Rudy81, it sounds like you didnt change the plenum itself in your further trials, am i right? You just added some spacers under one of the woofers? If so, your result is no surprise. The driver spacing alone will not change much. The plenum size and shape will dominte the response. If you dont change the plenum geometry itself, there will of course be no significant change.
hi.
first escuse me for my english and greeting from france.
i have some eminence kilomax pro18a in stock and i'm looking for a loud design for them.
do you think two of them fits good in a T-QPPSL as show in post 21 :
first escuse me for my english and greeting from france.
i have some eminence kilomax pro18a in stock and i'm looking for a loud design for them.
do you think two of them fits good in a T-QPPSL as show in post 21 :
FYI:
A T-QPPSL to be played at lower input powers:
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I am designing my first complete speaker system using 4 10" woofers, 2 3" full range and 2 2.5" full range for each side of stereo. Should I use PPSL for the woofers if I cross at 500 hz or just PP without the narrow slot? The woofers are a wide range that do well up to 500 but only have 4 mm xmax so are not subwoofers.
*Impedance: 8 ohms*Frequency range: 34-3,000 Hz *Fs: 33 Hz *SPL: 93.15 dB 1W/1m *Qts: 0.47 I would appreciate any help.
*Impedance: 8 ohms*Frequency range: 34-3,000 Hz *Fs: 33 Hz *SPL: 93.15 dB 1W/1m *Qts: 0.47 I would appreciate any help.
I think I have found a solution for my 18's. If I run PPSL... slot width is no issue, is what I gathered? The woofers are probably going to force a width of 8" or more anyway but, just wondering, thanks in advance.
There will be an increase in upper bass caused by the plenum (slot), followed by a drop in response, a deep cancellation that won't respond well to EQ, limiting the upper response, not an "issue" unless you plan to cross over in that range.
See #823 for a bit more info.
Post #823 was an actual measurement, though it can be modeled in Hornresp. Posts 779 and later have posted sim input screens and discussion in this thread.
The model is of a bass/reflex and horn, the "horn" being the slot/plenum.
Using ATC and separate horn sections, even the cross sectional volumes the drivers occupy (or don't) in the plenum can be accounted for.
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HERE IS THE SECRET TO HOW WIDE THE WIDTH (from djk, r.i.p)
The slot width needs to be as wide as 1/4 length of the first harmonic above where you want to run.
So, say you want to go up to 150hz.
The slot should be 1/4 wavelength of 300hz, or almost a foot wide.
You don't want to not run the slot too large either, there will be a resonance from parallel walls.
I had a standing wave in my 4x12" push pull slot (top to bottom), maybe 250hz.
I should have run 2 boxes of ppsl 12's.
The slot width needs to be as wide as 1/4 length of the first harmonic above where you want to run.
So, say you want to go up to 150hz.
The slot should be 1/4 wavelength of 300hz, or almost a foot wide.
You don't want to not run the slot too large either, there will be a resonance from parallel walls.
I had a standing wave in my 4x12" push pull slot (top to bottom), maybe 250hz.
I should have run 2 boxes of ppsl 12's.
Attachments
Would it have spoiled some great celestial plan to have mentioned the full form of PPSL?
Push Pull Slot Loading
Push Pull Slot Loading
Hello, relatively new member on diyaudio. only been reading material on here for a while tho.
I cant seem to find any of DJK's [bless him] plans posted anywhere these days. does someone have an archive of them somewhere?
Specifically his ppsl sub work. Thanks
I cant seem to find any of DJK's [bless him] plans posted anywhere these days. does someone have an archive of them somewhere?
Specifically his ppsl sub work. Thanks
DJK's plans basically were all standard bass reflex, though most used large slot ports.
He simply added the volume the speaker plenum slot occupies to a standard BR cabinet, disregarding the upper range boost and dip the push pull slot creates.
He simply added the volume the speaker plenum slot occupies to a standard BR cabinet, disregarding the upper range boost and dip the push pull slot creates.
