Anthem AVM70 Review (AV Processor)

[Beershaun]

Agreed. I think you are expecting the AVR to reduce the level of the center signal by 3db relative to the left and right signals because it's being sent to two speakers. It seems like the 3db increase is because you have two speakers replicating the center signal instead of 1. Level matching manually wont solve that problem. You should try running ARC with it set up as 4.1 in the speaker configuration and see if it is smart enough to drop the center signal by 3db relative to the left and right specific signals.

 

[nathan]

Agreed. I think you are expecting the AVR to reduce the level of the center signal by 3db relative to the left and right signals because it's being sent to two speakers. It seems like the 3db increase is because you have two speakers replicating the center signal instead of 1. Level matching manually wont solve that problem. You should try running ARC with it set up as 4.1 in the speaker configuration and see if it is smart enough to drop the center signal by 3db relative to the left and right specific signals.

I don’t get it. It shouldn’t be necessary to run arc to have the center channel contents played back at the correct level relative to the other channels.

I don’t expect surround back channels to be 3db extra loud when downmixed and played back by the surround left and surround right channels when playing 7.1 content in a 5.1 speaker system.

So why should the center channel content, when downmixed and played back by the front left and front right speakers in a 2.1 or 4.1 or 6.1 system be 3db extra loud?

 

[nathan]

I think they did, if you play contents that has the center channel, but you are relying on the phantom center effect, that's how the AVM works, according to their explanation. We may not like their response, but I think they are just giving us a honest anwer.

It’s an honest answer but I’ll bet it’s not how Dolby specifies downmixing for Dolby content.

 

[nathan]

All that being said using REW in a normal room to test this is probably not too precise. Room gain and different boundary conditions between the various speakers could easily create a 3db difference. The real test is probably taking the preamp output direct into REW or similar software.

 

[StigErik]

Agree with that. I will measure the pre outs and present the results later today. That is … in about 15 hours or so. Still early morning here….

 

[StigErik]

I came to think of the fact that the subwoofers are the same for all channels. There lies the evidence for acoustic in-room measurements. If the center channel upmix to front L and R is correct, the center channel content played by the subwoofers should measure the same as when using a center speaker, provided that the bass management crossovers are equal. Agree?

 

[nathan]

On the face of it that would seem to make sense.

 

[StigErik]

 

[nathan]

View attachment 355537

Is that the pre-outs? If so that’s disappointing. I can’t imagine running ARC will solve that but I suppose it is worth trying?

 

[StigErik]

In-room measurement. Without ARC so far. Will do that later.

 

[Beershaun]

I don’t get it. It shouldn’t be necessary to run arc to have the center channel contents played back at the correct level relative to the other channels.

I don’t expect surround back channels to be 3db extra loud when downmixed and played back by the surround left and surround right channels when playing 7.1 content in a 5.1 speaker system.

So why should the center channel content, when downmixed and played back by the front left and front right speakers in a 2.1 or 4.1 or 6.1 system be 3db extra loud?

What content has 7.1 down mixed to 5.1? Any 7.1 content I have ever seen has a 5.1 mix which is what is sent when your system doesn't have 7.1. the reason it's not 3db louder is because you are receiving native 5.1 and the AVR is not having to do the work itself.

My expectation for why the center channel content is 3db louder is: to create the phantom center is you have to play the same content out of both speakers at the same exact volume level for it to sound like it's exactly between them. When you play the same content at the same volume from two speakers the volume at the listening position is 3db louder than if it was from one. That means for the center content to actually be perceived at the listening position at the same volume as the left or right speaker normal content, the AVR must pre process and adjust the levels discreetly when it splits the signal into left and right. I believe the AVRs room correction software needs to be used for it to be aware that the center channel signal needs to be split and adjusted separately before being mixed into the left and right channel.

 

[StigErik]

My expectation for why the center channel content is 3db louder is: to create the phantom center is you have to play the same content out of both speakers at the same exact volume level for it to sound like it's exactly between them. When you play the same content at the same volume from two speakers the volume at the listening position is 3db louder than if it was from one. That means for the center content to actually be perceived at the listening position at the same volume as the left or right speaker normal content, the AVR must pre process and adjust the levels discreetly when it splits the signal into left and right.

The question is - why can't the AVM70 do this right without having to turn on room correction? That is - reduce the center content by 3dB in a phantom center speaker setup.

It remains to be seen if the ARC room correction will solve this problem. Like I said - I will test this later today.

 

[peng]

The question is - why can't the AVM70 do this right without having to turn on room correction? That is - reduce the center content by 3dB in a phantom center speaker setup.

It remains to be seen if the ARC room correction will solve this problem. Like I said - I will test this later today.

On that, I agree, but how do you let the AVM70 know you are downmixing 5.1, 7.1 etc., to 2.1? Did you press the mode button on the remote and select "stereo"?

 

[StigErik]

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

 

[GXAlan]

I think they did, if you play contents that has the center channel, but you are relying on the phantom center effect, that's how the AVM works, according to their explanation. We may not like their response, but I think they are just giving us a honest anwer.

But it shouldn’t do that according to the Dolby spec I offered a few posts up? The only exception is if it’s a MCH PCM issue. @StigErik just needs to find an old Dolby test DVD/Blu-Ray (Pixar/Disney Blu-Rays used to include audio test tones) and I think Netflix has audio test tones with their test patterns. If Dolby processing is correct it’s an issue with PCM. If Dolby processing is incorrect, it’s a bug.

 

[StigErik]

I don't have any Dolby encoded discs with test tones, but let some old classics with mono sound. In theory at least, that mono should be in the center channel... I hope

 

[GXAlan]

I don't have any Dolby encoded discs with test tones, but let some old classics with mono sound. In theory at least, that mono should be in the center channel... I hope

Watch Test Patterns | Netflix

This is a collection of video test patterns organized by source resolution and native frame rate. The resolution indicated in the pattern's title identifies the title's source resolution, and therefore, the stream set's maximum encoded resolution. The frame rate indicated in the pattern's title...

www.netflix.com

Very hard to find in search for whatever reason

 

[peng]

But it shouldn’t do that according to the Dolby spec I offered a few posts up? The only exception is if it’s a MCH PCM issue. @StigErik just needs to find an old Dolby test DVD/Blu-Ray (Pixar/Disney Blu-Rays used to include audio test tones) and I think Netflix has audio test tones with their test patterns. If Dolby processing is correct it’s an issue with PCM. If Dolby processing is incorrect, it’s a bug.

I read that link right after you posted, thanks. It depends on whether the unit knows to "downmix" from X.1 to 2.1, otherwise what's in the link may not apply. I asked OP the question, please read the OP's response post 774.

 

[StigErik]

Watch Test Patterns | Netflix

This is a collection of video test patterns organized by source resolution and native frame rate. The resolution indicated in the pattern's title identifies the title's source resolution, and therefore, the stream set's maximum encoded resolution. The frame rate indicated in the pattern's title...

www.netflix.com

Very hard to find in search for whatever reason

Thanks, but I don't have Netflix.

Will check out a mono sound Blu-ray disc later today.

 

[GXAlan]

Will check out a mono sound Blu-ray disc later today.

https://www.avsforum.com/threads/blu-ray-mono-audio-converted-to-stereo.3247220/

Some mono BD tracks are actually encoded as 2 channel.

The only way to prove an inaccurate down mix is to have a proper Dolby encoded test file.

This is what a Google search reveals:

One moment, please...