John Sayers' Recording Studio Design Forum Archive

Greetings to everyone it's been a long time since my last post. 5 years ago I moved into a small office space and managed to cramp in a (2.72m x 3.78m x 2.53m height) room. I know it's pretty small but it's what I could afford at the moment. I had to get work done for I already had some bands booked. So I had to make "temporal" acoustic treatment with the plan to improve it later on. Sound isolation is not an issue for I mostly mix in this room, and there aren't any residential neighbors.
What I managed to implement as acoustic treatment was an over all inside out wall design, but because of the small space I could not afford to go with 4" 703 only 2". I have two semi rigid clouds which are 3 " 703 and cover the whole ceiling but the area above the couch. I bought OC 703 in excess to further treat the room in the future so I have plenty left in the storage. My speakers are Adam A7x, because of the small room I figured a bigger woofer would be too much.
Now i'm finally planing on improving the acoustics in this room. And finally managed to make the measurements. My speakers are standing on sand filled stands. I originally planned on going the whole way and building a soffit mount and if it's not far fetched enough I still would like to do it (there are some modular designs which seemed doable.) My desk is way to big for the space and want to change it. Perhaps some of the issues could be because of this. On the back of the room is a couch, my floor is laminate flooring.
I hope this is enough information together with the pictures attached.
Now about the REW files. I don't really know how to interpret them and how good they can get in a space like mine. I know my speakers start at 48 hz therefore I didn't expect much sub information.
I noticed though that in the measurement with both speakers on, there is a big dip around 14 k ( looks like it canceled out between the speakers) I don't really know how to address any of this issues. And would be really greatfull if you could help me. My walls are all naked, like a blank OC 703 canvas.
Thanks in advance!

Here is the mdat file:

https://www.dropbox.com/s/j9xcogq6mjkju ... .mdat?dl=0

Welcome back!!!

It sure has been a while, and I do remember your brief thread.

Here is the mdat file:

Are you sure you followed the complete REW calibration procedure, including setting the SPL levels using a hand held sound level meter? It does not look like it from your data.

You need to set the levels such that each speaker by itself is putting out 80 dBC when using REWs pink noise generator, and therefore both together will automatically give you 86 dBC. The levels I see in your file are more like 60 dBC. There's too much noise in that file to see what is really happening in the low end. Please re-calibrate REW completely, using a good quality hand-held meter, set to "C" and "Slow", then repeat the same tests you did already. You can start the sweep at 18 Hz, in your case. No need to start it at 10.

My speakers are standing on sand filled stands.

I originally planned on going the whole way and building a soffit mount and if it's not far fetched enough I still would like to do it

It is certainly possible! And recommendable. The only issue with soffit mounting A7X is the strange angle at the top of the cabinet... difficult to cut. But some of my customers have successfully done that. One even cast his soffit baffles in concrete! They worked great...

My desk is way to big for the space and want to change it.

Get something that is not just smaller, but also more open, with fewer surfaces on it. Rounded legs, no drawers, no sides, smaller top surface. Even consider tilting the top surface slightly. The idea desk would probably be something made from wire mesh... it would look ugly, but would be great, acoustically!

Perhaps some of the issues could be because of this.

Very probable, yes. If you have a chance, take out the desk and do anther REW test without it... I think you'll be surprised at hoe much difference it makes!

I noticed though that in the measurement with both speakers on, there is a big dip around 14 k

That's not a problem. In fact, it isn't really there! Or rather, you will never hear that. You had the mic set up correctly in the middle of where your head will be, which is good, but in reality your ears are a few cm off to each side, so they will not "see" that dip where the two waves meet and suffer cancellation / summing. Your ears and brain will hear the two different signals, and will interpret them as a stereo image, not as what you see in the graph.

Don't worry to much about the high end: focus in the low end first: Below 500 Hz in general, and specifically below 200 Hz. That's where all your big problems will be.

I noticed that you also have some acoustic guitars in the room: you should take those out fr the testing. They are resonant things that ring and sing! And you don't want them messing up your readings, by ringing and singing along with the test signal....

So take out the guitars, re-calibrate for 80/86 dBC, and re-test. If you want to take out the desk and do another test like that as well (in addition to the tests with it in place), that would be good, but if it's too much hassle to do at present, that's fine.


- Stuart -

Thanks for the fast reply!
I did calibrate but with an SPL Meter App (hehe) tomorrow I shall get an appropriate SPL meter and run the tests again!
Thank you for the warm welcoming back I remember spending hours and hours lurking around the forum.
Well then I'll post tomorrow the new measurements! I'll try to remove the desk and guitar too.

