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Dirac advances settings 10 months 3 weeks ago #51536

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Ok so I ran REW with Dirac on and off. First time I had MV at -6db.
Dirac on / Dirac off is the first plot showing max boost of 12.3db.



So I adjusted my MV to -12.5db. Sat down started listening to music as that's the point right(!) and then though "hang on I've two target curves... I wonder if the max boost is the same for both?"

So off the sofa I get. Mic back to (as close as I could remember) the same position. And re ran the test.. Note now the MV was at -12.5db.

Interestingly my two target curves don't make much difference to Dirac!



Also interesting the max boost is now only 6.6db.

So should the MV be set to 0db when running this comparison?
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Dirac advances settings 10 months 3 weeks ago #51537

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So should the MV be set to 0db when running this comparison?


I'd use something like -20 dB to be sure there is no clipping happening during the measurements. As long as there isn't any clipping you shouldn't see any meaningful difference in the filters no matter what the master volume is.

Were you making measurements with the left and right channels playing together above? If so I apologise as I should has said to only do one at a time. You'll have a different filter for the left and the right so you want to see what each is individually. I suspect the reason you've ended up seeing a boost of over 10 dB above is because you measured both together?

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Dirac advances settings 10 months 3 weeks ago #51538

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No need to apologise. Let's call that one my practice run!

I'll re-run later at - 20db and left and right separate.

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Dirac advances settings 10 months 3 weeks ago #51539

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No need to apologise. Let's call that one my practice run!

I'll re-run later at - 20db and left and right separate.


I pretty much never make measurements on both channels together so I often forget to mention this :) .

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Dirac advances settings 10 months 3 weeks ago #51540

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I'd use something like -20 dB to be sure there is no clipping happening during the measurements.


Having said this all that really matters is the overall signal level. So if you use say -10dB in REW and -20 dB on your miniDSP the result would be the same as for example -30 dB in REW and 0 dB on your miniDSP. There's no need to go really loud for a test like this. I typically run sweeps that give measured levels around 80 dB other than the for the bass room mode peaks but there is nothing magical about this.

The main thing is to be careful not o accidentally send a signal that is too loud to your speakers and damage them!

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Dirac advances settings 10 months 3 weeks ago #51541

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Dirac advances settings 10 months 3 weeks ago #51542

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Ahhh... thats better! 4.6db max boost.



Does that mean set MV to -5db?
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Dirac advances settings 10 months 3 weeks ago #51543

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Does that mean set MV to -5db?


It's not quite that straightforward since that's the boost at one frequency whereas music has multiple frequencies all at once. Equally they can't individually be close to 0 dB if others are present too. Phase changes affect peak levels too.

What is your system? As in are you directly connecting your DDRC-24 to a power amp with the miniDSP acting as the pre-amp to control volume, or something else?

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Dirac advances settings 10 months 3 weeks ago #51544

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Well at the moment the DDRC-24 is connected to an integrated amp which controls volume.

But the amp has a "home theatre bypass" mode so I can configure any I put to bypass the pre-amp. I might try this at some point in the future but only once I've come up with an alternative volume display - but that's for a different thread!!

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Dirac advances settings 10 months 3 weeks ago #51545

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Well at the moment the DDRC-24 is connected to an integrated amp which controls volume.

But the amp has a "home theatre bypass" mode so I can configure any I put to bypass the pre-amp. I might try this at some point in the future but only once I've come up with an alternative volume display - but that's for a different thread!!


I think I remember discussing this now :) . Maybe go for leaving the master volume at -10dB? Equally in your position you might find greater digital attenuation works better depending on where it puts you in terms of the useable range of your integrated amps volume adjustment.

One factor I hadn't considered before is that the smoothing you have applied will actually mean that what you plotted will underestimate the maximum gain applied to some degree. I've just had a play with a dataset of mine and it seems you can just change this on your calculated A/B to see the difference. What does your filter look like with this set to say 1/48 averaging?

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Last edit: by Ultrasonic.

