Onkyo TX-NR646 (USA version)
- 7.2 channels
- 7.1 channel processing
- 100 W (8 Ω, 20 Hz - 20 kHz, 2 channel driven)
- Dolby Atmos, DTS:X capable
- HDR10, 4K Passthrough
- AirPlay, DLNA
- Ethernet, Wi-Fi, Bluetooth
- USB and Phono inputs
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Onkyo TX-NR646 was introduced in 2015. It is equipped with 7 channel amplifier with 100 W (8 Ω, 20 Hz - 20 kHz, 2 channel driven) power per channel and is capable of 7.1 maximum channel processing. It supports Dolby Atmos and DTS:X, passes 4K/60Hz video signal.
We evaluated the a/v receiver and gave 81 overall score out of 100. Our ranking system is based on the amplifier specifications, audio and video features, connectivity, multizone capabilities, radio and many other details.
Pros and Cons
In this section we present pros and cons of Onkyo TX-NR646.
|DSD via HDMI|
|Auto Speaker Calibration System with Mic.|
|New HDCP Version|
|4K or 8K Video Passthrough|
|Analog To HDMI Upconversion|
|Many HDMI Inputs|
|Many RCA Line Inputs|
|Many Optical Inputs|
|Composite Video Inputs|
|Component Video Inputs|
|Independent Power Supply|
|No Front Wide Channel Support|
|No Dolby Atmos Height Virtualization|
|No IMAX Enhanced|
|No Auro 3D with Auro-Matic Upmixer|
|No Dolby Vision|
|No 4K or 8K Video Upscaling|
|No Chromecast Built-In|
|Does not Work with Amazon Alexa|
|Few 8K Inputs|
|No RCA Pre-Outs|
|Old Bluetooth Version|
Here we are comparing Onkyo TX-NR646 to its predecessor TX-NR636 and displaying the major changes.
|UPGRADES||Onkyo TX-NR646||vs||Onkyo TX-NR636|
|Higher DAC Specs||384 kHz/32 Bit||vs||192 kHz/24 Bit|
|DTS:X||up to 5.1.2 after firmware update||vs|
|DTS Dialog Control||vs|
|Dialog Level Adjustment||DTS:X only||vs|
|More Advanced Auto Speaker Calibration System||AccuEQ Advance||vs||AccuEQ|
|AirPlay||AirPlay||vs||AirPlay via optional Onkyo RI Dock DS-A5 (sold separately)|
|More HDMI Inputs||8 (1 front)||vs||7 (1 front)|
|More RCA Line Inputs||7||vs||6|
|More RCA Line Outputs||1||vs|
|More Optical Outputs||vs|
|More Component Video Inputs||2||vs||1|
|Bigger Power Supply||6.4 A||vs||6.3 A|
|Higher Power Output (8 Ω, 20 Hz - 20 kHz, 2 channel driven, FTC)||100 W (0.08% THD)||vs||95 W (0.08% THD)|
|DOWNGRADES||Onkyo TX-NR646||vs||Onkyo TX-NR636|
|3-Stage Inverted Darlington Circuitry||vs||Front & Center Channels|
|Surround EX||vs||also known as Dolby Digital Surround EX|
|Video Signal Upscaling||vs||up to 4K/30p (Marvell Qdeo)|
|Component Video Maximum Resolution||480i/576i||vs||1080p|
|MHL Input||vs||Front HDMI|
|Less Coaxial Inputs/Outputs||1||vs||2|
|Less Composite Video Outputs||vs||1|
|Less Component Video Outputs||vs||1|
|Front A/V Inputs||HDMI||vs||HDMI/MHL, USB|
|Color-Coded Speaker Terminals||vs|
|Lower Power Output (6 Ω, 1 kHz, 1 channel driven, IEC)||160 W (1% THD)||vs||165 W (0.9% THD)|
|Lower S/N Ratio (Line, IHF-A)||100 dB||vs||106 dB|
For more detailed comparison between the models please visit Onkyo TX-NR646 vs Onkyo TX-NR636.
7 channel Amplifier
Onkyo TX-NR646 features 7 channel power amplifier. It is rated at 100 W (8 Ω, 20 Hz - 20 kHz, 2 channel driven).
