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#70676 - 12/04/04 10:07 PM Subwoofer Epiphany
mwc Offline
aficionado

Registered: 07/21/02
Posts: 958
Loc: Texas(DFW)..that country to th...
I ordered the Rives Audio Test Cd 2 and put it to use today. This cd has the built in corrected tones to compensate for the non linearity of the Radio Shack SPL meter. You can also print out a frequency chart and instruction on thier web site - pretty cool.

I found out that I had a huge 10db+ peak in the 50Hz-100Hz range. All other sub frequencies were within +/- 4db of the reference (1K) tone.

I realized from reading the Audioholics article that I had been calibrating the sub level relative to these peaks because they were dominate. This means that the sub level was set according to the level of this peak which encompassed 50Hz-80Hz-100Hz and I presume all points between those three.

I then began the pain in the ass quest to eleminate the dominate peaks. After several hours of moving 3 subs around the room and stacking and unstacking them and balancing the levels of each sub (in case you are wondering, my NHT sub has two passive slaves running off the same amp) and changing receiver settings and moving mains I finally found a combination of placement and settings that charted out to be fairly flat from 20Hz to around 16k. All frequencies are now within +/- 5db of the reference tone. I also found out that, in my room, my mains roll off sharply at 16k.

Receiver setting ended up at: All speakers set to small and crossover set to *gasp* 120. I know most will say 120 is too high because you will be able to localize the sub but as long as the sub is located near the mains this should not be a problem. I think it would be a problem if the sub is located close to the listening position.

The change is amazing. It took me a while to get used to the bass because it was the most dramatic change. It sounded like something was missing. I found out that before I made the adjusted calibration, I had gotten used to boom and thud and all the while thought it sounded good. I didn't know what I was missing. The bass now sounds smooth and tight and much more defined. Mid range seems to have improved in clarity as well. I suspect that the bass peak was causing some mid frequencies to be muddied up and I wouldn't have known the difference had I not done the calibration with the Rives disc and charted it out.

I highly recommend either getting this disc (for the adjusted RS tones) or using the compensated values when using the RS meter and another disc of your choice when charting frequency response.

Just thought I'd share this experience with everyone.
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#70677 - 12/05/04 10:29 AM Re: Subwoofer Epiphany
expatbrit Offline
veteran

Registered: 02/21/04
Posts: 148
Loc: Minnesota
I just (yesterday) did my own completely non-scientific version of this. I played with sub placement until it 'sounded better' which I equated to less peaky in the frequency domain. I then recalibrated and my sub volume control is at twice what it was before for the same SPL. My system also sounds better than it ever has. One day I will get around to a proper analysis. BTW I am crossed over at 60Hz.
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