Damping in speaker cabinets.

Firstly, I'm just a retired geologist,
Yet you have a helluvaknack for cab design and modification.

I bookmarked this thread/page, a rare act for me. I will return, re-read and digest.

If you want to tie you former occupation to your current obsession, I think I have a plan for a horn design that calls for rocks between the horn material and the outer case... from maybe the 1930's :D old, old cab design book.

I also thank you for your post as well as your willingness to help others, even doing the calculations and suggesting a replacement speaker and such where no one else will do so (with intelligence or not guessing).
 
I read/heard (might have been a YouTube video of GK factory tour) something from Bob Gallien relative to the Neo 112 cab (IIRC).
He was asked about why he chose not to put a lining in the cabs and answered that during the testing everyone (i.e. him and the testers) thought it sounded better without it.
I remember that, and it was here. Some owners noticed that they weren't lined and when it was suggested that it was a cost cutting thing Gallien posted that reply here. Then a bunch of guys lined their cabs and liked them better, and as I recall Gallien didn't comment on that. Do some searching, you should be able to find that thread.
Clearly there is more to this than just the science. Personal opinion and preferences come into play even though the physics/science still carries on regardless.
There's only one way to find out which way you prefer. I've heard that there's an entire country that thinks warm beer is better than cold, so anything's possible.
 
I remember that, and it was here. Some owners noticed that they weren't lined and when it was suggested that it was a cost cutting thing Gallien posted that reply here. Then a bunch of guys lined their cabs and liked them better, and as I recall Gallien didn't comment on that. Do some searching, you should be able to find that thread.
There's only one way to find out which way you prefer. I've heard that there's an entire country that thinks warm beer is better than cold, so anything's possible.
IIRC pretty much everyone who commented about that subject did seem to like their cabs better stuffed than un-stuffed...I wonder if the factory testing was a case of listening with an answer already in mind.
 
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Some cabinet designs seem to be more forgiving of undesirable tones than others when neither are dampened. I notice that some trapezoid shaped cabs I've looked in that don't have damping material don't sound like they need it. Rectangular cabs of certain material sound like the cabinet back & sides are putting off as much of a sound wave as the speaker itself and it's not good sound.

The mention of the GK MB150 not being dampened is somewhat debatable. There is no liner material on the inside surfaces of the cab, but the cab is so tightly sealed, the air itself dampens the speaker, and the aluminum cab is rigid to the point that it resists vibration, at least in the freq range of a bass
 
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It might be debatable if the purpose of damping was to limit cone travel or to reduce cabinet vibration, but it isn't. And while on the subject a sealed cab doesn't limit cone travel more than a ported cab, it's the other way around.
I wonder if the factory testing was a case of listening with an answer already in mind.
If it happened at all.
 
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Yet you have a helluvaknack for cab design and modification.

I bookmarked this thread/page, a rare act for me. I will return, re-read and digest.

If you want to tie you former occupation to your current obsession, I think I have a plan for a horn design that calls for rocks between the horn material and the outer case... from maybe the 1930's :D old, old cab design book.

I also thank you for your post as well as your willingness to help others, even doing the calculations and suggesting a replacement speaker and such where no one else will do so (with intelligence or not guessing).

Thanks. It's good to know that some notice. I learn a great deal from others here, and am glad to be able to contribute every now and then.

That horn cab design with rock-filled panels sounds somewhat similar to designs by GA Briggs who proposed the use of sand-filled panels - a principle used commercially by Wharfedale in their 60's hifi speakers.
 
I was shocked to hear that about no lining in the cab, but I suppose there could be situations where the physics and acoustics gods simply smile on an unlined cab.

Some years ago I conducted several controlled blind listening tests investigating damping material for a vented, stand-mount home audio speaker that was intended to be used with subs. I had never before made a speaker with such a small box volume relative to the woofer size, and I figured that getting the damping material right was going to be critical. Damping materials used in the tests included Black Hole 5 (a multi-layered cabinet damping product), No-Rez (basically a less expensive variation on the Black Hole 5 theme), several different types of acoustic foam, polyester fiberfill, and several combinations that I no longer remember.

