5.1 speaker placement

If I upgrade to 5.1, I'm wondering how easy it will be to place the speakers and have my 27" iMac be centered in the middle so I can work and listen without changing positions. I will be using speaker stands. It seems like the iMac would be too big and would block the center speaker. The speakers I have should not be placed horizontally. Is it okay to raise the speakers and tilt them down? Is it okay to have the center speaker be higher than the others?

It would help to have a diagram or model of your room, or photos, to better see what you are dealing with. For 5.1, there's an alternative that you might not have considered: use two video monitors, instead of just one, spread them apart a bit so that they are not blocking your center channel. That's what I try to do for 5.1, to avoid the very issues you are talking about.

The speakers I have should not be placed horizontally.

Good! Because speaker placed horizontally can create other problems, unless they are specifically designed to ONLY be used horizontally. Vertical is generally better. What speakers are they?

Is it okay to raise the speakers and tilt them down?

Yes, but with caveats! You can go to only about 10° downwards tilt. After that, you start creating psycho-acoustic issues with the way your ear and brain deduce direction of sound sources, so you upset the sound stage and stereo imaging. Some people say that 7° is the limit. Then there's also the issue of reflections: If you raise speakers and tilt them down, you are creating the perfect conditions for reflections coming off your console or desk to be aimed right back at your face. Bad. Then there's the issue of comb filtering and other phasing artifacts: Tilting the speaker down will create more prominent comb filtering form the desk(console surface. Not good. And there are other practical issues, such as if you have someone sitting on a sofa behind you: the speakers will be pointing at their feet, not their ears, so they will be way off axis, and therefore not getting clear, clean sound. The will tend to hear the mix more muffled and bassy than it really is.

Is it okay to have the center speaker be higher than the others?

Once again, you can, but it is not recommended. Take a loot at the ITU and EBU specs for 5.1 control rooms, to get a better idea of the geometry you need for your speaker layout, and how the room should be done. - Stuart -

The dimensions of the room are about 13'1" x 19'9" with about 9' ceilings before treatment. Originally I was going to build in a booth but now I will be using an adjacent room (on the short side) for a booth that is connected by a window, or alternatively I can use video cameras for monitoring. I did think about using two video monitors but thought I would primarily be using one so my head would generally be tilted to the side a little. Probably not a big deal though. I would actually want to set up three monitors, since the third monitor would be a larger display on top for viewing the video from Pro Tools, and that signal would be split and sent to a display in the booth also. The speakers I will probably be using are Dynaudio BM5A MkII's with a BM9S sub. Later tonight I will draw out some plans for the room. Thanks!

I have come up with this rough diagram with the speakers, sub, and computer scaled to size. The problem is I don't know where to put the computer if I want the speakers placed at the optimal height without having to tilt them down. If I'm sitting comfortably the tweeter level would be around 3'10" from the ground, with the bottom of the woofer at around 3'2" - the top of the iMac would be at about 4'2". The iMac would block the speakers, even if placed in between the center and left speaker due to it's width. I could lower the iMac down maybe 3" and tilt it up, then raise the speakers about 10", since the speakers might be roughly 5 feet away and tilt them down accordingly (maybe that would be around 10 degrees?) This may work better because the bottom of the speakers would then be at around the same level as the top of the iMac. Yes the speakers would be tilted down facing the desk, but maybe not too much...