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I got my SVS PC12-Plus to replace my Polk PSW350. It's a massive difference, and now I'm attempting to tune it for my room. Here is the first graph with corner placement:
pc12_no_aud.jpg

I had a null at 79.1 Hz. I figured since the wavelength there is 14.3 ft and the front-back measurement of my room is 14.6ft that I needed to move the sub away from the back wall. Here is the graph after moving the sub 2 ft away from the wall:
pc12_moved_no_aud.jpg

As you can see that solved my null problem. However, I still have large gains at 45 Hz and 73.6Hz. What can I do to bring those down? I've pretty much exhausted my placement options. Would room treatments help? If so, what kind? The following graph is what audyssey does for me:
pc12_moved_with_aud.jpg

Any ideas?
 

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Do you have any sort of EQ?
 

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Do you have any sort of EQ?
Just Audyssey MultiEQ (not XT) on my Onkyo TX-SR707. The sub has parametric EQ for removing one gain. I tried it to remove the gain at 45 Hz, and it worked, but I found Audyssey works better if I don't use the sub's parametric EQ.
 

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Treatments will help to a point, but it looks like your needs are broadband, and broadband absorption at those frequencies would be quite large to be effective. I suppose you could try tuned treatments with very low Q, but I don't know too much about them so you might want to ask in the Home Acoustics area....

But...

Why not run Audessey, and take an FR plot with it's filters engaged to see where it gets you?

Also, you say you've exhausted placement options for that sub, how about the listening position? Any options for moving it higher up?
 

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Treatments will help to a point, but it looks like your needs are broadband, and broadband absorption at those frequencies would be quite large to be effective. I suppose you could try tuned treatments with very low Q, but I don't know too much about them so you might want to ask in the Home Acoustics area....
I'm going to build a riser today based on the BBC modular sound absorber for very low frequencies. I don't know if it will help but I think it will be an interesting experiment.

Why not run Audessey, and take an FR plot with it's filters engaged to see where it gets you?
The last graph above is with audyssey. Or are you saying measure just the audyssey filters to see what it's doing?

Also, you say you've exhausted placement options for that sub, how about the listening position? Any options for moving it higher up?
Unfortunately, higher up for the couch is not an option, and the room is small enough that I don't have many options for furniture/tv placement. But I suppose the riser for the sub will make some height adjustment. I'll post the graphs with the results.
 

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I had a null at 79.1 Hz. I figured since the wavelength there is 14.3 ft and the front-back measurement of my room is 14.6ft that I needed to move the sub away from the back wall. Here is the graph after moving the sub 2 ft away from the wall.
Since you're showing us subs + mains graphs, the null might have been a phase issue.

Regards,
Wayne
 

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My thoughts: If your dimension at 14.6ft causes a mode at ~80Hz, that mode wouldn't show up as a null on the FR plot unless you're mic was close to the midpoint of that 14.6ft dimension. Outside of the center, it could show flat or close to it, and further towards the boundaries it would show as a peak.
 

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Greg, I expect you were thinking of a 1/2 wave length standing wave when you wrote. A full length standing wave, driven at one endpoint, should have nulls at the 1/4 wave and 3/4 wave points, i.e., ~3'6" from each wall in this case.

When I played with some simulation software for my room, it gave much more complex results, even with a simple model. So I am becoming much more reticent about make predictions, except for simple reflections. That's why playing with REW is so much fun: reality is much more complex and actual measurements don't lie. It does make sense to me, though, that moving the sub 2' from the wall, as Frank, did would make it less likely to set up standing waves at 80Hz.

Bill
 

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Yep, you got me Bill! At the same time, what you say about 1/4 and 3/4 wave points is true no matter where it's driven, not just from an endpoint. Certain places may reduce the modal effects, but the places where they occur will stay in place.

I agree with you about the real world vs predictions. Any time you get the sub out from a boundary, response is bound to be flatter. In fact, I have a little theory going here that 2.75ft would be even better.:D
 
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