John Sayers' Recording Studio Design Forum Archive

Hello!

This is my first post and I am looking for advice on how to improve my room. I am an avid hobbyist and have been working on this for the last 10 years (I know a long time…)

I record mostly jazz and blues and perhaps start to rent the room out to solo artists, duos, and perhaps some voice over work.

I am able to record and mix in the room, but really suspect that it could be better.

I am not loud, can easily mix at 70 – 85 dB without disturbing anyone.
The volume in my live room is at 25.5 dB
The volume in my control room with the computer on is 34.1 dB, and if I baffle it, 31.3 dB.

Current construction is in a basement. The control room is 12’ 10” long and 11’ 2” wide. The room height is 7’6”. This gives a ration of 1.48:1.68. There is a window out to the live area that is 30” square and centered on the front wall. In addition, there are 2 soffits running the width of the room along the ceiling to hide ductwork/ beams, one along the front wall that extends 8-1/2” down from the ceiling and is 11” wide. The other one is also 8-1/2” down from the ceiling, is 25” wide and is 94” from the front wall.

The room was built with staggered stud construction and filled with fiberglass insulation. The floor is oak, and the ceiling is a Armstrong acoustic tiles with fiberglass insulation above the tiles.

The power for the outlets is on a dedicated breaker and is 2’ off of the floor. Distance from the front wall to the listening position is 38.3% of the length of the room.

The back left corner of the room has a small closet, so is cut off at an angle. There is 1 small basement casement window. The door to the studio is a steel door like to type that typically goes out from a house to a garage.

Treatment now consists of two 2’x4’ x 4” bass traps across the front corners of the room, two 2’x4’ x2” OC 703 panels on the walls at the first reflection points, another panel just like it centered on the back wall, and 2 panels of 2’x4’ OC 705, one on each door (out of the studio and to the closet).

The live area is a shared finished basement space with the family that has berber carpet, is 7’6” tall and is untreated. So far I have only recorded vocals and acoustic guitar there and have really liked the sound without anything objectionable in the recording.

I have 2 more OC 703 panels that are not being used yet.

I am posting the results along with a scale drawing of the studio and pictures.

I ran REW but am having trouble posting it. It says the file extension .mdat is not allowed?
Am I doing something wrong? I suspect actually that I am doing quite a bit wrong....

My questions are:

1. What should I do with the OC panels? Add them to the first reflection points? Back wall? Mount them on thin plywood and hang them with the plywood facing into the room for more bass trapping?
2. Should I fill behind my existing 2’x4’x4” bass traps? With what? Superchunk? Something lighter?
3. Although the budget is not there now, I will be able to spend money on the room. What should I plan on long term to get the room sounding as good as possible, but within some reason (i.e. if I spend $500-$1000 and can get 95% of the way to a $10,000 retrofit, I would stop at the lower figure.)

Thanks!

Hi. Please read the forum rules for posting (click here). You seem to be missing a couple of things!

That's a nice looking space, though, with good possibilities!

- Stuart -

Thank you for the reply!
I really can't believe I for got to include my location!
Sorry...
Also, is there a way I can include or send the acoustic analysis files I saved from REW?

Thanks!

Also, is there a way I can include or send the acoustic analysis files I saved from REW?

If it is too big to upload directly to the forum, then upload it to some free hosting service, such as DropBox, and post the link here.

I really can't believe I for got to include my location!

No problem! It's fixed now, which is what matters...

- Stuart -

Here is a link to the REW files:


http://www.datafilehost.com/d/4d4c57b3


Thanks!

I just took a look at the REW file, and there are a couple of issues. First, is calibration: According to that file, you did the tests with peak levels at well over 160 dB, which is roughly a thousand times louder than the tailpipe of a 747 on full take-off power, so that seems to be just a bit unlikely! The tests should by done at 85 dB, and everything should be calibrated for that. There's a procedure for calibrating REW that isn't complicated, but you do need a hand-held sound level meter to do that. If you don't already have one, they aren't expensive: You can pick one up on e-bay or Amazon for under a hundred dollars, new, and probably under 50 for a used one (just make sure you don't buy the Chinese junk ones, that sell new for 30 bucks: they are garbage).

So first you need to re-calibrate REW with a sound level meter, before you re-do the tests.

You also need to calibrate REW to your sound card, and there are instructions for doing that in the manual that comes with REW. That doesn't make a huge difference for most sound cards, but it should still be done.

