Foam wedges vs. pyramids; brands

[ap]

Any reason to choose one over the other? Does it matter?

Also, recommend/avoid any particular brands? Does it matter?

[sjoko2]

Impossible to say - everything has its own characteristics, it all depends on your needs

[barefoot]

Because pyramids are bi-directional I would say they might have some marginal high frequency advantage over wedges of equal weight for applications where the foam is close to the listener or mic. Otherwise, alternating wedges will have the same aggregate effect.

Some might disagree, but I'm of the opinion that there isn't really much difference between decent quality foams of the same weight, density and basic material (ester, neoprene). Manufacturers will mess around with various additives and copolymers in an attempt to differentiate themselves from the competition, but this only works on the margins IMHO. And, I'm always skeptical of the NRC data. Even using standard testing methods it very easy to massage the results to look however you want. What they don't tell you is that any slight differences between brands (say equal density, equal weight ester) will be completely wiped out by any deviation from the proximity and mounting methods they used in the tests.

Anyhow, that's my opinion.

barefoot

[frederic]

Originally posted by ap
Any reason to choose one over the other? Does it matter?

Also, recommend/avoid any particular brands? Does it matter?

Typically, most of the foams of equal weight and thickness offer similar acoustical properties.

Darker colors last longer (they hold their color better).

I also recommend Auralex more often than not because its flame retardant. I have a anti-flame psychosis issue

[sjoko2]

Barefoot is right in his observations regarding the viability of tests, be it that one thing I have found is - the cheaper the manufacturer, the more the date has been manipulated.
Some of the cheaper foams I have seen / heard have a useless acoustic performance, given that all they do is absorb / deaden sound, and that is all. They do not "manipulate" the travel of frequencies in a frequency directed, positive manner, like some of the better designs do.

As an example, look at Sonex - which is not the top foam product for nothing, it is simply a better designed, better functioning, longer lasting product that any other on the market.

Another thing - touching on my hobby horse as I detest foam products for many reasons - is safety. Foam releases chemicals over its entire lifespan, nice stuff like formeldahyde. Safety tests do NOT consider the application of foam over entire walls, as is sometimes the case in a studio environment. The cheaper you buy - the worse it normally is.

Finally - I go back to my original statement. Wedges - pyramids - manufacturer - it all depends on your acoustic needs, each has its own characteristics. If you explain your room and the problem you seek to solve, we could all drop some relevant advise

[ap]

I don't really have any particular problem. At this point I'm just pondering the possibilities for improvement. I figured there were some general applications for each type, and possibly some brands to avoid or some good values.

[gnarled]

Originally posted by barefoot
Some might disagree, but I'm of the opinion that there isn't really much difference between decent quality foams of the same weight, density and basic material (ester, neoprene). Manufacturers will mess around with various additives and copolymers in an attempt to differentiate themselves from the competition, but this only works on the margins IMHO.

Way off topic, but....

While that may be true for the various foam products on the market currently (I'm not very familiar with them), additives and copolymerization can have tremendous effects on material properties. Just a couple examples:

PVC is used in a number of different applications. The PVC used in piping is partially crystalline (30% or so I think) which gives it good strength and rigidity. If your pipes were completely amorphous (non-crystalline), well, lets just say they wouldn't work so well. PVC is also used to make the soft plastic on dashboards with the addition of some plasticizers.
Also, polystyrene is used for a lot of applications like styrofoam cups, etc. But if you make an acrylonitrile-butadiene-styrene copolymer, ie ABS, you have an extremely tough, durable rubber used to make shoe soles among other things.
Also, just through manipulating the molecular weight (length of polymer chains), polyethylene can go all the way from a wax, to plastic wrap, to tubing, to a part of a hip replacement implant.

[barefoot]

Yeah gnarled, you're right. I shouldn’t have made such a blanket statement. Still, most acoustic foams do fall into the basic categories of polyester or neoprene and the range of acoustic properties between brands is nowhere near as dramatic as the material properties between something like ABS and Polystyrene.

But thanks for the correction to my overstatement.

barefoot