Hi,
This is a work in progress based on an initial prototype (REV:A) and nothing is set in concrete yet so Id thought Id share some of the preliminary results I have achieved thus far which look very promising.
I was going to put this in the subwoofer section except the main goal of this device is for accurate bass reproduction of music using a servo controlled woofer in a sealed box, open or infinite (large wall or floor mount) baffle systems. Typically it would be used as part of a multi-way passive or fully active speaker system or a stand-alone subwoofer system used to complement an existing full range speaker that cannot cover the bottom octaves. It has a fully programmable active crossover feature that can be used as a two-way stereo system with two dedicated bass servo channels. Alternatively it can be set up as a mono 3 or 4 way active system including one dedicated bass servo.
The board is designed to interface directly to a highly linear and low noise industrial grade accelerometer, namely a Measurement Specialties ACH-01-03 accelerometer. A novel mounting method directly couples the accelerometer to the voice coil which minimizes base strain and thermal coupling to the accelerometer. This accelerometer features an integral shielded flexible lead and a +/- 150g capability with a 30KHz mechanical resonance. This is the same accelerometer used in a $50,000 reference speaker system for the same type of application. It can be purchased from a number of sources including Digikey and Mouser for as little as $20.
A simple design procedure using fully automated measurement to characterize the speaker and box simplifies the entire design process without requiring any specialized or expensive equipment. No PhD required in electronics or electro-acoustics ;) A servo woofer design can be implemented and operating in less than 30 minutes !!
Initial testing and measurements are promising with a maximum of 43 dB reduction in motor distortion achievable. Most commercial systems only provide between 6-12 dB reduction in THD.
Any questions and suggestions are welcome and any of the specifications are subject to change. I hope to make this thread a blog on my progress with this project so any feedback is welcome.
1st image - DSP servo controller,
2nd image - Test loudspeaker with accelerometer mounted to the voice coil,
3rd image - The whole setup,
4th image - Distortion results at 20Hz before feedback,
5th image - Distortion results at 20Hz after 30 dB feedback applied,
Regards
David
This is a work in progress based on an initial prototype (REV:A) and nothing is set in concrete yet so Id thought Id share some of the preliminary results I have achieved thus far which look very promising.
I was going to put this in the subwoofer section except the main goal of this device is for accurate bass reproduction of music using a servo controlled woofer in a sealed box, open or infinite (large wall or floor mount) baffle systems. Typically it would be used as part of a multi-way passive or fully active speaker system or a stand-alone subwoofer system used to complement an existing full range speaker that cannot cover the bottom octaves. It has a fully programmable active crossover feature that can be used as a two-way stereo system with two dedicated bass servo channels. Alternatively it can be set up as a mono 3 or 4 way active system including one dedicated bass servo.
The board is designed to interface directly to a highly linear and low noise industrial grade accelerometer, namely a Measurement Specialties ACH-01-03 accelerometer. A novel mounting method directly couples the accelerometer to the voice coil which minimizes base strain and thermal coupling to the accelerometer. This accelerometer features an integral shielded flexible lead and a +/- 150g capability with a 30KHz mechanical resonance. This is the same accelerometer used in a $50,000 reference speaker system for the same type of application. It can be purchased from a number of sources including Digikey and Mouser for as little as $20.
A simple design procedure using fully automated measurement to characterize the speaker and box simplifies the entire design process without requiring any specialized or expensive equipment. No PhD required in electronics or electro-acoustics ;) A servo woofer design can be implemented and operating in less than 30 minutes !!
Initial testing and measurements are promising with a maximum of 43 dB reduction in motor distortion achievable. Most commercial systems only provide between 6-12 dB reduction in THD.
Any questions and suggestions are welcome and any of the specifications are subject to change. I hope to make this thread a blog on my progress with this project so any feedback is welcome.
1st image - DSP servo controller,
2nd image - Test loudspeaker with accelerometer mounted to the voice coil,
3rd image - The whole setup,
4th image - Distortion results at 20Hz before feedback,
5th image - Distortion results at 20Hz after 30 dB feedback applied,
Regards
David