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Multiple Sub EQing with MiniDSP. I'm lost with this result...

1K views 3 replies 4 participants last post by  willis7469 
#1 ·
Ok, so I decided to do some EQ'ing of my system. All subs are crossed to the mains at 100Hz in my AVR.

Equipment: (All subs are receiving the full low end signal. No crossovers between them.)
1x JBL 4645C clone
2x Martycubes with Dayton HO 18's
1x 25Hz ported box with 2 Infinity 1260W's
1x EP4000
1x iNuke 1000DSP
1x MiniDSP 2x4

So I am using the MiniDSP for my EQ work and REW for plotting the response etc.

This plot shows the first response (red) & the best I could get so far (green).



However what confuses me is that after a lot of mucking around trying to boost 50Hz, I tried cutting it. So I cut 50Hz to -12 with a Q of 1.5, and deleted the +3 boost I was giving it at 20Hz and the plot came out like this. I'm confused. Why would cutting 50Hz by -12 bring the frequency response back up to where it should be????

When playing music with this config afterwards, it sounded like the subs weren't even on due to the big cut at 50Hz!

I also got rid of the boost I was giving it at 20Hz and it seemed to help the rest of the response.

What's going on!!?? :help:
 
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#2 ·
A deep dip in FR like you have at 50 Hz is due to a standing wave resonance or a reflection/cancellation. It is an acoustical problem. It can not be EQed away by boosting.

But a phase shift at that frequency, as you caused with your 50 Hz cut filter, can change its character and decrease its negative effect on your response. Your filter choice was a lucky one. A slightly different set of filter values might have yielded a very different result.

As for why it did not sound better, that kind of problem is very position sensitive. Your ears are probably getting two different responses more like the original.

Solve it acoustically via sub position or some other room changes.
 
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