Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 448 - AVS | Home Theater Discussions And Reviews
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post #13411 of 13426 Old Today, 07:49 AM
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For reflections
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post #13412 of 13426 Old Today, 07:53 AM
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So your real question is how much reflections should be attenuated?

Markus

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post #13413 of 13426 Old Today, 08:15 AM
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Yes. When measuring for reflections. What is the goal? Where should the impulse be below?
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post #13414 of 13426 Old Today, 08:31 AM
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There is no simple answer to this.

The audibility of reflections depends on the number of reflections, their direction, spectral content and delay. Furthermore it depends on the signal itself. Reflections of percussive sounds are easier to hear than reflections of instruments playing sustained sounds, e.g. violins.
Some reflections are "grouped" by our hearing. Although their individual level is low and doesn't show up as significant spikes in graphs, their perceived level is high.

Then there's the question whether room reflections are an integral part of stereo and multichannel. If yes then not all reflections can be considered bad. Good read: http://www.aes.org/e-lib/download.cf...86&name=harman

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post #13415 of 13426 Old Today, 08:44 AM
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Quote:
Originally Posted by markus767 View Post
Waterfall doesn't look like there's 60Hz hum. Do you hear anything?

Also try looking at the spectrum of the noise floor:
So once again I am learning how to interpret everything, but to me, it looks like I do have something going on at 60 hz - I can most certainly hear furnace noise - I will shut down system if my wife does not kill me and measure again....but I have no idea if furnace noise is that low.


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post #13416 of 13426 Old Today, 08:52 AM
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Originally Posted by markus767 View Post
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There is no simple answer to this.

The audibility of reflections depends on the number of reflections, their direction, spectral content and delay. Furthermore it depends on the signal itself. Reflections of percussive sounds are easier to hear than reflections of instruments playing sustained sounds, e.g. violins.
Some reflections are "grouped" by our hearing. Although their individual level is low and doesn't show up as significant spikes in graphs, their perceived level is high.

Then there's the question whether room reflections are an integral part of stereo and multichannel. If yes then not all reflections can be considered bad. Good read: http://www.aes.org/e-lib/download.cf...86&name=harman
Nvm. I am thinking of ETC
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post #13417 of 13426 Old Today, 09:25 AM
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Sorry Brian but your messages are too cryptic.

Markus

"In science, contrary evidence causes one to question a theory. In religion, contrary evidence causes one to question the evidence." - Floyd Toole
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post #13418 of 13426 Old Today, 09:46 AM
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Quote:
Originally Posted by Brian Fineberg View Post
What is ideal to have the impulse below -20? -15?

Sorry I'm not wording it correctly
Brian, the target referenced in the guide is to reduce reflections within the first 20ms below -20dB. There is nothing magic about this guideline, it is just something to shoot for.
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post #13419 of 13426 Old Today, 10:16 AM
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Quote:
Originally Posted by toofast68 View Post
So once again I am learning how to interpret everything, but to me, it looks like I do have something going on at 60 hz - I can most certainly hear furnace noise - I will shut down system if my wife does not kill me and measure again....but I have no idea if furnace noise is that low.
Don't know if it'll give you some further thoughts... When my furnace is on, the noise through the floor vents is very low-frequency, and really screws up the lowest end of the waterfall. I can barely hear it really, I just hear the furnace motor and the air flow a bit...getting old, the lowest freqs the subs can reproduce mostly evade me. So yes, I do turn the furnace off when making measurements, it's just too "random" on/off. The noise through the cold air return vent is much louder (to me), I do have one of those in the HT room and put a panel in front of it that helps an awful lot while still allowing airflow. Edit: my furnace and gas hot water tank are *right below* my MLP. Due to new safety/venting building code requirements, the new gas hot water heater I got just before starting with REW is much MUCH louder than my previous one...I can hear it more than the furnace even, the supposedly high efficiency burner makes a very audible LF sound...JIC you have one of those too.

