Any measurements on the MiniDSP

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has anyone did the measurements on the MiniDSP? Something like a simple loop back test like we do with sound cards when using measurement tools like HOLM.

I would love to see some. I curious about the MiniDSP performance overall and also what it does under 20Hz. I can use it as a SSF (Shelf filter and boost) but I need to know its measurements first.
 
Doug,

I'm not sure what the question really is. Your question implies there is some sort of inherent frequency response limitation in the MiniDSP that would need to be understood and accounted for. It doesn't work that way.
You can assume the measured output will look exactly like the displayed curve in the MiniDSP software application.....Unless you force it into clipping with too much programmed boost or too much input voltage.

The specified 900mV output voltage limitation is accurate. I see the onset of clipping at about 905mV on my units.

The low frequency response is essentially flat to well below 20Hz. The output capacitor is a large value and should yield a near-DC turnover point with any nominal load.

Anyways, I've done quite a few measurements on mine. What do you want to see? I can program something specific if you'd like.

Cheers,

Dave.
 
I just want to see the real response curve. All products have a inherent frequency response limitation and they all have noise floors to say the miniDSP does not work that way does not make sense since processors, Amps, DCX, Art cleanbox, SMS-1. eD EQ.2 (All products I have owned) and so on all have been measured to show the noise levels and overall response curve. Many have inherent Subsonic Filters, The Art Cleanbox rolls of serverly at 18Hz, the old version of the SMS-1 also rolled off early below 20Hz, I know of several amps and processors that have issues below 20Hz.

"well below 20Hz" is not meaningful enough when my two different sub systems (1 IB array and one multi-sealed disign) go into single digits. I want to know if the MiniDSP can be used as a manual EQ for high end sub systems that have no limits.

EDIT: I see you do comment that its near DC so that is great.

Any measurements you have done would be awesome. Im not the only one interested in seeing pretty graphs ;)

btw, your help on all this is very much appreciated!
 
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Doug,

Well, what I was trying to say (not very well I guess) is that you can consider the MiniDSP response flat....for all intents and purposes.

Anyways, here's a frequency response measurement on one of my MiniDSP units with no crossover/EQ/delay/etc programmed.....into a 10k ohm load.
(Mine is a Rev. B board which explains the -7.9db offset.)

Noise floor (yellow) with a few other measurements as references. Stock DCX2496 outputs (red), line outputs from EMU Tracker-Pre (violet), noise floor of my measuring system (aqua.)

Hope that helps.

Cheers,

Dave.
 

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Well, you have to remember the DCX can spit out signal levels quite a bit higher than the MiniDSP. The majority of folks utilize the DCX2496 improperly, which is why there's such a variation of opinion on its performance. :)

Anyways, with any DSP devices of this type, gain structure has to be well understood and considered to achieve the best performance. Analog circuits don't (generally) have this limitation.

The MiniDSP has terrific test bench performance and the maximum signal levels are well considered (IMHO) to allow the units to be integrated successfully into a wide variety of systems.

Cheers,

Dave.
 
Would you have measurements at full output? Lets say using the digital input for both the DCX and the minidsp, and feeding them with a 0dB digital signal?
That is the way I use my DCX (with an SPL volume8 analog control), so that is how I would also use the minidsp (and specifically the balanced version)

Would you also happen to have distortion and maybe jitter measurements?
 
Do I need to turn down the input and/or output level to avoid overloading? I'm using them with a Emotiva processor and amps.

Probably not. The inputs/outputs of the MiniDSP modules are limited to 900mV, and that's right in the neighborhood of where most amplifiers would be delivering their rated power. So, if your MiniDSP modules are feeding the amplifiers directly I'd say your chances of clipping the MiniDSP outputs are near zero. This is what I was referring to with the "well considered maximum levels" comment. Unlike the DCX (and other commercial units) a multi-channel post-volume control is not necessary with the MiniDSP units.

The Emotiva power-amps have 32db voltage gain (which is a bit more than usual) so your MiniDSP working voltage levels would be a bit less than they would otherwise and reduce the chances of clipping even further.

Obviously, if programming large EQ boosts in the MiniDSP you might get into trouble, so you have to be aware.

Cheers,

Dave.
 
Im comparing them back and forth for the past couple of weeks.

The mini DSP is as good as or better then the stock DCX in many areas. Im testing using analog inputs because that is what my setup needs.

The one bonus I have enjoyed is removing all the issues with RCA to XLR connections. Not worrying about the DCX gain structure is another bonus.

Learning bi-quads has been fun too, I want to try a 96dB Slope ;)

I am concerned about the voltage wrt handling high end 4000Watt sealed subs.
 
