[rcag_ils]

I wanted gray or black foam but the only stuff I found at our neighborhood foam and fabric place was a block of foam, so I sliced it into 1/2" slices on my band saw then cut it to shape with a razor knife using a 1/4" MDF template I made.

Cutting a block of foam into 1/2" slices could be a task, I am sure they make foam in different thickness somewhere, I'll keep looking, maybe automotive upholstry shop.

[Wayner]

How much do you need? I have some 1/2" charcoal gray foam here on the shelf.

Wayner 

[rcag_ils]

Wayner, you have PM

[turkey]

I plast-i-clayed a turntable years ago and found that it worked out really well.

Adding clay to a pair of speakers didn't seem to do much.

A lot of woofers these days use cast baskets. Given the stiffness of the basket and the large mass of the magnet assembly, it seems unlikely that the moving cone would excite the basket very much, especially since it is decoupled via the surround and spider anyway. (Some modern drivers even use polymer baskets that have internal damping, so what about those?)

Well-constructed speaker cabinets have stiff walls and adequate bracing. They may even use damping materials in the enclosure panels themselves for CLD.

So is adding additional damping worthwhile? Will it make an audible difference these days?

Again, I would ask if Frank immediately opened his HT3s and applied clay?

Even using an accelerometer to measure the movement of the enclosure walls may not tell us anything unless you examine whether or not it's really audible under normal listening conditions.

You get things like "We measured it before and after and there was a lot less movement after adding damping. It's a major improvement. Just look at these graphs."

Ok, but was it audible before?

There's a lot of that in audio. Designers focus on one parameter or another, often an obscure one. Then they loudly proclaim that their thingamajig has better XYZ than any other thingamajig on the market. "Our front-panel LEDs are redder than anyone else's!"

But is it really audible?

Putting some clay in your speakers obviously is not a big deal one way or the other. It's not costly, nor terribly time intensive. But I still wonder whether it produces audible improvements in modern speakers.

[avahifi]

I have not done my HT3s or Songtowers simply because I have a lot of other things to get done around here and it is a big job to get the drivers in and out of the Salks without marring the cabinets (at least for me it is).

However, one way to do a before and after is to just do one speaker first, and then compare the two side by side with the system set to mono.  That will tell you immediately whether it is worth the effort.

Frank

[turkey]

However, one way to do a before and after is to just do one speaker first, and then compare the two side by side with the system set to mono.  That will tell you immediately whether it is worth the effort.

I did just that a number of years ago and the results were inconclusive. Neither I nor several of my friends heard major differences. I wound up claying both speakers, but I was never truly convinced that it was worth the time and effort.

I'm sure it's a very useful technique with some speakers though, especially old ones that weren't constructed that well.

[turkey]

I have not done my HT3s or Songtowers simply because I have a lot of other things to get done around here and it is a big job to get the drivers in and out of the Salks without marring the cabinets (at least for me it is).

So it isn't that important.

[avahifi]

It was important with the B&W speakers I did at their factory, and they did have very rugged cast frames.  However your results may vary of course.

Frank

[Minn Mark]

I used plasticlay on my ESS speakers (PS*'s, 8 woof + 10 passive radiator and Heil tweeter--did the woofer basket and back of tweeter) back in the 80's, and also modded by bro's Advent (Baby)...marked sound improvement.

Turkey,
please reply to the thread with details as to how you modded a TT with plasticlay...I am intrigued.

Cheers,

Mark

[turkey]

Turkey,
please reply to the thread with details as to how you modded a TT with plasticlay...I am intrigued.

I replied to your PM, but basically I just followed Frank's instructions from an old issue of Audio Basics. They're available on his website.

I filled in the underside of the base of my turntable with clay, being careful to avoid moving parts. With that and a Grado with the Longhorn mod, it was like I had bought a new, expensive turntable.

I remember using the microwave to make the clay easier to spread. I don't think I'd recommend that, because it was too easy to liquify the center and it was then blisteringly hot.

Take the clay out of the package and put it in a ziplock bag. Squeeze the air out, seal it, and put the whole thing into a bowl of hot water. That should soften the clay up quite well without any risk of burning yourself. I'd probably do it a stick at a time just so it's manageable.

[rcag_ils]

I bought the model clay today, and just cleaned up the woofers for restoration.

There will be no A/B listening test, because I bought these speaker with disintegrated foam surrounds, I'll just put the clay on after the surrounds are done, I am not going to take the woofers in and out of the cabinets just for that.

The plasti-clay idea's just simple physics that tames the resonance, I think it'll work.

