PARC flexible thin film audio speaker
- PARC Speaker are fabricated on 10-micron thick polyimide coated on glass.
- The PVDF: TrFE co-polymer is coated on the polyimide; thickness 20-25 micron.
- Gold top and bottom electrodes.
- Polyimide is removed from glass.
- Bi-morph structure.
- Two speakers bonded back-to-back.
- Speaker is very flexible – the black outer region is to provide some extra support
Unimorph and Bimorph structure
Modeling
- Amplitude with static voltage
- Bimorph gives about 6X increase in amplitude compared to Unimorph
- Linear dependence on speaker diameter
- 10-micron PI thickness is about optimal
Unimorph and bimorph Speakers:
- Unimorph operation
- Voltage causes film to stretch; converts to out of plane motion
- Bimorph operation
- Voltage applied with opposite polarity to top and bottom films causes structure to bend
- Modeling predicts that bi-morph amplitude is ~ 5x Unimorph amplitude
Sound Power Level (SPL)
- Frequency response is directional due to uneven speaker surface
- Loudness increases with voltage – 10’s V needed
- Confirms larger response of bimorph
- Response increases with frequency; can be flattened by filter circuit
- Low harmonic distortion
- Slightly curved speaker improves sound
In summary the Speakers are capacitors, High voltage (~50V or greater); low current. They work well and sound clarity is good. However, speakers need further optimization for loudness.
For more information contact Bob Street at street@parc.com.
