miniDSP 4x10 HD Review – the good and bad

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miniDSP 4x10 HD Review

This is DIY Geezer's comprehensive review of miniDSP 4x10 HD, a superb and flexible all-in-one DSP solution. The miniDSP 4x10 HD is a real chameleon, being able to function as a remote controlled preamplifier, a digital active crossover network, parametric equalizer for bass management, loudspeaker correction and room correction and being a digital to analog converter.

I personally own two miniDSP 4x10 HD's and use both on a daily basis so it may not come as a surprise that I think they are worth the money, but it may not be suitable for you and in this review you will get the good, the bad and the ugly.

The ins and outs of miniDSP 4x10 HD

miniDSP 4x10 HD is 1U and come with removable rack ears if you want a more traditional hifi look as opposed to mount it in a standard 19" rack.

miniDSP 4x10 HD front panel

On the front panel you have an infrared sensor for an off the shelf remote control. The unit can learn different commands for changing source, set the volume or load one of the four configuration settings for most remote controls. The front also has a multi-function knob which can be used for the same purpose by being rotated or clicked. Unfortunately, there's no display or led lights to indicate volume or signal levels, but there are eight white leds which will indicate which source is used and what configuration setting you're set to.

miniDSP 4x10 HD rear panel
Click to see high resolution image of miniDSP 4x10 HD's rear panel in a new window.

The rear panel is used for both miniDSP 10x10 HD and 4x10 HD, so that's why you see a lot of blank panels there, but going from left to right we find the VDC input for the standard laptop like power brick switch mode power supply that come with the device.

For analog input signals you have a pair of RCA inputs for single ended and a pair of Phoenix input terminals for balanced connections.

Phoenix terminal connector used by miniDSP

To use the Phoenix terminals you will need to connect your signal cables to the connector which resemble a terminal block. No soldering is involved, you simply use a flat head screw driver. The inputs are on the same channels, meaning you have to choose one over the other for a maximum of one analog input source. If you need more input channels, you may want to take a look at the miniDSP 10x10 HD instead. It's essentially the same as the 4x10 HD, but it has more input channels.

For the analog outputs you have eight RCA outputs for single ended audio and eight Phoenix outputs for balanced audio. Both single ended and balanced outputs are live at the same time and it's recommended that you choose one or the other.

Digital inputs are coaxial SPDIF, optical Toslink and AES/EBU. Digital outputs are the same, and all inputs and outputs support a maximum of two channels.

The USB 2.0 connector is not an audio interface, but strictly for controlling the unit by using a plugin.

The Phoenix terminals are easy, but time consuming to work with, especially if you tin all the wires, use heat shrink tubing etc. to make a semi decent result. The only benefit I can see with the Phoenix terminals is the cost advantage and that they enable this many channels in a 1U chassis, but I would gladly give up space and pay a few extra dollars for a 2U chassis with XLR inputs and outputs.

Peeking inside miniDSP 4x10 HD digital signal processor

Inside of miniDSP 4x10 HD
High res photo to study the inside of miniDSP 4x10 HD, and one with some comments on the gain jumpers and DIP switches inside 4x10 HD.

By popping the lid off, we're greeted with the nicely laid out internals of miniDSP 4x10 HD. To optimize the gain structure you may need to change some jumpers or set some DIP switches inside the unit.

Gain structure flexibility of 4x10 HD

This adds a great level of flexibility, as you can change the input sensitivity of the 4x10 HD between 0.9Vrms and 2Vrms on the RCA inputs, while the balanced inputs are constant at 8Vrms maximum input and can't be changed.

