High power directive speaker experiment kit components 10mmx 100pcs assembled

Description

If you hear ultrasonic sound long time, you may be damaged.
This is parametric speaker experiment kit.
This is complete assembled.
You can experiment directive sound beam.
High quality like FM radio. High pressure sound beam.
sound beam reach about 30 to 50m in silent room.
Kit including assembled PCB with tiny instructions.
This kit is based article of Elector magazine in March 2011.
Please read this article for details of kit.
10mm 100pcs ultrasonic transducers(black plastic type)
PWM driver PCB(SMD components are already assembled)
speaker level input( at least 1W or 2W)
You need 19V to 24V 2A DC power supply and source PA for PWM.
DC power jack is most popular 5.5mm type using laptop.
you need external sound amp.
PWM driver board is already assembled.
you need to solder speaker board.
please ask me more informations.
if you want more strong sound beam, I can offer for you.
If you have no knowledge of audio or electricity, don't buy this kit. This kit is for those who have the knowledge to perform experiments. If it connects but does not work, please tell me the detailed setting status. All kits are shipped after confirming that they work properly.