[doggie]

Don't tell anyone but today I applied a lot of Mortite rope calk to the baskets of my Super 6 Alnico's and the result was impressive. Much better resolution and localization.

[RDavidson]

Millersound uses strips of Dynamat. The effect is impressive, especially with old drivers that have stamped steel baskets.

[WGH]

Glad you made the discovery.
Frank Van Alstine wrote about damping speaker baskets way back in the January 1982 issue of Audio Basics Newsletter
http://www.avahifi.com/index.php?option=com_content&view=article&id=85&Itemid=181

In 2009 Frank wrote:

Years ago I did the plasticlay thing at B&W at Worthing, England in their sound lab.  They let me use a matched pair of new B&W DM6 small high quality bookshelf speakers.  I pulled the woofer from one and gave it (and the back of the tweeter) the treatment and put it back together. I had brought 1/2 pound of the stuff with me on the trip just hoping for the opportunity to show it to them. Since they were even matched cabinet grain, nobody, not even me, could tell which was which.

We took them into the playback room and set them side by side and ran their test music through them set in mono.  The group there (a freebee tour group of American dealers) along with several B&W engineers, all sat in and made notes regarding first, was there a difference, and second, if so which one was "better".

The results were nearly unamious in favor of the plasticlay treated one.  I opened them up afterward to find out which was which.  Later B&W put this concept into production on some of their first generation Matrix series speakers (not the 801 or 802).  The engineered the metal frameworks so they could pour damping material into the frames in production and have it set up permanently.  Unfortunately, the used a silicon like rubbery damping material that violated Van Alstine's famous damping material rule  "meatballs don't bounce."  So I don't know how successful their results were as I never heard an undamped Matrix speaker of that series to compare with the production damped version.

I know Dennis Murphy finally tired it very recently and did not hear anything worthwhile, but he did not do it double blind and was suspect to start with.

Regards,

Frank Van Alstine

I had good results damping the speakers in my old Von Schweikert VR2's



Wayne

[doggie]

Thanks for the replies. I have done it with speakers before but my Super 6's sound so good that I was hesitant to try to tweak them. Glad I did.

The nice thing about Mortite is that it is cheap, stays pliable for a long time and goes on and comes off easily.

[FireGuy]

Simple question:  If this modification gets good results and is quick and easy as described,  why are the speaker vendors not adding this specification?  Just a question.

[seikosha]

Didn't Louis used to do the past?  I remember seeing pictures of Omega drivers from time to time shown with dampening material applied to the baskets.  I guess he doesn't do it anymore?  Any word on this Canada Rob?

[doggie]

Simple question:  If this modification gets good results and is quick and easy as described,  why are the speaker vendors not adding this specification?  Just a question.

I wondered the same thing. My guess is that as with many tweaks perhaps they are trying to keep the selling price to a certain point? Sorta like why do audiophile level electronics manufacturers not put really well made and effective vibration absorbing feel on their chassis?

It took me about an hour to carefully remove the drivers and apply the Mortite. Well worth it but this would add cost for a manufacturer. I forgot to add that another reason I held off initially adding the dampening is that the Omega baskets are already well made. I believe they are cast metal, not the pressed steel which are more prone to ringing.

I should also add that they are amazing even without the dampening. With a revealing system however it does raise them a notch...

Best,

Paul

[roscoe65]

Didn't Louis used to do the past?  I remember seeing pictures of Omega drivers from time to time shown with dampening material applied to the baskets.  I guess he doesn't do it anymore?  Any word on this Canada Rob?

I have a pair of original super 3's with the Fostex drivers and they were damped this way.  I ordered RS5 replacement drivers and they did not have the putty but rather dampening foam applied to the frame in separate pieces.

[steve f]

I've been using Mortite and other damping materials for years.This is a simple and reversible modification. I've never noticed any speaker sounding worse for treatment. I've even used it on horn lenses with good results.

[Canada Rob]

Looking at the picture, I see what almost appears to be a basket hand daubed with thick clay.  The openings in the back of the basket have clearly been compromised causing more restricted backflow.  I can see dampening treatment being effective on stamped steel baskets, but on a well designed aluminum basket I think this kind of treatment would be less effective.  This, like with many changes such as speaker wire and interconnects etc, the sound may well be changed, but not necessarily improved on a purely objective basis.  However, if the change brings to you a perceived improvement in sound, then go for it.  Just keep in mind: is it totally reversible for the sake of resale or warranty?

