Anthem AVM70 Review (AV Processor)

[nathan]

What content has 7.1 down mixed to 5.1?

Almost all the content I play is 7.1 content, but I have a 5.1 speaker layout. The AVR doesn’t throw away the rear channel content. It downmixes the rear channel content into the surround speakers, combining it with the side surround channels.

 

[peng]

Almost all the content I play is 7.1 content, but I have a 5.1 speaker layout. The AVR doesn’t throw away the rear channel content. It downmixes the rear channel content into the surround speakers, combining it with the side surround channels.

As I said, it should work if it is actually downmixing 5.1, 7.1 to 2.1, but not if you use stereo mode, when the Dolby rules don't apply.

 

[peng]

The AVM will (or should) know that by itself when a 4.1 or 2.1 speaker profile is selected, and the input signal is 5.1 or 7.1

Great, then my question is, how did you do that REW phantom channel sweep? It can obviously do it for the center channel, but I don't recall seeing the phantom option. If I select L+R then obviously the level will be higher.

 

[nathan]

As I said, it should work if it is actually downmixing 5.1, 7.1 to 2.1, but not if you use stereo mode, when the Dolby rules don't apply.

Right. But the OP said he is using a 4.1 setup, not a two channel stereo option.

 

[nathan]

Great, then my question is, how did you do that REW phantom channel sweep? It can obviously do it for the center channel, but I don't recall seeing the phantom option. If I select L+R then obviously the level will be higher.

The OP said he is using 4.1 as hit speaker setup. This uses a phantom center by definition.

 

[peng]

The OP said he is using 4.1 as hit speaker setup. This uses a phantom center by definition.

It has nothing to do with that. My question was about his REW sweep, how did he select the center channel?

Anyway, I can try it later when I have a minute, maybe REW has that phantom channel selectable in the latest version, again, will find out, hard to imagine how it could be done.

 

[StigErik]

Great, then my question is, how did you do that REW phantom channel sweep? It can obviously do it for the center channel, but I don't recall seeing the phantom option.

The whole point is that the phantom center is created by the AVR.....

 

[StigErik]

It has nothing to do with that. My question was about his REW sweep, how did he select the center channel?

By selecting the center channel.

 

[nathan]

It has nothing to do with that. My question was about his REW sweep, how did he select the center channel?

Anyway, I can try it later when I have a minute, maybe REW has that phantom channel selectable in the latest version, again, will find out, hard to imagine how it could be done.

Don't need to select phantom center. You send a CENTER CHANNEL signal to the AVR. The AVR takes that and downmixes it into a phantom center.

 

[GXAlan]

It has nothing to do with that. My question was about his REW sweep, how did he select the center channel?

Anyway, I can try it later when I have a minute, maybe REW has that phantom channel selectable in the latest version, again, will find out, hard to imagine how it could be done.

Using ASIO4ALL you can send a signal to an individual 7.1 HDMI out. The audio is seen by the receiver/processor as 7.1 PCM

 

[peng]

Don't need to select phantom center. You send a CENTER CHANNEL signal to the AVR. The AVR takes that and downmixes it into a phantom center.

Thank you for saving me time to grab the mic and try it myself. In that case it is as I thought, REW simply would do the sweep from the output of the AVR, but in that case the Dolby rule that GXAlan wouldn't apply would it?

 

[peng]

Using ASIO4ALL you can send a signal to an individual 7.1 HDMI out. The audio is seen by the receiver/processor as 7.1 PCM

If you are referring to REW, you don't need the ASIOFORALL anymore, Java will work in the latest versions. I already agreed the AVM "should" know playing 5.1 and 7.1 to a 4.1 speaker profile will need to create the phantom channel, but I am not sure if you run REW, it would actually get the downmixed signal that follows the Dolby rule. I thought them response saved me time to find out by trying, but because of my doubt on whether REW would actually get the downmixed 5.1, or 7.1 signal, I will still have to hook things up to find out, as I don't want to keep bothering them with my potentially silly questions.

