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Little-known Secrets of the Soundroom

You could fall in love with a system in the sound room, only to want a divorce once that same system is installed in your car. This is because there are big differences between sound rooms and your car. Listening area, listening position, and something called “transfer function” can all make the sound in the sound room much different from the sound that ultimately ends up in your car.

Room vs Car

A sound room is different than your car. A sound room is just that (a room), while a car is, you get the idea. It’s apples and oranges. A room has flat, hard walls set far apart. A car has any combination of soft curves and plush padding, hard vinyl and metal, all in an irregular space about the size of a refrigerator box. It’s rare that you get to test a car audio system in an actual car, so you need to know the secret to turning these two completely dissimilar listening environments into more hospitable conditions.

Beware of Transfer Function

That’s difficult because of a complicated physics equation called “transfer function.” Transfer function is a measure of how the volume of an enclosure, such as a room or a car, effects the way a speaker sounds. A loudspeaker in your living room sounds different than a loudspeaker in your closet because the living room is a larger space, and thus puts less pressure, or “backward load,” on the speaker. A loudspeaker in your closet sounds a lot like a speaker in your Miata, though, because they are both small, enclosed spaces.

You can get a good working demonstration of transfer function by listening to your current car audio system with the windows rolled up tight, and then with the windows rolled down. You’ll hear that the bass is louder with the windows closed. That’s transfer function at work for you. Remember that when you hear a speaker in a showroom, it will have less bass than it will have in your car.

Dead Rooms and Live Cars

A “live” environment is one that is filled with noise. Your car audio system has to compete with your car’s engine, other car’s engines, sirens, road noise, and the sounds of the angry drivers you’ve cut off (just kidding!). None of that exists in the sound room, which is “dead” to extraneous sound (especially if it is an insulated, padded space). Professional car audio installers will often deaden a car’s sound the same way room builders do when they build sound rooms. They apply padding, fill gaps in doors and behind dashes, tint windows, and even coat the inside of exposed metal with a dense, sound-damping adhesive materials.

Listen Different

So the best way to listen in a sound room is to try to duplicate the listening experience of your car. Keep in mind what kind of car you drive. Is it a big boxy metal car, or a snug soft two-seater? As a rule, different types of cars treat sound differently. Basic models, with lots of plastic and metal, tend to make highs louder, while more luxurious cars, outfitted with soft fabrics and more padding, will dampen the highs and make bass fuller. Keep the characteristics of your car in mind when you’re standing in the sound room.

And maybe standing in the sound room is the wrong position in which to listen to car audio demos. Do you listen to your car speakers while standing in your car? Sit down in the sound room, with the speakers you’re testing at dashboard level. Notice where the speakers will be placed in your car. Are you sitting off-axis, or directly in line with them? Pick an optimal pathlength by estimating how far from the speakers you will be sitting when you’re in your car. Are you testing rear speakers? Don’t stand in front of them, since that’s not how you hear them in your car. Turn around and sit facing away from them.

By keeping the differences between the room and your car-there will always be more bass response in the enclosed area of your car-in mind when you’re testing out car audio, you’ll be more prepared to make the right decision when it comes time to buy the best sounding system for your car.

This article was last modified Apr 17, 2014

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