A rare trip to Lake Superior found river-class vessel Algoma Compass and her twin Kahlenberg Arctic S-5s in the Twin Ports on August 16, 2021. Departing Duluth, MN, with a load of taconite pellets, the Compass saluted the Aerial Lift Bridge and a large crowd of onlookers with a nice one-long, two-short blast. The bridge would respond in turn to complete the exchange.
The S-5 belongs to a classic series of marine air horns manufactured by Kahlenberg Industries, Inc. of Two Rivers, WI. Each model in the series has one, two, three, or four trumpets (bells) and comes in one of five sizes.
The number of trumpets that a horn has specifies the number of distinct tones it produces. For instance, a horn with two trumpets will sound a two-tone chord. Kahlenberg designates the number of trumpets with a lettering system as follows:
S = Single (1 trumpet)
D = Dual (2 trumpets)
T = Triple (3 trumpets)
Q = Quad (4 trumpets)
For each letter, a corresponding number 1–5 indicates the size of the horn, which also determines its pitch. The larger the number, the larger the horn and the deeper it sounds. Size 1 horns are smaller than and produce higher pitches than size 2 horns, for example.
Putting it all together, each horn in the series is given a designation of the form X-#, where "X" is a letter S, D, T, or Q, and "#" is a number 1, 2, 3, 4, or 5. A D-2 is a size 2 model with two trumpets, a T-3 is a size 3 model with three trumpets, etc.
An S-5 like on the Compass is a size 5 model with one trumpet. Sounding at a little over 100 Hz, it has the lowest pitch of any mainstream Kahlenberg S-type horns. Interestingly, this was the only size 5 horn offered by the company — to my knowledge, a D-5, T-5, or Q-5 never existed.
For S-type models, an Arctic variant was offered with an enclosed box insulating the aft end of the horn. This option was popular on Great Lakes vessels operating in frigid winter temps. The Compass has carried her twin Arctic S-5s atop her pilothouse her entire career.
Audio and images are my own.
Intro video by VartanMercadanti, pixabay.com, free license.
Intro audio by kbeezy88, pixabay.com, free license.
