The first loudspeaker I ever built was nothing more than a narrow rectangular plank of medium-density fiberboard with a 5″ driver haphazardly screwed into it, and a small base that let it stand upright.
It had a 1/4″ TS input on the front of the baffle, wired directly to the driver terminals with zip cord. The driver was an inexpensive car-audio midrange manufactured by Pyle. I had little understanding of T/S parameters at the time, and just wanted to throw together the simplest possible noisemaker. The driver wasn’t well-suited to an open-baffle topology in the first place, and the design was also compromised in other ways. The assembled loudspeaker lacked significant response below about 450 Hz; the driver had a bit more low-mid extension than that, but the response was limited primarily by the small dimensions of the baffle, for reasons that are explained in more detail in “Squawker 2.0.” Treble response extended to around 7 kHz.
While it was far too band-limited and unwieldy for anything resembling a casual listening application, it saw plenty of use as a guitar speaker; it worked well enough for casual practice, and it produced a useful ‘transistor-radio’ band-passed guitar tone that I used as an effect in several recordings. Its exaggerated upper midrange response also made it useful as a vocal monitor in band rehearsal, isolating and emphasizing the ‘vocal intelligibility’ range to provide clarity in the midst of a loud, guitar-heavy mix. A proper PA monitor would be positioned such that it was giving all of the musicians enough vocal to work with, and the Squawker would be run in parallel with this monitor and angled directly at the vocalist’s head to reinforce the vocal for them.
While this first design ended up being open-baffle simply because I was too impatient to attempt a proper enclosure, it sparked an ongoing interest in the open-baffle topology, especially for use as an electric guitar speaker. Open-baffle enthusiasts deride the literally ‘boxy’ resonances that come with putting a driver in a box, and they’re definitely on to something. Furthermore, the time-tested, eternally popular open-back guitar cabinet is only superficially different from open-baffle speakers designed for for hi-fi applications. Most of the disadvantages associated with an open-baffle topology become less of an issue when you are only concerned with a limited bandwidth, you can accept some beaming in the high frequencies, and coloration is not excused so much as embraced - all characteristics of typical guitar speaker cabinets.
In the next article in this series, we’ll look at an improved version of the Squawker, and I’ll include a more in-depth explanation of the ways that the open-baffle topology limits the low-end response of the design.