Onkyo TX-NR646 Review and Specs
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Onkyo TX-NR646 (Others version)

SCORE:
82

Highlights

  • 7.2 channels
  • 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 Overview

Onkyo TX-NR646 was introduced in 2015. It is equipped with 7 channel amplifier and is capable of 7.1 maximum channel processing.

We evaluated the Receiver and gave 82 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.

AMPLIFIER
88
VIDEO FEATURES
77
AUDIO FEATURES
85
CONNECTIVITY
83
MULTIZONE
77
MISCELLANEOUS
66
RADIO
91
OVERALL
82

Amplifier score is based on power ratings, minimum impedance load, power supply, transformer type, total harmonic distortion, damping factor, signal to noise ratio and other small details. Audio score depends on the number of channels, front wide channel support, maximum channel processing, support of audio formats, DAC specifications, room calibration algorithm... Video score is based on HDR, Dolby Vision and video signal passthrough and upscaling, analog to HDMI upconversion. Connectivity score is defined from all wired and wireless inputs and outputs, internet and bluetooth connections, HEOS, SONOS and others. Multizone score depends on the number of zones with their outputs. Radio score is evaluated form digital radio support and analog tuner with its frequency range, signal to noise ratio, harmonic distortion...

Pros and Cons

In this section we present pros and cons of Onkyo TX-NR646.

PROS
Certified 4 Ω Performance πŸ‘
Bi-amp Capability πŸ‘
Dolby Atmos πŸ‘
Dolby TrueHD πŸ‘
Dolby Digital Plus πŸ‘
Dolby Surround Upmixer πŸ‘
DTS:X πŸ‘
DTS Neo πŸ‘
DTS-HD Master Audio πŸ‘
DTS-HD High Resolution Audio πŸ‘
DTS 96/24 πŸ‘
DTS Express πŸ‘
DTS-ES πŸ‘
High Resolution Music Playback via USB and/or Network πŸ‘
Gapless Playback πŸ‘
DSD via HDMI πŸ‘
DSD via USB πŸ‘
DTS Dialog Control πŸ‘
Dialog Level Adjustment πŸ‘
Compressed Music Enhancer πŸ‘
Phase-Matching Bass Boost πŸ‘
Auto Speaker Calibration System with Mic. πŸ‘
HDR10 πŸ‘
3-D Ready πŸ‘
4K or 8K Video Passthrough πŸ‘
Analog To HDMI Upconversion πŸ‘
DLNA 1.5 πŸ‘
Ethernet πŸ‘
Wi-Fi πŸ‘
Bluetooth πŸ‘
New HDCP Version πŸ‘
Many HDMI Inputs πŸ‘
USB Input πŸ‘
Many Analog Audio Line Inputs πŸ‘
Phono Input πŸ‘
Composite Video Inputs πŸ‘
Component Video Inputs πŸ‘
Zones πŸ‘
Analog Tuner πŸ‘
Pandora πŸ‘
Spotify πŸ‘
Deezer πŸ‘
Independent Power Supply πŸ‘
H.C.P.S. (High Current Power Supply) πŸ‘
CONS
No Front Wide Channel Support πŸ‘Ž
No Dolby Atmos Height Virtualization πŸ‘Ž
No DTS Neural:X πŸ‘Ž
No DTS Virtual:X πŸ‘Ž
No IMAX Enhanced πŸ‘Ž
No Auro 3D with Auro-Matic Upmixer πŸ‘Ž
No High-resolution Music Enhancer πŸ‘Ž
No HDR10+ πŸ‘Ž
No BT.2020 color space πŸ‘Ž
No Dolby Vision πŸ‘Ž
No Hybrid Log Gamma (HLG) πŸ‘Ž
No 4K or 8K Video Upscaling πŸ‘Ž
No Chromecast Built-In πŸ‘Ž
Does not Work with Amazon Alexa πŸ‘Ž
Does Not Work with SONOS πŸ‘Ž
No eARC πŸ‘Ž
No Multi-Channel Input πŸ‘Ž
No Analog Pre-Outs πŸ‘Ž
No Tidal πŸ‘Ž
No Napster πŸ‘Ž
No SiriusXM Internet Radio πŸ‘Ž
Old Bluetooth Version πŸ‘Ž

Major Changes from its predecessor

Here we are comparing Onkyo TX-NR646 to its predecessor TX-NR636 and displaying the major changes.

