Surround confusion

[Danartdis]

I hope this doesnt come off as sounding really uninformed but can somebody explain the differences between 5.1, (which I have a good handle on) 6.1 and 7.1. I think I understand the 6.1 idea is to have a center rear but what are side surrounds and is my HK obsolete now?

[Craig6519]

6.1 is a rear center, 7.1 is two rear centers, and if your familier with 5.1 then you already know what side surrounds are, well at least they should be at your sides in a 5.1 setup.

Craig

[prodj101]

I think 5.1 is good enough for now. the next step I make in home theatre is when instead of wallpaper, they can use electrostatic paper, and can use it as wallpaper for my room. talk about omni-directinal, lol. anyway, back to your question. 7.1 would have 4 speakers in the rear, and 3 in the front. 6.1 is just 3 in the back.

[Danartdis]

So on a 7.1 receiver there are left and right rear center channels? And there are DVDs that have 8 different tracks?

[boa12]

dan, the confusion comes by the use of the terms by the industry. they may call it 7.1 but the two rear surround carry the same info. so you could just as well use only one rear surround (a rear center) w/ no downmixing.

then there's those formats that use a matrixed rear surround channel like dolby ex & dts es 6.1 matrix, & a discrete rear surround such as w/ dts es 6.1 discrete.

check out the tech info at

www.dolby.com & www.dtsonline.com for all the details.

[Guest BobG]

7.1 calls for the primary surrounds on the side of the listening position and two rear surrounds. THX suggests those two rear center speakers be positioned very close together, something not more than 1 meter apart. Using the Advanced Speaker Array function in a THX Ultra2 processor, it is possible to steer the rear surround information to different combinations of the four surround speakers, generating both enveloping ambience and proper localization.

Without ASA, with both rear speakers playing identical information, it would be very likely that the rear center sound would appear to come from the front center speaker. This psychoacoustic effect is the reason for ASA.

[WMcD]

I never disagree with Bob.

However, I wonder about the issue that a mono source from two speakers behind is likely to be interpreted as a front center.

I have two Forte II at the office and they are located in corners behind me. I listen to WFMT (Chicago Classical) all day. The announcer is certainly mono. However, the voice and the music (stereo) always are correctly located behind me.

Now perhaps if the surrounds are directly at 90 degrees off center or slightly forward, which is in the range of recommended placement, then maybe there can be an ambiguity.

Thinking about it, maybe this is an argument for placing surrounds greater than 90 degrees from the front. We don't want "surround" to become "rear". Yet perhaps a bit of rear placement keeps them from becoming "front".

Regards,

Gil

[boa12]

for thx/dolby ex 7.1 the rear surround is matrixed from the same material as the discrete RS & LS channels.

i don't know about the advanced steering per se but it must be using some delay for effect. i use a single rear center for that "6th"channel & don't have that problem as its using material totally discrete from the FC channel.

i'd have to be pretty convinced that the sound using 2 speaks for rear surround would make that much dif to spend the extra money & most of all going to that trouble to set it up. do have thx ultra so maybe will give it a try some day.