I would like to mention something that people often overlook, and that is having speakers that are compatible with your room. Acoustic products can solve many problems and refine any system, but have a hard time correcting for speaker/room mismatches. There are the obvious examples of having Wilson X-1s in a 12x14x8 room, or a pair of ProAc monitors in 30x26x14 room, but there is much more to consider.
Some guidelines I use:
Room size is the most obvious. Don't be afraid to ask the manufacturer of the speaker what room size will allow the speaker to work at its potential. If they say it'll work in any room, push harder. There is no speaker that I have ever heard of that is comfortable in any size room. Also consider where you will place them in the room. If like many you have the dreaded L-shaped room, you have to consider the dimensions of the portion of the room your system is in, AND the overall dimensions of the room which will greatly affect the bass frequencies.
Dispersion. Many people overlook this important detail. Often speaker manufacturers tout a narrow dispersion as this "causes the speakers to interact less with the room", pshaaaw! A narrow dispersion is most effective in an extreme nearfield setup, in any other configuration, they are VERY hard to make work properly. In my experience, narrow dispersion speakers interact with the room the worst, primarily because the frequency balance and phase characteristics off of the axis are often wildly inaccurate, and then these waves return to your ears causing distortion of the original signal. A wide dispersion will work well in most setups, and provides an enjoyable listening experience even when you are not in the sweet spot.
Dipolar, Bipolar, omni-directional, etc. These types of speakers demand more of your setup and listening space, but can be very rewarding in terms of soundstage spaciousness, and ease of listening. Obviously the most important criteria is how far from the back and side walls you can place the speakers. If you determine the distance by lifestyle requirements instead of the speaker's optimal distance, you will sacrifice imaging and tonal balance. They will work best in moderate to large sized rooms with a reasonable distance from the speakers to the rear and side walls. If you're limited on placement, non-rear firing designs will probably work best.
SPEND TIME ON PLACEMENT!!!
In a personal system, I will often continue to change speaker positions for up to a month. An inch or two makes a huge difference.
Start by adjusting the bass levels by moving the speakers forward and back until you find the right balance. Starting at 1/4 to 1/3 of the room is a safe bet. Next, set your midrange balance and soundstage width with the distance between the two speakers. Try to achieve a 75% (70-80 usually works) ratio of speaker distance to listener distance. For example, if you are 10 feet from the speakers, the speakers should be 7 to 8 feet apart. Finally for treble balance, adjust toe-in. Toe the speakers out for less treble, and in for more treble. For best imaging, toe the speakers out as far as you can until the center image starts to break up, and then go back just slightly.
Finally, measure. This is critical for proper placement. Use a point in the floor at your listening position and a point in the middle of, but right in front of the plane of the speakers. From the listening position point, make sure that the speakers are exactly the same distance from that point. A 1/16th of an inch even makes a difference. Then make sure that the speakers are the same distance from the forward point, and by measuring from that point to the rear corner of the speaker, ensure that the toe in is exactly the same as well. Once you adjust the speakers, you will have to check all the other measurements again since you moved the speaker. It can be time consuming but IT IS WORTH IT.
Happy listening,
Nathan
