Dual 18" sub design, Looking for suggestions / improvements

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#41
Theoretically this process should work from in-room vented subwoofer measurements using REW, but I've yet to try it:

1. Block the vents, place mic 1cm away from driver's dust cap, do a sine-sweep measurement, call that measurement A.

2. 1M from driver (or your chosen measuring point) with the mic equidistant from the driver and vents, do another sine-sweep measurement, call that measurement B.

3. Unblock the vents, do another sine-sweep measurement, call that C.

4. Using the "All SPL" view in REW, subtract A from B, that will give you the transfer function affecting the measurement in step 2. Call this measurement D

5. Using the "All SPL" view in REW, subtract D from C - this should give you the equivalent close-miked response of the vented subwoofer, which should almost the same as anechoic and suitable for comparison against 2PI sims in Hornresp or otherwise.
 
#42
weltersys said:
To eliminate the room from the tests I did last night required putting the mic against the cabinet face, which still resulting in as much as 4 dB deviation.
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Wow!
weltersys said:
With the mic a meter away from the speaker, responses looked like 20 dB mountain ranges, small rooms (being small relative to a 38' long 30 Hz wave) are terrible as far as point to point response linearity- move your mic another couple feet and your +14 dB at 55 Hz may turn into a -14 dB hole.
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Point taken. for a portable speaker, an analysis in a room is mostly useless.
weltersys said:
After several minutes with pink noise on at a moderate level during the indoor tests, I started feeling a bit queasy. The sub's actual response is around -10 dB at 30 Hz, but putting the mic where I was seated found it happened to be +10 at 30 Hz in that particular position...
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Again, that's amazing. The room can have more effect than the speaker itself on what one hears.
weltersys said:
One thing you will find when you start gigging is the reduced stage to ceiling height compared to the rest of the room can make the bass sound completely different on stage than in the house.
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That's a whole can of worms I haven't touched yet. I have little to no control over what the sound guy does. If it's someone who knows what they're doing and puts bass in his mixes, I can lower the volume substantially and use my box as a near field monitor as much as it will allow. But in typical bar gigs where the bass is non-existent, I will have to walk out front and try to blend. In the best case, There will be small amounts of stage noise (isolated guitars and drums, or electronics) and I can just use my IEM's. That doesn't happen often, unfortunately.
 
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