Using REW to test and tune my home theater acoustics

All about acoustics. This is your new home if you already have a studio or other acoustic space, but it isn't working out for you, sounds bad, and you need to fix it...
amurguia
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Using REW to test and tune my home theater acoustics

#1

Postby amurguia » Wed, 2020-Aug-05, 14:10

GREAT thread. Exactly the info I was looking for so thank you.

Hey, I'm a newb. I don't know what healthy graphs look like. I just calibrated my soundcard following the instructions. Does this measurement look like a healthy soundcard? I'm including images with no smoothing and with var smoothing. The soundcard is a Sennheiser GSX 1000.

Sennheiser_VarSmoothing.jpg
Sennheiser_NoSmoothing.jpg


Sorry if I posted in the wrong place!
Thank you!



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Soundman2020
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How To Calibrate and Use REW To Test and Tune Your Room Acoustics

#2

Postby Soundman2020 » Wed, 2020-Aug-05, 14:55

Hi there, and welcome to the forum! :) :thu:

I have moved your post from the original location (it was here: viewtopic.php?f=9&t=5 ), to his location, since this is the best place for it.

We would need to have the actual MDAT data file that REW created, to be able to answer your question. You can upload that directly to another post... but only after you post one more thing first! The anti-spam system on the forum is set to require that your first two posts must be approved by a moderator, and can only have certain attachments, but after your second "approved" post then those restrictions are lifted. So please post more details about your room (maybe a diagram and some photos), so I can approve that, then in the next post afterwards attach your MDAT file.


- Stuart -



amurguia
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How To Calibrate and Use REW To Test and Tune Your Room Acoustics

#3

Postby amurguia » Wed, 2020-Aug-05, 19:11

Excellent! Thanks for moving the post to the right place.

I have two systems in a small 20' x 15' room. It's not an ideal home theater room, but it is pretty rectangular.

Marantz System:

1x Marantz AV8802A
2x Marantz M8077
1x Def Tech SubAmp 600
1x Furman Elite Power Conditioner
1x Oppo UDP-205
1x Def Tech CS9080 Center Channel
2x Def Tech DI 6.5LCR
2x Def Tech UIW RSS III Surrounds
2x Def Tech UIW RCS III Rear Surrounds
2x Def Tech IW Sub 10/10 Subs
4x Def Tech DI 6.5S Height

IMG-4200.jpg
IMG-4196.jpg
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IMG-4195.jpg
IMG-4198.jpg
IMG-4190.jpg
IMG-4189.jpg
IMG-4193.jpg
IMG-4194.jpg
IMG-4188.jpg


I wish I could tune those subs separately, I can't. The strangest speakers are the rear surrounds.

Computer System:

Pair of AudioEngine A5+
Sennheiser GSX 1000
SVS SB-3000 (arrives tomorrow)

IMG-4191.jpg
IMG-4192.jpg
IMG-4202.jpg


Thanks!



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How To Calibrate and Use REW To Test and Tune Your Room Acoustics

#4

Postby Soundman2020 » Wed, 2020-Aug-05, 20:24

Great! :thu:

...in a small 20' x 15' room.
Ceiling height? Sound spreads out and bounces around in all three directions, so it is important to know about the height too. 20x15 is reasonable: 300 square feet can be quite good, acoustically.

It's not an ideal home theater room, but it is pretty rectangular.
:thu: Rectangular is good!

So, from what I can see, there's no visible acoustic treatment in your room right now. Correct?

I'm also assuming that your intention here is to treat the room so that it works well as a home theater?

- Stuart -



amurguia
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How To Calibrate and Use REW To Test and Tune Your Room Acoustics

#5

Postby amurguia » Wed, 2020-Aug-05, 23:02

The ceilings are 8 feet. I can't really sound treat it, unfortunately. This is the family room so it has to stay "in tact" for now. That's the reason I can't have two svs 16 ultras in there and have to hide the sb-3000 under the desk.

I attached that sound card file.

