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miniDSP 2x4

AngelRa

AngelRa

Active Member
The miniDSP 2x4 has been called "the best thing audio ever". But it is?

My brother, after reading all the hype, purchased 3 miniDSP 2x4. For some years he tried to get some improvement in his sound using them but he always ended up removing them. Frustrated, he was certain he was doing something wrong. He ended selling 2 of them and sending me one to see if I could get the great sound it is supposed to provide.

Received the unit. To educate myself I read the manual and saw several youtube videos.

I used my B&K 3384 reference mic, an UMC 202 24/192 audio interface. Proceeded to create correction curves and sent them to the miniDSP. There was not much to fix so the curves were mild, almost flat.

To listen I used a pair of old monitors connected to the incredible Hewlett Packard HP467A mono amplifiers. The sound with the miniDSP was not improved, instead it degraded. I repeat the entire process with same results.

At this point I decided to set the miniDSP in full bypass mode. All filters, and EQs in bypass. In this mode it should behave like a cable. Proceeded to listen and again the sound was significantly degraded. Sound degraded in texture and dynamics. It seemed grany and weak.

This needed to be understood, so I took it to my lab.
Conneted the miniDSP to a signal generator set for square wave and an oscilloscope. CH1 in yellow is the input signal going into the miniDSP, the blue is the output of the miniDSP. Signal out of the miniDSP is attenuated so I adjusted the scope to match their size in the screen.

Response at 1 KHZ.
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EDIT: The compression reported before was caused by the attenuator used before the miniDSP.

The miniDSP did not compressed the signal as I originally saw.
 
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Also notice the increase in ringing noise.

EDIT: Ringing noise did increased when input signal increased amplitude.
 
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My conclusion:

Inconclusive, the observed phenomena is normal for digital sampled sound.
 
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AngelRa said:
My conclusion:

The miniDSP 2x4 distorts, reduces dynamics, and create sound artifacts. This device will deteriorate sound more than can ever improve it.
Click to expand...

There are an awful lot of people using them that report positive results. And, having been around quite a while, surely this is not the first attempt at measuring the device. Not sure why you'd use square waves though for this.

Have you sent/reported your observations for comment to the miniDSP forum?
 
whoaru99 said:
There are an awful lot of people using them that report positive results. And, having been around quite a while, surely this is not the first attempt at measuring the device. Not sure why you'd use square waves though for this.

Have you sent/reported your observations for comment to the miniDSP forum?
Click to expand...

I have not reported to the miniDSP forum. Will take a look at it.
Have you personally test/used one?
 
While I've not measured it, the Behringer DCX 2496 compresses the sound too (similar device). While this is desirable for PA use, it's not great for HIFi use. I find that it slightly dulls the transients and makes the treble lose its luster. I use mine only on woofers and subs crossed at or below 160 Hz. The detriment to the sound above that is too great of a liability. Most of what I need heavy duty EQ, phase and time adjustment on is in bass region anyway, so it works out OK for me. I have heard the bigger (4 x8?) miniDSP unit as used by Sigfried Linkwitz during his demonstrations at Audio Shows and it seemed to sound very good. Maybe that one is a better unit capable of better fidelity?
 
soundmig said:
While I've not measured it, the Behringer DCX 2496 compresses the sound too (similar device). While this is desirable for PA use, it's not great for HIFi use. I find that it slightly dulls the transients and makes the treble lose its luster. I use mine only on woofers and subs crossed at or below 160 Hz. The detriment to the sound above that is too great of a liability. Most of what I need heavy duty EQ, phase and time adjustment on is in bass region anyway, so it works out OK for me. I have heard the bigger (4 x8?) miniDSP unit as used by Sigfried Linkwitz during his demonstrations at Audio Shows and it seemed to sound very good. Maybe that one is a better unit capable of better fidelity?
Click to expand...

I have a Behringer Ultra Curve Pro in a closet. Which I remember sounds better than the miniDSP. I may take some time and measure it.
 
soundmig said:
While I've not measured it, the Behringer DCX 2496 compresses the sound too (similar device). While this is desirable for PA use, it's not great for HIFi use. I find that it slightly dulls the transients and makes the treble lose its luster. I use mine only on woofers and subs crossed at or below 160 Hz. The detriment to the sound above that is too great of a liability. Most of what I need heavy duty EQ, phase and time adjustment on is in bass region anyway, so it works out OK for me. I have heard the bigger (4 x8?) miniDSP unit as used by Sigfried Linkwitz during his demonstrations at Audio Shows and it seemed to sound very good. Maybe that one is a better unit capable of better fidelity?
Click to expand...

