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Nathan/Airchime K5 series - K5L, K5H, K5LA, K5HA, K5HL, K5LLA



K5L and K5H: D# minor sixth (D#, F#, A#, C, D#), with K-series bells #1, #2, #3, #4, #5
K5LA and K5HA: B major sixth (D#, F#, G#, B, D#), with K-series bells #1, #2, #3a, #4a, #5
K5LLA: discord (C, D#, F#, A, B), with K-series bells #1L, #1, #2, #3L, #4
K5HL: D# minor sixth (C, D#, F#, A#, C), with K-series bells #1L, #1, #2, #3, #4


K-series horns are reliable and stay in tune fairly well over many years. They produce a clean, clear sound when in good condition. Around the same time the K5LA was introduced (late 1970's) die-cast bells replaced earlier sand-cast ones. Unlike the P-series, tuning remained correct with the new bells, but the old ones had a slightly mellower sound. Canadian-tuned versions are haunting—the K5H has a pleasing "unresolved" sound--while the K5LA is melodious. The K5LA has gained a reputation as an extremely loud horn (one reason for the development of the K5LLA and K5HL). K5 variations are also known for producing a "warbling" sound--this is caused by slight differences in the pitch of the #1 and #5 bells which are supposed to be an octave apart. Horns without an octave combination such as this do not warble.

Some less melodious sounds have been produced by K5 horns in recent years. Recent K5H/K5L horns were produced with the #4a bell instead of the #4 bell, resulting in a discord (D#, F#, A#, B, D#). Manufacturing inconsistencies have also resulted in a wide variety of chords from the new K5HL and K5LLA. The K5HL often sounds the chord B, D#, F#, A#, B, a sound similar to the K5H/K5L with the mismatched #4a bell. The K5LLA often produces chords (or discords) that don't match the intended tuning, although one of the results I've heard (B, D#, F#, G#, A#) is a very interesting sound.



K-series horns have similar gracefully shaped bells to the P-series, but the bell throats are wider. Two manifold types exist for the K5 series. A high-profile manifold features three bells above with two underneath; this arrangement was used almost exclusively with the Canadian-tuned version (K5H). Very few American-tuned versions were mounted on the high manifold (K5HA). The low-profile manifold has three bells in a row on top of the manifold with the smallest ones on the sides, forming an arc. All bells share the same back cap and power chamber size.


K5LR24, K5LAR24

Classification and Use


It is generally accepted that "L" and "H" currently designate a low-profile or high-profile manifold. However, when the K5H was first introduced, the "H" was intended to mean "high-pitched", since none of the low-pitched bells manufactured at the time (1L, 2L, 3L) were used on the horn.

As with other Nathan/Airchime horns, "R" is added for bells that are reversed, as in the K5LAR24 or K5LAR34. The "A" refers to American tuning, to distinguish from the earlier Canadian-tuned versions. An extra "L" in the K5LLA and K5HL is for "Low-pitched", as both horns feature the #1L bell tuned to middle C.


The K5H/K5L was introduced in 1954 and was tuned to comply with Canadian regulations for a D# minor chord. It wasn't until 1975, more than twenty years after the initial introduction of the K-series, that a major-key tuning variation was introduced. At the request of Amtrak, the K5LA was developed with the #3 and #4 bells lowered from A# to G# and C to B respectively. The bells were mounted on a new low-profile manifold, resulting in the K5LA designation. This horn has proved to be extremely popular, to the point where after the year 2000 it was the most widespread locomotive horn in North America.

As of 2005, FRA regulations specified a maximum (as well as minimum) decibel output from horns, resulting in the development of the supposedly quieter K5LLA and K5HL.


While not common in the United States, the Canadian-tuned K3H/K3L and K5H/K5L are the standard horn in Canada, with the K5H used mainly by BC Rail. The K5LA can be heard just about anywhere. It's the standard horn for commuter and passenger lines and has replaced the P5 on newer locomotives on the Illinois Central and Norfolk Southern.

It remains to be seen whether any locomotives produced after 2005 will have these older K-series horns, as recent locomotives have been built with the K5LLA (EMD) and K5HL (GE).

Copyright Michael Eby - Page code last updated 2010-07-18