak SPL before audible huffing) to equal area square ports.
Would a PPSL woofer with four ports help equalize the angular pressures on the cone spiders? The 18Sounds manifold has four corner ports?
Does a minor slant of the slot deliver a superior coherent wave launch plus a spreading of slot resonances??
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Any drivers that should be avoided due to noisy venting of the VC?
IIRC LAB 12 was mentioned earlier and was unsuitable as any benefit distortion wise was undone by air noise at volumes where lowering distortion would matter the most.
Have anyone made the plenum the port, kind of like a TH but different?
What are the thermal effects when driven hard for PA? I can imagine the thermal imbalance between the drivers (as one will be getting better cooling than the other) to upset the equal suppression of 2H as they will no longer be mirroring each others action.
IIRC LAB 12 was mentioned earlier and was unsuitable as any benefit distortion wise was undone by air noise at volumes where lowering distortion would matter the most.
Have anyone made the plenum the port, kind of like a TH but different?
What are the thermal effects when driven hard for PA? I can imagine the thermal imbalance between the drivers (as one will be getting better cooling than the other) to upset the equal suppression of 2H as they will no longer be mirroring each others action.
To my thinking, the manifold should have some absorbtion in the back of it to both damp any manifold resonances and also absorb some of the distortion components and/or pole vent noises.
And I don't think that in a PPSL, pole vent noises are going to mean much- first they'll be suppressed because they're not facing the listener, second, if the woofers are pumping that hard, the overall SPL will be high and tend to mask those components.
Also, I tend to think that large excursions any significant amount of time are indicative of undersized subs- you need the xmax occasionally but if you're using it often enough that vent noise is a meaningful issue, time to up the cone area.
And I don't think that in a PPSL, pole vent noises are going to mean much- first they'll be suppressed because they're not facing the listener, second, if the woofers are pumping that hard, the overall SPL will be high and tend to mask those components.
Also, I tend to think that large excursions any significant amount of time are indicative of undersized subs- you need the xmax occasionally but if you're using it often enough that vent noise is a meaningful issue, time to up the cone area.
Finished my PPSL
Much thanks to Dennis, I made a pair of PPSL's using his basic design customized for JBL 2226h's. I had been using the 4 drivers in the usual JBL 4508 enclosures meant for PA use. While the sound was ok, they seemed a bit slow/muddy even with EQ and were 97db efficient vs my horns at 112db. The other big factor is their size and weight was didn't work asthetically in my livingroom. As for the PPSL's- My initial impressions of the sound were similar to others in that first impressions were a lack of bass. I have not seen much discussion on how well the bass box pro plot compared to actual. While I don't have rew, I did use pink noise w/the behringer mike 3' from the box and photo'd the deq's display. Both drivers are identical in their frequency output, and there is a significant drop out at 300-500hz, and a much smaller one around 80hz. I'm able to eq these flat, but still, I can't explain the limited high requency result. I'm sure Dennis will have some insight. EQ'd, the sound is good, I'm still working on it, but it adds about 6db's more efficiency, 1/2 the weight and 1/3 the size of the orig. jbl boxes. I do wonder if the reduced harmonic distortion isn't perceived as less full/rich sounding, similar to the perception of tubes vs ss electronics.
Much thanks to Dennis, I made a pair of PPSL's using his basic design customized for JBL 2226h's. I had been using the 4 drivers in the usual JBL 4508 enclosures meant for PA use. While the sound was ok, they seemed a bit slow/muddy even with EQ and were 97db efficient vs my horns at 112db. The other big factor is their size and weight was didn't work asthetically in my livingroom. As for the PPSL's- My initial impressions of the sound were similar to others in that first impressions were a lack of bass. I have not seen much discussion on how well the bass box pro plot compared to actual. While I don't have rew, I did use pink noise w/the behringer mike 3' from the box and photo'd the deq's display. Both drivers are identical in their frequency output, and there is a significant drop out at 300-500hz, and a much smaller one around 80hz. I'm able to eq these flat, but still, I can't explain the limited high requency result. I'm sure Dennis will have some insight. EQ'd, the sound is good, I'm still working on it, but it adds about 6db's more efficiency, 1/2 the weight and 1/3 the size of the orig. jbl boxes. I do wonder if the reduced harmonic distortion isn't perceived as less full/rich sounding, similar to the perception of tubes vs ss electronics.
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