Acoustic Treatment Design based on REW Measurements

I am not one to give technical advice, but I have used and still use 4" thick panels for every reflection point in the past. Now I have a different setup with whole ceiling treated above my mixing desk with bass traps in corners.


Ceiling is now a completely treated space with cloth covering.

After the ceiling acoustic treatment, I have not actually found a need to add first reflection point treatment with monitor upgrade.
 
Troubleshooting: Repeatability of Measurements

So I am confused now...

I bought the panels from Acoustimac that I was talking about on here a month ago. I set them around the room and took a quick measurement with REW and some things looked worse, so I took them back out to see if they were causing the problem.

As it turns out, even when I attempt to set the room back exactly how I had it in my measurements a month ago I can't reproduce those measurements... it's really frustrating. Today's measurements are highly repeatable--I have run them more than a dozen times (moving things around in the room, tweaking settings, calibration files, etc)! But they don't match what I was getting a month ago, and I can't figure out why...

Look at this one (1/24th smoothing). From 100 to 200Hz. The blue line is a month ago, the pink (or whatever color that is) is today. There is a really bad notch around 105Hz and a really bad peak around 130Hz that weren't there before. Where did they come from?!?!
Reproducibility Problems_Same room 4 weeks apart.jpg

This image also includes the untreated room (measured over a year ago). You can see that the 105Hz notch and the 130Hz peak were there then. How did I have them fixed a month ago, but not today?
Reproducibility Problems_Untreated vs. Same room 4 weeks apart.jpg

Also, we can clearly see that in either measurement, my homemade bass traps did a great job from about 60-90Hz...

Does anyone have any ideas for me at all?
 
AHA!!! I can manipulate the 130Hz peak by changing the front-to-back position of my 32" LCD monitor!!! It was set deep into the cabinet today, but pulled out much farther a month ago.

Now I just have to figure out the 105Hz notch....
 
AHA!!! I figured out the 105Hz notch! The cabinet UNDER my LCD monitor. Apparently I had the cabinet doors open 4 weeks ago and closed earlier today. I can now get my measurements to be a lot more reproducible.

That is really really interesting to me. I hardly have any treatment on my front wall (behind the LCD monitor or studio monitors), other than the three non-floor corners. This is the unfortunate result of the desk unit that I am using, and there isn't much I can do about it, other than paying attention to whether or not doors are open or closed.

The amroc room mode calculator helped a lot in the troubleshooting. I could see that there was a 107Hz node right down the centerline of my room, so I started paying attention to things in the center.
 
Troubleshooting: Repeatability of Measurements SOLVED

That was a really informative (though time consuming process). Here's the REW graphs to back up my findings.

So this is what I was dealing with: no changes to room treatment from a month ago to today, yet significant changes to SPL response.
Reproducibility Problems_Same room 4 weeks apart Take 2.jpg

Moved the LCD monitor, closed some cabinet doors, and today's results matched a month ago's much better. NOTE: No change to treatment! Solved 105Hz notch, 130Hz peak, and a notch around 340Hz that I hadn't been paying attention to at all...
Reproducibility Problems_Same room 4 weeks apart Solved.jpg

Here's the full history, showing the untreated room, and the above iterations.
Reproducibility Problems_Same room 4 weeks apart Solved Full History.jpg

IMPORTANT LESSON LEARNED: Some room variables that actually do vary from one day to the next can have a significant effect!

Now I wonder if I could figure out what has amplified the 270Hz peak that was much lower before any room treatment...

And now I can test out my Acoustimac panels...
 
that's a great post... cabinet doors open and the like. sound is so crazy, amazing how small changes can push some freq up or down.
 
I think the biggest issue is the size of the room to begin with. It is not ideal and not able to have perfection...

I give you huge props for working so hard at getting the best from treatment in your room, but you have to realize it is not going to be perfect in that space.

I wonder sometimes when people analyze to such a degree, when in the end it really comes down to learning what monitors tell you in mix stage. It may take more time to get things right, but no room treatment is going to make your mixes perfect. That just takes time and a trained ear.

