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miniDSP Harmony 8x12 Car Audio Amplifier - Review and Measurements

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This is a review and the results of a measurement session from the miniDSP Harmony 8x12 car audio amplifier. The company provided me with a sample. It retails at 1049 USD on the miniDSP site (https://www.minidsp.com/products/car-audio-dsp/harmony-8x12).

It is quite a remarkable box that seems to fly under the radar. The feature set is very flexible and allows therefore for a lot of implementation options. I think it is uninteresting for a lot of car audio folks because the power ratings are perceived as low. On the contrary, the Harmony is very popular in the car audio development world where it is used for research and development tasks and is praised as a flexible and good sounding unit. I will cover some areas that are interesting for the (potential) user, but not really explained in the marketing material.

Since I was curious how the unit measures, I hooked it up on the bench to the Apx582. Power plant for all measurements is a TDK-Lambda GEN20-76 at 14.4V. Electric loads were non-inductive 2, 4 and 8 Ohms resistors. Only one channel was measured at a time.

Features

The Harmony 8x12 features six discrete inputs via USB. Two additional input channels are SPDIF via TOSLINK. Although the amp is named “8x12”, you either use the six USB inputs or the SPDIF via TOSLINK in. There are no analog ins. The housing is of a premium looking and feeling aluminum which doubles as a heatsink. Cooling is all passive.

Pic 1 unit.jpg


All other amenities are similar to other car amplifiers in this price range: 12V power supply is a screw terminal (would have wished for a Molex connector here), speaker outs are on a Molex connector (output harness is provided), power on is triggered via positive voltage on the „remote“ in, volume control is done by a separate box with OLED screen connected by the infamous RJ11 that by itself can be controlled via another miniDSP remote control. Unnecessary but cool.

Pic 2 connector side.jpg


The DSP and USB section (left) is split from the power amp side (right). Heart and brain of the DSP is XMOS U11692C20 and a Analog Devices ADSP21489. The installation of custom DSP code from Sigma Studio or AudioWeaver is not documented in the official miniDSP files.

tempImagecj3zPK.png


The A2B input/output section cannot be used with the current firmware.

Every output channel of the 12 can be configured individually to three modes:
  • BTL (bridge-tie load). The standard mode. Up to 40 W rms into 4 Ohm.
  • PBTL (parallel bridge-tie load). Two output channels are combined (hence you lose one) for 80 W rms into 2 Ohm.
  • Line-Out. The output channel functions as a DAC only. 5 V rms max output.
BTL Measurements

At 5W into 4 Ohm the unit delivers at a very good level for car audio!

BTL_-4R-8,858dBFS_dash.PNG

At 0 dBFS (max output level), the SINAD decreases only slightly. Power is -0.22 dBr under spec (negligible).

BTL_-4R-0dBFS_dash.PNG

THD over measured level is nice and low. The usual "hockey stick" is not visible because with 0 dBFS Input signal, you are far from clipping this amp. One worry less when building a car system.

BTL_-4R-8,858dBFS-THDoverLevel.png

With different loads at 2, 4 and 8 Ohm (AES17 filter active) the audible band is influenced minimally.

BTL_-2R-4R-8R.png


PBTL Measurements

When a channel is switched to PBTL, two channels become one, hence the number of output channels decreases to 6.

In PBTL mode, the SINAD decreases. Since PBTL is for "bass speakers", I cannot a see a problem here.

PBTL_-2R-11,83dBFS.PNG


At max level (0 dBFS) SINAD is slightly better. Power is super slightly under spec with -0.22 dBr

PBTL_-2R-0dBFS.PNG


THD over frequency

PBTL_-2R-11,83dBFS-THDRatio.PNG


THD over level has a interesting bumpy curve. My guess is, that the amp works below 1 Watt not in a real PBTL to save power when the buck boosters are off.

PBTL_-2R-11,83dBFS-THDoverLevel.PNG


The plop check is fine. While switching the unit on (first spike after 4 seconds) and off (second spike just before 10 seconds) no annoying noises are to be expected.

PBTL_-2R-11,83dBFS-Plopp-Check.PNG


Multitone shows a clean overall range of 16 ENOB.

PBTL_-2R-11,83dBFS-Multitone.png


Linearity. Good!

PBTL_-2R-11,83dBFS-Linearity.png


Phase. Nothing to see here!

PBTL_-2R-11,83dBFS-Phase.PNG



The latency is ok (ca. 5.8 m)

PBTL_-2R-11,83dBFS-Latency.PNG


Dynamic range

PBTL_-2R-11,83dBFS-DynamicRange.png


Frequency response is clean. Not the highly zoom axis.

PBTL_-2R-11,83dBFS-Freq-resp.png


Line-Out Measurements

The flexibility of the unit is highly enhanced through the addition of a line-out mode. In line-out mode, the outputs are DAC only and do not provide power.

