Christof,
I haven't done any comparitive testing. To find out for sure, you would at bare minimun need to make similarly sized test pieces of MDF, apply the various materials to the test pieces, then using some sort of contact driver attached to the MDF, feed it a signal at it's resonant frequency, and probably with an accelerometer find out how well the different materials attenuate the excitation of the MDF. I think that a proper test would be something along the lines of that.
I have a friend in the acoustics business. I've done some project management for him, and have some exposure to the techniques and materials they use to overcome sound transmission problems. One product that I came across and have used in industrial and residential applications is Symar. It works really well as a sound transmission barrier and resonace damper. Better than you would think. Here is some info on it
here.
Another trick I've tried is 12" X12" Armstrong industrial floor tile. The stuff you can get at the Home Depot in the peel and stick variety. There is a slightly thicker version ( about 2.5 mm)that is not peel and stick. I used this in my prototype AV/3's. I used contact cement to stick it on. I cut them to size with an old blade on my table saw. These tiles are very cheap, and add a lot of mass.
If you had to choose one over the other, ruling out labor and $ as a deciding factor, which way would you go and why?
Again, this was a while back, so I can't tell you with any certaintly if the materials you mention, or if the floor tile trick would attenuate more than the damping layer on the NoRez. However, if you really wanted to raise the performance a bit more, you could do the tile trick first, then add the NoRez. The NoRez has the foam already attached that you need in order to control standing waves inside the enclosure. That would be your biggest "bang for the buck" and kills two birds with one stone. The tile thing is not as easy to work with or apply, but it does add a considerable amount of mass.
Dayglow, do you use additional R-9 style (loose) insulation in addition to the no-rez?
Yes, but we typically use polyfill instead of fiberglass. This is not a method of resonance control, but a tuning method for the waves reflecting inside the cabinet. I'm not an expert in this regard, so I'll refrain from trying to explain any further.
Hmmmm.....Actually, now I'm inspired to do some experimenting with damping. I wish I had the time to do it now, but unfortunately I don't. I have some of the floor tile, I have some of the Symar, and I have some of the NoRez. I might have access to an accelerometer, I have a sinewave generator, but am missing a contact driver. I'll post my findings when I eventually give this a try.
Actually, I've been thinking as I've been typing this, that when I build my OB 7's, that I'll do just as I'm suggesting to you. I'll first apply the floor tile, then do the NoRez on top of the tile to the insides. Bonus.
All these little things that we discuss, bracing, damping, capacitor upgrades, bypass caps, wiring etc....are all incremental methods of optimizing performance. Of course you need a good foundation in the speaker design itself (drivers, crossover design). But, as I've learned over the last few years, you really do yield substantial performance gains from proper implementation. The enclosure is a big deal. I have to admit, that I was surprised to find out, to what degree the enclosure can affect the performance of a speaker.
I would be amiss, if I didn't mention another simple way of vastly improving the sound of whatever speakers you may be listening to. Room treatment!!!
At bare minimum, absortive panels at first reflection points. Then absorption in corners. Bass trapping in corners is a big deal. Diffusion is something that has worked well for me as well. A lot of this stuff you can DIY, and achieve good results. If you overlook this, you are severly limiting what true potential your speaker (and system) has.
I'll stress this. You can thank me later.
You feel like you've upgraded to a better speaker by these simple room modifications. The more care you take, the better the gains. What can you expect? Better imaging, clarity, less fatiguing. Bass trapping really tightens up bass. Without the bass ringing in the room, you get better imaging and clarity from the mids and highs.
To bring this back on topic, I think it is due to these types of discussions that we can, with a bit of elbow grease, realize much better sound from a (AV-3) kit than we can from a commercial speaker with a much higher price tag.
I totally agree.
Cheers
