Everything you could ever want to know about the Shure Green Bullet mic and more!

                                THE ELEMENTS
                                        SHURE CR & CM ELEMENTS

                                   The Physical Characteristics of the Elements
          Shure introduced the Controlled Reluctance Transducer element in 1949. The elements had a unique design that made them immune to temperature and climate conditions. It consisted of a brass disc that was used as the main support for the built in transformer, magnetic assembly, diaphram, armature assembly and cover. It was described by Shure as being a high output microphone with good response, high impedance without the need of a transformer that had its stability assured by unique control of the reluctance of the magnetic system. Years later they were called Controlled Magnetic Transducers. Shure described them as being pressure operated units using the balanced armature, controlled magnetic principle.
            The elements have a built in transformer, eliminating the need for an external one. The early CR's (controlled reluctance) were made with a transformer bobbin that was made of phenolic material that could withstand a lot of heat. This bobbin is also the main support for the elements copper lead wires. Being able to withstand a lot of heat made it much easier for most people to solder lead wires to the element without damaging the bobbin. In 1954 Shure switched to a plastic bobbin which remained the type used until the elements were discontinued in the early 90's. This plastic bobbin would melt if the microphones lead wires being soldered to the element were not soldered onto the element quickly, causing the elements main lead wires to become loose, or possibly unattached completely from the bobbin. Obviously the phenolic bobbins were superior in quality, and I can only imagine that Shure was looking save some money by switching to the plastic bobbins. The bobbin also held spacers in place to keep the winding from moving excessively. The new bobbins had molded in spacers. 
            All the vintage elements have a metal foil diaphram, and a magnetic assembly that consists of two L shaped pieces of metal to hold the permanent magnet in place. The magnetic armature is an E shaped piece of metal that has a metal pin attached to the center part of the armature. This pin is glued to the center of the diaphram and transmits vibrations from the diaphram to the armature. The armature assembly is held in place by two screws, and part of the assembly that holds the magnet in place. The center piece of the E shaped armature runs through the middle of the wire winding (transformer) and is centered precisely in a gap near the magnet. This part of the armature has the pin that is glued to the diaphram attached to it. This pin transmits the mechanical vibrations from the diaphram through the center of the winding via the armature which turns the mechanical vibrations into an electrical signal which is produced by the transformer winding and controlled by the magnetic field created by the permanent magnet. The electrical signal is then sent down the microphone cable to the amplifier

How They Work
              The element produces sound by taking the mechanical vibrations created on the foil diaphram when you speak into the mic, or put the mic in front of any source of sound, which turns the vibrations into electrical impulses that are picked up by the magnetic armature via the pin glued to the diaphram, and the magnetic armature as described previously. The number of turns of wire, and the thickness of the wire wound on the bobbin determine the amount of resistance it creates, otherwise known as the elements impedance. Well, not really. The impedance of a mic is determined by a formula, but as far as this website goes, we will refer to impedance as the actual DC resistance of the element because this is what most people think impedance is. The wire winding and the magnetic field created by the magnet turn the vibrations from the diaphram into electrical impulses that are then sent to an amplifier via the mic cable. The amplifier then takes the electrical impulses created by the microphone and turns them back into mechanical vibrations, which vibrate the cone of a speaker, or speakers, and are heard as the amplified music or speech that was picked up by the microphone.
             Most dynamic mic elements work in a similar way, but the design of these CM and CR elements is much different than typical moving coil dynamic elements, which work pretty much the same way a speaker works but in reverse. Typical moving coil elements turn the mechanical vibrations of the diaphram into electrical signals via the coil winding around a fixed magnet which is constructed very similar to the way a speaker is constructed. These dynamic elements turn mechanical vibrations into electrical signals, where as a speaker turns the electrical signals into mechanical vibrations. The CR and CM elements work in a much different way making them very unique. Their unique construction makes them much more durable than just about any other type of microphone element.
Frequency Response
            The elements are said to have a frequency response of 100 to 7,000 Hz, or cycles per second. They were designed mainly for good speech reproduction. This response range is where an average persons speech lands. This range also happens to be the range in which most harmonicas play, but many of the higher pitched harps will go well above 7,000Hz.These elements also have a high gain figure. The spec sheets list them as having an output level of 52.5db below 1 volt per microbar (high impedance models). Low impedance models were rated at 71.5db below 1 volt per microbar (open circuit voltage). The lower the db (decibel) rating, the more gain the mic will have. I have had conflicting literature and specs sent to me by Shure. One spec sheet may say that the elements had a freq. response of 100 to 7,000Hz, and others that say the same model 520 had a freq. response of 100 to 9,000 Hz. Another spec sheet on the 520D from 1986 listed the mic as having a frequency response of 100 to 5,000Hz, which were the dual impedance controlled magnetic elements that for the most part seemed to be a bit brighter than the older models.
         So which is correct? In my opinion, all of them! I have heard elements of the same model differ enough to say that some of them may reach the 9,000Hz range, but for the most part, I think most are closer to 7,000Hz. The literature sent to me was from many different periods in time, from 1949 through 1967 for the 520. One sheet with a date of 1959 would have the freq. response listed as 100 to 7,000CPS, and one from 1961 would have the response as 100 to 9,000CPS, and then another from 1964 would say 100 to 7,000 CPS again, so possibly they noticed the subtle changes from one element to another too, and decided to change the specs although no changes were made to the microphones.

