Sub output: Is it the woofer size or the rated RMS

Its not your insults I mind ; its your stupidity. You obviously have no idea what you are talking about. I suppose you never heard of "speed" in a sub woofer. If all you are interested in is making noise then the HT set up you seem to favor is fine. For those interested in serious music reproduction other considerations come into play. Oddly enough, my motivation is exactly what you profess yours to be, the prevent the clueless from misleading the unwary. My two REL Stadium subs use one 10" Volt driver each and cost $3000 each. I suppose that is your idea of cheap. You appear to be one of those who thinks that because they have spent a considerable amount of money on their system they have some how acquired knowledge and authority. Making wild and unsupported statements is hardly the mark of knowledge.

I for one believe that a fast sub is not reproducing deep bass. The very thing that makes deep bass deep is the long wavelength. I am not saying a small sub can't make deep bass. It just takes much more power and further cone movement than a large sub. The further cone movement negates the quickness of the small sub because a small sub must move in and out so much further than a large woofer, it is just as slow.

I'm not an expert in this area, but I believe that what creates the subjective impression of "fast bass" is simply the ability to accurately follow the input waveform, without harmonic or intermodulation distortion, and perhaps most importantly the ability to stop moving quickly when the musical note stops.

Increased driver size obviously will produce more volume at lower frequencies than a smaller driver, everything else being equal. Or, as Rwwear points out, the smaller driver will have the disadvantage of having to move further to produce a similar output. On the other hand, as I indicated in my previous post, producing a larger cone that will be as accurate as a smaller cone within their respective ranges of motion is more expensive. Everything else being equal, a larger cone will have to be stiffer to avoid flexing (what I believe is called "cone breakup"), cone resonances, and other contributors to non-linearity and distortion. A stiffer cone, everything else being equal, will be heavier, have greater inertia, and be less able to stop abruptly. Implementing a better combination of stiffness and lightness will tend to require better and more expensive materials.

As Mapman said, "it's the quality of the driver and soundness of the overall design that matters most." And producing a larger driver of similar quality to a smaller driver simply costs more, particularly if the design doesn't require the smaller driver to provide the volume or bass depth of the larger driver. I would not say that "a fast sub is not reproducing deep bass," just that it can't reproduce bass quite AS deep and/or loud as a larger driver or a driver of the same size but greater excursion.

Regards,
-- Al

Almarg outlined the issues well I would say.

Sorry to have gotten irritated, I was upset at the idea that many manufactures are only concerned with marketing. I have known many , beginning with Sol Marantz and Stu Hegaman and by and large they were driven by considerations other than the maximum amount of money they could make. Of course there are those like Bose who are all marketing but they are rare. Most designers are trying to produce the best they can at a price they can sell their product for. The optimum size of woofers is a subject that has been debated for years and will not be settled in my lifetime and I respect anyone else's opinion. What I do not respect is unsubstantiated attacks on the motivation of people I like and , in many cases, admire. It has often been said that the way to make a small fortune in HI End audio is to start with a large fortune , sometimes good products are rewarded but often they are not. The lack of marketing skills has been far more prevalent in hi fi than an excess of them. The point I am trying to maintain is that it is possible to disagree about equipment without impugning the motives of those who make products we ourselves do not like. I have never succumbed to the charms of Magnapans but I do not think those that do are somehow defective in some respect. It would be boring in the extreme if everyone liked the same things. The older I get the more I realize that everyone hears things in a different way and what suits one will not work for another.