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Discussion Starter · #1 ·
Hi! I've been working on our home theater room/living room and ran across REW during my research of room acoustics. I purchased a CM-140 SPL meter and have generated what I believe to be a valid set of measurements. No BFD or other EQ in my possession at this time.

My primary goal is to clear up muddy dialouge experienced while watching movies. My hope is that REW will help me identify the problems with my room and my AV setup.

A bit of background info: It's a 12 x 19 room with a ceiling that slopes from 9' at the front wall (AV Equip) down to 7' in the back (listening position).

I'm close to buying acoustic panels, as others I've spoke with believe that the sloping ceiling and other hard surfaces are causing too many reflections in the room and is my major problem. I believe I'm seeing this in the waterfall graphs, and i have a basic comprehension of what all the graphs are telling me, but I would appreciate any feedback anyone may be willing to offer, before heading off to the room acoustics forum.

Thank you for your input!

Graph 1 - Sub measurement
Graph 2 - Sub waterfall
Graph 3 - Mains measurement
Graph 4 - Mains waterfall
Graph 5 - Sub & mains measurement
Graph 6 - Sub & mains waterfall
Graph 7 - Sub & mains extended range measurement
Graph 8 - Sub & mains extended range waterfall
 

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Good job on the graphs.

There isn't anything that jumps out at me as being a problem with the sub and mains.

All your responses and waterfall look quite well behaved.

Certainly any problems you're having with muffled dialogue would be attributed to the center channel. You may want to check the center channel with REW by simply switching the speaker cable between center and a main speaker and do a sweep of that channel by itself and then also a measure with the sub and center (that is hooked to a mains speaker terminal). It may reveal some cancellation or peak around the crossover (assuming the center uses the same cross as the main channel it is using for the test). It may also reveal some large dip around 300Hz (dialog)..

brucek
 

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Muddy dialogue is pretty easy to diagnose. Typically it’s because of too much bass in the center speaker, low levels in the sibilant range (~ 6-8 kHz), or both. The waterfalls don’t look bad, but they aren’t going to tell you anything about the muddy dialog problem. They are only meaningful in the low frequency range, well below the frequency range of voices.

I’d suggest taking a full range reading of the center channel only. This can be done by unplugging both the main left and right speakers and plugging the center channel speaker cable in where the left or right main speakers were. Smooth the graph at 1/3-octave so we can see the trend in response without all the comb filtering.

Regards,
Wayne

 

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Discussion Starter · #4 ·
Hey guys - Thanks for the quick response! (and on a weekend no less :)

Here's the graph of the center connected via the right channel (left channel disconnected)

AVR is set for 80Hz crossover on mains, center & sub

Center is JBL LC-2 (crossovers at 700Hz, 4000Hz, 20kHz)
 

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Well, you can see that the center has quite a peak at 70Hz-120Hz. This extra bass may cause some problem with dialog.

I suppose one of the problems with a center is that they can't usually be moved. Often Audyssey will remove that sort of peak. Do you have any internal eq capability in your receiver?

brucek
 

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Discussion Starter · #6 ·
Bruce - unfortunately no, it's an older Denon 3802. Good point though - didn't even think about that :duh:. I just set the center crossover on the AVR at 120 hz and it brought that peak down a bit. We'll be watching a movie tonight, so we'll see how it sounds.

David
 

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just set the center crossover on the AVR at 120 hz and it brought that peak down a bit.
Yeah, that's a good test. Your sub doesn't exhibit any peaks around the 70Hz-120Hz range so raising the crossover should lower the peak for sure, although you may find some sub localization when you use such a high cross. If your sub is near the center (physically), then you may get away with it.

Either way, it's a good method to establish if that's the problem.

brucek
 

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In lieu of a calibrated mic, it can be difficult to determine if what the graph shows for the upper frequencies accurate, but I notice that the high end is sagging pretty severely on both the center and mains graphs. This can make things sound muffled. Of course, the orientation of the mic makes a huge difference in what the graph shows - hopefully you pointed the mic at the speaker?

How do the sibilants in voices sound? If they sound weak or indistinct, you might try pushing your treble control up a few notches and see of that makes a difference. If the sibilants sound balanced in relation to the rest of the voices, then disregard this...

Regards,
Wayne

 

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Discussion Starter · #10 ·
Wayne/Bruce - We watched "Defiance" yesterday and had problems with the dialouge. Tonight I re-played a couple of scenes that we had difficulty understanding and they sounded much better - no problems understanding.

We watched "A haunting in Connecticut" (in DTS) tonight and both I and the Mrs. had no problems with the dialouge. So the switching of the crossover made a noticeable difference to us. (and thank goodness - if I had to hear "what did he/she say" one more time :) ...

The SPL was placed at ear level in the center of our loveseat (pointing directly at the center & between the mains) for all tests.

I had to look up the word sibilants by the way :-( Haven't had to do that in a long time! Don't recall, but I'll pay more attention to that in the next couple of movies.

Is EQ my best option to raise the high-end if we need further help in this area (and treble increase doesn't help) ?
 

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Is EQ my best option to raise the high-end if we need further help in this area (and treble increase doesn't help) ?
The answer is "yes, but."

Yes, EQ is the best option. But that can only be done if you add an outboard amplifier, as an equalizer must be inserted in the signal chain between the pre-amp and the amplifier. By the time you spring for the amp and equalizer, it might make more sense just to get a newer receiver with more flexible equalization capabilities.

Regards,
Wayne
 

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Discussion Starter · #12 ·
I agree. My Denon has served me well, but I've been contemplating a replacement for a couple of months now.

I'm glad I took the time to work with REW and learn a little bit about my room and the acoustics.

Thanks to you both for your guidance!
 

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Discussion Starter · #13 ·
Just an update: I purchased an Onkyo TX-NR3007 to replace the Denon AVR-3802 and dialouge has improved! The overall range seems better, though maybe lacking a bit in bass for my taste. I'm sure I have some tweaking to do, but I haven't had time to run RoomEQWizard. After the holidays I should have things nailed down.
 

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My $0.02...

dz, you have done a great job. This concise thread is an excellent case study of how/why to use REW.

The response graphs and waterfalls look very good too, particulary considering you do not have any acoustic treatments or EQ in the signal chain. :T


Tim
:drive:
 

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Discussion Starter · #15 ·
Tim - thanks for the thumbs-up, but I'd still be lost if it weren't for the help of Wayne & Bruce. I still have a lot to learn and tweaking to do, but it was definitely worth the investment in research, time and money. It's great that resources like HTS and tools like REW exist to help us all along.

I am still considering sound treatment (not as much as originally proposed), but am holding off until I spend some more time with REW.

Of course now that I have upgraded the majority of my audio/video system over the past 2 years, my main speakers are begging to be relegated to surround duty and be replaced by something a little better... and so the cycle goes:spend:
 
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