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Minidsp DDRC-88A Dirac Multichannel DSP Review

amirm

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#1
This is a review and detailed measurements of the Minidsp DDRC-88A balanced 8 channel in, 8 channel out, Dirac and manual EQ DSP system. It is on kind loan from a member and costs US $999. The connectivity as you see is with phoenix connectors and if you order a set of cables to XLR for that, it would add another $60. A remote is included as I think a Dirac 3.0 license plus manual configuration software.

The front is business like and doesn't give you much control over the unit other than changing configs and volume:
Minidsp DDRC-88A Dirac Live multichannel room correction audio review DSP.jpg


Back panel shows the rich connectivity of both unbalanced (RCA) and aforementioned balanced:
Minidsp DDRC-88A Dirac Live multichannel room correction bakc panel XLR Inputs audio review DSP.jpg


Due to some mix up, I did not get the external adapter and had to use my lab power supply. It drew 750 milliamps at 12 volts.

To be clear, the DDRC-88A digitizes all the inputs, processes them using a DSP and then converts them back to analog. Stated sample rate is said to be 48 kHz at 24 bits.

The USB connection is sadly for control only but there, the provided software worked beautifully in configuring the unit, changing DSP, levels, etc. All my testing was doing using the balanced inputs and outputs.

DSP Audio Measurements
I ran my testing as if the DDRC-88A is an analog preamp since that is the connectivity it provides. All effects unless said otherwise were disabled. Here is our dashboard then:

Minidsp DDRC-88A Dirac Live multichannel room correction.png


There is a default -8 dBFS of headroom which makes sense based on what I have heard the requirement from Dirac to be. At that default value, the gain is negative causing 4 volt input to produce 2 volts out. That can be adjusted of course and that is what I did to get the performance relative to output level:

Minidsp DDRC-88A Dirac Live multichannel room correction THD+N vs Level Audio Measurements.png


Unlike many AV processors with EQ, as you see the DDRC-88A is fine producing output in excess of input to the tune of 4.7 volts before clipping.

Back to the dashboard, I turned on crossover processing and it did not impact the performance whatsoever. As it is, we have 15 bits of distortion-free range (90 dB of SINAD).

Dynamic range is just good enough to not impact the distortion-rating which dominates:
Minidsp DDRC-88A Dirac Live multichannel room correction SNR Audio Measurements.png


Frequency response is droops a bit at 20 kHz:
Minidsp DDRC-88A Dirac Live multichannel room correction Frequency Response Audio Measurements.png


It seems that the sample rate is 44.1, not 48 kHz. But maybe there is a setting for that?

Intermodulation and noise are well above state-of-the-art analog preamps:
Minidsp DDRC-88A Dirac Live multichannel room correction IMD Audio Measurements.png


THD+N sweep versus frequency shows some low frequency perturbations:

Minidsp DDRC-88A Dirac Live multichannel room correction THD+N vs Freq Audio Measurements.png


The overall level is high also. My sense was that this was due to noise shaping and indeed it was:

Minidsp DDRC-88A Dirac Live multichannel room correction FFT Audio Measurements.png


Quantization noise in the audible band is pushed into ultrasonics. Since THD+N vs frequency has a wide, 90 kHz bandwidth, it takes in all the ultrasonic noise and penalizes the device with it. In reality worst case distortion spike is still at -90 dB.

DSP Performance
As a quick test, I dialed in an 80 Hz crossover for say, a subwoofer and used the default 48 dB/octave:

Minidsp DDRC-88A Dirac Live multichannel room correction Crossover Audio Measurements.png


Looks clean and nice to me.

Conclusions
The performance of Minidsp DDRC-88A is just good enough to say it is not broken. It is significantly better than recently tested DSPeaker Anti-mode 2.0 Dual Core. With a SINAD of 90 dB, you are good using it on an amp having a SINAD of 80 dB. If the amp is any better than that, then the minidsp degrades its performance.

Based on measurements alone, I was borderline on recommending the DDRC-88A. But the software pushed me over the line, making it a joy to program the thing to build a discrete 7.1 system or two active speakers. Sadly, you can't do better than a good AVR or AV Processor although it does give you Dirac EQ and very nice set of programmable EQ.

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As always, questions, comments, recommendations, etc. are welcome.

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Trdat

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#3
For about the same price you can grab the Okto and implement software version of DSP, yeh ends up a little more expensive but you get pristine measurements with your chosen DAC.

I think people need to get over hardware based DSP when software is more versatile and allows you to choose the best equipment to implement it with.

