It’s been a while, folks, but at last we continue the Harmonica Microphones series with the second part of Greg Heumann’s exposition on microphone elements.
Last time around, we described two kinds of elements used for amplified blues harp – dynamic and crystal elements. So let’s name some of the most sought-after crystal and dynamic elements, and find out how to shop around for them.
Which are the most desirable Dynamic elements?
The most desirable dynamic elements among amplified players are the vintage Shure “Controlled Magnetic” and “Controlled Reluctance” elements (“CM” and “CR”). Yes, CR’s and CM’s are dynamic elements – but because they are special ones we usually refer to them by their marketing names instead of just lumping them in with all the other “plain old” dynamic elements. These elements came in the Shure 520 and 520D microphones, among others. The current 520DX has a more modern dynamic element which is less desirable tone-wise. It is brighter and has less bottom end.
Much has been written about Shure’s Bullet elements; Dave Kott’s excellent site has more information than you’ll ever need so I won’t repeat it here. Suffice it to say that these are great elements, and because of their “magnet and coil” construction, they have tended to last much better than crystals. Many players are still using the dynamic elements from vintage Electro-Voice microphones as well.
Dynamic elements are the most common among modern microphones as well. They are used in the majority of mics marketed to amplified harp players (Shure 520DX, Peavey Cherry Bomb, Bushman Torpedo, etc.) as well as the most popular instrument and vocal mics like the Shure SM57 and SM58. There is a huge range of dynamic elements. The newer they are, the more likely they are to appeal to acoustic players and the less they will to amplified players. This is because they have extended high frequency response which can be harsh and they don’t tend to “break up” as easily, making it harder to induce distortion at the amp. However there are exceptions. The Shure SM57, for example, actually breaks up very nicely and makes an excellent harp mic.
Which are the most desirable Crystal elements?
The most desirable crystal elements craved by harp players are the Brush Crystal, the Shure 99-131 aka “R7” element that came in the Shure 707, and the Astatic MC-151 element that came in the JT30. The Brush and Shure elements are all but extinct. The MC-151 element was made for a much longer period of time, but has still been out of production for many years. They are available (I still collect them for my customers) but their prices are going through the roof.
Over time, any crystal absorbs moisture and softens until it literally falls apart. If you buy an “untested” crystal on eBay, it is practically guaranteed not to work. Often, if you shake them they rattle. This is what is left of the crystal bouncing around inside the element. Along the way, they become more and more susceptible to damage from drops, temperature extremes, or even very aggressive playing (I once ruined a crystal, which undoubtedly was getting ready to go anyway, by drawing really hard with a tight cup. The vacuum pulled too hard on the diaphragm, and broke the connection to the crystal).
How do I get one?
Ah the million dollar question. If you like to gamble, you buy them on eBay. If you don’t, buy them only from a reputable dealer who knows harp and knows elements. eBay is filled with deception and ignorance. If you see a crystal element available (usually in a mic shell) with a description that says “I have no way to test it” you can assume it is dead. Of course this isn’t always the case, but it is generally true. Crystals don’t always fail all the way at once. Their output can simply get lower and lower. So even one that “works” may not work well at all. The only way to know is to try an element by hooking it to an amp. And the only way to know then whether it is in truly great shape is to know how loud they’re supposed to be. I buy crystal elements to provide to my customers. I charge a high price for them. Why? Because I’ve had to eat the cost of a lot of lousy elements I will not resell. If you buy from me, you get a good element, or your money back!
You’ll often see eBay vendors showing you the resistance measured across an element. However, you should never hook an ohm meter to a crystal – you can damage the crystal this way. But across a dynamic element, the fact the resistance is neither zero ohms (a short) or infinite (open) tells you that the coil in the element is still working. The value will also tell you something about the element’s impedance. 50-100 ohms indicates a low impedance element, somewhere around 1000 ohms indicates a high impedance element, and somewhere in between can indicate a medium impedance element. These are rare, but should be avoided as it is difficult to find a proper impedance-matching transformer for them.
The ohm meter’s reading, however, will not tell you anything about the tone of a particular element. Do not believe that 1.1K ohms is better than 1.2K ohms, or vice versa – it simply isn’t true. It is also not proof that the element is good. An element that’s corroded or squashed may not work or will work poorly, even if the coil is OK.
If all this talk of impedance leaves you just a little bit in the dark, don’t worry. I’ll explain more in our next article.