nathan
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Anthem AVM70 Review (AV Processor)
- Thread starter amirm
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Two independent speakers playing uncorrelated broadband signal would result in an increase of 3 dB. To get a 6 dB increase, both sources would need to be playing a correlated signal and be in the same acoustic environment -- like two adjacent woofers on the same multi-driver speaker or two smaller subs stacked/placed next to each other.
This does not apply to stereo playback of content like music, as the two channels have a mix of correlated and uncorrelated content, as well as interference effects with each other.
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Yes, and I think the AVM would do just that, right from the beginning I was wondering if StigErik's way of determining whether his unit had an issue, had to do with the way he measure. After taking a dozen or so measurements yesterday, I am quite sure the way he measured it with REW is not conclusive. I don't know what is the right way, let alone the best way. After all, phantom vs a real center speaker is not going to give you the same results even right at the MMP unless there is in fact some sort of specially designed test files.
Well, I initially started to investigate this after I noticed that the center channel content sounded slightly louder with a 4.1 speaker layout than with a 5.1.
I verified of course that all five speakers had the same level and frequency response in the listening position. All five speakers are also identical.
Then I started to measure the SPL at the listening position, comparing the two speaker layouts with the same input signal generated with REW for the center channel. It gave me 3 dB more SPL with the 4.1 layout compared to the 5.1 layout.
My measurements are found at post #768 in this thread. Please enlighten us all regarding what's wrong with it.
I verified of course that all five speakers had the same level and frequency response in the listening position. All five speakers are also identical.
Then I started to measure the SPL at the listening position, comparing the two speaker layouts with the same input signal generated with REW for the center channel. It gave me 3 dB more SPL with the 4.1 layout compared to the 5.1 layout.
My measurements are found at post #768 in this thread. Please enlighten us all regarding what's wrong with it.
I did see those graphs, no there was nothing wrong, just that those measurements don't seem to be enough for one to draw the conclusion that "It gave 3 dB more SPL....".
Sorry I had hard time finding time to do the same kind of REW experiments you did and have hard time finding the right words to express myself. Just one point for now, try using 1/12 smoothing, you will see a much different picture but obviously you know that already. If I get to do my experiment, I will post some graphs and with the graphs may be I could find the appropriate words to convince you why doing it that way is not good enough to draw the conclusion that you seem to have drawn.
By the way, for curiosity sake, I also asked Anthem yesterday, got a response, and I am not sure if the answer I got is the same as the one you got. I never felt Anthem gave you a non sensical answer either. Will post something later, got to leave the house now.
My measurements showed that in my room, with my speakers - using a phantom center speaker layout ends up with the center channel input signal being 3 dB higher in level.
I post my measurements again below, where the magenta line with the phantom center obviously is 3 dB above the others. All four measurements were done in the main listening position, and of course with the same source signal and level in REW being send to HDMI channel 3, which is the Center channel.
The AVM70 follows the standards for phantom center. The center signal is adjusted by -3 dB, and then sent to both L and R fronts.
In my case at least, the two front L and R speakers, as well as the subwoofer, will sum the signal adding back 6 dB.
-3 dB + 6 dB = +3 dB
I post my measurements again below, where the magenta line with the phantom center obviously is 3 dB above the others. All four measurements were done in the main listening position, and of course with the same source signal and level in REW being send to HDMI channel 3, which is the Center channel.
The AVM70 follows the standards for phantom center. The center signal is adjusted by -3 dB, and then sent to both L and R fronts.
In my case at least, the two front L and R speakers, as well as the subwoofer, will sum the signal adding back 6 dB.
-3 dB + 6 dB = +3 dB
In that case, we are in agreement, that is, AVM70 follows the "standard" (not sure if the same standard is used by all, but it appears to be consistent with the Dolby one @GXAlan linked before. I thought you have issue with that but based on this post, apparently not.
As as as the L+R 6 dB higher, we have to keep in mind what @rynberg posted, #803, so it is not always black and white.
The subwoofers obviously have influence and how much they would affect the overall SPL would depend on your specific sub's in-room response, and having ARCG in use should help making the results more predictable. Between the subwoofers, ARCG's contribution, and the smoothing you chose, and the frequency range you use, are some of the reasons I don't think doing it this way is the best way to draw a conclusion of whether AVM70 is doing something similar to others such as D+M, Onkyo, or doing something weird.
