Question TV sound volume very different per channel thru Onkyo TX-SR393


Novice Member
I got Onkyo TX-SR393 as it supports Dolby Atmos yet I only have 5.1 regular speaker.
I don't have celing speaker nor I am planning but looking into getting upward firing speaker.

Anyway, my question is:

When I set TV audio output as PCM, all OTA channel sound level about same but
when I set audio out to Dolby (No bitstream out on samsung TV), some channels sounds good but some channel sounds are so low that I can hardly hear.
Is this normal behavior that I need to increase volume? The reason why I set Dolby is; TV setting says set Dolby if your AV supports Dolby thru ARC but outcome is not what I am expecting.

Can anyone explain this?

Thanks in advance.


Distinguished Member
The Onkyo TX-SR393 can only facilitate Atmos or DTS:X via use of vitual height processing. It is only a 5.1 channel AVR so has the ability to drive physical height speaker. I'd therefore not suggest you add ceiling or height speakers to your setup.

Anyway, the answer is:

THe SD channels encoded with 2 channel PCM have a different dynamic range comparedto the HD channels commonly encoded with Dolby Digital. THe Dolby Digital encoded channels will also be subject to dialogue normalisation which only Dolby encoded content can benefit from. This is basically why the DD encoded channels sound louder than the SD PCM encoded channels.

If you set your TV's audio output to PCM then the TV will mixdown any 5.1 DD encoded audio and output it as 2 channel PCM. You should try avoid this and output the audio as it was originally encoded. You'll only get discrete 5.1 in association with TV shows etc that include it id you select and use the DD option.

It is normal for you to perceive differences in volume between the PCM and the DD encoded channels.


Novice Member
Thank you so much for quick reply.
I was wondering how I was going to add height speaker if I was going to add. Your answer solved my question.
I thought I had some defective system when it sounded terrible and low on certain broadcast.
Thank you.

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