Podcast HomeTheaterUnited Podcast Episode 15 - Dave Upton on room correction and calibration with REW and Audyssey (1 Viewer)

[Sam Posten]

 

[John Dirk]

Thanks as always, guys. This will give me something to listen to while I'm supposed to be working tomorrow!

 

[JohnRice]

I meant to ask Dave if he lost power. A week?

 

[Brian Dobbs]

 

[Sam Posten]

I meant to ask Dave if he lost power. A week?

4 days I think he said

 

[JohnRice]

Thanks for the podcast guys, and thanks @Dave Upton for the info. I definitely want to delve into REW, but I don't have a notebook computer. Fortunately, I am tempted by the new M1 MacBook Air. do you have specific recommendations of a reasonable microphone?

So, are you saying that the Sonex that I have in my HT for first reflections don't actually do much good? Or were you saying more that they're not effective with sub frequencies? Is that approach simply not effective for general deadening of the room, as opposed to for bass traps?

 

[Dave Upton]

Thanks for the podcast guys, and thanks @Dave Upton for the info. I definitely want to delve into REW, but I don't have a notebook computer. Fortunately, I am tempted by the new M1 MacBook Air. do you have specific recommendations of a reasonable microphone?

So, are you saying that the Sonex that I have in my HT for first reflections don't actually do much good? Or were you saying more that they're not effective with sub frequencies? Is that approach simply not effective for general deadening of the room, as opposed to for bass traps?

The egg crate type foams are just not as effective as other products. If you look at test results, you’ll see they’re most effective in the 3-400Hz range and up. They’ll do next to nothing for bass.

Bass traps generally have to be at least 4” thick, ideally 6 or more .

Here are some examples. Here’s your egg crate type foam:

Now for comparison here is a standard 2 inch panel from gik acoustics:

Now compare these to a corner bass trap:

And a monster bass trap in panel form:

As the data shows, the egg crate is better than nothing, but it’s effectively useless for treating the most problematic and important frequency range in most rooms.

I am not advocating for treating only the bass frequency range, but the panels that do effectively treat bass will also have a positive impact on the mid range and high frequency problems in your room.

Now that panels are on the market with what they call flex range technology, you can get all the benefits of a bass trap with some Diffusion, ultimately preventing your stereo image from collapsing.

I have a combination of monster bass traps, corner bass traps and wall panels in my room, in addition to a couple of specialized MSR acoustics spring traps narrowly targeting the 60 Hz region which is problematic in my room.

 

[Dave Upton]

I referenced a few different resources in the show. Here they are:

Show notes:
Youtube videos showing room setup, REW, calibration: https://www.youtube.com/channel/UCwxr5jJUgORcMS9FmIaH1jQ/videos?view=0&sort=da&flow=grid

Cheap acoustic panels: https://www.acoustimac.com/acoustic-panels

Measurement microphone for REW: https://www.minidsp.com/products/acoustic-measurement/umik-1

Audyssey Guides: https://www.avsforum.com/threads/official-audyssey-thread-part-ii.2376770/#post-52664721

Audyssey MultEQ FAQ and Setup Guide

www.hometheatershack.com

 

[JohnRice]

The egg crate type foams are just not as effective as other products. If you look at test results, you’ll see they’re most effective in the 3-400Hz range and up. They’ll do next to nothing for bass.

Bass traps generally have to be at least 4” thick, ideally 6 or more .

Here are some examples. Here’s your egg crate type foam:
View attachment 90698

Now for comparison here is a standard 2 inch panel from gik acoustics:

View attachment 90699

Now compare these to a corner bass trap:

View attachment 90700

And a monster bass trap in panel form:

View attachment 90701

As the data shows, the egg crate is better than nothing, but it’s effectively useless for treating the most problematic and important frequency range in most rooms.

I am not advocating for treating only the bass frequency range, but the panels that do effectively treat bass will also have a positive impact on the mid range and high frequency problems in your room.

