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Big BLH in Bookcase?
Big BLH in Bookcase?
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Old 2nd August 2011, 12:42 PM   #31
bentoronto is online now bentoronto  Canada
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Join Date: Jan 2008
Location: Toronto and Delray Beach, FL
Big BLH in Bookcase?
Aside from the thrill of a creative camouflage solution, what are the benefits of having your upper bass handled with a horn?

If you converted it to a TL, you could be handling the lower bass too.

HiFi aspirations since 1957. Currently working on motional feedback again... the final frontier in audio
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Old 11th August 2011, 09:25 PM   #32
dhenryp is offline dhenryp  United States
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Join Date: Aug 2003
Location: Mass.
Originally Posted by GM View Post
Normally one would fold it over the mouth rim ala Peavey, but for a bass horn it could be just on the inner 'lip' and extend up/down from the edge some distance, though not sure how much since my way of dealing with it is to 'kill two birds with one stone' by making a vent screen lined with 1" fiberglass acoustic insulation.

I've decided to go back to the curved expansion and do some testing of acoustic insulation in the mouth as GM suggested. I didn't have the rigid fiberglass GM talked about but I did have some 2" acoustic foam that appears, from some searching, to be roughly equivalent to 1" Owens Corning 703 rigid fiberglass.

The first picture shows the foam pieces I used to both line the end of the mouth and a piece that covers the entire mouth opening. The second picture shows the results at the mouth. It compares the original curved path with no mouth treatment (notice the spikes at 800 and 1800 hz), the square corners version with no mouth treatment, and lastly the curved path version with the pictured mouth treatment. The last two curves seem to be roughly equivalent, with the mouth treatment a little better around 500 hz and a little worse around 1800. None of these are with any additional fiber stuffing.

I've decided to go for the curved expansion with the mouth treatment - it's actually easier since I already have all the curvy bits cut. I'm not sure I would go through the trouble if I was starting fresh. I put about half of the fiber stuffing back in. Only half because the last stuffing test showed a quite large decline in bass response. The third picture shows where the stuffing went. The fourth picture is a summary showing the response at the mouth, the driver and 6ft on axis. This is for the speaker with the mouth treatment and the fiber stuffing.

I'm pretty happy with this. Now on to building a book case around it.
Attached Images
File Type: jpg IMG_0600-1.JPG (67.5 KB, 84 views)
File Type: jpg BC mouth treatment compare.JPG (78.8 KB, 85 views)
File Type: jpg IMG_0597-1.JPG (70.3 KB, 81 views)
File Type: jpg BC Round st foam in-on summary.JPG (76.8 KB, 81 views)
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