# REW Newb, first set of measurements in ded. listening room



## toddrhodes (Oct 13, 2013)

Hi all, hopefully this is ok to post here, if not please delete mods.

I built a small, treated room in my basement for my 2.2 setup. It's 12.5 x 9.5 with a 9' ceiling. Ceiling is unfinished with insulation stuffed in between the joists to damp sound to the above room (unfortunately our master bedroom, lol). I have 3 DIY OC703 2' x 4' x 4" thick traps, each is in a corner of the room just leaning into the corner. I also have a 2' x 4' 6" thick OC703 trap hanging on the back wall, about 3' from my listening position.

Speakers are sitting on top of anti-vibration pads and then on top of the subs. Speakers are DIY ScanSpeak, 3-way front ported, subs are 12" ported. Speakers are about 2' from side walls, 3' from front wall, and roughly 6' apart.

Mic is an EM-6 with MLX Mic Mate, pointing straight up at my listening position. I'm not great at interpreting these graphs but based on the RealTraps tutorial, it *seems* like I'm doing ok, at least for a first pass. Any thoughts on the below graphs, or are there other graphs/measurement files I can include to help? Thanks for any input, truly!

No Smoothing









Var Smoothing:









RT60









Waterfall (this is probably the best graph):









Er - been called upstairs for a minor emergency, will have to finish this up later 

Thanks again !
Todd


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## AudiocRaver (Jun 6, 2012)

Did you measure with both speakers running at once?

Always measure one speaker at a time. You can measure L, L + sub, R, R + Sub, Sub alone.

Then scale you graphs to cover 60dB total. 15 Hz to 22 kHz, 45 dB to 105 dB.

Point the mic at the speaker under test, unless you have a .cal file for 90° orientation.

You're off to a good start.:T


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## toddrhodes (Oct 13, 2013)

AudiocRaver said:


> Did you measure with both speakers running at once?
> 
> Always measure one speaker at a time. You can measure L, L + sub, R, R + Sub, Sub alone.
> 
> ...


I did measure the entire system at once. I actually tried to use Dirac Live last night and wasn't able to get it running on my Audio PC but in the sense that I had my mic and stand all set, and I have dabbled in REW before, I decided to test the whole system out with REW to see if it matched up to what Dirac's calibration tool said which really wasn't too far off of what REW produced.

When I'm mic'ing just one speaker and/or one sub at a time, I assume that's for EQ purposes, but I've been concerned that my back wall, the left side of it angles on probably a 140* angle or so to the left wall (this wall has a door on it) so I *think* some time alignment may be in order. But that's probably getting ahead of myself at this point. Also, would I mic both speakers and/or subs individually at the listening position, or close-mic them?

Thanks for the encouragement!
Todd

Edit, I see you already answered my question about how to orient the mic. I'll try to give this a go tomorrow. Is there a way to "universally" scale the graphs per your recommendations, or is that something where I should use the "controls" dialog to set those parameters for each graph? Sorry for the 20/20 questions


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## AudiocRaver (Jun 6, 2012)

toddrhodes said:


> I did measure the entire system at once. I actually tried to use Dirac Live last night and wasn't able to get it running on my Audio PC but in the sense that I had my mic and stand all set, and I have dabbled in REW before, I decided to test the whole system out with REW to see if it matched up to what Dirac's calibration tool said which really wasn't too far off of what REW produced.
> 
> When I'm mic'ing just one speaker and/or one sub at a time, I assume that's for EQ purposes, but I've been concerned that my back wall, the left side of it angles on probably a 140* angle or so to the left wall (this wall has a door on it) so I *think* some time alignment may be in order. But that's probably getting ahead of myself at this point. Also, would I mic both speakers and/or subs individually at the listening position, or close-mic them?
> 
> ...


Always one speaker at a time (or speaker + sub), for any and all purposes.

Measure with mic at the LP, point the mic at the speaker (or at the center point halfway in between so you don't have to move it between measurements).

Scaling: Scale settings are remembered for each pane type in REW. So for _All SPL_ pane, click on *Limits*, enter the numbers for each scale limit (105 dB, 15 Hz, 22 kHz, 45 dB), click on *Apply Settings*, and those values will always be used for that pane until you change them or zoom in/out or R-click/drag the window. You would have to do this again (just once) for the *Overlays* > *SPL* window, for instance. If you have a deep sub, use 5 Hz instead of 15 Hz.

