Minidsp C-DSP 8x12 V2.0 Review

[amirm]

This is a review and detailed measurements of the Minidsp C-DSP 8x12 V2 DSP for automotive (12 volt) applications. It was kindly sent to me by a member and costs US $760.

As the name indicates, you have 12 analog outputs which can be driven by either digital or analog inputs. USB connections is for control and configuration (no data transfer). Back panel shows the 8 analog inputs and dual digital:

The relay uses an RJ-11 connector/telephone wire so you should be able extent or shorten the cable as you wish. The LCD is very high contrast and volume control responsive. For testing I powered the unit using my lab bench power supply at 12 volts. Idle current usage was 570 milliamps (6.84 watts). So be sure to use the remote connection to power it on when the head unit turns on.

If these measurements are new to you, I suggest watching my video on DAC measurements.

Minidsp C-DSP 8x12 V2 DAC Measurements
Using Minidsp configuration utility, I muted all channels but the coax S/PDIF input. I routed that to RCA channels 1 & 2 and adjusted the volume to get 2 volts nominal out:

Noise and distortion as expressed in SINAD is pretty good for the application:

I set the volume to 0 and gradually turned the volume up from -30 dB to 0:

So even though we have an RCA connection, it is good to 4+ volts. SINAD goes up another 4 notches as a result. Many automotive products support higher voltages to improve noise immunity so this is good.

We can see the improvement in noise level in our standard dynamic range tests:

IMD test shows low distortion at extreme:

Linearity droops a bit as we get near 20 bits but is certainly good enough for what we need here:

Jitter spikes are visible but they are well below audibility let alone noise floor of a car:

The filter is the typical default you fine in audio DACs:

Attenuation is good enough that there is not much frequency dependence:

I was surprised a bit about low frequency saturation with 0 dB volume.

Minidsp C-DSP 8x12 V2 DSP Measurements
I spent a bit of time configuring various signal processing modes and the impact on frequency response. Let's dial in a crossover at 1 kHz/48 dB per octave:

Someone less lazy than me can see if the slope is right or not. The crossover frequency is right on at 1 kHz.

Next I dialed in low and high shelving:

Looks correct. How about single filter with different Q levels?

Looking good. Let's test very high Q and see if we get ringing:

We don't. Please note that the sharp dip is due to lack of data points in the measurement and not the transfer function looking that way.

I turned on a PEQ and measured IMD (not shown) and it had no impact other than the expected due to change in frequency response.

Minidsp C-DSP 8x12 V2 Analog In/Out Measurements
In case you are stuck with analog pipeline in your system, let's treat the unit as a black-box pre-amp and see how it performs:

Ah, we take a pretty big hit in the form of distortion. We lose almost 20 dB relative to using digital input! You can see this better in IMD vs level:

I guess if you are turning the volume down at the source you will enjoy the best case scenario but even that is not great (0.7 volts in).

Frequency response is very flat and nice:

Noise is decent as well:

So is crosstalk:

There is no frequency dependence but levels are high enough that this is kind of moot:

I happen to have the measurements for a desktop Minidsp so we can compare them:

So not much worse.

Conclusions
I really like the extensive capabilities, ease of configuration and digital input performance of C-DSP 8x12 V2. They should let you optimize the sound of your car (or with power supply at home), far better than not using one. Clearly company cares about engineering and design in this regard. Performance using analog input though drops a few notches so if at all possible, use digital inputs.

Overall, I am going to recommend the Minidsp C-DSP 8x12 V2.0 signal processor.

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

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

 

[Sokel]

Is there a chance to measure SINAD of lows with couple of filters loaded ?Like 40Hz while loaded with an x-over at 80Hz?

Thanks Amir!

 

[amirm]

Is there a chance to measure SINAD of lows with couple of filters loaded ?Like 40Hz while loaded with an x-over at 80Hz?

Thanks Amir!

As I noted, I measured IMD with a filter like that active and it hardly impacted it. It is not a very scientific thing to do because when you change the bandwidth, the nature of the measurement changes.

 

[fordiebianco]

Another interesting review. Unfortunately my cars are all way too small for this to be applicable, but interesting nevertheless. Many thanks, @amirm

 

[Aperiodic]

Unless it can DSP away vibrating sheet metal, which I doubt, seems like a waste of $700+. It also seems silly to quibble over a few dB SNR in an automotive environment.

 

[poxymoron]

Wow, this is something new, and again, the type of review we don't get to see anywhere else. Impressive product. Thanks Amir.

 

[amirm]

Unless it can DSP away vibrating sheet metal, which I doubt, seems like a waste of $700+. It also seems silly to quibble over a few dB SNR in an automotive environment.

No way. EQ is even more mandatory in a car as the modal region extends way up to hundreds of hertz to say nothing about the suboptimal placement of speakers. As to SNR, you sure as heck don't want a tweeter 2 foot away from your ear hissing.

 

[DanielT]

No way. EQ is even more mandatory in a car as the modal region extends way up to hundreds of kilohertz to say nothing about the suboptimal placement of speakers. As to SNR, you sure as heck don't want a tweeter 2 foot away from your ear hissing.

Thanks for the test Amir.

Unless it can DSP away vibrating sheet metal, which I doubt, seems like a waste of $700+. It also seems silly to quibble over a few dB SNR in an automotive environment.