Granted, I am lucky to have a larger room where I mix, but even my modes are fucked and REW tells me way different things at different listening positions.

The fact that I see you looking at graphs and not listening to the room makes me wonder. Kind of like guys that look at real time analyzers while mixing. It not what it looks like that is important, it is what you 'hear' and how it sounds/translates to other systems and environments.

Room treatment is always the best investment for making this easier, but not possible to make a room perfect. Not even the best built/sized rooms are perfect. It is a matter of damage control to help you get close.

You cannot rely on room measurements to decide what your mixes sound like. Just work with what you obviously have done to the room to make it better, and work with the space by working in it.


:)
 
I get what you are saying, [MENTION=112380]jimmys69[/MENTION].

Unfortunately, I don't have a lot of experience doing this and a trained ear to work with... I'm pretty much a noob to this.

What I do have is an electrical engineering degree (only barely relevant--just means I have a concept of frequencies and some of the math around them), and a high tolerance for research, looking at graphs, taking measurements, and experimenting. I hate spending money without justification, so I wanted to be able to document "before and after" of all the time and money I was investing in treatment. My treatment approach has been pretty much "by-the-book" (but not so much "buy-the-catalog"), so the measurements are just to help me convince myself that the book was right, and it was worth the investment.

I had some bad experiences back in college with mixing decisions made in a tiny un-treated dorm room. After that I decided that if I was ever going to attempt again to actually record music I would put the effort into fixing a room as best as I could.

I know it will never be perfect, and I think I have about hit the point of diminishing returns, but my tests today with the Acoustimac panels in temporary position have me down to about ±8db across the spectrum. That's pretty good, right? I'll post those details once they are permanently mounted.

If you have any tips on training my ear, I will gladly take them. I have enjoyed playing with the amroc room mode calculator--selecting frequencies it has identified as problematic, and then walking around the room listening for them. I also discovered by ear that a ground loop isolator I was using on a laptop was killing my highs (makes sense from an electrical engineering perspective). Other than that, all I have is an intention to pay good attention to various sound systems in various environments.

I am eager to get past this point and start working on actual mixes so that I can develop that trained ear! Then I'll be posting mixing questions in the other parts of this forum!
 
I get what you are saying, [MENTION=112380]jimmys69[/MENTION].

Unfortunately, I don't have a lot of experience doing this and a trained ear to work with... I'm pretty much a noob to this.

What I do have is an electrical engineering degree (only barely relevant--just means I have a concept of frequencies and some of the math around them), and a high tolerance for research, looking at graphs, taking measurements, and experimenting. I hate spending money without justification, so I wanted to be able to document "before and after" of all the time and money I was investing in treatment. My treatment approach has been pretty much "by-the-book" (but not so much "buy-the-catalog"), so the measurements are just to help me convince myself that the book was right, and it was worth the investment.

I had some bad experiences back in college with mixing decisions made in a tiny un-treated dorm room. After that I decided that if I was ever going to attempt again to actually record music I would put the effort into fixing a room as best as I could.

I know it will never be perfect, and I think I have about hit the point of diminishing returns, but my tests today with the Acoustimac panels in temporary position have me down to about ±8db across the spectrum. That's pretty good, right? I'll post those details once they are permanently mounted.

If you have any tips on training my ear, I will gladly take them. I have enjoyed playing with the amroc room mode calculator--selecting frequencies it has identified as problematic, and then walking around the room listening for them. I also discovered by ear that a ground loop isolator I was using on a laptop was killing my highs (makes sense from an electrical engineering perspective). Other than that, all I have is an intention to pay good attention to various sound systems in various environments.

I am eager to get past this point and start working on actual mixes so that I can develop that trained ear! Then I'll be posting mixing questions in the other parts of this forum!


Man, I so feel where you are coming from. But you have to realize first that there is no perfect environment. One just needs to learn by doing, no matter how good or bad the room sounds.

Just record in that room you have worked on, and forget about specs and anything involving theory. Just record and learn by doing from this point. Don't rely on what factors are involved. You already tamed the room. Just record and make adjustments from where you are now.

Just my 2 cents... :)
 
Back
Top