I have plotted a ton of REW FR graphs, and they don't indicate an issue with the level discrepancy in terms of the phantom center vs real center, especially if ARCG is enabled and the mic at mmp. I can post some of them once I have them organized.
nathan
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Thanks in advance for sharing those when time permits.
Will post some tomorrow.
A thing that you can do which may be more realistic, is to run the Dolby Atmos test that was linked to earlier in this thread.
I used this file:
dolby-atmos-test-tones-5.1.4-(www.demolandia.net).mkv
It's available here:
Set your measurement mic in the main listening position. Start REW, go to SPL Meter, and start the logger.
Make sure the center channel is enabled in the AVM70 (or other AVR)
The play the test file chapter 4 (at 2:11), where pink noise is playing in the center channel.
Let it play for at least 30 seconds. Then pause, and go to your AVM70 and turn off the center channel:
Play the test tone from 2:11 again and notice if there is any change in SPL.
I used this file:
dolby-atmos-test-tones-5.1.4-(www.demolandia.net).mkv
It's available here:
Set your measurement mic in the main listening position. Start REW, go to SPL Meter, and start the logger.
Make sure the center channel is enabled in the AVM70 (or other AVR)
The play the test file chapter 4 (at 2:11), where pink noise is playing in the center channel.
Let it play for at least 30 seconds. Then pause, and go to your AVM70 and turn off the center channel:
Play the test tone from 2:11 again and notice if there is any change in SPL.
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That seems like a better to do than the way you were doing with REW (a few points I mentioned yesterday). Now I'll have to find time to do it that way.
For now, I have plotted more than 50 graphs yesterday, got myself confused a little so I redid one set this morning. As expected, the results are not 100% conclusive in terms of the difference in level between the phantom versus physical center channel, because of the reasons I mentioned yesterday. I would probably try using the file you linked but I doubt it would make much difference.
From what I can see from the 60 or more files, I would say, again not 100% conclusive, but the phantom center, overall, is not going to be 3 dB louder, it is doubtful that it is an audible issue at all. I have no idea why yours look that way, may be somehow somewhere you had the center channel trim level adjusted in such a way (not sure how that can be possible though) that it wouldn't get reflected in the phantom case?? Don't really know...
Interesting. Can you please describe in detail how you did the measurements? REW settings, AVM settings, mic placement and so on? Especially describe what you changed when going from real center to phantom center.
I did it the way I always did, really nothing special except:
- Mic at MMP, at least close to it, but by memory only, obviously.
- Set subwoofers to none, to minimize their effects that would make analysis even more difficult.
- Use my profile 2 that is for 2.1, but again subwoofer set to none.
- Use psy smoothing instead of your 1/2 smoothing. According to REW, psy is more representative of what and how we hear anyway.
- For the physical center, I just change profile back to profile 1.
- Also try to use stick with profile 1 but just change the center to none when I want the phantom.
On thing I noticed was that if I stick with Profile 1 and just flip between setting center speaker to on and off did not yield the same result versus using Profile 2 that is for 2.1.
The difference is only in the low range, forgot what it was not but I thought it was for below about 100 Hz. When I notices that, I double checked to make sure both profile has the same subwoofer setting such as crossovers etc.. The last time I ran ARCG was about 3 months ago so I don't remember everything, but I am quite sure I did not run a different one for Profile2 so both should be using the same ARCG file. Regardless, the way I did it, the graphs do not reflect the contribution by the two subwoofers.
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Here's my Q&A with Anthem on the phantom thing:
Q: If I set a speaker profile to 4.1 , without a center speaker, will the phantom center channel be louder than normal, say by 3 or 6 dB when playing 5.1 contents?
A: If you turn off the center and play content with dialog that normally uses the center channel then it goes to left and right front in such as way that it maintains the relative level that it was mixed at. It is not boosted.
Q: If I set a speaker profile to 4.1 , without a center speaker, will the phantom center channel be louder than normal, say by 3 or 6 dB when playing 5.1 contents?
A: If you turn off the center and play content with dialog that normally uses the center channel then it goes to left and right front in such as way that it maintains the relative level that it was mixed at. It is not boosted.
That is not what I experience. All my measurements and subjective experience as well show a 3 dB increase. This is very odd indeed.
What was the difference?
Bass dip below 100 Hz, probably has to do with ARCG, that something is different when using 2.1. I have to investigate, time permitting, but it's not a priority for me because if and when I listen to 2.1 I typically use Dirac Live PC standalone version.
