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TOPIC: Distorition problems. (and some other questions)

Distorition problems. (and some other questions) 8 months 3 weeks ago #24339

  • JONTRE
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Hello,

For the most part, I'm happy with my miniDSP DDRC-88A. But in some scenes I hear distorition. Spontaneously it feels like Dirac has EQ signal too hard and create harmonics/distorition. Is that possible?

And if so, is there anything to do to avoid something like that? For example my couch is pretty close to backwall (30cm maybe).

Accourding to the manual you should max the input sensitity on the microphone and adjust so that the background noise is below the -24dB mark. But when doing so it gives realy poor SNR? a car door slamming 200m away makes a great peak.

Wouldn´t it be better to play louder and lower the sensitivity of the microphone? :blink:

How does the bypass function work, does it bypass the filters but keeping the distance and levels correction? Can I somewhere see the result of the distances and levels calc made by Dirac?
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Distorition problems. (and some other questions) 8 months 3 weeks ago #24340

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JONTRE wrote:
Accourding to the manual you should max the input sensitity on the microphone and adjust so that the background noise is below the -24dB mark.

Um.... the manual doesn't say that (or anything like it). This is what it says, on page 25:
1. Set the Output volume slider all the way down, at -80 dB.
2. Click on the Test button for the left channel and gradually increase Output volume. You should hear pink noise playing from the left speaker. Continue to increase volume until it is at a moderate level, such that your voice would have to be raised to converse with someone sitting next to you.
3. Set the Input gain slider so that the blue bar on the level meter is about in the middle of the green section, or around -12 dB:

Could I suggest you have another look at it? You are correct that the procedure you have used is bad (very bad, actually), but it's hard to know whether that is related to your distortion problem. As a first step I would try doing a calibration the way the manual says to do it, then maybe post again with some before/after graphs?

HTH
I am not miniDSP support.

"You must ask the right questions." - Dr. Alfred Lanning's hologram.
-> Have you read the User Manual??
-> Have you drawn and posted a diagram?
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-> Have you posted your config file?
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Distorition problems. (and some other questions) 8 months 3 weeks ago #24341

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Hi John,

Actually you are right, my mistake. It was not the manual I read it, it was in the a text box on the right in Dirac Live explaining how to measure. It says that you should do as I wrote.

But then I'll arrange a calibration according miniDSP manual. However, I find it strange that is different from the text of the manual compared to that in the the program :huh:

Hope it can solve the issues for me.
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Distorition problems. (and some other questions) 8 months 3 weeks ago #24342

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That is strange... I don't have a Dirac box connected right now to check.
I am not miniDSP support.

"You must ask the right questions." - Dr. Alfred Lanning's hologram.
-> Have you read the User Manual??
-> Have you drawn and posted a diagram?
-> Have you posted a screenshot?
-> Have you posted your config file?
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Distorition problems. (and some other questions) 8 months 2 weeks ago #24357

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@ Jontre,

As correctly pointed out by John, the help file inside the Dirac Live software isn't to be followed. It's unfortunately some leftover from the "Dirac PC/Mac" (i.e. processing running on the CPU) software which indeed doesn't have similar gain structure requirements.

We'll push Dirac to remove this misinformation in the future upgrade. Thanks to both for the warning and our appologies for the confusion!
The DDRC user manual are really key here. A LOT of time was spent to explain details in more words than we could think off. Please make sure to read it inside out. You will find it very very useful. :-)

Have fun!

DevTeam
MiniDSP, building a DIY DSP community one board at a time.
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Distorition problems. (and some other questions) 8 months 2 weeks ago #24365

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I did not get the opportunity to the test last night. Hopefully I can do tonight. I´ll give you feedback when it´s done. :)

BR
Jontre
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Distorition problems. (and some other questions) 8 months 2 weeks ago #24366

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Saw one other interesting thing in the manual now. My front system is placed above my projection screen so they are not 90 degree relative to the microphone during the calibration. It´s more like a typical surround speakers is placed in height (60cm above ear level). However the manual says the microphone can point either to the floor or ceiling.

Which would be to prefer with speaker placement?

Here is an other question while I´m at it. My UMIK microphone is rely sensitiv at the usb input, It happens a LOT of times when I perform calibrations that suddenly the microphone is available in the Dirac Live program ( happens after placing the mic on new measuring point). Then I have to restart the program because it does not understand that microphone is there otherwise. But even if I´m saving the project before shutting down the input gain of the microphone is reset. Is it important that a set of measurement is done with the exact same output level and input sensitivity on the mic?

BR Jonas
Last Edit: 8 months 2 weeks ago by JONTRE.
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Distorition problems. (and some other questions) 8 months 2 weeks ago #24372

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It's not super critical, as you will play with the target curve anyway. I guess you could just try that both ways. Pointed at the ceiling, high frequencies will be slightly reduced (the mic will read slightly high); and vice versa pointed at the floor.

I wrap the USB cable around the mic boom so that moving the mic doesn't put any stress on the connector.
I am not miniDSP support.

"You must ask the right questions." - Dr. Alfred Lanning's hologram.
-> Have you read the User Manual??
-> Have you drawn and posted a diagram?
-> Have you posted a screenshot?
-> Have you posted your config file?
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Distorition problems. (and some other questions) 8 months 2 weeks ago #24393

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john.reekie wrote:
It's not super critical, as you will play with the target curve anyway. I guess you could just try that both ways. Pointed at the ceiling, high frequencies will be slightly reduced (the mic will read slightly high); and vice versa pointed at the floor.

I wrap the USB cable around the mic boom so that moving the mic doesn't put any stress on the connector.

I did a new calibration yesterday. I did also the new calibration with a "custom system" with no LFE gain. It appears that pre-amp also did put an extra 10dB on the LFE track. Could there been some gain structure problem here that caused the distortions?

I did not have time to test that much last night but it did indeed sound better this way... I´ll return with a final verdict later.

Thx in advance :)
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Distorition problems. (and some other questions) 8 months 2 weeks ago #24394

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If you're pre/pro/avr is adding 10 dB to the LFE signal and you ran a 5.1 or 7.1 calibration, then you would have had the LFE gain applied twice. That could have caused a problem, whether that was it is impossible to know (completely in the dark without graphs or screenshots ;) )

If the distortion problem is now solved, you will probably find some fine-tuning of the target curves to be the next step :) And you need to make sure that your bass management in the pre/pro/avr is good too.
I am not miniDSP support.

"You must ask the right questions." - Dr. Alfred Lanning's hologram.
-> Have you read the User Manual??
-> Have you drawn and posted a diagram?
-> Have you posted a screenshot?
-> Have you posted your config file?
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Distorition problems. (and some other questions) 8 months 2 weeks ago #24460

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Great update @ Jontre and glad to hear that you've solved the first issue of overdriving.
A bit thanks to John for his help once again! :-)
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