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Onkyo TX-NR646 AV Receiver
Audio/Video Reviews

Onkyo TX-NR646 AV Receiver

A receiver that’s economically potent in performance and must-have audio features of ‘now’.

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It was a very late entry when we reviewed the Onkyo TX-NR636 AV receiver. In fact, we were racing against the clock in lieu of the upcoming models about to arrive. Despite the poor timing it was hard to ignore the brimming array of features for an attainable price.

Now that the home market has finally balanced itself among the introductions of latest audio formats and content encryption, you’d expect the privilege to come at an unwavering premium. However, amazingly enough, the TX-NR646 is another excellent AV receiver that bucks the expensive trend. The value probably doesn’t get much better than this mid-tier choice.

What doesn’t quite work

But before the acclaim I’m just gonna come right out and say it: the TX-NR646 is a fine AV Hub for any home-oriented build, but you’ll have to deal with the bulk. It’s essentially a black box that’s 20.7 lbs (9.4 kg) and is over a foot deep front to back. Compared to other receivers though it’s not exactly a standout, although completely functional with rows of buttons while resisting large dials. It’ll get the job done when you lose the remote but the look is generic in plain sight.

Speaking of which, all the other complaints we had are still relevant. The remote control remains a weak exercise of compromise due to its shorter length along with the uninformative layout, it reduces the button count but feels unintuitive and vague as a result. Onkyo also didn’t get the memo about their onscreen menu because that also goes untouched, and remains just as archaic with long folder directories and poor navigation. A dated and bare approach only longtime enthusiasts could immediately make sense of.

But everything else is great

Despite showing its age in areas, the TX-NR646 is a hell of a lot better everywhere else, although it’s not an extraordinary transformation. The obvious changes include more additional tweaks to sweeten the already attractive offering — boasting onboard Wi-Fi and Bluetooth for a suite of wireless playback through AirPlay and streaming services (Pandora, Spotify, SiriusXM, Deezer, etc.), and of course DTS:X object-based surround sound (when available) along with Dolby Atmos.

Connectivity has been modestly improved in quantity and peace of mind with one extra HDMI input (8 in/2 out), phono capabilities for a turntable, and a total of three HDMI 2.0/HDCP 2.2-capable source inputs for futureproof upgrades. Old-school analog ports such as composite and YCbCr component are kept if you simply can’t let go of that dusty VCR or PlayStation 2 always sitting on standby.

AccuEQ calibration

Room calibration utilizes the proprietary AccuEQ system, which involves placing the included microphone in the center of the room and let it do its work. At this point I’m fairly certain that Onkyo took the MCACC structure from Pioneer and incorporated it into their own AVRs, they even ‘borrow’ the same microphone; not that I’m complaining because it’s one of the better embedded configuration tools that comes somewhat close to our current build measurements. However, there are differences such as the inability to cancel during the procedure, and for whatever reason manually setting our speaker system wasn’t even recognized until you go through the routine at least once, an annoyance since it takes roughly 5-10 minutes to complete at embarrassingly loud volume.


Editors’ Note: At the time of this writing DTS Inc.’s latest object-based surround format, DTS:X was not made available to test. However, Onkyo has confirmed that this feature will be coming later this year to compatible AVRs as a free downloadable firmware update.

For the element of surround sound, things have changed considerably with the advent of Dolby Atmos and we’ve already experienced it firsthand. For the majority of our testing with the TX-NR646, we had those nice Elite Atmos speakers and subwoofer from Pioneer on hand while sticking to our little collection of Blu-rays. But we changed things up a bit with The Expendables 3 and American Sniper, two films that handle action and environment quite differently in scale.

In the case of Stallone’s self-admiring homage to 1980s action movies; those height channels were indisputably direct and effective, adding boisterous punch overhead to match the often feverish scenes filled with bullets and explosions. Admittedly, the implementation is meant to offer some added dimension to the reaching depth and pounding low ends hit physically rattles you when heard. There’s nothing soft about The Expendables 3 as its core forcefully draws you in for entertainment’s sake.

American Sniper has intensity all its own but is a lot more subtle in execution, preferring to carefully choose when loud periods of action are appropriate or when distressing moments need to grab your ears. In other words: the Atmos height implementation is incredibly nuanced as we almost forgot about the upward speakers pulling their acoustic weight except when a helicopters flew by or other firefights heard in the distance. This is actually the point since this film is largely built from dialogue and drama rather than mindless action.

Because each main channel of the TX-NR646 gets 170 watts of power (height-specific channels are rated 100 watts) there’s a surprising amount of power with even the default (and only) 5.1.2 arrangement (for reference, the last decimal number is strictly for height and takes over two of the 7 main channels). Compared to the 9.2 channel Pioneer SC-89 we played around with the TX-NR646 has a more grounded presence when the front lefts and rights are at higher placement to compensate. This approach is recommended by Dolby to accommodate the upward firing drivers which reflects the sound off the ceiling.

With that in mind, the SC-89 (5.1.4 or 7.1.2 configurations maximum) is obviously going to provide a fuller reference-based Atmos experience. But to be honest, we actually prefer the Onkyo as it lends itself to simplicity without reassembling or mounting above, rather than more affordable add-on modules. The TX-NR646 is easier to live with and a lot more practical in smaller and medium dwellings, an advantage in our slightly compact testing area.

More conventional uses for standard Blu-rays is more subdued when you optimize Dolby TrueHD and DTS-HD Master Audio tracks with the now-standard Dolby Surround codec (think Pro Logic combined with Atmos enhancements). The sound quality for stereo and Hi-Res Audio is well-composed when listening to Peter Frampton or The Who with clean mids, vocals, and treble that hardly comes off frazzled at higher levels. Obsessed audiophiles may scoff at the acute imperfections but there’s more than enough clarity to please everyone else.


We liked its predecessor, but there’s a reason to love and recommend the Onkyo TX-NR646 AV receiver. For such a relatively reasonable amount of money, this is a fantastic midrange AVR in overall performance and advanced dimensional formats  — something few other brands can compete with at this level.

About the Author: Herman Exum