Filter Controls, Remote Level control Optional

Filter Controls

Most speakers are not designed to reproduce

the full range of frequencies audible by the human ear. For this reason, most speaker systems are comprised of multiple speakers, each dedicated to reproducing a specific frequency range. Filters are used to select which frequency range is sent to each section of a speaker system. The division of frequency ranges to different speakers can be done with passive filters (coils and/or capacitors between the amplifier outputs and the speakers), which are acceptable and commonly used

for filtering between mid-range speakers and tweeters. Filtering between subwoofer systems and satellite speaker systems is best done with active filters, which cut off frequency content at the input to the amplifier. Active filters are more stable than passive filters and do not introduce extraneous resistance, which can degrade subwoofer performance.

The active low-pass filter built into the M600/1 is designed to attenuate frequencies above its filter frequency, so that the system’s subwoofers do not reproduce any audible midrange content.

This serves to improve tonal balance and to avoid distortion. Correct use of the filter can substantially improve the fidelity of your audio system.

2)LP Filter Operation: The low-pass filter in the M600/1 is fully variable between 50 Hz and

500 Hz via the “Filter Freq.” control knob and features the ability to select between a moderate

“12dB” per octave or a steep “24dB” per octave slope via the “LP Filter Mode/Slope” switch.

Depending on the subwoofer system and the vessel, different slopes may be required to produce a smooth transition to the mid-bass speakers in the system. Experiment to find the slope which best matches the acoustic requirements of your system.

3)Precise Frequency Selection: The filter frequency markings on the front panel of the amplifier are for reference purposes and are generally accurate to within 1/3 octave or better. If you would like to select the filter frequency with a higher level of precision, consult Appendix B (page 13) of this manual. This chart gives you a more accurate frequency for each of the forty detented positions of the frequency selection control. This method can be very useful if the amplifier is mounted in

a location where you can’t see the front panel markings easily.

4)Defeating the LP Filter: The Low-Pass filter can also be defeated completely, by switching the “LP Filter Mode/Slope” switch to the “Off” position. This is useful if you are using an external active crossover in the system. With the internal crossover turned off, the M600/1’s upper frequency response limit is 500 Hz, due to its subwoofer-specific design.

INFRASONIC FILTER

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 and infinite baffle subwoofer systems, the use of the “Infrasonic Filter” is highly recommended to protect the speaker(s) from excessive excursion at inaudibly low frequencies.

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.

Remote Level control (Optional)

With the addition of the optional Remote Level Control (HD-RLC), you can control the subwoofer volume from a location of your choosing.

The HD-RLC connects to the jack labeled “Remote Level Control” on the Connection Panel of the amplifier using a standard telephone cable (supplied with the HD-RLC). If desired, multiple XD (and HD) amplifiers can be controlled from a single HD-RLC controller using a simple phone line “splitter” and multiple phone cables.

When connected to the amplifier, the HD-RLC operates as follows. At full counter- clockwise rotation, the audio will mute completely. At full clockwise rotation the level will be the same as if the HD-RLC was not connected at all. In other words, it operates strictly as a level attenuator.

8 JL Audio - M600/1 Owner’s Manual