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Old 09-09-2013, 03:28 PM
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Originally Posted by craig john View Post

My point is that the important response is the *combined* response of all modes together.
With that in mind, do you think that mantaraydesign not even try to cancel the width modes as jkasanic did the in the example above?
Originally Posted by craig john View Post

The "width mode" isn't cancelled across the entire width of the room. A "standing wave" is a series of peaks and nulls across the dimension. As you move from left to right, you move from areas of peaks to areas of nulls. Try playing a 40 Hz tone and walking across the width dimension. You can literally stick your head into and out of the peaks and nulls. Take an SPL meter with you on your journey across the width of the room and you'll be able to measure these peaks and nulls. So, whether the listening position is in a peak or a null, or neither will have as much impact on the measured response as the subwoofer positioning.
Do you believe that modes (peaks & dips across a room dimension) can be cancelled? When people say they're arranging their subwoofers for "mode cancelling" do you think that's actually what's happening or that they're using that term as a figure of speech to mean smoother response or greater seat-to-seat consistency?
Originally Posted by craig john View Post

In your example a null was removed at the listening/measuring position with the subwoofer re-positioning. That is a good thing. But the nulls were likely caused by the corner positioning, and may well have been improved just by getting the sub out of the corner. But at other, (arbitrary), listening/measuring position(s), those nulls still exist, as do the concomitant peaks.
I've done the exact experiment you suggest (with SPL meter in hand, no less) and found the peaks & dips to be grossly mininmized across the width of my room (minimized to the point where I had trouble detecting them without the SPL meter). I did this at a time when I was just barely starting to understand modal behavior and had read about a subwoofer trick described in a Toole paper (click on snippet below). Because it worked in a real-world situation, it got me digging into why it worked.

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