miniDSP Harmony 8x12 Car Audio Amplifier - Review and Measurements

[radio3]

My dream is to make an all active system centered around this exact unit. Can’t wait for multichannel audio to become available for cars (amazing that it still isn’t at all outside of oem system). I spend much more time listening to music in car than I do in living room. Even bought my current car for the purpose of making a Dirac corrected multichannel system (BMW 2-series with typical BMW 4” speakers in perfect locations next to tweeters all around and in center of dash + 8” under seat woofers). Yet somehow multichannel upmixing and/or decode never arrives.

 

[Philipp Paul Klose]

My dream is to make an all active system centered around this exact unit. Can’t wait for multichannel audio to become available for cars (amazing that it still isn’t at all outside of oem system). I spend much more time listening to music in car than I do in living room. Even bought my current car for the purpose of making a Dirac corrected multichannel system (BMW 2-series with typical BMW 4” speakers in perfect locations next to tweeters all around and in center of dash + 8” under seat woofers). Yet somehow multichannel upmixing and/or decode never arrives.

Go for it! There is a lot of potential even in standard sound systems. Miltichannel will come eventually, pretty sure about that.

 

[changster]

My dream is to make an all active system centered around this exact unit. Can’t wait for multichannel audio to become available for cars (amazing that it still isn’t at all outside of oem system). I spend much more time listening to music in car than I do in living room. Even bought my current car for the purpose of making a Dirac corrected multichannel system (BMW 2-series with typical BMW 4” speakers in perfect locations next to tweeters all around and in center of dash + 8” under seat woofers). Yet somehow multichannel upmixing and/or decode never arrives.

You can get a great sounding system in your BMW with 2 channel stereo. I also have a BMW although I'm using a Zapco DSP. I have an 8x12DL as well but currently using it for a fully active setup at home.

Deaden the car, get an 8x12DL or a Helix V8/V12, replace speakers, add a sub, and most important of all tune the car.

 

[Philipp Paul Klose]

The “use-at-home“ users are more then I expected.

 

[changster]

The “use-at-home“ users are more then I expected.

Car DSP's give a lot of features, a variety of input types, a ton of channels, but unfortunately only unbalanced output.

I really hope we get to see a lot more reviews of car audio electronics and speakers.

 

[Philipp Paul Klose]

Any specific product in mind that you are interested in particularly?

 

[changster]

Any specific product in mind that you are interested in particularly?

Well the most popular DSP's/amps amongst the car audio SQ types would be Helix and Zapco products. Helix DSPs (V8, V12), Zapco HDSP-V, Zapco Z-AP line of amplifiers. I do see the JL HD amp review here from Amir which was great.

Also the most common thing people do to cars is to add a subwoofer. So I think a bunch of subwoofer reviews using the Klippel machine would be awesome. JL Audio subs for example.

I will have a bunch of stuff extra that I'm not using in my car which I can send for review, but I'm located in Taiwan so the shipping is expensive. I'm ok with that though. JL Audio 12W6v3 subwoofer, Zapco Z-1100.1 AP amp.

 

[radio3]

You can get a great sounding system in your BMW with 2 channel stereo. I also have a BMW although I'm using a Zapco DSP. I have an 8x12DL as well but currently using it for a fully active setup at home.

Deaden the car, get an 8x12DL or a Helix V8/V12, replace speakers, add a sub, and most important of all tune the car.

I know, for example those Integral Audio BMW Soundstage stereo systems apparently sound spectacular. However, I like to entertain with my car. Little parties in a way with friends, taking road trips, nights on town. That to me is where center channels and different dsp settings for diffent levels of occupation of car would be most valuable. It's not that I want pinpoint perfect sound where one person's head is. What I want most is 4 people at once to experience music like they've never heard it before all at one time (as much as possible).

Would be nice to basically have 3 settings: One with "surround sound" where everything time aligned, eq'd, level matched for driver. One for best overall for two people up front. A third for 4 passengers such that, for example, rear speakers that are in the ears aren't deafening them while front drivers want to turn the volume up.

 

[radio3]

You can get a great sounding system in your BMW with 2 channel stereo. I also have a BMW although I'm using a Zapco DSP. I have an 8x12DL as well but currently using it for a fully active setup at home.

Deaden the car, get an 8x12DL or a Helix V8/V12, replace speakers, add a sub, and most important of all tune the car.

Care to share what the rest of your components in car system are? Just curious.

