speaker + sub vs. testing separately - Home Theater Forum and Systems - HomeTheaterShack.com

 
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post #1 of 3 Old 06-06-10, 07:48 PM Thread Starter
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Join Date: May 2010
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speaker + sub vs. testing separately

For initial testing of my 2-channel system, I left my sub connected, so when I was testing the right I was actually testing right + sub (and similarly for the left). I did this so I could see the results for my "right system" and my "left system" as opposed to breaking it down to front/left/sub tests. Of course, I could disconnect my sub to be able to measure the front right on its own and front left on its own, then also test the sub on its own.

But, I am wondering - for a 2-channel system what's the advantage of doing that (or conversely, the disadvantage of doing the testing as I did)?

FYI, during the testing phase, I sent a test signal as though I was testing "full range". The end results made sense to me, but I am just wondering about the pro's/con's as noted above.

Thanks!

Mark
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post #2 of 3 Old 06-06-10, 11:19 PM
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Bill
 
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Re: speaker + sub vs. testing separately

You are right that looking at the left+sub and right+sub curves, you see the overall frequency response given your choice of crossover, and you get a visual confirmation that the levels are even. With the curves you have taken, you can compare the RT60 measures for the front speakers, to see if one is energizing more resonances than the other, and you can similarly compare the waterfall charts for your two front speakers.

There are a few things you can do better or only by looking at the curves separately.

Equalization, whether it is done manually or you are just investigating the receiver's automated system, is done on a per channel basis. So you need to look at each speaker separately to adjust the equalization or to investigate exactly what the receiver is doing.

Waterfall charts of the combined speakers can give you some information about the common room responses. But when you begin to move the speakers, it is helpful to have an individual measure of each speaker to see which energizes a particular room mode and whether changing its position improves the room response.

Similarly, if you want to look at the impulse curve or ETC to see where room reflections occur, to convince yourself that you need to treat certain parts of your room, this needs to be done looking at individual speaker measures. Clearly each speaker is in a different position, and the sub has different reflections than do each front speaker.

With REW v5 and using the left channel for timing, with separate measures for the sub and the fronts you can see the phase each has at and near the crossover frequency. This is more certain than just seeing a dip in the combined response and guessing the speakers are out of phase.

Using REW v5 to verify and adjust the distance to the sub, I found separate measures of the impulse curves more useful than looking at the group delay curve of just the combined response.

I'm not advising you to undertake any of these investigations. Sane people listen to an album instead. And all of these are more in addition to, not instead of, the primary measures you took of each front individually combined with the sub.

Bill
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post #3 of 3 Old 06-07-10, 06:37 AM Thread Starter
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Re: speaker + sub vs. testing separately

Very helpful - thanks!

I'm just learning these things, so you gave me a lot to go study to learn more.
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