Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How... - Page 58

Quote:

Originally Posted by Alan P 

JD - it's my understanding that the mode calculator is pretty much useless for those of us with open floorplans.

Not necessarily.  Any of these models are approximations designed to help us address room response issues.  I have an open floor plan as well.

The first step in the process is to measure the listening area's frequency response, 15-20,000Hz.  Looking at the measurement, you should look at several of the worst peaks and/or dips, and note the frequency range in which they occur.  These peaks/dips are the result of interactions with rooom modes.  The question is, which room modes?

Next step is to pick a room lenght, width, and height to enter into the standing wave calculator (download a copy here).  For the room length, I would measure from the wall where the TV is to the bak wall where the stairs are.  For width, I would measure from the wall with the couch to the wall where the left surround is placed.  When you enter these values into the calculator, see if any of the calculated room modes match up with the peaks/dips in your frequency measurement.  If yes, then you can use this information to experiment with placements to see if you can get any improvement.

If none of the calculated standing waves align with the measurements, you can try entering the room width as the width of the entire open space, and see if any calculated standing waves match the measurements.

If you still can't get the calculations to match up with measurements, there are still general guidelines that you can follow for speaker and sitting locations.  Place speakers at 1/4 and 3/4 positions across the front wall, or at 1/6 and 5/6.  Place these speakers 1/8 of the length away from the front wall.  etc.

The point is, experiment with placement, and measure!

I certainly agree with you on symmetry, Sanjay.  I have gone to a great deal of trouble to make sure that I am sitting in the exact center of my room (side to side), and that my five primary speakers (LCR and surrounds) are all the same distance from the MLP.  Even my four subs are in two pairs at the same distance from the MLP.  In my experience, the improved soundstage that comes from symmetry more than offsets anything else.  The MLP is at the 1/5 spot, front to back.

Quote:

Originally Posted by sdurani 

Quote:

Originally Posted by AustinJerry 

In my experience, the improved soundstage that comes from symmetry more than offsets anything else.

Yup, but that's a personal choice that you and I make. It is interesting to find people that fall on the other side of that compromise: e.g., knew someone that had a pair of Lay-Z-boys at 1/3 and 2/3 of room width. That would drive me nuts.

You can have a symmetrical arrangement that is off-centre though - by that I mean you can sit exactly between the speakers even though the midpoint between the speakers is not on the centre line of the room. Doesn’t this make for better overall SQ potential? I seem to recall reading that if each speaker is the identical distance from each sidewall, for example, this can excite room modes and/or reflections in an undesirable way?  Do I recollect this properly?

Quote:

Originally Posted by kbarnes701 

You can have a symmetrical arrangement that is off-centre though - by that I mean you can sit exactly between the speakers even though the midpoint between the speakers is not on the centre line of the room. Doesn’t this make for better overall SQ potential? I seem to recall reading that if each speaker is the identical distance from each sidewall, for example, this can excite room modes and/or reflections in an undesirable way?  Do I recollect this properly?

When I first set up my listening room back a few years, I had a setup like you describe.  When I embarked on my journey of trying to improve my overall audio experience, I found centering everything in the room was more desirable.  There is a lot of discussion about whether reflections are good or bad, but there seems to be agreement on one thing--having balanced reflections (same from left and right) is more desirable than unbalanced reflections.  A room that is not centered produces uneven reflections, which is not good.

Quote:

Originally Posted by asarose247 

For uploading of data files for analysis, is there any prefernce for either send space or dropbox?.
i'm still testing and moving sub(s) around but want to make available what I managed to record so far!

And would that be the entire .mdat file as REW asks to save?

Either service is fine.  And yes, the entire MDAT file.  You should also post:

- Frequency response 15-20,000, smoothing 1/6, for left+right+subs.

- Frequency response, 15-300, no smoothing, for left+right+subs.