The (red sore thumb in the middle of the PCB is the) internal DIP switches for each channel which will change the outputs between 0.9Vrms and 2Vrms for the RCA connectors and 4Vrms and 8Vrms for the balanced Phoenix terminals. You can also connect RCA to the Phoenix terminals by shorting cold (-) and GND (S) for up to 4Vrms through RCA.

miniDSP 4x10 HD Gain structure table
  Unbalanced Output (RCA) Unbalanced Output (Phoenix) Balanced Output (Phoenix)
  Setting 0.9 V 2 V 2 V 4 V 4 V 8 V
Unbalanced Input 0.9 V 0 dB 6 dB 6 dB 12 dB 12 dB 18 dB
2 V -6 dB 0 dB 0 dB 6 dB 6 dB 12 dB
Balanced Input 8 V -18 dB -12 dB -12 dB -6 dB -6 dB 0 dB

An optimal gain structure will yield the lowest noise floor and maximum headroom, and the goal is that the input voltage from your source does not clip the 4x10 HD, while miniDSP's maximum output voltage does not clip your power amplifiers. This gain flexibility means that miniDSP 4x10 HD will fit almost any possible application out there. I just wish they had placed the DIP switches and jumpers on the rear panel of the unit, as it's a pain to pull the whole thing out of the rack and unscrew the top lid whenever I need to change something.

For further insights into miniDSP 4x10 HD's specifications, you may want to peek inside the specification sheet. The miniDSP 4x10 HD manual (PDF) is also very detailed and will answer a lot of common questions, so you may want to flip through it to have a more in depth look at the product features.

miniDSP 4x10 HD DAC

For the technically inclined the who wonder about the miniDSP 4x10 HD DAC chip, the answer is an ADAU1445 DSP chip in combination with the Cirrus CS42528 DAC chip and the opamps in the output stage are NJM2068.

miniDSP 4x10 HD DAC chip, Analog Devices ADAU1445

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Do I think the DAC quality is important? Absolutely, but here's the thing. I used to be fiercely focused on the DAC. I've owned professional DAC's such as the Mytek DIGITAL 192 STEREO DSD DAC, Lavry DA11 and Grace Design m903, high end Hi-Fi DAC's such as Auralic MX+ and DAC's such as the cheap, but well renowned Objective2 DAC and many, many others.

Before I ventured into active loudspeaker systems and using DSP to optimize the sound quality of my system, the DAC was one of the main variables I could tinker with and rolling DAC's and opamps were a big part of the «audiophile» hobby. If the highs were a bit harsh I'd read tons of reviews trying to find a warmer DAC, found one and purchased it and but found that the warmer DAC had too little details, so I went out and looked for another one with more warmth and details, but got one with less bass impact and ... Well, you get the idea.

The point of telling you this is that you may be in that situation today. You may be concerned about the 4x10 HD's DAC quality, because that's what you normally consider an important contributor the overall sound quality of your audio system, and yes, you are right. A good DAC is important, but being able to do bass management to get rid of huge peaks in your frequency response, being able to time align speakers or even individual drivers and maybe even take it a step further and run them actively is so much more important.

We often hear that a system is no stronger than its weakest link; this is true, and this is why we must make sure our weakest link is optimized, and our weakest link often the loudspeaker, and the interaction between the room, the loudspeakers and subwoofers.

With DSP in your system you will be able to remove those pesky bass peaks, get even levels across all frequencies, adjust the tonal balance to suit your subjective preferences and time align the speakers to create better holographic imaging and a wider soundstage with better pin pointing. These are the things we should focus on, and when we have these things right, we can start focusing on the DAC to squeeze the last ounces of performance out of our music.

With that essay written, is the DAC quality of miniDSP 4x10 HD any good? The DAC is not high end, but it hits way above it's price range and you get eight channels! I wish I could afford a stack of MyTEK 192 DAC's or a professional DAC such as Lynx Aurora 16 and do all the processing before feeding those DA converters, but again, that's just icing on the cake and the sound quality in my system has never been as good as it is now, despite the lack of high end digital to analog converters.

