Beolab 7-2 distortion only on some soundtracks

[DT79]

Hi folks,

Hoping for advice on a strange issue.  I have a Beolab 7-2 speaker used as a centre channel in a 5.1 set-up, alongside BL8000 fronts, BL6000 rears and a BL19.

These are all being driven from the preouts of an Anthem MRX520. The 7-2 is connected via an RCA-to-powerlink cable which also incorporates a 5v trigger which is connected to a USB socket on the TV

A couple of months back I first noticed a distortion on loud voices when playing one particular film.  I thought it was a one off and as it was a rip, I thought maybe I’d done something wrong. Since then I’ve noticed it on a few other things from various sources: other rips and also some streaming services. However it definitely doesn’t happen on everything.

I did wonder whether it was an input sensitivity mismatch and tried lowering the output level of the anthem, but then of course I was turning up the volume commensurately more, so I guess it’s all the same in the end and indeed I don’t think that made a difference.

It’s a weird one because it never happened before a couple of months ago, and it doesn’t occur on everything.

Any ideas? Does anyone have the input sensitivity spec for the 7-2, then I can check if that might be the issue?

I could pick up another 7-2 for a relatively modest cost, but want to be sure that this one is actually faulty before doing that, and at the moment, that seems unclear.

Thanks for your help.

Dan

[DT79]

FYI, in case anyone finds this with a similar issue…

I’ve confirmed that it really is just certain soundtracks. I dug out the disc of the rip mentioned above where I first noticed the issue and it played fine, even when turned up very loud: no distortion. The rip was not 1:1 I had converted the soundtrack to save space.

I think the issue might also be with the Anthem Room Correction EQ curve as I tried toggling it off when experiencing the distortion and it reduced significantly.

I think it might be a combination of the characteristics of the soundtrack and the ARC EQ.

 

 

[Die_Bogener]

I have something like that with HDMI and DVD Player Software.

The sound is playing with 16-bit resolution. A loud section of the music/movie can use these 16-bit 100%.

If you use a software, that is increasing this 16-bit range to make it louder again, then there is a software bug… it’s an overrun of the system, you would need 17 or 18 bit or even more… and these bits are not available.

It’s a cheap and mean software bug of calculating the value.  It would be better, to limit the sound to the maximum instead making a overrun…

[DT79]

Thanks for your reply. If I understand correctly, and to put this in terms I understand, what you’re basically saying is that the loud parts of the signal are exceeding 0dBfs which is causing distortion when decoded by the DAC in the AV processor?

Thats a reasonable theory and would explain why it happens from some sources/soundtrack and not others and why the room correction EQ also appears to have an effect.

now I come to think about it, I have only heard the problem from different apps on the TV (Plex playing back files or streaming services), not external sources like sky box or blu-ray. Is there some kind of audio setting on the TV that I should be looking for?

I will continue to experiment with the amp’s eq as well.

Die_Bogener wrote:

I have something like that with HDMI and DVD Player Software. The sound is playing with 16-bit resolution. A loud section of the music/movie can use these 16-bit 100%. If you use a software, that is increasing this 16-bit range to make it louder again, then there is a software bug… it’s an overrun of the system, you would need 17 or 18 bit or even more… and these bits are not available. It’s a cheap and mean software bug of calculating the value. It would be better, to limit the sound to the maximum instead making a overrun…

[Author]

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