I do not know if the 4x8 would be better. Maybe the HD version is better.
 
AngelRa said:
It is what it is. This are hard facts. This proves to me that given the right amount of belief, people will hear an improvement when actually is deteriorated.
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A hard and fast conclusion with minimal study.

I have no dog in the race (I enjoy learning through discussion as opposed to just reading), but have you tested multiple units?
Have you tested with sine wave versus square wave (my knowledge of the science is minimal, but I thought music would be a sine wave)?
Is it possible that no one (not even the mfgr.) has ever done a scientific test on a MiniDSP, and you have revealed the Emperor's new clothes (wouldn't be the first time something like that happened)?
Will you be sharing the pictures of your test results?
Are you going to reveal the info on the other equipment used (speaker mfgr/model, preamp model, music source, equipment connection layout, etc.)?

Inquiring minds (well, mine anyway) want to know!
 
AngelRa said:
I have not reported to the miniDSP forum. Will take a look at it.
Have you personally test/used one?
Click to expand...

I indeed have a miniDSP Balanced 2x4 and a DCX2496. I would describe most of my testing by ear and don't notice this compression or horrible results described. That said, I have done frequency sweeps with both in the system(s) using measurment microphone and Room EQ Wizard. Didn't notice any anomalies in the response. Only improvement noted in smoothness of overall response with the correction factors applied.
 
robgmn said:
A hard and fast conclusion with minimal study.

I have no dog in the race (I enjoy learning through discussion as opposed to just reading), but have you tested multiple units?
Have you tested with sine wave versus square wave (my knowledge of the science is minimal, but I thought music would be a sine wave)?
Is it possible that no one (not even the mfgr.) has ever done a scientific test on a MiniDSP, and you have revealed the Emperor's new clothes (wouldn't be the first time something like that happened)?
Will you be sharing the pictures of your test results?
Are you going to reveal the info on the other equipment used (speaker mfgr/model, preamp model, music source, equipment connection layout, etc.)?

Inquiring minds (well, mine anyway) want to know!
Click to expand...

Yeah, lots of questions when something that has been around for long as it has, with generally good results reported, then along comes a rather scathing indictment.
 
I would love to see the graphs as well, thanks for taking the time to share your measurements. The 2x4 is their entry level unit, and my understanding is that the 2x4 runs different chips and has lesser specs from some of their more expensive products. I wouldn't be surprised if the ADC to DAC chain in the 2x4 also introduced some noise by itself.

I'm also not surprised there are applications, like for @soundmig, where it can provide benefits.

Again, please do fix the pictures! That would be really valuable to those of us playing with active DSP but without a well-stocked test bench.
 
whoaru99 said:
I indeed have a miniDSP Balanced 2x4 and a DCX2496. I would describe most of my testing by ear and don't notice this compression or horrible results described. That said, I have done frequency sweeps with both in the system(s) using measurment microphone and Room EQ Wizard. Didn't notice any anomalies in the response. Only improvement noted in smoothness of overall response with the correction factors applied.
Click to expand...

I felt the same about the DCX 2496 until recently. I've built some very revealing speakers and was using the DCX 2496 as a crossover between OB bass units and the bass-mid/tweeter set-up. I was not too happy with the HF performance and decided to take the DCX out of the Mid-Hi circuit and just use it between the pre-amp and the amp that drives my 12" OB woofer. Wow ... I was shocked at how unconstrained and open the bass-mid/tweeter unit sounded without the DCX in the loop. Its subtle and I doubt that you can measure it (it measure just fine with the DCX in the loop) but the "sound" is way better without it mucking up the signal. I'm sure that it is ADC/DAC artifact that was causing the problem. FYI - I was not using the DCX for any eq in the mid-hi leg. My mid/hi unit is very linear without any help. I did use the DCX to determine the time difference between the 5" mid-bass and the tweeter which allowed me to built a proper physical time alignment set up. The DCX is a very useful item and I like it - but its not the most transparent piece for hi-end audio use. I also have a Bryston 10B-LR ... I'll have to fire it up sometime and see if it is more transparent than the DCX (for use as a crossover). Not a fair comparison based on price. Evenso, the Bryston just doesn't have the processing horsepower of the DCX.
 
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