Nondirectional & Inaudible Bass: What Frequencies?

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

Unsound: I had forgotton all about those models. Personally, i think that downloaded subs lack "attack". This probably has to do with the longer signal path to our ears as compared to a direct front radiating design and the damping of upper harmonics that typically takes place in such a design. I only find such designs suitable for use as SUB-woofers if you know what i mean. I don't think it works well for anything but the bottom octave or two at the very most. The downloaded subs in my HT system are actively crossed at 30 Hz and the downloaded subs ( as used with small two way monitors on stands ) in my bedroom system are actively crossed at 65 Hz.

As far as exciting the floor and the building structure itself, yes, you get a lot more of that. It is especially noticeable if you are on a suspended floor aka over a basement or on the second floor, etc...

Your observations about various loading conditions from installation to installation are also quite valid. There are two different approaches that one can take to this. One can allow adjustable loading via moving the box up and down via threaded spiked feet or cones. This allows one to adjust the amount of loading and vary the tuning to best accomodate individual rooms and tastes.

The other approach is to have a permanent "sound board" ( like a piano uses ) or "loading plate" built into the design. This approach maintains consistent loading characteristics due to the consistent space between the board and the driver regardless of what type of flooring ( carpet, tile, etc... ) you have underneath it.

Both are valid approaches and up to the designer and end user as to what they like best. Personally, i like the adaptability of adjustable feet but some people would prefer relying on the design expertise of a professional as they don't trust themselves to "get it right". Sean
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Sean , I think Roy Allison designed a system such as you described with a canted down firing woofer reflecting it's sound off a fixed platform some years ago.

I don't doubt that Allison did something like that as he was always playing with / taking into account room loading and gain. There have been other designs that fire the woofer upwards into a "loading plate", which achieves the same effect without causing the spider ( part of a speakers' suspension ) to sag quite as much. Obviously, it is just another variation on a somewhat common design. As such, it has trade-offs of its' own to deal with. Sean
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