It isn't that metric sized drums are uniformly 10% bigger. You need to know what the actual diameter of each drum is. If they are all true metric then they will be even size in the metric system, and thus not an even inch size in the US/Imperial system. From memory, there were some metric Premier sets where only some drums in the set needed metric heads, and other drums were actually close enough to use heads in even numbers of inches. In some cases the metric shells just act like slightly undersized shells. You still have to watch out for the rims though because that presents another stumbling block to head happiness. As an example (from my ruler Burger Kin) a 350mm drum would be 13.8 inches. Easy to get a standard 14" head to fit it. Not easy to get the metric rim it came with to cooperate. So you would also need to substitute a true 14" rim. Then you have to rely on the lugs and tension bolts being able to handle that amount of outward splay. Obviously this isn't the case if the manufacturers chose the metric equivalent of 14" to be 360mm. Then the shells will indeed be too big in diameter. Thus my comment that you really need to know the exact sizes of the drums. Similarly 400 mm is a slightly undersized 16" shell. 15 and 3/4" with rounding. Same situation as the 14" head. But if they chose 410mm then no dice. And 330 mm is 12.99 inches so you can probably get away with the 13 inch head and the metric rim unchanged. That would be a reason for Remo to not offer a metric version of a 13 inch head. It isn't needed. I don't know why they wouldn't offer a metric equivalent of a 14" head, but it may actually be that the rims on the metric equivalent of 14" can handle the difference in almost all cases.So if you have managed to wade through all these numbers and not have your eyes glaze over, the answer is: begin by getting the exact diameters of the drums and work from there. If you do need to order metric heads or just special sizes from Remo you must know exactly what you are dealing with before you order. Special order = no return. :2Cents:
pretty much agree with all of this but perhaps i could add some rules about this , where they exist. i have been making and fitting heads since 1966---skins of all kinds and plastic too.
Rule# 1: Remo wrote the book of Rules; there were very few standards until the first Remo heads flooded the market. All of a sudden, in order to conform to the " standard" it became necessary to have shells sized in inch increments. Remo has always indulged users of any sized drum and will make a head or many heads for you . Obviously, one head is expensive and 100 heads relatively less per unit. Many companies, over the years have had Remo do custom runs----for instance, Trixon,in the early 60's could supply all of their drums with production Remo heads, despite the fact that none of their drums at the time matched the standard inch sizes being manufactured for mass distribution by Remo. Over time, as the demand for various odd sized heads decreased, they were dropped from production. I could be wrong on this but currently , the only off sized heads that Remo stocks as production heads are those for the pre-mid-sixties Premier/Olympic/Beverley drums. They are all prefaced by a PR and the 12" actually is designed to fit the 11 7/8" of the old Premier rack toms.
Rule#2: So-called metric heads are not necessarily metric; Is an 11 7/8" drum metric? Well, at 29.9 mm I guess it is but being an English drum maybe it should be measured in chains instead?--that would be pretty close to 1/66.67 chains or 1 of 2/3 of a hundred chains. That's a pretty round figure---no?
Rule#3: Until 1955 were no rules about heads;They were skin; they could be made any size within reason that you wanted. American drum companies made various inch and fractional inch sized drums and English drum companies made various inch and fractional inch size drums and European companies made various metric sized heads until Remo came along.Then Rule#1 took over. The Japanese just copied everybody else and if it worked and sold they stuck with it as long as yankee dollars poured in.Ditto, for Taiwan,Ditto for Korea and well China---they are a whole other kettle of monkey brains.
Rule#4: Most Continental drums were sized, specific to the company until Remo came along(see rule#1); The only standard that could be called such came from Dresdner, which produced legendary snare drums at 360mm. This size was also used by Trixon, Trowa, Lefima(and others for sure). Why 360mm? It's a magic size , of course. It's very similar to 14",which is also magic. It confers a certain je ne sais quoi to a drum, transforming the dull, plodding and dead nature of a 350mm drum or a 13 5/8" drum for that matter into the realm of the choir invisible. ----I don't know!; presumably, the formulation of the European Beech or Nickelled Brass , along with the hardware , snare construction and heads took flight at 360mm and other companies fell into line. Trixon dropped it in 1963, Trowa before and Dresdner Apparatebau still uses it to this day. Other metric sizes? There are myriads and there isn't a lot of company overlap. Heads for pre-1959 Sonors will mostly have to be custom lapped or custom made by Remo or one of the German makers that does them. They come out as really odd inch sizes.So, nothing except the above noted exception was standardized until they all started to march with Remo. Some examples of sizes from just 3 German companies.
23.3 24,26,28,31,32,33,34,36,36.3,38,41.8,42.6,50,54.6,55,56.---cm.
Rule#5: Most of the older drums work better with calf heads and carbon steel wires; Part of this is their sonic nature and part of it is that plastic heads put more stress on the shell than calf.Some of the thin shelled drums, actually require less regular tuning with calf heads. Calf ,comes to tension with less pull on the lugs than mylar and they don't stretch. They will slacken and tighten with the humidity but plastic heads can yank(no pun intended) the shell, slightly out of round and require increasing tension to bring an otherwise soft sounding drum up to a crisp tone. It is probably quite surprising for most of you to hear that a calf head can be surprisingly bright and crisp with less tension than an Ambassador for instance. That is why so many of the old drums had very thin shells. With the mylar heads in vogue , the shells had to become thick ,in order to take the stress. When in doubt,if you can find a fitting plastic head; start with thin ones---Diplomat or equivalent.
As for the original question about Aquarian vintage heads. The rational for these seems obvious. Many older drums, irregardless of their country of origin were a little imprecise in their manufacture and also a lot have become oval over the years(this is especially true of some solid shells and those fitted with straight flat rims(stickchoppers). The wooden hooped skins that were supplied were often also more loosely fitting,with more dropdown.. The Aquarian heads are slightly oversized , in order to accomodate these irregularities but they are not big enough to accomodate the Premier 16 1/2" floor toms, or Trixon 14 3/16" snare or Sonor 12 1/2" snares for instance.They are big to overcome irregularities and to allow the drum to give. As Zenstat said----measuring the shells is really important and one last tip. Don't rely on Remo to do the measuring for you when ordering custom heads. You would think, that it is easy for them but it really isn't . They either need the shell and the rim to use as a template or precise measurements from you. The most important of those being the i.d. of the aluminum head-hoop.