If you have a DAC you want to use instead of miniDSP two channels of your system, like the top end, midrange or your left and right speakers you can use the digital outputs and route two channels to that, but the channels will not have delay with the 96 kHz plugin which has the best sound quality, and the audio will be up sampled to 96 kHz before it reaches the DAC, and can't be set to pass through. You can set xover filters and parametric equalization filters however. For example, this will be ideal for integrating multi way subwoofer.

HiFi system with miniDSP 4x10 HD

This picture is from my brother's beautiful living room. You can see that he has a McIntosh C48 preamplifier (with integrated DAC) driving a meaty McIntosh MC602 power amplifier. He was convinced about getting minIDSP 4x10 HD after hearing it in my system and seeing how it worked, but he didn't want to mess up the aesthetics of his own system so he hid it from sight.

miniDSP 4x10 HD Hi-Fi room correction

He is using miniDSP 4x10 HD for room correction, time aligning his speakers and subwoofers and as a means to shift the tonal balance of his system somewhat. He has never had the level of performance that he has today and miniDSP did what no other DAC could do.

miniDSP 4x10 HD noise

As an extension of the DAC quality we need to talk about the noise floor of miniDSP 4x10 HD. A low noise floor will yield a black background and improve the micro details and listening enjoyment in silent rooms. A silent system is incredibly important if high fidelity is your goal.

To achieve the lowest possible noise floor with miniDSP 4x10 HD you should connect your source digitally. If you connect an analog source, the unit will first convert the analog signal into a digital signal, then do all the digital signal processing and convert it back into analog to drive your power amplifiers. The ADC or analog to digital conversion will add some noise to the signal.

Unless you have a ground loop in your system the miniDSP 4x10 HD noise will not be a serious problem with average sensitivity speakers and an optimized gain structure. There will be some slight hiss, but only audible when you put your ear close to the tweeter.

Line level attenuators for reducing noise in audio systems

If you want to get rid of that hiss too, you can use some off the shelf line level attenuators between miniDSP 4x10 and your power amplifiers. Line level attenuators are small XLR and RCA «dongles» which will attenuate the analog signal and help you get rid of noise. How many dB you need to attenuate depends on the sensitivity of your system. The cost of using line level attenuators is loss of headroom, but with the flexible gain structure of miniDSP 4x10 HD you will be able to regain most if not all of that headroom in many applications.

How about miniDSP 4x10 HD in high sensitivity systems? Well, I'm using miniDSP 4x10 HD in the worst possible arrangement. My source is analog, so I get noise because of the extra AD conversion by connecting the source through the analog interface. Furthermore, I use high sensitivity horns and the level of hiss in this application is unbearable without the line level attenuators, but with them the system is really magical, and my attenuators are just cheap off the shelf ones.

Real time adjustments of filters and multiple configurations

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Some DSP products require you to make filters locally and then upload them to the DSP device before they will take effect. This makes the adjustment process more cumbersome and it's a pain to make quick and dirty adjustments to the tonal balance or if you have some idea of a problem and want to correct for it before you bring out the measurement equipment to optimize something.

One excellent selling point of the mini-DSP 4x10 HD digital signal processing units is that they allow real time adjustments. This is amazing as you can make small adjustments and subjectively judge the results as you go. You can also change all other settings, such as the high-pass, low-pass, PEQ filters or delays. It's almost priceless having live adjustments.

What makes it even better is that you can store up to four different settings at any given time, this enable you to create four similar settings, but change some smaller variables and switch between them. Fantastic!

But with this kind of flexibility you must also be careful. For example if you run your tweeter unprotected and turn off the low pass filter by mistake, it will be a very costly mistake. Whenever I change XO settings I mute everything and if I want to compare different XO filters subjectively I have one in each config and switch between them to make subjective assessments.

Control plugin GUI and sound quality

You can choose between two plugins for miniDSP 4x10 HD. The 48 kHz plugin with more delay and fairly stable filters below 30 Hz or the 96 kHz plugins which offer superior sound quality but less delay and less stable filters below 30 Hz. The filter issue and how to work around it is covered in the next section.

