One big subwoofer or two weaker subwoofers?

Thanks Sean....I have copied the info so I can read it at leisure. This appears to be the best definition of TS parameters that I have ever seen. What I am looking for is some kind of single dimensionless number (like Bernoulli's number that relates to fluid dynamics) that would describe where a driver falls on the optimization spectrum between vented and sealed. Maybe I will invent such a parameter.

Sean...I guess that QTS is the parameter I had in mind, although as the writup suggests, it does not reliably describe vented/sealed suitability . The JBL 1500 QTS is 0.32, not far from the 0.4 suggested as the boundry between vented and sealed. I am sure that enclosure size, shape, and stuffing has a lot to do with it.

I could easily put a vent in my enclosures, but mice would probably take up residence. (Deaf mice).

El: Here's the "generic" figure that you're looking for.
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EBP-----This measurement is calculated by dividing Fs by Qes. The EBP figure is used in many enclosure design formulas to determine if a speaker is more suitable for a closed or vented design. An EBP close to 100 usually indicates a speaker that is best suited for a vented enclosure. On the contrary, an EBP closer to 50 usually indicates a speaker best suited for a closed box design. This is merely a starting point. Many well-designed systems have violated this rule of thumb! Qts should also be considered.
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The JBL driver that you refer to has an Fs of 25 and a Qes of .34 according to factory specs. The Fs ( 25 ) divided by Qes ( .34 ) equals the EBP ( 73.5 ). This figure is "kinda-sorta" in-between the "basic guidelines" of 50 for a sealed design and 100 of a vented design. Given the lower Qts and higher Fs of the driver, it definitely leans towards the vented side in my opinion. Having said that, it will also work in a sealed design. Playing with box volume along with the type and density of stuffing will have major effects on the resonant frequency and amplitude of the impedance peak.

As a side note, larger box size can allow increased extension, but it does so at the expense of power handling and transient response. There is an optimally sized box / stuffing combo for any given driver. You can fudge the figures up or down to achieve specific goals, but there are trade-offs involved. Sean
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PS... I'm off to work on my Father's sub. Drop me an email if you want to chat further.

Damn, Sean, that's really cool having a father that owns a sub. All I ever got to drive in high school was my Dad's 1953 Buick Special (yes, the one with the 130-horsepower straight six and Dynaslush transmission). I remember taking dates to SEE the submarine races, but having a Dad with a sub would have been a Hell of an improvement!!!

Scott: Thanks for the laugh. Too bad my Dad didn't have a "sub" like that. Taking a date out for a ride in the "sub" and "running out of gas" or having "engine trouble" would have probably been FAR more effective going that route : ) Sean
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