Indy Audio Labs Acurus ACT 4 AV Preamp Reviewed

Published On: June 14, 2017
Last Updated on: October 31, 2020
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Indy Audio Labs Acurus ACT 4 AV Preamp Reviewed

Dennis Burger examines the Acurus 4 from Indy Audio Labs. This 13.3-channel AV preamp supports Dolby Atmos, DTS:X, and HDMI 2.0 with HDCP 2.2.

Indy Audio Labs Acurus ACT 4 AV Preamp Reviewed

  • Dennis Burger is a native Alabamian whose passion for AV began sometime before the age of seven, when he dismantled his parents' brand new 25-inch solid-state Zenith console TV and exclaimed--to the amusement of no one except the delivery guy--that it was missing all of its vacuum tubes. He has since contributed to Home Theater Magazine, Wirecutter, Cineluxe, Electronic House, and more. His specialties include high-end audio, home theater receivers, advanced home automation, and video codecs.

Acurus-ACT-4.jpgIf you follow the AV preamp market closely, you've no doubt heard of the Acurus ACT 4 by Indy Audio Labs. When it was originally announced back in 2013, the ACT 4 was positioned as an easy-to-configure, simple-to-operate 7.1-channel home theater preamp with an elegant touchscreen UI and some serious made-in-the-USA bona fides. And then Dolby Atmos happened. And then DTS:X. After a few trips back to the drawing board (and a few missed release dates), what the company has finally released as the ACT 4 is quite unlike any surround sound preamp I've ever had the pleasure of using.

For those of you who haven't tracked its evolution in real time, the final version of the Acurus ACT 4 boasts 13.3 configurable channels of output, placing it in that new and exciting space between the capabilities of most consumer-focused Atmos/DTS:X receivers and preamps on one end and the prohibitively expensive, custom-only, 32- and 48-channel processors at the other. It's a space that will begin to fill out a bit in the coming months and years as other manufacturers introduce robust object-based processors with 16 channels of output (Emotiva's upcoming RMC-1 comes to mind, as does Trinnov's scaled-down Altitude16); but, for now, aside from Datasat's more expensive LS10, the ACT 4 ($9,499) is cutting a path into pretty unexplored territory.

That in itself would make the Acurus ACT 4 a fascinating product, especially given that it's from a company without tons of brand recognition (at least for the time being). You may remember the Acurus brand (and its sister brand, Aragon) due to its acquisition by Klipsch back in the early 2000s. Then both lines were sold to two former employees who led technology development at Klipsch, Rick Santiago and Ted Moore, and Indy Audio Labs was born.

None of that history really gives you an indication of what you're in for with the Acurus ACT 4, though. One of the main things that has been retained through every step of the preamp's development is its touchscreen interface, which provides simple, straightforward, graphical access to all of the ACT 4's various setup and configuration tools. Perhaps my favorite thing about the touchscreen UI is the way it represents the various speaker channels in a top-down manner. There's no attempt to provide an isometric overview of every conceivable speaker position all at once. Instead, speaker setup is broken into three sections: your audio bed channels, your subwoofers, and your overhead channels. You start with the beds, deselecting any speakers you won't be using from nine possibilities (the standard seven bed channels plus front widths). Next you select the number of subs (from zero to three), then the number of overheads, which can come in sets of two, three, or four (unless you selected nine bed channels, in which case you're limited to two overheads in the front, middle, or rear of the room). You also have a choice between heights or tops if you're running four overhead speakers. It's all spelled out in such a straightforward manner that there's really no misunderstanding any of it.

Once that's done, configuring delays and levels is also incredibly straightforward, although the ACT 4 doesn't allow you to simply plug in distances to each of your speakers. Delays are set in milliseconds, and the manual walks you through how to calculate these differently for ear-level and in-ceiling speakers.

Although the preamp does lack an onscreen GUI output for use with your TV, you won't have to worry about running back and forth between your seating position and the front-panel touchscreen, since the ACT 4 also includes a handy Web interface for configuration. So, as long as you have a laptop with network access or a mobile device with some browser other than Safari, you'll be able to sit in your main seat and dial in all of your speakers' pertinent settings.

The ACT 4 also lacks another feature that has become pretty standard on most every receiver and preamp these days: auto room EQ. The ACT 4 will generate pink or white noise, as well as a tone. As for frequency sweeps, you have to bring those to the table yourself. In my case, I simply pulled up the tone generator app on my iPhone, AirPlayed it to my Control4 EA-3 controller and into the ACT 4, and used my SPL meter to plot any egregious spikes in response below 300 Hz, which were easy to tame with the four bands of parametric EQ available for each channel. If that's a little more effort than you're willing to put in, the ACT 4 will also allow you to run sweeps with Room EQ Wizard, Dayton Audio's OmniMic, or other similar systems, so you can calculate your PEQ settings more easily. If even that's too much trouble for you, you might want to wait a few months--because word has it that Indy Audio Labs is cooking up its own auto room EQ, which will be added via firmware update at some point in the future.

