Subwoofer FS


New member
Username: Likeapuma


Post Number: 9
Registered: Aug-06
So I know as a general rule, a subwoofer doesn't perform as well at levels below it's FS. But I read somewhere that there are other factors that go into it. Could anyone enlighten me on this issue. Because i've seen subwoofers that are supposed to be top of the line, but their Fs is like 31 hz, and I couldn't imagine they'd be any good for most of the rap I listen to. Any help is appreciated.


Bronze Member
Username: Bobimpact

Danbury, CT US

Post Number: 39
Registered: May-06
Fs refers to the free air resonance of a driver. Essentially this is the frequency that will cause the driver to virbrate in free air (no enclosure) While the Fs value does say some things about a woofer, it certainly does not say that a driver with an Fs of 31Hz will not play deep bass. It is simply one factor that some companies have tried to say is more important that it really is. Just like some companies claim that "Volume Displacement" (Cone Area X Excursion) is the best measure, ignoring SQ entirely, so too have some made Fs a buzzword. As I tell my customers, numbers are fine, but your ear makes the choice.

Seperate from the discussion about Fs, remember that human hearing only goes down to 20 Hz, not 0. Many speaker manufacturers deemphasize the need for 20Hz to be heard, as the driver would have it's SQ in the upper end of it's dynamic range (which is much more audible to the human ear.) compromised. Essentially, because a 20Hz tone must be louder than a 60Hz tone for the human ear to consider them "flat" all subs would be "bottom heavy" if they were tuned this way.
You can google "Fletcher-Munson Curve" for more information on this.

Bronze Member
Username: Bobimpact

Danbury, CT US

Post Number: 40
Registered: May-06
I almost forgot, most cars have what is called a "cabin gain" that boosts the lowest octaves. Essentially, this boosts the 20Hz range naturally, "flattening" out the curve by boosting at 20Hz.

Gold Member
Username: Basshead86

Google is your Friend, FL

Post Number: 4921
Registered: Aug-05
good info bob.:-)
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