![]() Crossover networks use filters in high pass low pass pairs. These may be symmetric or assymetric and may (usually significantly) involve driver characteristics which affect slope, shape, and rolloff at both the high and low end. All of these and many variations for which no particular name has been applied also exist. The elliptic differs from the others mentioned in having "zeros" in the stop band. This means the roll off shifts between two rates and can even result, if the parameters are so adjusted, to show increases in drive in the stop band. Since most drivers would sound excellent with no crossover at all but would burn out and overload almost immediately, crossovers are necessary to prevent low frequencies which are beyond a midrange or Tweeters capability from entering them. It is also then necessary to use many drivers to cover the frequency range to enable frequency and load sharing and power handling. Some cone type drivers can achieve nearly full range and play adequately loud in car and home environments. Generally some bass and highs must be sacrificed. This type is found in many OEM cars due to low cost and compact installation. The Butterworth and Linkwitz-Riley |
difference to provide crossover designs that give better transient response. Transient respons degrades with greater order in practice. This audibly gives a system that has a character which remains embedded in the music over all musical sources. This character can overlay real information in the source thereby obscuring it. Usually the losses are barely noticeable up to an order of three. Beyond this the system can develop a character that is kind to various sources in that harshness is minimized but then information is lost when the very best recordings are used. Use of the elliptic in a fourth order configuration gives a transient response slightly better than a third order Butterworth and a roll-off rate slightly better than a fourth order of the same type. The same advantages apply to the L-R but in somewhat different proportions depending on the order.
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The net crossover in the CDT systemis designed to interface the mid woofer to the soft dome Tweeter to give optimum overall performance and consistent results. Only a loss in power handling and a custom in-car install and unusually delicate main drivers (not rugged miniature woofers) can provide a smoother more detailed easy listening experience. This can be accomplished with cone drivers that are both full range, crossed over to and interfacing with a Tweeter that uses its own mechanical properties to augment filter response. Each car requires different positions and settings and the settings are hyper critical. Although the networks are simple there are more of them.
Maximum sound quality can be so configured by providing special large expensive exotic drivers not easily installed - to achieve a demonstration of very detailed and moderately loud (by autosound standards) sound. Some show cars like this have been attempted with varying success. The CDT system gives a wide margin of power and precision with the easiest installation possible. Overlay character is held to a minimum giving unprecedented results short of a full all out custom show car - with a genious for a designer - on an unlimited budget. |