Would you choose 1 ou 2 subwoofers for a stereo set?

Fast Bass, Slow Bass - Myth vs. Fact See Below:

Mike

http://www.soundstagenetwork.com/maxdb/maxdb061999.htm

@mijostyn Wrote:

  I do think once you get beyond 18" the cone becomes more difficult to control and pistonic motion can be lost.

I don't think it's the size of the cone that's the big issue. I think it's the spider, the length of the voice coil and a careful choice of suspension elements, that helps prevent the pistonic motion loss in woofers. FWIW, I have 15'' and 18'' woofers from the same manufacturer in my two channel stereo system and the only difference between the two woofers is the 18'' has higher horsepower, longer voice coil length and higher efficiency. Both woofers exhibit no dynamic offset. 😎 See below:

Woofer dynamic offset is a problem long known about but seldom discussed or treated. With high input power at low frequencies, many woofers tend to shift their mean displacement forward or backward until the coil is nearly out of the gap. This is most likely to happen just above each low frequency impedance peak of a system. The result is a high level of second harmonic distortion and subjectively a bass character that loses its tightness at high acoustical output levels [4]. The cure for offset, as shown by T, H. Wiik [6], is a restoring spring force that increases in stiffness at high displacement in an amount that counterbalances the reduced B field at the extremes of voice coil travel. Such a nonlinear spider will in fact reduce distortion and eliminate the tendency to offset.

(4) M. R. Gander, "Moving-Coil Loudspeaker Topology as an Indicator of Linear Excursion Capability," J. Audio Eng..Soc., vol. 29, pp 10-26 (Jan./Feb. 1981).

(6) T. ti. Wiik, "Transient Distortion Caused by Nonlinearities in Driving Force and Suspension of a Loudspeaker," Presented at the S6th Convention of the Audio Eng. Soc., Preprint No. 1205 (C-6), _lareh 1977).

One issue is certain, the distance a driver has to move is directly proportional to the amount of distortion the driver produces.  The smaller driver has to move farther to produce the same volume producing more distortion. 

True! 

Mike