Another thing that shows up for me is the fridge. This shows up as a small bump at 59.something Hz, just like on your graph. I am close enough that I can hear the largest fridge's compressor run, when everything else is quiet. I think part of the picked-up noise is from the very heavy fridge being on a suspended floor, as is my HT room. I thought some of the vibration may be going through the floor, so I tried isolating the mic stand (as I think was suggested in the Audyssey measurement guide, not Jerry's, I use the same stand for both): no diff really. I sometimes turn that fridge off when making more "serious"/baseline measurements like noise floor. I have forgotten to turn the fridge back on too many times as well...did I mention getting old?

Edit: what I meant by my ramblings is we get used to "normal" house sounds, they all make some, so you have to get very critical when trying to determine what some anomalous reading might be.

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post #13420 of 13426 Old Today, 10:59 AM
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Quote:
Originally Posted by AustinJerry View Post
Brian, the target referenced in the guide is to reduce reflections within the first 20ms below -20dB. There is nothing magic about this guideline, it is just something to shoot for.
Exactly what I wad looking for. Than you. Sorry I couldn't put into writing what I was thinking You figured it out
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post #13421 of 13426 Unread Today, 11:09 AM
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Originally Posted by toofast68 View Post
As for treatment, I have been spending a ton of time trying to figure out a plan vs. just randomly tossing stuff in the room. Is this the thread to work on the treatments, or am I better off starting a "new thread".
There is an Acoustics Treatment Thread.
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post #13422 of 13426 Unread Today, 11:17 AM
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Originally Posted by Selden Ball View Post
That's often caused by power lines running parallel to preamp or speaker cables. It can be particularly frustrating if the power lines involved are those feeding the house.
I don't think that particular hum is electronics related at all. I don't see or feel the speaker cones moving.

As mentioned later it might be the ductwork is tuned just so to drive me batty.

OTOH, I do get a hum like you mention from the single outlet in my "wiring closet/equipment closet" if I'm not super careful.
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Originally Posted by toofast68 View Post
Hummmmm.....ok...so what you are saying is that if I am just sitting there with everything OFF, I will still get that 60hz spike. Is there a way to measure the room to verify that.
Not at all. Least I don't think so. That was in response to a comment about a hum in my room.

I have this fantasy about getting my noise floor to 25dB when everything in the house is off (fridge, etc). Never going to happen but spurious noises remind me of just how fantastical my fantasy is
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post #13424 of 13426 Unread Today, 11:34 AM
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Originally Posted by cfraser View Post
I sometimes turn that fridge off when making more "serious"/baseline measurements like noise floor. I have forgotten to turn the fridge back on too many times as well...did I mention getting old?
I had to throw out a month's freezer load because of such a measurement mishap. One of these days I'ld like to contribute a pilot check list to AustinJerry's guide.


  1. Kick everyone out of the house, including dogs
  2. Turn off furnace
  3. turn off fridge
  4. snack to prevent stomach grumbling
  5. ...
  6. turn fridge on
  7. turn furnace on
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post #13425 of 13426 Unread Today, 11:48 AM
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In preparation for replacing my first generation Pioneers with Fusion 8 Alchemies, I ran REW on my center speaker only. Thanks (?) to the recent discussion about distortion, I looked at that tab and discovered this:





A great many sweeps later, the culprit turned out to be "Sound Retriever." Turning it off gave me this:



Take home lesson for Pioneer AVR owners: TURN OFF S-RTRV!

Michael

Downloadable FREE demo discs:
http://www.avsforum.com/t/1475769/de...ently-authored 

Did you really need to quote that entire post in your reply?
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post #13426 of 13426 Unread Today, 11:59 AM
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For those using REW and Java instead of ASIO (for one reason or another ) and HDMI, I have found an easy way to get signals to one speaker at a time.
I've mentioned Equalizer-APO before because of its eq capabilities, but a feature has been added that provides this function: COPY.

For example, to get output only to the subs, edit the config.txt file:

Copy: SUB=L L=0.0 R=0.0

For center channel only (I just turn the subs off manually, but you can probably add SUB=0.0; guess I'll have to try that next time. ):

Copy: C=L L=0.0 0.0

You can even check your right surround!:

Copy: RR=L L=0.0 R=0.0

Very handy!

http://sourceforge.net/p/equalizerap...Documentation/

Oh, and it also works really well with REW for eq.


Michael

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http://www.avsforum.com/t/1475769/de...ently-authored 

Did you really need to quote that entire post in your reply?
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