A Thread for those interested in PPSL enclosures

[kees52]

Hi all

the build of a ppsl with 10 inch woofers I will start, I have some things read about it, but one question I have left, do I have to halve the Vas of the woofers and double the Sd?

when I calculate the box itslef as normal vented box it wil give a very long pipe, and in the slot the qts rise and Fs lowered and the woofer has already a low Fs of 19 hz, therefore will de ppsl box not very large, maybe someone has examples for hornresp to start with, I am a little curieus about this boxes and want to try it.

Maybe it is interesting to do the woofers in a samle slot without box around it and measure the thiele small parameters and use that for the calculation of the box around the slot like you all did.

Thanks.

kees

 

[Scott L]

ppsl

Yes, the Fs will be lowered once mounted in the ppsl fashion. When I checked mine I did not check the Qts values. Would be interesting to observe what happens, BUT the Vas doubles, it does NOT cut in half.

 

[kees52]

Yes, the Fs will be lowered once mounted in the ppsl fashion. When I checked mine I did not check the Qts values. Would be interesting to observe what happens, BUT the Vas doubles, it does NOT cut in half.

In had read somewhere that in a closed box two woofers do cut vas in half, thus this not true for vented and ppsl?

if the fs drops and qts is higher do I have then include this in the first vented box calculation without the slot included? because then it is better to make a slot alone and measure.

thanks

 

[Scott L]

ppsl v.2

ONLY in an Isobaric does the required Vb drop to 50%. That is beyond the scope of this thread.

YES (!!) If I had to do it all over again (which I sure will someday) I would build the slot and then measure the paralleled drivers t/s parameters as if they were one.

 

[kees52]

ONLY in an Isobaric does the required Vb drop to 50%. That is beyond the scope of this thread.

YES (!!) If I had to do it all over again (which I sure will someday) I would build the slot and then measure the paralleled drivers t/s parameters as if they were one.

then afcourse I need two weights of for example 20 grams to use on both speakers? or a closed box for both, but I think weights are better.

thanks

I go sleep, and outside snowing, it is midnight here,.

 

[ßart West-VL.]

then afcourse I need two weights of for example 20 grams to use on both speakers? or a closed box for both, but I think weights are better.

thanks

I go sleep, and outside snowing, it is midnight here,.

Yes, both cones need weights, then you ad them up. for example woofer1 + 20gr + woofer2 + 20gr = +40gr

I did the same thing recently.

 

[kees52]

Oke thanks, I go try that soon.

 

[kees52]

I have model a ppsl with the visaton wsp26 s these have a fs of 19 hz and a vas of 220 and a sd of 330, pretty big for a 10 inch.

The model trough bassbox pro 6 rae interesting if i do only closed box with slot, and the sound of a closed box system is good, my question is how low go the speaker when in a slot facing together, because it is already 19 hz how much lower it wil go, I have afcourse to test it but maybe someone has a idea.

I go then make a closed PPSL box with the 10 inchers, so it will have best impuls behavior and it go loud enough, the dipoles in my home is a problem because of my space here, a tapped horn is also possible but I do not now his sound quality, but people here have and I like to share.

I was always a horn fan, still I am, a tapped horn with a fostex horn will I think sound wel on tube amps.

But first these, I will try them all, the dipole do good, ver nice open sound, maybe the closed ppsl has a more closed character of sound.

 

[anubisgrau]

what will be upper range you gonna hit with it?

 

[kees52]

what will be upper range you gonna hit with it?

You mean where I go to mid bass? about 100 Hz, I talk then about the PPSL box.

the mid bas is open baffle 93 dB 2.83 volts from 90 hz to 20 khz.

I did read this, the plenum is a low pass filter, depth is important.

By mounting in a plenum several things change. The spacing becomes much tighter so the cancellation will work at higher frequencies, and a cavity is formed.

The cavity does several things, in no particular order:

The size, especially the depth, acts like a low pass filter. This can reduce 3rd harmonic distortion products near the top end of the passband, the effect is small, but audible. The cavity sizes I use have to be crossed in the 150hz~250hz region. It gives a slope of roughly 12dB/oct that must be taken into consideration in the design of the crossover.

 

[OscarS]

How would something like this fair for a PPSL tapped horn?




Thinking about putting a pair of Cerwin-Vega Stroker 12s in a tapped horn.

 

[kees52]

A tapped horn has already a mass load on the speaker and go very low, i don,t think it give you extra advantage with a plenum in it.