- WRAT (Wide Range Amp Technology): Onkyo TX-NR646 features Onkyo’s Wide Range Amp Technology (WRAT) circuit layout that prevents phase shifting by pushing the roll-off point higher than the listening-level frequency. Amplifying sound without phase shift creates an uncommonly well-focused and realistic audio image. If phase shift occurs and signal timing is not accurate, then neither is the resulting audio image.
Onkyo TX-NR646's 7 channel amplifier can be assigned for different speaker configurations.
- Dolby Atmos Configurations: The following speaker configurations are supported for Dolby Atmos:
- 5.2.2 with internal amplifier.
- DTS:X Configurations: The speaker configurations for DTS:X are the same as for Dolby Atmos:
- 5.2.2 with internal amplifier.
- Configurations without height channels: There are also other speaker configurations available which do not include height channels:
- 5.2, 7.2 with internal amplifier.
- 2-ch Bi-Amp: Onkyo TX-NR646 allows you to bi-amp up to 2 main channels simultaneously. During bi-amplification two amplifiers are used for one speaker. One amplifier powers the midrange and tweeter section of the speaker and another amplifier powers the low frequency woofers. Each amplifier is less loaded and performs better. In order to use this feature speakers must have 2 pairs of connectors.
Onkyo TX-NR646 supports Dolby Atmos. It is a cinematic audio format in which sounds exist as individual entities, called audio objects. In Dolby Atmos, any sound can exist as an independent audio object, free of channel restrictions. They can be precisely placed and moved anywhere in your room, including overhead, to flow above and around you in three-dimensional space. Through the use of audio objects, overhead sound, and all the richness, clarity, and power of Dolby sound, Dolby Atmos turns your room into an amazing place for entertainment. The format supports up to 128 simultaneous independent audio objects in a mix for rich, realistic, and breathtaking sound. It recreates the director's original concept through descriptive metadata to provide customized playback for home theater and delivers sounds above you through overhead speakers, special upward-firing Dolby Atmos speakers, or a Dolby Atmos enabled sound bar.
- Dolby Surround Upmixer: If the content is not mixed in Dolby Atmos then the Dolby surround upmixer will expand the audio to all channels including ceiling speakers. The upmixer has replaced the Dolby Pro Logic II family with improved upmixing algorithms.
Onkyo TX-NR646 supports DTS:X. A technique used in DTS:X is similar to the one used in Dolby Atmos. Instead of a fixed number of channels, DTS:X defines object locations from the listener in polar coordinates. An a/v receiver then dynamically renders sound according to the current speaker configuration. The speaker layout employed by DTS:X is the sum of Dolby Atmos and Auro-3D. It has standard 7.1 channel base layer, a 5 channel height layer above the base layer on the front and side walls, and 3 rows of speakers on the ceiling.
- DTS Dialog Control: This function adjusts the dialog levels during playback of the DTS:X stream. It allows you to separately increase the dialog levels in contrast with the background sound and hear dialog easily even under noisy circumstances.
- Advanced Music Optimizer: Compressed music enhancement in Onkyo TX-NR646 is done by Onkyo’s Advanced Music Optimizer. While MP3 or AAC files may sound fine through the headphones of your portable digital player, the limitations of these files can be exposed when played back through a quality home entertainment system. This is because a significant amount of high-frequency bit information is lost during the file-compression process. To counter this, Onkyo has designed the Advanced Music Optimizer to compensate for lost bit information and improve the quality of compressed audio signals. This results in a clearer and more expansive sound. Also included in this technology is a loudness correction feature that further improves the audio character of compressed files.
Onkyo TX-NR646 comes with AccuEQ Advance room correction system and includes the calibration microphone.
- AccuEQ: First, AccuEQ detects the presence of speakers and evaluates the impedance of each. Next, it pinpoints their distance relative to the main listening position using the mic and sets suitable sound-pressure levels. Then it selects the optimal crossover frequency so that deeper bass rolls smoothly off to the subwoofer. Finally, AccuEQ performs frequency response equalization based on room-acoustic and speaker data collected via microphone. The sound-field is now tailored around the listening position, resulting in a more immersive and realistic in-film experience.
Onkyo TX-NR646 features 8 HDMI inputs. It has 2 outputs which work parallelly and output the same signal.
- 4K/60Hz Passthrough: All inputs pass up to 4K/60p (RGB/YCbCr4:4:4/YCbCr4:2:2, 24 bit) video signal.
