It doesn’t matter how you make an attempt to plan for a perfect sounding “Audio Listening Room” or “Home Theater”, there are focused adjustments that need to be achieved after you have purchased all of your audio equipment in your room and just have a listen to it very carefully. Even if you have listen to a wonderful set of speakers at a Hi-Fi or Home Theatre showroom or high-end audio dealer and decided to make a purchase. Note that the situation in your own home or room is going to be different and will require the services of a professional audio person. This person will specify what equipment your will need to enhance your amplifiers and speakers and then arrive on the scene with their Audio Precision rig to measure and calibrate the equalisers used to “flatten” your room response.
The question is, can you do this yourself without spending somewhere around $500? Conceivably, you might be able to move some diffusers and Bass traps around the room to minimise reflections and control bass nodes by ear. On the other hand you are only going to get marginal results unless you have a source of “Pink Noise”, a “Calibration Microphone” and a “Spectrum Analyser” to tell you where your problems are. Correct?
There are some selected current A/V receivers that have built in DSP powered room tuning setup procedures. Audyssey is one familiar example. When you have connected your speakers to the back of your A/V receiver, you will have to setup a small calibration microphone that comes with the amplifier. It has a small stand but you will probably have to use a small table to the ideal listening position to do the measurements.
Using the microphone located in the “sweet spot” you then navigate your way to the menu setup section of the A/V receiver. Once you have selected that, there are options for adjusting the sound parameters of the device, follow the instructions with your brand and model. These include setting the size of the speakers to either large of small depending on the speakers you have purchased. I am going to imagine that you have decided on large speakers. In spite of everything, you are looking to produce some reasonable sound pressure levels (about 85 dB SPL) with some good quality.
Note that you will also be asked to specify how far away the speakers will be installed 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 if you decide to combine surround music and have acquired 5 or even 7 speakers and a subwoofer.
When you have to the basic set up done, 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.
Note that there is no such thing as the impeccable room. This will never happen. A professional audio individual 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” (well balanced) 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 mentioned earlier that no room is impeccable. In fact, you may prefer to have a tighter 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. If you are looking to know more about audio room calibrations please check out the “Home Theatre Guide” by Alphonso Soosay.