In his latest article in the Harmonica Microphone series, Greg explains what happens when your cup overfloweth. The secret is getting a good seal.
Good amplified tone starts with the player’s tone, and is accentuated by microphone technique. Cupping is an art; a learned skill that is neither obvious nor easy in practice. Properly done at its extreme, no air you suck or blow can escape “the seal” and therefore no sound at all comes out of the harp. Your goal is to visualize that all your breath must enter and exit through the microphone itself. In reality it is very hard to do this, and it is hard to even come close at first.
When the seal with a microphone is very good, the air pressure changes are effectively “coupled” to the microphone’s diaphragm in a way that is very, very different from the normal “free air” mode in which mics were designed to operate. The result is a very distorted signal sent to the amp.Note that to accomplish such a seal, you must not only create an airtight seal between the rear of your harp and the microphone, you must also seal off the open holes on the front of the harp – otherwise the air you blow/suck is free to travel under the coverplates, through all the open reeds and out/in the other open holes on the harp. This reduces the “coupling” effect you’re shooting for. You can learn the technique acoustically before ever attempting it amplified.
First, listen to the technique applied acoustically:
And now, the same technique amplified:
However to choose a good harp mic, you must understand what cupping is, as different microphones will respond in dramatically different ways to the technique.
Why are some mics more responsive to cupping?
Factor 1: Mic shape and size. When a mic’s physical shape or size makes it hard to achieve a good seal, the effect of cupping will be less.
Factor 2: Headroom. When a mic has a lot of “headroom”, which is the amount of sound pressure it can handle before it distorts, it will obviously distort less. A perfect example of this is the Audix Fireball, which has something like 140dB of headroom. A brilliant feat of engineering, but it makes almost no difference to your tone whether it is cupped or not.
So how does microphone shape make a difference?
There are literally hundreds, if not thousands of different kinds of microphones to choose from. Mics vary in cost, size, purpose, tone, and shape – all of which affect us. For amplified tone, one of the most important variables is the mic’s shape.
There is little about the shape that affects the mic’s tone in free air. However everything about its shape affects your ability to cup it easily and effectively. People’s hands and muscles differ, so one size most definitely does not fit all.
A stick mic with a ball end like the SM58 can also be difficult for smaller hands. The smallest diameter stick mics, like Shure’s SM57, are easy for some to cup, yet cause hand cramps for others. And their length gives the weight of the cable leverage to pull down on the end of the mic – another fatigue factor. (The weight and length of Shure stick mics was one of problems I set out to solve when I developed the Ultimate Series Microphones.)
The largest diameter bullet in popular use is the current model of Shure’s Green Bullet, called the 520DX. It is hard for people to cup well unless they have fairly large hands. It is also one of the heaviest mics available – and when you perform a three- or four-hour show, hand fatigue is a factor worthy of your consideration.
Finally, some mics like the popular JT30 or Hohner Blues Blaster have bumps around the circumference that make tight cupping very uncomfortable. Among vintage bullet mics, there are many shells that are a little smaller. The Electro-Voice 630 and M23/43, the Astatic T3, the Shure 707 are all excellent shell choices and are popular among “do it yourselfers” as mic project starting points.
Another variable is where the mic’s shell places the element relative your harp. Some shapes will hold the element further forward, others further back. Further forward reduces the size of the air cavity between harp and element, reducing the tonal changes from cupping. This effect is slight but real.
In summary, a mic’s shape makes a real difference! You’ll have to experiment to find what works best for you.
Watch out for Greg’s next post, with everything you need to know about microphone elements.