A Thread for those interested in PPSL enclosures - Page 32 - diyAudio
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Old 26th July 2012, 09:53 PM   #311
badman is offline badman  United States
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To my thinking, the manifold should have some absorbtion in the back of it to both damp any manifold resonances and also absorb some of the distortion components and/or pole vent noises.

And I don't think that in a PPSL, pole vent noises are going to mean much- first they'll be suppressed because they're not facing the listener, second, if the woofers are pumping that hard, the overall SPL will be high and tend to mask those components.

Also, I tend to think that large excursions any significant amount of time are indicative of undersized subs- you need the xmax occasionally but if you're using it often enough that vent noise is a meaningful issue, time to up the cone area.
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Old 29th July 2012, 11:11 PM   #312
TG1 is offline TG1  Norway
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I'm also wondering, like LineSource, if an angled slot does have any major effects...?

Also, what is the optimum size for the slot (if there is any such thing)?

-tg
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Old 30th July 2012, 08:29 PM   #313
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Default :)

Ratio of 1:2 or 1:3 of total woofer SD has been thrown around for manifold opening...
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Old 30th July 2012, 08:34 PM   #314
TG1 is offline TG1  Norway
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Quote:
Originally Posted by TMHutson View Post
Ratio of 1:2 or 1:3 of total woofer SD has been thrown around for manifold opening...
Okay, thanks
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Old 18th August 2012, 08:50 PM   #315
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Default PPSL Enclosures

According to Nelson Pass - a ratio of 1:3 of the woofer's SD is desirable. His article on slot-loading SW is most interesting. GH
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Old 18th August 2012, 09:30 PM   #316
Djim is offline Djim  Netherlands
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Hi Gary,

Could you share the link of the article?
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Old 18th August 2012, 10:53 PM   #317
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The Slot Loaded Open Baffle Project Article By Nelson Pass
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Old 18th August 2012, 11:56 PM   #318
Djim is offline Djim  Netherlands
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Thanks Djk, 'slot loaded open baffle', that explains enough….
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Old 19th August 2012, 09:23 PM   #319
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Default Finished my PPSL

Much thanks to Dennis, I made a pair of PPSL's using his basic design customized for JBL 2226h's. I had been using the 4 drivers in the usual JBL 4508 enclosures meant for PA use. While the sound was ok, they seemed a bit slow/muddy even with EQ and were 97db efficient vs my horns at 112db. The other big factor is their size and weight was didn't work asthetically in my livingroom. As for the PPSL's- My initial impressions of the sound were similar to others in that first impressions were a lack of bass. I have not seen much discussion on how well the bass box pro plot compared to actual. While I don't have rew, I did use pink noise w/the behringer mike 3' from the box and photo'd the deq's display. Both drivers are identical in their frequency output, and there is a significant drop out at 300-500hz, and a much smaller one around 80hz. I'm able to eq these flat, but still, I can't explain the limited high requency result. I'm sure Dennis will have some insight. EQ'd, the sound is good, I'm still working on it, but it adds about 6db's more efficiency, 1/2 the weight and 1/3 the size of the orig. jbl boxes. I do wonder if the reduced harmonic distortion isn't perceived as less full/rich sounding, similar to the perception of tubes vs ss electronics.
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File Type: jpg PPSL RTA.jpg (64.3 KB, 394 views)
File Type: jpg PPSL.jpg (97.2 KB, 395 views)
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Old 20th August 2012, 12:37 AM   #320
tb46 is offline tb46  United States
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Hi pumpkin1,

I took a quick generic look at the JBL 2226H in a PPSL in Hornresp. It looks like filling the back corners in the front chamber would provide some extension at the upper end.

Regards,
Attached Images
File Type: jpg JBL_2226H_PPSL_Input.jpg (37.6 KB, 349 views)
File Type: jpg JBL_2226H_PPSL_SPL.jpg (28.1 KB, 336 views)
File Type: jpg JBL_2226H_PPSL_with_S1 equals 1_SPL.jpg (27.9 KB, 333 views)
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