For speaker calibration on the home system, I have been using Audyssey on the AVR. But now that I have REW and the UMIK-1 I'd like to start looking at what's going on and perhaps adjust. Def Tech crossover specs are always a bit suspect I find :-)
Attachments
Soundcard.mdat
(3.1 MiB) Downloaded 890 times
Soundcard.mdat
(3.1 MiB) Downloaded 890 times



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#6

Postby Soundman2020 » Wed, 2020-Aug-05, 23:44

amurguia wrote:Source of the post I attached that sound card file.
Hmmm... there's an issue there with the way you did the setup and calibration, it seems. This is what your data file is showing:
amurguia-REW--Soundcard-issue.png
This is what a typical soundcard should look like:
good-soundcard-2-MKCAN.png
It looks like you might have a feedback loop within your soundcard itself. Check the settings for your card, to see if there is maybe a headphone feed or something like that, that is turned on when it should not be. Also check that you had your loop-back cable connected correctly, from the speaker output connector on your computer, back to the mic input connector. Another thing to check: that you have the correct output and input selected on the REW "preferences" panel: if you have several inputs or outputs, it's easy to accidentally select the wrong one.

Something is up there, and you'll need to fix it before you can take any measurement, validly.

I can't really sound treat it, unfortunately. This is the family room so it has to stay "in tact" for now.
Unfortunately, without at least some treatment in there, it's not going to be a good listening environment, to do justice to all that gear and those speakers that you have. Treatment can be disguised to fit into the room decor, so that shouldn't be a problem. Or it can be made portable, so you can store it some other place most of the time, then just carry it in when you want to watch movies, or listen to music. Many, many people don't realize how necessary treatment is in a home theater... until they hear what a room sounds like with good treatment in it! There's a huge difference: night and day.

There's also the issue that you can't actually use EQ successfully for the majority of problems you will have in your room, because they are acosutic issues, caused by the sound waves moving around the room and interacting with each other: EQ cannot correct that, because it happens after the sound waves have already left the speakers. EQ can only fix problems that happen before the sound leaves the speakers, as well as a very small, very limited set of acoustic things.

The mistake many people make, when they read the glossy brochures on "Room Correction" software or hardware, is not realizing that the manufactures of those products are not telling you the truth: they make it sound like you can just plug in their product and magically make a bad room sound good: that simply is not true. It does not work like that: the laws of the universe prevent that from being true. You can only use those EQ products successfully after the room has already been treated acoustically, to deal with the typical basic issues that all small rooms have. One those are dealt with bu the treatment, then the EQ can be used to iron out many of the remaining issues.

What most people find when they first use such a product, is that the do the analysis, fiddle with the controls, and the curves on the screen get a bit flatter... but then they are disappointed because the room still sounds like garbage! They look at the screen, see the curves flatter, and think that this MUST be an improvement... except that it isn't! The problem with the room is not in the "frequency domain", which is what a frequency response graphs shows you, but rather the problems are mostly in the "time domain", which you cannot see on a frequency response graph! "Time domain" refers to how sound bounces around the room and slowly dies away after it has left the speaker. That is not visible by looking at the frequency graph... or rather, you can see some of the effects in the frequency graphs, but you can't see the actual problem. That's where REW comes in: it shows you the frequency graph, yes, but that's not the most important one. REW also shows you a whole bunch of time-domain graphs, such as the waterfall plot, the spectrogram, the decay plots, the RT60 plots, and most important of al (but hard to understand); the "Impulse Response" graph, set to "ETC" mode. ETC means "Energy-Time Curve". It shows you how the sound energy in the room is behaving over time. Not easy to read (waterfall is much simpler to understand), but very useful.

As you start using your EQ to try to fix the room problems, you will run into all of these issues: there will be some that you just can't fix at all, no matter how hard you try, and some that seem to improve when you fiddle with the EQ.... but only for one seat in the room! As you sit in different spots, you'll hear different sound... because that's the other thing that the manufactures don't tell you! EQ in an untreated room will, at best, only improve the sound at one single location in the room... at the expense of all others! Things can be better for that one spot, but will be worse for all other locations in the room. That's fine or a recording studio control room, where the mix engineer is the only guy who needs to hear perfectly, and always sits at that "sweet spot" in any case. But it's not so fine for a home theater, where you usually have several people who want to hear well...