The manual describes this mode as "balanced output". My tests did not prove that. I think they meant "differential output". The 5 V rms out make this a good universal output.

L-O-dash.PNG


THD Ratio. Interesting spikes. I have no idea where they come from. Should be absolutely no problem though.

L-O-THDRatioOverFreq.png


SMPTE IMD. Not awesome for 2022, but very ok for automotive.

L-O-SMPTE.png


The manual warns of plop sounds during some switch on/off cycles. I had no problems whatsoever.

L-O-plopp.png


With the AES17 filter removed, the spectrum above 20 kHz looks fine. Filtering is just a bit lazy I would say.

L-O-noiseSpectrumFilerAttenuation.png


Multitone is as clean as the amped channel mode. 16+ ENOB.

L-O-multiTone.PNG


Linearity is a bit off.

L-O-linearity.png


The Jitter spectrum is surprisingly clean.

L-O-Jitter.png


Frequency response is flat. Note the highly zoomed axis.

L-O-freqResp.png


Dynamic range is lightly higher in line-out mode.

L-O-dynamicRange.PNG


Delay is the same for line-out as PBTL. Makes installation life easy.

L-O-delay.PNG




Software

Software interface is typical miniDSP and easy to use. The connection to the unit worked flawless and did not interrupt during the tuning process.

peq.png


What features do I miss in the DSP?

- Speed control input via CAN from OBD2 to have speed adaptive volume settings
- Phase control in degrees as advanced option in output section
- “Solo” in the output section
- Limiter in the output section
- Loudness curve coupled to volume of amp set in remote control
- Input section EQs

Verdict

Great box, flexible, good price, good performance for automotive. Like it!
 

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ytabouret

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Hello

« Verdict
Great box, flexible, good price, good performance for automotive. Like it! »

Thank you very much for this review.



I will be very curious to have comparison measurements with a Hifi amp at home.

What would be the weak points for this use?



I am very happy to use it at home, powered by a car battery, in multi-amplification of a pair of 3-way speakers.

I use the USB input to read my FLAC from the PC, the TOSLINK input to play my FLAC from a multiroom box controlled by my smartphone, or to listen to the audio of my projector.

I really appreciate the DIRAC LIVE delivered with which allows to align the channels and correct the acoustics of my room.

On this subject I recommend Sonnie's excellent guide:

https://www.avnirvana.com/threads/minidsp-c-dsp-8x12-dl-tuning-step-by-step-guide.7261/

Regards

ytabouret
 
OP
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I see nothing wrong with your use case. I thought about it, too, but I am way to lazy to charge the batteries. :) The DACs are fine, but are not up to par with more higher end models. So you loose some transparency here. But thinking about the automotive use case and the price/cost ratio, I think it is a cool box. Dirac Live has not been tested. I know myself how to use EQs ;)
 

changster

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Very nice review, thank you. I'm much more into car audio than home audio because it is way more fun to get it right. The environment is way more challenging and you have to do a lot more.

I really hope ASR can get more car audio equipment reviews, especially in amps and DSPs, and maybe even drive units.
 

Berwhale

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Great review, thanks for sharing.
 
OP
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I am a Mac guy. Havent had a PC PSU in ages. :)

How much power can you pull through the RCA plug? I once unintentionally had 400W on a TRS. Smelled very funny, but not for long.
 

Larudakote

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I am a Mac guy. Havent had a PC PSU in ages
Same.

How much power can you pull through the RCA plug?
Here is my choice for my work desktop because I listen low level, very near field.
But if you use GX16 plug and a good wire, you can pull at least 15A. A PC or Mac PSU can drive much more. I can post photo about my last Diy (little Lenovo PSU).
 

amirm

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It is quite a remarkable box that seems to fly under the radar.
Looks like your excellent review also flew under the radar as I just noticed it. :) Great work. Promoting to home page.
 

amirm

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I really hope ASR can get more car audio equipment reviews, especially in amps and DSPs, and maybe even drive units.
I have an amp here. I tend to get more of them when I review one of them as people don't think of us as such a destination.
 
OP
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Same.


Here is my choice for my work desktop because I listen low level, very near field.
But if you use GX16 plug and a good wire, you can pull at least 15A. A PC or Mac PSU can drive much more. I can post photo about my last Diy (little Lenovo PSU).
Ah, now I understand! I thought about the clunky ATX switch-mode power supplies with 64 cables dangling out of it. Using an old laptop PSU is safe and a good way of upcycling. I tried that once with a Merus eval board. Was not very successful.
 

Larudakote

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Ah, now I understand!I thought about the clunky ATX [...]
It is! Thanks to 12V output:
black wire = ground (high current)
yellow wire = 12V (high current)
red wire = 5V (high current)
blue = -12V (low current)
green = start
Just have to connect green wire to ground, add a switch and GX16 plug.
It is very simple and safe: a little bit drilling and soldering (some painting if visible).