It seems ive been given more homework. Thanks. I just spent a good while reading posts there, fascinating stuff.
This is really interesting actually. It always seems so complicated but when you explain it like a BR its not that complex.
Thank you both. Still a relative beginner trying to wade my way through an ocean of text on the internet.
Just a clarifying question on this technique. are you saying that you can include the plenum volume as if it was inside the BR chamber, and then model it as a normal dual BR in something like hornresp or WinISD?
PPSL basically is a ported box, but it cancels harmonic distortion.
Careful on the design above, very much a PA design, very load, very heavy, I prefer to tune near 27hz for my music/tastes.
The eminence kappa prolf2 driver is 35hz Fs with a qts of .3
A butterworth 4th order ported box would would hardly qualify as a subwoofer to me.
His 6th order ppsl boosted works well with a qts .312 driver.
You basically tune the driver to Fs (which would be around natural F9), then add 6db of boost (he used a high pass filter with a Q of 2, so it had a 6db boost at tuning frequency and acted like a subsonic filter below that).
I've made his ppsl boosted subs with a 2x12, 2x18, and lastly a 4x12 with excellent results (to me, lol).
Careful on the design above, very much a PA design, very load, very heavy, I prefer to tune near 27hz for my music/tastes.
The eminence kappa prolf2 driver is 35hz Fs with a qts of .3
A butterworth 4th order ported box would would hardly qualify as a subwoofer to me.
His 6th order ppsl boosted works well with a qts .312 driver.
You basically tune the driver to Fs (which would be around natural F9), then add 6db of boost (he used a high pass filter with a Q of 2, so it had a 6db boost at tuning frequency and acted like a subsonic filter below that).
I've made his ppsl boosted subs with a 2x12, 2x18, and lastly a 4x12 with excellent results (to me, lol).
The plenum volume reduces the BR chamber volume.
In WinISD you don't include the plenum (or bass reflex port, or driver) volume in the BR chamber volume.
With Hornresp, you can model the effect the plenum has on the upper response.
Post 779 has an example of the plenum (and a "too high" Fb)...
As Norman pointed out, most of DJK's PPSL designs were for PA, where a 35Hz Fb (box tuning) was a good compromise between low frequency response and efficiency.
https://audioroundtable.com/PiSpeakers/messages/19880.html
https://hometheaterhifi.com/reviews...reisel-dxd-12012-dual-12-push-pull-subwoofer/
Push pull = check the pictures.
Slot loaded = both drivers are physically very close and protected, mounted in a slot.
You are right, I mis-typed that a ppsl is ported.
PPSL does not have to be ported, it can be sealed, ported, transmission line, open baffle, whatever.
I've wanted to build a big sealed one not requiring any eq.......
https://hometheaterhifi.com/reviews...reisel-dxd-12012-dual-12-push-pull-subwoofer/
Push pull = check the pictures.
Slot loaded = both drivers are physically very close and protected, mounted in a slot.
You are right, I mis-typed that a ppsl is ported.
PPSL does not have to be ported, it can be sealed, ported, transmission line, open baffle, whatever.
I've wanted to build a big sealed one not requiring any eq.......
http://www.diyaudio.com/forums/subwoofers/223960-bench-style-cabinet-subwoofer-2x15-closed.html
Yep, I don'regret making a very large PPSL sub. 2X15" woofers, About 235 liters per driver. Plenum's backside stuffed with pillows. The problem is the small HT room's vertical mode.
'
Yep, I don'regret making a very large PPSL sub. 2X15" woofers, About 235 liters per driver. Plenum's backside stuffed with pillows. The problem is the small HT room's vertical mode.
'
Hi, I was talking about the “harmonic distortion cancelation” I suppose you are referring to the mechanical vibrations of the enclosure being reduced?
This is my prototype, it is sealed. There will be a top and bottom baffle, and damping material in slot, one day.
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