Here's a photo of the speaker (they were built in mirror-imaged pairs):

gi.mpl?u=2112&f=Gamma1a.jpg


I placed the two speakers side-by-side, facing the listener (didn't use the built-in "toe-in" for the testing), and let the listener tell me when to switch back and forth between the two speakers. The program material was a good recording of multiple voices singing in harmony, summed to mono, and the listener was to choose which sounded the most natural. I knew which speaker had which damping material in it, but the listeners did not.

Zero damping material sounded the most natural, to the listeners and to me. This impression held up with other program material as well. I never would have guessed it. I only tried zero damping material when the data from the earlier tests was pointing in that direction. I speculate that the non-parallel front baffle played a role.

Each design is different, and I've only had one wideband speaker system since then that sounded best to me with zero damping material, and that was a bass cab that combined an 18" woofer with cone mids. The internal dimensions were pretty close to a golden ratio, with a chunk taken out for the mid chamber.

Relying on "science" to tell me what damping material, how much, and where, generally hasn't produced good results. My impression is that our models of the internal acoustics of a loudspeaker box, and/or the psychoacoustic implications thereof, are not yet as mature as our models of vented boxes, for example. So for now at least, when it comes to damping material, I have more confidence in trial-and-error.
 
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Some years ago I conducted several controlled blind listening tests investigating damping material for a vented, stand-mount home audio speaker that was intended to be used with subs. I had never before made a speaker with such a small box volume relative to the woofer size, and I figured that getting the damping material right was going to be critical. Damping materials used in the tests included Black Hole 5 (a multi-layered cabinet damping product), No-Rez (basically a less expensive variation on the Black Hole 5 theme), several different types of acoustic foam, polyester fiberfill, and several combinations that I no longer remember.

Here's a photo of the speaker (they were built in mirror-imaged pairs):

View attachment 2966890

I placed the two speakers side-by-side, facing the listener (didn't use the built-in "toe-in" for the testing), and let the listener tell me when to switch back and forth between the two speakers. The program material was a good recording of multiple voices singing in harmony, summed to mono, and the listener was to choose which sounded the most natural. I knew which speaker had which damping material in it, but the listeners did not.

Zero damping material sounded the most natural, to the listeners and to me. This impression held up with other program material as well. I never would have guessed it. I only tried zero damping material when the data from the earlier tests was pointing in that direction. I speculate that the non-parallel front baffle played a role.

Each design is different, and I've only had one wideband speaker system since then that sounded best to me with zero damping material, and that was a bass cab that combined an 18" woofer with cone mids. The internal dimensions were pretty close to a golden ratio, with a chunk taken out for the mid chamber.

Relying on "science" to tell me what damping material, how much, and where, generally hasn't produced good results. My impression is that our models of the internal acoustics of a loudspeaker box, and/or the psychoacoustic implications thereof, are not yet as mature as our models of vented boxes, for example. So for now at least, when it comes to damping material, I have more confidence in trial-and-error.
Which seems to support an argument that there truly is an element of art and possibly even luck in the science of cabinet design.

I had a veterinarian tell me one time when prescribing something for my dog (that represented an off-label use) that no one was sure exactly why what he was giving me worked, but in most cases it seems like a miracle cure. Over thirty years and many German Shepherds later, it's still a go-to solution. Just because we can't model something or explain it with math and science, doesn't mean it can't work out well.
 
Which seems to support an argument that there truly is an element of art and possibly even luck in the science of cabinet design.

I had a veterinarian tell me one time when prescribing something for my dog (that represented an off-label use) that no one was sure exactly why what he was giving me worked, but in most cases it seems like a miracle cure. Over thirty years and many German Shepherds later, it's still a go-to solution. Just because we can't model something or explain it with math and science, doesn't mean it can't work out well.
Good example. My recent adventures in dental acute pain made me bump into a quote explaining that acetaminophen (paracetamol)'s mechanism of action against fever and pain is not completely understood, 130 years after its discovery. As Duke said, it's "just" a matter of further refining the model, not black arts of course.
 