[mark funk]

When I did my sub woofer (28"H X 17"D X 16"W ) I made a mold about 12" L and 6" W and 1/4" D and rolled it with a rolling pin. I went quite fast, my wife rolling and I was putting the clay in and I clayed all the insides of the box. We did it in the
summer time, just put it out side in the sun that works good too.

                                                                                 

[turkey]

While I'm sure there are speakers out there that would benefit from clay, I'm just not convinced it's worthwhile in all cases.

With my current speakers, the total weight of the woofer is 6 kilos. The weight is mostly in the magnet assembly. The moving mass is 33 grams.

I don't see that the 33 gram cone assembly is going to get the rest of the driver vibrating very much, especially since it's decoupled by the surround and spider, and the frame is clamped to the enclosure quite well.

There's more of a chance of exciting the enclosure walls via the air in the enclosure since there is much more surface area involved, but they're quite stiff in this case, well-braced, and the front and rear panel use constrained layer damping. So I don't see that this is really going to be audible either.

Covering things with clay would seem to work well when they are thin, flexible, and low mass. (It would probably work well on a speaker cone, except that the added mass would drop efficiency way down, and it's hard to apply it evenly. So it's not really suitable here either.)

I would recommend adding bracing inside your speaker enclosure if you're having problems with the walls vibrating. If the driver baskets are vibrating or flexing, put a brace between the enclosure walls and the magnet assembly. Tying the whole thing together will stiffen it and also tie all the mass together. The more mass, the less likely it's going to be excited by the cone or air in the enclosure.

I noted that the Salk speakers I've seen have stiff, solid enclosures that don't "sound" much when you rap them with your knuckles. Some other well-constructed speakers are like this too. I find it unlikely that adding clay to speakers like these will do much.

But hey, clay away if that's your thing. 

A final thought... it should be fairly easy for an engineer to measure the movement of the walls of a speaker enclosure and figure out the actual acoustic output of the enclosure referenced to the output of the drivers themselves. I don't think I've seen that done anywhere recently (if ever). Then we could decide if this is actually an audible problem, or if we're straining at gnats.

[rcag_ils]

I think it has more to do with the property of the material that the drivers are made of, not just weight. Most speaker drivers are made of metal, metal tends to ring whether if it's a 2lb metal or 2000 tons metal, and the ringing may modulate with the sound. Plasti-clay damps out some of the ringing.

[jtwrace]

A final thought... it should be fairly easy for an engineer to measure the movement of the walls of a speaker enclosure and figure out the actual acoustic output of the enclosure referenced to the output of the drivers themselves. I don't think I've seen that done anywhere recently (if ever). Then we could decide if this is actually an audible problem, or if we're straining at gnats.

When I designed / made my aluminum cabinet subwoofer, I did all my measurements using mulitiple accelerometers that were being logged at 500Hz.  It's "easy" to do with the proper equipment.   

[turkey]

A final thought... it should be fairly easy for an engineer to measure the movement of the walls of a speaker enclosure and figure out the actual acoustic output of the enclosure referenced to the output of the drivers themselves. I don't think I've seen that done anywhere recently (if ever). Then we could decide if this is actually an audible problem, or if we're straining at gnats.

When I designed / made my aluminum cabinet subwoofer, I did all my measurements using mulitiple accelerometers that were being logged at 500Hz.  It's "easy" to do with the proper equipment.   

How loud was the output from the enclosure walls compared to the output from the woofer cone?

[bob nielsen]

Don't use duct seal !  We use it for pellet traps at an air gun range.

It weeps oil. 

[avahifi]

When B&W went back to their lab laser vibration measuring equipment after I showed them my speaker framework damping ideas, they told me that they found that the sonic output of the speaker basket was only about 10 dB down from that of the driven cone at some frequencies.  That certainly opened their eyes, however they never did completely follow through on the idea.

Frank Van Alstine

[turkey]

When B&W went back to their lab laser vibration measuring equipment after I showed them my speaker framework damping ideas, they told me that they found that the sonic output of the speaker basket was only about 10 dB down from that of the driven cone at some frequencies.  That certainly opened their eyes, however they never did completely follow through on the idea.

Frank Van Alstine

Assuming that the output of the speaker basket makes it out through the cone (which I find likely), it would seem to have been a large problem in this case. Did they say how much adding clay damped down the output of the basket?

[birodisco]

Greetings of Portugal!

i have B&W DM6 (pregnant penguins). The mid and tweter units are separeted from de 10" woofer both in close box, like the big brother 801F, The diference is the concrete head for the mids. I'm thinking on damping only the mid and tweter area with plast-i-clay, my doubts is if when using only plast-i-clay in a part of the loudspeaker, if it loses the integrity between the units.

I change the damping of the mids area with visaton wool, use low capacitance wire and new capacitors with good results.

Thanks and regards