Replacement Models
         The older elements that came as a replacement model were what people today refer to as an R5. The "R5" is just the replacement model # that Shure used for the earlier mic models, just as an "R7" was replacement model # for the 707A mic crystal elements. This replacement number was used up until the dual impedance model came out in 1970. Some people seem to think that an R5 is some special model. It's not. It's just the replacement cartridge model # that Shure used for the older CR and CM elements. The dual impedance replacement model # was R44D. An R5B was a replacement model # for low impedance mic models.
           The modern day 520DX has a given frequency response of 100 to 5,000HZ, which I think may be more accurate than the specs of the older models which will differ from one to another. The 520DX does not seem to have as much high end as the vintage models, and they all seem to be pretty consistent in tone. The 520DX does not use the same element as the vintage models, as described later on. 
           These CR and CM elements were used in many different types of microphones. Some with the bullet shells, and others in handheld casings, and others in desk stand type mics. The type of microphone housing does have an affect on how the elements respond. Some mics had the elements sealed front and back much better than others as well, which also affects the response of the element.

                                                                                       Tonal Differences
          It has been my experience having had played literally hundreds of these elements, that each one will have some tonal characteristics all its own, having tested them all in the same mic shell using the same cable, amp and settings. They all seem to have minor tonal differences, sometimes big differences, but for the most part, minor differences that are not usually very noticeable to the average person. Some elements of the same model # and even the same date code will have some tonal differences between them. For example, some are brighter sounding, some are stronger in the mids, or some may have a better bass response than others. I've found this to be more noticeable with the older black label CR's. This may be because of their age, but they also had some different materials used on them like the glue that secured the diaphram to the pin that transmitted the vibrations from the diaphram to the armature. The CR's have a small metal disc that was glued to the diaphram and pin. Many of the early models used a glue that these days has become brittle, and has caused the disc to loose contact with the foil diaphram causing the element to sound weak, or dull. Most will work even though the glue has lost its grip on the diaphram, but the elements suffer in one way or another tonally.
          Some of the very first models used a magnet hold down assembly that consisted of four pieces of metal that all must be kept precisely in place as opposed to the two piece magnet holders used later on. These metal pieces were sometimes not perfectly aligned, and would cause the gap in the armature assembly to be inconsistent from one element to another, which is another reason why the early models were more inconsistent in tone as compared to the later models.
          Another thing I see on a lot of the old black labeled models is corrosion forming under the magnet assembly. This can cause the magnet assembly to be pushed upward, which knocks the alignment of the magnetic armature out of whack making the elements sound weak or bad. Many times this corrosion cannot be seen, even though it is bad enough to make the element sound bad. For the most part though, the bulk of the elements have just minor differences from one to another. There are some that for one reason or another stand out from the rest. These are few and far between, so don't set out to find one unless you've got a lot of money to burn. You could buy 75 or 100 of them before you find a real kicker.
                                                                                        Performance Facts 
          Some people tend to think that certain models sound better than others. I haven't found this to be the case, as I said before, each one will have some tonal quality unique to it. It may be because a person happened to get one of a certain model # that sounded better than a couple others that they've tried. I've heard a few people say that the model 440 bullet has a better tone than the 520. The model 440 uses the exact same model element that the 520 uses! The difference is the shell. The 440 bullet has a much larger, single vent hole in it on the bottom of the shell below the tag, as opposed to the 2 small vent holes that the 520's have. This will alter the sound of the mic. It may also be a cause of excessive feedback!
