Finished
I am finished and not very happy with the results. Granted, I did not follow any published design. Mine turned out to have a sonic signature of which I can not live with. Sort of like a thud thud thud quality. I can only speculate as to the reason(s). I think my plenum is too wide. IE the drivers are too far apart. Plus, I used 12" woofers, and I think most before me had used 15 inchers. The reason my woofer mounting boards are so far apart, is, because
I wanted the exit area to equal the SD of the drivers. Might have been a mistake. Worked on these bastards alll summer, and all that work is for naught. One pic is up close, and the other, of them finished and parked out of the way.
I am finished and not very happy with the results. Granted, I did not follow any published design. Mine turned out to have a sonic signature of which I can not live with. Sort of like a thud thud thud quality. I can only speculate as to the reason(s). I think my plenum is too wide. IE the drivers are too far apart. Plus, I used 12" woofers, and I think most before me had used 15 inchers. The reason my woofer mounting boards are so far apart, is, because
I wanted the exit area to equal the SD of the drivers. Might have been a mistake. Worked on these bastards alll summer, and all that work is for naught. One pic is up close, and the other, of them finished and parked out of the way.
Attachments
YES
Yes, the bass reflex aspect was followed to the letter. Most ppsl's you see are of a taller cabinet, a smaller plenum, use 15 inch woofers, and have rectangular ducted ports of who knows what depth at the bottom of said cabinet. It's also a shared volume. Mine were independent back enclosures.
The actual structure can be salvaged: My first thought was to simply front
mount the 12's. But further research has led to the suspicion of 12's qualifying as a decent woofer size (?) If I take and dissect the very center of the cabinet where the plenum is now, and add another thickness of 3/4" stock over the front panel,
I could barley, just barely, fit in my 15" pro woofers. I need to mention these were supposed to be for mid bass operation. 60-380 Hz. Somewhere else in the forum I read where one poster said 2x15" per side gives very effective mid-bass. (I'm using one 15 per side now, in a sealed box) It's very smooth, very musical, bit lacks the last word in an ultimate "punch" quality.
ps. another reason i built these now defunct ppsl's so squat and wide is (was)
the midrange horn now under construction is the same width.
Yes, the bass reflex aspect was followed to the letter. Most ppsl's you see are of a taller cabinet, a smaller plenum, use 15 inch woofers, and have rectangular ducted ports of who knows what depth at the bottom of said cabinet. It's also a shared volume. Mine were independent back enclosures.
The actual structure can be salvaged: My first thought was to simply front
mount the 12's. But further research has led to the suspicion of 12's qualifying as a decent woofer size (?) If I take and dissect the very center of the cabinet where the plenum is now, and add another thickness of 3/4" stock over the front panel,
I could barley, just barely, fit in my 15" pro woofers. I need to mention these were supposed to be for mid bass operation. 60-380 Hz. Somewhere else in the forum I read where one poster said 2x15" per side gives very effective mid-bass. (I'm using one 15 per side now, in a sealed box) It's very smooth, very musical, bit lacks the last word in an ultimate "punch" quality.
ps. another reason i built these now defunct ppsl's so squat and wide is (was)
the midrange horn now under construction is the same width.
Attachments
Measure the impedance response and compare it to the HornResp predictions. If they differ, then something went wrong with the actualization of your design.
scott, did you ever crunch the numbers of what those 12's would do in either a sealed or ported box ? Those magnets look very beefy for a 12" (not much low bass). The width of the plenum is fine to me. 2 x 12" = around an 18" driver.
If you list the manufactorer's qts, Fs, and Vas, we could get you some box sizes.
I think you said it was ported, to what frequency ? You did wire the drivers out of phase (the push pull), right ?
15's would be easier to play with (to me) because it is easier to find lower Fs drivers, and you have more box area, making for a shorter port (but then you deal with 2x15's worth of air through the port now).
Punch ? I got punch from dual 15's a side (running 80-500hz). Chest pressurizing bass, that came from the ppsl 18's, even with their wimpy 4.3mm xmax. Punch can come from integration, or even pleasant 2nd order distortion from a woofer.
Norman
If you list the manufactorer's qts, Fs, and Vas, we could get you some box sizes.
I think you said it was ported, to what frequency ? You did wire the drivers out of phase (the push pull), right ?
15's would be easier to play with (to me) because it is easier to find lower Fs drivers, and you have more box area, making for a shorter port (but then you deal with 2x15's worth of air through the port now).
Punch ? I got punch from dual 15's a side (running 80-500hz). Chest pressurizing bass, that came from the ppsl 18's, even with their wimpy 4.3mm xmax. Punch can come from integration, or even pleasant 2nd order distortion from a woofer.
Norman
Read "YES" again
Norman,
Which model 15's did you use dual per side ? And I saw the pic of your 2x18" ppsl's earlier in this thread. Impressive.
The back volumes are 1.8 ft^3 per driver, tuned to 50Hz. I get response way down to 36 Hz, and from what i have learned, it's because the plenum front loading of the drivers throws off the otherwise standard Thiel/Small calculations.
I should indeed try front mounting those (built like a tank) 12 inchers, just to see what they sound like in a conventional box.
To all others: note the large bump just above 200 Hz in Boscoe's simulation.
