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Thank you Crossfire, I am going to keep your method just in case I need it. For now, I finally got the subs in both my rooms almost delightfully perfect. I have a Snell Sub24 which I guess I luckily placed and set up perfectly (after getting the distance correct) by luck. The low bass is to die for: It is unobtrusive in that the listener can't detect where it is-the low bass seems to be coming from each of the other 7 speakers. The sound is very smooth and clean, only appropriately present at low volumes, yet will shake the floors during the loud parts of movies. Guests are most impressed while watching normal television. Most people didn't realize that HD stations carried such quality bass.
My problem was in getting my other, much larger room to have the bass quality of my smaller room. I hope you don't mind if I get a bit lengthy in the telling of this, but after I retired, this speaker thing sort of developed into a hobby. I had two large full range bass cabinets that I had built for my dad over 30 years ago with JBL e-15s, JBL horns and crossovers. When one of the speakers went out, it took the stereo amp with it, so I decided to rebuild the system as a 7.1 with the Yamaha RXA-800, an Emotiva XPA-5 as my main amp, an evolving set of Snell speakers--ending up with Snell LCR 500 Lucasfilm THX speakers for fronts and center (with in-wall versions (800s)) for the sides and rear. Fortunately, the large old cabinets I built for my dad over 30 years ago (about 6 cubic feet internal net) were so massively braced and cross braced internally (all joints with screws and heavy contact cement) that they were perfect candidates for subs. I bought two Dayton 15" 4 OHM reference sub speakers which were supposed to go down to 19HZ (RSS390HF-4). I removed the old speakers and used a computer program (WINISD) to calculate new porting. This was supposed to, by calculation, take the usable bass down to 16HZ. I bought a Peavy 2 channel AMP (2 x 500 watts at 4 ohms) to power the subs. The results were underwhelming. My old JBLs- even though they were wide range bass speakers, run with very little power- 90 watts shared with the horns, sounded better and cleaner though with less volume and output. The solution turned out to be 3 part. First, I found that fixing the miscalculated distances that the YPAO had produced on the first measurement greatly increased the "punch". Secondly, I removed a ground loop isolator device from between the Yamaha and the sub amp which was used because of a small subwoofer hum.This removed much of the "muffledness" from the bass. I finally tracked down the source of the very low, but annoying, hum to the TV cable connection, and simply disconnected it when listening to pure music. Grounding both ends of the cable further removed about another 75%, so it is almost unnoticable when watching TV. The last step was to purchase two excellent Snell subwoofer amps (SPA750) which I found brand new on E-Bay for 1/4 of new retail price. These, I am told, are really Dayton SA1000s with possibly some modification from Snell, though the controls are identical. These special sub amps are the most controllable I have seen. They have a 3DB at 25HZ boost switch, a subsonic filter switch, and variable controls to boost or attenuate at any chosen frequency with a variable range control to vary how wide you want to go around the chosen frequency. I set the volumes at 60% of max, turned off the subsonic filter (since I am not now using a turntable), turned on the 25HZ boost, and left the selectable frequency control at zero (no boost or attenuation). When I turned it on it fully matched the Snell sub 24 (though I think it has twice the potential sound power. Bass on even vintage Jazz recordings sounds noticeably distinct, clear, and smooth. Newer, well recorded material simply blows me away with the power and clarity.
I got into this whole business of YPAO because I was hoping to improve the bass using the YPAO controls. I am now using YPAO settings and I feel no need to improve on them. My problems obviously were obviously beyond any sound analysis systems' ability to correct for. Sorry for the excessive length. I hope this is useful to someone, Bob
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