DCR (dual chamber reflex) which port method is correct

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Many thanks for this illuminating comparison. Evidently, conventional single bass reflex is the best. Low frequency behavior below 60 Hz is almost identical between the three of them. In the pass-band DCR is remarkably worse, but it can be improved slightly with higher tuning (higher than 75 Hz).
 
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there's something in the order I sometimes do things on hornresp which brings an "empty box" error

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hey Sonce - I found the reasoning behind Briggs acoustic filter - see my AA post which contains a link to GA Briggs' book "A TO Z IN AUDIO" where Briggs describes the use of the filter.

RE: G.A. Briggs' Acoustic Filter functions (I was correct) see the definition from his book - freddyi - High Efficiency Speaker Asylum

Briggs in those days was using what I think were very compliant drivers with foam surrounds. The "filter" improved power handling below tuning.

IIRC, sometime in the late 1970's or maybe early 1980's, there was a commercially available speaker which had that "filter" and whomever reviewed
it thought it had vibrating "reeds" (maybe like a kalimba - lol)
 
Late comer and still fighting insomnia despite about 4 hours sleep in 90, so not exactly at my best. However, I'd point out that the DCR, while hardly a panacea, is far from being worthless or the shocking aberration that is implied. In normal practice, it tends to result in a fairly narrow / high Q notch in the response, usually on the order of about -3dB - -4dB. Since this is far less than the kind of deviations caused by most rooms, while certainly a caveat, it isn't necessarily a make / break situation either, since the flip side is the reduced driver excursion and increased dynamic range within its operating passband. This can be worth having, as the secondary tuning is often (depending on design) in the region where much of the LF energy in rock &c. music is located. Is the DCR load a compromise? Yes, of course, and I generally prefer QW alternatives, but it's fair to say that it can also give decent results.

Conversely I've never found the DBR (as in driver in a small chamber, venting into a larger chamber which is itself vented to the room) to provide useful design advantages. The DCR is usually more linear and as good a load or better; it also tends to be easier to design, or I've always found them to be at any rate. YMMV as always of course. Interesting how you can take these multi-tuned chamber designs out into the more extreme BP and the Karlson variations; they're all related at some point or another.
 
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