In order to achieve the optimum performance from any home theater surround speaker system, it is imperative that the speaker system is properly placed and aligned. Perfect speaker placement insures the distance from the speaker to the listening seat is exactly the same, along with vertical orientation and toe-in angle. Keeping the speakers “on axis” delivers the best staging and response. Also as critical is the exact level adjustment for each channel. This set-up process can easily be accomplished with a measuring tape and a couple of specialized tools: a speaker laser alignment tool and a sound level meter.
Whether a direct or indirect speaker placement is employed (figure 1), use a measuring tape and place the speakers an equal distance from the rooms “sweet spot” and apart from one another. (The “sweet spot” is usually a room’s prime seating position for audio listing and visual viewing). Speakers placed on stands with the tweeters aimed at ear level (figure 2) offer the best overall performance. However if stands are not possible, wall/ceiling brackets can be used (figure 3). Also if possible, place speakers at least one to two feet away from walls.
Additionally, the center channel speaker should be place above, below or in front of video display. The subwoofer is non-directional and can virtually be placed anywhere in the room.
Once speakers are in place, the speaker system needs to be “fine tuned”. Professional sound engineers know that even the best trained eye or string line system will not be nearly as accurate as a laser alignment tool designed specifically for use with speakers. These specialized speaker lasers are usually mounted in aluminum bodies and are accurate up to 0.25″ @ 100 feet away. More importantly these lasers work three- dimensionally, unlike typical lasers sold by DIY retailers which operate in just two dimensions. When a direct speaker placement is utilized, aim each speaker’s axis toward the room’s “sweet spot” (figure 4). For indirect placement, use the laser to square-up each speaker’s axis in proportion to one another and the room.
The final procedure is adjusting the sound levels. Most multi-channel surround receivers and processors include a built-in tone generator with digital readout. However, these built-in systems are flawed since they rely on the users “ears” for adjustment rather than exact measurement. To circumvent this fault, a sound pressure level or SPL meter is utilized. A SPL meter is a small hand-held device which measures sound levels in “decibels” (dB).
While holding the SPL meter at ear level in the room’s “sweet spot” (figure 5), adjust the components master volume to a comfortable sound level and engage the tone generator. Using the SPL meter’s readout, measure and adjust each channels decibel level until equally matched.
This completes the surround sound speaker system alignment and measurement procedure. These tools and techniques will insure that any speaker system, from basic to the most exotic, will provide the maximum sonic performance.
Alan Adelstein is Founder and President of American Recorder Technologies, Inc., and has over 30 years experience designing and manufacturing high quality audio and video products for consumer and professional industries.
American Recorder Technologies suggested products:
SAS-1320 Speaker Laser Alignment Tool
SPL-8810 SPL Meter