When you want to save a .jpg of a measurement pane, click on the camera icon, always use 800 pixel Image Width to publish on the forum.


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## toddrhodes (Oct 13, 2013)

Tonight I ended up measuring left and right independently, including sub/main independently. What an eye opener. I was able to EQ the right channel to a much smoother line, at least from 20-200 Hz. It gets pretty spikey after that but only for very short intervals and honestly, those seemed to change from measurement to measurement. I drove my wife crazy tonight running constant 20-1000 sweeps  Anyway, I figured ok, right channel is done - let's see if the EQ settings I applied for both channels help the left out just as much.

NOPE.

So that was another hour and 45 minutes, doing that side completely separately. It dropped off a cliff at 45 Hz. Oddly enough, gaining down at about 42 and 52 Hz by 3,4 dB actually solved that issue. Weird, but it was repeatable. Same thing at 90 Hz on the left side - a big dip from about 70-110, I was able to smooth that out quite a bit, then another one at about 160. Definitely seems like I have a mode issue around the 40 Hz area but I tried changing speaker and treatment positions with no real effect. Changing the mic location forward or back by 18" made a huge difference in how smooth the response was, so ultimately I am sitting forward a few inches from where I was.

I didn't grab most of the data tonight, I had to run all this from the Audio PC which is enough of a hassle and it's getting late. Needless to say, "trusting thy ears" is great and I'd never discourage anyone from doing so - ignorance is bliss when it comes to this stuff. But, put yourself out there and measure your room - you may just be surprised and learn a thing or two in the process!

Todd


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## jtalden (Mar 12, 2009)

Todd,
I just looked at the file attached to Post 1. The soundcard cal file that is active for those measurements appears to be a speaker measurement. It has badly distorted the measurements. It should be removed in REW 'preferences' if you haven't done that already. Most all soundcards are accurate enough without a cal file created. If you want to create one again, just remove the mic and attach a loopback cable from right output to right input and follow the instructions. After the new cal file is created and loaded in REW then the cable can be removed and mic plugged back into the right input for new measurements.


To see the impact on the old measurements you can remove the soundcard cal from the old measurements one at a time using the REW 'measurement panel'.


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## toddrhodes (Oct 13, 2013)

jtalden said:


> Todd,
> I just looked at the file attached to Post 1. The soundcard cal file that is active for those measurements appears to be a speaker measurement. It has badly distorted the measurements. It should be removed in REW 'preferences' if you haven't done that already. Most all soundcards are accurate enough without a cal file created. If you want to create one again, just remove the mic and attach a loopback cable from right output to right input and follow the instructions. After the new cal file is created and loaded in REW then the cable can be removed and mic plugged back into the right input for new measurements.
> 
> 
> To see the impact on the old measurements you can remove the soundcard cal from the old measurements one at a time using the REW 'measurement panel'.


Ahhh, that makes sense. The last time I played with REW was a few years back and I was using an M-Audio external sound card and I do recall doing the loop-back thing for calibration. I'll go ahead and remove the calibration and re-run the sweeps tonight to see how much things change afterward. Thank you for the heads up!

Todd


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## AudiocRaver (Jun 6, 2012)

jtalden: Good catch, thanks, I missed that.


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## toddrhodes (Oct 13, 2013)

While I won't say it was too much easier , the results were far more "predictable" as it were. I still struggle with getting the WDM driver for JRiver to not click/pop at times but it's so nice to be able to see how PEQ settings affect the over curve. Now, I'll be honest - I have noted the reference points for the subs but I have increased them 15-20%, just by ear, to get the "house curve" I prefer. I like bass, and won't apologize for it 

Regardless, I really appreciate the assistance, I've included the measurement file again in case anyone wants to take a look. I didn't post any pictures of the spectrogram or waterfall but, to me, they still look pretty good. Also, with the advice given I was actually able to position my room treatments and see how they affected the sound, the first reflection panels were not up at first but putting them back in place smoothed things out going past the 300 Hz region. Now, it still looks awfully jagged to me but maybe that's just how it normally is? I have a small room so I'm sure that doesn't help.