Might be something to that (?) I built my ppsl's with the object being the "absence" of box colouration, not the added presence of it. Soon as I recover from the depressive burnout of this summer project, I'll do something else with the boxes. Right now I am enjoying a single 15" (Dayton house brand pro 15's) in a sealed box. Sounds pleasant, but just dosen't punch/ or move the earth-punch me in the gut, like I am looking for. (mid bass only, as far as sub bass, I am just fine) ( and that's a different system for another time). Thanks to all, for your contributions to this on going thread.
Norman,
Which model 15's did you use dual per side ? And I saw the pic of your 2x18" ppsl's earlier in this thread. Impressive.
The back volumes are 1.8 ft^3 per driver, tuned to 50Hz. I get response way down to 36 Hz, and from what i have learned, it's because the plenum front loading of the drivers throws off the otherwise standard Thiel/Small calculations.
I should indeed try front mounting those (built like a tank) 12 inchers, just to see what they sound like in a conventional box.
To all others: note the large bump just above 200 Hz in Boscoe's simulation.
Might be something to that (?) I built my ppsl's with the object being the "absence" of box colouration, not the added presence of it. Soon as I recover from the depressive burnout of this summer project, I'll do something else with the boxes. Right now I am enjoying a single 15" (Dayton house brand pro 15's) in a sealed box. Sounds pleasant, but just dosen't punch/ or move the earth-punch me in the gut, like I am looking for. (mid bass only, as far as sub bass, I am just fine) ( and that's a different system for another time). Thanks to all, for your contributions to this on going thread.
Hi -
I'm thinking of doing a quarter wave transmission line loaded PPSL. Is there any reason the transmission line should not exit next to the drivers in the plenum? (it would be split to give one exit for each driver). This would strictly be for HT SW use below 60 hz, and am thinking of using 20hz or so tuning for the transmission line.
TIA for any feedback.
I'm thinking of doing a quarter wave transmission line loaded PPSL. Is there any reason the transmission line should not exit next to the drivers in the plenum? (it would be split to give one exit for each driver). This would strictly be for HT SW use below 60 hz, and am thinking of using 20hz or so tuning for the transmission line.
TIA for any feedback.
Hi there: TH's have one side of the driver(s) exiting into the horn mouth, so there seems to be no reason for not locating a TL port into the PPsl, althouigh others on this forum have expressed reservations, without backup data. ...regards, Michael
Hi michael,
Agree.Maybe time to test for the crackpot index of whats been argued to be exceptional compared to other good sub implementations.
Crackpot index
As soon as you confine an TL terminus close to a driver front or rear side diaphragm: It turns into a T-TQWT lookalike setup (BP-like) as for the T-QPPSL:
http://www.diyaudio.com/forums/subw...interested-ppsl-enclosures-3.html#post2563705
...where I stated to use a lower input power than was simulated.
At a third of the presented input power maximum pressure at the rear side of the drivers would be no more than 165 Pascals/=~123 dB-SPL/at ~26Hz. Nothing to worry about if using quality drivers,IMO..
b
Hi, DJK -
Hope you come back 100%+. Your input is always valued.
I am considering the quarter wavelength TL because my previous experience was that it seemed generally more neutral sounding than BR with still useful bass augmentation & not as rapid a rolloff below. but eventually, for hi quality audio, the delayed backwave started to bother me with music - I think this would be much less of a factor for HT use. If tuned for a quarter wave of 15-25 hz, could still have useful output down to as low as 8hz (with eq) where the K2 amp I plan to use with it cuts off.
Hope you come back 100%+. Your input is always valued.
I am considering the quarter wavelength TL because my previous experience was that it seemed generally more neutral sounding than BR with still useful bass augmentation & not as rapid a rolloff below. but eventually, for hi quality audio, the delayed backwave started to bother me with music - I think this would be much less of a factor for HT use. If tuned for a quarter wave of 15-25 hz, could still have useful output down to as low as 8hz (with eq) where the K2 amp I plan to use with it cuts off.
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Do you have any more pics of this build or atleast the bigger pictures showing the whole cabinet?
perhaps here is some inspiration.
Yes, those are 18's with a 12" diameter port.
It is worth it.
Norman
I'm not sure what else you want to see............
I have no pics of the build (like 6 years ago), but I could get more pics (they are next door to me). If I remember, they were 48" wide x 36" deep x 22" tall. Again if I remember, it was either 16 or 18ft3 tuned to 27hz. The drivers were not in seperate enclosures, they shared the giant box.
Actually, in the pic, I can see the mdf splitting... oh well...........
Scott, I had some cheapie eminence gamma 15's. Sealed box f3 around 80hz, like no xmax. Djk will fill you in on why yours didn't work well. Don't put too much faith in simulations. Don't give up on ppsl, but you may have to give up on that box going up to 400hz nicely. The design is a bit trickier than I thought.
Norman
I have no pics of the build (like 6 years ago), but I could get more pics (they are next door to me). If I remember, they were 48" wide x 36" deep x 22" tall. Again if I remember, it was either 16 or 18ft3 tuned to 27hz. The drivers were not in seperate enclosures, they shared the giant box.
Actually, in the pic, I can see the mdf splitting... oh well...........
Scott, I had some cheapie eminence gamma 15's. Sealed box f3 around 80hz, like no xmax. Djk will fill you in on why yours didn't work well. Don't put too much faith in simulations. Don't give up on ppsl, but you may have to give up on that box going up to 400hz nicely. The design is a bit trickier than I thought.
Norman
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