Why the K series over the P series?

I see most people using the K3L or K3H series of horns but not many using the P-Series. Other than the sound being a personal choice, is there another reason to use the K-Series over the P?

They are both priced within $100-$200 of each other and the P-Series is usually cheaper, and doesn’t use as much air so you would think there would be more people using them.

I should have enough funds in the next week or so to buy my horns and just trying to figure out the best set to get. I personally like the sound of the P-Series but if there are downsides to them I’d like to find this out before I spend the cash.

Nathan’s can take a bit more abuse (air pressure) than the Leslie’s.



The P-series I’m talking about are Nathan’s. (P3, P5) http://atsf.railfan.net/airhorns/p3.html

I’d say its a few things:

They are larger than the K-series. The P3 comes in a triangular formation with the longest bell on top. The P5 comes in a 3-high, 2-low high manifold much like the K5H. This takes a lot of vertical room. On top of that the bells are longer. (Where it gets the deeper tone from).

Then there’s loudness. The P3 and P5 are quite subdued compared to the K3/K5 (still waaay louder than any non-railway horn).

As well as losing a few decibels, the tone is far lower. The human ear tends to be less alert to lower tones (as well as extreme highs) so you’re a little less likely to grab people’s attention.

All that said, the P-series are extremely loud, will be heard from great distances, and will get everyone’s attention. They’re just not quite as compact or loud as the K-series.

But don’t forget to mention that P series horns have lasted 50+ years ON A TRAIN with no maintenance.

Tiernan, Thanks for the good explanation. The size of the horn isn’t that big of a deal for me since I’ll be using it on top of a boat tower. I’m primarily concerned with sound quality and durability (which Hondaguy make a good point about). I do like the deeper tone from the P-Series so I guess it will come down to what I can get for the best $$.

Thanks for the help everyone.

I actually like the sound of the P series better anyways lol. Not the new P5s but old cast P5s beat any K horn any day and same can be said about P3s (my opinion).

Good point.

A little history on that: the P-series was designed to be a maintenance free horn as a low-cost replacement for the old M horns to compete with Leslie. M-series horns required different replacements parts for each bell, whereas the P-series shared all the internals (much like the K-series). Also they do not require frequent recalibration like the M horns.

P horns by nature were designed to be cheap and low maintenance and they did this almost too well.

The K-series was introduced the year after the P and cost more. They were intended to become the favoured horn for locomotives (which now I’m pretty sure its safe to say they succeeded), but because of the success of the P-series they didn’t reach the immediate success AirChime expected.

The K-series feature a dual disc diaphragm system which is said to eliminate the pitch drop associated with single diaphragm horns. It was originally designed to emulate the sound of a steam whistle, raising the pitch as more pressure was applied, but never did.

The only difference between the K and P horn that may make the K horn more unreliable over a LONG TIME (cannot stress that enough lol) is the fact that the P horns diaphragms are always resting on some kind of gasket and are never touching the nozzle like the K horns.

So you’ve convinced me to go with the P over the K! Is there a big difference between the new and old castings? The new castings are more abundant but I’ve seen older styles for sale as well.

Older=better all around. Nathan changed the cast for the P horns and they lost most of their musical qualities. If you got the extra money, I’d go for old cast as they’ll only go up in price as time goes on. If you are just wanting it to scare, you’d be better off with a new cast as they are a little more “shrill”. New cast P3s still sound good but the new P5s are awful. I got rid of mine for the horn in my avatar lol

I prefer the sound of the P series as well! I just bought a new cast P3 and let me tell ya, it’s ear damaging loud! Heres a good video of both P and K series. The P3 is being blown at 115psi


115 psi? The tank and compressor I’m buying from HB doesn’t cut out until it reaches 150 psi… Is that too much?..

it was rumored that Swanson jokingly meant for the “P” to stand for “piss-poor”, as Swanson was never happy with the P horns, and he sold the manufacturing rights to Nathan Manufacturing.



LOL, the P actually stands for “pre-set pitch” :stuck_out_tongue:

I prefer the sound of the K’s over p’s, but that is just my preference.