- Room layout, or at a minimim, your room dimensions

- Room pictures, if you have them

Quote:

Originally Posted by AustinJerry 

Quote:

Originally Posted by kbarnes701 

You can have a symmetrical arrangement that is off-centre though - by that I mean you can sit exactly between the speakers even though the midpoint between the speakers is not on the centre line of the room. Doesn’t this make for better overall SQ potential? I seem to recall reading that if each speaker is the identical distance from each sidewall, for example, this can excite room modes and/or reflections in an undesirable way?  Do I recollect this properly?

 

When I first set up my listening room back a few years, I had a setup like you describe.  When I embarked on my journey of trying to improve my overall audio experience, I found centering everything in the room was more desirable.  There is a lot of discussion about whether reflections are good or bad, but there seems to be agreement on one thing--having balanced reflections (same from left and right) is more desirable than unbalanced reflections.  A room that is not centered produces uneven reflections, which is not good.

Good feedback, Jerry, as ever. Because I only use my room for HT, all reflections IMO are considered 'bad' and need to be struck down with great vengeance and furious anger. Any ambience I expect to hear is already in the 5.1 soundtrack and capably reproduced by my fine array of carefully positioned speakers. 

I'm not disagreeing with you BTW - just stating my own preference here, although I do sit fairly symmetrically in my room (as far as it allows) and would almost certainly always sit absolutely symmetrically, room etc permitting.

Quote:

Originally Posted by sdurani 

Quote:

Originally Posted by kbarnes701 

You can have a symmetrical arrangement that is off-centre though - by that I mean you can sit exactly between the speakers even though the midpoint between the speakers is not on the centre line of the room. Doesn’t this make for better overall SQ potential? I seem to recall reading that if each speaker is the identical distance from each sidewall, for example, this can excite room modes and/or reflections in an undesirable way?  Do I recollect this properly?

You might be recalling home theatre architech Russ Herschelmann, who was very influential when it came to symmetrical set-ups that were off-centre in the room (for the very reasons you mention). I tried it back in the day and ended up not liking it. I tend to light up my side walls with high gain early reflections, so following Herschelmann's approach made for an asymmetrical soundstage. Might not bother some people but was annoying to me to have the soundstage stretch out wider on one side than the other.

Besides, if you look at the mode calculator graphs posted in this thread, seems that symmetrical placement of speakers and subs yields benefits. Moving the entire set-up so that it is asymmetrical to room boundries would lessen my ability to use placement as a method of minimizing modal problems, forcing me to rely more on treatments and EQ. So IF I want to use symmetrical placement to improve modal response, then I have to decide whether I want to sit centered in my set-up (more symmetrical) or off-centre (smoother response). I can't do both.

Easier for me to figure out multiple methods to fix frequency response problems that come from sitting in the middle of room width than it is to figure out how to fix an asymmetrical soundstage. The latter can be done, but would involve absorbing enough early reflections that I would no longer enjoy listening to music on that sort of set-up.

I am flattered, Sanjay, that you would think I had read about Russ Herschelmann, and indeed maybe I even have and forgotten, but the influence you mention may have been echoed in something or other I happened across long ago. Either way, thank you for adding a layer of credibility to my ramblings :)

I so wish I had more space here to experiment the way you have with placement.  One day maybe...

For my view on reflections, I just regaled Jerry with my thoughts...

Quote:

Originally Posted by kbarnes701 

 

Good feedback, Jerry, as ever. Because I only use my room for HT, all reflections IMO are considered 'bad' and need to be struck down with great vengeance and furious anger. Any ambience I expect to hear is already in the 5.1 soundtrack and capably reproduced by my fine array of carefully positioned speakers. 

 

I'm not disagreeing with you BTW - just stating my own preference here, although I do sit fairly symmetrically in my room (as far as it allows) and would almost certainly always sit absolutely symmetrically, room etc permitting.

I agree, my comments on reflections would likely only make a difference for serious music listening.  I know you have a separate setup for music.

