I'm confused as to how a subwoofer can have a Resonant Frequency of say 18 hz, but a frequency response that only goes down to 25 hz. If the sub only responds to 25 hz, how can you know the fs is lower than that. The new Soundstream T5's are an example of this. I just don't understand.

-C

I don't know the specifics but the 18Hz is the free air resonance of the sub. The enclosure will, in a large part, determine the frequency response of the sub.

Edited August 1, 200718 yr by Luke

I understand the difference between free air resonance and the resonant frequency in a box. Back to my original question, if your sub can't even respond down to your free air resonance, how do you know that's actually the subs free air resonance? Is it just a mathematically formula on paper that states the sub "should" be perfectly balanced at this frequency even though we can't actually see it in action?

Also, what is the point of having a sub that doesn't even respond down to it's Fs. It will never be balanced while it's being played right? Where's the SSA geek squad, I mean Tech Team when you need them?

-C

Fs is a mathematically derived value.

Frequency response (given as a numerical range) is usually a very general and inaccurate method of rating a subwoofer; most manufacturers will not specify if the upper and lower limits are the f3, f6, or f10 (frequency at which response is down 3dB, 6dB, or 10dB respectively). If you can get your hands on measured frequency response shown via a spectral graph, then you have a much better idea of what it is capable of, but the system is the dominant factor, not the sub. It's all about the implementation.

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Unless you are screwing around with IB subs...