Now that panels are on the market with what they call flex range technology, you can get all the benefits of a bass trap with some Diffusion, ultimately preventing your stereo image from collapsing.

I have a combination of monster bass traps, corner bass traps and wall panels in my room, in addition to a couple of specialized MSR acoustics spring traps narrowly targeting the 60 Hz region which is problematic in my room.

Just thinking of economy. For treating first reflections and general brightness, isn't the foam going to be effective? That's really in frequencies over 400Hz, isn't it? I also want to explore bass improvements, but in my room it's more the brightness I want to tame. I definitely want to analyze any bass problems, but I seem to have been able to mostly alleviate them with placement.

 

[Dave Upton]

Just thinking of economy. For treating first reflections and general brightness, isn't the foam going to be effective? That's really in frequencies over 400Hz, isn't it? I also want to explore bass improvements, but in my room it's more the brightness I want to tame. I definitely want to analyze any bass problems, but I seem to have been able to mostly alleviate them with placement.

Generally speaking, perceived brightness is not only the result of an acoustic problem. It is a problem that starts with the way your system is put together and the actual components of said system, followed by the placement of your speakers and listening position, and finally amplified or tamed by acoustic treatments or the lack thereof.

In systems that I have calibrated, it is caused by bright speakers most often, followed by source and amplifier components that have high frequency issues, in the form of noise or distortion causing sibilance. Sometimes this is caused by the room, but that’s usually only in the case of extensive glass or extremely hard reflective surfaces that amplify high frequencies to the extent that they are problematic with any gear.

There is a reason that almost all room calibration systems have a high frequency roll off, it is to combat this exact problem.

An untreated room will certainly magnify these problems, but even an untreated room should not sound too bright with the right placement and equipment selections. My experience has been that bright speakers will sound extremely bright in an untreated room, and approach Neutral as you add more treatments. There’s nothing wrong with that, but to me it is secondary to the other benefits the treatment provide.

The primary reason you treat the mid range frequencies and higher frequencies is to lower the RT 60 in your room, with has the benefit of improving imaging, timbre and overall accuracy.

This is a great thing to do, but I still think anyone who has not experienced the results of bass trapping has no idea what they are missing. Even though you may consider the bass your system produces fairly tight, it is likely fat and bloated compared to what it could be with good room treatment. As I added more treatments to my room, I had to continually redefine my expectations of what tight accurate bass was.

In terms of economical treatments, the foam is definitely cheap. I just don’t know that it is cheap enough to justify the trade off. You can purchase 2 GIK 244 panels for $150, which will dramatically outperform the foam in the higher frequencies and has the added benefit of actually making meaningful improvements on the bottom end. Quibbling over under $100 in price difference in treatments is probably a poor reason to accept lower performance from your system, at least in my opinion

 

[JohnRice]

Generally speaking, perceived brightness is not only the result of an acoustic problem. It is a problem that starts with the way your system is put together and the actual components of said system, followed by the placement of your speakers and listening position, and finally amplified or tamed by acoustic treatments or the lack thereof.

I fully agree. This has also been a learning experience for me through the years. The biggest benefit I found with my speakers was when it was suggested they be moved away from the front wall. So, now their backs are 4' from the wall, and further from the side walls, and there are no windows. So it's really not a reflective as most rooms. Also, as I've been able to get better electronics, the supposed "brightness" of my Thiels has completely disappeared. They are now revealing and resolving, rather than bright. Now that I think about it, I can't remember the last time I thought they were harsh sounding. Honestly, this new amp (which I was extremely hesitant to buy) has made the most significant difference any single component has ever made to the system. Every other amp I've ever used with the Thiels seemed out of control by comparison. I don't know what the difference is due to. It has to be more than just power. It just feels and sounds like it is in total control of them, for the first time.

Anyway, thanks for the input Dave. After this discussion and your feedback, I do realize I am approaching this part of it as just a very last bit of fine tuning, as opposed to solving any real problems.