- Analog To HDMI Upconversion: The a/v receiver supports video upconversion, so you can connect your analog Component and Composite video sources and Onkyo TX-NR646 will output them via HDMI. This means that you will need only one HDMI cable to connect to your TV.
- HDCP 2.2 Copy Protection: 3 inputs and 2 outputs are HDCP 2.2 compliant which is a requirement for 4K/HDR copy-protected content transmission.
- 3D Ready: Onkyo TX-NR646 is able to pass 3D video through HDMI.
Onkyo TX-NR646 supports HDR (high dynamic range) video formats such as HDR10. High dynamic range video has greater dynamic range than standard dynamic range (SDR) video with brighter whites and deeper blacks. The result is greater contrast and more details in dark and bright areas, better color and depth.
- HDR10: HDR10 uses the wide-gamut Rec. 2020 color space. It sends static metadata via video stream to the TV which calibrates its screen brightness and color according to that. HDR10 supports 10-bit color which corresponds to 1024 shades of the primary RGB colors. It is technically limited to a maximum of 10,000 nits peak brightness, however common HDR10 contents are mastered with peak brightness from 1,000 to 4,000 nits.
Onkyo TX-NR646 offers multi-zone playback which allows you to play different input sources in 2 different rooms.
- Powered Zone 2: You can use the unit's 2 amplifier channels by connecting Zone 2 speakers directly to the speaker terminals. The remaining 5 channels will be left for main zone amplification.
- Audio Line Output: If you have a dedicated integrated amplifier for Zone 2 you can connect it to the a/v receiver via line outs by sending fixed signal and then control volume on the Zone 2 amplifier.
Inputs and Outputs
- Analog Line Inputs and Outputs: There are 7 line inputs and 1 line output for analog audio connection.
- Digital Inputs and Outputs: 1 optical input, 2 optical outputs and 1 coaxial input are available for digital audio connection.
- Headphone Output: There is a 6.3 mm (1/4") headphone output jack on the front panel.
- Inputs: 8 (1 front) Outputs: 2 (simultaneous)
8K Inputs: 0
- Composite Video: Connect you VCR, Laserdisc player and other old video equipment with composite video cables.
- Inputs: 3 Outputs: 0
- Component Video: Component video connection gives you the higher quality video compared to the composite video connection. So in case your old DVD player and other equipment do not have an HDMI output but have Component video output use this connection over the composite one. Onkyo TX-NR646 supports up to 480i/576i resolution on Component video connectors.
- Inputs: 2 Outputs: 0
Here we list all the available features and specifications of Onkyo TX-NR646.
|Front Wide Channel Support|
|WRAT (Wide Range Amplifier Technology)|
|VLSC (Vector Linear Shaping Circuitry)|
|Optimum Gain Volume Circuitry|
|Continuous 6 Ω Rated|
|Certified 4 Ω Performance|
|Discrete Output Stage Circuitry|
|3-Stage Inverted Darlington Circuitry|
|Independent Block Construction (Amp/Preprocessor)|
|BTL (Bridged Transless or Bridging)|
|Digital Signal Processing (DSP) Engine||Dual 32-bit DSP for Powerful Advanced Processing|
|DAC||Asahi Kasei AK4458|
|DAC Specs||384 kHz/32 Bit|
|Maximum Channel Processing||7.1|
|Air Studios Monitor Certification|