Greetings!
It seems that it's pretty hard to get a SPL meter in my city. But I finally managed to find someone who sells them (luckily near my studio).
I've attached an image with the specs. Would this be useful to get the correct data?

Thanks!

I'm not familiar with the brand, but it's the right type of meter and the specifications are fine. It should be good for what you need.

- Stuart -

Greetings!
I've finally managed to get my hands on an SPL meter.
I removed the desk for the tests, and made another set of tests without the couch on the back of the room.
Hopefully I've calibrated the REW appropriately.

Please help me interpreting these measurements and suggesting possible solutions.

Thanks in advance.

REW FILE:
https://www.dropbox.com/s/ye4g8nvjxt3m2 ... .mdat?dl=0

Anyone?
I'm eager in fixing my room now that there are holidays coming soon.
Thanks

Great! It looks like you calibrated REW correctly now.

However, you have an electrical problem in your studio somewhere, it appears:
See that sharp peak at 120 Hz? It never dies away, and stays at a constant level. I'm guessing that is mains hum. It's the second harmonic of 60 Hz. There's also a secondary peak at 180 Hz, which would be the third harmonic. I'm not sure if you are on 50 Hz power or 60 Hz power, but that's a classic indicator of 60 Hz electrical induction somewhere. Perhaps faulty grounding. You'll need to fix that, as it is messing up the readings. It is all of the measurements you did, for all speaker combinations, with and without the couch. If it is not mains hum, then it might be a small fan, or maybe a laptop power supply, or something like that.

But anyway: Overall, the room seems to dry in the high end, and not enough bass trapping. The decay times over the complete mid range and high end are around 70 ms, which is very low. The room must sound rather dead, and be a bit unpleasant to work in for long periods of time. It's only below about 300 Hz where the decay times increase, and then they go too high, up to around 400 ms. For that room, you should aim for something around 180 ms or so, and consistent across the entire spectrum. It seems to me that your walls must be very absorptive, and you'll need to do something to make them more reflective.

Also, there's a lot of low frequency noise getting in to the room. Are you close to something noisy, such as a road, or heavy machinery, or something?

The modal behavior is not where I would expect it to be for a room with the dimensions you gave. Are you SURE those are accurate? Did you measure those to the hard, solid, rigid, massive boundaries of the room?

So in general what the room needs is more bass trapping, and less absorption (or more reflections) in the mids and highs. There's a couple of other issues too, but those are the big ones to deal with first.


- Stuart -

Thanks for the Input!
That peak your talking about could be my PC that's nearby and not THAT quiet. And yes there is a a Road nearby. But it's not actually perceptible once you'r inside the room.
And yes the dimensions I gave are from hard surface to hard surface. How come it doesn't seem like this dimensions? What should be differently?
Well You actually described my room perfectly pretty damn unnaturally dry. And with some mayor bass build up. Now the Question is. How should I treat it? Shoud I create a new topic or continue this one?
You've pointed out two mayor issues to dry sounding in the high and mids and to little bass trapping. (ignoring the electrical noise because there is not really much I can do about it)
As I mentioned before all my walls are 2" inch thick 703. I was thinking about soffit mounting my speakers because the inside hanger traps could act as some initial bass trapping. And the hardwood surface would bring some "liveness" to the room.
In addition I was planning in adding some slanted slot resonators on my first reflection points filling these equally with hanger traps, serving again the purpose of controlling the lows and adding some "liveness" to the room.
Where should I start?
Remember isolation is not an issue.

Thanks in advance

EDIT: I've just make some tests and noticed that my behringer ECM 8000 mic, is EXTREMLY Noisy even at low levels, theres an weird electrical high pitched noise and some really low rumble. I tested with my other condenser mics and even if i crank my gain on the RME UFX the noise floor isn't even near as with the Behringer. I can't afford a new mic right now. I'm kinda pissed.

EDIT: I've just make some tests and noticed that my behringer ECM 8000 mic, is EXTREMLY Noisy even at low levels,

You are not the first person to have that problem! I have heard of several other people, including ME! I have an ECM 8000 that is basically unusable, for this very same reason. I also have a PreSonus PRM1, which is excellent, and a couple of others.

So, as of today, I will no longer recommend the ECM-8000. In fact, I will tell people that it is NOT a suitable acoustic measurement mic, and to avoid buying it. Spread the word. Behringer does make some good stuff, but mics and speakers are not among them... Especially not the ECM8000.

I would suggest that you try to return yours to the place you got it, for a full refund, or replacement.


- Stuart -