A Thread for those interested in PPSL enclosures

[hawkson]

In case someone doesn't know what DJK is talking about(I didn't),
this explains the different types of subs

[LarryMcConville]

I'm going to Google 'PPSL djk' as suggested; I would like to experiment with a pair of B&C 21SW152. I'll model both sealed and vented implementations.

Larry

[hawkson]

Please update us on your models. i am interested in 18 inch drivers.

[Antripodean]

Originally Posted by djk

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).

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]

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.

[tb46]

Hi djk,

When I use the automatic alignment feature in Boxplot the isobarik configuration ends up 6dB down, and at 1/4 the volume.

Regards,

[hawkson]

Originally Posted by djk

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.

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

[bjorno]

..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??

HI,My :

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 ..

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

[tb46]

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,

[Djim]

Originally Posted by tb46

keep the driver plenum(s) as small as practical

Oliver, your statement suggests there is no relation between (minimum) opening size versus Response.