|Dolby Atmos||up to 5.1.2 after firmware update|
|Dolby Atmos Height Virtualization|
|Dolby Atmos Music|
|Dolby Digital Plus|
|Dolby Surround Upmixer|
|Dolby Pro Logic|
|DTS:X||up to 5.1.2 after firmware update|
|DTS Neural:X||after firmware update|
|DTS Neo||Neo:6 until firmware update|
|DTS-HD Master Audio|
|DTS-HD High Resolution Audio|
|Auro 3D with Auro-Matic Upmixer|
|Music Playback via USB||FLAC, WAV, Apple Lossless, WMA, WMA Lossless, Ogg, MP3, DSD, AAC, LPCM, Dolby TrueHD|
|High Resolution Music Playback via USB and/or Network||up to 96 kHz|
|High Resolution Audio Formats via USB||FLAC, WAV, WMA Lossless, Apple Lossless, DSD, AAC|
|DSD via HDMI||2-ch/Multi-ch Input|
|DSD via USB||2-ch Input|
|DSD to PCM Converter|
|Jitter Reduction||PLL (Phase Locked Loop) Jitter-Cleaning Circuit Technology for S/PDIF Audio|
|DTS Dialog Control|
|Dialog Level Adjustment||DTS:X only|
|Tone Control||Front L/R Channels|
|Compressed Music Enhancer||Advanced Music Optimizer (bluetooth included)|
|High-resolution Music Enhancer|
|THX Processing Mode|
|Audyssey Dynamic EQ|
|Audyssey Dynamic Volume|
|Audyssey Sub EQ HT|
|Phase-Matching Bass Boost||for Deep Bass and Clear Mid-Range|
|Pure Audio Mode|
|Pure Direct Analog Path Mode|
|Virtual Speakers||T-D (Theater-Dimensional)|
|Independent Subwoofer Outputs|
|Auto Speaker Calibration System with Mic.||AccuEQ Advance|
|HDCP Version||2.2 (3 inputs / 2 outputs)|
|HLG (Hybrid Log Gamma)|
|BT.2020 color space|
|QMS (Quick Media Switching)|
|ALLM (Auto Low Latency Mode)|
|VRR (Variable Refresh Rate)|
|QFT (Quick Frame transport)|
|Video Signal Passthrough||up to 4K/60p (RGB/YCbCr4:4:4/YCbCr4:2:2, 24 bit)|
|Video Signal Upscaling|
|Analog To HDMI Upconversion||Component**, Composite|
|Component Video Upscaling|
|Analog to Analog Video conversion|
|Component Video Maximum Resolution||480i/576i|
|isf Certified Calibration Control|
|Works with Amazon Alexa|
|Works with SONOS|
|Apple Product Connection||iPod, iPhone and iPad|
|Remote App||Onkyo Remote App for iPod touch/iPhone and Android-Powered Devices|
|InstaPrevue Input Source Prevue|
|HDMI Inputs||8 (1 front)|
|HDMI Outputs||2 (simultaneous)|
|USB Input||1 (Rear)|
|USB DC Out Port|
|RCA Line Input||7|
|RCA Line Output||1|
|XLR Line Inputs|
|Composite Video Input||3|
|Composite Video Output|
|Component Video Input||2|
|Component Video Output|
|Front A/V Inputs||HDMI|
|Headphone Out||6.3 mm (1/4")|
|Zone 2 Outs||RCA Line Out|
|Whole House Mode|
|+12V Trigger Output||0|
|Remote (IR) Input/Output||0 / 0|
|On-Screen Display||Graphical Overlaid On-Screen Display (OSD) via HDMI with Quick Set-Up|
|Detachable Power Cord|
|ONKYO-RI System Control|
|RIHD (Remote Interactive Over HDMI)|
|On Screen Remote Programming|
|Bi-directional Remote Setup via GUI|
|SiriusXM Internet Radio|
|Solid Aluminum Front|
|Large Speaker Terminals||9|
|Color-Coded Speaker Terminals|
|Transparent High-Grade Speaker Terminals|
|18mm Pitch High Grade Pre-outs|
|19mm-Pitch Audio Inputs|
|Gold plated RCA terminals|
|Power Supply||AC 120 V, 60 Hz|
|Independent Power Supply||2|
|H.C.P.S. (High Current Power Supply)||Massive High Power Transformer|
|Power Consumption||6.4 A|
|No Sound Power||70 W|
|Standby Power||0.1 W|
|Capacitor Bank||8,200 µF|
|ECO Mode / Hybrid Standby Function|
