What is that blanket inside your kick drum actually doing? Shouldn't it be keeping you warm at night?
Sometimes we take things that are commonly done to be the way things ought to be done. It doesn't take more than a few minutes to think of stacks of examples. One example in music is putting a blanket inside a kick drum. Everyone does it. But why? What function does it actually perform?
The best place to look for the answer is in the kick drum itself, without the blanket. Hit the pedal and see what the drum sounds like - it will be a long 'boom' that takes a good while to die away - perhaps up to a second or more.
Now if the drum is played more often than once a second, there will be no let up in the sound. Try it for yourself - it doesn't sound too good. How kick drums ever evolved this way is a bit of a mystery, or perhaps people were putting blankets in them even as far back as the 1920s.
The reason why the sound extends for such a long duration is that the drum is resonant. It takes the energy input from the actual kick and channels it into a vibration centered around a particular frequency. Then it releases this energy over a period of time.
What we need to do is make the drum less resonant, so that the sound will be more of a thud and less of a note, and in doing this also make the sound shorter.
You may have heard of the terminology 'batter head' and 'resonant head' in relation to drums. The batter head is the head that is struck. The resonant head... yes it resonates. Since resonance is precisely what we want less of, wouldn't it be a good idea simply to take off the resonant head and throw it away?
Yes indeed, this is a very good start. Drummers tend not to like to do this as it makes the kick drum look somewhat 'unfinished'. But if it doesn't sound good with the resonant head, then why have it? And a drummer who is serious about recording really ought to keep a kick drum especially for that purpose.
The next step is to put a blanket inside the drum. The purpose of the blanket is not only to absorb energy, but make the three remaining components of the drum less resonant. We describe this as 'damping'.
The three remaining components of the drum are (did you guess?) the batter head, the shell... and the air inside. The blanket will inevitably be in contact with the shell and the air, and it can rest against the head if you want.
At this point, adjustment of the blanket is all down to the nature of the sound you want to hear. If by chance you did put the resonant head back on, you will have less opportunity to adjust the blanket. (And since the drum is now more resonant, you should have put a bigger one in!)
You don't have to use a blanket. You can use a proprietary kick drum damping system. It will cost a lot more and not work any better.
I have to wonder though whether anyone is thinking up a new kick drum design that incorporates its own damping. It would seem to make sense.