The other issue is that there's only one data set in that MDAT file, and you don't say if it was from just the left speaker, just the right speaker, both at once, or something else. You should run the test three times: once for left alone, once for right alone, and one for both, without changing anything at all. IF you have a sub, then run a test for the sub alone as welll, then one more for the sub plus the mains. After each test completes, click on the name block for that test (on the left side of the REW window) and make a note of which speaker the test is for, to avoid confusion.

You also didn't say what mic you used for the tests, or where you set it up in the room, and it is very important to know that. The mic should be set up exactly where your head will be when mixing, and it should be aimed straight forwards and pointed slightly upwards at an angle of about 30°.

So please re-do the tests, then post the new data file. And after you do these new tests, it is critical that you measure the exact location of the mic in the room, so you can always get it back to the identical spot for all future tests. If you don't put it at the exact same point for eery test, the you can't compare the tests to see what changed and what still needs to be done. So measure that, and note it down carefully for future reference. You need the exact same location in all three directions, and the same orientation.

OK, that said: based on what little I can tell from this test, the room isn't too bad. There are some modal issues, yes, and there's too much absorption in the high frequencies, plus a dip in the mid range, but it isn't terrible, in terms of frequency response. The overall decay is pretty decent too, with an RT-60 time of about 280 ms and reasonably smooth spread across different frequencies. The waterfall plot is a bit strange, though: The high mids seem to be decaying slower than the low mids and highs, which is unusual. The spectrogram is pretty useless, due the incorrect calibration, so I can't say much about that!

I think it can be improved with more treatment, and I'd concentrate on improving your bass traps, to help deal with those large modal issues, and it looks like you need to do something about the highs being sucked out, as well as adding some diffuse reflections for the mids. But before deciding on any of that, you need to get the calibration issue solved, and provide the other info I mentioned (mic model, location of mic in room, individual tests for each speaker, etc.)


- Stuart -

Thank you for the help!

Yes, I tried to calibrate the card & do the test, but I wasn't really sure if I did it right. The program seemed to get upset at me at first, saying the volume was too low, but I measured it in the 79 dB region with a handheld meter. After some fiddling it told me the calibration was ok, but I was not so sure...

The test was using a Nady measurment mic (CM 100)

It was exactly at ear level in the listening position exactly between the 2 speakers. That was on purpose.

It was a led slightly upwards, prob around 30 ish degrees. That was by accident.

Measurements were with both speakers and sub, all together.

I'll try to re-do the files and post in the next few days.

Thanks!

So you measured 79 on your hand held, but did you calibrate REW so it KNOWS that was 79? That's what you need to do. Click on the "SPL Meter" icon, "calibrate", and follow the instructions...

- Stuart -

Thanks! I should have time to run the tests tomorrow!

Found myself with some time today, so here is the new REW data.

http://www.datafilehost.com/d/fc52b6fb

The first one is both speakers + Sub. Next is Left speaker, then right speaker, then sub only. They are labeled.

I hope it's better!

Thanks!

Much better! Much more coherent and consistent. For future tests, you can turn up the volume a bit, by about 10 dB. I know they say to do the tests at 70 dB in the REW documentation, but the "standard" way of doing tests (if there is such a thing!) is at 80 dB for each individual speaker, which should come up to about 86 or so for all of them together.

OK, so one that that is apparent now, very clearly, is a huge modal issue at about 128 Hz, which is likely either your 3,0,0 axial mode (predicted at 132.1 Hz), or your 2,1,1 oblique mode (predicted at 126.5 Hz). Either way, it involves your front and back walls, so you need some heavy bass trapping there. I would suggest superchunks for both rear vertical corners and both front vertical corner, floor to ceiling, and as big as you can make them, plus thick absorption on the entire rest of the rear wall (at least 4", but 6" would be better). and also 4" of absorption on the front wall, either side of the window, between the speaker and the wall.

Next, there's another huge modal dip at around 71 Hz, which is most likely your 0,0,1 mode (predicted at 75.3 Hz), involving the floor and ceiling. It's a little lower in frequency that is predicted, but I suspect that's because you measured the room height up to the false ceiling, without considering the space above that: I'm figuring there's about another 6 inches of space up there, before you get to the REAL ceiling of the room. So I'd suggest a hard-backed cloud to deal with that, as well as stuffing as much fluffy insulation as you can above that false sealing.

Not so obvious on the SPL graphs, but visible on the spectrograms is another modal issue at about 100 Hz, and that is likely to be your 0,1,0 mode (predicted at 101.2 Hz), which runs side to side, and involves your side walls. You already have some panels on your side walls, and the superchunks for the other mode will also help with this one, so I don't think you need to do any more about this one.