I look forward to exploring things more with REW, but I need to get a computer to run it on.

Did you have a microphone recommendation?

 

[Sam Posten]

I have the Umik combo which is the go to for REW noobs like me

 

[JohnRice]

I have the Umik combo which is the go to for REW noobs like me

I’ll just be waiting for an M1 MacBook Air refurb.

 

[Dave Upton]

I’ll just be waiting for an M1 MacBook Air refurb.

The good news is you can run REW on any computer - so at least it's not picky.

Regarding microphones, I generally also recommend the UMIK-1 or newer UMIK-2, but there are a few other good options like the Dayton UMM-6 or a calibrated mic from Cross Spectrum Labs.

Here's the Dayton: https://www.parts-express.com/Dayton-Audio-UMM-6-USB-Measurement-Microphone-390-808

Cross Spectrum buys mics from MiniDSP and runs a more advanced calibration on them. Worth the extra expense if you plan to buy for life:

Cross·Spectrum - Calibrated MiniDSP UMIK-1 Microphones for Sale

Purchase calibrated MiniDSP UMIK-1 measurement microphones, low-cost option for performing precise and accurate sound measurements

cross-spectrum.com

Cross Spectrum also sells my reference SPL meter, a tool that every home theater enthusiast should invest in. The Galaxy CM140 SPL meter.

Cross·Spectrum - Galaxy CM-140 Sound Level Meter

Purchase calibrated Galaxy CM-140 Sound Level Meter

www.cross-spectrum.com

 

[JohnRice]

Now I can't stop asking myself "How fat is my bass"?

Damn you Dave Upton!

 

[Sam Posten]

I’ll just be waiting for an M1 MacBook Air refurb.

They are up on Apple.com now $809

 

[JohnRice]

They are up on Apple.com now $809

I keep telling you, those are Intel models, not M1.

 

[Sam Posten]

I keep telling you, those are Intel models, not M1.

They had em. Must be gone now

 

[JohnRice]

The good news is you can run REW on any computer - so at least it's not picky.

Regarding microphones, I generally also recommend the UMIK-1 or newer UMIK-2, but there are a few other good options like the Dayton UMM-6 or a calibrated mic from Cross Spectrum Labs.

Here's the Dayton: https://www.parts-express.com/Dayton-Audio-UMM-6-USB-Measurement-Microphone-390-808

Cross Spectrum buys mics from MiniDSP and runs a more advanced calibration on them. Worth the extra expense if you plan to buy for life:

Cross·Spectrum - Calibrated MiniDSP UMIK-1 Microphones for Sale

Purchase calibrated MiniDSP UMIK-1 measurement microphones, low-cost option for performing precise and accurate sound measurements

cross-spectrum.com

Cross Spectrum also sells my reference SPL meter, a tool that every home theater enthusiast should invest in. The Galaxy CM140 SPL meter.

Cross·Spectrum - Galaxy CM-140 Sound Level Meter

Purchase calibrated Galaxy CM-140 Sound Level Meter

www.cross-spectrum.com

Thanks Dave. I ordered the Microphone and the Verified+ meter. I only have the legendary (notorious?) old analog RatShack model. I'm guessing if I want to EQ my subs, I would then use something like THIS?

I have recently upgraded four mac Minis and realize I can just set one of the old ones up with a monitor in the HT to run REW.

 

[Dave Upton]

Thanks Dave. I ordered the Microphone and the Verified+ meter. I only have the legendary (notorious?) old analog RatShack model. I'm guessing if I want to EQ my subs, I would then use something like THIS?

I have recently upgraded four mac Minis and realize I can just set one of the old ones up with a monitor in the HT to run REW.

Yeah, I use my HTPC to run REW and other calibration software.

You are correct that you'll need the MIniDSP 2x4 HD. This is the specific video guide that walks you through the process of sub EQ - it's very comprehensive: