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In Reply to: RE: b&W cm1 notes - midrange and bass posted by ph5y on May 09, 2017 at 15:15:00
Ported designs can be quite good over hang wise. The designer has great leeway in the way a woofer transitions from flat to 24 dB roll off of a ported design and that transition is critical to the degree of over hang. That said a well designed closed box with low Q( a poor example is the LS3/5a although there is a logical reason for it) closed box inherently has significantly less over hang than a ported one. The only one who might claim other wise is Rock port speakers.
But I'm sure that a designer using ported designs(almost every one) will claim that on balance, a ported design is a better compromise of control AND low end cut off. I don't feel that way. I prefer closed boxes. But I can understand the argument.
Follow Ups:
I was a fan of the late Geoffrey Horne, the Gramophone reviewer who was always dissing b&W for having joined the movement to ported designs. He made it sound like they had sold out. And in truth, the last BWs I owned before now, the CDM1s, did display a very un-British sloppiness at the bottom of the spectrum, unlike my sealed JR149s which had all the British virtues (still have 'em and if they didn't look so depressing I might still be using them. The tear in one woofer is inaudible as long as you stay away from organ music!) Horne looks like Nathan Hale at this point:
"I only regret that I have but one career to lose defending sealed-box bass!" I suspect his insolence was a factor in the disappearance of Gramophone's great reviewing team in favor of some woo-woos from What HiFi? when Gram changed hands. But Horne claimed the move to ported bass and polypropylene drivers was motivated by SPL per dollar rather than subtlety of sound and was inappropriate at the "high end." Tend to agree. Audio is a Baby Boom hobby and until we boomers hit our dotage we were into LOUD and while imaging is always exciting there's no imaging in the bass. In fairness, I have heard some ported speakers not from B&W that sounded pretty tight in the bass. My DCM Macrophones for example, did not have a lot of bass but for their size they did pretty well. The new Elacs have pretty good bass.
It's never too late to turn back the clock.
The way a ported speaker transitions from flat to the final 4th order roll off is critical to the degree of overhang. Some ported boxes are quite good if not as good as closed boxes which have second order roll off which all things being equal is superior to 4th order inherent in ported designs.
As I mentioned the one case of a ported speaker which seems different are Rockport designs. The designer claims ported 2nd order roll off and I checked a Stereophile test where one of his designs did roll off at a 2nd order rate from about 40 Hz to 20 Hz. But I suspect and the curve didn't extend far enough that below 20 Hz the roll off goes to 4th order. I don't know and I also don't know what that means to the performance. My guess is the best bass control possible from a ported design. And the few times I've heard a Rockport that seemed to be confirmed.
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