UPGRADES Onkyo TX-NR646 Onkyo TX-NR636
Dolby Surround Upmixer βœ” βœ–
DTS:X βœ” up to 5.1.2 after firmware update βœ–
DTS Dialog Control βœ” βœ–
More Advanced Auto Speaker Calibration System βœ” Advanced AccuEQ βœ” AccuEQ
HDR10 βœ” βœ–
AirPlay βœ” AirPlay βœ” AirPlay via optional Onkyo RI Dock DS-A5 (sold separately)
More HDMI Inputs 8 (1 front) 7 (1 front)
More Analog Audio Line Inputs 7 6
More Analog Audio Line Outputs 1 βœ–
More Optical Inputs 2 1
More Component Video Inputs 2 1
Deezer βœ” βœ–

DOWNGRADES Onkyo TX-NR646 Onkyo TX-NR636
Surround EX βœ– βœ” also known as Dolby Digital Surround EX
Video Signal Upscaling βœ– βœ” up to 4K/30p (Marvell Qdeo)
MHL Input βœ– βœ” Front HDMI
Less Coaxial Inputs/Outputs 1 / βœ– 2 / βœ–
Less Composite Video Outputs βœ– 1
Less Component Video Outputs βœ– 1

For more detailed comparison between the models please visit Onkyo TX-NR646 vs Onkyo TX-NR636.

Selected Features

Amplifier

Onkyo TX-NR646 has 7 channel amplifier and delivers 100 W (8 Ω, 20 Hz - 20 kHz, 2 channel driven) and also has a stable performance at 4 Ω load.


Video Features

The Receiver has 4K passthrough up to 60p. It can bypass HDR10.


HDR10

High-dynamic-range (HDR) video has greater dynamic range than standard-dynamic-range (SDR) video with brigter whites and deeper blacks. HDR10 was announced on August 27, 2015, by the Consumer Technology Association and 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 up to 1000 nits of brightness and 10-bit color which corresponds to 1024 shades of the primary RGB colors.


Dolby Atmos and Dolby Surround upmixer

Onkyo TX-NR646 supports Dolby Atmos with its Dolby Surround upmixer. It can be configured upto 5.1.2 channels using internal amplifiers.

Dolby Atmos is the first cinematic audio format in which sounds exist as individual entities, called audio objects. In Dolby Atmos, any sound - the helicopter, a car screeching around a corner, a melodic bird call - 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. You'll feel like you're inside the action, in ways you've never experienced before.

Dolby Atmos for the home represents every sound in the original cinema mix as an audio object. Extensions to the Dolby Audioβ„’ codecs, along with an advanced scalable algorithm, allow Dolby Atmos to be delivered via Blu-ray Disc and streaming media. A spatially-coded substream is added to Dolby TrueHD or Dolby Digital Plus. A Dolby Atmos audio/video receiver (AVR) adapts the cinema experience to your home theater from seven speakers to as many as 34 in 24.1.10 configuration, recreating the original artistic concept. 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.

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.


DTS:X and Neural:X upmixer

Onkyo TX-NR646 supports DTS:X. It can be configured upto 5.1.2 channels using internal amplifiers.

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 Neural:X is a new upmixer that can take non DTS:X content and upmix it to the DTS:X speaker layout. It has replaced the DTS Neo family with improved flexibility.


WRAT

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.


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.


Phase-Matching Bass Boost

Onkyo TX-NR646 features Phase-Matching Bass Boost. The negative effects of phase-shift or the timing difference between sound waves of different frequencies can sometimes be heard in audio players when corners are cut in order to increase bass response. While most audio systems have some form of low-frequency enhancement system, often a bigger bass sound comes at the expense of mid-range clarity, and results in a smeared or muddy sound. Onkyo’s Phase-Matching Bass Boost technology avoids this problem by improving the phase timing to preserve the natural clarity of the mid-range allowing vocals and strings to shine while maintaining a smooth, powerful bass response at all volume levels.


Room Correction

Onkyo TX-NR646 comes with[y] Advanced AccuEQ room correction system and includes the calibration microphone.


Connectivity

Onkyo TX-NR646 can be connected to internet using ethernet cable or built-in wi-fi adapter. It can also connect to bluetooth devices via built-in bluetooth adapter. The Receiver supports[y] AirPlay. It has 8 HDMI inputs and HDCP 2.2 (3 in / 2 out) copy protection. There is a phono input with built-in phono stage for connecting the cartridge output of the turntable directly to the Receiver.

Front panel has HDMI input.

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Detailed Specifications

Here we list all the available features and specifications of Onkyo TX-NR646.

