JBL 400GTi, 500GTi System Connections, Lead instrument fundamentals without a crossover point

that the 400 and 500GTi should always be connected in the same polarity as the tweeter however. It is possible, that due to the difference in the distance the sound travels from the woofer/midrange to your ears compared to the distance from the tweeters in a typical system, and the short wavelengths of sound at the crossover frequency, that a connection where the tweeters are connected in reverse polarity from the other drivers in the system may actually result in better sound. Because there is no way to accurately predict this before installation, we recommend that you try the connection both ways, and leave it in the polarity that gives the smoothest audible transition between the woofer/midrange and tweeter.

System Connections

There are a variety of system options available with the 400 and 500GTi. The simplest configuration is to use the 400 and 500GTi connected in parallel to a tweeter which includes a high-pass crossover such as the 08GTi, GT03 or GT07. Because the 400 and 500GTi is specifically designed for mid

frequency operation, it should have its high and extremely low frequencies blocked by electrical means in order to achieve the best system fidelity and the widest dynamic range. For the best performance, we recom-

mend that an active crossover with a minimum of 12dB per octave slope be used for the transition point between the subwoofer and the 400 or 500GTi. The optimum crossover frequency for this transition is de- pendent on the specific components used, the vehicle, and other installation details. As a general rule, the crossover frequency should be as low as possible to achieve the best sys- tem imaging. You can fine-tune the crossover after the installation is complete for the best sound. A good place to start your tuning process is between 50Hz and 150Hz when using the 500GTi and between 80Hz and 150Hz when using the 400GTi. In 4-way sys- tems using a midbass driver such as the 600GTi, the crossover point may be raised higher without detrimentally affecting imaging as long as the midbass drivers can be mounted reasonably close to the midranges. This higher crossover fre-quency will allow the system to play louder. Since no crossover is

perfect, it is advisable to keep your crossover points away from the range where your hearing is most sensitive. Therefore we recommend that you try to keep the high-pass frequency below 250Hz and the low-pass above 2500Hz. This lets the 400 or 500GTi reproduce the entire range of frequencies, covering the most important vocal and

lead instrument fundamentals without a crossover point.

If you prefer to use all passive crossovers, you will need to construct or purchase either a low-pass or band-pass filter for the midrange driver and match it to a high-pass filter for the tweeter. When a matched GTi Competition Series system is used, the best crossover choice is the laboratory-optimized, system-matched crossover which is included with the 408GTi or 508GTi system. If you have not yet installed your components, we suggest that you consult your dealer for this system package.

The most advanced system designs use active electronic crossovers such as the JBL GTX2, GTX4 or GTX47 at both the subwoofer(or midbass) to woofer/midrange transition point and at the woofer/midrange

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