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-   -   A Thread for those interested in PPSL enclosures (http://www.diyaudio.com/forums/subwoofers/177905-thread-those-interested-ppsl-enclosures.html)

jamikl 25th November 2010 10:12 PM

A Thread for those interested in PPSL enclosures
 
This is a new thread as suggested by Moray James.
For Moray James: What I did was to simulate the enclosure with
two speakers in Horn Response. I simulated it as you would an Altec
A7 type of speaker but with a front chamber on the horn. This front chamber
would be the plenum if I am doing it right. The plenum opening was the horn throat. I rounded the opening a couple of centimetres and used this as the horn. I did do the combined sim to take into account the vents. As I said
in the other thread, I don't know if this is anywhere near accurate.

Any input from those who have done this type of design would be most welcome.
jamikl

tb46 26th November 2010 03:59 PM

PPSL in Hornresp
 
Hi jamikl,

I think your model places the speakers at the throat of the front horn (e.g.: CH driver arrangement), I may be better to have them entering the horn from the side @ S2 as in the OD arrangement.

I posted in the http://www.diyaudio.com/forums/subwo...designs-3.html thread, Post #30, that I would ask David McBean for help in his Hornresp thread: http://www.diyaudio.com/forums/subwo...ml#post2377713 , and he answered in Post #1464. I posted a sample PPSL Hornresp Input Screen in Post #1463, and feel relatively confident, that that is the correct way to model a PPSL in Hornresp.

The OD driver arrangement allows you to position the drivers in a short horn of two sections, by keeping the areas S1-S4 the same you create the plenum, and by OD definition the driver is located @ S2.

You then use Vrc/Lrc/Ap/Lpt to define you back-chamber BR.

Be sure to use the Combined Response for the SPL and resulting Impulse Response.

Hopefully someone has some practical dimensions and measurements to compare to the models.

Regards,

moray james 26th November 2010 05:41 PM

Thank you Oliver. That's great. Best regards Moray James.

jamikl 27th November 2010 06:02 AM

Hi tb46. Yes I saw your question on the other thread and David's response. I thought I might be doing it wrong but it was quite awhile ago and I didn't know about the other facility in Horn Response so I tried what I tried!!!

Will do it David's way when I get a chance. I did try a la scala derivative with
two 12 Inch speakers and posted the result somewhere awhile ago. Its on this forum somewhere!!!
jamikl

tb46 1st December 2010 03:45 PM

Shape of plenum chamber
 
2 Attachment(s)
Hi guys,

When looking at some models in Hornresp I found a pronounced peak in the PPSL frequency response that does not seem to be easy to tame. This may just be something I'm doing wrong, or it may be typical for this type enclosure. I then changed the plenum from its rectangular form to a triangular form and the peak becomes much easier to control in the model.

Maybe somebody who knows something about PPSL enclosures (e.g.: djk :-)) can shine some light on this; or maybe we're on to something.

Regards,

djk 2nd December 2010 10:52 AM

Your first graph looks like what it does when both drivers face into the plenum, a cavity resonance.

When you flip one of the drivers magnet structure into the plenum the cavity resonance seems to disappear.

tb46 5th December 2010 02:21 AM

Hi djk,

I spend the last week rebuilding my computer after a virus attack.

It makes sense that the volume reduction inside the plenum would make a difference, especially if the plenum is kept to a minimum.

Thanks for the additional information.

Regards,

salzburgsoundsystem 4th May 2011 08:54 AM

Ports?
 
This is another thread I've been looking forward to!

Am I mistaken, or do these subwoofer cabinet designs lack the ports that DJK had on some of his enclosures?

Regards, Ben

hawkson 4th May 2011 09:27 AM

What are the benefits of PPSL vs Dual for an 18 inch, high powered amp build? Goal is low and clean and loud!

Cant find too much on PPSL...

djk 4th May 2011 09:51 AM

"Am I mistaken, or do these subwoofer cabinet designs lack the ports that DJK had on some of his enclosures?"

The basic idea behind PPSL is the plenum with the push-pull mounted drivers. The box could be sealed, vented, 6th order vented (most of my designs are 6th order vented), or even dipole (the Linkwitz sub).

"What are the benefits of PPSL"

Distortion reduction.

When I built the first model PPSL over 20 years ago it sounded so different (compared to a 'normal' speaker) that I didn't realize what I was hearing (lack of distortion). It was only when I compared it with a large corner horn that I realized what was happening, that the PPSL was cleaner, less colored, and more musical.

"Cant find too much on PPSL... "

Google

PPSL djk About 1,920 results (0.25 seconds)
1.
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Both SL and DJK are smart cookies. They chose this topology for very ... Maybe it would help if you explained how each would work in a PPSL? ...
AVS Forum › ... › Audio Related › DIY Speakers and Subs - Cached
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PPSL les hudson About 896 results (0.27 seconds)
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High Efficiency Speaker Asylum
http://usr.audioasylum.com/images/3/33876/100_1147.jpg
Just completed a new experiment Push-Pull double 15" subwoofer. This is the best sounding subwoofer that I've ever heard after building sub cabinets for 33 yrs. Love it. Les Hudson


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