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Vizio M Series M21d-H8R vs Vizio M Series M51ax-J6
Side-by-Side Comparison
Products
Vizio M Series M21d-H8R
Vizio M Series M51ax-J6
Tested using Methodology v1.0
Updated Jan 12, 2024 03:54 PM
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Amazon.comTested using Methodology v1.3
Updated Sep 04, 2024 06:58 PM
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Amazon.com
Channels2.1
Channels5.1
Variants
- M-Series M21d-H8R (Black)
- M Series M51ax-J6 (Dark Charcoal)
Our Verdict
Vizio M Series M21d-H8R
Vizio M Series M51ax-J6
The Vizio M Series M51ax-J6 and the Vizio M-Series M21d-H8R are very different soundbar setups. The M21d-H8R is a 2.1 standalone soundbar that's ideal for listening to vocal-centric content like TV shows. That said, the M51ax-J6 is better overall. It's a 5.1 bar with Dolby Atmos support that can reproduce a more extended low bass thanks to its dedicated sub. Its satellites offer a better surround performance, too, and it has a better soundstage.
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Black
M-Series M21d-H8R
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Amazon.comDark Charcoal
M Series M51ax-J6
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Amazon.comBlack
M-Series M21d-H8R
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M Series M51ax-J6
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M-Series M21d-H8R
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Walmart.comDark Charcoal
M Series M51ax-J6
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M-Series M21d-H8R
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M Series M51ax-J6
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Walmart.comMain Differences forMixed Usage
Mixed Usage
Threshold
Mixed Usage
6.8
7.9
Height (Atmos)
0.0
5.9
Stereo Frequency Response
7.3
7.9
Stereo Dynamics
6.5
8.5
Surround 5.1
4.4
7.5
Center
6.7
8.4
Full Comparison
Design
Style - Bar
Style photo - bar
Style - Subwoofer
Style photo - sub
Sub Wireless
No
Yes
Enclosure
Integrated
Ported
Style - Satellites
Style photo - satellites
Satellite Wireless
No
Partial, wired to wireless sub
Dimensions - Bar
Dimensions photo - bar
Width
36.0" (91.5 cm)
36.0" (91.5 cm)
Height
2.2" (5.7 cm)
2.3" (5.8 cm)
Depth
5.3" (13.5 cm)
3.5" (9.0 cm)
Dimensions - Subwoofer
Dimensions photo - sub
Width
N/A
8.3" (21.0 cm)
Height
N/A
9.9" (25.2 cm)
Depth
N/A
8.3" (21.0 cm)
Dimensions - Satellites
Dimensions photo - satellites
Width
N/A
5.7" (14.6 cm)
Height
N/A
2.3" (5.8 cm)
Depth
N/A
3.5" (9.0 cm)
Mounting
Bar Mounting Holes
Satellite Mounting Holes
Mountable Bar
Yes
Bar Brackets Included
Yes
Mountable Satellites
Yes
Satellite Brackets Included
Yes
Build Quality
7.5
7.0
Build quality photo
In The Box
In The Box photo
HDMI Cable Length
1.5 m (4.9 ft)
Digital Optical Cable Length
1.5 m (4.9 ft)
Back - Bar
Back photo - bar
Bar Mounting
Proprietary
Back - Subwoofer
Back photo - sub
Enclosure
Integrated
Ported
Back - Satellites
Back photo - satellites
Mounting
No
Sound
Stereo Frequency Response
7.3
7.9
Stereo Setup
Raw Frequency Response
Frequency Response Small
Channels
2.1
5.1
Tested Preset
Music
Direct
Slope
-0.44
-0.26
Standard Error
2.64 dB
3.35 dB
Low-Frequency Extension
53.4 Hz
33.6 Hz
High-Frequency Extension
19.9 kHz
19.9 kHz
Stereo Frequency Response With Preliminary Calibration
7.3
8.2
Frequency Response Calibrated
Suggested Preset
Music
Direct
Suggested Bass Setting
-2
-3
Suggested Treble Setting
2
0
Slope
0.05
-0.11
Standard Error
2.56 dB
2.37 dB
Low-Frequency Extension
54.2 Hz
33.2 Hz
High-Frequency Extension
19.9 kHz
19.6 kHz
Stereo Soundstage
6.5
7.0
Crosstalk Error
3.37 dB
2.16 dB
Stereo Dynamics
6.5
8.5
Dynamic Range Compression
SPL @ Max Volume
96.2 dB SPL
96.2 dB SPL
DRC @ 90dB
0.25 dB
DRC @ Max Volume
4.88 dB
1.40 dB
Stereo Total Harmonic Distortion
8.1
Weighted THD @ 80dB
0.29
Weighted THD @ Max Volume
1.46
Center
6.7
8.4
Center Setup
Frequency Response
Localization
Phantom
Discrete
Slope
-0.72
-0.21
Std. Err.
3.06 dB
2.67 dB
SPL @ Max Volume
92.9 dB SPL
92.4 dB SPL
Weighted THD @ 80dB
0.37
1.17
Weighted THD @ Max Volume
1.50
2.09
Surround 5.1
4.4
7.5
Surround Setup
Frequency Response
Localization
Stereo (Downmix)
Discrete
Slope
-0.66
-0.17
Std. Err.
2.86 dB
4.01 dB
SPL @ Max Volume
94.6 dB SPL
93.3 dB SPL
Weighted THD @ 80dB
0.32
0.34
Weighted THD @ Max Volume
1.55
1.02
7.1 Rears
No
No
Height (Atmos)
0.0
5.9
Height Setup
H Frequency Response
Localization
Not Supported
Phantom (Front Firing, Satellites)
Slope
N/A
-0.06
Std. Err.
