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17 Posts
Discussion Starter · #1 ·
Hello new friends :)

I was a two channel guy until recently and I've caught the HT bug. I just bought a new house. I've decided to raise aesthetics in terms of priority with the new place, so the alpha 50's and subs on the floor have got to go. This is evidenced by me giving up on life and going with on-walls for mains :-( I am still interested in achieving flat bass response though.

In an effort to keep black boxes off the floor I bought two salamander 303's and had a couple of black walnut pieces made so I'd have a place to put the subs basically inside the cabinet, on the floor. Let me deal with killing the rattles. That's not what this discussion is about.

Here is the old setup in the loft when I was running Kappa 5.1 for mains and Kappa video for center. That center wasn't great BTW.

Room Living room Interior design Furniture Building

Here is the new setup.

Furniture Property Room Computer desk Chest of drawers

My question is this. Is this location a decent place for the subs? I need to answer this question because I spaced that custom shelf to fit either two uls-15 or a single seaton F2 between the salamander 303's. I want to make sure there aren't massive nulls I won't be able to overcome before I spend coin on subs to go there. Obviously I can test with my current subs before I pull the trigger. SO!, I got a UMIK-1 and REW and set about testing. I have the Dayton UMM-6 from Cross Spectrum also but I haven't used it yet.

Let's talk about these graphs! Setup is in signature.

White Text Line Plot Diagram

The first night I did a couple quick measurements. The blue line is with audyssey off and the green line is with audyssey on. I was very pleased with this! I thought to myself, I'll get a mini-dsp to clean this up a little bit before audyssey and I should be in good shape!

The next night, everything I did resulted in a line similar to the red line! Big null around 55hz no matter what I do. What the heck is going on!? I'm moving furniture back to where it was the night before, I'm closing plantation shudders and re-testing, I'm wondering if the mic has gone bad, I'm losing my mind! Then I notice that my subs are on auto on. I turn audyssey off. I turn one sub off and test. I turn that sub off and turn the other one on and test. These tests are the yellow lines. The night before when I tested only one sub must have been on! Both subs individually are tracking the blue line from the night before with audyssey off. I turn both subs on again and again, big null at 55hz.

Let's recap the lines,

blue line : 1st night, single sub, audyssey off (I thought this was both subs on)
green line: 1st night, single sub, audyssey on (I thought this was both subs on)
red line: 2nd night, both subs, audyssey off
yellow lines: 2nd night, each yellow line is a single sub, audyssey off

I would have never figured this out without measurement equipment.

I was able to fix this 55hz null with both subs on and essentially achieve the green line from the MLP by simple closing the gap between the subs. I moved them closer together. Through extensive testing, I've also determined that the sub on the right hand side alone is the best position within the tiny placement options I've given myself :) The position more to the left likes to produce an issue between 75 and 80hz, as evidenced by the yellow line with the deeper hole there on the graph.

NOW! I wrote all this on the forum to ask one question and seek your advice.

If I purchase a seaton F2, or two uls-15, the cones will basically be in the positions that produced the nasty null at 55hz. Do you think the null is caused by audyssey given the speakers slightly different distances (.2 feet), or do you think it's caused by that left cone being in an extremely detrimental location?

As I wrote that question, I just realized I have to get a y cable, get the cone centers of my two abyss in the same location as the seatons would be and do some testing.

I have a headache. You guys are going to ask for dimensions of the room now.

17 Posts
Discussion Starter · #3 ·
Here is some good reading to help answer your question.


Article called "Subwoofers: Optimum Number and Locations" is a great reference.
That was a fascinating and enlightening article. I eventually opted to change sub location because the null between 70 and 80 applies to the center channel there also. I can't have both the subs and the center in that location because I can't get around the null by changing crossover.
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