High Efficiency Speaker Asylum

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RE: Subs in the ceiling or under the floor

Posted by Davin Carter on February 19, 2012 at 11:35:13:
I use a pair of 18" woofers mounted at the top of the ceiling and vented into the attic. Performance is rather good.
This is mostly due to WAF issues. I though of making a nice 8 cu ft coffee table, but really the infinite baffle works even better.

I have woofers that have a fairly low fs, but also low Qts, also 97 db efficiency. They were really designed for a vented enclosure I start to get a 6 db/oct rolloff below 80 HZ. My low pass crossover just starts with a first order starting at 20 HZ to avoid the rolloff. I also have a 2nd order low pass at 150HZ. I run horns above 150hz.

If you vent into the ceiling, you may want to think about fire protection. If something burns through the woofer cones, you do not want to light up the attic. I faced the attic side with drywall far enough that a fire would not spread easily.

I thought about starting a horn about 6 feet into the attic and letting the top room corners continue as the horn. I just am not just not happy with a possible quick rolloff below 30 hz. Also, I would need to get a delaying device if I went with a horn for the subwoofer. Plus I am happy enough with my current configuration.

Anyway, I would recommend infinite baffle venting either into a floor or attic.