The K series of horns was introduced in 1954, one year after the P series was first unveiled. However, the K series was a much more refined horn. The K stands for "kettle drum", which is what these horns were adapted from. Unlike the P series, these horns use a two-disk diaphragm with a layer of silocone along the edge, making a sealed air chamber between the diaphragm disks. Robert Swanson's idea behind this was to make a horn sound as close to a steam engine as possible, including the typical raise in pitch as more air is applied. Swanson hoped the kettle drum idea would provide this effect, though it did not. It did, however, virtually eliminate the pitch drop present in nearly every other horn, a significant feat on its own.

K horns were offered in a three and five chime configuration since their inception, both tuned to the government mandated D# minor chord. It wasn't until 1977 that the K horn line would see any significant change. Deane Ellsworth, working for Amtrak, worked with Robert Swanson in 1975 to change the tuning of his K5 horn. He had wanted to make a horn that sounded like the old M5 for use on Amtraks new locomotives. By boring out the 3 and 4 bells, it turns out that the K5 was transformed into a horn playing the D# major 6th chord, only one step higher than the M5's C# major 6th. However, the first prototype K5LA, as the new horn became known, was actually used on the Chessie system in 1976. This horn unfortunately disappeared after only a short time.

At this same time, AirChime purchased a die-casting machine, and die-cast K5LAs started appearing in 1977. The first die-cast K5LA was presented to Deane Ellsworth for use on Amtrak, and today is saved in a private collection. Aside from the prototype K5LA, which was sand-cast, all K5LAs, and all K horns produced after 1976, are die-cast horns. The sand cast horns tend to have a more mellow tone to them, but thankfully the die cast horns remain true to Swanson's specs; unlike the P series horns, the chords of K series horns have remained unchanged throughout their lives. Since the introduction of the K5LA and die-cast K horns, no significant changes have occurred to the K horn since.

		bdrv8159_011218_5.wav	a K3H, Canadian-tuned, in active service
		k3la_030614_1.wav	the American-tuned K3LA
		k5h_030614_3.wav	here is the Canadian-tuned 5-chime K5H
		k5la_030614_2.wav	and the American-tuned 5-chime K5LA

construction

K horns, like P horns, have a single-piece bell/diaphragm housing unit. The back cap then bolts onto the back of this unit, and the entire piece bolts to a manifold. The bells are smaller than P horn bells, but have a wider throat and larger diaphragm housing. Also, the flare of the bell is basically an exponential flare starting early on in the bell's length. The only external marks on a K horn are the bell numbers, and a couple markings on the back cap. Sand-cast K horns have "AirChime" and "Made in Canada" cast into the back cap, whereas die-cast horns have "AirChime" and "30109" cast into the cap.

Inside, the K horns have a double-disk diaphragm separated by a silicone ring. This, a principle of a kettle drum, forms a sealed air chamber between the two diaphragms, and provides a more even vibration against the nozzle. It also virtually eliminates the typical drop in pitch as more air is applied to most horns, like the M horn. Also unlike the P horn, there is a diffuser ring used to more evenly distribute the incoming air stream around the inside chamber of the K horn. There are no rubber gaskets, either, and so the stainless diaphragm vibrates directly against a cast-in aluminum seat. Because of this, it is possible (though very uncommon) for a K horn to wear away to the point where machining will be necessary to restore the horn to proper spec before it can be used.

k5h_020627_1.jpg

a photo of my K5H showing arrangement on a standard high-profile manifold

designations

When Swanson first introduced the K series horns in 1954, he offered two different combinations. The first was the K3H, which uses bells 1, 2, and 3. This horn plays D#, F#, and A# - D# minor - in line with Canadian regulations. The K3H was offered on two different three-chime bases. One mounts all three horns in a horizontal line, next to each other. The second, like the early three-chime P base, mounts one horn in the middle, with on on each side, rotated 90 degrees. The second was the K5H, which uses bells 1, 2, 3, 4, and 5. This horn plays D# minor 6th (D#, F#, A#, C, D#) and is on a high-profile manifold. The manifold has three bells in a row on the "top", and two bells below, rotated 90 degrees.

Early AirChime literature shows some additional bells beyond bells 1-5, as well as alternate tuning for the 5 bell. Originally, the 5 bell played D, not D#. The other bells were 3L, 2L, and 1L bells, which played D# (155Hz), G# (208Hz), and C (261Hz) respectively. These bells help explain why the original K5 and K3 had an "H" postfix. Unlike horns produced after 1976, this is not because of a "high-profile manifold", since there was only one manifold style! Instead, the H represented "high-pitch". A straight K5 used bells 1L, 1, 2, 3, and 4 (C D# F# A# C), while a K5L (low tuning) used bells 2L, 1L, 1, 2, and 3 (G# C D# F# A# - G# major 7th), and a K5LL (extra low tuning) used bells 3L, 2L, 1L, 1, and 2 (D# G# C D# F# - G# major 7th second inversion). Also, the K3 used bells 1L, 1, and 2 (C D# F#), the K3L (extra low tuning) used bells 2L, 1L, and 1 (G# C D# - G# major), and the K3LL (extra low tuning) used bells 3L, 2L, and 1L (D# G# C - G# major second inversion). I'm not aware of any 3L, 2L, or 1L bells to have actually been produced during this timeframe, though. Supposedly, all these alternate models, along with the 5 bell tuned to D, were no longer available around the 1955-1956 timeframe.