          Another thing that I've heard people say is that the higher the resistance reading is, the more gain, or hotter the element will be. This is nonsense! Differences in resistance of the windings is not going to determine how hot an element will be. At least not at differences as small as 100 or so ohms on a high Z controlled magnetic element as used in today’s applications. Yes, a low Z CM element will not have the gain of a high Z element, but the difference in resistance is much larger, and they're usually plugging them into a guitar amp that has 1 meg or higher input impedance. While it is true with certain microphones, a small difference in resistance with CR and CM elements is not going to make an element stronger or weaker than another. I have had CR's close to 1,400 ohms that weren't any stronger than CM's that were 1050 ohms. In fact, I've had some lower resistance elements that were much hotter than elements of higher resistances. There are many things that determine how much gain these elements have. Slight differences in resistance is not one of them.
            There are many things that can affect how well an element of this type performs. I can't get into everything, but the main ones are magnet strength, armature alignment, diaphragm condition, debris getting into the magnetic assembly, crud collecting on the diaphram and corrosion build up. I've had people send me elements that they tried to clean up with steel wool. Not a good idea! NEVER clean a magnetic element with steel wool, and if you use it to prepare a shell for painting, make sure that you remove the element from the shell and store it in a zip lock plastic bag or something to prevent it from coming into contact with the metal dust from the steel wool. The magnet will suck the fine steel into the magnetic assembly and the element more than likely will need to be disassembled and thoroughly cleaned.  Using brass wool is not a good idea either as the metal dust can still get into the assembly and cause problems. If you must clean up your element, use a lint free cloth with water or alcohol if needed and do not stick anything into the little holes in the face of the element. If your element needs to be taken apart and cleaned, do not attempt to do this yourself. You'll likely end up ruining the element. Send it to a qualified technician.

Element Model #'s
          As I'm sure most of you know, Shure put quite a few different model numbers on these elements. I believe there are 15 or more that all look the same. There are some models that have only a single hole in the middle of the diaphram cover (element model 99AM556). Some have the large center hole with 6 small holes around the center hole, and the ones we all know and love that have a total of 14 holes in the diaphram cover. There are also some that have a raised ,somewhat smaller diaphram with a single hole that were used in military and other handheld communications mics that were designed for use in very noisy environments. These were designed to be put practically in your mouth when you speak into them. They came with a rubber piece on the mic cover that you put right on your upper lip to speak into. The element model # was 99D561.
           There is also a smaller version of the controlled magnetic transducer that Shure used in the model 430 Commando microphone. These mic's are OK for harmonica, but they do not have the same sound that you will get from a 520 green bullet. They are much lower in gain and not as gritty either.
          Most of the elements that have a single, or fewer than normal (14) holes in the diaphram cover were meant for use in handheld communications mics that were designed to keep out stray noise, and were made to be spoken into with the mic positioned very close to your mouth without being overdriven.
         In 1949, there were only two different models that I know of. The first model to be used in the 520 green bullet mics was 99A86. Then they switched to the model 99B86 either sometime in late 1949, or early 1950, to be used in the 520. In 1950, the models 99G86 and the 99H86 were used in other types of microphones. In 1952, the medium impedance model 99E86 was introduced, which was a 300 ohm element.  In 1970, the model 99S556 was introduced which was a dual impedance element used in the 520D green bullet mic. This is the model that was used in all the green bullet's up until they stopped production of the controlled magnetic elements. The modern day 520DX uses a whole different type of element and it does not sound like the vintage mic's. Over the years, Shure used many different model numbers on the CR and CM elements which were used in many different types of microphones for other companies as well as their own.

