I recorded a couple of quick clips of me playing both the Freeman Tweaked Generation D and the Killarney Brass D whistles. Both videos were done on an iPhone, so the whistles will obviously sound better in person. This does show a pretty good comparison of the timbre/tone of the two whistles though. I’m posting this since I would’ve loved to see something like this before I purchased my Killarney.
The Generation takes a bit more air and a bit more push in the second octave. It has a slightly more airy (chiffy even?), open tone. The Killarney is heavier (obviously from the metal headpiece) and sweeter. The first time I played the Killarney I thought it was quieter than the Generation. Honestly though, after a lot of playing time on both whistles I think the volume is pretty similar between the two. The Generation may be slightly louder in the 2nd octave because of the extra push it requires, but it’s not a huge difference. There’s just something about the Killarney that sounds softer (for lack of a better term). I feel like the Killarney is a bit easier to play because of the reduced breath requirements. Both are great sounding whistles and I’m glad I have both so I can experiment with them on different tunes.
NOTE: I have only been playing 3-4 months and am VERY much a beginner. Both these whistles would sound better in the hands of a more accomplished player.
https://www.youtube.com/watch?v=o3g5vK-mQ2A
Thanks for the post and the description. I also have an all brass Killarney. The Killarney, with my Freeman Blackbird D and the Mellow Dog makes a powerful triumvirate. I don’t see Jerry’s tweaked Generation D on his Ebay listing any more. Maybe, he will bring it back.
I love my Killarney, but sometimes I switch to my Dixon Trad because I need more breaths. The Killarney has almost-too-low air requirements.
Oooh… that would be a good thing for me, thanks!
I just now came indoors from our morning break at school. (I am a teacher) I was playing the Dixon Trad D nickel! Ok, back to my teaching now. … 
Brass Killarney sounds very close to my Tweaked Dixon brass Trad (not as breathy as a stock Trad D). Killarney does sound softer to my ears than the Gen Brass redtop. I like both!
I have three Killarney whistles, a D and Eb in Nickel and a D in brass. I’ve tried many makes of whistle over the years. The Killarney whistles are, for me, the best I’ve ever played. And I’m including Copelands, Sindts, Overtons, Reyburns*, and all the usual Generation type whistles as well.
\
- For me, my Reyburn C/D set would be my second favourite whistles. Very loud, though. I have the ‘session’ set.
You may have only been playing for a few months but your observations are exactly in line with my feelings, based on 40 years of playing.
IMHO what the Killarney and Sindt do is to replicate, better than any other modern whistles, the way some really good vintage whistles (Generations, Feadogs, etc) play.
An extremely light easy sweet 2nd octave, yet a full round low octave, and nice tone.
Jerry’s tweaking (in my admittedly limited experience with them, around a dozen) takes the Generation in the opposite direction, more the direction of most modern makers, which is to maximize fullness in the low octave and creating a slightly stiff 2nd octave.
Not all Freemans I’ve had, mind you! I have one Freeman Generation Bb head that’s wonderful. It has that old-school sweet 2nd octave. I use it on a Freeman Generation Bb body and a self-made A body and it’s great with either. But I have two other Freeman Generation Bb heads, and two or three D heads, that play as you describe.