A Thread for those interested in PPSL enclosures - Page 8 - diyAudio
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Old 10th May 2011, 11:36 AM   #71
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Quote:
Originally Posted by djk View Post
"just a quick question - did you ever try building a PPSL where the vent exited through the plenum? I'm thinking a shelf port to the rear of the enclosure that vents into the back of the plenum. "

No, it doesn't seem like a good idea to me.

I have made the plenum with ports above and below the opening for the woofers. I made a dual 18 tuned to 28hz this way, and a dual 12 tuned to about 40hz. I am designing a dual 15 tuned to about 28hz this way too.
One of my friends built a double-TH - the topology was basically identical to a PPSL with a vent through the plenum (because he used a small mouth for his design), but of course one driver wasn't reversed. It actually sounded pretty good, especially considering that it was built using 6.5" long-throw drivers....
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Old 10th May 2011, 09:07 PM   #72
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I am concerned about the midrange performance, most of my designs are crossed at 150hz or higher.
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Old 15th May 2011, 07:14 PM   #73
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Hmm... the PPSLTH above makes me wonder about doing a PPSL with TL. Could do a single TL instead of the slot ports or two separate TL like he does in his TH. Interesting.
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Old 15th May 2011, 07:23 PM   #74
Djim is offline Djim  Netherlands
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Hi Mashaffer, the problem with the PPSL-TH is that you want equal distribution of the sound pressure throughout the whole bandpass between the 2 paths. Thatís the main reason why Iím still not satisfied with the end results so far. For the combination of PPSL-TL, I would go for the plenum (cavity) idea and use just one path.
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Old 22nd May 2011, 03:10 PM   #75
Scott L is offline Scott L  United States
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Default the horns w/ PPSL subs

Quote:
Originally Posted by hawkson View Post
Cool
What kind of horn's did Les have?
Do you have a build thread of the 18" PPSL that you built? What are the dimensions? What is the port tuned to?
This is only the answer to part 1.
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Old 22nd May 2011, 11:33 PM   #76
djk is offline djk
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"Hmm... the PPSLTH above makes me wonder about doing a PPSL with TL. Could do a single TL instead of the slot ports or two separate TL like he does in his TH. Interesting."

I did something like this with a pair of 8s around 1985 or so. It was kind of a cross between a TH and a TL. In retrospect the cross-section of the line was too big for the 8s, but it worked well anyway. The main box was about 12x12x48H with the drivers in opposite sides of the bottom and the cabinet spaced off the floor about 3".

"Do you have a build thread of the 18" PPSL that you built? What are the dimensions? What is the port tuned to?"

That's totally dependent on the T/S parameters of your drivers. If you look at post #56, Norman used about 8 cu ft per driver (net) tuned to 28hz.

I built some for a dance club that were a 3 foot cube tuned to 28hz. They were using a subharmonic synthesizer and ruined a few sets of drivers, there were no drivers with a large x-max at that time. I re-tuned for 40hz with our 8mm x-max drivers, removed the subharmonic synthesizer, and stopped having problems.

Another set were used for a live band, they were tuned for 38hz and were about 30Wx24Dx39H. The design was 6th order vented, and the 20hz filter in a Rane AC23 was changed to the 38hz Q=2 filter required by this design.
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Old 24th May 2011, 02:34 PM   #77
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What drivers are good for PPSL designs.

I have several extra woofers sitting around

Like...
TD12S 12" woofers
TC2000 15" subwoofers.

I already have an IB array, Sealed LMS5400s and Im building JBL 2226 Mid-bass horns (XOed with the IWATA-300/BMS 4590) but I would like to plan for a PPSL build and Im hoping my unused drivers could work.

I would like to see a 40Hz to 200Hz design with the TD12S 12" woofer.

Thanks for any advice.
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Old 24th May 2011, 07:24 PM   #78
tb46 is offline tb46  United States
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Hi doug20,

Maybe it would help to think about PPSL more as a driver mounting method than a destinct type of enclosure. You can use the PPSL plenum mounting method with any type of enclosure.

Plug the T/S values for your drivers (e.g.: the TD12S) into Hornresp, and take a look at what you can model.

Regards,
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Old 26th May 2011, 01:05 AM   #79
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djk, ever tried a slot shaped like this

(one side cutout to show detail)
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Old 26th May 2011, 01:28 AM   #80
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"The other tip is to triangulate the back corners of the plenum."

I have also installed DC 703 resin-coated fiberglass in the back corners.
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