# REW with JBL LSR 5.1 system



## GrizzlyAK (Dec 5, 2015)

OK, I'm brand new to REW and this is my first post. :wave: I have aligned my surround system in my room for movie post production using the standard 5.1 approach (mostly volume adjustment at the listening position). But first, my setup: I have 5 JBL LSR6325p studio monitors for my LCRLsRs channels, and the JBL LSR6312SP as my sub. Bass Management is turned on. This sub has 4 inputs and 3 outputs. The LCR channels run from the Audio Interface (MOTU Ultralite mk3 hybrid) to the sub, where the sub high-passes the signal before outputting those 3 channels to the respective LCR speakers. The sub takes the lower frequencies split from the LCR channels and plays it through the sub. The sub has a 4th input dedicated to the .1 (LFE channel), which is completely removed from any bass management. It adds that signal as is to any signal scraped off the LCR. The Ls and Rs channels do not pass through the sub, but are connected directly to the audio interface.

Given that, after reading the REW manual cover to cover, I'm struggling :yikes: to figure out how REW can help me improve my room acoustics and especially with how to use it with my setup. Any advice as to the basic steps to follow for my particular system, and particularly which steps would be helpful to utilize (and which steps I can ignore of all the various REW capabilities), would be greatly appreciated. :dontknow:

Thanks,
Shane


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## AudiocRaver (Jun 6, 2012)

A good starting point would be to take measurements of left, Center, and right channels, one at a time, with no sub or bass management active. Also take a measurement of subwoofer with no bass management active. Then take separate measurements of left + sub, Center plus sub, and right Plus sub each with bass management active. That that would give us a good view of your starting point.


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## GrizzlyAK (Dec 5, 2015)

AudiocRaver said:


> A good starting point would be to take measurements of left, Center, and right channels, one at a time, with no sub or bass management active. Also take a measurement of subwoofer with no bass management active. Then take separate measurements of left + sub, Center plus sub, and right Plus sub each with bass management active. That that would give us a good view of your starting point.


Thanks Wayne. I guess one of the things I'm trying to understand is what exactly am I trying to do with REW. I don't understand really what taking the measurements separately will do for me. It seems like since, while mixing, I'll be using all 5 mains and the sub, including bass management, isn't that the configuration that I should be measuring and trying to 'correct' at the listening location? I would expect that any combination other than that would give me readings and different room effects that don't really need correcting by themselves, and different from the combined effect of all speakers playing together. Although I guess if you could address each channel separately, correcting each as best I could, but I can only apply an EQ to each output channel PAIR in my Audio Interface, not each channel individually (which is a bummer). What is it that we would learn from the individual measurements you suggest in light of the end goal of overall correction at the sweet spot? Sorry if I've misunderstood something.

Cheers,
Shane


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## Wayne A. Pflughaupt (Apr 13, 2006)

You want individual measurements of the main-channel speakers so you can get as “clean” a reading as possible. Measuring all five at once, the signal will be hitting the mic at different times, and the resulting comb filtering that will give an reading that’s useless for all practical purposes. 

In addition, unless the placement for all speakers is 100% symmetrical in room, each will show different frequency response characteristics, especially below 400 Hz or so where the room starts having an effect. You won’t get the individual information with a combined measurement.

Regards,
Wayne


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## GrizzlyAK (Dec 5, 2015)

That makes sense, Wayne. But I'm still a little confused how that is going to help me. My ultimate goal is to have as flat a response as possible at the listening position when all 5 speakers and the sub are playing at once. Even if I do calibrate and EQ each speaker individually, that won't eliminate the combing I'll get, or other interference when actually playing a theatrical mix through all my speakers at my mix position. 

So, doing what you suggest, once I get a clean reading for each speaker individually, what do I do with that information? It would seem that in my case I'd want to get the frequency response of the sound field at the listening position with all speakers playing, since that is what will be happening while mixing. I guess I just don't understand how other folks are using REW.


