Best example of room treatment on the web IMO

[Thomas savage]

i just bought some deep shag... thanks amir

i already have a rug but its thin so will give the deep pile a go...

 

[amirm]

Listening tests show that floor bounce causes coloration. That coloration though was above 500 Hz. So you need something that starts there and goes to limits of audibility.

Here is a simulation I ran on a 25 mm/1 inch absorber. The graph shows amount of absorption at every frequency with 1.0 "alpha" being perfect absorption:

As you see, it starts absorbing around 200 Hz and by 1000 Hz it is in full swing.

Here is what happens when we cut the thickness to half inch/12.5mm:

Now absorption barely starts at 500 Hz and we never achieve perfect absorption.

Last is quarter inch or 6 mm:

This is why you don't want to cover all of our walls with fabric as some people do in home theaters. You effectively will be putting an EQ in the system with the above shape, absorbing a lot of your mid to high frequencies, resulting in a very dead room.

This is why Shag carpet if you can deal with its look is so good. Otherwise put a porous pad below the carpet to give it an air gap.

 

[Thomas savage]

i used to used a big sheep skin rug made by mountain people from poland.. that was too much though and deaden the room imo but i loved it. i dont like absorption on side reflection zones either.

nice graphs, all rugs should comes with this type of info as standard, whats wrong with the world

 

[Thomas savage]

hey amir i indulged myself with a quality modern shag in my living/hifi (really only hi fi as i chucked everything else out) room... i did not measure but it seems more effective than my old asian one. how about a before shag and after shag graph? so we can see just what effect this simple cheap thing can have?..

 

[Purité Audio]

European shag was it?
Keith.

 

[Thomas savage]

did not ask, it was a cheap shag though..

 

[amirm]

hey amir i indulged myself with a quality modern shag in my living/hifi (really only hi fi as i chucked everything else out) room... i did not measure but it seems more effective than my old asian one. how about a before shag and after shag graph? so we can see just what effect this simple cheap thing can have?..

It won't be easily measureable. Once the sound leaves the speaker, it will many surfaces. What then arrives at the measurement microphone is a mess. Here is the example from my article on perceptual effects of room reflections: http://www.madronadigital.com/Library/unfiltered-response.png

The effect of the carpet is at 500 Hz and above. Look at the mess we have on our hands there from measurement point of view. And this is what one ear may hear since we have one microphone. The second ear would hear a completely different waveform. The brain analyzes that and figures out what it is hearing.

For frequencies above a few hundred hertz the rule is that acoustic measurements tell you very little about what you hear!

Instead we must rely on results of listening tests and follow the conclusions blindly. Floor reflections are not good and require thick carpet to absorb them. That is it. No need for measuring before and after.

Now there is a cool set of measurements in an AES paper on absorption coefficients of various carpets and underlayment. Here is one of the graphs:

As you see there are large variations mostly due to how porous the substrate is and how thick it is. The carpet alone had the least absorption.

Ultimately though you are not going to find such data for any carpet you buy so best advice is what I gave: get the thickest carpet+substrate you can get.

 

[Thomas savage]

thanks amir, i left my old asian rug underneath.. better shag = better sound.

 

[NorthSky]

 

[Chuck Gerlach]

I have a combination of GIK and DIY and it sounds (and measures) incredible. BUT, there is no room treatment I am familiar with (ASC, RPG, DIY and GIK - I was an RPG dealer for a while) that will completely deal with most bass problems to the extent that room correction (and multiple well placed subs) can not improve upon.

Love this demo clip, by the way.

 

[Ethan Winer]

If you have enough bass traps, and they're good bass traps, you can get excellent bass with one hefty sub and minimal EQ. This is the response and ringing in my 25x16 foot living room home theater with a large number of bass traps. My SVS subwoofer has a one-band cut-only parametric EQ, which is set to reduce the 2nd order mode at 44 Hz by -3 dB.

--Ethan