High and Low Impedance Model #'s
          There are a number of models that are all high impedance, as well as a bunch that are all low or medium impedance models. I can't remember all the model #'s I've seen over the years but here's a list of the more commonly seen models. High Z models were labeled as one of the following models: 99A86, 99B86, 99F86, 99G86, 99H86, 99K86,and 99X86. The F, K, and X are really not common models, but I have seen a few, mostly in older model mics of various types.
           The first medium impedance models (100 to 300 ohms) were mostly labeled as 99E86 being the most popular, and some others that were used mainly in handheld and desk stand communications mics that were labeled 99AP556, 99AT556, 99AF556, and the 99E86 model mentioned above. I have seen one model which I don't remember the model # of, but it had very thick winding wire and measured 3 ohms. A common low impedance model is the 99C86 which is a 15 ohm model. The 99C86 was introduced in 1960 and at that time used in the low Z model green bullet mic's labeled as a 520B, and the desk stand model known as the 520SLB.
         One noticable thing about the low and medium Z models is that they have a red, blue or purple colored plastic bobbin as compared to the white ones used on all the high Z models that have a plastic bobbin. The medium Z models can be used with good results for harp with most amps, but are better suited for amps with lower than normal input impedances. When used with most amps that have a 1 meg ohm input impedance or higher, they will be noticeably weaker than the high Z models, but will usually have a half way decent tone. As far as construction, they are all made the same way with the same materials with the exception of the 99D561 used in the military handheld mics. I believe that other than having different impedances, all the different model numbers were mainly used to identify the elements used in all the different models of mics that they were used in.
         As you can see, there are a bunch of high Z models that are all the same but have different model numbers. The same goes for the medium Z models. Shure made these elements for use in many other companies microphones, and likely used a certain model # element for each one. As far as I know, the high and low impedance models have the same frequency response specs, and were made the same way with the exception of the models that have fewer holes in the diaphram covers. So I would think that it just made it easier for Shure to keep track of what types of elements went to the different companies for use in their mics.

Model #'s used in Green Bullets
          As far as the green bullet mics, Shure used at least four different models of elements in them, not counting the current model now being used in the 520DX which I believe is model 90A4482. First the black CR 99A86, then 99B86, and in 1954 when Shure began to use the white labels and plastic bobbins, they were still being called controlled reluctance transducers, but they changed the model number from 99B86 to 99G86. Physically, the two elements are identical. The 99A86, and the 99H86 are also identical in construction. The only difference between the two pairs is that the 99B86 and 99G86 both have the negative lead of the elements grounded to the element body. The 99A86 and the 99H86 do not. What this does I'm really not sure. I do not believe it has any tonal affects and I don't know if it was for the purpose of eliminating hum or what, but neither type has any hum problem when properly installed in a microphone.
          Shure used the 99G68 in the 520 mics up until 1958 when they made the transition from calling them controlled reluctance to controlled magnetic. They then switched back to the 99B86 model number, and continued to use that model # until the creation of the 99S556 element in 1970, which was a dual impedance model that they decided to use in the green bullet mics. Shure then changed the mic model to the 520D, and produced them in Evanston ILL. for a short period before shipping them off to be assembled in Mexico.
           The 520D's made in the USA had the same green tags that they always had, but they began putting a serial # on them where the impedance used to be stamped. When the move to Mexico took place, the shell tag was changed to the silver and black type now being used on the 520DX mics. The 99S556 dual impedance element began production in Evanston ILL., and have the same white labels as the older CM's. Some of the earliest Mexican made elements have this same label, but have the "Made in USA" blackened out with marker, and are stamped "Assembled in Mexico" on the side of the label.

