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Why not acoustic suspension?

When I was young, late 60's early 70's, the sealed or acoustic suspension speakers were quite commonplace. Now bass reflex, ported speakers seem to be much more common. My understanding is that both speaker designs, assuming competent design will perform very well. Perhaps with the ported getting a slightly lower bass response and higher efficiency gives it the edge. Thinking efficiency though, amplifier watts don't cost that much more today so it doesn't seem like a deal maker. What I don't understand from a pragmatic corporate standpoint is why more acoustic suspension speakers aren't available. My understanding is that the sealed speaker box can be smaller which would be a plus from a cost standpoint, both in less material, lighter cabinet and more speakers could be shipped in a truck reducing shipping cost. Any thoughts as to why the industry has shifted so hard in the bass reflex direction?

61falcon
faustuss's avatar
faustuss
815 posts
 

@61falcon 

"Can anyone name modern acoustic suspension, true acoustic suspension speakers made today?"

The ATC SCM7 - SCM20 series are acoustic suspension which refers to any speaker whose woofer is mounted in a sealed encloser where the air trapped inside acts like a spring stabilizes the loose and floppy cone suspension. Acoustic suspension is also known as an infinite baffle.

The advantages lower frequency extension, a more benign or smoother impedance modulus and lower bass distortion. The disadvantages are mostly dramatically less efficiency requiring a more powerful amplifier. 

It was common to see rather large enclosures at one time with woofers of twelve to fifteen inches or more that could reproduce bass notes as low as 15Hz. Some of these were produced by ADS, Avid, Cerwin Vega and others. The Advent Loudspeaker, the Acoustic Research AR 3a though smaller than the above were still fairly large with up to two square feet of internal encloser volume. Radio Shack also marketed quite a few fairly large acoustic suspension speaker systems.

erik_squires
17,543 posts
 

BTW, I asked fellow hobbyists at DIYaudio, and the consensus is that we still call a box with a driver in a sealed box of small size "acoustic suspension." 

The drivers have changed over time but a sealed box is almost always acoustic suspension.  Disagreements should come over to DIYaudio. :) 

jwei
255 posts
 

So if the box includes a passive radiator, it is technically not "sealed"?  Which would make my Thiel 3.6s and Sunfire subs not acoustic suspension?

ditusa's avatar
ditusa
2,396 posts
 

So if the box includes a passive radiator, it is technically not "sealed"?

A passive radiator is a ported speaker, JBL was the first to implement the passive radiator in 1959. See here

Understanding enclosure principles see here page one-twelve. 😎

Mike

rlj
75 posts
 

I am concerned about insect or rodent infestation through open rear ported speakers such as the MoFi Source Point speakers.   With these speakers the port is open and low enough for a rodent to climb into.   I'm 73 and I remember back in the 70's many of the speakers were acoustic suspicion such as Advent and KLH.  Yes, acoustic suspension speakers seem to have lost their popularity.  I treasure my acoustic suspension Kirksaeter speakers.   

 

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