Originally Posted by Moggie
I'm shaking my head thinking "wait to you hear what you've got".
I hear you - I'm sure you can speak to that better than I can. I've never heard an IB yet - But from what I understand it is a different sound that most are used to due to the lack of distortion and because of the lack of distortion some say they do not sound as loud to some people as a conventional sub.
I hope that you are right and I have no desire to upgrade - 4 18's is probably considered excessive by many, but this is the way I look at it. - I remember in the late 80's I went into a high end stereo store and they had the Infinity IRS Beta's - The IRS Betas were $70k if I recall correctly and this was a time when $5000 speakers were considered extremely high end. The IRS betas had two towers with 12 - 10 or 12 inch woofers in two towers and they went down to 16 hz. They played an organ note at 16 and it totally pressurized the room. I was amazed by those speakers.
Those Infinity drivers of that era probably had 8-10 mm of xmax if that - Now you can get the equivalent displacement with a few 15 inch drivers and just about everybody these days with a subwoofer has 16hz extension. The Infinity's seemed very excessive back then (and they were), but looking at them from today's perspective the output does not seem as impressive.
One other thing - each halving of frequency requires 4x the displacement for equal volume - Lets say hypothetically My speakers with dual 9" scanspeak woofers can output 110db at 40hz and have 1 liter of displacement - to have the same output as the mains at 20 hz - the sub would require 4 liters. 16 liters at 10 hz, 64 at 5 hz etc. (the 4 fi 18's have 29 liters of displacement) When you start to look at it like that maybe 4- 22's does not sound so crazy
I'm not interested in cranking out 130 db's at 20 hz. I really have no use for that - I want the subs to be able to play low and free of distortion and driving them well under their limits.
This is the Infinity system I was referring to (this was just a photo pulled off the web)