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## GrizzlyAK (Dec 5, 2015)

OK, so I think I've successfully calibrated the Audio Interface, checked levels, and took a measurement. The attached images are from that measurement of the Center Main + the Sub (bass managed). Room is 10.5' D x 16' W x 7.5' H. Listening position is almost midway in the short dimension (10.5'), and about 40/60 split along the long dimension. Ear height 4' and distance to speaker is 4'. Any help interpreting these would be appreciated.

































































Thanks,
Shane


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## willis7469 (Jan 31, 2014)

Hi Shane. I'm not exactly sure of your situation, but I think what Waynewave) is getting at is playback content won't likely be the same for all 5 channels simultaneously, so the combined response doesn't matter. As far as the graphs go, I'll only take a shot at the spl graph. It looks to my lamens eye like phase issues between 65hz and 250hz. I'd try moving the phase control, sub distance in the avr, or move the sub. Pick one of those and remeasure. Rinse and repeat. If I'm off, I'm glad to be corrected. 
Edit: what are you going to be mixing?


Sent from my iPhone using Tapatalk


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## GrizzlyAK (Dec 5, 2015)

willis7469 said:


> Hi Shane. I'm not exactly sure of your situation, but I think what Waynewave) is getting at is playback content won't likely be the same for all 5 channels simultaneously, so the combined response doesn't matter. As far as the graphs go, I'll only take a shot at the spl graph. It looks to my lamens eye like phase issues between 65hz and 250hz. I'd try moving the phase control, sub distance in the avr, or move the sub. Pick one of those and remeasure. Rinse and repeat. If I'm off, I'm glad to be corrected.
> Edit: what are you going to be mixing?


Thanks, I'll give that a try. What you said about playback makes good sense. I don't know why I have the impression that it should be done that way, or that it does matter. I'll have to go back to the post production audio forums and see if I can track down the source of that 'thinking'. 

At any rate, I'm mixing the soundtrack for a short film, so dialog, foley, sfx, music, atmos, etc.

Is the goal with REW to measure one speaker in your room and build an EQ curve for your system, or ONLY for that speaker (and repeat for the others)? It may not matter for stereo, I don't know.

Thanks for your response.

Cheers,
Shane


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## willis7469 (Jan 31, 2014)

Sounds like fun. I've always been interested in the process of movie making. 
My experience with REW might be just enough to get you into trouble. Lol. I believe you want to EQ each channel separately for flat response at the LP. If you do end up having simultaneous output from some of the channels, and therefore phase cancellation/peaking issues I couldn't say how much it would hurt, but I think it would be lessened by being EQ'd first. Room treatments may be able to help but I'm not qualified to say how much. 


Sent from my iPhone using Tapatalk


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## AudiocRaver (Jun 6, 2012)

Your distortion graph is almost too horrible to believe, meaning if your distortion in actual use is as bad as the graph shows (20 to 30 %), your first question would have been, "Why does my system sound so distorted?" I wonder if some part of your measurement setup is being overdriven, which would make all of those measurements invalid. That graph should show a difference of around 40 dB or more between the fundamental and all the harmonics, above 100 Hz (corresponding to 1% distortion), and 20 dB or more below 100 Hz (10%).


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## AudiocRaver (Jun 6, 2012)

GrizzlyAK said:


> Thanks Wayne. I guess one of the things I'm trying to understand is what exactly am I trying to do with REW. I don't understand really what taking the measurements separately will do for me. It seems like since, while mixing, I'll be using all 5 mains and the sub, including bass management, isn't that the configuration that I should be measuring and trying to 'correct' at the listening location? I would expect that any combination other than that would give me readings and different room effects that don't really need correcting by themselves, and different from the combined effect of all speakers playing together. Although I guess if you could address each channel separately, correcting each as best I could, but I can only apply an EQ to each output channel PAIR in my Audio Interface, not each channel individually (which is a bummer). What is it that we would learn from the individual measurements you suggest in light of the end goal of overall correction at the sweet spot? Sorry if I've misunderstood something.
> 
> Cheers,
> Shane