 

[nathan]

Thank you for saving me time to grab the mic and try it myself. In that case it is as I thought, REW simply would do the sweep from the output of the AVR, but in that case the Dolby rule that GXAlan wouldn't apply would it?

It's an interesting question. I would surmise that it should/would. Maybe, for a PCM signal like from REW, this is the Wild West and AVR makers can choose how to handle it. It would mean that every test tone sweep will sound wrong if the source is multi channel PCM, but sound right if the source if multi channel DD. (By "right" and "wrong" I mean the center pink noise from an external source would sound sound louder than the other channels with PCM but sound like the same level with DD material.)

 

[nathan]

If you are referring to REW, you don't need the ASIOFORALL anymore, the windows driver will work in the latest versions. I already agreed the AVM "should" know playing 5.1 and 7.1 to a 4.1 speaker profile will need to create the phantom channel, but I am not sure if you run REW, it would actually get the downmixed signal that follows the Dolby rule. I thought them response saved me time to find out by trying, but because of my doubt on whether REW would actually get the downmixed 5.1, or 7.1 signal, I will still have to hook things up to find out, as I don't want to keep bothering them with my potentially silly questions.

Just to be clear, we may be talking about two different things? Apologies for being really overly specific in how I write this, but it is hard for me to describe it well.

REW would not get and does not generate a down mixed signal.

Rather, REW generates a normal center channel signal, and REW sends that center channel signal to the AVR.

This is similar to how any source device sends content to an AVR. Just send the bitstream, or multi channel PCM, however many channels are in the source, direct to the AVR....and let the AVR figure out how to render it.

The question is what does the ANTHEM do with the center channel content? (And does it differ in some situations?)

We know if you have a 4.1 speaker config, the ANTHEM puts an equal amount of center content in the left and right speaker, creating a so called Phantom Center.

We know that if the incoming signal was a DD signal, the Dolby algorithm says to attenuate that center chanel signal down so that the summed level of the center content matches the level of the other speakers.

What we don't know is whether an incoming PCM signal is treated the same as a DD signal, right? The OP did some measurements which suggest a PCM signal is handled differently (ie, the content is not level aligned with the other speakers). And we know that someone at Anthem appears to be saying this is the intended behavior. Which (opinion?) I would surmise is not what one wants from a decoding algorithm.

 

[peng]

Just to be clear, we may be talking about two different things? Apologies for being really overly specific in how I write this, but it is hard for me to describe it well.

REW would not get and does not generate a down mixed signal.

Rather, REW generates a normal center channel signal, and REW sends that center channel signal to the AVR.

This is similar to how any source device sends content to an AVR. Just send the bitstream, or multi channel PCM, however many channels are in the source, direct to the AVR....and let the AVR figure out how to render it.

The question is what does the ANTHEM do with the center channel content? (And does it differ in some situations?)

We know if you have a 4.1 speaker config, the ANTHEM puts an equal amount of center content in the left and right speaker, creating a so called Phantom Center.

We know that if the incoming signal was a DD signal, the Dolby algorithm says to attenuate that center chanel signal down so that the summed level of the center content matches the level of the other speakers.

What we don't know is whether an incoming PCM signal is treated the same as a DD signal, right? The OP did some measurements which suggest a PCM signal is handled differently (ie, the content is not level aligned with the other speakers). And we know that someone at Anthem appears to be saying this is the intended behavior. Which (opinion?) I would surmise is not what one wants from a decoding algorithm.

Thanks for being overly specific as that suits me fine. I think we are more or less talking about the same things. In any case, I have my mic hooked up now and will do some experiments.

 

[nathan]

I will be curious to hear what you learn.

FYI, if you want to use a DD test file with just the center channel playing -- to compare that result with the PCM test tone from REW's own generator -- a user on another forum created a set and shared them freely. There is a way to actually use it with REW instead of the internal test tone generator. (I haven't used them that way. I just use them from an Apple TV to confirm speaker levels.). I think I can post a link to another forum, here, right?

