What is the best speaker layout for a 7.1 system? A few years back I seam to remember reading that the rear speakers should be close together along the back wall but on the Dolby site they seem to recommend having them wider apart. Where I place the speakers will depend on were the entrance door is going to be placed so i have to get this right. I've attached a photo of the room layout.

Rob.

The close together placement you refer to is for THX placement and works best with a THX certified processor, you can place your rears about 10' apart, not in the corners. out from the wall if possible but that depends on the speakers as well, whether they are rear ported etc.
If you have multiple rows the sides should be between the rows and about 2' above seated ear level, rears should also be at that same level.
Fronts should be either behind the screen if a good AT screen or just outside of it, not against walls very slightly toed in toward the audience.
If behind the screen all three fronts should be tweeters at between 1/3 and 1/2 up the screen. [though I personally prefer 1/3 down from top]

Ok I see, So in you opinion would this layout work well from a sound quality point of view?

Cheers,
Rob

I would bring the fronts in more so they were no more than the distance of the outer edge of your seating and a bit more straight at em. just slightly toed in. and of course as I said pay attention to the height of them all.

If you have multiple rows the sides should be between the rows and about 2' above seated ear level, rears should also be at that same level.



As far as multiple rows and placement of side surrounds, there was a whole thread on that issue. If you place between the rows, generally you are optimizing for none -- and comprimising for all. So some suggest choosing one row as the "prime" row and optimizing for that row. So that way, at least some people have optimized and not comprimised sound for the side surrounds.

I have 2 rows, but since 90% of the time, it will be my wife and I, I chose to optimize for the 1st row (the row we sit in), and placed the side surrounds directly to the sides of the 1st row.

Ok, this might be a dumb dumb question, but what happens if you put in 4 pairs of sides? 2 for each row? Does that work? Is that what the regular movie theater does?

You can use dipoles between rows as well, that works quite well.

You can use dipoles between rows as well, that works quite well.

The thread I referred to was mostly discussing dipoles as side surrounds.

Since the recommended place for dipoles is directly to the side of the listener (so you are in the null). So in between rows kind of destroys that for both rows.

The thread I referred to was mostly discussing dipoles as side surrounds.

Since the recommended place for dipoles is directly to the side of the listener (so you are in the null). So in between rows kind of destroys that for both rows.

where is the thread you are referring too? I don't find that to be the case at all.

You can use dipoles between rows as well, that works quite well.But then no one gets the intended effect.

Dipoles have opposing sets of drivers wired out of phase. The phase cancellation creates a null (quiet zone) in between the forward and rearward facing sets of drivers. The idea is place those speakers directly to the sides of the listeners, so that the entire row is in the null. This way, listeners get very little direct sound and are instead enveloped primarily by reflected sound from nearby walls.

Placing dipoles in between rows will mean that none of the listeners end up in the null. In fact, both rows will have drivers pointing towards them, firing direct sound instead of diffuse envelopment. If that is the effect you want, better to use bipoles or wider dispersion monopoles. Why use speakers that generate an acoustic null if you're not going to take advantage of that unique feature?

Sanjay

A few years back I seam to remember reading that the rear speakers should be close together along the back wall but on the Dolby site they seem to recommend having them wider apart.I would go with the Dolby layout: side speakers at +/- 90 degrees, rear speakers at +/- 150 degrees. Same as in the diagrams you posted.

Spreading the rear speakers apart improves imaging stability, makes for smoother pans, gives better rear envelopment and allows left-vs-right separation to be heard behind you (can't hear "stereo" when the speakers are right next to each other).

Side speaker placement is easy: they go directly to the sides of the sweet spot. This is the same location that you'll be calibrating levels and distances from, so it makes sense to place your speakers based on this location too.

For rear speakers, measure from the sweet spot to the back wall and multiply by 1.2 to get the rear speaker spread. For example: if your back wall is 3.5 meters away, then the rear speakers should be placed 4.2 meters apart. That will put them at the +/- 150 degree points.

Finally, as caesar1 points out, trying to optimize for all seats will result in none of the seats being optimized. Imagine if you set time alignment based on an average distance of multiple seats. There wouldn't be a single seat with the correct speaker delays dialed in. Better to have one row optimized and one row compromised than have both rows compromised.

Good Luck,
Sanjay

Wow- I just looked at the THX recommended 7.1 speaker settings. They recommend placing the rear surrounds next to each other! If that's the case, why not just go 6.1?
http://www.thx.com/home/setup/speakers/back.html

CJ

Wow- I just looked at the THX recommended 7.1 speaker settings. They recommend placing the rear surrounds next to each other! If that's the case, why not just go 6.1?
http://www.thx.com/home/setup/speakers/back.html

CJ

'cause 7 is a bigger number and there for has to be better, right? ;) :p

One thing that McCall referenced but I don't think got across completely due to the lack of further discussion (save a few misplaced jabs) is the THX ASA processing. At least, I remember it as ASA, but that could be wrong. The first decision to make is are you going THX or not. If you get a THX receiver, you will have access to the ASA processing mode for the rear surrounds. In this mode, you place them next to each other and the processor does something sexy to make it sound cool for both HT AND Music. I don't know the details, but you can get them at THX.com.

So, basically, are you using a THX processor?

If you are, do you want to use ASA?

If you do, use the rear channel in the center as per the THX spec.

If you don't, use the separated dolby spec for the rear surrounds.

Ok Im still confused, I'll list my gear maybe that will help.

