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Review: Onkyo TX-NR646 7.2 Channel Receiver with DTS:X and Dolby Atmos


Another receiver that made its way to the market to join the DTS:X race, the Onkyo TX-NR646 stands to take a spot that doesn’t hurt your wallet as bad as some of the others. Last year, AVR manufacturers raced to release models that supported the then-new format, Dolby Atmos. The same race is here once again as DTS:X takes the industry with an enjoyable surprise.

Now that DTS:X is finally here, you can expect to see over a dozen AVR models hit the streets between now and the end of the year. The most noticeable one being Yamaha’s new flagship that we covered at the start of the month. Now we sit down with Onkyo’s model that is aimed for the mid-range shoppers that aren’t looking for something as expensive, yet still want a lot of umph.

The new receiver delivers both DTS:X and Dolby Atmos at up to 7.2 channels while supporting all of the other formats we have grown to love over the years. It also weighs heavily on its streaming capabilities, just like most achieving models on the shelf.

atmos-speakersFor those looking for Dolby Atmos, is important to point out that the TX-NR646 only supports the front two height channels in the ceiling. If you are looking for all four channels, you will have to upgrade to something like the Yamaha or another high-end model. As long as the front two channels are fine with you, the additional channels do provide noticeable depth to the content you are watching (assuming the content support the Atmos format of course). When using those height speakers, the remaining configuration is your typical 5.2 setup (two mains, two rears, a center and one or two subs).

646-DTS-X-readyDTS:X however is universal to however many channels you have. Ceiling, sides, front, back; it really doesn’t matter since it is an object-based format that makes use of all of your speakers, wherever they are (as long as the receiver knows their locations of course, and you don’t randomly move them around to off-positions). DTS:X is an exciting addition to the DTS formats, as it provides a completely different–more natural–feel to the audio surrounding you. We have discussed the new format a number times now, including directly with the engineers of DTS at CES this year.

What’s great is that you can expect to see most of your major films releasing from this point forward with support for one or both of these formats. This helps, since there aren’t a lot of options to choose from at the moment, with just around a dozens movies so far that support Atmos alone. DTS:X has only one movie sporting the new format (Ex Machina, on Blu-ray), that just released to the market recently. There may be a slow start to that format as studios are just now beginning to add it to the mix (pun-intended).

The new receiver offers 100 watt output to each channel, which is slightly higher than their previous year’s model (95w). This is enough to feed almost any store-bought speaker, covering the majority of consumers looking to buy into surround solutions. This is one of the areas where price begins to climb noticeably, as money truly is power. For the price of the unit, 100w is great.

ONKYO_ak4458_DACIt offers an on-board AKM DAC for digital music processing. Although it isn’t as great as a Burr Brown, Wolf or ESS SABR, this also costs money if your looking to improve on this. The AKM performs just fine, giving a good listening range for all your favorite formats. It falls into the range of slightly above-average (to our ears). You typically don’t expect better unless your spending over a thousand dollars on a receiver.

Performance: The receiver handed well for various music and movie benchmarks. The Atmos speakers do offer that extended depth to the surround experience. Of course, this heavily depends on how well Atmos has been mixed into the feature you are watching. Some movies performed quite well, while others were barely noticeable.

We were limited to test footage for testing out DTS:X on this receiver since we do not have a copy of Ex Machine sitting around (yet). Possibly in the future, we may come back to update this if we decide to add the movie to our test collection. The demonstration videos performed well though and all of the speakers delivered just the right balance of sound between all directions. As I mentioned, the new format really does stand out, adding something completely new to what you are watching. We shall see where this goes in the future as more movies begin to release using the format.

Playback of DSD audio and a handful of FLAC selections, the TX-NR646 sounded really good. Not bad for the price it comes at, if not a little bit richer than that. It really helps when you start playing with true DAC processing. Also, Bluetooth streamed audio from multiple devices resulted in solid playback as well as exceptional range (over 70 feet in our tests).

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Streaming: There is nothing like options when it comes to streaming selections to choose from. This receiver definitely delivers, allowing you to select from options like TuneIn Radio, Pandora, Spotify Connect, SiriusXM, Slacker and Deezer. It also supports a number of ways you can stream your music from other devices such as AirPlay and Bluetooth, without having to purchase any additional devices to plug into the back to support such with.


Connectivity: Here is something worth talking about, as the TX-NR646 offers a total of 8 HDMI inputs (7 on the rear, and 1 on the front). Each of them are HDMI 2.0 with support for HDCP 2.2, opening it up to all of the latest content.

You also have 8 RCA inputs on the back for audio, including a phono input for turntables and 3 of which include video. There are 2 RGB inputs, 2 optical and 1 digital coaxial.