Dirac advances settings 10 months 3 weeks ago #51546

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Arghh smoothing! Of course you're right!

Right, so with no smoothing there are some really high boosts (of over 15db) once we get above 2khz. But they have no width. By that I mean they look like the impulse response graphs.

Ignoring these "impulse" like spikes, the biggest normal looking boosts are 6.2db.

Applying 1/48 smoothing, the "impulses" disappear and the biggest boosts are the 6db ones.

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Dirac advances settings 10 months 3 weeks ago #51547

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Arghh smoothing! Of course you're right!

Right, so with no smoothing there are some really high boosts (of over 15db) once we get above 2khz. But they have no width. By that I mean they look like the impulse response graphs.

Ignoring these "impulse" like spikes, the biggest normal looking boosts are 6.2db.

Applying 1/48 smoothing, the "impulses" disappear and the biggest boosts are the 6db ones.


Yes, no smoothing won't work for the highest frequencies which is why I suggested 1/48 :) . No smoothing is fine at bass frequencies though.

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Dirac advances settings 10 months 3 weeks ago #51558

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Sorry, I meant Flavio. The guy from Dirac support that’s on all the forums (maybe not this one?)


Sadly no, nobody from Dirac support posts here. At least not while declaring this status.

He answered:

Flavio Fellah commented:

Hello,
yes, in the hardware products the manufacturer assigns appropriate headroom.

I expect that it's something like 10 dBs but miniDSP can answer precisely


I'm afraid that whilst Flavio may hope and expect that miniDSP hardware provides headroom, it does not. Note that Flavio clearly didn't know what miniDSP hardware does. I feel the information in the links I provided shows this, most specifically the example of at least one person who have experienced distortion 'fixed' by providing the required headroom. I have seen others.

You asked if I’m running the SHD at full volume when experiencing this. Yes and no. It doesn’t matter what the SHD master volume is at, the attenuation is the same.



What I asked was whether you run your miniDSP at 0 dB master volume, and with no attenuation applied within the plugin on either inputs or outputs. This matters as you're not going to have an issue if you are routinely applying sufficient attenuation anyway.

I care about this as I don't want other users to be mislead. I'm totally with you that what you think happens would be logical but sadly it is not reality.


Ok, I see now that you were right. It’s right there in the SHD manual on page 51:

“If audio playback is distorted, you may have too much gain internal to the DSP. Dirac Live can apply up to 10 dB of gain, so the output level should be kept lower than -10 dB to guarantee that there is no distortion with a full- scale input signal.
This issue typically occurs when volume control is being done downstream of the miniDSP processor. If so, set the processor master volume at -10 dB, and then use the downstream equipment to control volume.”

Doesn’t explain, why I experience attenuation after running the Dirac calibration tool, but I’ll have to do some measurements on that at some point.

So we can just refer to the manual whenever someone has this problem again.

www.minidsp.com/images/documents/miniDSP...%20User%20Manual.pdf
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Dirac advances settings 10 months 3 weeks ago #51561

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Ok, I see now that you were right. It’s right there in the SHD manual on page 51:

“If audio playback is distorted, you may have too much gain internal to the DSP. Dirac Live can apply up to 10 dB of gain, so the output level should be kept lower than -10 dB to guarantee that there is no distortion with a full- scale input signal.
This issue typically occurs when volume control is being done downstream of the miniDSP processor. If so, set the processor master volume at -10 dB, and then use the downstream equipment to control volume.”

Doesn’t explain, why I experience attenuation after running the Dirac calibration tool, but I’ll have to do some measurements on that at some point.

So we can just refer to the manual whenever someone has this problem again.

www.minidsp.com/images/documents/miniDSP...%20User%20Manual.pdf


Good to see the manual has been updated to include this :) . It wasn't in the earlier version I have. Well spotted!

I'd missed from your earlier posts that you'd experienced a volume reduction. Measurements as you plan would be informative. Is it Dirac 3.09 that you're using?
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