It's not like your getting a range of Dolby, or other decoders for surround plus Dirac and top of the line measurements.
 

phoenixdogfan

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#4
For about the same price you can grab the Okto and implement software version of DSP, yeh ends up a little more expensive but you get pristine measurements with your chosen DAC.

I think people need to get over hardware based DSP when software is more versatile and allows you to choose the best equipment to implement it with.

It's not like your getting a range of Dolby, or other decoders for surround plus Dirac and top of the line measurements.
Just run Dirac on the pc, do the 7.1 decoding with JRiver, and pass the signal via usb to the Octo 8.

IDK, miniDSP always wants to bundle something you don't want, and omit something you do in every offering.

This one, like many of their products has no usb input and it outputs analog with a mediocre dac. I for one would want the eq, the electronic crossovers, multichannel DSP, decoding for all the legacy 5.1, stereo and 7.1 codecs, and a usb input and usb output. And nothing else.

That would make it something you could stick between a pc and a multichannel dac, and be reasonably confident it wasn't distorting anything, and it could process everything but Atmos and DTS-X. Don't know why they can't or won't just do that for l.t. say $1500. If they did, I'd buy one in an instant. But this thing...
 
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amirm

amirm

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Thread Starter #5
Just run Dirac on the pc, do the 7.1 decoding with JRiver, and pass the signal via usb to the Octo 8.
Dirac on PC is expensive. Multichannel version is $500.
 

Vasr

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#6
Thanks. Not too bad if it did indeed go through a ADC-DAC cycle for the test.

1. Can you please do at least the basic measurement with unbalanced in and out? Just a hygiene test. This would likely be the most common use of this as an outboard processor to AVR pre-outs.

2. While the gain can be adjusted to give the full 4 volts, I am not sure you have that option with Dirac doing the correction. Depending on the correction, it will likely lead to digital clipping. Unless the "gain adjustment" is on the analog side after correction and converting back to analog. It wasn't clear what this gain adjustment did in the test. Digital/Analog? Before or after Dirac? This is critical to understand whether it can actually be used for an amp that requires more than 2V.

3. Is it possible to test this with Dirac enabled but no filters installed (so no measurements needed)? Again another hygiene test just to make sure there are no surprises.
 

Vasr

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#7
If they really wanted to sell a lot of these, they could just combine DDRC-88A and DDRC-88D with a USB audio in/out to this unit along with analog in/out so people could choose digital only correction or analog-analog depending on their requirement. Should be quite simple to do this routing. Or they could just put a USB in/out to DDRC-88D to increase the sales of that unit. You could then just inline it with Okto Dac8 Pro.

But in typical miniDSP fashion, they would not think they have done their job unless they have selected combination of features and connectors that always have people scratching their heads on how to use/connect to 90% use cases requiring all kinds of adapters and dongles. :(

Only the SHD series avoids this quirkiness.
 

PeteL

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#8
We are starting to have some sort of a pool now of dsp capable units, with many AVRs recently reviewed. Looks they all have some compromise compare to pure DAC or ADC, but to me it's somehow to be expected, and In many cases, I believe the purist, pure performance approach can be trumped by the benefits. Would be great to have also have some chart, to kind of measure the value of what's out there for people who'd like to dig in the room correction thing.
 

Vasr

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#9
Also the bass management module (their DSP bass management not Dirac DLBC which is not available for this) is an extra add-on that adds $100 more to the price.
 
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#10
their SHD Studio is a later design with a more powerful DSP, 96/24 resolution and USB input if you don't need multi-channel and want to use your existing DAC. I use one for USB-AES conversion and DSP EQ (-20dB gain, Volumio disabled), surprisingly good sound quality
 
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carlob

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#11
Since you raised the gain It would be interesting to test if it clips with Dirac enabled, which is what happens with the Minidsp SHD if you don't attenuate the signal by 8/10dB
 

voodooless

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#12
Why does the filter stop attenuating past -45 dB? That does not make sense for a "normal" filter.
 

milosz

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#13
Of all these DSP crossover, speaker correction, room correction gizmos my favorite is still the DEQX. Their algorithm for measurement and correction is the best IMHO. If you buy an older used one it's not too expensive - I bought a PDC 2.6 with balanced outputs for $630. Learning curve can be a bit steep, but there is help via forum available. It would be pricey to use for 5.1 or more, but for stereo DEQX is great.
 

tecnogadget

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#14
Of all these DSP crossover, speaker correction, room correction gizmos my favorite is still the DEQX. Their algorithm for measurement and correction is the best IMHO. If you buy an older used one it's not too expensive - I bought a PDC 2.6 with balanced outputs for $630. Learning curve can be a bit steep, but there is help via forum available. It would be pricey to use for 5.1 or more, but for stereo DEQX is great.
How would one integrate DEQX with AVR pre outs for 5.2 or 7.2 channels ?? My only experience has been using Feedback Destroyer with 1 subwoofer (really nice results).
 