For what it's worth, just calculating my parametric EQ adjustments on my own with a tablet of graph paper and a few hours of effort resulted in astonishingly good results. But, of course, no amount of equalization can compensate for a surround processor whose performance is lacking to begin with. Thankfully, the ACT 4 stands alongside some of the finest preamps I've auditioned here at home in terms of sound quality. The best description I can come up with is this: take the sound of a Classé SSP, sweeten it ever so slightly, add a touch of airy spaciousness, and crank up the dynamic punch just a skosh.

Simply put, the ACT 4 sounds incredible with movies and music alike, with a wide, open, cohesive sound that fills the room beautifully whether you're cranking out action movies in 7.3.6 or soaking in some tunes in straightforward stereo mode. Little details in movie scores that normally go unnoticed sparkle through the mix. And with music, I found that the preamp delivered the sort of depth, texture, and authority that you expect from really great dedicated stereo gear. Contrary to what you might expect with incredibly high-fidelity gear like this, though, the ACT 4 is also ridiculously forgiving when it needs to be.

I tend to watch a lot of YouTube documentaries, as well as the nightly netcast of The Young Turks in my home theater, and I can't remember ever giving a second thought to the sound quality of such streams. But the Acurus and its various modes of processing lent these low-fi streams an extra touch of space, of punch, of openness that really enhanced the listening experience. Hell, I couldn't help but notice that even Weather Underground on the Weather Channel sounded pretty fantastic through the ACT 4. This deft mix of purity of tone and detail with high-fidelity listening material and forgiveness with lesser-sounding programming is absolutely one of my favorite things about this preamp, regardless of its channel count or unique setup features.

I'll admit, I didn't really hear any appreciable difference between a 7.3.6 setup and 7.3.4 in my room, which probably has a lot to do with the fact that my main seat is a mere 6.5 feet from my screen, and four overhead channels is way more than enough to bridge the gap between the front and back of my room. But if you have a room that's much deeper than it is wide (a room with two rows of seating, for example), you'll certainly appreciate the extra overhead channel count. I did, however, like the effect of having front width channels, and I wish I had the space to run such a setup permanently.

No matter how many channels you're running, you'll also appreciate just how easy the ACT 4 is to operate. You would expect the remote control for such a device to look like the control panel of a space shuttle. Nope. Instead, it's the picture of simplicity. Take away the input selection buttons, and all you're left with is standby, volume, mute, a button for night mode (which is far more than simply dynamic range control, by the way), and options for Auto, Direct, Dolby, and DTS processing. Auto, as you might have guessed, simply takes whatever source format you feed the ACT 4 and processes it in such a way as to fill whatever speaker configuration you have set up. Direct gives exactly what it's given (with bass management thrown in, so you get the benefit of subs if they're present in your system, even with stereo material). And the Dolby and DTS Neural X buttons let you choose on-the-fly between the two companies' upmixing processes, depending on your tastes. Since the ACT 4 actually processes Dolby and DTS at the same time, switching between modes to determine which, if either, you prefer takes almost no time at all.

That same nimbleness extends to every other aspect of the ACT 4's operation. The unit powers up in just a couple of seconds, and switching between inputs is nigh instantaneous. What's more, the quirks you expect to run into with a product from a small, independent American hi-fi company are nowhere to be found, at least not in my experience. I never ran into any HDMI handshaking issues, lockups, or anything else of the sort. It is worth noting, though, that my review unit is running an older HDMI board with only one of its eight HDMI 2.0 inputs being HDCP 2.2 compliant, and only one of its two outputs being so. Starting in June (probably by the time you read this), all ACT 4 preamps will ship with a new board that's 2.0a compliant from end to end, with all inputs and outputs sporting HDCP 2.2 compliance. Thanks to the modular design of the ACT 4, Acurus will also be able to make this new board available to existing ACT 4 customers in the form of a paid field upgrade that can be done either by the local dealer or by the factory in Indiana.


