Originally Posted by jiang1202
Darinf , you have contributed several remarkable PRIR 7.1 which impressed me a lot, you mentioned that you didn't really care about 5.1sourse used in 7.1 PRIR, from my point, I think the LS and RS in 7.1 PRIR is nearer than in 5.1 PRIR, I guess if 5.1 sourse played in 5.1 PRIR will have better surrounding effect and better soundstage, because LS RS in 5.1 PRIR are more seperated and backed. Am I right on this point? Most of the Blue movie now are made by 5.1, if I am right on the point, I will be very happy to see some of 5.1 PRIR made by you in your later visit :)
Almost all the PRIR's I have posted have been from 2 channel speaker systems. So I am going to talk about this relative to making 7.1 or 5.1 PRIR's from 2 speakers...
If you look at the speaker placement specs for THX 5.1 and 7.1, the positions of the Ls and Rs speakers are actually the same. Their recommended positions are 90 to 110 degrees from front center.
The defaults on the Realiser for speaker angles is 110 degrees for the Ls and Rs channels.(See page 28 of the Realiser manual.)
I leave them that way for either a 5.1 or 7.1 measurement. The main reason is that it's not usually practical to get a 90 degree measurement on most 2 channel systems. To get a 90 degree measurement, assuming you can't move the speakers, you would have to do the measurement while "sitting" directly between the two speakers.
This is not possible most of the time since there is usually equipment placed directly between the two speakers.
Secondly you would be taking a measurement with your ears facing the side of the speaker. This would not give you a great measurement.
So, with a 110 degree angle, you can be slightly in "front" (towards the back of the room) of the two speakers. This is more practical since there is usually open space there and your ears are closer to the front of the speakers than the side. (Especially if the speakers are toed inward.)
That's why I don't think a 5.1 PRIR vs. a 7.1 PRIR would be really much different. I actually prefer the Ls and Rs to be slightly behind me even with 5.1 material. I suppose with the speakers at 90 degrees there is a tiny bit more distance between the speakers, but nothing that would dramatically affect the sound.
Technically the 110 degree speaker placement for 5.1 is still within the THX specs for 5.1 AND 7.1. So why not just do a 7.1 PRIR?
I am also usually trying not take as little time as possible when I am in someone's home or business. So, I don't have the luxury of doing separate 5.1 and 7.1 PRIR's. I would rather take the time to do multiple 7.1 PRIR's to make sure at least one of them turns out accurately. I always seem to find issues with my first PRIR attempts which get resolved in subsequent measurements, hopefully.
I don't think a 5.1 PRIR would sound any different than a 7.1 PRIR.