You can get away with an even smaller diameter. You want to check the "free air resonance" point, as close to 20 Hz. as possible. A butyl rubber surround is more durable under heavy excursion movements.
PartsExpress used to have a nice Pioneer 12" woofer with a "FA" point of like 18 Hz. This makes a good candidate. In fact, PartsExpress has a lot of nice woofs that will work in that capacity. Check 'em out.

hey moon dude... what's up bro... quick question on this... dont ya think efficiency is gonna be an issue???

And...related to efficiency...I think.. :shock:

Keep in mind this is capturing sound from a walloped kick drum, not reproducing it by electrical means with high power.

It may depend on several things how well something will work.

How big is the kick drum, and how hard does your guy kick it?

How far away is the speaker going to be?

A large, looser speaker with a lot of excursion may not react quickly enough to get a good, tight beater sound, and may still be moving slightly between beats which may contribute to more low-end mushiness or woofiness. The cone may vibrate too long? If so, it's probably still sending that to the recording, causing possible rumbling.

A tighter speaker may pick up the transient well, but may be lacking in the low-end reproducabilty.

If a 1" diameter microphone element can pick up good, low sound, it stands to reason that a speaker should be able to. It's more in how that speaker reacts initially, and immediately after. And, it's in the sound you actually want.

Of course, all of this can be tweaked somewhat by running through a preamp (which you'll almost certainly need) and EQ. If it's there in the first place, you can always tweak it out. If it AIN'T there, it's hard to put back in.

...I think I got that somewhat correct...

Kapt.Krunch

You have to ask yourself this:"why do I want to use a speaker as a kick mic in the first place?" It isn't to get the full range of the instrument-it is to get that LOW END. This was the case when they did it in the 70s for Stevie Wonders' "Songs in the Key of Life". It is the case these days when people grab the Yamaha SubKick. I used an 8" Peerless hi-fi woofer to do that several years ago. When I changed the surround from paper to rubber, and doped the cone to make it stiffer, it went from sounding like a cardboard box to a good deep punch. This was because the speaker's FA point was much closer to the tuning of the kick drum, so the resultant output was much higher. As far as getting the upper range of the drums' tone, I still relied on a 421, sometimes on the beater side, sometimes in the drum. I positioned the speaker, which I suspended in a frame kind of like a gong would be mounted, but with 4 tension springs to stabilize it.
I mounted a polarity switch and a little line-matching box a local tech here rigged for me. It rocked pretty well until my place was visited by Hurricane Ira a couple of years ago. RIP, Boomer.

Although it will lower the output (should'nt be a problem) the other way of controlling the resonance (i.e. "boominess") is to load the speaker with a few ohms (or less) of resistance. This is pretty much how the speaker is used the other way and compares with damping factor.

[EDIT] Not only is this much easier to try than changing cone suspensions and doping but it should not affect the higher frequencies in the same way. I'm not saying that the overall effect will be identical but it should certainly help with the OP's question.

thanks for all the tips guys! Appreciate it heaps.

cheers,

Sammyg