Do You Miss Acoustic Suspension Speakers?

[fmw]

If I remember the literature from Advent back in the day, the idea was to use more compliant, longer throw drivers that would gain some control from the air pressure inside the enclosure. The longer throw would produce better bass response than a normal driver but not sound loosy goosy. My subwoofer has a very long throw driver that goes down to the low 20's in a sealed enclosure. I think it is the same idea except that the subs aren't trying to reduce the size of the enclosures while the acoustic suspension speakers were all about that.

 

[Kingnoob]

If I remember the literature from Advent back in the day, the idea was to use more compliant, longer throw drivers that would gain some control from the air pressure inside the enclosure. The longer throw would produce better bass response than a normal driver but not sound loosy goosy. My subwoofer has a very long throw driver that goes down to the low 20's in a sealed enclosure. I think it is the same idea except that the subs aren't trying to reduce the size of the enclosures while the acoustic suspension speakers were all about that.

Even cheap subs claim to be long throw , but high end ones that are big Xmax are far superior just cost significantly more . Only some pro subs cannot claim big Xmax ?

Acoustic suspension requires a certain amount of internal volume ?

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[dlaloum]

The issue isn't so much "long throw" as the ultra light suspension used in the original AS woofer designs...

The surround was designed to impose as little resistance to motion as possible... support was from the sealed nature of the box.

More recent woofers seem to be mechanically quite different, and their "heavier" surround, is then dependent on and requires more work to drive it, and the surround keeps it in place - hence is inherently providing more resistance as well.

Are there manufacturers making woofers specifically designed for old style AS use?

 

[shadyJ]

Are there manufacturers making woofers specifically designed for old style AS use?

Nope. Modern loudspeaker drivers have much more powerful motors, and the magnetic field is a much larger factor in the restoring force of the coil position than backspring pressure from the air.

 

[dlaloum]

Nope. Modern loudspeaker drivers have much more powerful motors, and the magnetic field is a much larger factor in the restoring force of the coil position than backspring pressure from the air.

Which also means, as a direct corollary, that more power is required to drive the woofer... (and possibly also, higher distortion levels when driven at lower SPL's?)

 

[ryanosaur]

(and possibly also, higher distortion levels when driven at lower SPL's?)

I wouldn't necessarily expect that. If the Driver is well designed, it should perform well within it's first bit of stroke. On the other hand, it is in pushing that stroke toward Xmax where one would begin to expect issues in compression or other distortions.

 

[Verdinut]

Nope. Modern loudspeaker drivers have much more powerful motors, and the magnetic field is a much larger factor in the restoring force of the coil position than backspring pressure from the air.

James,
Also, I think you will agree with me with the fact that compliance of the suspension of the currently produced drivers is quite stiffer than that used on AS woofers. That also contributes to making them less dependent on enclosure backspring pressure.

 

[MrBoat]

No. When I was a lad during the roomie years, there were Advents and JBL L100s in the house simultaneously. For the kind of music I listened to, and the concerts I witnessed, the JBL just trounced the Advents. I never really looked back and ported, higher displacement designs were more of a sure bet. The Advents didn't sound bad, but more like they were just in the wrong neighborhood, perhaps.

The JBLs got flogged hard for about 3 years before they moved on with their actual owner and he still has them in play. As I get older and less complicated, a good, full-range, ported design, manages to spin my little flywheel most days.

My current F-12 Tempests manage to cure the JBL itch, and bring modern neutrality/imaging etc. as a fusion of sorts. Still, after more than 4 decades in, the three essential requirements with full-range speakers remains constant, and everything else can be reasoned out with headroom and (at least tone controls) EQ.

 

[shadyJ]

James,
Also, I think you will agree with me with the fact that compliance of the suspension of the currently produced drivers is quite stiffer than that used on AS woofers. That also contributes to making them less dependent on enclosure backspring pressure.

It's not just the compliance, it is the linear range of travel of the suspension. Modern driver suspension can have a ton of computer modeling to extract every last mm of Xmax. Some spiders use different materials going from the outer to inner radius. There are all kinds of different surround designs too. They all work with the motor to get a level of linear travel that far surpasses anything that was possible in AS's day. I am not sure the principles of acoustic suspension could be updated using modern design methods where it could be competitive against regular loudspeaker designs.

 

[Verdinut]

It's not just the compliance, it is the linear range of travel of the suspension. Modern driver suspension can have a ton of computer modeling to extract every last mm of Xmax. Some spiders use different materials going from the outer to inner radius. There are all kinds of different surround designs too. They all work with the motor to get a level of linear travel that far surpasses anything that was possible in AS's day. I am not sure the principles of acoustic suspension could be updated using modern design methods where it could be competitive against regular loudspeaker designs.