CR's vs. CM's
         I often get asked, "what is the difference between a CR and a CM"? Well the black labeled CR's have an obvious difference in the material of the winding bobbin. All the black label CR's have the phenolic bobbin, and the very first white labeled CR's have them as well, but not many were made before switching to the plastic version. CR's also have a small cymbal shaped metal disc that Shure used to glue the foil diaphram to the center pin of the magnetic armature pickup. You can see it glued to the center of the diaphram of all CR elements. I have never seen a CM with this disc. I do not believe that there were ever any CM’s made with the metal disc on the diaphram.
          There is also a slight difference between the two as far as how the winding wires were ran to connect to the lead wires of the element. I have seen a very few CM elements that were wired the same way as the CR's, and all were made right at the time when Shure started calling them controlled magnetic transducers. Many people like the tone of the CR's better than the CM's. I think the two are very close in tone but the CR's have a slightly grittier tone to them. This is likely attributed to the metal disc on the center of the diaphram. Other than that, a white label CR and an early 60's CM are basically identical.
           There appears to be a lot of hype over the black label CR's these days. I really can't explain that. I think that the white label CR's have a tone that is just as good as the black labeled CR's. As I mentioned earlier, you will occasionally find one that really stands above the rest. This goes for all the different models of CR's and CM's too. If you happen to find a really good black label CR, it will likely be the best harp element you've ever heard, but again, they are very few and far between. Trying to find one today could put you into debt if you get carried away trying to find the ultimate element! You're better off paying someone whom you know has one the big money for it instead of trying to find one on your own. 
           There are some very exceptional white CR's and CM's too. You're more likely to find a really good white CR or CM because the construction of the later elements was more consistent due to refinements in the parts they used, and better glue used to secure the diaphram to the pin that transmits the vibrations from the diaphram to the magnetic armature.
        These day's, the prices have gone through the roof for the CR elements. This is because there are now a bunch of people seeking out every microphone ever made that has a CM or CR element in it on ebay. Some of these people seem to have deep pockets too and are bidding on every mic they can find with a CR in it. This is unfortunate for those who would like to buy a CR element, but you don't have to pay that kind of money to get one if you know where to look for them (see the page on collecting vintage mic's). These few people who are paying upwards of $200 and sometimes as much as $300 for mic's with CR's in them are apparently so greedy that they won't let one or two pass by. They apparently are not mic builders, as they can't possibly make a profit on them buying at these prices. I can't imagine the prices going any higher but I wouldn't be surprised. Nobody in the right mind would hoard these things and pay $200+ for each one. They'll be lucky to break even if and when they decide to sell them. If you would like to get a CR for your mic, you can get one for as little as $5 if you are patient and know where to look. The last black CR I bought I paid $2.75 for. Thats right, $2.75, not $275. I've purchased mic's with high Z CM's in them for fifty cents too. These deals are not that hard to find, and if you're patient, you'll get your element dirt cheap as well. DO NOT look to buy elements on ebay unless you're prepared to pay 100 times more than you can get one for elsewhere. Let the CR hoarders (you all know who you are) pay out of their noses for them on ebay. They will end up eating them for lunch when they find out they can't sell them at a profit.  

The Newest Green Bullet
           The latest version of the infamous green bullet mic is the model 520DX. Now the 520DX mic is a different story. That’s because it's a different animal. The new 520DX has a regular dynamic element with a plastic diaphram in it. Shure claims it was made to sound like the old ones, but it doesn't quite cut the mustard for most harp players. It does have a decent tone, and many players like it, but it's much less raspy than the vintage mics and just doesn't sound like a vintage green bullet. It does have it's place in that it really doesn't sound like any other harp mic on the market, and some players like having a mic that is somewhere between a 520 and a vintage vocal mic.
          Modern vocal mics have a frequency response that goes way below and above the response of vintage mics, and don't make for good harp mics at all unless you want to have a more natural acoustic sound. One very important thing to keep in mind is that these elements are pressure actuated. They must be mounted properly with the proper gasket to form an airtight seal around the front, and the back of the element. As many of you already know, the cupping technique can change the tone of the mic drastically. Forming a nice airtight chamber with your hands is sometimes difficult, but doing this will allow you to get a bunch of different tones out of your mic.
          Choose the right shell, and have a reputable mic builder build your mic for you to make sure it done right. If the element isn't sealed properly, you'll be loosing tones you otherwise may be able to produce. It's sad that Shure decided to stop making the CM's, even if they were assembled in Mexico. I think they were a better harp mic than the 520DX by a long shot! Thank God the CR's and the CM's were built to last and should be easy to find for many more years to come!