[WGH]

Looking at the picture, I see what almost appears to be a basket hand daubed with thick clay.  The openings in the back of the basket have clearly been compromised causing more restricted backflow... However, if the change brings to you a perceived improvement in sound, then go for it.
Just keep in mind: is it totally reversible for the sake of resale or warranty?

The restricted airflow didn't even cross my mind, maybe so but probably minimal. Plasti-clay never hardens so it is always removable. If I ever had a warranty it was voided by all the other mods I did to the speakers long before I added the clay. The good news is I sold the speakers a couple of years ago.

[avahifi]

After the demo I did for B&W year ago, their engineers told me later that they were shocked to find that the resonances from their high quality CAST speaker baskets were only 10 dB down from that of the active cones themselves.  They said my damping treatment took that down to -40 dB or better. They use a laser interferometer to measure system resonances.

I have no idea why they quit.

I do suggest plastic modeling clay rather then mortite as I have been informed that mortite may give off some acid fumes that could degrade voice coil wires.  Plastic modeling clay is inert and never drys out.  It is available in several pound blocks at hobby and craft stores.  Judicious heating in a microwave softens it for easy application.  Too much microwave time however leaves you with a pool of goo.   

I have not done this to my current speakers, just too much lazy mental initiator to try it I guess.   

The way to try this is to do one speaker and then compare the pair in mono, side by side.  Be careful not to block vent holes or airflow.

Regards,

Frank Van Alstine

[steve f]

Thank you Frank. I had never heard the negatives about Mortite.
A lot of audiophiles tend to go overboard on modifications. I've found that rather nominal amounts of material work very well.

[planet10]

I have been used duct-seal since the late 70s to damp baskets (and shape the rear exit).

2nd half of this article:

http://www.t-linespeakers.org/design/tweeks.html

dave

[monsterbill]

Here's what someone else did to dampen his fostex:  http://diyaudioprojects.com/Drivers/Fullrange-Modifications-Tweaks/

Likewise, Louis used to dampen both the backplate and the basket of the fostex drivers, but now only dampens the legs of the basket.  Perhaps the new baskets are less resonant?

[vinagunner]

v

[Mark Korda]

Hi, I was one of the first subscribers to VanAlstines Audio Basics. It made the hobby more fun than ever. I used the clay in all sorts of new ways. One that Frank suggested was also the inside of the cabinets except the front could be lined with clay. I did that to 2 pairs. One was the little Boston Acoustic 40, long gone, and a pair of monitors I made from Woodstyle 802 cabinets. 16 in. by 10 in. by 8 in. deep. The size of a pair of LS3/5A monitors. I kneeded the clay by hand, a great workout and added 20 pounds to each speaker. After the clay lining was done I used 3 sections of (egg crate) foam rubber for the internal stuffing. The way I fit the pieces in seemed to abut the clay perfectly and I did not need any staples. This I think allways kept the internal clay put. I had a fear the clay might loose it's adherency with the wood....Not!...those monitors are still mint and playing as I speak. There heavy but every once in a while I give them the shake test with 2 hands and their always rock solid. Just you clay interested guys and Frank ought to know. I built these speakers in 1989 ,26 years ago.....Mark Korda

[doggie]

Great thread. Thanks for all of the input!

[Mark Korda]

Hey Doggie, Here is another fact about Mortite which I observed. I just moved from a tiny studio apartment that I lived at since 2000. I live in Maine and had to pay for my own heat so I put a lot of Mortite in my old leaky  bay windows. When I finally moved a couple months ago the Mortite in my window cracks had started to dry out. That was 15 years in the sun and the wind it was blocking doing this. The same roll,out of the box,sitting in a box of tools was just as plyable as the day I bought it.I used it recently for a woofer and tweeter gasket on a pair of Dynaco A-25MK2's. Boy does it make things easier for gaskets and the sound improvement is superb. There is a well respected Audiophile named Wayner who does not like Mortite, he works with Frank and is a great guy!, but these are my observations on Mortite. As a window glazier I prime bare wood sashes before I apply linseed oil glazing. This prevents the sash from sucking up the oil in the glaze and drying it out too fast. This may have happened to someone who used Mortite on bare wood which my windows were like where the old paint had chipped off and I stuffed the Mortite in....get along Doggie...Mark Korda

[doggie]

Thanks Mark. My roll is easily 10 years old and just as pliable as when I bought it. I also have used it as a gasket for speaker drivers.

Best,

Paul