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Denon AVR-X6700H Home Theater AVR Review

amirm

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#1
This is a review and detailed measurements of the Denon AVR-X6700H "8k" 11.2 channel Audio/Video Receiver. It is kindly loaned to me by a local member and costs US $2,499 on Amazon with free shipping.

AVRs look the same these days and the AVR-X6700H is no exception:

AVR-X6700H AVR Surround HDMI Dolby Atmos Home Theater Receiver Review.jpg


Inside though, is quite full as indicate by large number of amplifications with speaker terminals in the back:

AVR-X6700H AVR Surround HDMI Dolby Atmos Home Theater Receiver Back Panel Inputs Outputs Review.jpg


I did not invoke the ECO mode. Without it, the unit runs quite warm. Some instrumentation on this later.

I tested the 6700H a couple of weeks ago and found what I considered performance issues. I ran the subset of those measurements by Denon. They examined them and confirmed that the measurements are correct for the unit I have and is due to capacitor substitution. They provided me with this statement to share with you:

“Denon is pleased to work with ASR once again, who kindly shared his Denon AVR-X6700H measurement results with Denon engineering. The initial results ASR shared were surprising and prompted an investigation, which resulted in Denon engineering identifying measurement irregularities caused by a particular capacitor used in the initial production run to mitigate a supply issue caused by the COVID-19 pandemic. The latest production units have the capacitor Denon typically uses, which does not show the same measurement results.

Even with the previous production units affected by the capacitor constraint, Denon sound masters approved the audio quality in the initial AVR-X6700H production run and we’re confident it sounds just as good as the latest production units. However, if you purchased a Denon AVR-X6700H and have concerns, please reach out to Denon customer support after August 5, 2020 and we will verify if your unit is affected and offer a replacement if merited. “

They will be sending me a newer unit without this issue for testing in the future. I will be updating this review when I get that sample and test it.

AVR DAC Audio Measurements
As usual we start by feeding the AVR over HDMI a 1 kHz tone and see how much noise, distortion and unwanted signals are present in the pre-amp output. I set the volume to 82.5 which produces the nominal 2 volt we see from stereo DACs (see later for performance at other levels):

AVR-X6700H AVR Audio Measurements.png


Note that the amplifier for the two channels being tested is turned off to avoid its clipping behavior impacting the DAC portion. We see a distortion spike rising up to -88 dB which is high enough to dictate SINAD which is a sum of noise and distortion to the same level. This is quite a regression relative to AVR-X4700H to the tune of 8 dB.

I tested using Coax and got the same performance so this is not HDMI channel mixing issue we have dealt with before.

While troubleshooting this behavior, I noticed that the level of distortion varies with time. See this second measurement for example:

AVR-X6700H AVR Audio Measurements Capture 2.png


So I powered the unit down, let it cool some and then measured SINAD over time:

AVR-X6700H AVR Audio Warm-up.png


The instant the test is started, SINAD is nearly 90 dB but drops after a minute or so to 86 dB.

As noted, Denon engineering traced this to a faulty capacitor in early units (I provided the serial number for this sample and they confirmed that it does use this faulty cap).

Running with what we have, this is the ranking then:

Best home theater AVR DAC Review 2020.png


We are now in the "red" category of DACs which I don't consider to be good. The AVR-X3600 from last year now enjoys a commanding lead, bettering the AVR-X6700H by a whopping 12 dB. Hopefully the manufacturing fix narrows and closes this gap.