                                                 CRYSTAL ELEMENTS
Shure Mics and Crystals
          I'm really not a real big crystal mic fan, mainly because they're so darn fragile and most aren't known for their big fat tone, and the fact that I'm content with my collection of CR's and CM's. Shure introduced one of the best, if not the best crystal mic ever made in 1940. The 707A. It was first introduced in 1940 and was identical to the 520 green bullet physically, but the shell was painted grey and was slightly smaller than the 520. It did not have any vent holes in it like the 520, which had 2 small holes drilled in the bottom side of the shell. It came with a chrome plated grille and a Bimorph Rochelle Salt crystal. It has a frequency response of 30 to 7,000 Hz, and output rated at 50db below 1 volt per microbar! In other words, some serious output!
          These mics had the biggest, fattest tone you'll ever hear from a harp mic although it wasn't made to be a harp specific microphone. It was made for the same uses that the 520 was made for but it was a stronger, louder mic, and needed an input impedance of at least 1 meg ohms, but preferably higher like 3 to 5 meg ohms. The elements that came in the 707A in the 40's were model #99-131. Over the years, Shure changed the shape of the element but used the same bimorph rochelle salt crystal. They were made up until 1970 before being discontinued.
          I believe it was sometime in the early 50's that Shure changed the shape and the model # of the crystal element. I have seen them labeled as 99A94, 99B94, and 99A47, and the date was usually clearly stamped below the model # on the back side of the crystal. These days, the crystal which was the 99A94-99B94-99A47 is better known by Shures replacement model number which is R7.
          Around the late 40's or early 50's, Shure also went to the larger full size bullet shell, the same size as the 520, and painted the shell silver with a brushed nickel grille like the old 520's had. Over the years, Shure used a few different types of tags on the shells. The very first ones were a small metal tag, black and silver in color. Then in the 50's they used a larger tag with embossed lettering, similar to the 520 tags but they were black and silver. Shortly before Shure moved from Chicago to Evanston in 1956, they switched the tags to an embossed type silver and blue tag. After the move, the tag again changed to the smooth type and were an off blue color. 
           The older smaller shells were not much smaller than the full sized shells .To give you an idea, you can put the grille of a full sized 520 on the smaller shell and it would fit, but it would have a slight lip, about 1/16 of an inch at the most around the diameter of the shell. You could also put one of the smaller grilles on a full sized shell with the same result. They do however seem easier to hold than the larger shells for some people. Shure also made another bullet mic that used the same crystal element as the early 707A’s. The mic was painted all brown, both shell and grille, and had a label that said, "Specially Designed for Recording" on it with a model # of 9822A but I know it also had another model # on some of them for some reason, which I believe was 9822B. I never collected many of these because finding one in good condition is difficult, and finding one that still works is a lot more difficult, but there are a few out there. They usually sell for a pretty good buck even though they're dead. I did eventually find a primo condition working 9822B which has fantastic tone and about as fat a low end as you'll ever hear from a crystal mic.

