Tuning speaker / room response?

The graph is actually pretty simple to do. You put it on a web server, then include a link in your post. The link is done by a simple html tag.

Using square brackets in stead of smaller than / greater than signs, the tag looks like this: [img src="http://www.myhome.org/pics/roomresp.gif"]. You would of course use greater than in stead of [ and less than in stead of ].

Niels.

OK, take two of the experiment will thus involve pink noise and a spectrum analyser. I have done a bit of research on linear mics, PC Sound Cards et all, and as it turns out, it is not really economical to turn my PC in to a spectrum analyser. (See other thread on PC Spectrum Analyser).

What I found is that using an osciloscope, I got a nice 1kHz sine wave from a test CD to look as such. When my sound card was done with it, looking at the representation on the PC, there were tons of harmonics. So, I have a spectrum analyser coming to do this right.

So let me describe my room, here is a quick picture:


The black boxes are the speakers, they are actually toed in about 50 degrees. The blue box is roughly where I took the meassurements, and where I normally listen. The room (narrow part) is about 14' wide, about 20' long. Ceiling at about 9'.

The left wall is almost exclusively glass, about 90%. Glass is framed in hardwood. The floor is hand-made tile over concrete. Front and rear wall are drywall. Right hand side wall on narrow part is brick. Front part right side wall open to higher level floor. Ceiling is hardwood boards with beams hanging down at 8' and 16' from the front of the room; beams are hardwood, 4" wide, 8" high.

There is a couch against the back wall, two recliners (one where blue square is, one to the left). There are rugs inbetween the speakers and listening spot, from about 1' left of left to about 1' right of right speaker, another rug between recliners and couch.

The plan for this weekend is to repeat the experiment using pink noise and spectrum analyser. I will perform the test at several points in the room to see what results I get.

Finally, I suspect some people are going to suggest changing speaker placement radically. That is not really an option due to the traffic pattern in the room. I am sure it would be better to move the speakers 3' more out of the wall, but it aint gonna happen. *sigh*.

More data later...

Niels.

Jaycee, thanks for the response.

I ended up buying a different instrument to test with, after some people had pointed out the flaws in the methodology I was using here, and using different test methods. Some of the things seen in the graphs above were artifacts from the RS meter used, but not all.

Using my Terrasonde The Audio Toolbox 2, a handheld, calibrated SPL meter, tone generater, and real time spectrum analyser, I did the tests again with pink noise and slow C weighting. I found that I had a high-frequency and a bass problem. The high frequency problem was mainly caused by reflections from the walls it seems; hanging a rug about 2.5" from my back wall solved most of that. Right now, my in-room response abve about 400Hz is within +/- .5dB! The difference is amazing... Imaging improved incredibly, and the system sounds 'calm' now.

As for the bass problems, I tried building some traps using the mthods found in an article on headphone.com, but I made some calculation mistakes, so they did more harm than good. Then I found the ASC website, they sell accoustical products to deal with room acoustics, and offer a free consulting service. I have provided them with room and frequency response information, and they are working up a solution for the bass problem. We shall see what comes out of it...

Niels.