“Boose” 2-way waveguide speaker cooler

The “BOOSE” speaker was a project I did with one of my classmates for our final design project in a transducer theory course I took at UM.  The project requirements were pretty simple – build a 2-way speaker that sounded good.  Because of the vague guidelines, we decided we weren’t going to just build a generic box speaker – everyone else was going to do that.  Since we both enjoy our beer, we joked that we should build something that serves or holds beer.  The joke gradually turned to reality as we brainstormed together.

The result is a 2-way waveguide speaker using a standard Coleman 5 gallon drink dispenser and an aluminum dryer duct for the waveguide.

The picture here shows the arrangement of the dryer duct waveguide inside.  As with all waveguide speakers, the overall length of this tube had to be tuned to 1/4 the wavelength of the resonant frequency of our bass driver.  The use of the dryer duct made this adjustment quite easy, although we were aware of the poor decoupling it provided with the outside world (the liquid or air in the cooler).  We were designing a conversation piece, not a hi-fi speaker system.  Note that the entire speaker assembly is inside or attached to the lid so that it can still be removed like normal from the container.

The picture below shows more detail of the lid assembly.  We built a custom crossover to fit inside the lid (between the upper and lower plastic) so that it would be safe from any splashing liquid in the cooler.  The picture shows after the crossover had been installed, with leads exiting the lid for the bass driver and tweeter.  Food-safe silicon sealant was used to seal the duct to the lid.

Each driver mounted to a 90 degree elbow of the appropriate size.  For the bass elbow, much effort was spent to get the best seal between the elbow and the cooler lid/ dryer duct so that no air could escape at any junction.  A strong plastic glue was used to create the initial bond between the bottom edge of the bass elbow and the top of the bottom layer of plastic in the lid.  A JB Weld plastic putty product was used to create a nice aesthetic blend between the PVC elbows and the lid.

The drivers had to be sealed directly to the PVC elbows using silicon sealant.  Although this means any repair work will be very difficult, we couldn’t think of any other mounting that would look clean and be cheap.  Instead, we just took extra care to avoid cold solders or any other dodgy construction techniques.

The speaker actually did quite well in our RTA test of the speaker.  I’ll have to redo the tests though to get another screen capture of the results.