[Daygloworange]

My understanding is that the acoustical energy needs to be converted to heat via friction in order to reduce the energy.

That's been my understanding as well, as the most effective way.

Thinking over this a bit I am posed with another problem, how the heck would I cut the mdf/tar/mdf without botching up my table saw

Easy. Composite panel construction. For example, two 3/8"  MDF skins, separated by a frame sandwiched around the perimeter of the panels say of a 1/4" thick MDF cut into 1" strips. You fill the area inside the built up frame with your tar of choice, then glue the other skin on. The frame glues the two skins together, the tar is the damping between the field portions of the panels. You've now encapsulated the tar, and can cut the panel without cutting into the tar. Ta Da!

Cheers

[Hank]

I don't think he means liquid tar - he probably means roofing tar paper.
Here's another thought:  I recently sent Danny a test cabinet and one of his comments was that he rapped on a side and it sounded really dead - he asked me what I used.  First, I used the Parts Express damping layer material.  They have 2 versions:  mineral-filled asphalt polymer (p/n 268-020 for example); also a mineral-filled viscoelastic polymer that they claim is twice as effective (p/n 268-035 for example).  They're both peel-and-stick.  I stick that on the MDF (clean it like Al said), then on top of that, I stick the PE 1" thick acoustic foam, p/n 260-525, also peel-and-stick.  No-Rez might be better - I haven't compared.  I'll be interested in your test results, Dayglow.

[Daygloworange]

Hank,

Thanks for the info.

If you re-read Cristoff's latest post, he did in fact mean liquid tar. He also mentioned ice& water shield, which I believe is a tar paper.

The liquid damping method should be the most effective method. Much like harmonic dampers on crankshafts of high performance engines. They are (as far as my most recent knowledge on the subject) by far the most effective at damping harmonic vibrations. I believe this would hold true in a constrained layer method for speaker cabinets as well.

I believe I've read that natural silicone, has very good harmonic damping properties as well.

I have a colleague that has a vibration and sound control business. They are very well established, and respected as one of the leading experts in the field. They do stuff all the way up to tuned mass dampers for skyscrapers. I'm gonna pick his brain one of these days again, on the subject.

I don't know why it hadn't occurred to me before, to consider this method. But that's the beauty of AC. Two heads are always better than one.    

I'm toying with design ideas for a new subwoofer enclosure, to get away from just a plain ol' rectangular box. I was thinking of having built in ballast tanks for sand/lead shot. But now that I think about it, the tar thing would probably be even more effective at adding both mass, and having the most effective damping properties as well.

I checked out the Parts Express stuff you listed. Interesting. I think one of those might well be very similar, if not the same stuff as the Symar I mentioned earlier.

If I actually get around to doing a controlled test, I'd like to try as many samples of dampening materials, as I could get my hands on.

Cheers

[Danny Richie]

Hey guys, the best fill material to use between layers of MDF is sand.

[Christof]

If you re-read Cristoff's latest post, he did in fact mean liquid tar. He also mentioned ice& water shield, which I believe is a tar paper.

I guess I was refering to either.  The ice and water shield is sort of a combination of both.  It has a platic membrane on one side which is not sticky and the other side is a sticky rubber tar type stuff which gets very sticky (not runny) when it heats up.  The sticky side will stick to MDF with no problem, especially if the mdf has a seal coat of shellac applied first.  I'm going to play with it a bit on with a pair of cabinets I'm building and see how it turns out. 

I suppose there are as many ways to creat constrained layer damping as there are to drink a beer or skin a cat, if thats your style.  If the inner box is coupled to the outer box via rigid mechanical fasteners like bolts, screw, mdf (solid corners) or anything other than the "lossy layer", there will be an avenue for the energy to escape because the the layers are not truely independent.  I think to realize the most from CLD there should be nothing but a "lossy layer" between the inner and outer box. 

There has been much discussion about CLD at DIY Audio.  I'm kinda curious about Green Glue used between two layers of 1/2" mdf.  Wilson Audio published a white paper on their CLD experimentation and it seems that a very thin adhesive layer between two identical rigid layers (MDF) worked best for them.  It makes sense after reading the Wilson paper that a thick "lossy layer" will allow the inner panel to be set into motion and have a slow "decay" time, if you could call it that.

I'm toying with design ideas for a new subwoofer enclosure, to get away from just a plain ol' rectangular box. I was thinking of having built in ballast tanks for sand/lead shot. But now that I think about it, the tar thing would probably be even more effective at adding both mass, and having the most effective damping properties as well.

Here is an unorthidox subwoofer I did, following Bucky Fullers "Dymaxion model" stating that as the number of sides of an enclosed shape increases, approaching spherical geometery, the enclosure should become inherently stronger and thus be able to be made more lightweight ie. geodesic domes.....  I cannot imagine how to build this using CLD but if it could be pulled off it would one dead horse.

c-

[gprro]

Hey Dayglow,

If you're looking for damping to test, have you heard about Wispermat 1 or 2. Check out silentsource.com, can't remember if you have to order a minimum amount. I'll probably use the 1 on my new OB's, unless floor tile and foam is just as good. Or maybe the PE stuff.