milosz

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#15
DEQXs are stereo. For 5.2 you'd need three or four of them. For 7.2 you'd need....um, I think, 7. You would connect the 5.2 or 7.2 analog outputs to the analog inputs of the DEQX's. And you'd have to use the newer DEQX's that have digital outputs which makes "daisy chaining" in multichannel setups work. These newer DEQX's have the ability to run in master and slave mode, so the master would control the volume level and the slaves would follow. You could also just leave level control in the DEQXs to a fixed setting, and adjust your levels with your processor, but there would likely be a signal-to-noise penalty with that kind of setup.

DEQXs are 2 in / 6 out. They are designed to be speaker / room correction and 2 or 3 way crossovers. So I guess you could have a 5.2 system with all active speakers - fifteen amplifiers for 5 channels of tri-amped speakers, and two amps for the subs....

It gets quite expensive trying to use DEQXs in a multichannel setup. I really can't see anyone but a home theater contractor with wealthy clients or a very well-heeled hobbyist.

DEQX can do things like linear phase crossovers, bass group delay correction, crossovers with 200 dB per octave slopes.....they can generally correct a speaker to flat response ± 0.5 dB if you can get a really good measurement ( basically have to do such speaker correction measurements outdoors to eliminate room reflections, or use an anechoic chamber if you have one handy.....)

You can get decent speaker correction to flat from 200 Hz up of about ±1.5~2.0 dB with careful measurement in a typical home. If you are going to be setting up 5.2 speakers with five three way (triamp) speakers setting things up with the DEQX would become something of a part time job until you got it all dialed in...

In my opinion, using DEQX for multichannel audio is prohibitively expensive and impractical due to the amount of work you'd need to do.... the amplifiers you'd need to buy...the speaker cabling.... I imagine DEQX knows of some pro home theater installers who are adept at this. Multichannel DEQX boggles my mind. But given sufficient money and effort it could be done.

I think the sound from the 5.2 or 7.2 analog outputs of a typical pre-pro would be somewhat disappointing, given how mediocre they all seem to be as DACs based on measurements here on ASR. I think you'd get better sound if you could find some way to output multiple SPDIF or AES EBU two channel datastreams - one SPDIF for front left/right , one SPDIF for rear left / right, one SPDIF for center and height, a SPDIF for 2 channel subs.... there must be a way to extract these from HDMI. By using 2 channel SPDIF you could feed digital to the DEQXs and take advantage of the DAC inside the DEQX and avoid a trip through the A-to-D stage on the DEQX's analog inputs. Now, you are approaching a large engineering project....
 

Trdat

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#16
Dirac on PC is expensive. Multichannel version is $500.

Audiolense is 390 euro, I admit it's expensive but in the overall scheme of things you get to chose your own DAC.
 

Martin

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#17
I've often thought the miniDSP DDRC-88A was made for use with the Outlaw Audio Model 976 pre/pro and Model 7000x 7-channel amplifier. That gives one a 7.2 channel Dolby TrueHD / DTS HD Master Audio / Dirac capable 130WPC system for less than $3,000 that would likely measure and perform better than any of the recent crop of Dirac receivers. The only thing missing are height channels.

Martin
 

voodooless

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#18
I've often thought the miniDSP DDRC-88A was made for use with the Outlaw Audio Model 976 pre/pro and Model 7000x 7-channel amplifier. That gives one a 7.2 channel Dolby TrueHD / DTS HD Master Audio / Dirac capable 130WPC system for less than $3,000 that would likely measure and perform better than any of the recent crop of Dirac receivers. The only thing missing are height channels.
Well, looking at the SINAD, it won't measure better. The recent Denon's are 6 tot 10dB better than this.
 

Absolute

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#19
390 Euro for Audiolense is not expensive, neither is this Minidsp with this many channels and Dirac. I would always recommend the digital version and a better dac like the Okto 8 channel, but this thing is okay if you have normal speakers with low-ish sensitivity.

I have Minidsp 2x4 HD and that thing is too noisy for my compression driver, so I bought the digital stereo-thing with Dirac (DDRC-22d) to get Dirac.
Both works, only one is acceptable with sensitive speakers.
MiniDSP as a company baffles me no end with all their products yet none of them really ticks all the boxes in any one of them.
 

voodooless

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#20
If you can't invest the money, you can always invest some more time and learn how to do it yourself using freeware tools.. there is more than enough out there.
 
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