|Dimensions (W x H x D)||435 mm x 173.5 mm x 329 mm|
17-1/8" x 6-13/16" x 12-15/16"
|Weight||9.4 kg (20.7 lbs)|
|Power Output (8 Ω, 20 Hz - 20 kHz, 2||100 W (0.08% THD)|
|Power Output (6 Ω, 1 kHz, 1 channel driven, FTC)||170 W (0.9% THD)|
|Maximum Effective Power Output (6 Ω, 1 kHz, 1 channel driven, JEITA)||175 W|
|Rated Power Output (6 Ω, 1 kHz, 1 channel driven, IEC)||160 W (1% THD)|
|Dynamic Power per Channel (3 Ω, Front)||240 W|
|Dynamic Power per Channel (4 Ω, Front)||210 W|
|Dynamic Power per Channel (8 Ω, Front)||120 W|
|THD||0.08% (20 Hz - 20 kHz, Half power)|
|Damping Factor||60 (Front, 1 kHz, 8 Ω)|
|Input Sensitivity and Impedance (Line)||200 mV/47 kΩ (Line)|
|Input Sensitivity and Impedance (Phono MM)||3.5 mV/47 kΩ (Phono mm)|
|Phono Overload||70 mV (MM, 1 kHz 0.5% Direct)|
|S/N Ratio (Line, IHF-A)||100 dB|
|S/N Ratio (Phono MM, IHF-A)||80 dB|
|Frequency Response (Analog In)||10 Hz - 100 kHz/+1 dB, -3 dB (Direct mode)|
|DSD Sampling Rates via HDMI||2.8 MHz, 5.6 MHz|
|DSD Sampling Rates via USB||2.8 MHz, 5.6 MHz|
|Video Input Sensitivity/Output Level and Impedance||1 Vp-p/75 Ω (Component Y)|
0.7 Vp-p/75 Ω (Component PB/CB, PR/CR)
1 Vp-p/75 Ω (Composite)
|Video Frequency Response||5 Hz - 100 MHz/+0 dB, -3 dB (Component)|
|Wi-Fi Standard||IEEE 802.11 b/g/n|
|Wi-Fi Terminal Frequency||2.4 GHz|
|Bluetooth Version||2․1 + EDR|
|Bluetooth Frequency||2.4 GHz|
|USB Terminal||5 V, 1 A|
|FM Frequency||87.5 MHz - 107.9 MHz|
|AM Frequency||522/530 kHz - 1611/1710 kHz|
* - 480i/576i and 480p/576p only
** - 480i/576i only
*** - no 1080p/24 upconversion
**** - 1080p signal is not converted
In 2016 Onkyo TX-NR646 was replaced by TX-NR656. Let us now have a look at some important changes that the successor brought.
|UPGRADES||Onkyo TX-NR656||vs||Onkyo TX-NR646|
|VLSC (Vector Linear Shaping Circuitry)||Front L/R channels||vs|
|DTS Neural:X||after firmware update||vs||after firmware update|
|Higher Resolution Music Playback via USB||up to 192 kHz||vs||up to 96 kHz|
|High Resolution Audio Formats via USB||FLAC, WAV, Apple Lossless, DSD, AIFF, AAC, Dolby TrueHD||vs||FLAC, WAV, WMA Lossless, Apple Lossless, DSD, AAC|
|BT.2020 color space||vs|
|Video Signal Upscaling||1080p to 4K||vs|
|Front A/V Inputs||HDMI, Mini-Jack||vs||HDMI|
|Detachable Power Cord||vs|
|Bigger Power Supply||580 W||vs||6.4 A|
|Higher S/N Ratio (Line, IHF-A)||106 dB||vs||100 dB|
|Higher DSD Sampling Rate via USB||2.8 MHz, 5.6 MHz||vs||2.8 MHz, 5.6 MHz|
|Wi-Fi Standard||IEEE 802.11 a/b/g/n||vs||IEEE 802.11 b/g/n|
|Wi-Fi Terminal Frequency||5 GHz, 2.4 GHz||vs||2.4 GHz|
|Newer Bluetooth Version||4․1 + LE||vs||2․1 + EDR|
|DOWNGRADES||Onkyo TX-NR656||vs||Onkyo TX-NR646|
|Music Playback via USB||FLAC, WAV, Apple Lossless, WMA, MP3, DSD, AIFF, AAC, Dolby TrueHD||vs||FLAC, WAV, Apple Lossless, WMA, WMA Lossless, Ogg, MP3, DSD, AAC, LPCM, Dolby TrueHD|
|InstaPrevue Input Source Prevue||vs|
|Less RCA Line Outputs||vs||1|
|Less Composite Video Inputs||2||vs||3|
|ONKYO-RI System Control||vs|
|SiriusXM Internet Radio||vs|
|Independent Power Supply||vs||2|
|Lower DSD Sampling Rate via HDMI||2.8 MHz||vs||2.8 MHz, 5.6 MHz|
|Narrower AM Frequency Range||530 kHz - 1710 kHz||vs||522/530 kHz - 1611/1710 kHz|
For more detailed comparison between the models please visit Onkyo TX-NR646 vs Onkyo TX-NR656.