Audio quality and performance specs
The way that a car stereo sounds is primarily dependent upon the specs of the amplifier (whether built-in or external), and the number, configuration, and quality of the car's speakers. The presence of a dedicated subwoofer, for example, gives drivers a more immersive bass feel; and component speakers (woofers for low-range output, midrange speakers, and tweeters or super tweeters for high-range output) used in conjunction with external crossovers deliver better audio reproduction than full-range (or all-in-one) speaker assemblies.
External--rather than built-in--amplifiers also generally lead to increased power and a clearer output. The options for external amplifiers, in-car speaker arrangements, and other external components are limitless and beyond the scope of this buying guide, but some things to look out for when shopping for an external amp are: power ratings (usually rated in ohms); separate volume controls for front and rear channels; and the presence of high- and low-pass filters.
When shopping for a car stereo, there are a number of features to look out for in order to optimize audio quality. First, decide whether you are intending to use the stereo's built-in amplifier or whether the output is going to be channeled through an external amp. For stereos with built-in amps, some key considerations include:
Power rating:
Always use the RMS rating (measured in watts) rather than the peak power rating. RMS is an indication of a system's continuous power used for consistent output rather than its maximum capability.
EQ controls:
Most stereos come with some kind of equalizer for enabling drivers to tweak the bass, treble, and midrange bands. Advanced systems have four-, five- or even seven-band equalizers, and give the driver control over the center frequencies for each band for the smallest tuning tweaks.
Crossovers and high- and low-pass filters:
Some stereos such as the Eclipse AVN 6600 feature user-configured crossover settings, which let drivers set the frequency at which audio signals are sent to a specific band. Adjustable high- and low-pass filters work in a similar way by reducing or blocking output that is under or over a specific frequency before it gets to selected speakers. For example, a high-pass filter might allow only frequencies over 2000Hz to play through the tweeter speakers. In this way, the speakers are protected from damage and only those sounds intended for a certain acoustic range are amplified, leading to a more refined output.
For those audiophiles who want to route their audio through an external amplifier, the preout connections are a key consideration when shopping for the stereo head unit itself. Preouts are RCA connections required to connect your stereo's output to an external amplifier. Advanced systems will have more powerful preout configurations of four, five, or eight volts, which deliver a better signal to the amplifier and result in a clearer, brighter output. Basic stereos will come with one or two pairs of RCA preouts (allowing a limited number of amps to be connected), but advanced systems can have up to five.