As pointed out, the problems with taking those measurements all at once are:

Phase interaction between the speakers at the measurement mic can give you large "apparent" variations in frequency response which in reality do not exist, except when you are sitting listening to sine waves from all speakers at once. I am hoping your film soundtrack will not involve too much of that.:yikes:
A very small change of position of the measurement mic will give you a very different set of measurements.
You will glean no useful information toward making changes to your room or system.
Agreed, it is not intuitively obvious on the surface, but the only useful measurements are one speaker at a time (subs are a special case). If anyone told you specifically you should do it that way, take NO more audio advice from them! EVER!:rolleyesno:

It is only when you consider what is happening acoustically in your room with the same measurement signal coming from multiple speakers at once, that there will be - at mid and higher frequencies - phase cancellations which cause erratic measurements which are virtually unrepeatable, that it starts to make sense.


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## Wayne A. Pflughaupt (Apr 13, 2006)

GrizzlyAK said:


> That makes sense, Wayne. But I'm still a little confused how that is going to help me. My ultimate goal is to have as flat a response as possible at the listening position when all 5 speakers and the sub are playing at once. Even if I do calibrate and EQ each speaker individually, that won't eliminate the combing I'll get, or other interference when actually playing a theatrical mix through all my speakers at my mix position.


The reason we don’t pay attention to anechoic response is that the room will ultimately alter the speaker’s response. That’s why we want a measurement of the speaker in the room, taken at the listening position. Equalization can compensate for at least some of what the room adds. And also, many speakers don’t have especially flat response out of the hole, and equalization can make improvements, too. Basically, EQ can’t make a bad speaker sound great, but it can make a good speaker sound better.

Comb filtering is not anything to be concerned about. You’re going to get it in any room except perhaps an anechoic chamber, and the more speakers you add, the more of it you’re going to get. All it is, is reflected sounds arriving at the measurement mic later than the original signal. Fortunately our ears are more forgiving than a measurement mic, and easily “discount” most reflections in a reasonably-dampened room. More reading on the subject here: http://www.madronadigital.com/Library/RoomReflections.html

And actually, ruler-flat response is typically not the best idea, as it sounds bad to most people. Most rooms need a so-called “house curve.” On top of that, going overboard with equalization trying to wrangle flat response often ends up with things sounding worse rather than better. You can find material on these subjects in my signature.

Speaking of flat response, your center channel reading is simply amazing. What speaker is that?

Regards, 
Wayne


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## GrizzlyAK (Dec 5, 2015)

AudiocRaver said:


> Your distortion graph is almost too horrible to believe, meaning if your distortion in actual use is as bad as the graph shows (20 to 30 %), your first question would have been, "Why does my system sound so distorted?" I wonder if some part of your measurement setup is being overdriven, which would make all of those measurements invalid. That graph should show a difference of around 40 dB or more between the fundamental and all the harmonics, above 100 Hz (corresponding to 1% distortion), and 20 dB or more below 100 Hz (10%).


AudiocRaver, I'm not sure. I'm just about to post some new measurements after doing some EQ and changing some DIP switch settings on my speakers. The distortion graphs look much different, and although I don't really know what I'm looking for in them, they seem to better match the numbers you quote in your post above.

Thanks,
Shane


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## GrizzlyAK (Dec 5, 2015)

AudiocRaver said:


> As pointed out, the problems with taking those measurements all at once are:
> 
> Phase interaction between the speakers at the measurement mic can give you large "apparent" variations in frequency response which in reality do not exist, except when you are sitting listening to sine waves from all speakers at once. I am hoping your film soundtrack will not involve too much of that.:yikes:
> A very small change of position of the measurement mic will give you a very different set of measurements.
> ...


