Is it fair to say that larger embouchure holes require more air/breath, generate louder/breathier sound and are easier to target at (with the air jet) whereas the smaller ones are the opposite?
Any expert opinion/comment? Thanks.
No.
Could you elaborate a bit?
Here, what we really need in order to answer this question is a real expert (i.e. not me). But, from things I’ve gleaned from my own flutes, and from talking with real experts …
I have a flute with a patent head (its original head) and a spare Wilkes head. The original head has a very large embouchure hole, and the Wilkes head has quite a small embouchure hole. Both are quite hard to master, as it turns out. The Wilkes head is amazing (of course. 
) It takes loads of getting used to, and loads of breath … until that day when you finally get it. And then, it takes hardly any breath at all and produces a huge, booming sound, that would fill concert halls. The original head can produce a very wide variety of sounds and tones, as well as having a huge dynamic range, from extremely soft to very very loud. But it’s a nightmare to control. When you get it, it’s good, but the flexibility, which seems to come with a larger embouchure hole, also makes it hard to produce exactly the sound you want at any given time. But, again, when you’re used to it, not a lot of breath is required.
I think the size of bore makes much more difference to the breath requirement than the size of embouchure hole. The flute I’ve been talking about has a larger bore than my others. It takes more breath, even if you swap one of its two heads onto another flute - the other flute will take less, and I think that’s because of the narrower bore.
My conclusions, from the flutes I own, are that bore diameter makes much more difference than embouchure hole size and, in fact, that embouchure hole size seems to make little or no difference to how much breath is required or to how easy it is to blow. Shape makes more difference, IMO, and some of my heads are much easier to play than others. Although I have a few flutes in the house, and have drawn my own conclusions, I haven’t done a study or anything, so an expert may well be able to find flaws in what I say, or, in fact, be able to explain what I’ve found.
Thanks for your comment above. Maybe some others can shed more light on the issue.
I think it’s a bit easier to get lazy with a larger embouchure hole.You can get an acceptable sound with less precision than is necessary than with a smaller one, but that sound will not necessarily be even close to the full capabilities of the embouchure. (This is what I am discovering after playing for a week on my new Aebi, which has a relatively smaller embouchure, and going back to one of Steffen’s flutes. I can now get his [Steffen’s] flute to sounds like a foghorn once in a while). Of course, the cuts seem quite different also.
Yeah, that’s what I suspect. My guess is that smaller holes require more focused/precise embouchure. I sometimes lose the note/sound completely when jumping from a higher note, e.g. B, to the bottom note, i.e. D. As I am a beginner, I suspect that the reason is that I moved the flute slightly on the way, the higher notes seem to be more adaptable while the bottom one is very sensitive to embouchure precision. However, this is only my guess and the second post above disagrees.
I think the bottom D takes a lot of work in any case, whatever embouchure cut you have. It took me years to get anything close to what I want and, after 4 years, I’m not there yet with the bottom D. There’s a precise sound I’m after, and I’m not quite getting it. Well, sometimes, but not reliably. At least I can reliably get the note, and with reasonable strength these days.
Yeah, I’ve been trying to play the Glen Road to Carrick recently, and that last part will really show you where your embouchure is at. Mine is not at anywhere apparently… Can’t even make that d-D jump reliably, forget about putting a convincing cran on the bottom d…
So a larger embouchure hole won’t make the bottom D any easier to play?
Well, out of the two heads I mentioned earlier, the one which produces a far better, easier and honkier bottom D is the Wilkes head, which has a much smaller embouchure hole than the other. So my answer would be No. But some larger-holed heads will produce better bottom Ds than others. However, out of a very small sample of flutes that happen to be in my house (more than just 2 
) it’s the smaller embouchure holes that produce a decent bottom D more readily. I still think it’s the particular cut, the shape of the embouchure, that would make more difference than size. And also, it does take a long time to get that sound you want. Unless you get an accomplished fluter to try and s/he says there’s something wrong with your flute, then the answer is likely to be lots more work over a long period.
I don’t think we can just take embouchure properties apart from the whole flute.
I own a F.Baubet medium-holed Rudall. Its embouchure hole is quite large and I struggled with it for the first two or three weeks to get proper sound both on the bottom D and the high notes. The D was weak or dissapeared, the highs were tooshrill and out of tune. My bandmate has a Hamilton Pratten with bigger holes and bore but its embouchure, to my surprise, turned out to be significantly smaller. My impression from it is that that it is a bit easier to play - easier to control sound. Mine on the Baubet requires a bit of control on all the notes- it allows to produce sound of very different quality - it is not easy to find a “sweet spot” on it, to get even sound and to be consistently in tune. Hammy’s one seemed to me easier to play. But, I have to add, I AM used to my flute, the Hammy is a new different beast for me and I can’t yet get full proper sound out of it.
A while ago I had a chance to play an Aebi large-holed Rudall - it also had a smaller (than my Baubet’s) embouchure but a bit bigger than the Hammy’s (if i remember that right). It seemed to me easier to control as well.
But, the my main thought - we can’t take embouchure separately from the whole flute. Flutes of different makers feel different. My friend’s Hammy is very different from my Baubet. But it is different in embouchure, in holes, in octave balance, air requirement and so on. Moreover, the shape of embouchure doesn’t matter if you own only one flute and have nothing to compare it with. You just get used to it play it and its embouchure becomes yours.
Seems like everyone is telling you it’s not the case ~ me too 
Here’s Jed Wentz playing on a Pierre Naust copy of a baroque traverso. Embouchure size is approximately 7mm. He can fill a chamber hall although the microphone probably helps 
[video]http://www.youtube.com/watch?v=YXhRHf1rhZw[/video]
If you’re after a strident low D fundamental, it’s probably a combination of the flute design and large Pratten size holes. The Rudall Carte 1867 patent Boehm style flute and the Rockstro design (with the innovative F sharp key) has massive fingering key pads which dwarf normal size Boehm flutes. It is really strident at the loud low end notes. I guess the rectangular embouchures are also aided by deeper chimneys (convex designs) to project the air through.
If you’re more of an average Joe with a normal simple system unnamed keyed flute, making it completely airtight by redoing all the tenon threads; sealing the headjoint cork and rebedding all the pads will probably help that extra decibel to get the most out of the low end, next to practicing more…either of these are better than spending lots on a miracle foghorn peashooter