TOPIC: Dirac with external mic and intermodulation

Hi
Don't know is this the right place, or should this be in SHD topic, but I have this problem:

When I'm trying to calibrate Dirac thru SHD, and I'm selecting my SPL DAC as mic preamp, and when im running the sweep tones,
it generates several intermodulation chirping to output, like Im having wrong sample rate or such.
I have tried every sample rates, and bit depths on my computer settings, but nothing helps.

And this is only when I try to calibrate Dirac. When running sweeps thru my DAW, there is no issues and SHD switches nicely to any given sample rates.

Only thing I can image, is that you can't calibrate Dirac with SHD without UMIK microphone?!?
If so why it lets you choose on witch devise you want to record your mic?

I have load latest firmwares, and softwares and im using 2020 iMac

Any ideas?

I believe you have to use a UMIK-1. See the red 'Note' in the 'What's in the box?' section of the following link:

www.minidsp.com/products/streaming-hd-series/shd

You could contact Support to double-check there isn't any way around this.

Damn, you are right!
I have read all the manuals many time to find, if i find this kind of infomation. And there it is.
Thank you!

Hi
So I got UMIK-1 mic today and did some more studies around the issue, but it just remained the same.
Measurement signal just gets corrupted by intermodulation distortion, when I try to calibrate with Dirac.

Thats very weird, since its definedely that Dirac app, that's making it. When I'm running normal audio tests thru the SHD output signal is just fine.
Here is recording from Dirac dump folder, where you can hear that direct mic recording, when trying to calibrate.

Edit: ok so you can't attach wav files.

You'll likely get this resolved quickest if you contact Support via the link at the top of the page. If you want anyone to try to help further here it would be helpful if you you could give full details of exactly what equipment you have and how it is all connected up.

I send a customer ticket. Now we'll wait.

Some details to my setup: Im running mastering studio, and my main computer is iMac 2020, and I just today updated my OS X from Catalina to Big Sur. With both of them, the problem remains the same.

I have disconnected everything, but SHD from my system, to avoid any conflicts. I have tried to install all of the latest firmware, and newest mini DSP and Dirac softwares, and even tried older versions.

Tried every sample rates and all that, but nothing helps.

Im very confused now. Surely that calibration sweep should not have that intermodulation "chirping" at upper frequencies? That would be very strange.

Do you get a sensible looking measurement in Dirac? It just occurred to me that you may be describing something normal...

Hi!

Actually i did got reasonable sounding correction curves.
I havent made final conclusions about it by measuring and deep tweakin, but my first impressions were quite positive.

But that said: Is that behaviour normal? Should that signal sound like that?
And if so: How and why it behavious as it does? Never ever i have heard that measurement signal should behave this way. That intermodulation is not anyways subtle.

Im trying to implement that SHD and dirac to my mastering setup, and my main job as a mastering engineer is to eliminate about questing that what sounds, how they sound, so i might be a bit more "paranoi-ish" about this, than a regular user.

I can't remember which, but one of REW or Dirac gives a sort of audibly fluctuating high frequency 'tail' to the sweeps, which may be what you're referring to?

Ignore the correction. Does the raw measurement look sensible? Mine do which is why I've just assumed it's normal...

Ultrasonic wrote:
Thats a very good description how that sounds. So it is as it shoud be after all?!?
At the same time, this is good news, and raises so much more questions

Thank you.

Hello.
FYI: This is latest information directly from Dirac support:

"The modulation of the sweep is such that our algorithm can correct for it, so if you create a filter based on measurement data with this sweep, it should still function properly.
We've seen this issue infrequently before, and the sweep problem originates in the miniDSP hardware. In this case, we ask that you update to the latest version of the miniDSP firmware and contact their customer support in the case that the issue persists."

I have latest firmware, so its up to Mini DSP to fix this issue. (Btw, they still have not answered to my support ticket about this issue, from last week.)

Anyway, I just calibrated Dirac, with this weird calibration signal, and results are very, very positive.
Dirac performs better, than my previous Audyssey ARC.

Thank you