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Discussion Starter · #1 · (Edited)
I don't own a BFD yet, but I setup Room EQ Wizard to measure the frequency response of my DIY subwoofer. I got the absolutely horrible response graph below (purple line). It's a relatively large (4.5 ft^3) ported sub with a 12" Dayton DVC woofer, so I expected much better low bass.




As a test, I put the sub in my bathroom and I got the curve below. MUCH FLATTER!!!




So I guess my room is sucking all the bass? Does anyone have any suggestions? Is this something that BFD could help solve, or am I screwed? Here are some details of my setup:

- My TV room is 23x13 (300 SQ feet) but it opens into the dining room/kitchen area, which is about 550 sq feet (so a total of 850). The ceilings are 9 feet.

- I'm using a Nady Audio SPL which looks to be a clone of an older Radio Shack unit, but I'm not sure. I used the old RS correction curve for these graphs, figuring it might be appropriate. But the massive impact the room has is much bigger than the corrections anyway.

Thanks for any thoughts.
 

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So I guess my room is sucking all the bass?
The room is a fair size, and it's only a 12" sub. Corners have quite a positive effect, providing room gain at lower frequencies. Have you tried moving the sub into different positions?

Is this something that BFD could help solve,
Nope, gain is a no-no with a BFD, particularily the amount you need.

I'm using a Nady Audio SPL which looks to be a clone of an older Radio Shack unit, but I'm not sure. I used the old RS correction curve for these graphs, figuring it might be appropriate
I sure wouldn't count on that. There are three versions of the RS meter, each with it's own set of cal files. It would be nice to retest with a known meter/cal file setup. :).

note:when you post graphs, try and stick with a vertical scale of 45dB-105dB and horizontal of 20Hz to 200Hz. That way we are all comparing the same graphs ;)

brucek
 
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Discussion Starter · #3 ·
The room is a fair size, and it's only a 12" sub.
Hmm. But would would a larger sub (or multiple subs) really boost the lower frequencies, without raising the frequencies in the 60-90 range as well?

Corners have quite a positive effect, providing room gain at lower frequencies. Have you tried moving the sub into different positions?
The only corner I have available is on the back wall, which I was hoping not to do, but I'll give it a shot now and report back.

note:when you post graphs, try and stick with a vertical scale of 45dB-105dB and horizontal of 20Hz to 200Hz. That way we are all comparing the same graphs ;)
Oh ****, yeah I think I did read that somewhere. Will do next time.

Thanks for the reply!
 

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Hmm. But would would a larger sub (or multiple subs) really boost the lower frequencies, without raising the frequencies in the 60-90 range as well?
I believe larger cone diameter drivers (15" & 18") can more easily produce and extend to lower frequencies (in the correct enclosure). Multiple subs only add headroom.

brucek
 

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Before you give on that low bass try other listening positions (if at all possible).
Moving your chair or sofa backwards or forwards can effect the bass response dramatically.

Did you have your SPL meter near your normal ear level when seated? It matters in my room and might also in yours.

For the small amount of money involved it might be worth investing in another SPL meter to confirm you have the correct compensation. Just because the case looks like an RS meter doesn't mean it has exactly the same roll-off.

The lower bass response curve measured by REW (or any other software) depends critically on the roll-off curve of the meter itself. If you haven't matched the meter with the correct compensation curve you can't say for sure that the meter is reading correctly. Your missing bass could just be a figment of your meter's imagination. Or, it might just be perfectly compensated and your bass really is rolling off early.

The nearer you are to your sub the better as far as bass levels are concerned. If moving your listening chair backwards or forwards doesn't do it for you then the option remains to move the sub physically nearer your chair.

REW is so quick to take tests that you can try half a dozen positions in a few minutes. Think flexibly about your seating position and your sub's position to see if the curve flattens out to your advantage. You don't have to move your chair yet. Just keep moving the SPL meter a few inches then test and retest until you find the best spot.
 
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Discussion Starter · #7 ·
Thanks guys.

I've now got the sub in the corner, and I have the SPL at ear level in the seating position.

Due to the room layout, moving the couch isn't really an option. But I'm getting a much better response now. This is the response for the sub and mains together.

The bad news is the big dip from 106 - 120 Hz. This is definitely not the SPL because I can hear it when I do manual tones. And it happens even if I cross low (or turn off the sub) so it's not a crossover or phase problem.

I realize the SPL is an unknown and could be way off, so I'm not assuming too much here. But I'm guessing these big dips are unlikely to be SPL errors.
 

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Many people prefer the sub a bit higher than their mains. Try turning up the subwoofer amplifier a bit and see how it graphs and see how you like the sound.

The response is definitely better - I'm sure it sounds better. Dips like the one at 110Hz sometimes are caused by simple things like a particular door open or closed in the ajoining room etc. You may have to live with it. :)

brucek
 

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Interesting that there should be troughs at two doublings of frequency.

~27Hz, ~54 Hz and ~110Hz.

Yet Room Mode Calculator shows no obvious correlation between these troughs and the given room dimensions.
 

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Yet Room Mode Calculator shows no obvious correlation between these troughs and the given room dimensions.
I feel when you're in a main floor of a house with lots of openings and doors and hallways etc, it's really a crapshoot. The calculators work great in a closed dedicated theater room, but in a living room - not so much.... :)

brucek
 

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The dip at ~100Hz is a boundary cancellation between the mic and the floor. If you change the height of your measurement, you're going to see this dip move up and down with frequency (higher up = lower in frequency and vice versa).

The reason you don't hear these huge dips is because the program is measuring the steady state response of the room, while your ears are hearing the transient state. In other words, you are hearing the full sound for the few ms before it cancels itself out.
 
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