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I recently lined an old Hartke B30 combo (30 watts, 1 x 10) with excellent results.

I've never liked this amp. I got it for virtually nothing years ago but it's pretty much been gathering dust. It had an inherently awful middy sound that couldn't be dialed out.

I recently lined another cabinet (Sunn 215S) with Walmart mattress topper, and thought, What the heck, let's look inside the Hartke and see if I can use the leftover lining. It had no lining. I lined it (all surfaces except the baffle) and am quite impressed by the improvement. The inherent mid-quack is tamed. Now it sounds like a usable cheap combo amp, rather than the total POS it was. I'm not hyping this amp by any means, but if you have a crappy combo amp, you can't go wrong by trying this. $9 to line two cabinets, not bad!

I brought it to a home jam session and it was enough to keep up with moderately loud drums, 2 guitars, and keys -- sounded good, just breaking up a bit, the nasty midrange was gone, tone could be controlled.

P.S., this is a ported cabinet, so I lined it rather than stuffing it.
 
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Some of the software will calculate the cabinet damping material.
It can always be a starting point and the rest done by ear.

In any case the cab can be measured before and after.

It always seems like a missed opportunity when somebody adds or removes damping but never measures or records the before and after.
 
Interesting discussion.
I'll throw in a couple of examples from the past.

Back when I was starting out almost everyone I knew used the Fender small 212 cabs.
Those were sealed and stuffed with fiberglass.
From all I ever heard about him, Leo Fender was a notorious bean counter.
That makes me think it must have made quite a difference if he OKd the extra cost.

A few years later Acoustic came along.
As far as I know, none of their cabs had any damping material.
They were the hifi sounding amps of the time and pricey enough to have been able to cover the extra cost if it sounded better.

This seems to rule out the cost cutting consideration.
 
I find that when it comes to damping or changing it, you have to experiment with materials and thicknesses to determine what is going to work best, if any at all.

It’s somewhat difficult to perform these tests. I run prerecorded bass thrugh the cab and listen. Change the damping and listen. Differences can be subtle. But that takes time between listening tests so you can’t easily A/B. Recording the samples can help but it complicates things. Focus your istening for a lack of muddiness in the mids.

The efficiency of the damping material makes a difference. A good product works well and doesn’t have to be thick. Products that work well for me include wool felt, and matted denim. The denim is often made of recycled cotton, people like the green aspect. Of course, foam is more common and works very well.

If you are only lining one surface, many choose the one opposite the speaker. The damping serves to absorb sound waves and dissipate them rather than allowing them to bounce off a surface and reflect them back, combining with primary waves to create mud.

This is an example of the felt that I use. There are less expensive felted alternatives such as felt carpet underlaying. I like this material because it is stiff and can be press fit into place.

FELT from Aircraft Spruce

8E1DE353-2AF6-48CF-A0DF-9F2DD74038D6.jpeg


Here are examples of foam damping.

https://www.parts-express.com/Search.aspx?keyword=Acoustic sound damping&sitesearch=true

Here is denim damping.

Green Products, Green Building Materials | Green Depot

UltraTouch Denim Insulation | Recycled Denim Insulation,

echo eliminator: Acoustical Absorbing Material | Echo Eliminator Wall Panels
 
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Cabs shouldn't add anything to or detract anything from the signal sent to the drivers. Keeping that from happening is the reason for damping. You don't need fancy testing gear to see if your cab needs damping. Remove a driver, stick your head inside the cab, and hum. Vary the pitch of the hum from low to high. If there's a resonance that causes a response peak you'll hear it. Line the cab with enough damping to get rid of that resonance, but not more than required, or the cab will be over-damped. It seems weird, I didn't quite believe it when I saw it described, but I tried it and it works. The most important surface to line is the back, but any parallel surfaces in the box will have resonant modes, so they should be lined. Duke says the cab he pictured sounded better without damping. The only parallel walls it has are the top and bottom, and they're not behind the driver, so I'm not surprised.