Lowering the output level does not change the equation much:
AVR-X6700H AVR THD+N vs Level.png


Here is our signal to noise ratio:
AVR-X6700H AVR Surround HDMI Dolby Dynamic Range Measurement.png


Intermodulation test vs level shows a saturation problem as early as -20 dB:
AVR-X6700H AVR Surround HDMI Dolby Atmos DAC IMD vs Level Measurement.png


32-tone test resembling "music" shows dramatic increase in intermodulation distortion as frequencies rise: (label should say 6700)

AVR-X6700H AVR Surround HDMI Dolby Atmos DAC Multitone Measurement.png


This manifests itself in THD+N versus frequency just as well: (label should say 6700H)

AVR-X6700H AVR Surround HDMI Dolby Atmos DAC THD+N vs Frequency Measurement.png


Unimpressive out of band filtering in the DAC contributes to above: (label should say 6700H):
AVR-X6700H AVR Surround HDMI Dolby Atmos DAC Filter Measurement.png


On less depressing note, Jitter performance is good:

AVR-X6700H AVR Surround HDMI Dolby Atmos DAC Jitter Measurement.png


Linearity suffers from secondary power supply tone close to test frequency of 200 Hz:

AVR-X6700H AVR Surround HDMI Dolby Atmos DAC Linearity Measurement.png


AVR Analog Input Amplifier Measurements
The CD input on Denon AVRs is not digitized which makes for a good input to test the amplifier's raw performance outside of digital processing:

AVR-X6700H AVR Surround HDMI Dolby Atmos Amplifier CD Input Measurement.png


This is above average performance for all amplifiers tested regardless of type:
Best stereo multichannel amplifier review 2020.png


Within AVRs, it lands in the crowded middle:

best AVR amplifier review 2020.png


Frequency response is flat and bandwidth quite wide:

AVR-X6700H AVR Surround HDMI Dolby Atmos Amplifier CD Input Frequency Response Measurement.png


Crosstalk is reasonable:
AVR-X6700H AVR Surround HDMI Dolby Atmos Amplifier CD Input Crosstalk Measurement.png


Signal to noise ratio could be better at 5 watts (like to see 16 bits of dynamic range there):

AVR-X6700H AVR Surround HDMI Dolby Atmos Amplifier CD Input SNR Measurement.png


The most important measurement here is power output so let's get into that using 4 ohm load driving 2 channels simultaneously:

AVR-X6700H AVR Surround HDMI Dolby Atmos Amplifier CD Input Power into 4 ohm Measurement.png


Lots of power at 180 watts. One channel has worse distortion though.

Allowing for more distortion at 1% we get this much max and short-term power outputs:

AVR-X6700H AVR Surround HDMI Dolby Atmos Amplifier CD Input Peak Max Power into 4 ohm Measurem...png


That's 600 watts of short-term power which is nice! You get a benefit from a power supply that is designed to drive a lot more channels than two in this test.

Switching to 8 ohm we get:

AVR-X6700H AVR Surround HDMI Dolby Atmos Amplifier CD Input Power into 8 ohm Measurement.png


Rated spec is at higher distortion than I allow so we are good here.

Edit: forgot to include this measurement in the original review:

AVR-X6700H AVR Surround HDMI Dolby Atmos Amplifier CD Input Power into 4 ohm vs Frequency Meas...png

Overall for the class, this is very good power and general performance.

Eco Mode Amplifier Performance
I measured the effect of leaving Eco mode in auto versus On (above tests were with ECO=OFF):

AVR-X6700H AVR Surround HDMI Dolby Atmos Amplifier CD Input Power into 4 ohm Eco Mode Auto On ...png


As with my previous tests, auto mode has no impact on performance. The switching seems well, seamless.

Turning on the ECO mode not only limits power to just 38 watts but also raises the noise level some. So auto mode would be the preferred mode of operation if you need the power saving and heat reduction.

HDMI Input Amplifier Performance
Since majority use HDMI as the chose input, I ran a separate test on its performance:

AVR-X6700H AVR Surround HDMI Dolby Atmos Amplifier CD Input Measurement.png


There is essentially no impact because the DAC performance was a few dBs better.

Multichannel Amplifier Power Response
I ran a test where I increased the number of channels driven from 1 to 5 channels using 8 ohm impedance (did not want to press my luck with 4 ohm load):

AVR-X6700H AVR Surround HDMI Dolby Atmos Amplifier Power Per Channel 8 ohm.png


Above is using 1% THD+N. You still have over 100 watts of output with all five channels running.

