Endcaps, Part II. Damping (1 Viewer)

[Jedd]

Searching throw the archives and web I found this article:
Panel Vibration Damping Experiments

The damping layer for the green curve is 2 layers of 30# roofing felt that costs $0.17 per square foot (thanks to Dickason for mentioning this stuff). The constrained layer of roofing felt reduces the peak vibration by almost 20 dB, and the average by about 10 dB, relative to the blue curve without a damping layer. In most regions it is better than the hi-tech pricey vinyl. Needless to say, I chose the roofing felt sandwich for my enclosure construction.

Although he is talking about full range speakers here.
Are there any damping materials that can help with vibrations in the sub land?

 

[ThomasW]

Are there any damping materials that can help with vibrations in the sub land?

Not necessary for tube sub endcaps.

 

[Jedd]

I plan to use machine screws to connect mdf and birch pieces of my endcap. I was warned that screw-connection might cause some excesive vibrations. So I'm looking how to decrease them.

Another question. If I decide to glue over the screw, what glue do I need? I've read that softglues do the best for birch to mdf connection. Are there any specific brands you can recommend?

 

[Ron D Core]

I can't imaging how screws will cause excessive vibration. I've always used a few screws to hold sandwiched mdf together. With a sonosub you only need to increase the thickness of the end-caps and run 3 or 4 all-threads across to help hold it together. Some people like to dampen the rods with something like a tight wrapping of polyfill or some tar, but its not really worth stressing over. And I'm not a big fan of spending a lot on glue, it will all do what its supposed to. I just use Tight-Bond or Pro-Bond from Home Depot. I like to destroy boxes with an axe when I'm done with them to scare my neighbor's kids, and I have never had the layers split apart without the wood itself splitting first. When you do glue them together though try spreading the glue evenly over the entire surface with something, and either put some screws through it or a few sandbags to get the panels as close to each other as possible. The more it acts as one thick piece the better.

 

[Jedd]

Well, if someone has positive result using screws only, I would do my endcaps this way. (they still will be glued to sonotube).

Ron, do you use screws only to keep mdf together or it's screws + glue?

How necessary are thread-rods? (and what are they?) My tube is 24" long only.