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Why are ported designs ubiquitous?

141.161.175.52

Posted by Peter on December 22, 2009 at 18:19:36

I am old enough to remember the sixties when the acoustic suspension sealed box speaker was first introduced by AR. The design had a number of merits:
1) response into the 20 hz range from a medium size speaker
2) a slow rolloff in the bass rather than a sharp hump and falloff
3) measurably much lower harmonic distortion.
4) better bass impulse response - a ported design, according to John Dunlavy, cannot decay more than 3db per cycle. Working out the math, a 60 hz plucked bass guitar note at 90db will take 30 cycles - half a second - to decay. That ought to be audible.
From the early 60s through the 80s the acoustic suspension design was the only choice for makers of quality box speakers. The rivals were large horn designs and transmission line designs a la I.M. Fried.

But in them mid-90s it seems everyone went over to ports. Ported speakers will play 3db louder for equal wattage, and a customer base that listens to rock and heavily electronic music might not notice, or might even enjoy, the gratuitous bass output. It seems the industry press cooperated too: Despite taking many sophisticated measurements, measurements of bass harmonic distortion - once a standard review feature - are rarely seen nowadays. Might the reviewers be protecting someone? What good is a flat bass if much of it is higher harmonics pretending to be bass? Anyway, is there any rational explanation for this changeover or is it just the idea of getting an extra 3db from the amplifier - seemingly a poor rationale for a "high end" company.

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