The testing as is standard in the industry is at 1 kHz. I thought I run a sweep from 20 Hz to 20 kHz and step through the channels just the same. Alas, after adding the third channel, the AVR went into protection mode immediately and shut down. This tells me the actual available power in bass where most of the action is, is lower than the above bar chart indicates. When I get the second sample from Denon, I will run this test again and verify this issue.

EDIT: Forgot to include these in the original review.
Thermal Performance
As I have been commenting, these Denon/Marantz AVRs run pretty warm. So I thought I take a snapshot after my testing using my IR camera:
AVR-X6700H AVR Audio Heat Rise Measurement.png


As we see the hottest area is the row of heatsinks. Zooming in we get the peak temperature:

AVR-X6700H AVR Audio Heat Rise Zoomed Measurement.png


As we see the peak temperature is 72 degree C (161 F) and this is the heatsink. The junction temperature for the power output transistors will be much higher. And this is with the AVR in "open air" and not in any kind of cabinet. So be careful about amount of airflow.

Conclusions
Stepping up in Denon AVR line gets you progressively more power and that is indicated in my measurements. Amplifier running out of power is a key aspect of sound quality suffering so this is good.

Alas, the performance of the pre-amp output is disappointing in the way it has regressed relative to other units in the line. Hopefully the later production units perform better. Until I can verify that, I can't recommend the Denon AVR-X6700H.

-----------
As always, questions, comments, recommendations, etc. are welcome.

The number of messages I get in my forum inbox has exploded as of late. I need to hire someone to impersonate me and answer them. I can't find anyone as good looking as myself but since people can't see my image in these messages, maybe I have some hope of finding someone to do that. They won't work for free though so please donate what you can using : https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 
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Promit

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#2
It's unfortunate that such a high end receiver doesn't live up to its lower spec brethren, and I'm curious to see what a capacitor substitution does to these numbers. But I absolutely love how engaged and forthcoming Denon has been with ASR, and I'm hoping it translates to an effort to really improve some of these metrics in the 800 series. Denon if you're reading, I am a current Denon owner and this type of engagement makes me excited to make more Denon purchases in the future including this year. It really is meaningful.

Oh and Amir, thank you for adding the multiple channels driven tests. Very helpful graph to include in these reviews. I don't know what the right sort of broadband signal is for this test but even the 1 kHz is good to see.
 
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BsdKurt

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#3
Nice review @amirm. Another win for consumers! Those with faulty capacitors will have the ability to get this fixed thanks to you.
They will be sending me a newer unit without this issue for testing in the future. I will be updating this review when I get that sample and test it.
I'm very impressed with Denon's willingness to work with you and that they will be sending you a unit with the fixed capacitor.
 

Vasr

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#4
So the fall guy is a "cap" now? ;)

This distortion from the "faulty cap" is different from the downmix issue in X4700H, right? If so, did you test if this unit suffers from the same downmixing issue?
 
OP
amirm

amirm

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Thread Starter #5
This distortion from the "faulty cap" is different from the downmix issue in X4700H, right? If so, did you test if this unit suffers from the same downmixing issue?
Correct. I confirmed that Coax input results in same performance issue. I did not check the downmix issue but I am confident it is present here as well.
 

Baff

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#6
"93dB peak performance vs 102dB on 3700"
Is that supposed to say 3600? 4700?

 

Vasr

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#7
So that is two strikes against this model.

What you have done with your hard work is force a voluntary recall of this unit for the "cap".

If they are doing this ethically, they should send a letter to all previous registered buyers and to all dealers (who are not necessarily here) announcing this exchange program and put up a serial number check on the web site. Let us see how they handle this.

I don't like the "people won't notice it and it still passes our testing" crap. Not in this price range and not with their marketing. This is significant distortion.

It would also be better if they sent you a voucher for a new purchase from a vendor than supply a unit on their own. Just so there is no appearance of a "golden sample". There would be no practical way to verify it after testing that unless you get another street unit in.
 

