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Old 11th September 2011, 03:42 PM   #161
Scott L is offline Scott L  United States
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Default 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.
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File Type: jpg ppsl and system 014.jpg (117.7 KB, 706 views)
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Old 11th September 2011, 04:03 PM   #162
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I am sorry it did not work out for you, maybe it can be salvaged.

When you say you did not follow a published design, can you expand on that. For instance, did the internal volume, size of ports etc come from a design for that particular woofer?
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Old 11th September 2011, 05:02 PM   #163
Scott L is offline Scott L  United States
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Default 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.
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Old 11th September 2011, 09:27 PM   #164
Boscoe is offline Boscoe  United Kingdom
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My efforts to design a PPSL! I don't know whether I have done it right please correct me if i'm wrong! Using two HiVi SP-10s.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

I'm not that impressed with the efficiency figures actually I might try some different drivers or I might of designed it wrong.
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Old 11th September 2011, 10:11 PM   #165
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Boscoe Is that a small slot port or no?

I hope it was something simple Scott. I have alot of hope for this design so hopefully yours works out or DJK can tell you what it was.
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Old 12th September 2011, 06:57 AM   #166
Boscoe is offline Boscoe  United Kingdom
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Quote:
Originally Posted by chrapladm View Post
Boscoe Is that a small slot port or no?

I hope it was something simple Scott. I have alot of hope for this design so hopefully yours works out or DJK can tell you what it was.
Yes two either side.
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Old 12th September 2011, 11:07 PM   #167
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Quote:
Originally Posted by Scott L View Post
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.
Measure the impedance response and compare it to the HornResp predictions. If they differ, then something went wrong with the actualization of your design.
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Old 14th September 2011, 12:19 PM   #168
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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
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Old 14th September 2011, 12:23 PM   #169
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Which 18's did you use? Pro Audio of some sort I assume. Any dimensions?

I think if I did one it would be more shape externally like your dual 15's in your avatar.
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Old 15th September 2011, 09:46 PM   #170
Scott L is offline Scott L  United States
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Default Read "YES" again

Quote:
Originally Posted by norman bates View Post
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

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.
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