Meridian 561 processor, will be upgrade down the line to a 861
DSP5500 for FL and FR
DSP5500C for Center
DSP5000 for Sides and Rear

These are all front firing tower speakers. The front and sides I can play around with placement but the rears I have to get right as they will determine where the entry door goes. I think i would like them optimised for HD DVD AUDIO.

Rob

dsp5000:

Maybe its just me but I would suggest that you recheck your drawings and measurements, the angles you have drawn do not look correct. Especially the rear angle of 150 degrees.

Bill

I didn't draw or check the angles in the first image. They came from the dolby PDF and i just pasted it into my drawing. Will check tonight. Don't go to the DTS site for speaker layout recommendations!! They have 8 different versions for 7.1! It seams to me that there really isn't a definitive setup.

Rob

I didn't draw or check the angles in the first image. They came from the dolby PDF and i just pasted it into my drawing. Will check tonight. Don't go to the DTS site for speaker layout recommendations!! They have 8 different versions for 7.1! It seams to me that there really isn't a definitive setup.

Rob

It's probably because 7.1 Processors all have their own unique "way" to do 7.1. So you really need to either use a standard method, such as the one on the Dolby site (and NOT use a custom one such as THX ASA), or you need to find out what your processor needs for optimal sound.

I paged through both manuals (561 and 861) and didn't see anything in there on THX ASA. So I'd probably go with the dolby spec.

It can all be summed up as - match your speaker layout to your equipment. I'd guess anything will support the dolby speaker placement. But read through your manual for your processor and make sure there's not a contradictory suggestion.

If you get a THX receiver, you will have access to the ASA processing mode for the rear surrounds. In this mode, you place them next to each other and the processor does something sexy to make it sound cool for both HT AND Music.It's basically a Spatializer-like effect that makes speakers sound further apart than they physically are. When doing initial set up on a THX receiver, you dial in how far apart your rear speakers are and the amount of ASA used will based on that separation. The closer together, the more ASA is used. There's no reason you can't place the rear speakers like the Dolby diagram. The THX modes will simply use less ASA processing. Which I guess is kinda sexy, now that you mention it. It's probably because 7.1 Processors all have their own unique "way" to do 7.1.Most use PLIIx to extract surround-back information; a few add the THX option. But aside from that, there's really not many unique ways to do 7.1.

Sanjay

the angles you have drawn do not look correct. Especially the rear angle of 150 degrees.That's 150 degrees from centre (which is zero degrees; sides are 90 degrees, directly behind is 180 degrees). The angles measure correctly in the drawings.

Sanjay

It's basically a Spatializer-like effect that makes speakers sound further apart than they physically are. When doing initial set up on a THX receiver, you dial in how far apart your rear speakers are and the amount of ASA used will based on that separation. The closer together, the more ASA is used. There's no reason you can't place the rear speakers like the Dolby diagram.

Let me caveat this with saying that I've never setup a 7.1 THX system. However, the documentation at THX.com states that:

The left and right surround back speakers are direct firing, placed together on the back wall to take maximum advantage of THX’s patented Advanced Speaker Array (ASA) technology. Using this speaker setup, THX ASA digitally reconfigures the surround channels to recreate the appropriate sound fields for movies, music and games.

To me, it sounds like they are using some sort of processing to give a "separation" feel for a "7.1" experience, and just using a "flat" processing to generate a "6.1" experience. If you separate the rear channel, it'll probably make the 7.1 better and the 6.1 worse. For a dedicated HT, separating might be better, but I'm kinda just talking out of my arse.

interesting topic to follow

If you separate the rear channel, it'll probably make the 7.1 better and the 6.1 worse.Even with the rear speakers spread well apart, 7.1 can image sounds directly behind the listener when required. PLIIx normally runs the two rear speakers in stereo, but when applied to EX/ES encoded soundtracks, it can send dual-mono content to the rear speakers, so those particular sounds will phantom image inbetween.

Sanjay

Most use PLIIx to extract surround-back information; a few add the THX option. But aside from that, there's really not many unique ways to do 7.1.

Sanjay

There is Logic 7 for those that have Lexicon and some Harman Kardon etc. receivers. LOL
Just trying to muddy the waters :p

I actually often use L7

Even with the rear speakers spread well apart, 7.1 can image sounds directly behind the listener when required. PLIIx normally runs the two rear speakers in stereo, but when applied to EX/ES encoded soundtracks, it can send dual-mono content to the rear speakers, so those particular sounds will phantom image inbetween.

Sanjay

With that being so, why would THX.com recommend this speaker layout?

Just trying to muddy the watersYou bad girl you! I didn't mention LOGIC7 because it's not commonly available and I didn't want to confuse the issue. I actually often use L7PLIIx tends to have more precise steering in the surround field, so that's what I usually apply to movie soundtracks. L7 gives better wrap-around envelpment, so that's what I always use with music. Both are good technologies and I couldn't decide which I prefered. So instead of forcing myself to choose one or the other, I make good use of both.

Sanjay

You bad girl you! I didn't mention LOGIC7 because it's not commonly available and I didn't want to confuse the issue. PLIIx tends to have more precise steering in the surround field, so that's what I usually apply to movie soundtracks. L7 gives better wrap-around envelpment, so that's what I always use with music. Both are good technologies and I couldn't decide which I prefered. So instead of forcing myself to choose one or the other, I make good use of both.
Sanjay



so do I, He He.
I also love to use 2 channel surround for instrumental music. Talk about enveloping!