A Thread for those interested in PPSL enclosures - Page 31 - diyAudio
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Old 27th June 2012, 02:20 AM   #301
djk is offline djk
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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.
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Old 27th June 2012, 08:41 PM   #302
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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
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Old 1st July 2012, 12:33 PM   #303
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Quote:
Originally Posted by pumpkin1 View Post
Is there some trick to forcing the software to hold 2 of 3 dimensions and add the 3rd to = the chosen 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
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Old 1st July 2012, 12:36 PM   #304
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Quote:
Originally Posted by Scott L View Post
I really don't understand tapped horns- they don't make a bit of sense to me
I'm just curious - what part of the tapped horn system turns you off/do you frown upon or not understand?
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Old 1st July 2012, 07:03 PM   #305
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Default ppsl vs tapped horn vs tcb enclosures

Quote:
Originally Posted by CRESCENDO View Post
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 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.
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
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Old 2nd July 2012, 10:03 PM   #306
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Are there some calculations about PPSL subs? or program, or examples somewhere, I have martins sheets but these don,t cover this sub.

thanks.
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Old 3rd July 2012, 12:02 AM   #307
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Model it as an ordinary box, whatever type that suits your drivers (sealed, vented, OB, etc).
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Old 3rd July 2012, 04:31 PM   #308
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Default 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.
Quote:
Originally Posted by CRESCENDO View Post
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
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Old 26th July 2012, 10:09 PM   #309
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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??
Attached Images
File Type: jpg MultiPorts.jpg (55.0 KB, 459 views)
File Type: jpg PPSL Woofers.jpg (57.2 KB, 469 views)
File Type: jpg manifold.jpg (467.6 KB, 469 views)
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Old 26th July 2012, 10:32 PM   #310
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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.
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