Filter Freq. Hz Control | JL Audio HD900/5 instruction

while the “Sub” channel filter is a low-pass filter (attenuates high frequencies). For each filter, the user can select from a shallow (12dB/octave) filter slope or a more aggressive (24dB/octave) slope.

1)“High-Pass Filter” Controls (Front and Rear channels) or “Low-Pass Filter” Control (Sub Channel): These switches allow you to select filter slopes or defeat the filter(s) completely.

“Off”: Defeats the filter completely. Useful when using an external crossover, such as one built into a head unit or signal processor.

“12dB”: Configures the filter to attenuate frequencies above or below the selected filter frequency at a rate of 12 dB per octave (Butterworth alignment).

“24dB”: Configures the filter to attenuate frequencies above or below the selected filter frequency at a rate of 24 dB per octave (Linkwitz- Riley alignment).

Depending on the speaker system and the vehicle, different filter slopes may be required to produce a smooth transition between the sound of different speakers in the system.

In high-pass mode, the sharper “24dB” setting will do a better job of protecting small speakers with limited power handling. In low-pass mode, the “24dB” setting can also help by more aggressively removing lower midrange output from a subwoofer system.

The shallower “12dB” octave setting allows for more output overlap between the speakers being crossed over. In many cases, this will result in a smoother “blend” or transition between speaker systems.

Experiment to find the slope or combination of slopes which best matches the acoustic requirements of your system.

2)“Filter Freq. (Hz)” Control:

This control selects the frequency at which the filter begins to attenuate the signal and refers specifically to the frequency at which output has been attenuated by -3dB.

The filter frequency markings surrounding this rotary control are for reference purposes and are generally accurate to within 1/3 octave or better. If you would like to select the filter cutoff frequency with a higher level of precision, consult the charts in Appendix B (page 18) of this manual.

“80 Hz” is a good starting point for most systems where a subwoofer is connected to the Subwoofer Channel and component systems or coaxials to the four main channels.

INFRASONIC FILTER (Subwoofer Ch. Only)

The “Infrasonic Filter” is a 24 dB/octave high- pass filter, with a fixed cutoff frequency of 30 Hz. This filter is designed to conserve amplifier power and protect subwoofer systems, without audibly degrading the sub-bass output.

With ported enclosures, the use of the “Infrasonic Filter” is highly recommended to protect the speaker(s) from excessive excursion below box tuning.

With sealed enclosures, the use of the filter is less necessary, but can still help protect the speaker system from excessive excursion.

The “Infrasonic Filter” can be completely defeated by selecting the “Off” position on its switch. This bypasses all signal from flowing through the circuit.