I've seen people call the miniDSP 4x10 HD sound quality veiled, and I suspect statements like that may be a result of several factors. Maybe they used the 48 kHz plugin, maybe they didn't optimize the gain structure and had noise issues or maybe they had set some poorly implemented filters  – or maybe they just have golden ears and I don't, lol.

One thing I strongly oppose is that miniDSP's decision to charge $10 for each of their plugins. Sure there are development costs, but I can't imagine Behringer, Monacor, DEQX, Groundsound, Trinnov, Hypex or anyone else selling standalone DSP devices charging extra for the software needed to operate them. These things should be factored into the price of the unit to make the customer experience smoother. I have purchased a number of plugins myself, and it's not so much the cost, but the inconvenience and annoyance of having to pay because I want to control the unit I've purchased from them. But I guess this is the era of appstores and quick micro payments and it's just me getting old.

Here's a video tutorial using the 96 kHz plugin GUI to control miniDSP 4x10 HD.

(video in production)

As you can see, very flexible, and regarding the advanced biquad filters, you can use the biquad spreadsheet available through miniDSP's website.

miniDSP 4x10 HD measurements

The following measurements were made with a calibrated Tascam US-366 audio interface and Room EQ Wizard. The Tascam ran in 192 kHz operation over USB using bit perfect ASIO. Furthermore, the Tascam was connected to miniDSP 4x10 HD by analog input and output channel 1 over single ended RCA.

miniDSP offer two separate plugins which both work for the unit, the 96 kHz (aka 2x8) plugin which offer better overall sound quality, but have quite unstable low frequency filters due to arithmetic rounding errors, and the 48 kHz plugin which have lower sound quality and sound more veiled, but has better low frequency filter stability.

miniDSP 4x10 HD low frequency filter stability on the 96 kHz plugin

miniDSP 4x10 HD 96 kHz all high pass filters, instability measurements

These are all the stock filters at set at 10 Hz and 3 kHz. The behavior is normal at 3 kHz, but as you approach the minimum limit of 10 Hz you get overshoots upwards of +13dB @ ~12 Hz for the BW 48dB/Oct filters.

As you can see you need to be very careful with the high-pass filters in the low frequencies with the 96 kHz plugin as they overshoot a lot and this can cause serious harm to a subwoofer and will be very audible. The PEQ filters are also unstable, so if you are going to do anything below 30 Hz, use the SUB_EQ filter type as it offers better stability.

miniDSP 4x10 HD 96 kHz BW 48 dB/oct, instability measured with incremental steps from 10 to 100 Hz

96kHz plugin, BW 48dB/Oct high-pass filter @ {10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100} Hz showing you how the instability correlates with frequency.

miniDSP 4x10 HD low frequency filter stability on 48 kHz plugin

miniDSP 4x10 HD 48 kHz all high pass filters, instability measurements

The 48 kHz plugin (aka 8x8 plugin) is more stable. The maximum overshoot is around +3 dB at circa 12 Hz and this is not that bad, but use the SUB_EQ filter type below 30 Hz.

miniDSP 4x10 HD 96 kHz BW 48 dB/oct, instability measured with incremental steps from 10 to 100 Hz

48 kHz plugin, BW 48dB/Oct high-pass filter at {10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100} Hz showing you the correlation between overshoot and frequency.

Comments miniDSP 4x10 HD low frequency instability

It was nyt over in the minidsp forums who found these anomalies, and you can read all about it there. The instability of the 96 kHz plugin is quite severe, so don't use a steep high-pass filter to protect your DIY sub with that plugin as it may have the opposite effect. Use shallow filters instead, especially as you go down in frequency.