If not, I will take it down:

Dolby Atmos and REW

Yes, but the sweeps aren't compatible with REW. Correct, it needs AudioTools. AudioTools is the standard measurement software used by the Home Acoustics Alliance (HAA) training/certification for home theater calibration. The conversation morphed to not being able to even test channels beyond...

www.avnirvana.com

and other posts. They did a few different versions of the test files. They also linked to some official dolby files (but instead of being one speaker at a time, it is a moving pink noise, IIRC) that are free to download. So in theory when playing ANY of the following three files from a thumb drive or what not directly into the AVR, and having the AVR set up to play 4.1 content, each of the 5 or 7 of 9 test tones you hear out of the four main speakers should all register the same level on an SPL meter at the main listening position.

https://download.dolby.com/us/en/test-tones/dolby-test-tones_5_1_2.mp4

https://download.dolby.com/us/en/test-tones/dolby-test-tones_7_1_4.mp4

https://download.dolby.com/us/en/test-tones/dolby-test-tones_9_1_6.mp4


And I think they also did pink noise files for each channel, in addition to those sweeps (which are great for REW). But I haven't tried those yet.

Direct link here to the ATMOS sweeps that the user there created:

256k_20_to_20000_48k_V2.zip

Atmos 9.1.6 sweeps for REW (256k)

drive.google.com

 

[StigErik]

I finally managed to do some measurements of the pre outs from the AVM70. And guess what - it's all by the book. Phantom center signal is attenuated 3 dB in L and R, just like it should be.

The question now is - what happens when my two front speakers (and subwoofer) add 6 dB.
I've always thought that two speakers driven from independent sources would sum by +3 dB, and not 6 dB.

 

[StigErik]

That does however not change the fact that the center channel content will be 3 dB too loud in a phantom center speaker setup.

 

[peng]

I will be curious to hear what you learn.

FYI, if you want to use a DD test file with just the center channel playing -- to compare that result with the PCM test tone from REW's own generator -- a user on another forum created a set and shared them freely. There is a way to actually use it with REW instead of the internal test tone generator. (I haven't used them that way. I just use them from an Apple TV to confirm speaker levels.). I think I can post a link to another forum, here, right?

I read something about that and wanted to try but have yet to find time.

If not, I will take it down:

Dolby Atmos and REW

Yes, but the sweeps aren't compatible with REW. Correct, it needs AudioTools. AudioTools is the standard measurement software used by the Home Acoustics Alliance (HAA) training/certification for home theater calibration. The conversation morphed to not being able to even test channels beyond...

www.avnirvana.com

and other posts. They did a few different versions of the test files. They also linked to some official dolby files (but instead of being one speaker at a time, it is a moving pink noise, IIRC) that are free to download. So in theory when playing ANY of the following three files from a thumb drive or what not directly into the AVR, and having the AVR set up to play 4.1 content, each of the 5 or 7 of 9 test tones you hear out of the four main speakers should all register the same level on an SPL meter at the main listening position.

https://download.dolby.com/us/en/test-tones/dolby-test-tones_5_1_2.mp4

https://download.dolby.com/us/en/test-tones/dolby-test-tones_7_1_4.mp4

https://download.dolby.com/us/en/test-tones/dolby-test-tones_9_1_6.mp4

Thanks.

And I think they also did pink noise files for each channel, in addition to those sweeps (which are great for REW). But I haven't tried those yet.

Direct link here to the ATMOS sweeps that the user there created:

256k_20_to_20000_48k_V2.zip

Atmos 9.1.6 sweeps for REW (256k)

drive.google.com

I played with REW for about 30 minutes then ran out of time for today. From the dozen or more sweeps I have done, there were no clear evidence the center channel was boosted by 3 dB, if anything, I think it was not an issue. It is naturally difficult to see the differences with those sweeps even if tons of smoothing, such as 1/3 is used. I don't think the way the OP did with REW is the right way to prove his case. GXAlan may be right about using test files might be a better way.

 

[StigErik]

I did the test with various test files as well. Same result as with REW.