Anyway, excuse the long explanation, but I just wanted you to be aware of what you are going to find out soon enough when you start using your EQ. And to urge you to consider doing some simple, basic treatment to improve the acoustics somewhat. As I mentioned earlier, treatment can often be disguised in a room, so it isn't too noticeable, or it can be made portable and moved out for storage when the room is not being used as a home theater.

There are a handful of things that EQ can help with, when applied correctly, even in a poorly treated room, but EQ cannot fix most of the issues, and the results of trying will likely not make you happy. Especially if you are wanting to hear quality sound in your room, similar to what a large movie house sounds like. The real solution to achieve that, is acoustic treatment plus EQ at the end.

But first comes the analysis! As soon as you figure out the problem with your REW setup, do a room measurement with REW, and post the results here. We can show you what the problems are in your room, and identify which ones can be improved with EQ, and which ones require treatment.


- Stuart -



amurguia
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How To Calibrate and Use REW To Test and Tune Your Room Acoustics

#7

Postby amurguia » Thu, 2020-Aug-06, 01:39

Perfect!

I appreciate the long answer. The information is fantastic. I may be able to room treat over time, we'll see how those conversations go :)

Is there a good place to go for room treatment stuff? I can also Google.

I’ll troubleshoot that sound card, thanks for the sample. That helps a lot!



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How To Calibrate and Use REW To Test and Tune Your Room Acoustics

#8

Postby Soundman2020 » Thu, 2020-Aug-06, 02:04

Is there a good place to go for room treatment stuff? I can also Google.
Right here, on the forum! :) We don't sell treatment, but we can certainly show you how to make your own. Or w can suggest things that you can buy, if you don't want to make stuff.

But first you have to figure out WHAT treatment you will need, and WHERE to put it in the room... that's what REW will help you do!

If you look around the forum, you'll find lots of useful advice, and also lots of examples of the how people are treating their rooms. They are mostly people building home recording studios, not so much home theaters, but the same basic principles apply. There's also a section on things to ignore! Things to look out for, and avoid. There's a lot of scammers out there, ready to take your money and sell you useless "acoustic" products, and there's a lot of well-meaning but very wrong or misleading advice too. So I created a section in the forum where you can earn about those things. I call it "Fake Acoustics": Myths, legends, mysteries, and scams (you can click on that link to go there directly). That would be a good place to start.

There's also a section with Useful reference documents for designing and building a studio or home theater, where you can find stacks of technical information about acoustics. And there's a Reference area with articles about some specific aspects of building and treating rooms, and a Recomended reading list of books that we recommend, if you really want to get a good understanding of how sound works, and how to build or treat a room for good acoustics. And finally, there's a series of articles I'm working on right now (just getting started!) that show you how to go about INTRODUCTION TO DESIGNING YOUR OWN STUDIO OR HOME THEATER , step by step, through the entire process. That's not finished yet: just the first couple of steps. But I'm adding to it every few days, so do check back regularly!

Basically, everything you need to know is right here on the forum! :thu:

- Stuart -



amurguia
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How To Calibrate and Use REW To Test and Tune Your Room Acoustics

#9

Postby amurguia » Thu, 2020-Aug-06, 10:37

Excellent. Thank you so much for all the info. I appreciate it.



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How To Calibrate and Use REW To Test and Tune Your Room Acoustics

#10

Postby Starlight » Thu, 2020-Aug-06, 11:13

amurguia wrote:Source of the postIs there a good place to go for room treatment stuff?
Stuart mentioned building your own. That is something I did a few years ago for about 20% of the cost of buying ready-made traps, so well worth it. If you have the money and lack the interest to make your own, GIK Acoustics is a well-enough respected company that makes and sells traps and more.

Here are a few photos from when made my traps to show you how simple they are. They are covered with hessian (UK) which is burlap (US).
2378pasca.jpg

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2383pascy.jpg

2405cloud.jpg

2635studio.jpg




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