Finding the Listening Position
by, 01-10-2012 at 01:11 PM (1045 Views)
As mentioned in my last blog I've begun the process of optimizing my current 2-ch rig which is computer based. Step 1 was to determine the best listening position in my room:
I rolled up the area rug and moved as much out of the room as I could. I'd be using a Behringer DEQ2496 for it's RTA (Real Time Analyzer) functionality along with their ECM8000 measurement microphone and a cheap (but adjustable) mic stand.
I'd be playing test tones from the Rives Audio Test CD2 which is still available for purchase on their website for $21. This disc was ripped in iTunes to 16/44 AIFF. My speakers are only rated down to 45Hz so I simply created a playlist named after the task at hand and used (the uncorrected) tracks for 40Hz through 315Hz. Why up to the upper-bass/lower-midrange? It's what I've found through my research the point where the room's modes trade off to it's other issues (ie reflections).
Starting at the back of the room I measured between the two side walls and marked the mid-point every 12" with a small piece of blue 1" wide painters tape. I did this just in case the walls weren't exactly parallel and to make sure I had a straight line to serve as my reference.
Once that was down, I connected them all with one long, continuous piece of tape. There are numerous ideas about "where to start" but the consensus for a near-field setup like mine was almost unanimously at the 38% point from the front wall where the speakers would be placed. This was something like 52.5" for me. I marked it off with a 12" piece of tape that ran perpendicular across my "mid-point" tape. I then marked that mid-point tape in 3" increments from that 38% mark and labeled them A-Z (front to back). Mark "E" ended up being the 38% location to give you some idea. This put marks A-D closer to the front wall and F-Z going towards the back wall.
I put the speakers on stands and pushed them completely into the two front corners in order to excite the maximum amount of room modes. I measured the height from the floor to the midway point between the tweeter and the woofer and then adjust the mic stand so that the mic was at that same height. I used a 4' level standing on end to line up the tip of the mic with the marked location on the tape and began measuring. I took 260 measurements in total (10 frequencies x 26 locations). Initially I calibrated it so that location "E" measured 85dB at 100Hz and got to work.
So I learned several things about my room and my speakers during this process among them:
1. My speakers DO roll of quickly below 50Hz. The average dB was 84 at 50Hz and down to 75 at 40Hz. The highest measurement I got at 40Hz was 79dB at the very back of the room.
2. Peaks were almost consistently at 80Hz and 200Hz but weren't terribly off of the reference of 85dB @ 100Hz.
3. My smoothest results were in the front of the room.
My absolute best result ended up being at the 38% mark! What are the chances? There I achieved an average dB of 85, +2/-3 from 50hz-315Hz. (At this location my 40Hz measurement was 72dB.)
Locations C,D,F,G (6" up or back from E) had decent results as well but with a wider variation from the reference.
So I found my ideal placement for my chair...next it would be on to the speaker positioning.
P.S. I'll try to post pics later tonight.