Posted: April 15, 2015
I was asked by one of my clients to try to build an infrasonic wave emitter. After thinking about it for a while, I found myself planning a resonance chamber using a base drum (something I can’t believe had not been tried at that time).
I used a 22 inch base drum and 21 inch 2000 watt Pyle Pro speaker cone. The idea is that both the Pyle speaker and the base drum are engineered to produce sound in the lower audible frequencies. So my idea was to build a base cannon inside of the drum that resonates and amplify the drum head and speaker cone simultaneously while directing the air-wave blast-pulses.
My goal was to achieve a harmonic resonance between the 21 inch speaker and the 22 inch drum head by placing them at strategic distances from one another and by working with an awesome Pyle Pro amplifier.
The 1000W amp claimed to have a frequency response of 20Hz-20kHz and the speakers claim 22Hz resonance with a frequency Response from 22Hz ~ 4kHz. According to some 22 inch base drum tuning guides, the batter lug frequency can be as low as 55Hz but the resonant (post-lug) frequency of the drum head varies. When recording equipment like the Avenson STO-2 condenser is used (capable of picking up lower frequencies) the Kick-Port reportedly produces a low-peak below 20Hz.
I suspected it could reach sub 20Hz if motivated by a complex harmonic standing wave.
Theoretically, I sent the ~20Hz signal to the speaker and get ~21-22Hz to bounce off of the 22inch base drum inner chamber that causes a complex harmonic resonance and emits a strong infrasonic standing wave-boom – somewhere inside and throughout the base cannon drum heads and chamber.
My hypothesis is that this method works better than the standard sub-woofer box model because it is something of a cross between these experimental base cannons (http://www.instructables.com/id/800watt-12-long-16quot-diameter-Bass-Cannon/ – check the notes for a hilarious video) and a resonance chamber.
I thought about trying the so called base cannon idea, but I when working with my hybrid drum concept I was quite satisfied so I have not yet expanded on this project.
The tones I used to test the base cannon were generated here
I should have more news soon – I’m thinking earthquake simulation in the lab – haha – JK.