 

[changster]

Care to share what the rest of your components in car system are? Just curious.

Zapco HDSP-V DSP, Zapco Z-AP amps, FIIO M17 coax into the DSP directly, Focal Utopia 8WM underseat midbass but I've cut a hole under for a true Infinite Baffle install, Scanspeak 12MU in the factory door for midrange, Focal K2 tweeter in the sail, Adire Audio Brahma X 15" sub in a sealed enclosure.

Key for a great car audio sound is installation and tuning. Check out "Pssound" on Youtube for great videos. Search his playlist for something like "What is SQ" playlist or something like that. I'm not quite there yet but I'm getting closer.

 

[Philipp Paul Klose]

Good to know. I wish I would have more time to measure and write reviews.

 

[novice]

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.

Some car amps have amazing fidelity, specifically the Italian ones (Audison, Mosconi, STEG). I'd bet your system sounded good.

Props on your DIY too, excellent work and great aesthetic.

 

[novice]

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.

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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.

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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.

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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!

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

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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.

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

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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.

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

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THD over frequency

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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.

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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.

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Multitone shows a clean overall range of 16 ENOB.

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Linearity. Good!

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Phase. Nothing to see here!

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The latency is ok (ca. 5.8 m)

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Dynamic range

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Frequency response is clean. Not the highly zoom axis.

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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.

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

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

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

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

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

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Linearity is a bit off.

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The Jitter spectrum is surprisingly clean.

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Frequency response is flat. Note the highly zoomed axis.

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Dynamic range is lightly higher in line-out mode.

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

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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.

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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!

Impressive & thorough review. Re: speed control, one of our vehicles has it (via Ford SYNC). It works as indicated but one still has to hit the volume control to talk at normal level rather than talk over it. So, Why use it at all? was my conclusion and leave it OFF.

 

[Larudakote]

Some car amps have amazing fidelity, specifically the Italian ones

Absolutely! I bought many years ago two used Audison Millenium Power 4 cheap: very impressive performance, nice built construction, good user manual, LR2 crossover for 2, 3 or 4 channels. The other one is behind a TV wall support with HiFi loudspeakers (as you can see in my portfolio).
Also powered by a dedicated HTPC, I made a remote powerfull ATX PSU for special parties If not, the HTPC shutdown when you play too loud (this is not the main goal here).

Props on your DIY too, excellent work and great aesthetic.

Thanks

 

[Philipp Paul Klose]

Impressive & thorough review. Re: speed control, one of our vehicles has it (via Ford SYNC). It works as indicated but one still has to hit the volume control to talk at normal level rather than talk over it. So, Why use it at all? was my conclusion and leave it OFF.

thanks! The volume curve in the Ford is probably undercompensating then. If the speed control is done right, it can be really joyful and transparent. But most OEMs do not use a mic to control for in-cabin noise and have only a speed depended gain.

 

[chris719]

Any specific product in mind that you are interested in particularly?

Helix / Match UP 7

I’d go miniDSP but the Helix center channel upmixer is something I want.

Excellent review btw.

 

[Philipp Paul Klose]

I would offer to review more car audio stuff, but the time to work with the Ap on fun stuff is somewhat limited.

 

[Philipp Paul Klose]

Helix / Match UP 7

I’d go miniDSP but the Helix center channel upmixer is something I want.

Excellent review btw.

the description of the center channel upmixer sounds interesting, I am tempted to reverse engineer this thing.

 

[chris719]

Zapco HDSP-V DSP, Zapco Z-AP amps, FIIO M17 coax into the DSP directly, Focal Utopia 8WM underseat midbass but I've cut a hole under for a true Infinite Baffle install, Scanspeak 12MU in the factory door for midrange, Focal K2 tweeter in the sail, Adire Audio Brahma X 15" sub in a sealed enclosure.

Key for a great car audio sound is installation and tuning. Check out "Pssound" on Youtube for great videos. Search his playlist for something like "What is SQ" playlist or something like that. I'm not quite there yet but I'm getting closer.

Wait, in what BMW can you get a Scanspeak 12MU to fit in the door? I was about to install a 11M/12M because I didn’t think anything beyond like 55mm was even worth entertaining.

 

[changster]

Wait, in what BMW can you get a Scanspeak 12MU to fit in the door? I was about to install a 11M/12M because I didn’t think anything beyond like 55mm was even worth entertaining.

2018 BMW X6M. I think it would only fit on the X5/X6/X7.