John Sayers' Recording Studio Design Forum Archive

First off thanks everyone for all of the great info! I've been researching the forum for a few months now and have learned so much!!

So, overview... I'm in the planning process of my mixing room in my condo and I have some questions on the acoustical design..
The room is almost a perfect square regardless of the closet space, so I know I'm going to have some issues and want to aim for the best I can for under $1500 USD.
It's on a second story, with no connecting walls to neighbors. No complaints ever.

Goals: To have a true sounding room for mixing (Any recording done is direct in).

Current plans:
- Remove carpet, install laminate flooring
- Add super chunk bass traps (using Roxul)
- Add clouds above monitors
- Make cinder block speaker stands

Speaker Setup: Focal Twin 6be's

Room Dimensions:
L 10'1"
W 9'10"
H 7'11"
Closet Dimensions
L 2'5"
W 6'11"
H 7' 11"

1. I came up with a few ideas (see attached), but I'm not sure how to incorporate superchunk bass traps. Should I scratch the superchunks and follow the modular design like in the drawings John provided?

2. I originally wanted to mount my speakers, but I don't know how to compensate for the increased mid range that will be an issue with the Twin 6's. I tried looking into barefoot's DIY filter, but I have no experience in soldering and wouldn't trust myself to pull it off. Is there any other options?

3. The problem areas I see are behind the door and the entire closet. I was thinking to install the large box with insulation as seen here:
Or should do angles in the closet as seen in drawing v3?

4. I'm wondering if the slot resonators would be that beneficial for such a small room, or if I should focus on absorption. Room modes (not including closet space) for a 10'x10' room (I believe) are 56.5, 113, 169.5, 226, 282.5, 339, etc.

I have the REW software and a mic to measure the room. Not sure if it's really worth to post it until I rip the carpet out.
(My drawings may be off a little in dimensions, but mainly looking for the layout.)

Additional Questions:
Which design would work best?
What am I missing or what should I change?

Thanks for your time and Happy Holidays!

- Matt

Attached are the Sketchup Files

Hi there Matt, and welcome! (I think I might have already welcomed you in another thread, but I'm not sure if that was the same "Matt"... if so, then you are doubly welcome!)

The room is almost a perfect square

Not good...

It's on a second story,

Also not good...

Current plans:
- Remove carpet, install laminate flooring
- Add super chunk bass traps (using Roxul)
- Add clouds above monitors
- Make cinder block speaker stands

Yes, Yes, Yes, and Yes! Perfect, on all counts.

You will also need treatment at your first reflection points and on the rear wall.

Room Dimensions:
L 10'1"
W 9'10"
H 7'11"
Closet Dimensions
L 2'5"
W 6'11"
H 7' 11"

Where exactly is the closet? Is it at the back of the room? In other words, does it add 2'5" of length to the room?

Should I scratch the superchunks and follow the modular design like in the drawings John provided?

For that room, I would go with superchunks. Big ones. Deep ones. In as many corners as you can hit.

2. I originally wanted to mount my speakers, but I don't know how to compensate for the increased mid range that will be an issue with the Twin 6's.

You won't have an increase in the mid range: you will have a boost in the bass. The soffit acts something like a shelving EQ at the low end, increasing the bass level by 6 dB, starting at a frequency that is given by the size of the actual speaker boxes themselves before you mount them in the soffit. This is called the "baffle step response". Basically, the soffit eliminates the need for the internal baffle step compensation that is built into the speaker, which is why most studio monitors have "room correction" or "bass roll off" or "bass tilt" controls on the rear: It turns off the circuit that was compensating for that, since you no longer need it. The issue is that a small speaker cabinet means that all of the energy in the the high frequencies radiate into half space (focused forwards), while only half of the energy in the low frequencies goes forwards: the rest "wraps around" to behind the speaker. So there is a difference of 6 dB between the high end and the low end. This is called "power imbalance" for obvious reasons, so the manufacturer artificially boosts the lows by 6 dB. But if you put the speaker in a soffit, you no longer have any power imbalance! Now ALL of the energy is going forwards. So you don't need that artificial boost any more.

I tried looking into barefoot's DIY filter, but I have no experience in soldering and wouldn't trust myself to pull it off. Is there any other options?

Your Focal 6be's have controls on the back for exactly this reason. There is a control called "Bass Contour" that allows you to cut the lows by 6 dB. That's all you need to do: turn that to -6dB, and you are done!