Have it all running now except for the center speaker. The bass is intense with the boost at 20Hz to the point that I will have to reduce the boost. My speaker drivers (except for the fifteen year old subs) still need a lot of break-in. Today I will be getting a speaker bracket for above the TV and hooking up the center. It has some of the best drivers made (ScanSpeak's top of the line midwoof and Discovery tweeter). I hope it doesn't make my Etons sound bad. Since they are crossed over/equalized with miniDSPs I should be able to match up their response.
 
Probably not. The inputs/outputs of the MiniDSP modules are limited to 900mV, and that's right in the neighborhood of where most amplifiers would be delivering their rated power. So, if your MiniDSP modules are feeding the amplifiers directly I'd say your chances of clipping the MiniDSP outputs are near zero. This is what I was referring to with the "well considered maximum levels" comment. Unlike the DCX (and other commercial units) a multi-channel post-volume control is not necessary with the MiniDSP units.

The Emotiva power-amps have 32db voltage gain (which is a bit more than usual) so your MiniDSP working voltage levels would be a bit less than they would otherwise and reduce the chances of clipping even further.

Obviously, if programming large EQ boosts in the MiniDSP you might get into trouble, so you have to be aware.

Cheers,

Dave.

Hi Dave,
I've been playing with MiniDSP revA for couple of months now and am very interested in your observation regarding not needing post-XO volume control. Do you just adjust the input level from pre-amp? or do you use the 10K Master Potentiometer connected to both boards to attenuate all channels digitally at DACs?
I would love to hear your input on this subject.

And second thing, i don't have an oscilloscope to measure the input voltage at which it starts clipping? I would love to know the maximum input voltage that i can feed it because i've been playing with various sources/audio cards which output anything from 0.7 to 2.77 volts and the digital meters inside the software never show any clipping(?!?), the music sound good to my ears :), but the thought that I might be clipping it can't let me go?
(May be my ears are not as sensitive to clipping as I thought).

And if I understand correctly the output will always stay 0.9V even if the input is clipping?


I also noticed that the overall volume of my system with DSPs went down since my previous setup, probably because of lower output voltage from MiniDSP.

I used to run software XO and EMU 1820m connected to 6 channel Rotel RMB-1066 and had twice the overall volume level. I went back to re-measure my setup and it turns out the EMU was outputting 2.77V into Rotel amp with 1.5V input sensitivity and all these years it sounded GREAT to me!!!???? I can't trust my ears any longer. If it says input sensitivity of 1.5V do you think it could take up to 2.77V and not clip the input?
Obviously now with 0.9V output of miniDSP it sounds much quieter.(Rotel's volume on woofer is maxed out so I can't increase gain after miniDSP).

Thank you for your help!!!
 
I've done it both ways. The preferable way depends upon your source level, power amp gain, speaker sensitivity, etc, etc. I think for most users with RevA units (that don't have the jumpered input adjustability) you're probably better off having your master volume control upstream in a "preamp" or level attenuator of some sort and disabling the miniDSP level control.

The maximum input voltage varies depending upon programmed EQ settings above 0db. If you just have notches, crossover filters, etc, etc, and no boosting EQ settings the maximum you can input is 0.9 volts RMS. (Any more and the outputs will clip.) Regarding the digital meters inside the software......there's a few threads on the miniDSP forum addressing the "issue."

I'm not sure why your overall volume level would reduce. The miniDSP output voltage levels should be very close to the input voltage levels on a Rev A unit with a nominal setup.

Cheers,

Dave.
 
Thanks for quick reply,
I understand, as long as we keep the average listening level close to the clipping point we are OK (be it 0.9V or 2V, as long as the gain matching is done correctly to keep minidsp happy).

I also found unofficial specs on my amp which apparently accepts up to 5V on input which explains how I was able to listen with 2.77V and not get clipping.
 
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Thanks for quick reply,
I understand, as long as we keep the average listening level close to the clipping point we are OK (be it 0.9V or 2V, as long as the gain matching is done correctly to keep minidsp happy).

But what I can't figure out is that the difference between when I play music softly and when I play it loudly, is dozens of dB... so how do you set the level? Or do you just live with a diminished S/N at low levels?

(I'm not sure if this is in-principle different from all-analog systems.)

In this thread - as in many other places - people are asking for just a plain, simple, ordinary, regular harmonic distortion figure. Seems trivial to produce one... even better, to input 1kHz and show us the output spectrum. I haven't seen even one, no matter how many times I ask.

Why is that?

Ben
 
In this thread - as in many other places - people are asking for just a plain, simple, ordinary, regular harmonic distortion figure. Seems trivial to produce one... even better, to input 1kHz and show us the output spectrum. I haven't seen even one, no matter how many times I ask.

Why is that?

Ben

Because it's just not that important. :)
I can easily generate one if you want, but what would you deduce from it? Simple harmonic distortions from gadgets like these are waaaay less than any speaker system you'd use them with. And there are a few experts that believe harmonic distortion measurements are completely meaningless anyways. :)

Cheers,

Dave.
 
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