AES Technical Document on Surround Sound

[WMcD]

There is a nice publication by the Audio Engineering Society at:

http://www.aes.org/technical/documents/AESTD1001.pdf

The technical jargon may be too much for some (I had to chew on it).

It is problematic that "5.1" is used to describe both the number of speakers (this is a speaker hardware issue) and the number of channels of transmission and storage (this is a different issue). We have to be careful. I harp on this only out of the belief that it has lead to confusion, and deserves careful articulation. Forgive me for stating the obvious if you know all this. OTOH, we have people browsing the forum and this is part of the learning curve.

In any event, there are two nice diagrams.

The first sets out the ITU recommendation for speaker placement for 5.0 (without sub) and/or 5.1 (with sub) sound speaker set ups.

Note, "surrounds" are not in back, but just a bit to the rear of 90 degrees left and right. This would apply to systems using either Dolby Pro Logic (2 channel storage and transmission) or Dolby Digital and DTS (5.1 channel storage and transmission). The diagram just goes to speaker placement. The AES and ITU are not saying this is the only way, just a recommedation.

The second sets out a block diagram for the combination of LFE channel and additional redirection of the bass from the main channels. This assumes a 5.1

storage / transmission system as in Dolby Digital and DTS. I.e. 5 channels plus an LFE channel (0.1).

But this should be taken with a grain of salt in consideration of settings of "Small" and "Large" on the processor / HTS receiver.

It shows that the LFE (Low Frequency Effects) storage / transmission channel is sent to the sub. (It fails to show that if you don't have a sub, LFE is sent to whatever speaker is set to "Large"; or that your setting should be that.) The 10 dB amplification is just there to say that the gain is pumped up. room". Don't worry.

It also shows that bass below 120 Hz in the 5 other channels is sent to the sub. Note the use of L and L' (etc.) in the input and output of the processor, indicating that L' output means the bass has been redirected to the sub, or at least filtered out. Of course this assumes that any speaker with a prime (') has been set to "Small" in the set up of the receiver.

You might be setting only surround, e.g. LS and RS, to small. In which case your L, C, R, is still getting whatever is in the feed channel.

The .pdf document is well worth printing out and studying if you have questions about (1) a starting point for speaker placement and (2) LFE channel and redirection of bass from the other channels to the sub.

Please note this does not address a situation where the sub is getting its input from the speaker output wires.

Regards,

Gil

[Seb]

just wanted to say thanks and good one Gil!