Ok I just got done spending about 24 hours over the last two days playing with subwoofers. Sean dropped off his Dominator D-10s and tripod on Saturday so I figured I’d just get it done.
I’m including links to an article if found very useful both for it’s content and the links it provides, even a couple to Axiom. Much thanks to Big Daddy at the Blu-ray.com forum for putting all this information together in one place and summarizing it.
http://forum.blu-ray.com/subwoofers/48286-guide-subwoofers-part-ii-standing-waves-room-modes.htmlhttp://forum.blu-ray.com/subwoofers/4366...djustments.htmlI’m not sure how much external validity my results will have for other except in the most general sense which is actually one of the most important findings I made. The picture below shows the basic layout of my room(s). The brown block is my seating, purple line is the screen, green dot is the best single subwoofer location, yellow dots are other subwoofer locations I tried, red areas measured the worst for subwoofer placement. Besides the odd shape the room also has a vaulted ceiling.
Prior running the subs place my EP500 on the sweat spot and set up a grid on the floor running frequency sweeps using Sean’s HSU CD to find the best single subwoofer locations. After all that work I found that I had already identified 3 of the 4 best locations by ear. However, all was not wasted since the single spot I’d missed actually turned out to be the best one.
For each test I ran frequency sweeps in each seat after the subs had been calibrated for their new positions. I did one sweep with the AS-EQ1 off to see what two subs alone would do and then ran another sweep in each seat with the AS-EQ1 on again with both subs running. For the AS-EQ1 I had to leave the phase setting to 0 since it handles that. For the non-EQ runs I ran a test tone for phase setting on each sub and adjusted the dials accordingly. I also ran several tests with my SPL meter and figured that my margin for error was about 3dB or +/- 1.5dB.
For comparing the overall results of EQ on multiple seats I’m summing the variation’s recorded in each of the 3 seats along with noting any significant other results.
I ran a total of 7 dual subwoofer tests with the D-10s and comparing them only to themselves (i.e. the single sub in the best location the dual D-10s are compared to is also a D-10). I did opposite corners (using two of the best locations), both back corners, opposite side walls in 3 configurations and front and back walls in two configurations.
In every case when EQ was not applied I got worse results with dual subs than with one single sub in the best spot. About half these results were within the margin of error but in all cases the dual subs did worse. EQ improved the results of using dual subs but when compared to the single sub in the best spot using EQ the duals still did worse.
Using the combination I got the best dual results in I put the EP500 in one spot and a D-10 in the other to see how two very dissimilar subs did together. W/o EQ the results were the same as before with the single sub in the best location beating the duals. OTOH when EQ was applied to the two dissimilar subs the results got worse by twice the margin of error.
So what can I conclude from this. Well first read the fine print on using dual subwoofers that says “usually get better results.” Although I’ve only tested one room I’m going to make a leap of faith and suggest that my poor dual subwoofer results stem from a non-rectangular room. Virtually all the math and theory on dual subs is about rectangular rooms. Actually the only thing I ever found to read about non rectangular rooms basically says good luck cause it’s up to trial an error.
Not all of this was a waste of time. It’s saved me the effort of buying another EP500 or other brand of duals (I’m not fond of the changes to the EP500 amp controls). But it does still leave the door open for using EQ which is for another thread:
http://www.axiomaudio.com/boards/ubbthreads.php?ubb=showflat&Number=308860#Post308860
