miniDSP nanoAVR HD HDMI Audio Processor Review
nanoAVR HD MSRP: $249
Available From miniDSP
by Wayne Myers
The miniDSP nanoAVR HD is a recent introduction from the company that has brought us an entire family of audio DSP products in recent years. I was intrigued by the concept of the nanoAVR as soon as I heard about it, and was anxious to have a chance to review a unit.
When it first came out, it was called the nanoAVR 8x8. Now miniDSP is calling it the nanoAVR HD. And the prices just dropped from the initial $299 to $249.
As the name suggests, the unit is very small, a mere 1.22 x 6.34 x 7.87 inches in a sturdy metal chassis. The product puts its focus on the heart of AVR communication, the HDMI interface. There are two HDMI inputs and a single HDMI output. That is the grand total of signal I/O for the nanoAVR. There is a USB connector and an Ethernet connector, for connection with a configuration control computer, Windows-based. Once configuration is complete, the nanoAVR can run stand-alone if desired, with one of four saved configurations selected from the front panel. The front panel is ultra-simple, a single push button and eight indicator LEDs, a group of four showing the selected configuration and a second group of four showing selected input and unit status.
The nanoAVR processes only the audio portion of the HDMI input bus selected. There is no video processing, and there is no Dolby or DTS processing, so audio input and output is in PCM format, up to 24 bits at up to 216 k-bits-per-second. Internal processing runs at 96 kHz, with 32-bit internal processing.
Two software plugins are available for the nanoAVR. Both support a full complement of input and output processing options with any-to-any selectability of the 8 input and output lines per HDMI bus. One of the plugins includes LFE / bass management capability.
The nanoAVR comes with a USB cable, an Ethernet cable, an HDMI cable, and a power supply.
nanoAVR HD Product Datasheet
nanoAVR HD User Manual
nanoAVR HD Plug-in Datasheet
That nanoAVR user interface is very well thought out and extremely intuitive. The experimenter who hates to have to open up the user manual will probably get by just fine by poking around and will quickly see how everything fits together. On the other hand, the documentation is also very well-written and easy to follow.
There is always more than one way to navigate from Point A to Point B. On numerous occasions when contemplating a leap from one part of the interface to another, I found myself thinking how handy it would be to get there "this way," would click on a control, imagining it to be a super short-cut, and on every occasion someone had thought it all out ahead of time and that shortcut worked. Think in terms of the minimum possible number of mouse-clicks to get from Point A to Point B, give it a try, and it is already implemented for you. This is the level of attention to detail in design and implementation that makes a product like the nanoAVR a real joy to work with.
The simplicity of the product forces you to think ahead how you are going to listen to the changes you are making as you program the nanoAVR. There is no way to get audio directly out of the unit, it must be followed by an HDMI-empowered processor of some sort to get the individual audio signals where you want them to go.
I listened carefully while making all kinds of changes, including from configuration to configuration, and in no case did I ever hear any kind of pop or click or glitch. Most transitions were instantaneous or very near so, but even changing from one configuration to another where there was a short silent pause, there was no sign of glitching.
The little nanoAVR is quite simply a powerhouse of first-rate audio processing capability, fronted by a pro-grade graphical user interface.
Configuration Implementation Test 1
After familiarizing myself with the NanoAVR, I decided to go through the process of implementing a couple of unique configurations to see how long it would take and if any unexpected results might turn up along the way.
The first was a 2-channel 3-way crossover with a single sub channel with two independently-EQable outputs. As previously mentioned, the only way to hear the changes being made is to run through an HDMI-capable AVR of some sort. Not wanting to subject unprotected speaker drivers to unruly signal changes, you would want to disconnect them from your AVR outputs while doing this, for safety.
Here is where a small pair of full-range speakers come in handy to attach to the outputs being worked on. I also made use of an HDMI-to-Audio adapter, a $30 unit, any number of which are readily available from internet sources. If using one of these, remember that it only gives you the left and right main outputs, and the output is only active when a stereo signal is running. A handy nanoAVR user interface feature might be the addition of a solo bus where the output bus under test or being worked on could be soloed to the left or right main output for easy speaker or headphone monitoring.
The interface is broken up into three blocks, first the LFE and bass management, then the switching matrix, and then the outputs. It took me less than a minute to select the front-left and front-right inputs to go to the LFE management bus and turn off the rest of the inputs. Selection is a single mouse-click to toggle on or off. Or a right-click opens up a volume slider with the option of direct numeric input. Each of the inputs also has an optional low-pass filter. I left these at their 80 Hz defaults.