           Shure also produced a couple other bullet style mics back in the late 30's early 40's which were the model 7A, and a moving coil dynamic microphone that was made in 1939 only. This was the model 5, which came in three different impedance versions, the model 5E low Z, model 5F medium Z, and model 5G high Z. All three models came with the smaller version shell in all brushed chrome. Needless to say, they are very rare to find these days.
The MC-151 & Others
         I'm not really not a big fan of the Aststic crystals, although they did produce some very good ones from time to time. The early Aststic crystals were made by the Brush Co. which also made the early crystal elements for Shure mics back in the 30's. Both the early Shure and Astatic mics had Brush Co. stickers on them. Shure went on to patent theirs and so did Astatic. The most popular of the Astatic crystals is the ever popular MC151. This crystal dates back to the 40's I guess in various forms as you can see on the picture page. They also had a larger, thicker crystal that they used in the model 30 mics, better known as the "biscuit mic" , that came with old console units that had recording capabilities back in the late 30's and early 40's. The biscuit mic has a small round shell that’s very easy to hold and is very popular with harp players, especially those who have a hard time with the larger shells. I've seen the crystals in those mics with many different model #'s on them. They were good crystals, but 99% of them are dead or very weak these days.
           The JT30 is by far the most popular of the Astatic mics. Many players like them because they are slightly smaller in diameter than the Shure 520, and they have a nice old art deco look to them. These are the mics that made the MC151 popular with harp players. It seems to me that the older ones have a much fatter tone to them. I have a couple from the early 70's that still have a nice bottom end to them, and are much fuller sounding than most of the MC-151's I've heard in new mics.
           For the most part, the MC151's, which were discontinued in the late 90's, had a tone that many describe as "tinny". In other words, too crisp in the high end, and not enough low end. Some of the older ones were very good and had excellent low end response and grit, but most, especially the last of them were lacking low end response and sounded thin. They had a signature sound for sure and were preferred by many players who like their tone. In my opinion, as compared to a typical CR or CM, the MC151 does not have the grit and growl that the Shure magnetic elements have, and they usually lack low end response.
          It appears that the MC151's differed from one to another like the Shures, but not quite as much. Some have a decent full tone, and some are very thin and have no bottom end at all. It seems to me that the MC151’s made in the 70’s and 80’s were the best of all the MC151’s ever made. I did however purchase a few crystals from Astatic in 1994 that sounded very good. From then on, until they were discontinued, the tonal quality went down fast. When the word got out that the JT30 and the MC151 were being dropped from the Astatic line, people started buying the mics and elements like crazy, including me. I bought 2 Blues Blasters and 2 spare MC151 crystals. Well, here's how much I liked them. I sold all 4 elements immediately. They were all very thin sounding, no bottom to speak of, and weak to top it off. They sounded as if Astatic took their batch of rejects from the past few years and stuffed the last run of mics with them. I, and many many others were very disappointed in the quality of those crystals.
           The Hohner Blues Blasters are still being made with small crystal elements made in Japan. I've played a few of them, two of them that a guy who bought 2 Blues Blasters sent to me to swap the crystals for vintage CM's. He didn't even want the crystals back! Since then I’ve had a bunch of new Blues Blasters sent to me to swap elements in because the new crystals are very high gain, thin and squeaky sounding with no nads at all! So I guess there’s no need for me to comment any further on those!
           The only other decent crystal elements that I've heard that are worth seeking out are made by Aiwa and Turner. I've had a few of the Aiwa's but only one had the Aiwa logo cast into the body of the element, but they were all identical and sounded the same. I assume they were made by Aiwa, or possibly by Argone. They have a very good bottom and strong mids without overpowering highs. The Turner crystals came in the CX and BX model mics which are exelent crystals as well. Nice crystals, way better than the MC151’s, but in my opinion, the best crystals ever made are in Shure 707A's. The bummer is that those crystals didn't handle the test of time well, and finding one at 100% full strength today is near impossible. I was fortunate enough to find a 1964 model on eBay that was tucked away in an old ham radio operator’s closet. Still in the original box with tags and all. Brand new in the box basically. Check it out in the pictures section along with my very rare small shell, all brushed nickel 1949 model 520, and examples of all the mics and elements mentioned on this website. 