No matter the type of suspension used In any sealed enclosure, there will always be some linearity distortion caused by compression and decompression of the entrapped air. That is why a well designed woofer or subwoofer in a vented cabinet will distort less while being more efficient than the driver in a sealed box.

 

[fmw]

Even cheap subs claim to be long throw , but high end ones that are big Xmax are far superior just cost significantly more . Only some pro subs cannot claim big Xmax ?

Acoustic suspension requires a certain amount of internal volume ?

Sent from my iPhone using

I have no experience with pro subs so I can't comment. The 15" driver in my home theater sub has a huge convex rubber surround that lets the driver move a lot of air. I have three other subs in the house and none of them have the kind of surround of the 15 incher in my home theater. They do a decent job but seem to struggle compared to the 15 incher. But they are smaller 10 and 12" subs so it isn't a fair comparison.

 

[Kingnoob]

I have no experience with pro subs so I can't comment. The 15" driver in my home theater sub has a huge convex rubber surround that lets the driver move a lot of air. I have three other subs in the house and none of them have the kind of surround of the 15 incher in my home theater. They do a decent job but seem to struggle compared to the 15 incher. But they are smaller 10 and 12" subs so it isn't a fair comparison.

Yeah I have a similar sub in my set up I rarely use , and now the tv died in that set up . Unfortunately my 15” won’t fit in the room my main set up is in. So i stacked two 10” subs.
The 15” can easily rattle my bedroom. Sure looks dirty in the pics yet it’s not that’s the clear coat messed up everything.
Any pics of your sub or brand etc ? Mines stereo integrity 15”.

 

[blanddawg62]

Again read the attached article on acoustic suspension. If the box doesnt have a port, aka vented, aka bass reflex, its by definition a "acoustic suspension" design. And you are correct it is not a very common speaker design anymore but for subs its still prevalent. Its also part of the reason that good subs almost invariably include very high power class D amps. The latest DB1D, for example, has a 2kw amp! BTW acoustic suspension predated AR. One of AR's founders, Vilchur came up with the design a couple of years before AR was founded by himself and Kloss

What is the point of saying 'acoustic suspension predated AR'? The founder of AR was the inventor of acoustic suspension. As my kids would say, 'And your point is?'

 

[blanddawg62]

Again read the attached article on acoustic suspension. If the box doesnt have a port, aka vented, aka bass reflex, its by definition a "acoustic suspension" design. And you are correct it is not a very common speaker design anymore but for subs its still prevalent. Its also part of the reason that good subs almost invariably include very high power class D amps. The latest DB1D, for example, has a 2kw amp! BTW acoustic suspension predated AR. One of AR's founders, Vilchur came up with the design a couple of years before AR was founded by himself and Kloss

They are all variations on the original principle. Closed enclosures with passive radiators can be considered a hybrid of ported and acoustic suspension design since its still a pressure vessel that dampens the excursion of the active cone while using some of that energy to produce lower octaves from the passive cone. Some also include the acoustic suspension into the infinite baffle category since the primary idea behind the "stuffed" sealed box was to eliminate the sound radiating from the cone's rearward travel. BTW there is still one company that makes mostly acoustic reflex speakers, Magico! Although it takes some "magic" to come up with the cash to buy a pair If you look at the design closely, its an AR design built from space age materials.

That is why they are so expensive.

 

[blanddawg62]

Yep, the earth is flat and gravity is a theory......

The earth is both flat and round, like a quarter.

 

[everettT]

That is why they are so expensive.

Care to explain what is so expensive and why?

 

[Verdinut]

Care to explain what is so expensive and why?

Is it because they are no longer made and the rare ones which are still in good working order, have become a collector's item?

I guess people have lost interest in them because of their low sensitivity. You need more amp power, hence more spending.

 

[everettT]

Is it because they are no longer made and the rare ones which are still in good working order, have become a collector's item?

I guess people have lost interest in them because of their low sensitivity. You need more amp power, hence more spending.

Thanks, I wasn't sure what he was relying as it sounded if it wasn't currently cost effective to produce.

 

[TLS Guy]

That is why they are so expensive.

That is all nonsense. There are plenty of sealed designs around. A sealed speakers is not by default acoustic suspension. An acoustic design has a unique set of T/S parameters, that has a very compliant suspension and minimal restoring force. The major restoring force is the air spring in the cabinet. This makes for inefficient designs and prone to failure with age due to sag in the suspension. I know of no drivers currently available for an acoustic suspension design, they are history.