Mix position acoutics prob...

[kats]

After measuring my mix postion frequencies I'm about +/- 3 or 4 dB across the board until 10 or 12k where there is a 8dB boost. My guess is the desk reflections and I currently only have broadband absorbtion above my mix position. does this sound like a diffuser solution or should I consider foam for the HF's?

Thanks in advance!

[Ethan Winer]

kats,

> After measuring my mix postion frequencies I'm about +/- 3 or 4 dB across the board <

Unless you have a magic mix room, your response probably varies more like 20 or even 30 dB. Especially if you have insufficient bass trapping and other acoustic treatment. How are you measuring? At 1/3 octaves? To see the true response, at bass frequencies anyway, you need to measure to a much finer resolution than 1/3 octave.

> until 10 or 12k where there is a 8dB boost. My guess is the desk reflections <

Yes, reflections from all nearby surfaces can affect that. I suggest you measure the response, then move the microphone one inch to the left, then right, and measure again at each of those places. If the frequencies change that proves the response error is position related, and not due to your loudspeakers.

As for absorption versus diffusion, it depends on the size of your room and other related factors.

--Ethan

[kats]

Unless you have a magic mix room, your response probably varies more like 20 or even 30 dB. Especially if you have insufficient bass trapping and other acoustic treatment. How are you measuring? At 1/3 octaves? To see the true response, at bass frequencies anyway, you need to measure to a much finer resolution than 1/3 octave.

Hmm not sure really. I was using the calibration tool that comes with Tannoy Precisions. Basically the software calibrates to your soundcard and sends sweeps through one of your monitors where you have a measurement mic at a predescribed position. It plots a graph for you based on this.

[Ethan Winer]

> Basically the software calibrates to your soundcard and sends sweeps through one of your monitors where you have a measurement mic at a predescribed position. It plots a graph for you based on this. <

Are you letting it do any "correction," or are you just measuring at this point?

I have to tell you that "room correction" devices are marketing hype, and you risk making things worse using them. So...

How big is your room? Where in the room are you sitting? And so forth. If you can post the graphs and maybe some photos too, that will help further. If the only treatment you have is overhead, the next step is to treat the side wall reflection points and add bass traps in the corners.

--Ethan

[Glenn Kuras]

I myself have tryed these room "correction" programs and have never had the room work any better. In fact it made things worse!!

Glenn

[kats]

Thanks for your time

Firstly, I just did the tests to "see", I didn't play with the dip switches

The room is approx 22X17X8 with the desk 1/3 - 1/2 way in between. The ceiling is plain acoustic tiles (fibre). The front wall is diffused 4'X8' centered, broadband in all corners as well as 8 4'X8' broadband absorbers around the walls and one over the mix position. The rear wall has foam HF absorbers between the broadband absorbers. The BB absorbers are Auralex (sorry - didn't know about you felllas at the time) so the efficiency won't be up to spec to your product. Floors are laminated wood (fake hardwood).

Ok the program doesn't save to file so I had to trace (I got pretty close) and upload it as a web file. So here's the graph:

graph

PS the 10k line transferred weird and should be where the HF rise begins...not ends. IE the whole graph should slide over to align properly.

[u b k]

wait, i'm unclear... is the boost at 10k something you were hearing and finding problematic, or is it something you first saw with this test and now want to correct?

there's only one thing i know that would cause such a dramatic and sudden spike in the top end, and it's something fubar in the monitoring chain. an eq that ought not to be engaged, a balanced/unbalanced cabling issue, pyschopathic monitors...

but the reason i asked the first question is because i had this notion that there is no problem, but the mic you used to measure the room is hyped up top, or you just placed it too close to a tweeter.


gregoire
del
ubk
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[Ethan Winer]

Kats,

If you have a Windows computer I suggest you download the ETF demo and run a response sweep with that:

http://www.etfacoustic.com/

Then we'll know for sure the test is accurate. Also:

Room measuring is best done with a small diaphragm omnidirectional condenser microphone. What kind of mike did you use?

One reason I suggest ETF is you should view the response at both low (1/3 octave) and high (1 Hz) resolution. Measuring is especially tricky at high frequencies.

--Ethan

[kats]

The mic I used was a measurement mic supplied by Tannoy that is specific for their calibration routine (sdc, probably omni - battery powered, cheap as borscht).

Ubik, I tested it just to see. But having said that, there is a translation problem up there that I'm used to(not a 10dB probelm though - AFAIK). It's easy to work with actually, I get a little of that HiFi sound while mixing, that eventually comes back to me after mastering the way I originally heard it in the mix. Having said that, I prefer to live in reality

I don't think there's a problem in the chain since the software calibrates itself to the soundcard - but I'll try it again through my studio converters as opposed to my PC soundcard, ya never know.

PS, just to be clear, the rise STARTS at 10k - not finishes (the graph is a bit porked)