BASICS
BrandOnkyo
ModelTX-NR646
TypeA/V Receiver
CountryOthers
Release Year2015
AMPLIFIER
Channels7.2
Front Wide Channel Supportβœ–
WRAT (Wide Range Amplifier Technology)βœ”
VLSC (Vector Linear Shaping Circuitry)βœ–
Optimum Gain Volume Circuitryβœ”
THXβ„’ Certificationβœ–
Continuous 6 Ω Ratedβœ”
Certified 4 Ω Performanceβœ”
Discrete Output Stage Circuitryβœ”
3-Stage Inverted Darlington Circuitryβœ–
PUSH-PULL Designβœ–
Independent Block Construction (Amp/Preprocessor)βœ–
Bi-amp Capabilityβœ”
BTL (Bridged Transless or Bridging)βœ–
AUDIO
Digital Signal Processing (DSP) EngineDual 32-bit DSP for Powerful Advanced Processing
DACAsahi Kasei AK4458
Maximum Channel Processing7.1
Air Studios Monitor Certificationβœ–
Dolby Atmosβœ” up to 5.1.2 after firmware update
Dolby Atmos Height Virtualizationβœ–
Dolby TrueHDβœ”
Dolby Digital Plusβœ”
Dolby Surround Upmixerβœ”
Dolby Pro Logicβœ–
Surround EXβœ–
DTS:Xβœ” up to 5.1.2 after firmware update
DTS Neural:Xβœ” after firmware update
DTS Virtual:Xβœ–
DTS Neoβœ” Neo:6 until firmware update
DTS-HD Master Audioβœ”
DTS-HD High Resolution Audioβœ”
DTS 96/24βœ”
DTS Expressβœ”
DTS-ESβœ”
IMAX Enhancedβœ–
Auro 3D with Auro-Matic Upmixerβœ–
PCMβœ” 2-ch/Multi-ch Input
Music Playback via USBFLAC, WAV, Apple Lossless, WMA, WMA Lossless, Ogg, MP3, DSD, AAC, LPCM, Dolby TrueHD
High Resolution Music Playback via USB and/or Networkβœ” up to 96 kHz
High Resolution Audio Formats via USBFLAC, WAV, WMA Lossless, Apple Lossless, DSD, AAC
Multi-Channel Music File Playback via USBβœ–
Gapless Playbackβœ”
DSD via HDMIβœ” 2-ch/Multi-ch Input
DSD via USBβœ” 2-ch Input
DSD to PCM Converterβœ–
USB DACβœ–
Jitter Reductionβœ” PLL (Phase Locked Loop) Jitter-Cleaning Circuit Techβœ– logy for S/PDIF Audio
DTS Dialog Controlβœ”
Dialog Enhancementβœ–
Dialog Level Adjustmentβœ” DTS:X only
Dialog Normalizationβœ–
Dialogue Liftβœ–
Tone Controlβœ” Front L/R Channels
Compressed Music Enhancerβœ” Advanced Music Optimizer (bluetooth included)
High-resolution Music Enhancerβœ–
THX Processing Modeβœ–
Audyssey Dynamic EQβœ–
Audyssey Dynamic Volumeβœ–
Audyssey LFCβœ–
Audyssey Sub EQ HTβœ–
Audyssey DSXβœ–
Phase-Matching Bass Boostβœ” for Deep Bass and Clear Mid-Range
Direct Modeβœ”
Pure Audio Modeβœ–
Pure Direct Analog Path Modeβœ–
Virtual Speakersβœ” T-D (Theater-Dimensional)
Independent Dual Subwoofer Outputβœ–
CALIBRATION
Auto Speaker Calibration System with Mic.βœ” Advanced AccuEQ
VIDEO
HDR10βœ”
HDR10+βœ–
Dynamic HDRβœ–
BT.2020 color spaceβœ”
Dolby Visionβœ–
Hybrid Log Gamma (HLG)βœ–
Quick Media Switching (QMS)βœ–
Auto Low Latency Mode Pass-throughβœ–
Variable Refresh Rate (VRR)βœ–
Quick Frame Transport (QFT)βœ–
3-D Readyβœ”
Video Signal Passthroughup to 4K/60p (RGB/YCbCr4:4:4/YCbCr4:2:2, 24 bit)
Video Signal Upscalingβœ–
Analog To HDMI Upconversionβœ” Component**, Composite
Component Video Upscalingβœ–
Analog to Analog Video conversionβœ–
Component Video Maximum Resolution480i/576i
isf Certified Calibration Controlβœ–
CONNECTIVITY
MHL Inputβœ–
DLNA 1.5βœ”
FireConnectβœ–
FlareConnectβœ–
Chromecast Built-Inβœ–
DTS Play-Fiβœ–
Works with Amazon Alexaβœ–
Works with SONOSβœ–
AirPlayβœ” AirPlay
Apple Product Connectionβœ” iPod, iPhone and iPad
Remote AppOnkyo Remote App for iPod touch/iPhone and Android-Powered Devices
InstaPrevue Input Source Prevueβœ”
Ethernetβœ”
Ethernet Switchβœ–
Wi-Fiβœ”
Bluetoothβœ”
HDBaseT Compatibleβœ–
Enhanced ARCβœ–
HDCP Version2.2 (3 in / 2 out)
HDMI Input8 (1 front)
HDMI Output2 (simultaneous)
USB Input1 (Rear)
USB DC Out Portβœ–
Analog Audio Line Input7
Analog Audio Line Output1
Phono Inputβœ”
Optical In2
Optical Outβœ–
Coaxial In/Out1 / βœ–
Composite Video Input3
Composite Video Outputβœ–
S-Video Inputβœ–
S-Video Outputβœ–
Component Video Input2
Component Video Outputβœ–
PC Inβœ–
Multi-Channel Inputβœ–
Analog Pre-Outs0.2
XLR Inputsβœ–
XLR Pre-outsβœ–
Front A/V InputsHDMI
Speaker A/Bβœ–
Headphone Outβœ” 6.3 mm
ZONES
Zones2
Powered Zonesβœ” 2
Zone 2RCA Line Out
Whole House Modeβœ–
RS-232βœ–
+12V Trigger Output0
Remote (IR) Input/Output0 / 0
MISC
On-Screen Displayβœ” Graphical Overlaid On-Screen Display (OSD) via HDMI with Quick Set-Up
Detachable Power Cordβœ–
uportβœ–
ONKYO-RI System Controlβœ”
RIHD (Remote Interactive Over HDMI)βœ”
Pre-Pro/Learning Remoteβœ” / βœ–
On Screen Remote Programmingβœ”
Bi-directional Remote Setup via GUIβœ–
Smart Grid-Readyβœ”
RADIO
Analog Tunerβœ” FM/AM with RDS
Presets40
Digital Radioβœ–
Internet Radioβœ” TuneIn
Pandoraβœ”
Spotifyβœ”
Tidalβœ–
Deezerβœ”
Napsterβœ–
SiriusXM Internet Radioβœ–
CONSTRUCTION
Solid Aluminum Frontβœ–
Speaker Terminals9
Large Speaker Terminals9
Color-Coded Speaker Terminalsβœ–
Transparent High-Grade Speaker Terminalsβœ–
18mm Pitch High Grade Pre-outsβœ–
19mm-Pitch Audio Inputsβœ–
Gold plated RCA terminalsβœ–
POWER
Power SupplyAC 220-240 V, 50/60 Hz
Independent Power Supply2
H.C.P.S. (High Current Power Supply)βœ” Massive High Power Transformer
Toroidal Transformerβœ–
Power Consumption630 W
No Sound Power70 W
Standby Power0.15 W
Capacitor Bank8,200 Β΅F
GENERAL
ECO Mode / Hybrid Standby Functionβœ”
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"
Weight9.8 kg (21.6 lbs)
Warranty2 Years
SPECS
Power Output (8 Ω, 20 Hz - 20 kHz, 2100 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
THD0.08% (20 Hz - 20 kHz, Half power)
Damping Factor60 (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 Overload70 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 HDMI2.8 MHz, 5.6 MHz
DSD Sampling Rates via USB2.8 MHz, 5.6 MHz
Video Input Sensitivity/Output Level and Impedance1 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 Response5 Hz - 100 MHz/+0 dB, -3 dB (Component)
Ethernet Standard10BASE-T/100BASE-TX
Wi-Fi StandardIEEE 802.11 b/g/n
Wi-Fi Terminal Frequency2.4 GHz
Bluetooth Version2.1 + EDR
Bluetooth Frequency2.4 GHz
USB Terminal5 V, 1 A
FM Frequency87.5 MHz - 108.0 MHz
AM Frequency522/530 kHz - 1611/1710 kHz

