Eggshell foam and terminal cups?

[uncle sam]

Hey guys, does anybody know where I can find eggshell foam and high quality terminal cups in the Johannesburg area. I have tried looking at material shops for the foam, but alas, no luck! I have also found many places who stock terminal cups, but they are all those crappy cheap spring loaded things 

[GearSlave]

Talk to Alex on the forum.

His website is www.audiosa.co.za

Cheers

Gert

PS, how did that mic work out?

[uncle sam]

Thanks for the info Gert, I'll get hold of Alex.

The mic is working out nicely, it is just what I needed. Maybe in the distant future if cash flows allow, I'll go for the full Behringer setup with phantom power supply etc., but for now, the Marantz is perfect  Thanks a million for that agian man!

[GearSlave]

Excellent! Only a pleasure!

[Hi-Phibian]

Turnkey Multi Media and Music I think on Hans... Malibongwe Drive sells fancy imported foam for "studio" use....

[uncle sam]

Thanks croak, I'll check that out also.

[Timber_MG]

The favoured stuffing isn't foam but plyester stuffing as encountered in duvets. just for reference: Havign some stuffing in the middle of the enclosure is much, much more effective that stapling some to the enclosure wall. Has to do with the fact, that at the boundaries of an enclosure the acoustical wave is a pressure maximum and a velocity null, damping (simplified) in a volume depends on resistance and velocity, which exists in the inner of an enclosure and not on its boundaries.

[uncle sam]

The favoured stuffing isn't foam but plyester stuffing as encountered in duvets. just for reference: Havign some stuffing in the middle of the enclosure is much, much more effective that stapling some to the enclosure wall. Has to do with the fact, that at the boundaries of an enclosure the acoustical wave is a pressure maximum and a velocity null, damping (simplified) in a volume depends on resistance and velocity, which exists in the inner of an enclosure and not on its boundaries.

I hear what your saying here man, but I was interested to try the eggshell foam because I have heard of some guys who have had some good results with it.  I don't suppose you have a link to a site that further explains what your saying, I imagine it could make for some very interesting reading. 

[Timber_MG]

Study wave theory. In school you may have seen a sinusoid transversal wave that has two fixed points at the end of it (example pluck a steel/nylon string on a guitar). The velocity (movement of medium, in our case air) is at a minimum at the boundaries and at harmonic intervals (you can put your finger=resistance there but the wave propagates pretty much unaffected). Put your finger on a point on the wave where it excites the medium to move and you damp it much, much more effectively.

Read up on waves (and specifically standing waves which represent he case of a resonance) here http://en.wikipedia.org/wiki/Wave

Enjoy

It is a case not of what you use, but of how you use it and in damping a resonant system loction makes much more of a difference.

[uncle sam]

Cool, very interesting, thanks very much man!

[Hennie]

What Timber says about stuffing and flow resistance is true, however it is possible to provide energy absorption at the enclosure walls. It just needs to be pressure dependant. This is the rationale for using foam – the foam stuffing used in commercial speakers is normally of a closed cell type so it does not provide much in terms of flow resistance anyway. It is there to provide pressure sensitive energy dissipation.

Hybrid, multi-layer pressure sensitive materials for speaker enclosures are commercially available. For example, “Black Hole” provides pressure sensitive foam layers for absorption, together with a visco-elastic layer for panel vibration damping. By using different layers of materials “Black Hole” is tuned to provide more absorption in the critical mid-band frequencies you normally find in enclosures.

I would expect egg crate foam to provide at least some pressure sensitive absorption, but my gut feel says the absorption bandwidth would be reduced compared to a composite product such as “Black Hole”. And it would probably depend on foam density and thickness..

Form the above we can deduce that the optimum damping strategy would contain both elements, i.e. flow resistance and pressure sensitive absorption.

Black Hole:
http://www.zalytron.com/

Sonic Barrier 3-layer, more or less equivalent to Black Hole,:

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=260-535

Acousta-Stuf:

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=260-317

I expect Acousta-Stuf to be a bit more effective than Dacron. Whether it's worth the trouble of importing I don't know, but it is very popular in the US. I have not used the Parts Express products, but I have used Black Hole with ordinary Dacron and that combination gave me the most effective damping. If you don't want to import, try egg crate foam together with Dacron or similar.

[uncle sam]

Thanks for the extra info Henni, that Blackhole stuff looks very interesting, not too cheap either!

[Hennie]

Yes it is, unfortunately. And it does not perform miracles, more like a worthwhile improvement over ordinary foam.

Why not try a reasonably dense 1" layer ordinary foam, with Dacron or similar in the centre.

On the subject of terminal cups, I did once see some nice ones at Yebo Electronics. They were gold plated and looked like copies of the Bennic cups, but were still good quality. Strangely, I could not find them on their website. They weren't bi-wire compatible though.

[uncle sam]

Yeah, I think I'll try and get my hands on as many different types of damping as possible and just try all different combos and see what works best.