MZKM

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#8
Multichannel Amplifier Power Response
I ran a test where I increased the number of channels driven from 1 to 5 channels using 8 ohm impedance (did not want to press my luck with 4 ohm load):

Thanks for running this. The Marantz siblings usually state 70% for 5ch, so especially for 7-11 channels I assume they would be even better over Denon (that said, the measured performance of the Marantz AVR you did was less than stellar).
 
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amirm

amirm

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Thread Starter #9
So that is two strikes against this model.

What you have done with your hard work is force a voluntary recall of this unit for the "cap".

If they are doing this ethically, they should send a letter to all previous registered buyers and to all dealers (who are not necessarily here) announcing this exchange program and put up a serial number check on the web site. Let us see how they handle this.

I don't like the "people won't notice it and it still passes our testing" crap. Not in this price range and not with their marketing. This is significant distortion.

It would also be better if they sent you a voucher for a new purchase from a vendor than supply a unit on their own. Just so there is no appearance of a "golden sample". There would be no practical way to verify it after testing that unless you get another street unit in.
They haven't had much time to react to these findings. I pushed them for a statement overnight in advance of this review and I think in that context, they did well.
 

Baff

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#10
One other minor typo toward the end "the AVR went into product immediately and shut down". I assume that should be "protect".
 
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amirm

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Thread Starter #11
Thanks for running this. The Marantz siblings usually state 70% for 5ch, so especially for 7-11 channels I assume they would be even better over Denon (that said, the measured performance of the Marantz AVR you did was less than stellar).
Hmmm. This is what they say:

1595620926174.png


70% of stereo (161 watts) would be 113 watts and that is exactly what the Denon AVR-X6700H produces in five channels! So they are meeting that spec.
 
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amirm

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Thread Starter #12
One other minor typo toward the end "the AVR went into product immediately and shut down". I assume that should be "protect".
Thanks. Corrected.
 

Gedeon

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#13
It's a bit of surprise that sr6014 isn't so bad when looking up to 1.4 Volts output and multitone test.

Obviously this one has got more power and a more linear response. But not sure if aged ears would realize unless feeding hungry speakers.
 
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#14
I am really glad I bought X3600 to use as processor :) Thanks amirm for the reviews. I am sure Denon engineers will run all measurements on future models and fix all problems prior to production thanks to your work ! And will look forward for AVRs/Processors with SINAD over 105dB in the future.
 
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#15
Nice to see Denon offering replacement process. Will be interested to see how the 3700 performs. I wonder how close to the 3600 it will be.
 
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amirm

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Thread Starter #16
"93dB peak performance vs 102dB on 3700"
Is that supposed to say 3600? 4700?

Thanks. Should have said 3600 as I have not yet measured the 3700. Corrected.
 

Vasr

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#17
They haven't had much time to react to these findings. I pushed them for a statement overnight in advance of this review and I think in that context, they did well.
Ok. As long as you don't become the Maggie Habermann of ASR for access. ;)

Just a joke, not trying to insult or insinuate. :)
 
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#18
Got the impression that those AVRs are a waste of time and we focus too much on them. Instead, they should be discouraged and neglected. I see stereo amps/ monoblocks deliver better performance, yet not many got proper attention.

It was an interesting question raised recently, namely how do compare: a brilliant DAC into a terrible amplifier vs. a terrible DAC into a brilliant amplifier. How to match the amplifier with speakers...

Anyway, I envision more this forum focus on full-stack recommendation: dac + amp + speakers, dac + headphone amp as I believe nothing will deliver better sound performance then curated list of components.
 
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amirm

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Thread Starter #20
Got the impression that those AVRs are a waste of time and we focus too much on them.
We are kind of stuck in that video processing and advanced audio surround codec decoding does not exist in 2-channel world. So if you want to watch movies, video concerts and such, these are the only solutions. As such, we need to quantify their performance and find the best we can among the category.
 
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