OK, this is beginning to sink in, finally. I think I get it. Thanks! :T :bigsmile:


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## GrizzlyAK (Dec 5, 2015)

Wayne A. Pflughaupt said:


> Speaking of flat response, your center channel reading is simply amazing. What speaker is that?


Wayne, my surround monitoring system is the JBL LSR6325SP 5.1, which consists of 5 LSR6325Ps and the LSR6312SP sub. I'm pretty pleased with them. I looked at the 6328s for a lower end on the mains, but the cost was much greater, and advice from the JBL rep indicated that the 6328's would be overkill for my room (10.5' x 16' x 7.5').

I'm going to post some new measurements next, which hopefully show better results, and for all 5 speakers.

Cheers,
Shane


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## GrizzlyAK (Dec 5, 2015)

OK, so I've spent a bit of time trying to flatten things out a bit. 

A little about my setup first: My room is still completely untreated, in regard to acoustic treatment products. I have a couple of bookcases full of books and other furniture covering most of the walls, except the right side wall. My back wall has a roof slant ceiling which takes the top 3 feet off the back wall and reflects sound to the floor. My tweeters are about 9" above my ear height, tilted down pointing directly at my ears, and all 5 mains are exactly 48" from my head (ITU surround setup). My sub sits in the front left corner and I ended up rotating it 90 deg from the way I had it so that its back is against the front wall firing toward the back. I implemented the sub's RMC function to eliminate a large Node at about 60 Hz with a 20 dB cut.

All channels run from my MOTU UltraLite mk3 Hybrid audio interface (Firewire), with LCR running first to the sub to be HPed at 80 Hz (with the lows from each front reproduced by the sub) before the HP signal is fed on to those three speakers. The Ls and Rs are directly connected to the MOTU, and therefore those signals will roll off as 65 Hz (-3dB), 56 Hz (-6 dB), 48 Hz (-10 dB). That can be easily seen in the measurements.

I've included a jpeg of my MOTU interface, showing the EQ set for each output PAIR. As I can only EQ pairs of outputs (even though they are really distinct channels), I have Main 1-2 sent to LR, Analog 1-2 sent to CLFE, and Analog 3-4 sent to LsRs. This allowed me to set 3 different EQs for the LR, C, and Surrounds, respectively. I'm assuming, although I haven't tested it yet, that the correction of the low end from the LCR channels running through the sub will likewise correct the direct LFE channel as well without ill effect. The LFE channel has a +10 dB boost at the sub per Dolby standards. The individual EQ settings for each of the three PAIRs in MOTU are listed in the comment field for each measurement as (Freq:Gain:Q), if interested in what these were. The 'treatment on the rt wall' consisted of a few blankets hanging against it, covering it completely. It made no difference. Could the extent of some of these EQs be causing other issues that aren't showing up in the graphs? All of them made the SPL graphs 'flatter'.

My take: I've been able to produce a pretty flat response from each speaker (surrounds roll off early on low end as expected, and I'm not sure what's going on with the LsRs lows below 100 Hz where they appear to be out of phase :blink: ). Waterfall appears OK (to me), although a little ringing in the lows in LCR, but down by at least 40 dB by 300 ms. Everything above 200 Hz is dead by about 175 ms and is relatively even. Distortion seems to be better with over 40dB separation above 100 Hz. If I'm reading my Filtered IR correctly, my RT60 is less than 150 ms, with all plots reaching -60 dB by that time. I do see a few first reflections which I've verified with my own distance measurements and calculations. I could probably treat those with something if needed.

At any rate, I know it's a lot to ingest, but I'd really appreciate a review of the MDAT (attached) and any advice or comments as to what you guys see and think. :rubeyes:

Thanks!!

Cheers,
Shane
View attachment Measurements - 3 (UPLOAD).mdat


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## Wayne A. Pflughaupt (Apr 13, 2006)

GrizzlyAK said:


> Wayne, my surround monitoring system is the JBL LSR6325SP 5.1, which consists of 5 LSR6325Ps and the LSR6312SP sub. I'm pretty pleased with them.