The IR plot also shows a sharp, loud reflection coming from something at about 3.5 ms after the direct sound, which is going to mess up your spatial perception of where sound is really coming from. That's a fairly short gap, implying a path difference or about 47 inches. It's hard to say what might be causing that, but I'm guessing it is the console surface, or maybe the ceiling. You can check it easily, if you are interested: Get a piece of string, and stretch it out from the middle of the front face of one speaker to the tip of the measurement mic. Now make it 47" longer. Tape both ends in place (one end to the speaker, the other end to a mic stand at the exact location where teh mic was), then move the "sagging middle" part of the string around to see what object it touches. There will be something somewhere that it touches perfectly, and that is your culprit. Once we know what it is, we can figure out what to do about it.

Also, something is sucking out the highs a bit too much already, so I would cover all of the above devices with plastic before you but the fabric over them, to keep the highs in the room, and do the same to your existing panels: take of the fabric, add thin plastic, then put the fabric back.

So those would be my suggestions so far!


- Stuart -

Thanks, Stuart!

I really appreciate all the help. I should have done this sooner, but I just donated to the forum.

Interesting about the real ceiling being higher than the drop ceiling. That changes my ratios!
Yes, I have fluffy fiberglass insulation up there now...

I did a test with the string as you suggested, and I think I found the culprit!

As the images show, I don't think it's the console, but rather a vent in the ceiling, over the left side of the console.
It was tough to show in the picture, but the string is just touching the plastic lever that adjusts airflow hanging down from the vent. Dang! nice job finding that!

Also, the back left corner of the room is closed off and there is a small closet there. Not sure how/ if I should treat that!


I also have a few questions:

What thickness would you recommend for the ceiling cloud, and the wall panels at the first reflection points? The current panels on the walls are 2". Would 4" be better?

I would like to use a superchunk style bass traps in the front corners, thanks!

GIK has some bass traps that are 7.5" thick and scatter panels can easily be added. They also have nice looking corner bass traps that look to me to be superchunk-style. I asked them about it, and they suggested a couple on the back wall. What are your thoughts? Their products look good and affordable, and since they have given me some advice, I want to do the right thing and purchase from them. I also want to continue to support this forum and say thank you for the most excellent and detailed advice!!

It would be great if I could just hire a full service design firm, but since any money I might make from music is a tiny, tiny fraction of what I spend on music, that's just not in the budget. I knew going into this that this endeavor is a loss financially, but a huge gain in terms of fun!

I already have plastic over all of the panels in the room. I currently have two 4" thick panels in the front corners, and a total of five 2" thick panels in other places, some 703, some 705. Should I remove the 2" thick panels and go with say the 7.5" bass traps on the backs walls, superchunk in the corners, and a ceiling cloud in addition to the first reflection point panels? I woulds then remove three 2" panels. Would that help the high end?
maybe doubling up the 2" panels and putting them on the front walls next to the windows? Would putting them under the window instead of next to the window work as well too?

What can I do about the vent? I could hang the ceiling cloud under it.

Thanks!

Erik

Interesting about the real ceiling being higher than the drop ceiling. That changes my ratios!

Yup! The acoustic boundary of the room is the hard, solid, massive, reflective surface that sound waves see. Light-weight, low density, or non-massive things in front of that aren't taken into account, since low frequency waves ignore them, and go straight through.

As the images show, I don't think it's the console, but rather a vent in the ceiling, over the left side of the console. It was tough to show in the picture, but the string is just touching the plastic lever that adjusts airflow hanging down from the vent. Dang! nice job finding that!

Sounds like it could be the culprit! To check, maybe you can figure a way of positioning a piece of thick piece of insulation over that vent and repeating the test? Perhaps take out the register itself and stuff the end of the duct with insulation? Obviously, you can't just hold something up there, since your body itself would greatly change the acoustics, invalidating the test, but if you can figure out something temporary and do another REW test (just one test, with all speakers on), then that would confirm if it is the issue or not.

Also, the back left corner of the room is closed off and there is a small closet there. Not sure how/ if I should treat that!

Take it out? Just kidding: you could try covering the front (including the door) with absorption.

What thickness would you recommend for the ceiling cloud,

I would make it a hard-backed cloud with at least 4" of 703 below, and another 2" or 4" above. The hard back needs to be fairly heavy and solid, so maybe 3/4" MDF would be good for that. I would also hang it from chains for safety, using fully closed hooks (not "S" hooks), and angle it at about 10° (lower over the speakers, higher over your head). Use good quality chains, anchored firmly and safely: Check the manufacturer's rating and use more than you need. EG, if four chains would be enough to hold that weight, then use six or eight. You do NOT want that thing coming down on your head!

and the wall panels at the first reflection points? The current panels on the walls are 2". Would 4" be better?