The HDMI-out for your TV supports ARC (audio return channel) so that it can receive the audio back from the TV (in-case anything else plugs directly into the TV for signal). The second HDMI-out is for your separate Zone or whatever else you want to plug it into (ie, if you have a projector on the ceiling).

You have the option for both ethernet input as well as built-in WiFi so that you can add it directly to the network without having to buy any optional WiFi adapter parts. As of a few years of ago and later, manufactures were pitching WiFi as an “optional” feature, which bugged a lot of consumers since most other devices (ie, TV) already had it built-in.

Apps! All of the good manufacturers nowadays seem to come with an app, so of course Onkyo are one of these. You have the option of downloading an app from either the iOS or Android stores that can not only control most of the functions of the receiver, but also stream music from your device to the receiver with. The app isn’t bad and doesn’t cause any confusion. This is still something you can expect to see improvement on as manufacturers strive for a more consistent feel between the app and on-screen interface.

Setup Friendliness: Just like most of the receivers in this price range and above, it comes with its own calibration method using a single microphone that you connect to the front of the unit with. Instructions are straight-forward, and it automatically adjusts the required settings based on the position, range, volume and distance of all of your speakers. As usual, there is always the chance that you will want to fine-tweak the settings a little to your liking, once it has finished. In the end, it takes a load off of the user by offering a quick path to the finish line.

Design: The TX-NR646 doesn’t come with anything new when it comes to looks as it resembles just about every other Onkyo you have seen for the last 30 years. A few changes of course, such as the rabbit ears in the back and flat rotation dial. There really isn’t much you can do to a receiver though, as the average shopper is looking for performance, not eye candy (we save that for the audiophiles looking to justify the many thousands they would spend on a high-end unit). You won’t find anything to complain about in the design as nothing stands out as tacky.

Despite some of the comments you might read in regards to the remote, there is nothing more confusing about this than any other AVR remote would be–at least, any AVR that came packed with features like this one. You find the same number of buttons to choose from, if not more, with other companies such as Yamaha or Pioneer. It offers many inputs, decoded formats, scenes and other media selections. Once you sit down with it long enough, you find there are many other controllers worse than this.

Our Conclusion

The Onkyo TX-NR646 is a solid receiver with plenty of options to choose from. The DAC isn’t the best, but it still performs quite well (better than we had expected). Streamable selections are nice and we always smile at the availability of SiriusXM. The price feels right for the unit and we are glad they decided to keep on top of the latest for surround formats. We decided to offer this model a 7.5 out of 10 score. It’s not perfect, but it doesn’t fall too far behind. Well worth the cost.

7.5 / 10 stars           



Additional Images:

Onkyo TX-NR646 7.2-Channel Receiver - FrontOnkyo TX-NR646 7.2-Channel Receiver - Back Remote TX-NR646-Onkyo-Visual646-INTRO


Amplifier Section
Power Output
All Channels 170 W/Ch (6 Ohms, 1 kHz, 0.9% THD, 1 Channel Driven, FTC);
100 W/Ch (8 Ohms, 20 Hz–20 kHz, 0.08% THD, 2 Channels Driven, FTC)
Dynamic Power 240 W (3 Ohms, Front)
210 W (4 Ohms, Front)
120 W (8 Ohms, Front)
THD+N (Total Harmonic Distortion + Noise) 0.08% (20 Hz-20 kHz, Half power)
Damping Factor 60 (Front, 1 kHz, 8 Ohms)
Input Sensitivity and Impedance 200 mV/47 k-ohms (Line)
3.5 mV/47 k-ohms (Phono MM)
Rated RCA Output Level and Impedance 100 mV/2.2 k-ohms (Zone 2 Line Out)
200 mV/470 Ohms (Subwoofer Pre Out)
Maximum RCA Output Level and Impedance 1.0 V/2.2 k-ohms (Zone 2 Line Out)
2.0 V/470 Ohms (Subwoofer Pre Out)
Phono Overload 70 mV (MM, 1 kHz, 0.5%)
Frequency Response 10 Hz-100 kHz/+1 dB, -3 dB (Direct Mode)
Tone Control ±10 dB, 20 Hz (Bass)
±10 dB, 20 kHz (Treble)
Signal-to-Noise Ratio 100 dB (Line, IHF-A)
80 dB (Phono MM, IHF-A)
Speaker Impedance 6 Ohms–16 Ohms
Video Section
Input Sensitivity/Output Level and Impedance
Video 1.0 Vp-p/75 Ohms (Component)
0.7 Vp-p/75 Ohms (Component PB/CB, PR/CR)
1.0 Vp-p/75 Ohms (Composite)
Component Video Frequency Response 5 Hz–13.5 MHz/+0 dB, -3dB
Tuner Section
Tuning Frequency Range
FM 87.5 MHz–107.9 MHz
AM 530 kHz–1,710 kHz
FM/AM Preset Memory 40 stations
Power Supply AC 120 V~, 60 Hz
Power Consumption 6.4 A
No-Sound Power Consumption 70 W
Standby Power Consumption 0.1 W
Dimensions (W x H x D) 17 1/8″ x 6 13/16″ x 12 15/16″ (435 x 173.5 x 329 mm)
Weight 20.7 lbs (9.4 kg)