Edit: here is a photo from my modified TXF PSU, very compact, exctracted from a Lenovo mini tour. I replaced the fan by a low profile, managed by the PSU so totaly silent. You can buy TFX for less than $35.

PXL_20220511_215449082.jpg


Using an old laptop PSU is safe and a good way of upcycling
It's not! Because laptop needs 19V output.
Car amp needs 12 to 14,8V (max car battery voltage).
 
Last edited:

ytabouret

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I see nothing wrong with your use case. I thought about it, too, but I am way to lazy to charge the batteries. :) The DACs are fine, but are not up to par with more higher end models. So you loose some transparency here. But thinking about the automotive use case and the price/cost ratio, I think it is a cool box. Dirac Live has not been tested. I know myself how to use EQs ;)
Hello,
Your study compares the output signal to the signal entered in USB or Toslink. It's correct ?
This signal passes through an internal mill which includes a DAC that cannot be bypassed, and optionally a DSP and Dirac (if configured by a computer).
So your conclusion includes at least the DAC or I didn't understand?
If not, it would be great to complete the study by measuring the quality of this DAC.
Is it possible ?
Cordially,
 

ytabouret

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Just find a PC PSU. It works fine
I use car amplifier for decade (Audison). TV system and my desktop, connected at DIY HiFi loudspeakers.
This last setup is connected to my PC, where I extracted 12V trough RCA plug.
What voltage converter could compete with a lead acid car battery?

1) Total absence of electronic noise

2) Huge energy reserve to serve the slew-rate (Q=CU example : 50 Ah with 12V = 15.10exp9 μF)

3) Almost zero internal resistance.

It just needs to be permanently connected to an intelligent charger that takes care of maintaining its optimal level.
 
OP
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Hello,
Your study compares the output signal to the signal entered in USB or Toslink. It's correct ?
This signal passes through an internal mill which includes a DAC that cannot be bypassed, and optionally a DSP and Dirac (if configured by a computer).
So your conclusion includes at least the DAC or I didn't understand?
If not, it would be great to complete the study by measuring the quality of this DAC.
Is it possible ?
Cordially,
I measured the output of the amplifier in all cases via the TOSLINK in. Every output can be individually configured to BTL (40Wrms), Parallel BTL (80Wrms) and Line-Out mode (5Vrms, DAC only). Every case has been measured. If you are interested in the quality of the DAC only, have a look at the line-out data.
 

ytabouret

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I measured the output of the amplifier in all cases via the TOSLINK in. Every output can be individually configured to BTL (40Wrms), Parallel BTL (80Wrms) and Line-Out mode (5Vrms, DAC only). Every case has been measured. If you are interested in the quality of the DAC only, have a look at the line-out data.
I reacted to your answer: “The DACs are fine, but are not up to par with more higher end models. So you loose some transparency here. »
I was just wondering how your study assessed the quality of the DAC, and if not then why this statement?
 

Larudakote

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What voltage converter could compete with a lead acid car battery?
Fortunately I was never concerned with WAF (my darling is so cool!) so I could do that, but...

It just needs to be permanently connected to an intelligent charger that takes care of maintaining its optimal level.
... what is influence of this charger to your audio system? Because it's connected to your system (via battery plug).

So, what is the difference between an ATX/TFX PSU and your battery + charger?
Edit: concerning #1 "Total absence of electronic noise"

I see two reasons (plus WAF for some people) to avoid your choice:
  1. saving huge space taken up by a lead acid battery
    we could talk about powerful and much smaller Li-ion (3S 11.1V or 4S 14.8V) but the charger is much more complex and probably noisy
  2. saving the planet and avoid lead acid battery ;) (Li-ion is not really better)
 
Last edited:

ytabouret

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Fortunately I was never concerned with WAF (my darling is so cool!) so I could do that, but...


... what is influence of this charger to your audio system? Because it's connected to your system (via battery plug).

So, what is the difference between an ATX/TFX PSU and your battery + charger?
Edit: concerning #1 "Total absence of electronic noise"

I see two reasons (plus WAF for some people) to avoid your choice:
  1. saving huge space taken up by a lead acid battery
    we could talk about powerful and much smaller Li-ion (3S 11.1V or 4S 14.8V) but the charger is much more complex and probably noisy
  2. saving the planet and avoid lead acid battery ;) (Li-ion is not really better)
The charger is permanently connected to the battery, but I have the choice of only powering it when not listening. I have sufficient autonomy with 80Ah for a flow <3A.

I admit that I am not able to hear a difference when listening to the battery being charged or not.

About the volume, the weight of WAF, it is not a subject for me because the system is hidden in a bin under my sofa…;)

There remains the advantage of the enormous energy available instantly.

As far as pollution is concerned :facepalm:, it is true that we can do better, the next sodium-ion technology is promising.
 
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