Definitely! And if you can space them away from the wall another inch or two, that will help even more. The air gap increases the effective depth, which makes them effective down to lower frequencies.

GIK has some bass traps that are 7.5" thick and scatter panels can easily be added. They also have nice looking corner bass traps that look to me to be superchunk-style. I asked them about it, and they suggested a couple on the back wall. What are your thoughts? Their products look good and affordable, and since they have given me some advice, I want to do the right thing and purchase from them. I also want to continue to support this forum and say thank you for the most excellent and detailed advice!!

GIK has some good products, and Glenn Kuras is one of the good guys in the industry. He's also a forum member (although I haven't seen him posting much lately, unfortunately!) So yeah, he's very likely giving you good advice on which of his products would work best for you.

any money I might make from music is a tiny, tiny fraction of what I spend on music,

Well, you know what they say about the music industry: The best way to end up with a small fortune in this business, is to start out with a LARGE fortune....

I knew going into this that this endeavor is a loss financially, but a huge gain in terms of fun!

Oh yeah!!! For sure.

I already have plastic over all of the panels in the room.

How thick is that plastic? It might need to be thicker, since there's definitely an overall roll-off of the high end. Is your floor carpeted? What speakers are those? NS-10s?

Should I remove the 2" thick panels and go with say the 7.5" bass traps on the backs walls, superchunk in the corners, and a ceiling cloud in addition to the first reflection point panels?

Sounds like a plan.

I woulds then remove three 2" panels. Would that help the high end?

You could re-use those panels up front, between the speakers and the front wall.

And actually, that would very likely make the low end worse, not better, since you'd be increasing absorption across the board (lows, mids, and highs)- But wrapping in plastic helps. another option is to put them in frames and put random wood slats across the front too, widely spaced, to increase diffusion and reflection. Or maybe add some large non-numeric diffusion, such as pyramids or cylindrical in a couple of places.

maybe doubling up the 2" panels and putting them on the front walls next to the windows?

Would putting them under the window instead of next to the window work as well too?

Not really: they need to be between the speakers and the front wall, to help deal with the combing filtering and other reflection artifacts bouncing off there.

What can I do about the vent? I could hang the ceiling cloud under it.

- Stuart -

Thanks!!

Some answers to your questions:

Some of the plastic is 4 ml. Some are just thin garbage bags...
How thick should the plastic be?

The speakers are blue sky Prodesks.

The floor is wood.

When you said "it might make the low end worse", was that in reference to removing the panels or in reference to putting them on the front wall? I think it was in reference to removing them, but I just want to be sure that I understand!

I can do a hard backed ceiling cloud, and was thinking of 4". It kinda has to hand down from the ceiling a bit to clear the vent, so I'm not sure there is much room for insulation above the hard surface. With the speaker end lower, that would put it just under 7' off the floor. How low is too low?
Is there any such thing as too low?

Yup, music is a good way to get rid of any of that pesky money laying around!

As I play jazz, what's the definition of a jazz musician?

Someone who puts a $5,000 instrument into a $500 car and drives 50 miles for a $5 gig.

Thanks for the help!!

Erik

Some of the plastic is 4 ml. Some are just thin garbage bags... How thick should the plastic be?

I would use 1 or 2 mil on the cloud and first reflection points, 4 mil on the back, and 6 mil everywhere else.

The speakers are blue sky Prodesks

Nice. OK, so the response should be flatter than what is visible in your REW data, but hopefully that will smooth out a bit with the treatment.

When you said "it might make the low end worse", was that in reference to removing the panels or in reference to putting them on the front wall?

In reference to all the changes I mentioned: That's a lot of absorption you'll be adding, and it will suck out the highs more than the lows. The plastic helps to keep the highs in the room.

It kinda has to hand down from the ceiling a bit to clear the vent, so I'm not sure there is much room for insulation above the hard surface.

If there isn't room for that, then that's OK. It would be nice to have the extra absorption up there, but if you can't fit it in comfortably, then that's OK.

With the speaker end lower, that would put it just under 7' off the floor. Is there any such thing as too low?

Yup! The point where you bang your head on it, is too low!! 7 feet over the speakers is not too bad: it could be worse. Some people only have their entire ceiling at under 7 feet! No room at all for a cloud like that.

Now, in your case you actually have another option: Take out the drop ceiling completely, and gain several more inches. That would probably also allow you to re-route the HVAC duct to a better place, hopefully.

Someone who puts a $5,000 instrument into a $500 car and drives 50 miles for a $5 gig.

Yup. I sometimes feel like that when I run live sound for an event....

- Stuart -