DTS:X Ready

DTS:X is a next-generation object-based surround sound technology that includes height to deliver a fully-immersive listening experience. DTS:X provides listeners the ultimate in flexibility, immersion, and interactivity. Unlike channel-based audio, you will be able to personalize your audio experience. For example, you can turn up just the dialog within a mix. DTS:X allows you to customize to your room layout as well as control dialog and dynamic range.

Dolby Atmos

With Dolby Atmos, sound comes alive from all directions, including overhead. The format combines a channel-based audio bed with object-oriented sound to place and move specific effects around the room, creating a breathtakingly realistic and captivating sonic atmosphere.

Sound designers and artists are free to mix in a 3D space, steering effects through surround channels and adding a seamless overhead dimension with discrete height channels.

Additionally, a new Dolby surround up-mixer allows for your current channel-based content (that has not been mixed for Dolby Atmos) to be expanded to fill the flexible speaker layouts of a Dolby Atmos system.

Ready for UltraHD

The latest HDMI specs and HDCP 2.2 compatibility support the formats and technologies planned for Hollywood content. The newest HDMI offers a significant increase in bandwidth (up to 18Gbps) to support new features such as 4K@50/60 (2160p), which is 4 times the clarity of 1080p/60 video resolution.

This Onkyo AVR has the latest HDMI version, which enables transmission of HDR formats, and provides enhanced picture quality by simultaneously enabling greater detail for both the dark and bright parts of an image.

Stream Virtually Any Music

The TX-NR646 has AirPlay, Wi-Fi and Bluetooth technologies built in. The free Onkyo Remote app puts a range of streaming options at your fingertips, from universal hi-resolution audio via network-attached devices to internet streaming services to music on your smartphone and tablet. Or pair up and enjoy whatever’s playing on your Bluetooth-compatible device for huge cinematic sound.

This receiver comes loaded with Spotify, Pandora, SiriusXM Internet Radio, Slacker and TuneIn. You can select a station and search for music available on these services via the Onkyo Remote app on your phone. You’ll never be short of your favorite music to enjoy.

170 Watts per Channel

From the quietest dialog passages to booming action scenes, Onkyo’s exclusive amplification technology dramatically enhances the audio dynamics of your movies, music and games.

This Wide Range Amplifier Technology (WRAT) is at the core of Onkyo’s signature sound. The innovative amplifier design is comprised of three key elements:

(1) A low negative feedback design for punchy, true-to-life sound, and cleaner audio across the frequency ranges

(2) Closed groundloop circuits to reduce individual circuit noise and keep the ground potential free of distortion

(3) A high instantaneous current to handle big dynamic gains

This allows massive power at 170 W/Ch (6 Ohms, 1 kHz, 0.9% THD, 1 Channel Driven, FTC) and 100 W/Ch (8 Ohms, 20 Hz–20 kHz, 0.08% THD, 2 Channels Driven, FTC).

High-Grade DAC

No matter what you’re listening to, it will sound powerfully full, clean and clear. A premium-quality AK4458 digital-to-analog converter from Asahi Kasei implements unique low-distortion filtering technologies for clear sound, and unlocks the full potential of any audio format, including compressed, lossless, and hi-resolution audio (MP3, WMA, WMA Lossless, FLAC, WAV, OggVorbis, AAC, Apple Lossless, DSD 5.6 MHz, LPCM, and Dolby TrueHD).

Classic Analog & Hi-Resolution Digital

The receiver is engineered for hi-res analog and digital audio. You can spin your classic vinyl and hear it in all its analog glory and stream your networked hi-resolution digital files. Both analog and digital audio sound its warmest and clearest. The TX-NR646 supports hi-res audio playback, gapless playback, and the ability to play DSD, Double DSD, FLAC and ALAC along with other Hi-Res formats.

Easy Zone 2 Audio

The TX-NR646 features Powered Zone 2 and Zone 2 line-outs. This lets you assign two channels to power audio in a room equipped with speakers. An existing hi-fi system in a third room can also be connected via the line-out, enabling the use of the A/V receiver as a pre-amp and audio server.

Control content in the two zones via remote app; play the same song in all zones using Whole House Mode; or enjoy a different song in each room.


Are you a manufacturer or distributor that would like us to test something out for review? Contact us and we can let you know where to send the product and we will try it out.

7.5 Impressive
  • Final 7.5
  • User Ratings (8 Votes) 5.8

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