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If you?re serious about sound then you?ve probably put a lot of thought ? and money ? into your car audio system. Unfortunately, even the best components may sound crummy if your vehicle?s acoustics are poor.
What exactly are acoustics? According to Webster's Dictionary, ?acoustics? refers to the ?qualities that determine the ability of an enclosure to reflect sound waves in such as way as to produce distinct hearing.? In other words, it?s all the stuff ? road noise, electrical interference, vibrations, echoes, dead space, and a dozen other factors ? that combine to make an automobile a good or bad listening environment.
To put it as simply as possible, improving your vehicle's acoustics generally involves two things:
The road is a noisy place when you?re driving. Your engine makes noise, the tires make noise, the wind rushing over the car makes noise, and other vehicles make noise. To create a good listening environment, you need to reduce the amount of sonic clutter entering your car.The age and condition of your vehicle have a direct impact on the amount of noise intrusion you have. Older vehicles may have engine knocks or squeaky suspensions. Also, the seals around the windows and doors may be worn and brittle, allowing more air noise to penetrate. Also keep in mind that expensive cars such as BMWs and Volvos are generally quieter to begin with because of the engineering and quality of construction that went into the vehicle. A 10-year-old Pontiac will almost certainly be noisier than a Lexus of the same year.
 It's a good idea to consider your vehicle's acoustic properties when planning your stereo system.  Acoustics has to do with the behavior of sound waves in an enclosed space. |
If you?re serious about sound then you?ve probably put a lot of thought ? and money ? into your car audio system. Unfortunately, even the best components may sound crummy if your vehicle?s acoustics are poor.
What exactly are acoustics? According to Webster's Dictionary, ?acoustics? refers to the ?qualities that determine the ability of an enclosure to reflect sound waves in such as way as to produce distinct hearing.? In other words, it?s all the stuff ? road noise, electrical interference, vibrations, echoes, dead space, and a dozen other factors ? that combine to make an automobile a good or bad listening environment.
To put it as simply as possible, improving your vehicle's acoustics generally involves two things:
- Eliminating environmental ?noise? that interferes with music listening.
- Enhancing the mechanical issues such as speaker placement and interior surfaces that affect sound.
The road is a noisy place when you?re driving. Your engine makes noise, the tires make noise, the wind rushing over the car makes noise, and other vehicles make noise. To create a good listening environment, you need to reduce the amount of sonic clutter entering your car.The age and condition of your vehicle have a direct impact on the amount of noise intrusion you have. Older vehicles may have engine knocks or squeaky suspensions. Also, the seals around the windows and doors may be worn and brittle, allowing more air noise to penetrate. Also keep in mind that expensive cars such as BMWs and Volvos are generally quieter to begin with because of the engineering and quality of construction that went into the vehicle. A 10-year-old Pontiac will almost certainly be noisier than a Lexus of the same year.
KEEP IT QUIET
Regardless of the age or make of the vehicle, you can do certain things that will reduce unwanted environmental noise. One method of noise reduction is to install damping material around the vehicle cabin.
The term ?damping? is a physics term that refers to the changing of energy. Damping material, which can be installed in the doors, in the roof, under the carpet and behind the rear seat and fire wall, is typically a thin, flexible fabric that acts as a shock absorber for sound waves.
 A comparison of speaker panel distortion without Dynmat anti-vibration material (left) versus with an application of Original Dynamat shows a massive reduction of audible distortion. |
?Damping is all about energy conversion,? explained Scott Whitaker, CEO of the company that makes Dynamat, the leading brand of sound-damping material. ?You?re taking the energy of sound waves and converting it into a silent energy, which is harmless, low-grade heat. The result is a quieter cabin.?
 Applying Dynamat to the door panel. |
Whitaker said that a vehicle?s doors are usually the biggest source of noise intrusion and therefore the first place to install a damping material such as Dynamat.
?Installing Dynamat in the doors alone can reduce exterior noise so much that it sounds like a 3-5 dB boost in stereo volume,? said Whitaker.
