Onkyo TX-NR646 review & specs

Onkyo TX-NR646 7.2-Channel Network AV Receiver: Full and Honest Review

Onkyo TX-NR646

Amazing Dolby Atmos sound for a great price – that’s what Onkyo TX-NR646is about. 4 Built-in decoders, recognition of 7 audio formats and ability to control the receiver remotely makes Onkyo TX-NR646 one of the best in its price category. Also, there is something outstanding about it that you should know before reading about the rest positives of this receiver – it has a 170W output for a single channel, this is a unique parameter for something that costs just few hundred dollars, don’t you think so? If you still unsure if it is worth buying or not, just look at the more detailed review below!

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Onkyo TX-NR646 has modern design and black color which appeals to a lot of customers on the market due to its universality and a nice match to any kind of TV. It has only one wheel for volume on the right which makes it really comfortable as you can’t get mix the wheels and end up in a cacophony of sounds. The built-in fluorescent display shows the mode the receiver is currently on. On the bottom, Onkyo TX-NR646 has a phone and HDMI inputs on the left followed by set-up on the right. In the middle, you can see a line that represents different mods receiver has. Just choose the one you need for now and enjoy the beautiful sound. If you think that somehow have done something wrong, do not panic – use a tuning/reset button on the top-right and it will help you find the best option. I strongly advise using a preset button to start with for the ones that have this receiver as their first one. Worth to mention, the buttons at the remote are very close to each other and quite small, their placement is pretty odd and there is no backlight feature. Also, it is quite slow to react so you need to be patient.


The signal-to-noise ratio of Onkyo TX-NR646 is low - 106 dB (NB lower the value, better the receiver is). Little display in the middle shows the functions currently in use while turned on and the current time while in sleep. 170W per channel, which sustains a frequency response of 20Hz-20kHz, makes a receiver to have a total output power of 580W, which is great, however it also means that operational power consumption is also bigger – it needs 360W (need to pay higher electricity bills, unfortunately) whereas in standby mode it requires only 0.1W. The Onkyo TX-NR646 has no sleep timer. Little thing, but still, be aware of it so your dreams to fall asleep while listening to music cannot be spoiled by waking up in the middle of the night due to the noise.

Sound Quality

Onkyo TX-NR646 has a built-in range of Dolby decoders, which include: Dolby Atmos, Dolby digital plus, Dolby surround and Dolby True HD. Audio D/A conversion happens at 32bit / 384kHz and total harmonic distortion is just about 0.08%. You can enjoy a clear sound from any point of the room due to a receiver having a 7.2 channel Surround Sound output with Theater-Dimensional Virtual Surround sound effects. Overall, the sound quality of this Onkyo definitely turns your house into a real cinema with 3D Volume sound all around.


Onkyo TX-NR646 has 2 AV inputs, 2 optical and 1 coaxial digital inputs, 8 HDMI inputs and 2 HDMI outputs. Please, be aware that it doesn’t have either coaxial or optical digital outputs. However, you can also link your phone or USB-stick to the receiver as it has a USB port and a phone connector so you can enjoy playlists that are on your phone. If you feel like there is not enough space to connect everything (like I did), I have connected my speakers remotely via Bluetooth. Also, note that you can also connect other devices using not only Bluetooth but WiFi and IEEE 802.3/IEEE 802.3u. I will strongly advise doing this if you want to connect your phone as it can act like a nice remote controller so better to have your phone with you rather than leave it on the receiver. Apple Airplay is very convenient for iPhone-users as now they can enjoy their Apple Music subscription with a great sound. The receiver also supports remote control which makes it more comfortable to use the receiver ( I use it for turning on and off) instead of looking for a manual controller all around.


Not a user-friendly menu. I found it quite hard without any guidance to figure out where is what. Once I did though, I found it amazing, however, make sure you read the instruction before use otherwise you will waste lots of time seeking for desired options like me. So here we go. There are two options for a set up: you can either use their sound device and do your set-up quite fast or do a whole set-up process manually. For beginners, the first option is definitely better. If you do it manually, please, ensure that you have the room to connect speaker wires if you are working in a typical two shelf TV stand. As well, I would recommend getting a decent gauged wire and a set of banana plugs for installation. Banana plugs seem great for quick and easy connection/disconnection of speakers, which can be quite handy if you ever have to relocate your receiver, replace it in the future, or if you just get speaker wires mixed up when installing.


Onkyo TX-NR646 is a great middle-class receiver that has quite a good choice of specs and amazing sound quality. Combined with extreme 170W power per channel and nice stand-by power consumption, this receiver is a real representation of amazing price/quality ratio. It would not suit the one who loves DTS as it doesn’t have this kind of decoders, however, if you are not passionate about specific decoder type, the opportunity to experience true Dolby Digital sound for a great price should not be missed!

Common features


Onkyo TX-NR646






3.9 of 5




Digital player

Internet radio

Network audio player

Amplifier class


Audio formats



Apple lossless






Built-in decoders

DTS neural:X

DTS-HD master audio


Dolby atmos

Dolby digital plus

Dolby surround

Dolby true HD

Power device

Operational power consumption

360 W

Standby power consumption

0.1 W

Built-in display






Total output power

580 W

Output power per channel

100 W, 170 W

Output impedance per channel

6 Ohm, 8 Ohm

Frequency response

20 Hz-20 kHz

Total harmonic distortion

0.08 %

Number of channels


Signal-to-noise ratio

106 dB

Connectivity interfaces



IEEE 802.3

IEEE 802.3u

Signal processing

HDMI pass-through

Up to 4K

Video conversion/scaling

Analog to HDMI up conversion

3D pass-through

has not

Upscaling via HDMI

has not

Connector type

AV inputs


Optical digital inputs


Coaxial digital inputs


HDMI inputs


HDMI outputs


Optical digital outputs

has not

Coaxial digital outputs

has not

Subwoofer outputs






Media content source





Tuner type


Tuner bands


Preset station qty


Additional features

A-B speaker switch

AIR Studios monitor certification

Three-zone capability


Advanced sound retriever (ASR) technology

Apple air-play support

Audio return channel (ARC)


Deep color


Auto power off

Pure direct mode

Dual-zone capability

Smartphone remote control

Sound features

Sound output mode

Surround Sound

Audio D/A converter

32bit / 384kHz

Surround sound effects

Theater-Dimensional Virtual Surround

Surround system class

7.2 channel

Digital sound processor (DSP)

DSP preset qty


Digital content protection

has not


Built-in clock

Sleep timer

has not


Shipping size

12.9 x 17.1 x 6.8 inches

Product weight

20.7 pounds