Room acoustics


How about a thread on room acoustics and ways to improve the in-room performance of your system and its speakers? Subjects covered could be the physics of room response, measurement of response in your own room, and how to deal with imperfections, above and below the Schroeder frequency, like damping, bass traps, speaker positioning, (multiple) subwoofers, and dsp equalization. Other subjects could be how to create a room with lower background noise for greater dynamic range, building construction, or what to do in small rooms.
I am a bit busy just now, but as soon as I have time I will try to kick off with some posts and links.
willemj
@toddverrone

Try to plot RT60 time for various frequencies.

In the bass you should aim for less than 1 and around 0.4 over the rest. Also adjacent RT60 times should be similar - so your reverberation needs to be even to sound right and natural. A larger space can handle more reverb. A small space needs more treatment. There are rules of thumb for RT60 depending on genre and venue space.

See this system thread

https://systems.audiogon.com/systems/4962?page=5

See how I presenrt the 3D waterfall plot in a meanngful way. Your plot is diffcult to interprete.


I'm not sure why mine is difficult to interpret and yours is easier.. I'm new to all this. I just really learned last month what a waterfall plot shows and am just now figuring out how to read it with regards to looking for problems. 

I'll try to make sense of what you just said.. I know rt60 is classified as a measure of clarity in REW, other than that, I'm in the dark. I have lots of reading to do it seems.. I'm certainly not expecting any of you to explain it to me, so I appreciate all comments. The give me things to learn and figure out.
@toddverrone

I rotated my 3D plot so you can see well the time axis. Your time axis comes almost straight out of the page...


Here is a good resource.

http://www.bobgolds.com/RT60/rt60.htm



It has a table at the bottm of the page specifying recommended control room RT60 as a function of room volume. This is a fairly dead control room and the specifcation can be relaxed below 200 Hz and audiophiles will probably prefer something higher or more lively (up to double in RT60 specified)

Key takeaway is that SMALL rooms require gargantuan amounts of absorption treatment!!!!!!! A shower stall is terrible except to sing to yourself....

V in ft^3 V in m^3 ITU RT60
63 1.8 0.07 (shower stall - waterproof acoustical treatment required?)
1000 28.3 0.16
1250 35.4 0.18
1500 42.5 0.19
1750 49.6 0.20 (approximately 16’ x 16’ x 7’)
2000 56.6 0.21
2250 63.7 0.22
2500 70.8 0.22
2750 77.9 0.23
3000 85.0 0.24
3250 92.0 0.24
3500 99.1 0.25
3750 106.2 0.26
4000 113.3 0.26
4250 120.3 0.27
4500 127.4 0.27
4750 134.5 0.28
5000 141.6 0.28
5250 148.7 0.29
5500 155.7 0.29
5750 162.8 0.29
6000 169.9 0.30
6250 177.0 0.30
6500 184.1 0.31
6750 191.1 0.31
7000 198.2 0.31
7250 205.3 0.32
7500 212.4 0.32
7750 219.5 0.32
8000 226.5 0.33
8250 233.6 0.33
8500 240.7 0.34
8750 247.8 0.34
9000 254.9 0.34
9250 261.9 0.34
9500 269.0 0.35
9750 276.1 0.35
10000 283.2 0.35
11000 311.5 0.37
12000 339.8 0.38
13000 368.1 0.39
14000 396.4 0.40
15000 424.8 0.40
16000 453.1 0.41
17000 481.4 0.42
18000 509.7 0.43
19000 538.0 0.44
20000 566.3 0.45
22500 637.1 0.46
25000 707.9 0.48
27500 778.7 0.50
30000 849.5 0.51
32500 920.3 0.52
35000 991.1 0.54
37500 1061.9 0.55
40000 1132.7 0.56
50000 1415.8 0.60



Sweet Lord, that post will take a while to decipher. Thanks!

I just wanted to post back that my first limp membrane absorber is a smashing success. It's very deep (14") but only 10" wide and 16" tall. It's like a good size monitor speaker cabinet. I used thick vinyl for hot tub covers and used polyurethane caulk to glue two layers together, as an increase in membrane density helps to lower the effective frequencies the absorber works on.

I'll post graphs later, as I'm about to head out to dinner, but, subjectively, my 3 note bass problem is, if not gone, greatly reduced. Objectively, I have almost all bass frequencies dropping below 40db by 300ms. 

This is good fun. Sorry I seem to be the only one posting questions on this thread. I definitely appreciate your input, @s