Y cables and phantom power

Most have very low draw and would be fine. Some are close to spec and power would sag.

just gonna give it a shot and see if it works.  if not, no loss aside from the 5 min it takes me to make a Y cable.  if I'm back to using two separate pres for each tom, so be it.  just excited by the possibility of using fewer pres/inputs.  saw a thing about Brendan O'Brien doing this with a 421/57 on toms.

in the genres I typically work in (metal, hardcore, punk), fewer mics on kits doesn't yield the hyper-real sounds people tend to expect.  I currently use no less than 15 mics on a kit most of the time.  

When I was in nuclear power, propositions like this where labeled “Gross Conceptual Error”. You cannot simply Y or MULT mic outputs together. Think about it. If it was possible wouldn’t it have been in common practice for decades?

First, the phantom current draw from the preamp would double, dropping the phantom voltage delivered to the mics and robbing power. Obviously a bad situation.

Second the low impedance mic outputs would effectively short each other. This won’t be healthy for its output stage. If you get any signal at all it would be heavily distorted.

I don’t know what you saw in that video but there must be more going on than is apparent. Something like summing build-out resistors inside the XLR connectors. That might work with passive mics.

It's not that simple.  Mics are typically class AB and rarely require full phantom current.  Most, if not all, have bulk capacitance internally that is rarely depleted so instantaneous current steps wouldn't be an issue for most.  Both mic outputs would normally be in-phase and would lessen the amount of nulling, and would likely be working in compliment.  Either way, most mics have some form of current limiting in the form of resistors.  Output impedance in the few-hundred-ohms range isn't going to burn anything up even with dead shorts.

I've Y'd mics together a lot over the years.  I'm not a big fan of it anymore but it never became a problem doing it.  If a mic has an issue, it'll sound bad and you won't use it like that anyway.

Might want to wire up a short polarity flip cable if you’re gonna go top and bottom into one pre.

+1 I've been reading about a Y-cable with one polarity flipped for snare top/bottom for decades. It's not new. And it’s a snare drum!

Condensers? Not wildly different from the 'Straus Packet' (Volker Straus) approach in terms of power viability.

en.wikipedia.org/wiki/Volker_Straus

Done to create wide cardioid when no suitable mic was available. 

I don't know how Brendan O'Brien does it, but I know some prominent engineer/producers have custom boxes for that, with 2 female and one male XLR per channel, polarity switches and attenuators for blending. Personally, I wouldn't want to do it without the attenuators. I think the phantom power still comes from the mic pre in this scenario...

Well said. Especially if they’re playing blast beats - those seem to turn most drummers into tappers. We need all the help we can get

....and it comes around to.....the drummer.....

I've had session guys go over schedule and have to leave, replace them with another guy on the same kit, sounds nothing alike and they are the only part that's changed.

Oh and there's two types of drummers out there. The kind that tune the heads to the breaking point and the kind that barely finger-tight the tension rods.

Knowing how to tune a head to the shell is a huge step to sounding good.

I mean, sure, it works for anything if you want that minimally mic'd sound.  I've used Glyn Johns (modified or just the straight up 3 mic original) many times.  It works if you want that sonic aesthetic, it doesn't work if you don't.  I have yet to hear a metal/punk/hardcore record that's going for that kind of aesthetic.