Pro Logic II - high frequency interference - is this normal


New member
Username: Docrob

Post Number: 1
Registered: Jan-07

I'm new to all this surround sound stuff so excuse my ignorance. Just got Onkyo TX-SR674E AVR and Monitor audio surround 5.1 (4 x radius 45 and radius 180 centre + 360SW).

I've set it all up with automatic setup which callibrates everything. When i listen to Sky TV program or any stereo input (ie freeview) through Dolby PLII or Neo 6 the surround speakers and 2 fronts have noticeable high frequency interference (a sort of whispering), particularly when people are speaking. - i can only hear this if my ear's right by the speaker though, not normal listening position.

When i change back to all channel stereo, stereo, all mono etc all the speakers are fine and sound perfectly clean.

I have good QED micro speaker cable and good quality optical interconnects.

The AV shop i bought it from have tested it and said that's normal signal degredation as the signal is being processed from stereo to 5.1 - i can understand the logic but i was hoping for around £1K I would get a much cleaner surround from stereo input.

The other thing which is a factor is my surround speakers are about 2m from listening position so are louder (and so is the interference) when you put your ear to them.

To be fair you cannot hear this interference in normal listening position.

I just wanted some reassurance that this is indeed normal for AV recievers with PLII and other similar processing such as Neo 6.

When I use Dolby Digital the sound is great and what i would expect for surround sound. It's just i hoped i would get a similar experience with normal TV. I presume i'm asking to much.

Look forward to any replies.

Bronze Member
Username: Usernamex


Post Number: 40
Registered: Oct-05
Hi Rob, have you compared PLII from another source to sky/freeview? An audio book or maybe director comments in stereo to PLII fom a dvd might be a good comparision?

You'll then know whether the issue is due to SKY/Freeview. Also, you didn't say what PLII mode you were using ("PLLII movie" or "PLLII music").

Bronze Member
Username: Usernamex


Post Number: 41
Registered: Oct-05
Also, what is "good QED micro speaker" cable? The "micro" bit made me feel uneasy... just checked wire is 1.25m csa... maybe 16 awg? Hmm, the amp claims 150w / channel, and I'm familiar with the speakers. My opinion is the wire is just too lightweight, and more ideally suited to a lower power micro system. The concern is your amp has to work harder to produce the same volume with lighter wire (Think of a pump with a thin hose attached). I think you'd be better off with something 12 awg (3.5 to 4 csa) or better. However, I do doubt it has anything your PLIII query.

I'd also better preface my comments too... I think speaker wire is one of the most controversial topics in hifi. I'm of the school of thinking that well made cable of the appropriate gauge and spec for the run required is the more important than any fancy embellishments. That said I think my comments about your wire being too light is on fairly safe ground. Most of the arguments centre on whether very expensive cables can add much more performance than plain 12 awg zip wire, and whether cabling can sound different.

Its probably worth a new post to be fair

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