 

[epa]

How would something like this fair for a PPSL tapped horn?




Thinking about putting a pair of Cerwin-Vega Stroker 12s in a tapped horn.

when our the cnc router arives (6 weeks or so)
then were gona bild this
we are also going to flip one driver to see what hapens.

 

[kees52]

it looks like a slot loaded dual tapped horn, interesting I am curieus about its capabillitys, nice professional look also, well drawn but big? and for PA?.

I have some question need the plenum be open on both sides? I see I can see trough the plenum with a PPSL.

I now now how to design, just simulate a normal vented box and make the advised volume greater with the total cm2 of the plenum, so a box of 100 liter with a plenum of 5 liter will give total of 105 liters.

Only, the plunem makes that the FS drops, and so I have to measure the parameters of the two spekaers first in the plenum alone then calculate the total vented box around it, I did see the plenum is in de middle of the box but I think is not so critical.

the plenum has only big enough to fit the speakers?

now I have enough info for trying to make with box pro.

thanks

 

[epa]

plenum only open to the frontside.
i'm not sure why the fs should drop.
best is to simulate it in hr,it is pretty acurate.
the plenum needs to be half of the total sd for pa speakers.
and yes you wil need the driver to sqeeze trough it.

 

[OscarS]

A tapped horn has already a mass load on the speaker and go very low, i don,t think it give you extra advantage with a plenum in it.

Going "lower" wasn't an objective, anyone who has modeled tapped horns can play with the line length to get a lower F3---I was thinking about incorporating the PPSL plenum in order to hopefully drop the distortion levels on a speaker that has no anti-distortion mechanism what so ever.

 

[kees52]

@epa

You are right, with tight you mean the speakers has to be build in without opening the box, just enough to squeeze them trough the plenum?

I have visaton 10 inches with xmax 12 mm and fs of 19 hz, that the fs drops have I from the ripole/dipole idea from linkwitz now I think the ripole drops fs because the frond and the back of the woofer cone will be mass loaded, the normal dipole only loaded on one side of the cone.

Have you some example how to use hornresp for it? do it only simulate the plenum s1, s2 and s3 and s4? and the box itselfs and the pipe length is lpt etc.

I had not good look to the plenum so I tought it was open it was not.

@oscar well try it, I can not say what it will do, sound is very difficult to predict, I was suprised by that and how much but tapped horns has already more spl watt and so lower distortion
an good woofer with heavy cone and motor and big xmax will already be low distortion when listen normally, for PA yes it give more but still low compare to normal pa systems without horns.

thanks all

 

[weltersys]

I was thinking about incorporating the PPSL plenum in order to hopefully drop the distortion levels on a speaker that has no anti-distortion mechanism what so ever.

Oscar,

DSL's TH-812 uses an in-line PP loading that probably would work better than the plenum you suggested.
Even if it did not work better, it would be a lot easier to build.

 

[epa]

maybe this helps

just an example

 

[kees52]

I have the wsp 26s woofers I did want to build this box for home theatre, but always I get to long pipes, because the woofers has low FS of 19 hz, but do the slot trow down the speaker fs and rise the qts yes or no, because some people way it stays the same, I have then need to measure in a slot alone to see what happens, or we make a small slot facing the speakers like in a ripole and look what happens.

the thiele small of this speakers.

maybe you can try them for me in HR, thanks, nut the box get really big, I do use basbox pro to test a normal vented box, and it go low but so long a pipe..

Rated power 110 Watt
Maximum power 140 Watt
Nominal impedance Z 8 Ohm
Frequency response fc - 7000 Hz
Mean sound pressure level 91 dB (1 W/1 m)
Excursion limit 22 mm
Resonance frequency fs 19 Hz
Magnetic induction 1 Tesla
Magnetic flux 1250 µ Weber
Height of front pole-plate 8 mm
Voice coil diameter 5 cm
Height of winding 1,45 cm
Cutout diameter 23,3 cm
Net weight 2,5 kg
D.C. resistance Rdc 5,7 Ohm
Mechanical Q factor Qms 3,19
Electrical Q factor Qes 0,38
Total Q factor Qts 0,34
Equivalent volume Vas 230 l
Effective piston area Sd 330 cm2
Dynamically moved mass Mms 42 g
Force factor Bxl 8,7 T · m
Inductance of the voice coil L 1,2 mH