Nondirectional & Inaudible Bass: What Frequencies?

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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Sean, I believe Dunlavy had models with both up firing and down firing woofers.

You might be right. I think that the first commercially available "loaded" woofer system was the Janus made by Jan Marovskis. That is, as far as i can remember.

Design Acoustics, a division of Audio Technica, also did this on some of their models. These were probably the most commercially succesful down-firing or "loaded" speakers that i recall. I personally think that DA took this approach primarily for space saving reasons, but they really weren't bad sounding speakers for the price and era. Sean
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