15" DVC Sub complete (1 Viewer)

[Fred Seger]

I've just completed my latest sub. It uses a 15" Dayton DVC in a 6th order Bandpass(vented front box and vented rear box. The rear box is about 130L and tuned to 16 hz. The front box is 25L and tuned to 50 hz. I made the box to be used as( or at least look like) a coffee table. The outside dimensions are 50Lx20Wx16H. I have the voice coils wired in parallell for a 4 ohm load. The amp is the PE 250 watt plate amp which presents 272 watts to a 4 ohm load. It also has a 6db boost at 30hz which I plan on disabling sometime. Here is a graph of the frequency response. Sub level is first set with reciever test tones. Then I set receiver volume to 0db(reference) and ran test tones at 5 hz increments from 15 to 80. All measurements were taken from thelistening position which is about 10 feet from sub. The sub is in the middle of the wall under my projection screen. The room is 30x30x7. RS meter was used and no corrections were made to the readings.

I assume the dips at 20,40,60 are room modes. Correct?
Over all I'm pretty happy with the results. This sub replaces a 7' tall 24" sonotube with 2 shivas. The sonotube does sound better IMO, but it was over twice the size.

 

[Patrick Sun]

Well, I hope you wore ear protection when you were measuring at reference levels! You're a braver man than me.
Do a near field measurement: place the RS SPL meter very close to the dust cap of the driver, around 1" or so, don't turn up the volume too much, just enough to produce readings around 80dB. Re-do the measurements again, and plot them again. See if the dip show up again. If not, than perhaps, the 3m measurements were room modes.
I'd also suggest adding the RS SPL meter correction values for a better look at the response. Look in the other thread on the RS SPL meter for the correct values to be applied to the measurements.
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