John Sayers' Recording Studio Design Forum Archive

I'm finishing up my gobos and have one question regarding the placement of insulation (in this case rockwool) behind the slats in a slat resonator.

The SAE site shows insulation right up against the slats themselves with an air gap behind that. I remember reading something saying that having the insulation touching the slats would inhibit their resonation and reduce the effectiveness of the absorber. My initial plan was to place the rockwool at the back of the chamber and have the air gap between that and the slats. The fabric behind the slats will obviously touch them but I don't think this will have a detrimental effect.

Hopefully someone is out there with a quick answer as I am cutting the slats right now!

Here's the previous thread with the designs posted:

http://johnlsayers.com/phpBB2/viewtopic.php?t=861

Thanks,
bassman

Closest thing to expert comment I know of -

http://www.johnlsayers.com/phpBB2/viewtopic.php?t=132

The fabric behind the slats NEEDS to touch them - the path between slats has to be through the cloth.

The insulation isn't critical, you could just fill the box with scraps of loose bats or scraps of rigid fiberglas. It's only there to break up the space and dampen the response of the cavity some, as near as I can tell. I'd tend to use cleats and fix the rigid fiberglas at midpoint between front and back, caulking to avoid rattles... Steve

Well, at least the fabric is touching the slats. From reading the other thread, the variation in slot width did nothing but change the average perforation percentage yeilding not a wide band absorber but a higher frequency resonator absorber. The fabric widens the Q of absorbtion but only around a certain frequency.

I think this will work out fine in the end since the holes we cut out in the center and covered with Luon are acting as a lower frequency diaphramatic absorber. Its neat to hit them like drums and hear it ring before we put the rockwool in. Then it all went dead.

The wider gaps should also provide a bit more difusion than the narrow 1mm gaps. We'll see how they work in the end.

-bassman