[Danny Richie]

The Wispermat material is just about worthless. Read the info page on the No Rez to learn why. It is the same type of material as Sonic Barrier.

http://www.gr-research.com/components/no_rez.shtm

[gprro]

even the wispermat 1? Looks like it's just a damping layer then foam. The wispermat 2 I thought was just like blackhole.

[Danny Richie]

even the wispermat 1? Looks like it's just a damping layer then foam. The wispermat 2 I thought was just like blackhole.

Take a good look at the pictures. You will see that they are nothing more than a thin sheet of foam, then a barrier layer, then a with the WM2, a thicker sheet of foam on top. It is just a suspended piece of vinyl. There are no damping layers. Nothing but a foam layer touches the walls of the cabinet. If the enclosure wall is excited at its resonance then foam pad with suspended barrier has little effect on it. The cabinet wall can resonant independently of the barrier.

Blackhole 5 and No Rez both have a heavy composite damping layer that is stuck directly onto the cabinet wall to minimize and control the panel resonance.

[gprro]

Oh, I thought wm1 was like no-rez, Vinyl damping layer (1lb. per sq. ft) that attaches the the wood, then 1 inch foam layer on top. Whats your thoughts on floor tile and foam? I know I shouldn't cheap out, but my budget is tight, specialy considering that I'll probably be ordering 8 of the xbl's when they're in and either save my current 130's for suround speaks or sell them.

quote from whispermat.
Whispermat1  combines a single barrier layer with a single layer of Hushcloth® acoustical foam.  When the barrier is applied to sheet metal, plastic, or wood, the foam is exposed to absorb airborne noise.     
The barrier functions both to contain sound, and acting as a mass damper, eliminates structural vibration.

[Daygloworange]

On the topic of resonance control, I'm building a custom metal stand for my audio gear. The stand pictured below is constructed out of 2" x 2" square tube for the uprights, and 1 1/2" x 1 1/2" square for the crossmembers, all .100" wall thickness cold rolled steel.

All the tubes were drilled and sand filled. Cross members included. The difference in ringing prior to sand filling, and after, is tremendous. Again, I experimented with tapping the tubes with various hammers of different weights, and materials. The sand is a big deal.

Just for fun, a couple of people told me that expanding uerethane foam (the same kind you buy at the Home Depot for air leaks) works well for damping. So I tried that with some spare tube. It actually does work really well at preventing the tube from ringing like a bell.

The other difference noted with this experiment, was that when the stand was flipped 90 deg. on it's side and you were to bang on the legs. The stand actually resonates like a tuning fork. You can actually see it oscillating. After sand filling, the oscillation is greatly diminished, and the duration is much shorter as well. Of course the mass of the sand will do this, while the foam could not.



Just to give you an idea on how much mass sand adds. The stand prior to sand filling weighed 50 lbs. After sand filling, 80lbs. An easy, cheap, and very effective method of mass loading and damping.

I'll definitely be doing it in the future for my new subwoofer enclosure. 

I'm also experimenting with constrained layer damping for the shelves for this unit. I'll give an update on that when I finish those experiments. 

Cheers

[World Leader Pretend]

So I'm looking at building my first set of "real" speakers and am ordering the AV-3 kit.  A few things: 

>For a first-time build should I go with the sonocap upgrade?  I am running mid-level electronics using mostly CD quality music (plus some high bit-rate MP3s).  No HT, just music using Dolby PLII or stereo presentation. 

>What should I use for dampening/mass loading?  I want to keep construction fairly straightforward and inexpensive, but also have good quality. 

>Any additional tips for me about the AV-3? 

I am going to finish the enclosure in a gloss black paint, using lacquer.  I have access to a spray room and gun, but I am not sure what type of lacquer to get for a gun.  I think that the black paint will be from a can, since that is pretty cheap and I have had good results thus far. 

Thanks for the help! 

[S Clark]

You are a lucky guy to be starting into quality audio with the AV-3's .  They are going to be hard to beat for quite a while. I think that most folks buy the upgraded kit.  If you are going to paint the cabinet, there are lots of threads that cover the problems.  Keeping the seams invisible is the main one. 

[Danny Richie]

For a first-time build should I go with the sonocap upgrade?  I am running mid-level electronics using mostly CD quality music (plus some high bit-rate MP3s).  No HT, just music using Dolby PLII or stereo presentation. 

Clearly it will sound better with the Sonicaps, and that added performance does come with a price. Whether the performance is worth the price is something each person has to decide.

What should I use for dampening/mass loading?

No Rez.

am going to finish the enclosure in a gloss black paint, using lacquer.

