DSP: Fixing what ain't broke
I want you to think about a scenario for me. It's a simple one. You own a taxicab and you smoke cigarettes. You're losing business because customers don't like the smell. Question: do you buy a scented piece of green cardboard and hang it from the rear view mirror, or do you stop smoking in the car? Both solve the problem, one might be better than the other. And to me, that sums up the dilemma of room correction using DSP: change the speaker to fit the room, or change the room to fit the speaker? There are few perfect rooms–perhaps there are none–and to maximize system performance it's necessary to modify the environment to to enhance the sound. Or, you can choose to change how the speaker produces sound so that it does not piss off the room. One method makes sense to me, the other seems twisted. How might DSP work if we choose to change the room through the speaker? Let's first understand what is happening. If I play a speaker outside, or in an anechoic chamber (room without any reflections), sound is delivered to my ears intact; what I hear is an exact copy of what is produced from the speaker. When I play that same speaker inside an enclosed area the walls act as both a filter and an amplifier: reducing the loudness of some frequencies, increasing the loudness of others. Let's imagine bass produced from a speaker in a room. If the room acts as I just suggested, we will have too little of one frequency and too much of another–we're all familiar with how this sounds. It is therefore a simple matter to use DSP's intricate tone controls to turn up the bass where it is missing, reducing it where it is too much. The result should be flat bass. If you now take your speaker and its DSP correction outside, you'd have too little bass in one area, too much in another–because the room has been taken out of the equation. The first problem with this solution may not be obvious. Our room is not a constant filter/amplifier. Where too little bass might be heard at the listening chair, all you have to do is move two feet in another direction and that hole will now be filled. Rooms are not consistent. Changes made through DSP are.
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