Dating the Elements
The 3 Digit Code
           One of the question’s I get the most is "how can I tell when my mic was made"? Well, it's really not documented anywhere but I have been able to come up with some information. From 1949 and up to 1951, the black labeled CR's had an obvious date stamped on them, for example,10-49, or 12-50. I believe it was in 1951 that Shure began using a 3 digit date code. From looking at the elements over the years of collecting and noting the different changes in the mic shell tags, the dates on paperwork that came with some mics, and even receipt’s still in the boxes of mic’s I bought, I believe that the 3 digit date code works like this.
          The first digit is the year of manufacture, and the last two digits are the week of the year that they were made. For example 322 would be the 22'nd week of 1953, and 943 would be the 43'd week of 1959, or, October 1959. This type of date code system was used up to December of 1960 when Shure began to use the 2 digit date code system. You will see that the very first CM elements had this type of date code on them. 
         I haven't seen a black labeled CR with a date code that began with a 4, but as far as I know, they were used up until late January or early February 1954. I have seen very many white labeled CR's with date codes that begin with a 4, as well as a few white labeled CR's with the phenolic bobbin construction with date codes that begin with 4. The few that I've owned had very close date codes in early 1954. I do also have a CM element with the same wiring construction as the CR's that has a date code of 827, which means that it was about this time (July 1958), that the elements began being labeled as Controlled Magnetic Transducers. This element does not have the disc on the diaphram as seen on all CR elements, but it does have the different wiring configuration that all the CR's have. I have had many regular CM elements with the date code beginning with 9, so I guess it's a safe assumption that the name change happened at about that time. I don't think I've had any white labeled CR's with a date code beginning with an 8, but I do have some with a 7 as the first number of the date code. So I guess it's safe to say that the CR's fizzled out sometime in early 1958.
The 2 Letter Code
           In January 1961, Shure began to use a two letter date code system. The letters ran alphabetically beginning with the letter A as 1961. The first letter of the two designates the year the element was made, and the second letter designated the month, with A being January and running alphabetically down to December with the letter L being December. The tricky part of this code system is that it went for 20 years using the first 20 letters of the alphabet. So, the letter A could be either 1961, or, 1981. Or for instance, J could be 1971, or, 1991. In this case it wouldn't be too hard to figure out which year it was by looking to see where it was made. If it says Mexico, I think you can figure it out that it was made in 1991.
           Some elements may have you guessing though, like the ones that may have been made in the late 60's or, possibly 80's. There is a way to get some hints though. On the early 60's elements, as you'll also see on the white labeled CR's, the date codes were stamped in small letters with red ink, like the small numbers on the later white label CR's. Also, the labels themselves are different on the early 60's elements than they are on the elements made in the 70's and 80's. The early labels were made from a dull looking cloth like material. You could actually see the threads on these labels that had a dull look to them, kind of resembling a piece of canvas. Sometimes, a thread would even be frayed on the edges.
           Sometime in the 70's, they started using labels that had a slightly glossy look to them, and the lettering was now being stamped with larger letters as compared to the early small ones. There is an obvious difference in appearance of the cloth like labels as compared to the glossy type. How long were the cloth like labels used? I don't know for sure, but if your element has this type of label, it's probably a safe bet to say it's a 60's element. It's at least safe to say that it will be the earlier of the dates if you're not sure. 
           I believe that Shure produced high impedance elements through the 80's here in the US, but they were not the elements being used in the green bullet mics. They were being used in the model 444 desk stand mic’s, and similar mic’s made for General Electric and other companies. A lot of these elements are being found in harp mic’s these days and they sound just as good as the older ones. Most of these elements are model 99A86, which is the same model used in the very first 520's. Most of the 520D green bullets made after the 70's were made in Mexico. All 520D's had controlled magnetic elements with a model # of 99S556, even the limited number of 520D's that were made in the US, but those models clearly had labels that said “Made in the USA”, and green tags on the mic shell.
         The Mexican 520D's have cheap paper labels on the elements that rip easily, some even had perforated lines where they would fold over the edge of the element assembly. They all clearly state "Assembled in Mexico", so dating these mics is not a problem. Whatever year the letter designates with this type label, it's likely a mid 80's to 90's date code.

Controlled Magnetic Elements Showing the Two Types of Date Codes

          I believe that Shure is still using the 2 letter date code for the 520DX. What date they started at I haven't a clue, but I doubt there are many people out there wondering when their 520DX was made. It's a safe bet to say it was within the past 10 years. The 520DX began production in 1996. If you're still having trouble trying to figure out the year your element was made, there are some other clues such as the tags used on the shells that may help, but this information should help you determine exactly when your mic or element was made. I'll pass along any other clues and info as I get them, or change any dates that I find out may be wrong, but everything here is fairly accurate as far as I know. I'll also be posting some dates on pictures of the various mics, tags, and elements as I get them on, to show when the various materials were used. If you still have any doubt as to the date of your mic or element, email me a close up picture and I'll try to help you determine when it was made. Please try to keep any pics as small as possible (100k bites or less). Thank you!  Questions?? Contact me at