If so then it will be important that you cut all of you exterior walls with a 45 degree angle so that the seam will be on the rounded edge and easy to hide. Otherwise it is nearly impossible to keep the seams from showing through.

[Daygloworange]

For a first-time build should I go with the sonocap upgrade?

I would recommend that you do. The reason is quite simply, that when you discover how well the AV/3's perform with the lower grade parts, you will not stop wondering how much better they could sound, with the premium parts. It's human nature. Then you will purchase the more expensive parts, and have nothing to do with the parts that you'll be replacing. Those parts that you initially saved money, are now just sitting there unused.

I would also recommend bypassing all the caps with Sonicap Gen I or Gen II's. It'll only add a couple of more bucks to the kit. Bypassing is an easy hot rodding option.

>What should I use for dampening/mass loading?  I want to keep construction fairly straightforward and inexpensive, but also have good quality

I'll again echo that the NoRez works really well. The other methods (like floor tile) will work as well for mass loading and damping, but you would then need to add something on top of that to control internal resonances. The NoRez does both, and is peel and stick. The adhesive really works well. After 24 hrs, there just about no getting it off. Cuts easily with a knife. No muss, no fuss. 

I am going to finish the enclosure in a gloss black paint, using lacquer.  I have access to a spray room and gun, but I am not sure what type of lacquer to get for a gun.  I think that the black paint will be from a can, since that is pretty cheap and I have had good results thus far. 

The advice to mitre the edges will yield you the best results, but certainly much harder to do.

As far as lacquers, it depends on how far you want to go. If this is just a quicky DIY speaker, just to get your feet wet in DIY, then use whatever types are readily available where you happen to have access to a spray booth and guns. Use what they use.
You can run into compatibilty problems when you use multiple products from different manufacturers on the same project. Some problems don't show up right away, but later on down the road, and can be nearly impossible to rectify. You must start over.  So beware of that. The most durable lacquers are of the post catalyzed variety. You must spray these in a booth only, and must wear a respirator. These paint systems are not friendly to your health otherwise.

Read around the GR Research and RAW Acoustics forums, there are plenty of threads where DIY'ers have asked similar advice regarding how to veneer and finish speakers.

Have fun, and don't forget to post pictures.

Good luck! 

Cheers

[Loftprojection]

I went straight with the upgraded kit and Blackhole.  This was my first ever DIY project and I figured that I would put a lot of effort to it so didn't want to take any chance on the potential for sound quality.  I'm sure the base kit is probably very good sounding but if you plan on keeping your speakers for a long time then I guess the few dollars more are well worth it.  I've had my A/V-3 for close to a year now and I haven't been thinking about upgrading my speakers since then, I really love the sound they produce, even more since I added the SW-12a sub.  Have fun with your project.

[slksc]

I am going to finish the enclosure in a gloss black paint, using lacquer.  I have access to a spray room and gun, but I am not sure what type of lacquer to get for a gun.

I also started my AV-3 project by thinking to use paint instead of veneer, mainly because I had no idea how to work with veneer, and the extra cost of veneer was significant.  Now I'm so relieved I went with veneer.  My raw cabinets ended up with a number of dings, screwholes and uneven seams.  I patched and sanded these as best I could with wood filler, but I shudder to think what these things would have looked like without veneer to cover up my mistakes.  If you have a WAF, you'll need to consider that, IMO.

[Blaine_M]

I also went with veneer for the same reasons mentioned above...the cost was higher because the paper backed veneer isn't cheap...but they would have looked like crap if I would have just tried to paint them.  Also do the sonicap upgrade and the NoRez as Danny recomends over the BH for these speakers. 

[Hank]

Wood is beautiful.  Awesome, gorgeous wood grain is available to us thanks to veneer technology.  I would never paint, except for speaker bases.  I had a local customer who wanted a 5 speaker system (2 towers, i center and two surrounds.  He had a strict budget, so veneer was out of the question.  Rather than paint them, I coverred them in the PE vinyl that looks like black-dyed ash.  I didn't have to mess with paint and the customer was thrilled with his speakers.  The lowest cost wood veneer tends to be oak, cherry and maple.

Yes, do the max A/V-3's and you'll have speakers rivalling any audio showroom's $1,500 - $3,000 speakers.

[World Leader Pretend]

Sorry I couldn't reply sooner, I've been out of town for a while.
 
Anyway, I am glad to see all these replies, it is getting me pumped up for this project! 

I will go for the Sonocap upgrade, it seems like a no-brainer now.

I'll figure out the dampening issues later, after I do some more research.  No-rez sounds like the answer but it is more expensive than the drivers.     Convenience may win me over in the end though..

As for the finish, I am quickly realizing that painting may bring tons of troubles, and I would like these to look as professional as possible.  I am (relatively) new to veneers and would appreciate any help as far as suppliers, techniques and types.  I want whatever veneer I choose to be fairly easy to work with and not require tons of toxic chemicals.  Can you guys help me here? 

Thanks!