Both biquad filters and parametric EQ filters are also affected, so use the SUB_EQ filter when you do anything below 30 Hz.

miniDSP are aware of these issues, but the alternative is to disable filters below a given frequency all together and that's not very helpful, so it's better to be aware of these limitations and work around them instead.

miniDSP 4x10 HD not built to scale

This will not apply to a lot of people but if you intend to use more than one miniDSP device in your audio system you should know that the implementation of the control mechanism is not scalable. For example, you can't have more than one miniDSP device connected to your computer at the same time. This is because the control plugin will not know which device you are trying to connect to, synchronize with and control. This is an annoyance as you have to connect and disconnect each device every time you need to make a change.

To make matters worse, the settings you set will be stored in the plugins' local memory on your computer, and every time you connect it to another device than the last one connected it will want to synchronize the new device with the settings from the last connected unit or restore the new unit back to factory settings.

This poor implementation means that you can't have two devices connected at the same time and make real time adjustments. It also means that you will need to install the same plugin twice and be really careful which plugin you sync with each device every time you make a change.

Solution to the scaling issue

This is most likely a software issue with the control plugins which miniDSP can fix since the plugins are able to read out the serial number of the miniDSP device connected.

It would be better if the plugin first looked for all compatible devices connected to a computer, differentiated between them based on their serial numbers and enabled the user to give a custom name to each of the devices. The name and settings for each separate device would be stored locally by the plugin and kept separate from each other through the serial number.

miniDSP 4x10 HD review conclusion

miniDSP 4x10 HD is a bargain at the asking price, and it's a great starting point for people wanting to venture into the domain of digital signal processing. It has a lot of flexibility as we have seen, and the company stand behind their product and offer good after sale service (I've witnessed that first hand).

Pros & Cons of miniDSP 4x10 HD
Pros Cons
Real time adjustments No display
Affordable No audio over USB
Easy to use Gain switches should be accessible from the outside
Flexible gain structure Phoenix terminals instead of XLR inputs
Many pre set filters Should have more delay than 9 and 15ms
Biquad filter implementation Does not scale well if you want multiple units
Smooth REW integration Plugins should be free
Good DAC quality Low frequency filter instability
Eight analog output channels Some hiss, especially with highly sensitive speakers
Two digital output channels No on and off switch
Four separate configurations  

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There are obviously some flaws, but it delivers where it counts, and that's on flexibility, the number of channels, the audio quality and making DSP affordable and available to a larger audience. Not a single company has done this better than miniDSP, and they have contributed a lot to the REWolution with their affordable UMIK-1 measurement microphone and their vast array of functional DSP devices.

If the 4x10 HD is not suitable for you, you should check out their alternatives, as miniDSP has been churning out new products hand over fist. I hope they revisit some of their earlier successes and improve upon them, like a miniDSP 4x20 HD elite with XLR connectors, more delay, more filters, more channels, more of everything! :)

miniDSP has been a game changer to my personal development in our great hobby, and because of everything I have learned and being able to adopt with the miniDSP 4x10 HD I have never had better sound quality than I have today, so thank you, miniDSP!

Join the dark side; get DSP into your system. :D

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Discussion on miniDSP 4x10 HD Review – the good and bad

Very good article, probably one of the best review of minidsp I've seen on the web. You touched a number of core issues that were on my "ask-a-question" agenda!

Gain structure is the main issue, I agree. However it is very difficult to understand for newbies/nontech people I must confess that although I am not really an inexperienced sometime I get easily confused on how to proceed for optimizing the gain structure.

I understood that you listen to your analog source as a primary source. This is what prevent me from using a DSP engine. My music collection is 50% analog and 50% digital. How do you find the AD conversion?

Best Wishes and thanks again for this
Pietro

DIYGeezer's picture
Hello, and thank you for the kind words. I did put quite a bit of effort into this review and it's based on long time use.

I agree that gain structure optimization is confusing and if not matched properly you will lose headroom or get a worse noise floor than you would need to. The good thing about miniDSP 4x10HD is the flexibility of all the settings. What you are basically looking for is to match the output voltage of miniDSP to the input sensitivity of your amplifiers, and then adjust the levels for each speaker/component so it plays equally loud to avoid imbalances.

