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Jerry's Leslie Speaker Project

I recently picked up a vintage 1956 Hammond M-3 and restored it back to perfect operating condition. The

only thing that was missing was a Leslie speaker to go with it so I decided to build my own. This is my construction page illustrating the different stages of development and components. All exterior cabinet lumber was 3/4" cabinet grade Birch with 3/4 plywood and MDF for inside shelving. I used Minwax stain and polyurethane sealer to finish everything off. There are four smaller casters installed to make moving it around a lot easier. I designed it to be externally powered using a Hafler DH-120 so that I could use it with either my Hammond M-3 or any other synth. All components were obtained through Hammond parts suppliers online, Radio Shack, eBay or other available sources. To switch the motors (on fast, on slow or off) I use a SPDT (on-off-on) switch mounted on the front of the organ connected to a low voltage relay system using any 4-conductor telephone cable. This eliminates the need for heavy bulky wiring and keeps the voltages on that line low using a 12V power source. I may not have saved myself a whole lot of money but I do have the satisfaction of knowing that I made it myself to my exact specifications and it sounds great!

ac_terminal

This is the main 117v AC distribution connector.

power_distribution

This is the main power and control distribution block.

bottom_back

This again is the complete power and control distribution block.

power_control_audio_input

From left to right: audio inputs on panel, fuses to speakers, switching control plug with switching relays behind, power outlet for 12V power supply, covered AC connection terminal, rotor 2-speed motor.

12v_power_supply

The 12V power supply module provides power to the two switching relays.

control_relays

This is a standard 4-connector phone plug used to control the relay switching from a remote SPDT (on-off-on) switch mounted on the organ. The relays have 12V coils and SPST contacts which supply the 117V to the respective motors (fast or slow). Switch and relays can be obtained at any Radio Shack.

speaker_fuses

These are the backup speaker protection fuses for the horn and woofer.

800hz_passive_crossover

The passive 800Hz crossover was designed to provide a 12dB/octave split between the horn and woofer.

dayton_woofer

I used an 8 ohm Dayton 12" woofer to supply the lows from 800Hz on down.

horn_woofer_compartment

The woofer cabinet is a sealed enclosure design so all possible air leaks have to be sealed. You'll notice all the RTV sealing any holes where wires or anything else passes through the cabinet. All displaceable items such as the horn motor isolation box, woofer, horn driver and crossover assembly were taken into consideration when calculating the size of the enclosure so as to ensure optimum results. The horn driver is capable of handling 50 watts and the woofer 100 watts RMS.

horn_motor_assy

This is the horn motor assembly. The horn was purchased from TonewheelGeneralHospital.com. The bearing assembly is permanently sealed and never needs lubrication. The Leslie driver adapter plate came from bborgan.com. which allows the 250-5kHz driver to screw right into it nicely.

horn_motor_isolation_box