Home theater receiver announcements aren’t really that exciting these days unless you haven’t bought one for the past couple of years. The latest entry-level models are a bit more exciting though because there is always that possibility for existing features on more advanced models to make their debut on the cheaper models. In fact, Onkyo announced one of the most exciting revamps of their entry-level division making them more newbie friendly. Onkyo’s latest high-end receivers like the Onkyo TX-NR646 don’t have those exciting changes simply because it doesn’t need them. The target audience knows how to set up the receiver and they prefer having cutting-edge features. Besides, Onkyo needs to keep refreshing their products to stay in line with the competition.

Onkyo TX-NR646

Onkyo TX-NR646

About the Onkyo TX-NR646

The TX-NR646 is a step-down model from the new high-end TX-NR747. It replaces last year’s TX-NR636 and unlike some of the lower-end models, the Onkyo TX-NR646 has the same launch price as the price when the TX-NR636 launched. There aren’t as many new features though but this receiver is proof that 2015 is definitely the year to buy a new home theater receiver if you are targeting the upper spectrum.

Comparison with the Onkyo TX-NR636

The TX-NR646’s predecessor already had Dolby Atmos and that technology isn’t exactly mainstream even though more Blu-ray movies plan to support it. The Onkyo TX-NR646 retains this feature but a firmware update adds something that is a little bit more flexible – DTS:X support. DTS:X revolves around the concept of object-based audio and it tries to achieve the same result as Dolby Atmos which is to create a moving 3D sound atmosphere. The main difference is that the technology plays nice with just about any speaker configuration and can even work with speakers specifically made for Dolby Atmos. The functionality extends beyond movies too as you can adjust the volume of certain channels on a soundtrack such as the vocals. Movies with DTS:X support allow direct adjustment of the volume.

It is also nice to see the TX-NR646 having an additional HDMI port for a grand total of 8 HDMI inputs (1 on the front). These HDMI ports are outfitted with the latest HDMI 2.0a specification too so not only do these ports have 4K 60 Hz support but they also enable High Dynamic Range for a nice increase in detail for very dark and bright parts of the picture.

The aging Burr-Brown 192 kHz / 24-bit DAC is finally being replaced with something a bit more advanced. The Onkyo TX-NR646 uses a 384 kHz / 32-bit DAC made by Asahi Kasei instead. It still relies on the AccuEQ Room Acoustic Calibration system for optimizing the speakers but the calibration has been improved adding an additional measurement for better results.

Below is the back panel layout. Click on image to enlarge for a clearer view.

Onkyo TX-NR646 Back Panel

Onkyo TX-NR646 Back Panel

Other Features

The wireless connectivity features remain the same. The built-in Wi-Fi allows the Onkyo TX-NR646 to be a part of the home network. If you have any Apple devices that support AirPlay, you can stream music from these devices to the receiver quite easily. iOS and Android devices in general can also download the free Onkyo Remote app so the mobile device turns into a mini control panel where you can adjust settings or control the receiver’s independent streaming capabilities. The Onkyo TX-NR646 can stream to a couple of popular music streaming services including Spotify, Deezer, TuneIn and a few others on its own. Bluetooth remains as an option as well if you prefer wirelessly streaming the old fashioned way. Now all Onkyo needs to do is add Google Cast support.


With 170 watts per channel, the TX-NR646 works well with demanding speaker setups. It isn’t a huge leap from the TX-NR636 but DTS:X is the game-changer and it benefits the latest Blu-ray titles. It actually makes the TX-NR636 and other Dolby Atmos receivers without DTS:X tough sells simply because you most likely need extra equipment to take advantage of Dolby Atmos. DTS:X works with more types of setups and if you ever decide to go the Dolby Atmos route, Dolby Atmos support remains present.

The hi-current amp design of the Onkyo TX-NR646 also helps the speakers produce more accurate sound than the entry-level receivers. Combine that with the Wide Range Amplifier Technology or WRAT and you have virtually no distortion as well. Music sounds noticeably better too providing you are using high-quality MP3s or preferably lossless formats so you can really witness that new Asahi Kasei DAC go to work. The phono input allows you to listen to analog music too and the receiver really helps bring up the quality.



• DTS:X can improve the experience while having low requirements.

• Dolby Atmos support still present.

• HDMI 2.0a and HDCP 2.2 ready.

• Minor music quality improvements.


• Design needs an overhaul like the entry-models.

• Google Cast support would have made the receiver more platform agonistic.


Thanks to Dolby Atmos, DTS:X and the latest HDMI specification, the Onkyo TX-NR646 is truly the upper high-end receiver of the future. Upgrading from a receiver that is 2 or 3 years old is a huge step forward since the TX-NR646 is fully prepared for next year’s 4K displays and all the Dolby Atmos speakers coming out that aim to add more dynamics to the sound space. Owners of the TX-NR636 might want to wait for another cycle unless you feel your movie experiences need a major facelift. Just make you read into the DTS:X subject more to see if your speakers are truly ready for the technological improvements.

Update: There is a newer model > Onkyo TX-NR676