In 1956, AirChime introduced the MK5H and MK3H, which use an M-like screw-on back cap so that the railroads that wanted to adjust their horns would be able to. These MK-style horns use a 1 1/2" socket to adjust the tension on the diaphragm, and have "Made in Canada" cast into the back cap. MK horns are extremely rare, and I know of only one of these, thankfully saved in a private collection. Just one year later, the MK design was dropped in favor of a newer design of adjustable back caps. These, on the K5H and K3H, use a 3/4" wrench to adjust diaphragm tension. These caps were made in both Canada and England, and so it's possible to have "Made in Canada" or "Made in England" cast into the back cap. Finally, in 1969, AirChime stopped offering the adjustable caps. Both of these two adjustable styles used a bolt-on ring which attaches to any standard K bell. The inside of the ring is threaded to accept the screw-on cap.

In 1976, AirChime unveiled the K5LA and low-profile manifold, though sales didn't start until 1977. The low-profile manifold is basically the same as a three-chime manifold, but with a port on the ends of the manifold for the remaining two bells, turned 90 degrees from the first three ports. With these product introductions, there are now three postfixes that can be applied to a K5 or K3. First, horns with the older, high-profile manifold have an H postfix (no longer stands for "high tuning"), whereas horns with the newer, low-profile manifold have an L postfix (no longer stands for "low tuning"). (A low-profile three-chime base was also introduced around this time.) Also, horns with the new, bored out 3 and 4 bells have an A postfix.

The 3A and 4A bells, as they became known as, were constructed by boring out the inside of the throat just enough to lower the pitch of the 3 bell one step, and the 4 bell a half step. Horns with these bells are said to be American-tuned, hence the A postfix. The K5LA uses bells 1, 2, 3A, 4A, and 5, tuned to D#, F#, G#, B, D# - B major 6th. The K3LA uses bells 1, 2, and 4A, and plays D#, F#, and B - B major triad. Also, though the K5LA, K5H, K3LA, and K3H are the common configurations, it is also possible to have A K5H, K5L, K3HA, and K3L.

Somewhere along the line, after 1956 and the discontinuation of the 3L, 2L, and 1L bells, a new 1L and 3L bell, and a 5H bell, were introduced. The new 1L bell blows a B below middle C (247Hz), the 3L bell blows A above middle C (440Hz), and the 5H supposedly blows high E (660Hz). The 5H bell is only used in Africa, though the 1L and 3L bells are used elsewhere. 1L bells are all sand cast, and of two-piece construction - the only K bell to ever be two-piece construction that I'm aware of. The diaphragm housing and foot are cast as one piece, and the bell is a second piece. The earliest 1L bells were cast by Hyson-AirChime, sold by Sydney, Smith, Dennis (now out of business) and were welded together. Newer 1L bells are bolted together, with a rubber gasket in-between. Horns with either the 1L or 3L bell will have at least one extra "L" beyond the manifold designation (either H or L). Some combinations are K5LLA, used on the LIRR (1L, 1, 2, 3A, 4A), K5LLLA (1L, 1, 2, 3L, 4A), and K5LAM (1, 2, 3L, 4A, 5). The M is not an official designation, since the horn is not a marketed product, but added to signify a "modified" configuration (the 3L bell in this case).

		bdrv8159_011218_3.wav	another clip of a K3H in service, sand cast
		k5h_030614_4.wav	another K5H, recorded at Steve Forrest's Oak Ridge 2003 blow
		ns_010704_3.wav	a K5LA passes through Three Bridges on an NS freight
		k5lam_hosford_1.wav	one of Jeff Hammaker's K5 combinations, a K5LAM, using bells 1, 2, 3L, 4A, and 5
		k5lm_hammaker_1.wav	Jeff's K5LM, using bells 1, 2, 3L, 4, 5
		k5lllm_020518_1.wav	Jeff's K5LLLM, using bells 1L, 1, 2, 3L, and 4
		k5_020518_2.wav	another of Jeff's creations, I believe this one uses bells 1L, 1, 2, 3A, and 4
		k5_020518_4.wav	one more - this sounds like it uses bells 1, 2, 3L, 4A, and 5, but sounds different from the K5LAM above...

last updated 02.17.2004