Current treatment arrangement:

each side wall has a 2' x 4' treatment
front left corner, directly opposite my diagonal wall has a 2' x 4' leaning up against it, acting as much as a bass trap as anything.
Back right corner has a trap as well
Back wall has the 6" trap hanging about 3' from my listening position.

The listening position was especially neat to play around with. Moving the microphone in about a 30" path closer or farther from the speakers made significant changes to the overall response. I settled on the best spot in terms of the graph. Sounds great to me 

Thanks again, 
Todd


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## AudiocRaver (Jun 6, 2012)

The plots all look sensible and valid. Allowing for your house curve with accentuated bass, your plots are reasonably smooth and are well matched. 

In your .mdat file, the second-to-last plot shows very high distortion, > 10%. It might have been something rattling when the measurement was made. It appeared at a resonant frequency during that measurement. Something to check on.

You have a couple of big reflections at 3.7 mS and 5.2. mS. That is a bit on the early side, but they match extremely closely between L and R sides. Depending on arrival path, they could be hurting soundstage and imaging or they might be just fine.


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## toddrhodes (Oct 13, 2013)

I do have a 58" glass-front plasma TV sitting about 3' behind the mains, roughly equidistant from each. I could re measure with a thick blanket over the TV to see if that changes the ETC readings but first I need to read up on how to interpret those graphs. Also I can move my first reflection point treatments to see if those have any impact. Any suggestions for a resource to read about ETC graphs?

Many thanks for the help!!

Todd


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## toddrhodes (Oct 13, 2013)

fjc20 said:


> hey john cant quote you yet on the forum but I seen that and that's what I used to get started. I only have the choice of HDMI 1, and HDMI 2. not the full 8 channels.


If you wouldn't mind could you start a seperate thread please? Thanks!


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## JohnM (Apr 11, 2006)

Posts moved here.


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## toddrhodes (Oct 13, 2013)

Here are my latest measurements - all Filtered IR ETC curves. Frankly, these look almost too good to be true to my beginner eyes but maybe the room is a little too dead...? Or maybe I'm graphing incorrectly, that certainly could be it. I've included the measurements file per usual - do not pay attention to frequency response with this set, I just used my normal speaker outs on my "main" PC, not the PC with JRiver doing PEQ so FR is all over the place.

This is with two front wall, two side wall, and one thick rear wall treatment it place. I've repositioned this stuff a dozen (or 10 dozen) times and this conventional setup just works. Now, I was getting far worse ETC's with no or slight toe-in. So I went all the way and toed them in with the help of a laser level such that they cross in front of me. Rather extreme toe-in but seemingly as soon as I did that, everything leveled out nicely IMO.

I initially set the Filtered IR limits to be Left: 0, Right .03, Top 0, Bottom -60 but doing so the top of the initial spike wasn't visible and I thought that might come in to play so I ended up making the top 60 and kept bottom at -60 which seemed to help.

Once again, thanks for all the tips, it's rather amazing what this software can do! And yes, I need to donate toot sweet 

Edit - I do find it odd and inexplicable why taken separately, I don't get that second very quick impulse (toe in does affect how close I get it to the very first spike, interestingly) but when played together, it appears. This has occurred whether I toe them out, straight on, slightly in, or extreme as I have them right now.


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## AudiocRaver (Jun 6, 2012)

Above 500 Hz, your curves match really well. There are some modal issues to be dealt with. It is kinda hard to say about reflections.


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## JohnM (Apr 11, 2006)

The second peak when you play both speakers is from the further speaker, the distances to each from the mic would need to be identical to have a single peak.


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## toddrhodes (Oct 13, 2013)

JohnM said:


> The second peak when you play both speakers is from the further speaker, the distances to each from the mic would need to be identical to have a single peak.


Thank you John, I ended up playing around with the right channel position - it was about an inch or 1.5" off from the left, now it looks better at least in that respect. I also now see the value in pointing the microphone up vs at the speakers, the previous ETC plots were pointed toward the front of the room. The graph attached here is pointing up, much easier to see what's going on (I think).

Thanks again!
Todd


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