* - 480i/576i and 480p/576p only
** - 480i/576i only
*** - no 1080p/24 upconversion
**** - 1080p signal is not converted

Successor

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 Onkyo TX-NR646
DTS Neural:X βœ” after firmware update βœ” after firmware update
Higher Resolution Music Playback via USB βœ” up to 192 kHz βœ” up to 96 kHz
BT.2020 color space βœ” βœ”
Dolby Vision βœ” βœ–
Video Signal Upscaling βœ” 1080p to 4K βœ–
FireConnect βœ” βœ–
FlareConnect βœ” βœ–
Chromecast Built-In βœ” βœ–
Tidal βœ” βœ–
Higher DSD Sampling Rate via USB 2.8 MHz, 5.6 MHz 2.8 MHz, 5.6 MHz
Wi-Fi Standard IEEE 802.11 a/b/g/n IEEE 802.11 b/g/n
Newer Bluetooth Version 4.1 + LE 2.1 + EDR

DOWNGRADES Onkyo TX-NR656 Onkyo TX-NR646
Certified 4 Ω Performance βœ– βœ”
Less Analog Audio Line Outputs βœ– 1
Less Composite Video Inputs 2 3
Analog Tuner βœ” FM/AM βœ” FM/AM with RDS
Independent Power Supply βœ– 2
Smaller Power Supply 580 W 630 W

For more detailed comparison between the models please visit Onkyo TX-NR656 vs Onkyo TX-NR646.

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