Abstract: The present invention teaches an electro-acoustic guitar having an isolated resonant soundboard with or without an integrated transducer attached to the soundboard. The soundboard/transducer assembly fits into an aperture of the guitar body frame and has structure allowing it to be adjusted in multiple axes to provide the best playing action. The soundboard may also be interchangeable with other soundboards to further alter sound quality. String vibration energy is conducted by an acoustically pure bridge to the soundboard/transducer assembly. The large magnetic transducer is integrated by having one portion, a magnet structure, secured to a magnet support and another portion, the voice coil and mounting hub, secured to the soundboard spaced and opposed above the magnet support thus creating a truly integrated electro-mechanical soundboard transducer assembly with tonal qualities modified by an internal chamber defined by the space between the soundboard and the magnet structure support.

Abstract: A subsurface thermally autogenous reactor and method has downgoing and upgoing flow passages connected at the bottom to form a U-tube and in heat exchange relation to each other. The downgoing and upgoing flow passages each have an upper heat exchange section and a lower reaction section. An air injection system injects air into the downgoing flow passage between the heat exchange and reaction sections. The cross sectional area of the upgoing heat exchange section is greater than the cross sectional area of the downgoing heat exchange section to balance the downgoing and upgoing flow velocities. The downgoing heat exchange section has multiple tubes to increase the heat transfer area.