Onkyo has always been at the forefront when it comes to adopting and implementing new technology and features in their latest products. They were one of the first to add HDCP 2.2 and Dolby Atmos, and once again they lead the way by adding the latest Immersive Surround Sound formats to the new TX-NR646 7.2-Ch Network A/V Receiver - in this case DTS:X. All that is missing in this very affordable model is the Auro-3D format.
Features and Design
Visually, the TX-NR646 looks more or less the same as its predecessor, the TX-NR636, with only a large round volume control to break up the otherwise angular appearance. A closer inspection does however reveal a number of noticeable changes, both on the outside and inside; eight HDMI inputs (three HDCP 2.2 compatible), antennas for improved Wi-Fi/Bluetooth performance, Asahi Kasei’s AKM4458 384K/32 Bit DAC, and added AirPlay. The MHL interface on the front HDMI input is removed and the USB port has been moved to the back.
In short, no major changes compared to the previous model, apart from some added connectivity and improved digital-to-analog conversion. Oh, and DTS:X of course.
The AccuEQ room acoustic calibration has been improved as well as it now implements equalization on the front speakers, something we missed in the previous model. The measurements are still being made using only one position, but it's not a major issue at this relatively modest price, especially since the AccuEQ lives up to its name and actually include an EQ for the different speaker groups - including the subwoofer(!). It's a useful, although limited, 5-band EQ that can be adjusted in steps between -6dB and +6dB. The speaker terminals offer some flexibility and allows you to choose between traditional setups (2.0 up to 7.2), more immersive setups including Height Speakers, and Zone 2 and bi-amping.
The new features are also represented in the on-screen menus, which still looks typically Onkyo, meaning fairly well structured, easy to navigate and intuitive, but also a bit dull to look at. The remote control is pretty much the same as previously but with some minor changes. It still gets the job done and has clearly laid out buttons, but Onkyo also offers a Remote App (iOS, Android) that combines control and streaming functionality in one easy-to-navigate interface.
Video and Multimedia Functionality
The TX-NR646 supports 4K resolution up to 60Hz thanks to the HDCP 2.2 HDMI 2.0 inputs. It also supports 3D, Audio Return Channel, Deep Color, x.v.Color™, LipSync, CEC, Extended Colorimetry (sYCC601, Adobe RGB, Adobe YCC601), Content Type, 3D Dual View and 21:9 Aspect Ratio Video Format. It does however not up-scale lower resolutions to UHD, so you will have to leave the up-scaling to your TV.
Audio-wise it supports Dolby Atmos, Dolby TrueHD, Dolby Digital Plus, Dolby Digital, DTS:X, DTS-HD Master Audio, DTS-HD High Resolution Audio, DTS 96/24, DTSES, DTS, DTS Express, DSD and Multichannel PCM (up to 8ch).
You can also stream audio wirelessly via bluetooth or Wi-Fi, and it supports Spotify, Pandora, SiriusXM Internet Radio, Slacker and TuneIn. The USB port allows you to play media in FAT16 or FAT32 file system format.
Sound Quality & Listening Experience
We started the listening test by setting up the system using the AccuEQ acoustic calibration, and although the system does a decent job we still ended up doing some minor adjustments before we were completely satisfied with the result, and we used a variety of familiar music and movie scenes to get the TX-NR646 to sound as neutral as possible. We also played around with the various listening modes, but as the result ranged from mildly annoying to exceedingly bemused we ultimately decided to turn any unnecessary processing off. Whether you should use the listening modes or apply the EQ or not is a matter of taste and the condition of your listening room, but it's nice to know that you can do any necessary adjustments if needed.
We also did a quick measurement of the output stages and the TX-NR646 showed us some solid numbers – staying above 75 watts per channel with all channels driven hard. Movies rarely drive all channels at full force, but it’s good to know that this particular Onkyo have decent power reservs and can handle some stress.
Lately, ‘Mad Max: Fury Road‘ have quickly become one of our favorite movies to use as reference when we test new gear, specifically amps and speakers, as it is packed with high-octane action and awesome sound effects from start to finish, giving the audio equipment a rigorous workout, and also provides a Dolby Atmos track. This movie cover all frequencies and the LFE track is a good way to separate the wheat (the good) from the chaff (the bad) when it comes to bass performance – if you’re listening to good speakers and amps you should be getting a rather physical experience. In our case we mostly used a Klipsch Reference Premiere 5.1.2 setup, which may seem like a bit of an overkill considering the modest price of the TX-NR646, but it gave us a pretty good indication of how the Onkyo performs.
And it does indeed perform. Mad Max: Fury Road can be quite messy at times with a lot of things going on, but the TX-NR646 always managed to keep things under control. Dialog was easily distinguishable and kept from being muddied up by all the background noise, and the soundstage was both wide and deep with easy to pinpoint soundeffects. Sound effects like bullets whizzing over our heads, thunder, wind and sandstorms was presented with authenticity and realism, almost making us believe that we would have to sweep the sand off our listening room floor once we've finished watching the movie.
Any movie with a decent sound mix almost made us forget to listen critically, as we found ourselves immersed in whatever was happening on the screen, and we can’t think of a better testament to the TX-NR646’s abilities and performance. The powerful, well balanced, detailed and dynamic sound also makes music truly enjoyable. It may not reach the heights of some dedicated two-channel amps for the same price (or more), or its own bigger brothers (TX-RZ800 & 900), especially when it comes to the finest grains of resolution and ultimate power, but there’s no denying that the TX-NR646 is one of the top contenders in the sub $700 category.
The Onkyo TX-NR646 is powerful, balanced and dynamic, and it's been nothing less than a pleasure to use and listen to. The only thing that we can really complain about is that the AccuEQ could use some improvements. The fact that it also offers HDCP 2.2 and DTS:X means that it has very few competitors in this price class.
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● Equipped with 7 ch amplifier
● Supports playback in Dolby Atmos format which provides 360-degree placement and movement of sounds including overhead sound
● Supports playback in DTS:X, which is DTS's nextgeneration object-based surround sound technology that includes height to deliver a fully-immersive listening experience to your living room
● Dolby Surround listening mode expands 2 ch, 5.1 ch or 7.1 ch source to available speaker configurations
● Equipped with 4K compatible HDMI IN/OUT jacks
● Equipped with 2 HDMI output jacks
● Supports the HDMI Standby Through function which allows signal transmission from players to the TV in standby state
● Supports HDCP2.2, a strict copy-protection for providing high quality content (HDMI IN1 to IN3/HDMI OUT MAIN/ SUB)
● Supports ARC (Audio Return Channel)
● Supports USB storage playback
● Supports variety of network functions such as Internet Radio, DLNA, AirPlay etc.
● Supports Wi-Fi and Bluetooth®
● Equipped with a PHONO jack enabling connection with a turntable
● Bi-Amping capability
● A/V Sync Function to correct deviation of audio and video
● Multi-zone function which allows you to play a different source in another room from the main room
● 32 bit DSP (Digital Signal Processor) with excellent calculation performance
● Music Optimizer™ for compressed digital music files
● Phase Matching Bass System
● Automatic speaker setup available using supplied calibrated microphone (AccuEQ Room Calibration)
● Supports playback of MP3, WMA, WMA Lossless, FLAC, WAV, Ogg Vorbis, Apple Lossless, DSD, Dolby TrueHD via network and USB storage device (the supported formats will differ depending on the use environment)
|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|
|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|
|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)|