N/A
3.99 dB
SPL @ Max Volume
N/A
85.1 dB SPL
Weighted THD @ 80dB
N/A
2.60
Weighted THD @ Max Volume
N/A
0.32
Sound Enhancement Features
4.6
7.1
Room Correction
No
No
Dialogue Enhancement
Yes
Yes
Auto-Volume/Night Mode
Yes
Yes
Subwoofer Level Adjustment
No
Yes
Bass Adjustment
Yes
Yes
Treble Adjustment
Yes
Yes
EQ
Presets
Presets
Surround Level Adjustment
No
Yes
Rear Level Adjustment
No
No
Height Level Adjustment
No
No
Virtual Surround
Yes
Yes
Connectivity
Inputs/Outputs - Bar
Physical Connections Bar Photo 1
Physical Connections Bar Photo 2
Optical Audio In
1
1
HDMI Out
1 (shared)
eARC
HDMI 2.1 Class Bandwidth
No
Full HDMI In
1
1
Analog Audio In 3.5mm (Aux)
1
1
RCA In
No
No
USB for Files
1
1
Ethernet
No
No
Subwoofer Output
No
HDMI ARC
1 (shared)
Audio Format Support: ARC/eARC
7.1
10
Dolby Atmos
No
Supported
Dolby Digital
Yes
Supported
Dolby Digital Plus
No
Supported
Dolby TrueHD
No
Supported
DTS
Yes
Supported
DTS:X
No
Supported
eARC
No
DTS-HD MA
No
Supported
PCM Channels
Up To 7.1
5.1 PCM (eARC only)
No
Audio Format Support: HDMI In
6.4
10
Dolby Atmos
No
Supported
Dolby Digital
Yes
Supported
Dolby Digital Plus
No
Supported
Dolby TrueHD
No
Supported
DTS
No
Supported
DTS:X
No
Supported
DTS-HD MA
No
Supported
PCM Channels
Up To 7.1
5.1 PCM
No
Audio Format Support: Optical
10
10
Dolby Digital
Yes
Supported
DTS
Yes
Supported
PCM Channels
2.0
Audio Latency: ARC
9.5
ARC Latency Video
PCM-2.0 ch
61 ms
PCM-5.1 ch
106 ms
Dolby MAT (PCM) Atmos
76 ms
Dolby Digital
65 ms
Dolby Digital Plus
70 ms
Dolby Digital Plus Atmos
74 ms
Audio Latency: HDMI In
5.0
6.9
HDMI Latency Video
Latency Video
PCM-2.0 ch
97 ms
PCM-5.1 ch
87 ms
Dolby MAT (PCM) Atmos
107 ms
Dolby Digital
124 ms
Dolby Digital Plus
115 ms
Dolby Digital Plus Atmos
122 ms
ARC
195 ms
Optical
179 ms
Full HDMI In
49 ms
Audio Latency: Optical
7.0
Optical Latency Video
PCM-2.0 ch
147 ms
Dolby Digital
207 ms
Video Passthrough To TV
0.0
9.0
1080p Max Refresh Rate
120Hz
1080p @ 4:4:4 Max Refresh Rate
120Hz
4k Max Refresh Rate
120Hz
4k @ 120Hz @ 10-Bit
Not Supported
4k @ 4:4:4 Max Refresh Rate
60Hz
8k Max Refresh Rate
30Hz
HDR10 Passthrough
Yes
Yes
HDR10+ Passthrough
Yes
Dolby Vision Passthrough
Yes
HDMI Forum VRR Passthrough
Yes
4k @ 60 Hz Passthrough
Yes
FreeSync Passthrough
No
G-SYNC Passthrough
No
ALLM Passthrough
Yes
4k @ 60 Hz @ 10 bit Passthrough
Yes
4k @ 60 Hz @ 4:4:4 Passthrough
Yes
Wireless Playback
6.0
6.0
Bluetooth
Yes
Yes
Wi-Fi Playback
No
No
Chromecast built-in
No
No
Apple AirPlay
No
No
Spotify Connect
No
Connectivity - Subwoofer
Physical inputs subwoofer photo 1
Physical controls subwoofer photo 1
Sub Wireless
No
Yes
Connectivity - Satellites
Physical inputs satellites photo 1
Physical controls satellites photo 1
Sat Wireless
No
Partial, wired to wireless sub
Additional Features
Interface
Interface photo
Display
No
No
Bar Controls
Controls photo
Remote
Remote photo
Universal Remote
No
Voice Assistants Support
Amazon Alexa
No
No
Google Assistant
No
No
Apple Siri
No
No
Microphone Mute
No
App
App image
App Name
No App
iOS
No
Android
No
Acts As A Remote
No
Controls Soundbar's Settings
No
Casts Device Files
No
Other Features
Power Saving
Auto-off
HDMI CEC (TV Remote Control)
Yes
Check Price
Black
M-Series M21d-H8R
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Amazon.comDark Charcoal
M Series M51ax-J6
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Amazon.comBlack
M-Series M21d-H8R
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BestBuy.comDark Charcoal
M Series M51ax-J6
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B&HBlack
M-Series M21d-H8R
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Walmart.comDark Charcoal
M Series M51ax-J6
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BestBuy.comBlack
M-Series M21d-H8R
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B&HDark Charcoal
M Series M51ax-J6
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Walmart.com
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Vizio M Series M21d-H8R vs Vizio M Series M51ax-J6: Main Discussion
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