[WGH]

I'm a big fan of speakers that have very inert cabinet sides, they can have tighter more controlled bass for their size, image much better and seem to disappear into the room. Unfortunately most speakers are built to a price point because bracing is labor intensive to install and a heavier cabinet makes the speaker expensive to ship. Audiophiles who build their own speakers or are willing to open up their boxes can easily improve their sound quality by adding Richlite resonance control panels.

I first discovered Richlite in Oct. 2009 when I modified my Von Schweikert VR-2's and was amazed by the improvement. Since then I have retrofitted Richlite into a couple of Audio Circle members speakers with the same positive results. You can read my original review in the link below, it includes a link to "How to design a low distortion speaker cabinet by Albert Von Schweikert" and a photo of the triple wall laminate construction now used in many of his latest speakers.
http://www.audiocircle.com/index.php?topic=72808.0

Richlite is made from layers of recycled cardboard or cellulose fiber and phenolic resin. The photo below showing the layers is from the sample kit, Richlite is impossible to break and would never look like this if you could break it.



Richlite is dense, it weighs .0439 pounds per cubic inch, a 6"x6" square of 1" Richlite will weigh 1.6 lbs. The great thing about Richlite is that it can be cut with a carbide tipped triple chip blade or a band saw so anybody can use it.

I have been using Excel XPRESS Gel Polyurethane Adhesive. The glue is thick enough not to drip, foams as it sets so it fill any gaps and stays slightly flexible after it dries. I use hot melt glue at the corners to hold the panels in place until the glue dries.



You can see the thin foam line in the closeup below



Lately I have been thinking of using Green Glue as a Constrained Damping Layer. It may damp the cabinet sides even more.



Richlite comes in many colors and thicknesses, I have always used scraps I bought our local supplier but a lot of cabinet shops use Richlite and probably have scraps laying around. If you do have to buy retail order the R50 Medium Brown, it is the cheapest.



Have fun.

Wayne

[Speedskater]

Constrained Damping Layer (CLD) works best when both panels are the same. 
That is, a CLD of 1/2 inch wallboard - Green Glue - 1/2 inch wallboard, will be better than a CLD of 5/8 inch wallboard - Green Glue - 1/2 inch wallboard. 

[Tone Depth]

The approach Wayne is taking, uses dissimilar materials with different resonant frequencies, and different densities, to damp transmission of vibrations through a speaker enclosure formed with composite walls.  I've observed the great results he is achieving while music is playing, both in feeling through my fingertips absolutely no vibrations in the walls of his vented speaker enclosures, and markedly reduced vibrations in the walls of my sealed speaker enclosures, which he helped me with.

Even more important is the improvement in the sound while the speakers are playing.  More efficient damping of vibrations reduces the distortion created by the resonances of the enclosure, on the sound produced by the speakers.

Part of the function of the glue layer is to convert vibrations from the walls into heat, and in this manner a thicker layer of the Green Glue may be more efficient at this than a thinner layer of the polyurethane adhesive.

I'm not certain if the theory predicting the performance of this approach is fully developed.  Regardless, the audio results are readily observed and perceived.

Your photos look good, Wayne.  A great start for this thread.

Constrained Damping Layer (CLD) works best when both panels are the same. 
That is, a CLD of 1/2 inch wallboard - Green Glue - 1/2 inch wallboard, will be better than a CLD of 5/8 inch wallboard - Green Glue - 1/2 inch wallboard.

[richidoo]

Thanks for the info on Richlite and XPRESS Gel. Looks very interesting!

Last summer I built some speakers in MDF, and with minimal structural bracing they had noticeable resonance. I laminated on another layer of 18mm MDF to the outside with Green Glue and noticed a big improvement in sound coloration from the box. It was not totally dead, but much better.

This summer I hope to try it again with 3 layers of 1/4" baltic birch plywood, laminated with 2 layers of green glue. BB is much stiffer and I think the resonance is a much higher Q, at higher freq, so it should be easier to damp than MDF. It is an expensive and time consuming process, but keeps me out of jail.   I used a sawtooth notched trowel to spread on the green glue, leaving a 3/4" strip around the edges masked off. Then peel off the masking tape and join the panels with a few staples at points of minimal vibration (structural braced spots.) When the panels are joined the gap is <1/16", so adhesion prevents the wet green glue from oozing past the clean strip on the edge. It does thicken over the first few weeks, but never totally dries. 

According to bpape, denser materials like sheetrock, MDF, birch ply are better for the green glue treatment. One of the panels should be permeable to allow the green glue to dry. Richlite being phenolic resin composite is probably not very permeable.

[WGH]

I have never used Green Glue but from the video it looks like it never dries hard. Check it out:
http://www.youtube.com/watch?v=LiUBxjFG53o

Laminating with Green Glue might make for a light weight non-resonant cabinet, take photos if you can, it would be interesting to see.

I think you would get equally as good results by adjusting the cabinet size to allow for 3/4" or 1" Richlite applied to the inside along with plenty of bracing, it would make a very heavy box for it's size. The speaker cabinet would certainly be easier to build. I used 3/4" and my cabinet sides are pretty dead sounding with a knuckle rap test.

Wayne

[Speedskater]

While it is "Green" in color it is not a "Glue" in any sense.
It has no adhesive properties. 

[Vapor Audio]

While it is "Green" in color it is not a "Glue" in any sense.
It has no adhesive properties.

Haha, I'm guessing you've never used it.  Green Glue definately sticks two flat panels together very well and for a long time.  Since it never hardens, the two panels aren't rigidly coupled, but that's a benefit in a case like this. 

Wayne, what sort of forms is Richlite available ... and what sort of sq/ft pricing does it run?  I've used canvas phenolic and G10 thermoplastic in speaker builds, but always have to get it cut by somebody with proper equipment.  Being able to cut this myself would a big help.  But if prices like this are typical, that would pretty much rule it out

http://www.katom.com/067-1930222.html?CID=GoogleBase2

[Steidl Guitars]

I love Richlite--it's what I used for countertops on my recent remodel--but it is spendy stuff! 

[Vapor Audio]

If it is as pricey as my quick Google search would indicate, why not just use economy grade paper phenoic?  It can be had for about 1/2 the price ... although still about 4x the cost of Baltic Birch.

[Steidl Guitars]

I just checked and for 1" material, I paid $35/sf.

[richidoo]

The idea of different materials damping each other's resonance is key. Albert's paper has me thinking 3 layers of the same stuff may not be ideal. But then again, green glue is pretty powerful. Only one way to find out! 

[WGH]

Yes, it is pricey. The 1/2" thick scrap I used on Tone Depth's speakers was $11.66 sq. ft. The supplier gave me a price of $25 sq. ft. for the 3/4" thick, that is why I suggest scrounging around for scraps. There are sink cut outs and cut offs around, you just have to find them. A buddy ordered 2" thick Richlite for a counter top because the customer didn't want a built up edge, I bet that was expensive, he said the top was unbelievably heavy.

Contact your distributor for a cool sample box to play with.




Wayne

[Speedskater]

Haha, I'm guessing you've never used it.  Green Glue definately sticks two flat panels together very well and for a long time.  Since it never hardens, the two panels aren't rigidly coupled, but that's a benefit in a case like this. 

No ,I never did an installation.  I thought that it was sticky like peanut butter but not like real glue.