John Sayers' Recording Studio Design Forum

Control Room - Looking for 2nd opinions
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Author:  jgoldkamp [ Tue Jul 23, 2019 1:32 pm ]
Post subject:  Control Room - Looking for 2nd opinions

I have a 12' 9" Wide by 10' 11" Long and *7'6" tall room. The asterisk that is there is a duct going through the room lengthwise that I soffetted out. It measures 46 1/2" from the right wall and drops 9 1/2" at a roughly 45° angle to 37 5/8" from the right wall.

I have the room treated with panels built out of whitewood and Roxul Safe n' Sound covered in speaker cloth, along with what I believe to be four useless GIK Gridfusors that I'm about to return. The front, behind desk, above window, front right corner, right wall, back right corner, and back ceiling, and ceiling over the listening position are all 3" thick and 16"x4', 16"x6', and 16"x8'. The other panels are 6" thick at the back left corner, right wall center, right wall top.

All of the walls are staggered double studded, insulated with an air gap. There is a studio door (2 doors actually due to the double studding) on the right wall to a hallway and another studio double door and studio window on the front wall. The doors on the right are 32" by 77.5" and the front doors are 32" x 80". The doors are made of solid wood. The studio window is 59" x 27.5"

Here is my REW measurements ad cal files. L+R+Sub and all the various combos:

REW File
Digi003 Cal file
ECM8000 Cal File

Here is a 360 photo of the room:
360 room photo

My goal is a flat frequency response for the room for mixing/mastering. If you have any advice, please let me know. I think I've gotten it as good as I can with my acoustics education, but if I'm missing something I'm always willing to learn. I'm also willing to lend my education to anyone on the forum, if asked for. I've been a sound engineer for 20 years and have an associate and bachelor degree in Sound Arts (Plus an MBA, but that's not really relevant unless you need business advice.)

Also, if there is a free way to model my room in 3D (that is not a 30 day trial) let me know. I'd love to see my reflections as my room actually is.

Author:  Soundman2020 [ Tue Jul 23, 2019 2:43 pm ]
Post subject:  Re: Control Room - Looking for 2nd opinions

Hi there "jgoldkamp", and Welcome!

I'm downloading your files to take a look, but your image is not there! When I click on that link, all I get is "This image does not exist.". So please follow the forum rules, and upload the image to the forum itself, where it will always be around for as long as the forum exists.

Also, if there is a free way to model my room in 3D (that is not a 30 day trial) let me know.
SketchUp Make 2017 ! It's free, its powerful, and way, way better than the online joke of a toy that the same company calls "SketchUp free". That one isn't even worthy of the name "toy". But SketchUp Make 2017 sure is. It was their best product ever, before they started going downhill and stopped any serious development of new features, or bug fixes. You can get it here: You could also get the 2017 Pro version, and after 30 days it will expire as Pro and turn into ordinary 2017 Make.

... OK, I looked at your MDAT file... but WOW! It's huge! It took ages to download, so I though there must be dozens of measurements in it, but there's only six. :shock: You are running your sweeps way too long; you don't need to run four 1M length sweeps, and you don't need to do them at 96 k: 44.1 or 48 is just fine, 256 k length is fine, and 2 sweeps is fine. Even 1 sweep is fine. It will make your REW files much smaller, and won't harm the results or the interpretation. Your tests will go a lot faster too. And you also don't need to run your sweeps from 2 Hz! There's no useful information in your data below about 12 Hz, so you could happily run your sweeps from 15 Hz to 22k, and you'd be fine.

Next up: your sound card calibration is invalid. It is WILDLY wrong. There's no way that your sound card is so terribly bad as this:


This is what a sound card calibration file typically looks like:

That's why your curves look so absurdly weird:

There's no way that any real room would show such results. Your calibration curve looks more like an actual measurement, similar to "L+R+SUB", which is why you got those almost flat results with some sudden peaks and dips: because your "soundcard" calibration data was basically nulling the REAL data! (I also found it just a tad hard to believe that your sub is putting out much energy at 22 kHz, as shown by the graphs... :) )

So I deleted all your soundcard calibration from the measurements, leaving just the raw data, and now we have curves that look normal:


That makes sense. That looks like the response of a typical small room.

Next up; you have some type of interference in your signal chain somewhere:

See that peak I marked at 180 Hz? That is not an acoustic issue in the room: it is an electric/electronic issue. Those peaks repeat at regular patterns all the way up the spectrum:

That could be mains hum in your cables (lousy grounding), or it could be a typicall poor quality notebook power supply (try running REW with the notebook unplugged), or it could be a faulty mic (the ECM8000 is known to be very flaky, and has a high failure rate in exactly this area, due the poor quality). OR it might be some type of lighting in your studio, or interference from elsewhere. I vote for something relating to mains hum, since the frequencies are all multiple of 60 Hz, and you live in the USA where the line frequency is 60 Hz, so that makes sense. My first suspicion would be the ECM8000, due to its lousy history. Second guess would be lighting: perhaps some type of neon lighting ballast? Third would be notebook power supply.

So, ignoring all of those major issues, what you have is typical response from a partly treated small room. There's some modal issues (see above waterfall plots), there's a hole in the frequency response around 116 Hz (probably either floor bounce or SBIR), and there's too much absorption in the mids and highs, not enough in the lows:



I marked roughly where your goal should be for decay time, around 180 ms or so. Perhaps a bit more, but it would be hard to do that in such a small room.

Overall, your results are not terribly bad, but things can certainly be improved. However, I would suggest that you first fix all the issues that I outlined above with your REW measurements. Here's a tutorial I wrote a while ago on How to calibrate and use REW to test and tune your room acoustics.

After you get your REW problems sorted out, please re-measure and post the new results, so we can have another look.

My goal is a flat frequency response for the room for mixing/mastering
That's part of a good goal, but contrary to popular belief, flat frequency response is not the best metric to set aiming for: Flat time-domain response and correct phase response are more useful and desirable goals, with flat frequency response in third place. Flat frequency response is meaningless with the context of good phase control and flat time-domain response. Which is why so-called "room correction" hardware and software are such big flops: way too many people try to use that instead of treating their rooms properly... then they wonder why the are seeing such beautifully flat graphs on the screen, yet the room still sounds like crap...! (Excuse my French). Fortunately, you didn't do that, so you can ignore my rant... :) It's meant mostly for other people who are following your thread, and might be thinking "But if only he would put so EQ on there, he could fix his frequency response!".

So, don't be aiming for flat frequency response as your first goal. Rather, aim for flat time and frequency response (use ITU BS.1116-3 as your guiding principle), and good phase response. Achieve that, and you'll have a great room.

- Stuart -

Author:  jgoldkamp [ Tue Jul 23, 2019 2:54 pm ]
Post subject:  Re: Control Room - Looking for 2nd opinions

Thank you so much for your thoughtful reply. I followed them instructions to do the sound card cal, but maybe I’ll stick to the acoustical calibration. Anyhow I will try to recalibrate again tomorrow and remeasure.

Also the 360 photo should work now. I forgot to capitalize the last “L”

Author:  jgoldkamp [ Wed Jul 24, 2019 12:26 pm ]
Post subject:  Re: Control Room - Looking for 2nd opinions

Hello @Soundman2020

I cannot get the loopback to work for the life of me. I tried for 2 hours with your instructions. I was however able to calibrate the SPL level using my CM-130 meter. I used the acoustical reference to generate these files. I am using a Digi 003 with a 256 sample buffer if anyone has a cal file for that already made.

New REW file
360 photo of the room

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