[Project Ryu] Field Coil Loudspeaker Mid-Bass Driver

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Hello,

Recently i have finished a pair of field coil mid-bass drivers. The driver has a Fs of 50Hz and a frequency response up to 7kHz. It is a dual voice coil design features a 160mm diameter motor with a max of 1.4T in the gap, Ryu spider, non-treated paper cone, triple roll cloth surround and bullet shaped phase plug.

 フィールドコイルスピーカー field-coil loudspeaker

 フィールドコイルスピーカー field-coil loudspeaker

 フィールドコイルスピーカー field-coil loudspeaker

The voice coil construction was presented in an earlier article here. Inside the gap set at around 1T flux density, the voice coil inductance was measured at 0.52mH @1kHz and 0.15mH@10kHz.

The high compliance of the Ryu spider was measured at around 3.4mm/N for this mid-bass and makes the compliance of the cloth surround the determinant factor in the system’s total compliance value.

 フィールドコイルスピーカー field-coil loudspeaker

 フィールドコイルスピーカー field-coil loudspeaker

Below you can see the impedance measurement and frequency response of these mid-bass drivers. The frequency response is measured with the voice coils connected in parallel. you can see a nice constant 6db/octave rise in response. You can use this characteristic when designing the loudspeaker if you consider baffle step or horn loading.

 フィールドコイルスピーカー field-coil loudspeaker フィールドコイルスピーカー field-coil loudspeaker

I have tested the unit and played Isao Tomita’s Snowflakes are Dancing and The Police Synchronicity. The sound is thin with the voice coils connected in parallel and no baffle but with the voice coils in series even without a baffle you can reach a good tonal balance. This indicates the unit can be used successfully in an Open Baffle system or in a horn loaded enclosure with the voice coils in parallel.

 フィールドコイルスピーカー field-coil loudspeaker

Thank you for visitng.

3 comments

  1. Serge says:

    ! horn loaded …that’s one a good candidate for a low-mid horns ….i have thinking about one speakers whose capable reproduce 80-500Hz , upper my mid horns ,lower an sub 15″ , or another bass speakers to reproduce 80Hz !

  2. Ed says:

    This is a phenomenal project! I have spent some time considering what driver I would build and this is almost exactly it: field coil, no dustcap, paper cone midrange. I would like to hear about the steel you used and your development process.

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