If you want to see if DSP is something for you without spending a lot initially they've come out with a new device recently, namely the miniDSP 2x4 HD. (The HD version is superior to the non HD version, so make sure you get the HD version).

I have been very happy with the DSP even though the ADC added some noise I had to get rid off by using those passive attenuators. In my situation the benefit of DSP outweighed the cost of the extra AD conversion.

You may also want to look into Groundsound's offerings I hear that people say the vinyl magic is still there after the conversion. I do not use vinyl and have not tested the Groundsound products myself unfortunately.

hi- thanks for the review it's helpful. my question is, given the power of the miniDSP, why use in-line attenuators...why not use the miniDSP to either attenuate the overall signal or EQ the problem hiss? just curious of the advantage of the in-line hardware. many thanks

ck

DIYGeezer's picture
Hi,
I think some of the noise is coming after the digital to analog conversion (after the DSP) so digital attenuation won't have any effect. (I've tried and it didn't help).

Great article, thank-you.

What are the speakers in your brother's aesthetically sublime system, please ?

DIYGeezer's picture
Thank you, those are a pair of Consonance Barque M15 MKII. A (Chinese built) 2-way bass reflex system with a horn loaded compression driver. His subs are Velodyne DD18. The speakers sound very good.

i thing give it a go for Xonar U7 as a DAC... You can be pleasant surprised.

Thanks for publishing this. I've been going crazy trying to make a MiniDSP 4x10 work with an OpenDRC-DI; the former for a 3 way XO, the latter to linearize the phase and do room correction.
Re' LF filter stability/accuracy
Is the filter actually unstable in that it can "blow up" or just have a big peak in the frequency response where it should be rolling off smoothly?
There was some discussion of this issue in the RePhase thread on DIY audio, if I recall correctly. The idea was to modify the coefficients to get better accuracy at low frequencies.

Just wanted to say that this was a great review, but I have a couple of things you may want to take note of.

1. When terminating a Phoenix style connector, you should not tin the ends of your cables. The idea is that you want the clamping action of the connector itself to flatten down the wire and make a broader contact. If you tin your ends, the connector will not be able to do this and the result is a small contact point. Either way works, obviously, but not tinning is theoretically better.

2. I have not used the 8x8/4x10 plugins, but if they are anything like the 2x4 versions, you are able to(and should) save your setup for future synchronization. So, in your example of multiple MiniDSPs, once you setup each one save the file, then load it back into the GUI before reconnecting to the device in the future. This way the right setup will re-sync with the DSP you are working with in your system. A pain, I know, but that's the way it is.

Very good and inspiring article when you're considering minidsp or any dsp in your system. However even many subjects are covered I would like to know if you have any knowledge regarding internal clock stability (jitter) ? It is crucial that the clock is "jitter free" in the D/A conversion (also A/D). I upgraded the clock in my CD player CDA 266 Copland and it was absolutely worth doing regarding sound quality.

As all my sources are digital (WAV, FLAC), I too am very concerned about DAC quality as I will soon venture into to DSP-based multi-sub bass management and room eq, using one of these solutions
http://www.dspeaker.com/en/products/anti-mode-8033.shtml
http://www.audiovero.de/en/acouratedrc.php
http://www.roomeqwizard.com/
https://www.minidsp.com/applications/home-theater-tuning/multi-sub-optimization-with-the-ddrc-88a

But assuming that your speakers (and my which are also two way high sensitivity) have no serious group delay issues, and if our rooms have no serious resonance's above, say, 70Hz, then driver time aligning and/or room correction for the upper midbass might not be necessary (??). In which case, DAC quality may not be a factor in apparent sound quality, as DSP processing would be confined to the subwoofers. That plus merely using the DSP box to take room measurements at various locations and treating any issues acoustically.