Here is another interesting use of REW to analyze what Audyssey room calibration is doing:

The graphs represent three measurements of each of my three front speakers (Green=Preout, Red=Audyssey On, Blue=Audyssey off):

Left front:

Right front:

Center:

Here is how to interpret the results.  Take the center speaker as an example.  The in-room un-corrected response (i.e. Audyssey off) shows nice peaks at 60Hz and 150Hz.  The preout measurement (which shows the correction Audyssey is applying to the center channel signal) shows inverse peaks at the same two frequencies.  The post-Audyssey in-room response shows that the Audyssey correction has completely erased both peaks, resulting in a nice smooth response.

Pretty cool, no?  Are we liking REW now?

Quote:

Originally Posted by sdrucker 

Question about measuring the center channel in REW:
I'm using HDMI connection from the laptop to my Denon 4311 (V-AUX source, HDMI-7 port). If i pick channel 3 as input, which should be the center channel, how can I get center channel output without running PLII Cinema, when Audyssey is enabled. Stereo mode reproduces the sound in my right speaker. Am I missing something obvious to set to force no signal processing from the HDMI mono signal from REW?

In direct mode it works correctly, but that's with Audyssey off.

Since my laptop only supports two channels, I'm not sure I know the answer, Stuart.  Are you sure channel 3 is the center and not the LFE?  I know Keith will have the answer.

Quote:

Originally Posted by sdrucker 


In direct mode, channel 3 is center, and channel 4 is indeed LFE, which I confirmed with test tones. Everything else maps to the 'standard' layout, at least through channels 5 and 6 (surround left and right in my 5.1 system).

Keith has an Onkyo, not a Denon, and IIRC he's using something called 'Pure Audio'.

Maybe some of us with Denons want to stck with PLII Cinema for the center after all...

AFAIK, Pure Audio is the same as Direct Mode, or perhaps Pure Direct Mode.

Quote:

Originally Posted by sdrucker 

Question about measuring the center channel in REW:
I'm using HDMI connection from the laptop to my Denon 4311 (V-AUX source, HDMI-7 port). If i pick channel 3 as input, which should be the center channel, how can I get center channel output without running PLII Cinema, when Audyssey is enabled. Stereo mode reproduces the sound in my right speaker. Am I missing something obvious to set to force no signal processing from the HDMI mono signal from REW (i.e. source specific bitstreaming)?

In direct mode it works correctly, but that's with Audyssey off, of course.

BTW, if anyone still cares, I picked up the OmniMic 5.1 test DVD. From a quick look, it does the usual tests (sine sweep, bass sweep, pseudo-noise, delay) for each of the 5.1 channels, but only for individual channels, including LFE. That actually makes the ability to pick and choose two channel inputs in REW more useful.

I just use basic Multichannel 5.1. When I select '3' in REW it plays the centre channel. No DSP applied. Dunno how you do it in Denon but with Onks you can just cycle through the DSPs until you get to M/Ch 5.1. 

BTW, I don't use Pure Audio normally - I may have mentioned I used it for a specific purpose, or maybe when I had no idea at all what I was doing with REW  ;)

Basically you select it in the AVR just as you would select any source that you don't want to use a DSP on - straight 5.1 Dolby etc, except it comes up as M/ch (or it does om the Onk anyway).

Quote:

Originally Posted by AustinJerry 

Here is another interesting use of REW to analyze what Audyssey room calibration is doing:

 

The graphs represent three measurements of each of my three front speakers (Green=Preout, Red=Audyssey On, Blue=Audyssey off):

 

Left front:

 

 

Right front:

 

 

Center:

 

 

Here is how to interpret the results.  Take the center speaker as an example.  The in-room un-corrected response (i.e. Audyssey off) shows nice peaks at 60Hz and 150Hz.  The preout measurement (which shows the correction Audyssey is applying to the center channel signal) shows inverse peaks at the same two frequencies.  The post-Audyssey in-room response shows that the Audyssey correction has completely erased both peaks, resulting in a nice smooth response.

 

Pretty cool, no?  Are we liking REW now?

Way cool, Jerry!

Quote:

Originally Posted by sdrucker 

 

OK, this kills my remaining angst over moving from OmniMic...
 

OmniMic is beautifully simple - but it's a Nissan compared to REW's Ferrari IMO.