In other words, eliminating the noise helps you hear the stereo better.
Depending on the condition of your vehicle, you also can reduce noise by buying new tires, getting an engine tune-up, and replacing that worn out muffler. Also try tightening loose bolts and hinges to reduce rattles.
 Equalizing the path lengths from your speakers to your ears is crucial for getting the best sound reproduction possible in your car. |
LOCATION, LOCATION, LOCATION
Generally speaking, automobiles have poor acoustic qualities. Scientists who study acoustics generally agree that the best listening environment will have soft, sound-absorbing walls, few obstacles that either deflect or reflect sound, and provide enough space so that all speakers are relatively equidistant from the listener.
With that in mind, think about your car. It has numerous hard surfaces (windows, dash panels, etc.) and lots of acute angles and ?dead spaces.? Dead spaces are areas within the vehicle that have little or no reverberation; in other words, it?s a space where sounds go to die. Furthermore, the driver ? the primary listener ? is located in the front left corner of the cabin, making speaker placement especially difficult.
?When designing a car audio system, the number one priority is positioning the speakers so they are equidistant from the listener and relatively unobstructed,? said Larry Pagelsdorf, a sound quality judge with 17 years of experience at car audio competition events.
Pagelsdorf said one of the primary objectives in speaker placement is to achieve ?time alignment.? Time alignment refers to the simultaneous arrival of sounds to the ear from different locations. A difference of even a fraction of a second reduces the realism and quality of the sound.
Given that the driver does not sit in the center of the vehicle, unless he?s driving a Formula One racer, it becomes difficult to achieve perfect time alignment. Some high-end head units provide built-in time correction, but most source units do not, so achieving true time alignment can be particularly difficult. If time alignment is a problem, then thoughtful speaker placement is essential for creating better time alignment and a more realistic sound.
Serious car audio competitors learned long ago that OEM dashboard speaker locations were a bad idea. Speakers mounted in the dash typically fire into the windshield creating all sorts of troublesome acoustic issues. Looking for alternatives, they found better locations in the doors and kick panels.
 Q-Forms kick panel enclosures can provide an excellent solution to the problem of speaker placement in a car. |
Mounting speakers in the upper portion of the doors often works well, but sometimes space is a limiting factor. Doors may not provide enough mounting depth for larger speakers, and door speakers may interfere with roll-down windows. The kick panel areas are a good option so long as the speakers are placed at the proper angle so they aim almost directly at the listener?s ears.
With regard to tweeters, it?s important to know that they should be mounted within 18 inches of the midrange speakers. Certain sounds are at such a frequency that they are divided between the mid-range and tweeter. The typical female singing voice is a good example. If the tweeter and midrange are mounted too far apart, the voice will be ?out of phase? and not realistic. So keep the tweeter and midrange in close proximity for accurate sound reproduction.
Most audio system designers will note that rear speakers are essential for top flight sound reproduction. Rear speakers, Pagelsdorf explains, ?fill in the sound.? Like dash speakers, rear speakers are more effective if aimed at the listener rather than the rear glass.
Bass speaker location is not as critical because subwoofer frequencies are multidirectional, but it is important that the sub be mounted in an enclosure that is designed to maximize its performance.
 Your amp's power cable can radiate electrical noise. Run the signal cables down the opposite side of the vehicle. |
Wiring is also an important design factor when creating a car audio system. Your vehicle?s electrical wiring emits interference that can be picked up by RCA signal wires. It?s therefore important to keep electrical wires and speaker wires as far apart as possible. Also, it?s best to use unshielded twisted pair (UTP) cable, as the physical relationship of the twisted pair helps prevent radiated noise (engine and electrical noise) from being introduced into the audio system.
It?s important to realize that your car is not a concert hall; it takes careful planning and some installation knowledge to create a good acoustic environment. With a little extra effort and expense, your car audio system can sound incredible.
