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In Reply to: RE: Dipole Subwoofers posted by stryke23x on July 11, 2016 at 17:54:08
"Tomorrow I will be constructing a very simple H baffle and U baffle to take some measurements of. It looks like a single coil and resistor can be used to get quite flat response from below 30hz on up to 400hz or so. I will have results soon."
What kind of efficiency do expect to get with that configuration?
Dave
Follow Ups:
Hi Dave,
Open baffles in general are very inefficient due to the significant rolloff caused by the baffle. Adding the H frame or U frame does help increase the low end efficiency but can only do so much.
A single Dipole18 is about 93dB 1W. With the dual 8ohm coils in parallel for 4ohm, 2.83V input gives a max efficiency of about 96.5dB way up at 400hz. Modelling a 24" x 24" flat baffle shows a drop of of about 16dB from there to 30hz giving 80.5dB 2.83V at that point. The U baffle or H frame should get back somewhere between 6-10dB efficiency at 30hz which is quite good. It also increases the max output by the same amount. The OB is capable of about 98dB at 30hz, again with the U or H frame giving 6-10dB more maximum output. This requires only 20V input to do so, about 100W. Proper placement in the room will get back several dB more output. The plan is to measure the OB, U, and H all outside. Then bring into our well treated 13' x 21' room with 9ft ceilings and get some measurements at the listening position as well.
That is a lot better than I thought it would be. Will you be posting your results?
Dave
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