Øyvind Kvålsvoll 20.08.2015 Download PDF
How to set up a Home Theater Sound System
26.03.2014: Minor updates for Room acoustics.
06.01.2015: Info for new immersive sound formats Dolby Atmos, Auro3D, DTS:X.
20.08.2015: Revised version. Updated content, more images, more on acoustics.
Placing speakers and seats
In a home theater or media room the options for speakers and seating placement are limited by the fact that when the screen is placed, all other items just have to follow.
Also, there may be interior design and practicality issues limiting the choices, and this is not wrong - the ideal home theater sound system is the one that suits the needs on that particular room, even if that means some compromises.
The Dolby/THX specification for speaker locations can be used as initial guideline for placement.
Start by placing the screen on one of the shortest walls, and not too high up. Then the locations of the main speakers are also determined - they go besides the screen, one on each side.
Next place the seats. If possible try to avoid the middle of the room or close to the back wall - these locations tend to have the worst uneven bass response. The worst place is close to the back wall - the reflections from the very close wall are bad for sound, and back surround speakers will have to be above listeners head.
If you have a center it goes above or below the screen. With the screen placed low it will be more relaxing to watch and there is plenty room above for the center speaker. Avoid placing the center low close to the floor, especially if there is a table or other furniture that comes close to or even blocks the direct path for sound from the center speaker.
If you have an acoustically transparent screen then all front speakers - left, center, right - obviously can be located independent from the screen, and the positions for best sound can be chosen. The center can then be of same type as the L/R, or at least it can be mounted with HF horn section at same height as L/R speakers.
Distance between L/R main speakers is recommended to form a 45 to 60 degrees angle for home theater. For music many will prefer a little wider soundstage, and that is perfectly good, space them a little further apart, and you will find that music sounds better and it does not have a huge impact on movie sound, the front stage just seems a bit larger and wider.
Surround speakers goes along the side and back walls, as shown in the picture 7.1 speaker placement guide. Height above listeners heads, or slightly lower if you are doing a complete Atmos system with ceiling speakers.
What happens if you do not sit in the middle between the main front speakers? Imaging will be compromised, so that the virtual location of sounds tends to be imprecise and move towards the nearest speaker.
In an old-fashioned audiophile set-up the listening position is precisely located on the center-line between the main speakers, because this location is where it is possible to experience the magic three-dimensional sound stage. In a theater, however, we also want to create the best possible experience for more than one listener, and obviously only one person at a time can be seated in the ideal position. As described in the chapter about main speakers, better speakers with controlled directivity is the clue to get better sound for all seats, in combination with a good center channel. And then you can still have good sound if you prefer to lie down on the sofa and need not worry that your ears now are slightly off center.
Subwoofer location affects the low frequency response, and the actual response is a result of room dimensions but also wall flex and damping, and any windows and openings. The best placement depends on room acoustic properties, practical and interior considerations, number of subwoofers available and subwoofer size.
One subwoofer is rather hopeless, but if that's what is available, try placing it somewhere between the front speakers along the front wall, asymmetric.
If you have followed the advice in this guide, you have at least two subwoofers. If you have good bass absorption on the back wall it may work well to place them in the front left and right corners. Often it is possible to get a better response by moving them away from the corners, somewhere in between the front speakers. If practical due to interior issues, a placement further back along the side walls towards the back wall can also give better results.
If you have 4 subwoofers, place them in the corners, two up front and two at the back. The idea is to place subwoofers on opposite locations from boundaries, to be able to fill in nulls, or holes, in the frequency response.
If you want to experiment with alternative locations for subwoofers this should be determined by acoustic measurements, with focus on placement to fill in the nulls - holes in the frequency response - as those can not be equalized.