A Thread for those interested in PPSL enclosures

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jamikl

Member
2005-05-31 8:24 am
Melbourne
  • #1
    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
     
    T

    tb46

    Member
    2006-01-09 7:04 pm
    Texas
  • #2
    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/subwoofers/176729-klipsch-horn-woofer-designs-3.html thread, Post #30, that I would ask David McBean for help in his Hornresp thread: http://www.diyaudio.com/forums/subwoofers/119854-hornresp-147.html#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,
     
    J

    jamikl

    Member
    2005-05-31 8:24 am
    Melbourne
  • #4
    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
     
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    tb46

    Member
    2006-01-09 7:04 pm
    Texas
  • #5
    Shape of plenum chamber

    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,
     

    Attachments

    • PPSL_rect_v_tri_plenum_ACAD.pdf
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    • Rect_v_Tri_penum_all_b.jpg
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    djk

    djk

    R.I.P
    2001-02-04 4:23 am
    USA
  • #10
    "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.
    Push-pull Slot Loading (PPSL) sub drivers? [Text View] - AVS Forum
    20 posts - 9 authors - Last post: Jan 4
    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
    ******************************************************
    PPSL les hudson About 896 results (0.27 seconds)
    *************************************************************
    High Efficiency Speaker Asylum
    [IMGDEAD]http://usr.audioasylum.com/images/3/33876/100_1147.jpg[/IMGDEAD]
    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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    Antripodean

    Member
    2008-12-15 8:22 pm
    www.xtr.com
  • #14
    djk said:
    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).
    Click to expand...

    So, to check my understanding, is there any difference between a sealed PPSL and a sealed isobaric? The principle seems the same. Has there been any comparison of the two?
     
    djk

    djk

    R.I.P
    2001-02-04 4:23 am
    USA
  • #15
    The sealed PPSL is twice the size of the isobaric, and 3dB more efficient, with 6dB more maximum output.

    "B&C 21SW152"

    That looks like a nice driver, but it fits in a small box and the port required for the x-max the driver has may be a problem. Check the port size in your speaker program and see it you can make it work.

    Most 18s don't look too bad, I have made a couple of different dual 18 PPSL for PA use.
     
    H

    hawkson

    Member
    2011-04-06 5:24 am
  • #17
    djk said:
    The sealed PPSL is twice the size of the isobaric, and 3dB more efficient, with 6dB more maximum output.

    "B&C 21SW152"

    That looks like a nice driver, but it fits in a small box and the port required for the x-max the driver has may be a problem. Check the port size in your speaker program and see it you can make it work.

    Most 18s don't look too bad, I have made a couple of different dual 18 PPSL for PA use.
    Click to expand...


    I am now deciding between a I) Dual Sealed Opposed build, II)multiple small sealed, and a III)PPSL Opposed Sealed. (Compound PPSL). DJK, most of the PPSL's you and Les online pictures of are Slot Loaded PPSL for PA. These seem harder to design and build than a PPSL Opposed Sealed design.

    1. What is the advantage of having the plenum/slot loading manifold design in PPSL compared to a Dual Opposed PPSL.

    2. Can you comment on the usage of PPSL for Home Theater? I've only seen you and Les building them for PA. Some users have commented that they won't work well down low??


    Please correct me if I am wrong--
    My current thoughts are to build a dual opposed PPSL. Why?
    a) The design is easy, its like a Dual Opposed Sealed but with one driver and mount facing in.
    b) In terms of modelling and building it, as long as I have enough internal space and amp power, what else should I worry about? Other designs have angles, horn length, port length etc. This design is a sealed box
    c) This is better than 2 individual sealed 18's because of the ?even? harmonic cancellation. Right?


    Thanks for the input, especially the parts in bold
     
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    bjorno

    R.I.P.
    2005-03-17 9:36 am
    Jacobsmountain
  • #18
    ..2. Can you comment on the usage of PPSL for Home Theater? I've only seen you and Les building them for PA. Some users have commented that they won't work well down low??
    Click to expand...

    HI,My :2c::

    I would guess the PPSL shares similar SQ performance(= high) with a T-TQWT/T-TQWP if build sturdy, i.e. not letting any CSA:s larger than ~10”x 10” to be un-braced.
    The differences when placed in a room would be : The PPSL sums sound pressures in the far-field thus shows directionality but the T-TQWT/T-TQWP acts like an omni pressure point-source and is not sensitive if placed jammed very close to other in room objects. Its like comparing in room performance using a closed sub to a corresponding ported.


    ..Please correct me if I am wrong--
    My current thoughts are to build a dual opposed PPSL. Why?
    a) The design is easy, its like a Dual Opposed Sealed but with one driver and mount facing in.
    b) In terms of modelling and building it, as long as I have enough internal space and amp power, what else should I worry about? Other designs have angles, horn length, port length etc. This design is a sealed box ..
    Click to expand...

    Comparing a closed PPSL would be like to compare with a closed T-QPPSL( easy to simulate in HR): Both offering very similar performance: Internally the the PPSL behaves like an ordinary closed box but the T-QPPSL like an closed TL,i.e. Lambda/2 behavior. See the picture:

    b :)
     

    Attachments

    • T-TQWT-morphing-into-PPSL.GIF
      T-TQWT-morphing-into-PPSL.GIF
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    tb46

    Member
    2006-01-09 7:04 pm
    Texas
  • #19
    Hi hawkson,

    Sorry, but I don't get what you mean with: "...a dual opposed PPSL... its like a Dual Opposed Sealed but with one driver and mount facing in..." Could you, please, provide a sketch of that arrangement?

    As to the design of the enclosure, keep the driver plenum(s) as small as practical, and follow the same general rules you would use for a sealed box (or for a vented (bass reflex) if you decide to go that way). It may be interesting to design the box with ports you can stuff, or close.

    Regards,
     
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