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

Eliot, your speakers are not acoustic suspension. With the port sealed they are closed box but not acoustic suspension. A closed box is acoustic suspension when the air in a sealed box has a significant affect on controlling the woofer. If the woofer works in a ported box the spider controls the driver moving in and out and  air affect in the box is minimal. Acoustic suspension occurs when the air in the box is necessary to restore the woofer to neutral. It implies a soft spider that can't do the job on its own. Even if the box is closed and the spider controls the woofer it still isn't acoustic suspension; it's just closed box.

The problem with the nomenclature occurred because in the 60s acoustic suspension was 2/3 of the market. When Thiele/Small did the math so reflex boxes could be designed on paper without guessing like it was before acoustic suspension went out of favor. But since acoustic suspension at one time was almost all closed boxes people forgot that it wasn't a synonym for closed box and recalled the popularity of the term acoustic suspension and started using the terms interchangeably in correctly. Edgar Vilchur who founded Acoustic Research and along with others, especially Henry Kloss made acoustic suspension popular would be rolling in their graves at the misunderstanding. If you understand math set theory acoustic suspension is a PROPER subset of closed box.

 

I listen to AR9's that are 45 years old. They, to me, are the perfect example of the old acoustic suspension system. They were a reference speaker of their day. Many things have come and gone in the last 45 years. I still enjoy listening to my AR9's, nearly every day. They have the bast bass that I've ever owned, maybe the best that I've ever heard. They are no slouch in mid or highs either. They are a very well designed speaker system. I would never get rid of them. I might try something new at some point but if I don't, I'm OK with what I have as well. 

The AR9 was real acoustic suspension but a hanger on. By that time bass reflex had taken over. It became harder and harder to do acoustic suspension as bass reflex took over. Many(most?) speaker companies buy their drivers from a few main suppliers. And the suppliers build what sells. And bass reflex was what was selling. To get an acoustic suspension woofer you either had to design your own or pay a supplier to build something special for you which, of course, is more costly than standard designs.

And closed box is hard to sell now. It sounds different. Bass reflex sound is what most people have heard and what they think bass sounds like. There are very few closed box designs today. Off the top oif my head there's Magico, a top of the line design. But I don't know if they are acoustic suspension or closed box though I think they use the term acoustic suspension. They use closed box because they know it has less ringing that bass reflex.

@dynamiclinearity Wouldn't Legacy Focus SE be sealed enclosures? 

I may be too old school to "like" the new stuff. I really don't know. I get curious about the open baffle stuff, find it interesting but that's about as far as it goes for me. I have absolutely nowhere to listen to any new concepts or designs. I am very accustomed to what I do listen to and I don't ever get tired of it. I also have a pair of KEF R107's. They have a nice sound as well. 

I have to correct myself. I just looked at the Legacy Focus SE specs and it says that they are rear ported.