At each available filtering point of the interface, there is a complete list of filter types and slopes available. Crossover sections have an advanced mode that allows for bi-quad filters as well.
The main routing matrix, where I spent about another minute of programming time, allows for any-to-any routing between inputs and outputs, again with the option of simple on-off toggling or treating each point as a variable-level mix point. The matrix is 8 x 8 with a ninth internal channel handling the LFE mix, which has its own 8 x 1 x 8 routing matrix, effectively making the design a 9 x 8 configuration.
I selected front-left and front-right to be the main low-frequency outputs, sub out and center out as sub outputs from the LFE channel, SL and SR as mid band outputs, and RL and RR outs as tweeter band outputs. The matrix points for the tweeter bands were set at -3db to compensate for a sensitivity difference.
There were two very nit-picky interface features that I wished for. One was a return-to-zero feature that would allow a double click on a volume slider or control to reset it to unity (0 dB) gain. The other wish was that if a gain level for a given matrix point had been changed to a non-zero gain value, that it would be represented by a different shade of gray than "0 dB" or "Off," so it would be easy to find when switched "Off." But these were wish list items on an otherwise flawless user interface that went above and beyond expectations at almost every turn.
The most time was spent on the 3rd portion of the interface, the output programming, where the crossovers were set up. The user will be thinking about each output as a frequency band and the high- and low-pass filter points for that band. Available filter types are Butterworth, Linkwitz-Riley, and Bessel, with selectable slopes.
With the crossover configuration window open, one can see both the graphical representation of the band being modified, and the numeric input and descriptions of the low- and high-pass cut-offs. It is easy to switch between channels and any channel can be linked to any other in pairs to cut the programming time in half. Each of the subwoofer outputs had a couple of dips added to the parametric EQ section to control room resonances. These also could be linked together if desired. Setting up the crossover pairs, frequency bands, and sub EQ took less than 20 minutes, including experimenting time.
With that done, the nanoAVR configuration was in place. All changes take place in real time within the nanoAVR unit when made from the GUI on the controlling computer.
Each track has both a bar graph and a numeric representation of the RMS signal value at its output. This helps you see at a glance where you have signals routed, and is needed when any EQ with boosted frequencies is in use, and when setting up optional channel compression. I would have liked to have seen a peak-reading meter, but they can eat up a lot of DSP power.
Master output gain and input selection are also selectable, plus a number of functions can be programmed into popular remotes, including output gain.
Configuration Implementation Test 2
The second configuration project was to create, with a base 7.1 surround set-up, a custom headphone mix for a hard-of-hearing listener, sacrificing the RL out and RR out channels to that headphone mix output.
The LFE management remained unchanged from its default settings. The routing matrix took a little more thought, I chose to reroute the rear left and rear right outs to be mixed with the surround left and surround right outs with zero attenuation. That way a 5.1 source would play correctly, and the few less-common 7.1 titles would play almost correctly. Each of the new headphone mix outputs received its signal from Front channels, a -3db Center signal, and the surround and rear signals at full strength. LFE signal was not included, as that would only be a distraction to a hearing- disabled listener trying to follow dialog.
The only output channel changes were the enabling of compression. There is one compressor per output channel, with basic but adequate threshold, ratio, attack time, and release time controls. Some final output gain was added to compensate for compression, and the configuration was complete.
Configuration Implementation Test 3
My final experiment was to see how easy it would be to import filter values from Room EQ Wizard (REW) using a previously measured room response. REW allows for selection of several miniDSP platforms, including the nanoAVR. REW's designer, John Mulcahy, has worked with the miniDSP team to implement filter selection and file format to be compatible. Only 10 bands per channel of parametric equalization are available. Being one who prefers to avoid EQ overkill, I believe this to be plenty for most applications.
Going through REW's processs of determining correction filter values, once the needed filters have been defined, they are then manually saved to a file. Then that file is simply manually imported into the nanoAVR parametric EQ configuration screen and the nanoAVR settings now reflect the values that were determined by REW. The process is clearly documented and easy to follow, and took me 10 minutes, including the time reading the instructions.
The nanoAVR delivered first-rate audio performance through all of my tests and experiments. Its 24/96 I/O depth and speed, combined with 32-bit internal processing, will satisfy demanding listeners.
I took on the nanoAVR review with high expectations, and those expectations were satisfied at every turn. The tiny unit is packed with audio processing capability, has an outstanding user interface, and is sure to delight experimenters and tweakers with special audio needs for their surround system. The nanoAVR HD is a dynamite offering from the miniDSP team, and gets my full recommendation, along with my challenge to just TRY to work with one without having a fun time!