Digital signal process (e.g. Dolby PLIIz) sends everything to centre, what's wrong?


Novice Member
Please could you help me understand what is going on here. Maybe I simply misunderstand the expected behaviour, but certainly what I am seeing is not at all what I want.

When playing a stereo source such as YouTube or ITV Hub, if I put my amp into a DSP mode such as Dolby PLIIz or DTS Neo 6, I expect that the amp would cleverly distribute the sounds to all 5.1 speakers appropriately. Namely, that it sends music to front, dialog to centre, deep bass to the sub, and some presence to the rears.
What actually happens is that almost everything comes out the centre. So this makes music sound naff, and there's no deep bass.

The amp (Marantz NR1504) does have the ability to tweak the processing parameters, but I've not fiddled with the factory settings.

Is my expectation of what these modes should do accurate?

How can I get the desired distribution (all/more speakers) of stereo sound when using these modes?

Many thanks


Distinguished Member
I'd suggest that the content you are applying the PLIIz processing 2 is mostly 2 channe dialogue centric? This would basically only use the centre speakers to portray said dialogue centrally.
THe upmixing modes you've mentioned use algorithms to analyse the audio they are being applied to. THey portray the audio via the speakers they determine to best portray what was actually captued in the audio recording. THese modes do not simply distribute the same audio to all the speakers present and they try to create a pseudo interpretation of the audio.

If simply wanting the audio to be portrayed by all the speakers then use a multichannel or 7ch stereo mode. THis would simply mirror you front stereo speakers via you surround and portray a mono interpretation of the stereo soundtrack via the centre speaker. Note that this wouldn't be correct if trying to create a psudo surround sound interpretation of what is being played though.

The cenre will inordinately also portray dialogue while watching discrete surround sound formats or if trying to create pseudo surround interpretations of something. Where else would you expect dialogue to be coming from if those talking are in front of you on a screen?

Even if and when viewing content with a doscretemultichannel surround soundtrack, the surround speakers would not always be in use. Even in such instances, the centre will be the most frequencly used speakers along with the lefdt and right speakers to either side of it.


Novice Member
Hello Dante
Thanks or your feedback.
I do understand what you say.

Indeed, I don't want the stereo signal evenly shared over all speakers (for which multi-channel stereo would suit), rather I am expecting that the processing distributes the sound cleverly (not equally) by applying its algorithm. Vocals to centre, music to front, bass to sub, in particular.

Perhaps I should have mentioned that I experienced this problem when listening to stereo dance music. The music all comes out the centre, and the fronts do nothing. Not even the drums.

This feels dreadfully incorrect to me; does it to you too?



Distinguished Member
I'd expect music to engage at least the front 2 speakers, primarilly the left and right.

I tend not to engage upmixing while listening to music and prefer to portray it as it was recorded as a stereo performance.

Does your AV receiver inclge eithe Dolby Pro Logic or DTS NEO Music options? If so then maybe try them?

Never the less, the leat least the left and right speakers should theiretically of been engaged while portraying music while using most if not all upmixing methods. Yes, it is strange how you aren't getting this?

THere may also be a centre spread option that forces the centre channel out to the left and right speakers. Maybe try that as well?

One last point worth mentioning is that if the source had been authored as a mono soundtrack then the processing would see that both channels are the same phase and this would result in the audio all being portrayed via the centre speaker? Maybe try using sources you can trust as opposed to youTube while carrying out tests and trials?
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Novice Member
Does your AV receiver inclge eithe Dolby Pro Logic or DTS NEO Music options? If so then maybe try them?
That's the secret.

Yesterday I was using a Movie processing mode. When selecting a music mode, it's much better.

I also changed the settings for speaker size, from large to small. This then allows bass to be sent via the LFE channel to the sub. of course in direct mode, whatever the size setting, all comes through only the mains.

Thanks again for the pointer.

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