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Discussion Starter · #1 ·
I am looking for some technical information on bandpass enclosures. As an example, JL Audio has a great page that explains how changing the chamber volumes and port tuning will impact the final results of a single-reflex bandpass (some call it a 4th order).


But, that page does not recommend a dual-reflex bandpass (some call it a 6th order) and does not provide any information on how adjusting chamber volumes and port tuning will impact the frequency response. It provides no information on series tuned bandpass enclosures. I have not been able to find a source or reference that covers anything more complex than a single-reflex bandpass. Does anybody have a source or reference on this topic? I am not afraid of math so I am open to reading scholarly publications and technical bulletins with formulas.

I have modeled some dual-reflex enclosures in WINisd, so I can see how adjustments change the frequency response, but I would like to know the underlying theory.

I have searched the forums and scoured the web and have yet to find what I am looking for. I suspect that I need to start with the original papers by Theil and Small and start working my way through the academic literature in order to find what I am looking for. Hopefully one of you can point me in the right direction.
 

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The front chamber on a bandpass box is a low pass filter.

It's that simple.

So a single reflex bandpass box is a sealed box with a low pass filter in series. The low pass filter changes the rolloff of the sealed box from 12dB/octave to 24dB/octave.

The smaller the chamber is, the lower the Q of the filter is. The larger the chamber is, the higher the Q of the filter is.

Dual reflex is the same idea, but now you're filtering a ported box instead of a sealed box.

I don't recommend dual reflex. They're very easy to screw up.
 

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Discussion Starter · #9 ·
I don't recommend dual reflex. They're very easy to screw up.
I agree. The marginal benefit to marginal cost (mostly in terms of effort) of bandpass designs is very rarely worth it. I am just trying to satisfy my curiosity. Thanks for your response, it has been helpful. Just to clarify, I can think of a dual reflex enclosure as a ported enclosure with a low pass filter.

Here is a related question: What kind of driver works best in bandpass (either single reflex or dual reflex)?
 
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