Visit to Switzerland

Tenson said:
You didn't fancy building your own stands and rack then Chris?
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Stands, no. I've ordered some Target MR70's.

Racks, yes. There's a pile of IKEA LACK side tables on my living room floor awaiting assembly. I need to get the big black slab in from the garage and touch up the paint.

Absorbers. I can't find 25mm Rockwool anywhere. Can't find 25mm high density foam at a sensible price or anywhere locally.
 
I'm also having trouble finding anywhere local to buy materials to build some absorbers.
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Try local builders merchants or insulation suppliers for the rockwool slabs Chris.

Word of caution tho'. Mineral wools (rock wool and glass fibre) give off fibres that are low in bio-solubility. When inhaled they don't dissolve easily causing possible lung irritation so maybe not best suited to the domestic environment if you have children about or are prone to asthma. Sheepswool batts are an alternative but a similar price to acoustic foams.
 
mosfet said:
Try local builders merchants or insulation suppliers for the rockwool slabs Chris.
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I have several local suppliers for 50mm Rockwool slabs but I don't really want the absorbers to stick out 3 inches from the wall (allowing for the all-important air gap). 2 inches would be tolerable.

If I use Rockwool, it will be behind curtain material on the front (sateen) and something cheap with a close weave from behind.

I may have to bite the bullet and buy some acoustic foam. Very annoying when I know it's the same as the stuff they make cushions out of, just three times the price! Case in point - one of the acoustic suppliers wanted £25 for a can of special spray adhesive to stick its foam pads up with. My @rse! I don't think it costs £22 to print a different label on a can of spray adhesive you can buy for £3 down your local DIY emporium :mad:

Anyway, I seem to have hijacked Simon's thread. This was supposed to be about Titian's system :D
 
Chris, from what I understand a 2" solid rockwool slab directly on the wall will work better than 1" slab and a 1" air gap. The gap is very good for improving low frequency absorption but its only really used as a trick to improve what you have without buying more absorber ;)
 
I have several local suppliers for 50mm Rockwool slabs but I don't really want the absorbers to stick out 3 inches from the wall (allowing for the all-important air gap). 2 inches would be tolerable.
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In terms of acoustic absorption 50mm slabs bonded or hung directly on the wall will be more effective than 25mm slabs plus a 25mm air gap.

Using an air gap is a simple technique to increase broadband absorption by placing the absorptive material a distance away from the reflective boundary where wave velocity is higher (at the point of reflection wave velocity is zero and increases sinusoidally after this).

In short thicker is always better and thicker with an air gap better still.

I may have to bite the bullet and buy some acoustic foam. Very annoying when I know it's the same as the stuff they make cushions out of, just three times the price!
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Not the same stuff Chris. Upholstery foams are closed cell. Acoustic foams are open cell; it's this gas porosity that makes them effective acoustic absorbers.

The cheapest suppliers I know of are below.
http://www.mtraudio.com/
http://www.studiospares.com/
 
I think acoustic foam is a lot more complex than normal cushion foam. Besides being open cell there is a lot of attention paid to how well it slows the velocity of air particles. I don't know for sure but I suspect that on a microscopic level it has a very uneven surface to increase air contact. Fibrous materials absorb sound because the small, small hairs vibrate in sympathetic motion to the air and thus use up its energy. There is also surface friction. Foam probably employs a similar technique but is nice because its easy to pour in a mould ;)
 
Tenson said:
Foam probably employs a similar technique but is nice because its easy to pour in a mould ;)
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Most foams are cut from a bloke, not moulded, thats why profiled foams cost more money, those fancy pyramids have to be programmed in!
 
I thought so at first, but seeing some very complex shapes... how the hell do you cut them? A pyramid or something you can do with a straight hot wire but how do you do the other things with complex shapes?
 
Tenson said:
I thought so at first, but seeing some very complex shapes... how the hell do you cut them? A pyramid or something you can do with a straight hot wire but how do you do the other things with complex shapes?
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Our profoam is cut from a block, i think with a wire, its all computer controlled, same with our pyramid profiled stuff, some stuff, like wedges, can be cut easier, as 2 pieces will come out of one thickness easily enough(thats why certain brands have that, its cheaper to produce....)but other things require a block to be cut off, then the pattern cut from that.

ever wondered why there isnt much black acoustic foam in fancy shapes? the blocks cant be made with a uniform colour throughout, so it cant be guarenteed that the colour will be true. If it was moulded, it would be a POP to do, and would cost less. The basic materials are not that expensive(except Basotech), its the designs in them that cost the money to produce
 
titian said:
As you know I built my system specifically for classical music and also the non-electronic jazz.
Since I practically never hear any electronic reproduced music, I wouldn't have a clue what I would change to make that kind of music work perfectly well here. I would very probably throw away most of the stuff and buy a system which would cost one fifth of my actual (maybe even less).
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Any system which can cope with the dynamic range of orchestral music, and reproduce acoustic instruments convincingly, will have a very easy time with anything else.
 
The Devil said:
Any system which can cope with the dynamic range of orchestral music, and reproduce acoustic instruments convincingly, will have a very easy time with anything else.
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That sounds like a fair statement. I find the problems start the moment the electric guitars come in. They are, afterall, pure distortion and can sound quite awful on an accurate system :D
 

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