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post #2491 of 2496 Old Today, 08:00 AM - Thread Starter
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Quote:
Originally Posted by Mr.Tim View Post
Format of the graph looks fine. What are the different plot lines? Different subs?

............
Each sweep is from one of the three front row listening positions.

I think you are correct about the modes, though. I believe the dip in the blue trace at 49 Hz is due to the 2-1-0 mode and the dip at 58 Hz is the 3-0-0 mode.

flipping the sub will address the tangential modes, correct?

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Originally Posted by Mfusick View Post
@lilmike look! Paul ran a sweep! Progress!
I know, right! I need to get a game plan together for how I want to go about measuring the room. I may start a thread over in the theory forum.

Dude, are you made of leprechauns? Cause that was awesome!

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post #2492 of 2496 Old Today, 08:32 AM
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baby steps. Focus on just getting some good measurements. If you have not even treated your room yet, but have a plan and material to do so, install that and see what happens. Once it's all done, then you can look to really tweak stuff.

-

"Too much is almost enough. Anything in life worth doing is worth overdoing. Moderation is for cowards."
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post #2493 of 2496 Old Today, 08:50 AM - Thread Starter
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Yeah. Good point.

BTW, I'm digging this room mode calculator. I always have trouble visualizing the room modes compared to mode numbers because I don't look at it often enough.

Dude, are you made of leprechauns? Cause that was awesome!

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post #2494 of 2496 Old Today, 10:01 AM
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Quote:
Originally Posted by J_P_A View Post
Yeah. Good point.

BTW, I'm digging this room mode calculator. I always have trouble visualizing the room modes compared to mode numbers because I don't look at it often enough.
Does the plan indicate the subwoofer positions? Maybe a call to the designer and see what he says given your measurements.

I'm am barely above completely ignorant on the subject (stop using big words like tangental...) but in my cranium I would try to correct any issues first by speaker placement. After that I'm guessing you would treat the room to correct the response and finally tweak with DSP? I am asking more than making a statement.

I just don't know how the designer would know there is a 20dB dip unless the subwoofer locations were specified. Maybe it doesn't matter with LFE... just treat the hell out of the corners?

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post #2495 of 2496 Unread Today, 10:25 AM
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This is a post from Mark that I'm sure most have read. A lot of good info here that's good to keep in mind.

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Originally Posted by Mark Seaton View Post
While responding to some questions in this thread over Sunday morning coffee I found myself with a decent summary on subwoofer optimization using Room EQ Wizard (REW) or other measurement systems like the Dayton OmniMic or XTZ Room Analyzer. This is by no means comprehensive, as we could flesh out many bullet points on a few of these items, but I thought it was a worthwhile summary to post up before I go ahead and organize the measurements and data on thebland's system that I'll be posting on my forum. This is a generalized post that won't apply to all systems depending on number of subwoofers, inclusion of manual subwoofer EQ, and features and functions of each surround processor.


To summarize some of my thoughts and experience, here's my suggestion for most attacking their system with REW and other measurement systems:

  1. Take a subwoofer only measurement in your first subwoofer location while noting signal levels to the subwoofer and volume setting.
  2. Do NOT change any signal levels and start moving the subwoofer to any other possible locations saving a measurement at each location. The response should be louder or softer from different locations and you want to see this.
  3. Choose the location with the balance of fewest dips and most efficiency across the subwoofer range.
  4. If you have more than 1 subwoofer, pick locations that compliment eachother where dips do not overlap.
  5. With multiple subwoofers overlay individual responses and then measure both together driven at the same level to see how they sum. Maximum summation of 2 equal sources is +6dB. Unless there is a big peak, the goal is to get the sum to be +0-6dB and not negative. Moving the sub or adding delay to the closer sub is my preferred way to make this adjustment.
  6. If manually EQ'ing, now apply EQ to the subwoofer alone while also watching for peaks out to 120-200Hz that go above the target or above flat flat if no HP is in the measurement.
  7. Now run any auto-EQ/room correction.
  8. Measure the subwoofer alone and center channel alone, then the combination of the two.
  9. Make adjustments to the subwoofer distance setting, most often adding to the physically measured distance at 0-8ms.
  10. Choose the smoothest interaction and adjust the crossovers up or down if you see room for improvement.
  11. If you have separate EQ on the subwoofer you can sometimes improve a lumpy/peaky summation by adding a notch to the subwoofer around the crossover range. The benefit to dialog and music balance far outweighs a small dip to the LFE channel.
  12. Next compare the interaction with the left & right speakers making crossover setting and delay adjustments to get a best fit for both.
  13. The more you listen to movies & surround concerts, the more you should prioritize the center channel vs. left/right.
  14. Now measure what happens when you increase the subwoofer level by 3,6 and 9dB to understand what happens when raising the sub level.
  15. Do some listening and adjust the subwoofer level and/or shape to what you are after, and then re-measure subwoofer-center interaction to insure any ramping up in response you add is as smooth as practical.
  16. Enjoy!

There have been many times when people have asked "What does Mark do that an auto-EQ system or typical enthusiast can't?" when they hear people raving about the results after I get into setting up or adjusting a system for 3-12 hours. My answer is that anyone COULD do it, very few do. Few will take the time to gather all the measurements and learn how to manipulate what they see. I encourage more to be some of the few, or search them out to set up their system.

-




Is it solipsistic in here, or is it just me?
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post #2496 of 2496 Unread Today, 10:45 AM
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What are the temporal aspects of the measurement - sweep duration, gating, smoothing?

IIRC, you were not able to get raw outdoor measurements for these subs - so we should post Mike's data at the same settings so that we can begin to compare and tease out the influence of the room and placement.

Tim - I'd say your sequence works fine and is what I would have said a year or two ago, but at this point I would say that treatment is so tough below 80Hz - and given the minimum phase relationship of a sub and the response - eq is not a bad thing; if you have a good idea about your headroom, go ahead with eq, once location is pinned down, IMO.
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