Nondirectional & Inaudible Bass: What Frequencies?

I agree Unsound, Viridian did bring up a VERY good point. The fact that the mass majority of powered subs that are out there are not properly calibrated in terms of crossover frequency does not help any either. Most all subs are actually crossing over at a higher frequency than what the controls state. Top that off with most of them having a less than "ultra-steep" crossover slope and you have a LOT of "blending" between the sub and the woofers. Too much in most cases. That is why so many people have a hard time trying to get a good blend between the mains and the subs.

As i mentioned earlier though, downloading will help to reduce the amount of apparent upper bass output. This has to do with the "tuning" of the space between the driver / baffle board and the flooring underneath it. This type of system has a narrow band of efficiency with everything else acoustically sloping off outside of that band. By playing with the distance of the driver from the floor, one can alter the loading / coupling of the driver via the pressure front and "fine tune" the bandpass that you want highlighted most. This also changes the "Q" of the speaker system, which will affect the low frequency extension, output and transient response of the sub. If you are looking for anything BUT the lowest bass though, downloaded designs do not have as much apparent "attack" and / or defintion due to the lack of upper harmonic structure. As such, they do not work well when being used as a woofer and are best suited for sub-woofer only use. Sean
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Sean, some of Dunlavy's more recent works seem to support your point.

See, if Dunlavy would have just listened to me years ago, they might still be in business today : )

Honestly though, i don't know what you are refering to, but i'd love to see it if you can find a link to it. Sean
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Sean, I'm sure your aware of the downloaded woofers on Dunlavy's Athenas, Catenas, SC IIIA. John Dunlavy told me as a string bass player he liked the results of this approach, but he somewhat avoided the issue when I asked him if it was as accurate as his direct firing (to listener) designs. I have to admit I'm a little dubious of this approach as everyones flooring is different and so would the reflected sound be. Also I suppose that it would have a greater chance of exiciting the the rest of the room and surrounding rooms structure and would probably be limited to ground floor rooms. I really don't think I'd like to live below someone with such an arrangement. Further more as a believer in time coherent designs (I do try to keep an open mind about this, though) it would appear to be a contradiction in that regard. I suspect that it might really work best with omnidirectional "satelite" designs on a somewhat detached ground floor.

In my listening room 65hz seems to be a point where I can no longer notice it's origin.80hz is very locatable.Wish i knew why.A single sub exites the room at certain locations and not others.Two subs in opposite corners exite the room at different locations,mostly "spreading" the sound out more.While putting two in one corner only increases bass out put in the same location as the first.I have seen my subs peaking front to back at freq below 18hz and for what ever the reason the room never reenforces it.No matter where i put the sub.Confused?so are the pro's