Wow, can't say I've ever heard of those. Pretty pricey stuff, but I guess outstanding response like that doesn’t come cheap. I can’t say I’ve ever seen any speaker reviewed by Sound and Vision graph that good, no matter what the price. If they sound anywhere near as good as they measure, they must sound awesome!

Regards, 
Wayne


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## Wayne A. Pflughaupt (Apr 13, 2006)

It all looks pretty good to me, at least the frequency response. :T I don’t pay much attention to anything else.



GrizzlyAK said:


> (surrounds roll off early on low end as expected, and I'm not sure what's going on with the LsRs lows below 100 Hz where they appear to be out of phase :blink: ).


Are you talking about the way one drops below 100 Hz and the other doesn’t drop until 70 Hz?

Regards, 
Wayne


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## GrizzlyAK (Dec 5, 2015)

Wayne A. Pflughaupt said:


> Are you talking about the way one drops below 100 Hz and the other doesn’t drop until 70 Hz?


Yes. I don't understand what's happening there. These speakers roll off at 70 Hz as 65 Hz (-3dB), 56 Hz (-6 dB), 48 Hz (-10 dB). Even the Green curve (Rs) is being damped more than that, and the Gold curve (Ls) drops off way early, only to rise again by 45 Hz. Very odd (to me).

Although, now after thinking about this a bit, I think that the Ls (Gold), which is close to the left wall similar to the subwoofer, may suffer from the same modes the sub-woofer did that I tamed for the front (bass-managed) channels. There was a big (+15 dB) and wide (30 Hz to 70 Hz) bump in all the LCR channels until I implemented Room Mode Control on my sub, which allowed 14 dB, wide cut centered on ~50 Hz. Perhaps the Ls is setting up a similar mode, also boosting the signal at the listening position at ~50 Hz. Could that also explain why it is rolling off early?

Thanks for the feedback, Wayne. :T

Cheers,
Shane


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## GrizzlyAK (Dec 5, 2015)

Wayne A. Pflughaupt said:


> Wow, can't say I've ever heard of those. Pretty pricey stuff, but I guess outstanding response like that doesn’t come cheap. I can’t say I’ve ever seen any speaker reviewed by Sound and Vision graph that good, no matter what the price. If they sound anywhere near as good as they measure, they must sound awesome!


That's good to know! :yikes:

They are pricey for a budding (but not young) filmmaker, but about the cheapest I could find for a nicely integrated 5.1 surround system. Plus, it's hard to beat JBL. So, that's why I'm trying my best to get the most out of them so my short film mix ends up sounding decent in a theater (hopefully) at a festival somewhere. Coming to this as a career scientist/researcher (retired), I've taken my time and learned as much as I could about every aspect of filmmaking on this project over the last year, from writing the script, production, directing, photography, sound field recording, picture editing, sound / dialog editing, ADR, Foley, creating my own sound fx (still working on that ), and now final mix. It's been a long, fabulous journey, and I just want to get this part right. I know how important sound is to a film.

Cheers,
Shane


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## Wayne A. Pflughaupt (Apr 13, 2006)

GrizzlyAK said:


> Although, now after thinking about this a bit, I think that the Ls (Gold), which is close to the left wall similar to the subwoofer, may suffer from the same modes the sub-woofer did that I tamed for the front (bass-managed) channels.


Bingo. The low end of two identical speakers very often measures differently, unless their placement in the room is symmetrical.

By the way, good luck with your project! :T

Regards, 
Wayne


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## AudiocRaver (Jun 6, 2012)

It all looks pretty good to me. Distortion measurements look a lot better, too. Well done. Time to mix a film soundtrack!


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## GrizzlyAK (Dec 5, 2015)

AudiocRaver said:


> It all looks pretty good to me. Distortion measurements look a lot better, too. Well done. Time to mix a film soundtrack!


Thanks Wayne!! :T


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