Speaking of DSP in car sound systems. Here an example. A seventeen year old example:

Using digital signal processing (DSP), the sound is adapted to the shape of the interior and the location of the loudspeakers. DSP technology is also used to fine-tune the tone curve, thereby contributing to natural sound character.

Volvo Audio - Volvo Cars develops Premium Sound for a high quality audio experience

The first audio unit that bore Volvo’s name was presented back in 1969. Since then, Volvo Cars, together with leading manufacturers, has developed its own audio systems and introduced a number of world-firsts. Among other things, the world’s first RDS radio was in a Volvo, as was the first...

www.media.volvocars.com

 

[TimoJ]

No way. EQ is even more mandatory in a car as the modal region extends way up to hundreds of kilohertz to say nothing about the suboptimal placement of speakers. As to SNR, you sure as heck don't want a tweeter 2 foot away from your ear hissing.

Also notice that this unit supports 8 channel Dirac Live (extra cost option). I have one of these with Dirac in my car, results are pretty awesome.

 

[K man]

Oh, this is a review I've been waiting for! (I've made multiple attempts to get miniDSP to send you a sample, @amirm.)

I'm using this one to control my 4.2.3 system at home. I have it plugged in between my receiver and the power amp + active subwoofers. The amount of configuration options in this one, including Dirac Live, makes it absolute magic! It's really the key to the sound quality I now have in my surround system, combining manual PEQ, channel leveling, Multi-Sub Optimizer (5 sub channels; 3 subwoofers + 2 "virtual" subwoofers on my full range fronts), Dirac Live and per speaker pair optimized crossovers.

I've had two issues with it though. First of all it's supersensitive to a clean 12V input, so make sure you have a clean such source. (Normal switching 12V adapter won't do.) The second thing is that it's very sensitive to proper grounding. It took me quite a bit of effort to get rid of all grounding generated background noise.

However, with a clean 12V source and properly done grounding, I would say this is a superior option to miniDSP DDRC-88A. Especially since it has more channels out, allowing for more subwoofers.

 

[Vini darko]

Very cool gadget thanks for the review.

 

[GWolfman]

Interesting! Too bad the analog path suffered so much, but at least it offers a feature set no one else does.

 

[restorer-john]

Even A/D-D/A is quite respectable for such a device. I'm pretty impressed and thanks for the extensive review @amirm

 

[markk]

Thanks for reviewing it for us. I figured it was a bit of work to review!

Note it's only $550. The invoice was for ~750 or so because somewhere in the box is a umik2 mic...

I bought it more as an experiment. I have a couple sealed subs that I want to LT, and just thought about a 2x4HD, but it's not that much more for quite a bit of versatility. Makes for a pretty respectable 3 way digitial xover if you use the digital inputs.

Unfortunately, I take a bit of a hit using the analog inputs. Since this will be used with a Denon 3800H, well, the SINAD is only in the high 80's, so, using the analog portion of the miniDSP doesn't cause a big hit. Still, the ability to LT the sealed subs and potentially manually correct the main 3 up front for $550 is a pretty good experiment to see if the benefits of eq outweigh the slight hit. Similar to what K man had mentioned in his post.

Thanks again Amir

 

[jhaider]

I'm using this one to control my 4.2.3 system at home. I have it plugged in between my receiver and the power amp + active subwoofers.

Are you using the 12V trigger? How would one wire a home 12V trigger to a car audio REM IN anyway?

I've had two issues with it though. First of all it's supersensitive to a clean 12V input, so make sure you have a clean such source. (Normal switching 12V adapter won't do.)

Hmm. Which power bricks have you tried and what ended up working for you?

 

[K man]

Are you using the 12V trigger? How would one wire a home 12V trigger to a car audio REM IN anyway?

Yes, I do. I split the 12V+ from the power source into two wires, one connected to DC IN +, the other connected over a relay and then to REMOTE IN. I then connected the trigger from my Denon receiver to control that relay. So when the trigger from the receiver goes on, the relay short the second 12V+ to the REMOTE IN.

Which power bricks have you tried and what ended up working for you?

I tried a few switched adapters first, but none of the did it. I then ended up using this one, but I guess any sufficiently well filtered or clean 12V source would do.

 

[ferongr]

Does the ADC portion really start to saturate above 0.8V? That's a very line input low voltage, esp. for automotive where 4V or even 6V audio line outputs are common.

 

[K man]

Does the ADC portion really start to saturate above 0.8V? That's a very line input low voltage, esp. for automotive where 4V or even 6V audio line outputs are common.

It's possible to configure the sensitivity of the input:

Source: C-DSP 8x12 DL User Manual (page 55)

@amirm's diagram ends at 2V, while default should be 4V. Could we worth checking.

Could maybe also be worth checking the 8V high level input, if your line level is >4V. Could we have the high level input tested as well, @amirm?

 

[nalianth]

I have been running the 6x8 and 8x12v2 (upgraded for FREE from v1 board) since 2016 in my vehicles. These are a very good alternative to mainstream automotive DSPs and allow the creation of a full active speaker system...which as mentioned earlier is critical to correcting (as much as possible) sound from each speaker location. I have had zero issues with them.

 

[Ken Tajalli]

Is there a chance to measure SINAD of lows with couple of filters loaded ?Like 40Hz while loaded with an x-over at 80Hz?

Thanks Amir!

For car use, 60dB SINAD is overkill. Unless you are in a deserted indoor car park somewhere in Chernobyl!