Getting Great Sound: Tuning Your Room

Getting Great Sound: Tuning Your Room

No matter hard you try to plan for a perfect sounding listening room or home theater, there are also adjustments that need to be made after you get all of your equipment in the room and have a chance to listen to it. Even if you’ve auditioned a wonderful set of speakers at a trade show or high-end audio dealer and decided to make a purchase, the situation in your own space is going to be different and require the services of a professional. This person will specify what equipment your will need to augment your amplifiers and speakers and then appear with their Audio Precision rig to measure and calibrate the equalizers used to “flatten” the room response.

Can you do this yourself without spending $500 or more? Perhaps. You might be able to move some diffusers and tube traps around the space to minimize room reflections and control bass nodes by ear. But you’re only going to get marginal results unless you have a source of pink noise, a calibration microphone and a system to tell you where your problems are.

There are some recent A/V receivers that have built in DSP powered room tuning setup procedures. Audyssey is one well-known example. Once you’ve got your speakers connected to the back of the A/V receiver, you setup a small calibration microphone. It has a small stand but you’ll probably have to push a piece of small table to the ideal listening position to do the measurements.

With the microphone located in the “sweet spot” you navigate your way to the setup section of the A/V receiver. Once you’re there, there are options for adjusting the sound parameters of the device. These include setting the size of the speakers to either large of small depending on the speakers you’ve purchased. I’m going to assume that you’ve decided on large speakers. After all, you are looking to produce some reasonable sound pressure levels (about 85 dB SPL) with some good quality.

You’ll also be asked to specify how far away the speakers are from the central listening position. This ensures that the sounds will reach you at the same time. The receiver inserts small amounts of delay based on your input measurements to optimize the phase relationships between the speakers. This is especially important is you have decide to embrace surround music and have acquired 5 or even 7 speakers and a subwoofer.

Once you’ve to the basics out of the way, you can begin the measurement procedures associated with “automatic” room tuning. There will be a series of sweeps output from each speaker. These low to high sweeps are precisely output and represent the reference against which the measure input of the microphone signal will be compared. An acoustically perfect room will have an exact match between the signals received by the microphone and the output from the speaker.

There is no such thing as the perfect room. This is not going to happen. A professional will then make a series of adjustments to either a one third octave equalizer that is inserted between each main output and its associated amplifier or a parametric equalizer. The automated system do much the same thing but they make the changes automatically inside the digital signal-processing core of the A/V receiver.

The basic idea is to introduce an equalizer that modifies the output of each channel in the exact opposite way that your room is distorting the sound. For example, if you space is allowing a large amount of bass frequencies to build up, then the bass frequencies will be attenuated by the external or internal digital EQ, Ideally, the results will be that the actual listening experience will be “flat” at the sweet spot.

There is a very delicate balance between making adjustments to the physical space and making adjustments electrically to the signals prior to them being sent to the speakers. I would opt for getting the room as balanced and “flat” as possible and then fine tune using equalizers.

As I said no room is perfect. In fact, you may prefer to have more low end in your room that would be called for by the measurements. This is your personal preference, of course, but be aware that professional studios spent a lot of time and money to deliver recordings that are predictable and consistent. Tampering locally with the sound as mastered is generally not encouraged.