3. The problem areas I see are behind the door and the entire closet. I was thinking to install the large box with insulation as seen here:

That's a panel trap. It is a tuned device, set to absorb a specific frequency or range of frequencies. I don't think you'd need that. Here's what I would do:
Set up your room geometry correctly, and without any treatment at all in the room, run a test with REW. Now add the standard basic treatment devices, one by one, and do another REW test after each is in place. When you have all those in, we'll take a look at your REW data, to see what is working, what isn't, and what still needs to be be done. Then you can decide which devices you need to add, or maybe modify.

Room modes (not including closet space) for a 10'x10' room (I believe) are 56.5, 113, 169.5, 226, 282.5, 339, etc.

Not necessarily: you'd need to know the height as well, not just the length and width. Plus, your room is not 10' x 10' ...

I have the REW software and a mic to measure the room. Not sure if it's really worth to post it until I rip the carpet out.

Definitely! It wold be very interesting to see how a room changes when carpet is removed! So please do a test with the carpet still in, then another test once you have it out. Make sure the speakers and mic are in the exact same location for both of those tests, otherwise we cannot compare them validly.

Which design would work best?

Start by getting your geometry correct: First, get your speakers off that desk!!!! And get them onto stands BEHIND the desk, up against the front wall. The stands must be very solid, massive, rigid, heavy, and must place your speakers acoustic axis at 1.2m above the floor. Set the speakers so the rear edge is touching the absorption panels that you have there on the front wall, with each speaker 33" from the side wall. That means your speakers will be 52" apart. (all of this is with reference to the acoustic axis of the speaker!)

Set your chair so that your head will be 46" from the front wall. Aim the speakers so that the are both pointing at a spot about 18" behind your head.

Do your initial tests like that, take out the carpet and do another test. Then take out the treatment you already have in there, and do another test with a totally bare room. Then start putting in your new treatment, one piece at a time, with a REW test after each so you can see what it is doing.

Which design would work best?

I would go with your "green" plan for the basic treatment, but modifying it to put 6" of absorption on the rear wall, above the sofa. You could angle that: start out with 2" above the sofa, and increase it to 6" or even 8" up at the ceiling. I would also go with pure absorption on the front and side walls to start with, then only if necessary make the side ones into slot walls. With a very small room like that, I would not have tuned devices so close to your ears.

- Stuart -

Thanks for the welcome or double welcome haha!

Where exactly is the closet? Is it at the back of the room? In other words, does it add 2'5" of length to the room?

Yes, closet is in the back of the room, so the room dimensions would actually be
L 12'6"
W 9'10"
H 7'11"

I have the REW software and a mic to measure the room. Not sure if it's really worth to post it until I rip the carpet out.

Definitely! It wold be very interesting to see how a room changes when carpet is removed! So please do a test with the carpet still in, then another test once you have it out. Make sure the speakers and mic are in the exact same location for both of those tests, otherwise we cannot compare them validly.

Sounds like a good approach! I'll set my speakers up correctly and get some tests before and after removing the carpet. I'll be sure to post everything before I continue with adding insulation.

Thanks again Stuart!

Ok.. I moved the monitors to the measurements you gave me Stuart, 52" between them on center, 33" from each wall on center, 48" from the ground, pushed back against the current front panels.

These measurements are with the carpet still installed and the current (6) 48"x24"x2" Roxul Rockboard panels.

Any tips on what graph settings to use? Such as ms for the waterfall graph?

Any tips on what graph settings to use? Such as ms for the waterfall graph?

First of all, before anything else, you need to calibrate REW!

I'm absolutely certain that you do not have an ambient level in your room at -12 dB, because if you did you'd have set a new world record for the quietest room on the planet! (Actually, you'd be in second place, after the brand new multi-million dollar, ultra-silent anechoic facility that Microsoft just got certified....)

Soooo..... you'll need to get out your hand-held sound level meter, and calibrate REW to that, at 85 dB, then repeat your tests, also at 85 dB per individual speaker. So do one test with just the left speaker, then another test with just the right speaker, the a third test with both speakers.

And this time, run all your tests with a full sweep, from 15 Hz to 22 kHz.

Just use the default settings in REW for your initial viewing of the graphs.

