can someone me understand fs?

This spec is somewhat confusing to me.  My understanding is that Fs indicates the "resonant frequency" and although that number doesn't indicate the absolute bottom-end frequency a sub is capable of reproducing it does sort of "give you an idea".  So I would therefore expect that a sub with an Fs of say, 35hz, wouldn't play as deep as a sub with an Fs of, say, 25hz.  But I've seen multiple high-end SQ-based subs with what seem to have a relatively high Fs number (30hz-35hz), so that makes me think maybe it doesn't really "give you an idea" as to how deep a sub will play.

So what's the deal...what exactly is Fs supposed to tell you, is Fs a meaningless spec, is it meaningful but only in conjunction with other specs, etc?  I'm hoping someone here can shed some light on this spec or direct me to a resource that thoroughly explains it.  Thanks in advance for any help!

fs is the resonant frequency of the driver in free air.  Using an enclosure you can change the resonant frequency of the system and push it down (or up.)  The key factor to know along with fs is the driver's Qts.  IN GENERAL, if the Qts is less than 0.39, the enclosure will tune higher than fs and above 0.39 system tuning will be lower than fs.  It is also possible to operate below fs in any system using EQ and tons of amplifier power.Support the12volt.com

DYohn wrote: It is also possible to operate below fs in any system using EQ and tons of amplifier power.

Ah.... the ol' BFI method. That's "Brute Force and Ignorance". A long throw and monster power handling is really necessary to make it work, but it's quite possibly my favorite method. It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."