Trying to Fix Center+Sub FR - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 32 Old 03-06-17, 02:14 PM Thread Starter
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Trying to Fix Center+Sub FR

My center channel sits on the top shelf of an A/V rack beneath my display about 2.5 feet from the front wall.

Running full system sweeps per pg.100 of the REW Step by Step Guide, I generated the graphs below for the center only, and for center+sub. There's a large dip centered around 100Hz that I think is due to SBIR; [ fc = c/4dwall = 112.5Hz ], so that would need to be addressed first.

Any help to understand or solve these issues are greatly appreciated!
  1. What are the reasons for the dips close to 200Hz and 400Hz?
  2. Why does the FR have a rising trend? Room gain?
  3. Does sub phase need to be adjusted to provide good SPL support through the xover region for both the mains AND the center simultaneously? IOW, if it's good for the mains, is it good for the center?
  4. Would an external time delay (my AVR disables them when using Dirac) make my sub play nicely with both mains and center?

Trying to Fix Center+Sub FR-layout-1-fr-c-only-12db-.jpg Name:  Layout 1 FR -  CenterSub.jpg
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Trying to Fix Center+Sub FR-layout-1-fr-lr-only.jpg Trying to Fix Center+Sub FR-layout-1-fr-lrsub.jpg

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post #2 of 32 Old 03-06-17, 02:43 PM
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Re: Trying to Fix Center+Sub FR

Sub level looks a little low. Where are you crossing mains to the sub? If it's 90-100 then the dip there could absolutely be the culprit.

200 and 400 could be SBIR from front wall, side walls, ceiling, etc.

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post #3 of 32 Old 03-07-17, 08:12 AM Thread Starter
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Re: Trying to Fix Center+Sub FR

Quote:
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Sub level looks a little low.
Thanks for your quick response, Bryan! The sub level for the Center+Subs measurement is low because I needed to reduce REW's input level to avoid clipping.
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Where are you crossing mains to the sub?
Good question! The measurements were taken with auto-EQ disabled, so I thought bass management was as well. Now I'm unsure how my processor handles crossovers. I do know that its Dirac Live LE feature uses non-adjustable 80Hz crossovers - yes, that's a peculiarity of Dirac Live for Emotiva (LE). So I looked it up on pg.53 of the manual, and found that when certain playback modes are active, so is bass management. This simple functionality didn't occur to me before, so I have no idea at what point the crossovers were set! I will need to look them up in the processor's menu system when I get home.

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post #4 of 32 Old 03-07-17, 12:22 PM
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Re: Trying to Fix Center+Sub FR

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Thanks for your quick response, Bryan! The sub level for the Center+Subs measurement is low because I needed to reduce REW's input level to avoid clipping.

Good question! The measurements were taken with auto-EQ disabled, so I thought bass management was as well. Now I'm unsure how my processor handles crossovers. I do know that its Dirac Live LE feature uses non-adjustable 80Hz crossovers - yes, that's a peculiarity of Dirac Live for Emotiva (LE). So I looked it up on pg.53 of the manual, and found that when certain playback modes are active, so is bass management. This simple functionality didn't occur to me before, so I have no idea at what point the crossovers were set! I will need to look them up in the processor's menu system when I get home.
I think he meant the sub level itself is low.
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post #5 of 32 Old 03-07-17, 12:32 PM
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Re: Trying to Fix Center+Sub FR

Yes - exactly. The sub isn't balanced to the mains.

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post #6 of 32 Old 03-07-17, 02:17 PM Thread Starter
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Re: Trying to Fix Center+Sub FR

That's a mystery to me, and I believe you, but how can you tell without an mdat or a sub-only graph?

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post #7 of 32 Old 03-07-17, 02:35 PM
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Re: Trying to Fix Center+Sub FR

Just look at the general level compared to 80 and above.

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post #8 of 32 Old 03-07-17, 02:42 PM
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Re: Trying to Fix Center+Sub FR

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That's a mystery to me, and I believe you, but how can you tell without an mdat or a sub-only graph?


This was kinda my question in the other thread. You mentioned reducing the sub level for REW , and it looked like a rise up to 70ish. Curious, why not just lower the MV?
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post #9 of 32 Old 03-07-17, 02:54 PM
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Re: Trying to Fix Center+Sub FR

Either will work.

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post #10 of 32 Old 03-08-17, 07:53 AM Thread Starter
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Re: Trying to Fix Center+Sub FR

Quote:
willis7469 wrote: View Post
This was kinda my question in the other thread. You mentioned reducing the sub level for REW , and it looked like a rise up to 70ish. Curious, why not just lower the MV?
Quote:
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Either will work.
I'm getting old... my memory fails me. I thought I had reduced the soundcard's input level to avoid clipping, not the sub's output, but I can't find the post now. I'm making such a big deal about it because I'm thinking I should have taken all measurements over again, not just CENTER+SUB. Then the relative levels between graphs would synch up.

But you're not talking about relative levels between graphs, are you? I think I finally get it - you're saying the sub's level should be brought up to match the mains, correct? I was not aware of this system tuning step, so I always left it up to auto-EQ. Yet it makes sense to correct as much as possible before auto-EQ to reduce audible artifacts resulting from too many filters.

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