I moved the monitors to the measurements you gave me Stuart, 52" between them on center, 33" from each wall on center, 48" from the ground, pushed back against the current front panels.

How does that sound? You should be hearing a noticeable difference...


- Stuart -

Soundman2020 wrote:

Any tips on what graph settings to use? Such as ms for the waterfall graph?

First of all, before anything else, you need to calibrate REW!

I'm absolutely certain that you do not have an ambient level in your room at -12 dB, because if you did you'd have set a new world record for the quietest room on the planet! (Actually, you'd be in second place, after the brand new multi-million dollar, ultra-silent anechoic facility that Microsoft just got certified....)

Soooo..... you'll need to get out your hand-held sound level meter, and calibrate REW to that, at 85 dB, then repeat your tests, also at 85 dB per individual speaker. So do one test with just the left speaker, then another test with just the right speaker, the a third test with both speakers.

And this time, run all your tests with a full sweep, from 15 Hz to 22 kHz.

Just use the default settings in REW for your initial viewing of the graphs.

I moved the monitors to the measurements you gave me Stuart, 52" between them on center, 33" from each wall on center, 48" from the ground, pushed back against the current front panels.

How does that sound? You should be hearing a noticeable difference...


- Stuart -

Ahh haha! Ok will do..

Sounds wayy better! I can't believe that small of a tweak changed it so much!

Ok! How about now?

I would need to see the actual MDAT file. The way you are showing your graphs is not useful.

Please upload your MDAT file to a file-sharing service such as DropBox, then post the link here so I can download it.

Sounds wayy better! I can't believe that small of a tweak changed it so much!

The math and science of Acoustics works well! Now we'll see if we can improve the response of the room, with some suitable treatment...


- Stuart -

Ok here ya go Stuart, thanks!

https://www.dropbox.com/s/049f4kzu96x7o ... .mdat?dl=0

Pulled the carpet and installed the laminate floor over the weekend..

Ok here ya go Stuart, thanks!

Ummm... there seems to be a rather big problem there! According to that file, your soundcard response is as follows:

All I can say is:

That CANNOT be right! No way. Your soundcard should have almost flat response, with maybe some slight variations in the low end and high end, just a couple of dB max. That is NOT the response of your soundcard, so you need to go back and repeat the calibration procedure for REW.

So I am ignoring the soundcard calibration files for these comments.

Next, I'm not sure what I am looking at with those tests. All of them are dated Jan 14 just a few minutes apart, Two are called "Test wCarpet" while the other is not named, and the third test was done at a different level from the other two, about 5 dB quieter, and is named Jan 13, even though it is dated Jan 14.... Two of those show huge, massive ringing at 137 Hz, but the other one shows only mild ringing there. That's hard to understand....

I'm really not sure what is going on there, but it seems that there is a problem with the way you are doing your tests.

Overall, what I can see is a lack of bass trapping in that room, very unbalanced frequency response, very unbalanced decay times, early reflections, and a few other issues. But I'm not sure if all of those are really there or not, due to the questions about REW calibration, about how the tests were done, and about what the three of them actually are.


- Stuart -

Ahh I see, I missed the portion of connecting the output directly into the input to calibrate the soundcard..

Ok! Tonight I will hopefully have a proper measurement

Thanks

Sorry I've been super busy.. but I think I finally got it.

Took me a minute to figure out that I needed to mute the input in the UAD console

So now: the carpet is out, laminate flooring is in, the window is covered with drywall (forgot to mention I was doing that), couch is in the room, same panels are up, and speakers are on cinder blocks 48" at the center.

I did 3 tests.. Left notes on each.

Please I hope this is right!

Here's the mdat : https://www.dropbox.com/s/wkx2sqrbvz9mr ... .mdat?dl=0

I hope this is right!

Unfortunately not!

1. That cannot possibly be the correct calibration: No sound car I have ever heard of has a difference of 60 dB in sensitivity between one end and the other. It would be totally unusable. There MIGHT be variations of 2 or 3 dB, but that's it.

2. There is only one single test in the file you sent, not three, and it is not labelled.

3. You did the tests at a level of around 60 dB, instead of the 85 dB that is needed.

4. You did the test from 2 Hz to 30 kHz, but there is nothing useful at all below about 18 Hz, and I doubt that your speakers and sound car are able to produce anything useful above 20 kHz.. Run your test from 25 Hz to 22 kHz only.

- Stuart -