What's the difference between 3Hz and 4Hz movements?

4Hz is 28,800 beats per hour and 3Hz is 21,600.The seconds hand on a 4Hz usually looks smoother because it ticks eight times per second vs six. Accuracy isn't guaranteed by frequency alone but higher beat rate can help against position variations.

I have both. Honestly on a skeleton the visual difference is more ogvious than I expected. The 4Hz balance looks busier and the escape wheel moves faster. Whether that's better is personal.

Maintenance is the thing I'd care about. Higher beat rate means more wear over time on the pallet forks and escape wheel. Not a dealbreaker but worth knowing if you're buying older skeleton pieces.

3Hz can be nice because you see the escapement action more clearly. On some 4Hz skeletons it almost blurs. Depends on the design and how open the dial is.

Is 3Hz generally cheaper to service? I've heard some watchmakers say lower beat movements are a bit more forgiving.

Not necessarily cheaper, but fewer beats per hour does mean less cumulative friction. The bigger factor is parts availability and how the movement is constructed. A well-made 3Hz can outlast a poorly finished 4Hz.

I don't think most people notice the difference on the wrist. The skeleton factor makes people look closer though.

There's also the sound. Some 4Hz movements have a faster, higher-pitched tick. If that bothers you, 3Hz can feel calmer. I know that sounds odd but it's real when the case is thin

That's a good point about sound. I hadn't considered it but my 4Hz skeleton is definitely more aUdible at night than my 3Hz one.

If accuracy is the priority, 4Hz has a theoretical edge in stability, but regulation and build quality matter more. I wouldn't pick a watch based on frequency alone.

Agreed. Also some 3Hz movements are surprisingly accurate. My old 3Hz skeleton runs within a few seconds a day and it's not even adjusted

For a skeleton I'd lean toward 3Hz just because the slower motion makes the mechanics easier to follow. But that's purely aesthetic. Functionally both are fine.