My acoustic project

[Zerock]

Hi
I just thought I'd start a thread about my audio respons improvement project. This is my first measurements at the primary listening position. The position is 8' off the back wall (About 38%) and slightly off center of the room. The room is a converted garage. There are some photos in this thread: http://www.hometheatershack.com/foru...i-georgia.html

I have a lot of work to do here. It seems almost overwhelming and not sure where to start, other than beginning to treat for 1st reflections:


Red graph is made with front speakers only,
Green graph is both subs (only)

[brucek]

I'll make a couple comments about posting graphs.

It's best to use the standard here at the shack of vertical axis = 45dB-105dB and horizontal axis starting at 15Hz and extending for subs to 200Hz and whatever you like for full range.

With full range measures it doesn't hurt to use 1/3 octave smoothing to reveal the underlying trend of the response that is hidden by comb filtering and to more closely comply with our hearing. Smoothing is not recommended on subwoofer plots though.

It's a bit easier to view waterfalls in the LOG mode rather than LIN mode since that will match the response graph scaling. Then you can move the slider to 1 slice and see the initial response and slowly move to 30 slices and see it ring out.

Hopefully you're not using a Radio Meter for those full range measurements - there not really suitable for that.

Anyway, you're getting some sharp cancellations with your subs and you have a peak around 45Hz-60Hz. Since you have two subs you may be able to use them to support a better response (not that it's too bad now). Try measuring one at a time first to get a feel which one is contributing to any large peaks or dips and them try and get them to work in concert for the smoothest response by moving them around (if that's possible). You may also benefit from equalization with your subs if placement doesn't solve any problems. There's really no treatment that helps at those low frequencies. EQ and placement are your options there.

brucek

[Zerock]

Thank you for the graph tips, I still have a lot to learn.

Yep, I'm using the old RS meter. It's all I have for the near future: I'm using it's CAL file- Is the meter useful at all for a full spectrum?

I did some speaker placement experiments last night- and eager to try some new places this evening.

[brucek]

I'm using it's CAL file- Is the meter useful at all for a full spectrum?

You'll note the cal file stops at 200Hz.

You can use the meter for full range in relative terms, but not absolute.

So if you took a reading at a frequency (for example) of 5KHz and then made a positional change in a speaker to see if it was relatively louder or quieter at 5KHz, then that's fine. You could not say that the SPL reading at 5KHz was correct. The RS meters have been found to be quite different between units.

Most people here use the ECM8000 and XENYX combination mic/preamp. See this thread with regard to where they're available and how to connect up. Fairly inexpensive and effective, and we have a full range cal file available on the download page.

brucek