High Points
The Acurus ACT 4 is one of the few consumer-friendly surround sound preamps on the market with 16 channels of output and support for both DTS:X and Dolby Atmos.
Regardless of its channel count, it's simply an incredible-sounding preamp, with output that's just barely to the sweetened side of dead-on balls accurate. It's deliciously tactile and impactful with movie soundtracks, and its performance with music is rich, detailed, nuanced, and room-filling even in stereo mode. Make no mistake about it: the ACT 4 may be an incredibly advanced home theater product in every respect, but it's also an audiophile component at heart. Its impeccable fidelity is appreciated with music and movies alike, but it's also forgiving enough to make YouTube streams sound pretty fantastic.
For such a complex product, it's remarkably easy to configure and is, without question, the easiest-to-operate multichannel preamp/processor I've evaluated in ages. Tapping into sound mode tweaks, ADC sample rates (up to 192 kHz), and other in-depth settings simply could not be more intuitive. You can even set Night mode to downmix to 2.0, 2.1, 3.0, 3.1, or 5.1, if you so choose, and the screen used to do so is so well-designed that I can't imagine anyone, even the most technically challenged, having trouble understanding exactly what that means.
You want Made in America? The Acurus ACT 4 is made in America! Ignoring the handful of components that have to be imported (like the Texas Instrument DSPs), the preamp is built by Key Electronics in Jeffersonville, IN--a highly respected manufacturing facility that primarily serves the aerospace/defense and medical industries. In other words, it's an incredibly well-built piece of gear.

Low Points
For now, the Acurus ACT 4 lacks built-in auto EQ, which may be a bummer for some. You'll have to calculate your PEQ settings yourself or import settings from Room EQ Wizard or other such offerings.
At the time of this writing, relatively few IP drivers for advanced control systems have been released (only Savant, Crestron, and OnControls). More drivers are scheduled for release over the upcoming weeks and months.
Firmware updates require a USB connection to a Windows computer. The program responsible for performing firmware updates is straightforward and easy to use; but, if you've grown accustomed to simple over-the-network updates, this may seem like an extra headache.

Comparison & Competition
The Acurus ACT 4's most direct competitor for the time being is likely the Lyngdorf MP-50 ($9,999), which adds Auro3D processing and RoomPerfect room correction, as well as digital media streaming capabilities (including AirPlay and Spotify). It also features an HDBaseT output, and its audio outs are all balanced XLR. Also worth noting is the fact that it features no analog audio inputs.

There's also the Datasat LS10, which comes in at $11,000 with Dolby Atmos processing or $15,000 with the Auro3D upgrade. The Datasat bumps up the parametric EQ to 10 bands per channel, and it also features Dirac Live room correction, but it doesn't yet do DTS:X (it's currently in alpha testing and on the way soon).

StormAudio's ISP 3D.16 ELITE ($13,800) is another potential contender that adds Auro3D and a version of Dirac Live. It also features SpherAudio binaural processing for its headphone output, plus advanced channel configuration capabilities that allow you to re-assign any unused output channels as subwoofer outs.

Trinnov's upcoming Altitude16, a scaled-down version of its Altitude32, will match the channel output capabilities of the ACT 4, but will also allow for configurations like 9.1.6 (whereas the ACT 4 is limited to two overhead channels when nine bed channels are selected because of the three dedicated subwoofer outputs). Your guess is as good as mine on pricing and availability, though.

Perhaps the biggest competition that the ACT 4 faces in the coming months is the eventual release of Emotiva's RMC-1, a 16-channel processor with Dirac room correction that's slated to sell for $4,999. Little else is known about the RMC-1, including its release date, but a prototype unit shown at CES 2017 did lack the ACT 4's multichannel analog inputs.

You would expect that the most exciting thing about Indy Audio Labs' Acurus ACT 4 is its 16-channel processing and support for six overhead channels for DTS:X and Dolby Atmos. And yes, those capabilities do make it stand out in the surround sound processor market right now. In practice, those ended up being mere features for me. What made the ACT 4 such a pleasure was its stunning audio performance (no matter the channel count) and the utter simplicity of operating it. Simply put, the fact that a processor this sophisticated is so utterly idiot-proof in day-to-day operation is a bit of a pleasant head-scratcher.

Until Indy Audio Labs cooks up its own room correction system, you may need a hand setting it up. But once that's done, the ACT 4 almost operates itself. Above all else, it sounds fantastic with practically any listening material. Reference-quality recordings ring through with a level of precision and clarity that other surround preamps aspire to, yet even the most mundane YouTube streams and TV shows sound warm, open, spacious, and inviting. For all its tricks, that may be the ACT 4's best.

Additional Resources
• Check out our AV Preamps category page to read similar reviews.
Production Begins on New Acurus ACT 4 Preamp/Processor at
• Visit the Acurus website for more product information.

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