Here are a couple of recordings from today. I recently purchased a Graham-White valve. I bored and decided to record (Ha! That rhymes!)
Anyways! Forgive the odd sequence, the valve is a little hard to work.
First up is my 90's K-5LA with the 2 and 4A bells reversed. The 5 bell is standard bore and the whole horn is bare aluminum glass bead finish. I do not know what the heritage of the horn is. It had black paint on it when I got it, but It was not original.
Second, my 1981 RS-5TRRO. The 44 and 55 bells are reversed. The horn is of L&N/Seaboard heritage. It wears a worn coat of CSX YN1.
Notes: I used a 12 gallon surge tank with 1/2" I.D. plumbing to achieve good volume. Starting pressure was 120 PSI and was 90 when it was all said and done with for each horn. Reversed bells faced the garage with bounced the sound around enough to balance it out.