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I took some REW measurements today of just my sub, then both mains together, the the sub + mains together and would appreciate opinions on what I found.

I ran a 10hz - 120hz sweep on the sub, a 10hz - 20khz sweep on the mains, and a 10hz - 20khz sweep on the sub+mains, and it looks like I have some significant freq cancellation between 70hz - 90hz when the sub and mains are run together.



The NHT vt-1.2a mains each have a side firing 8" woofer. So to resolve this, my immediate thought is to adjust the crossover in the UMC-200 and set the mains somewhere between 100-120 with a 24db slope, and set the sub somewhere between 80-100 with a 24db slope. Since I'm performing the EQ'ing and crossover with the UMC-200, and measuring by connecting directly to the amps, I'm not sure if there's a way for me to measure how effective the solution would be. Maybe I can use the multichannel input, although I'll have to read up to see if that input will bypass the internal processing.

Another thought I had was to invert the phase of the subwoofer to see if it would help; although I realize it could introduce more issues in another part of the band. Unfortunately I didn't have time to test that, and probably won't until sometime tomorrow.

Here is the mdat file for the measurements.

Any thoughts on this? I'm new to analyzing the REW data, so appreciate any input you can offer.
 

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...it looks like I have some significant freq cancellation between 70hz - 90hz when the sub and mains are run together.
Sure, this is often the case when you combine mains with good extension and subs. That’s why we separate their operating frequency ranges.


The NHT vt-1.2a mains each have a side firing 8" woofer. So to resolve this, my immediate thought is to adjust the crossover in the UMC-200 and set the mains somewhere between 100-120 with a 24db slope, and set the sub somewhere between 80-100 with a 24db slope. Since I'm performing the EQ'ing and crossover with the UMC-200, and measuring by connecting directly to the amps, I'm not sure if there's a way for me to measure how effective the solution would be. Maybe I can use the multichannel input, although I'll have to read up to see if that input will bypass the internal processing.

Any thoughts on this?
At the risk of sounding “snippy” - perhaps you’re over-analyzing things? Setting up crossovers between subs and mains is usually considerably easier than making a movie. :D Typically you can just set it somewhere between 80-100 Hz and you’re good to go. Only in unusual circumstances are staggered crossover points needed.

Regards,
Wayne
 

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Discussion Starter · #4 ·
The UMC-200 has separate crossovers for the mains and the sub, and I could certainly set them both to 80, 90, 100 etc ... But with a roll off of 24dB, I was concerned the overlap would still be significant enough to cause enough cancellations to create a dip.

I really need to be sending the test tones to the speakers through the processor to satisfy my curiosity. I'm going to head over to the EMO forum to see if the analog 7.1 channel input bypasses the PEQ and bass management functions. If it doesn't, this would be the perfect solution to checking the results.
 

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Looks like a trough between 40-100hz. I would keep your measuring method consistent, and spend some time experimenting with placement, and phase. Try crossing at different points from 50 to 100 too. I think a room induced trough would be narrower. (Maybe), but the only way to fix that is moving the sub/mains, or the LP.
 

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But with a roll off of 24dB, I was concerned the overlap would still be significant enough to cause enough cancellations to create a dip.
Most processors’ crossovers these days use Linkwitz-Riley alignment, which is electronically flat through the crossover region. Acousically is another thing, though, but typically any issues are solved with phase adjustments or EQ, not by staggering the filters.

Regards,
Wayne
 
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