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
>
PS... I'm off to work on my Father's sub. Drop me an email if you want to chat further.
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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.
---------------------------------------------------------
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
>
PS... I'm off to work on my Father's sub. Drop me an email if you want to chat further.