A few of my last posts have been commented to be "straight from lecture", as in me copying what my teacher said and posting it. I realized I was definitely inspired by my classes to write some of the previous posts, and now that I am out of that class I feel I can write freely again.
To remove myself from thinking too hard about it, I'm just going to write about a subject I have never had a class on so there can be no lame copying and to everyone it will be new information.
Todays topic is microphone design. This is an extensive subject and I am not even going to scratch the surface. There are two design elements to a microphone that I am going to try and explain: electric and acoustic.
Microphones, in their basic form, are simple to understand. You have a capsule that converts acoustic pressure into an electrical signal. What all microphones do is split that signal into two amplified versions flipped 180 degrees from each other. When two signals are flipped 180 degrees out of phase from each other and sent down the XLR cable, inductance may occur. If an interference is picked up by the cable it will cancel itself out when the two signals are flipped back in phase.
The circuit of the actual microphone varies, of course. I don't understand electronics all that well, which is why I search online to find microphone schematics. The little bit I know helps me choose a circuit I want to build, and I'm on my way. (The circuit I am currently studying is a tube microphone that needs phantom power instead of a power supply. We'll see if it works.) One thing the circuit needs is shielding around it. Correct me if I am wrong, but I believe this acts as more of a protector against interferences in the air surrounding the mic such as electromagnetic disturbances when a cell phone receives information, and not so much a ground for the microphone's circuit to send unwanted signal.
The acoustic properties of a microphone are critical. Sound can be manipulated in many ways, and if the design of the microphone is incorrect, that sound can be hitting the capsule in unwanted ways. The capsule should be separated by a barrier of some kind from the rest of the body. The body of the microphone is more or less a hollow tube where sound can become trapped and reflected back into the capsule. I had just built a microphone out of a 2" brass tube, and put a barrier further down into the body so that the capsule was right above it. 2" of circular tubing creates a standing wave of 6.78kHz which bounces straight back into the capsule and causes vocals to sound very nasal. I put a barrier cutting off the capsule from the tube and prevented that standing wave from ruining my microphone.
The grill is possibly the most important acoustic element in the physical microphone design. The way that sound propagates past the thickness of the mesh wire and the width of the spacing between the wires is a tricky relationship to understand. Throughout my research on it, I have come to find that the larger the spacings in the mesh, the more open the mic will sound, and on the contrary, the closer the spacings, the more direct your mic will become. I have no idea what wire size has on the impact of the sonic quality. I can say this, the thinner wire will be easier to mold, but easier to dent. I suggest a combination of the two, with the thinner wire and thinner spacing mesh on the inside, while the thicker wire with larger spacing is on the outside.
Neumann has a patented grill shape that they use for their large capsule side-address condenser microphones. It is a rectangle shape at the top, and as it gets to the body of the microphone, it becomes a cylinder. This shape allows for zero standing waves to become trapped inside the grill of the microphone. AKG 414s have a similar design. My dad suggested studying the design of the stealth bomber, which was designed to minimize radar reflections as much as possible. (If only I can figure out how to do that in to the inside of the enclosure...) Some designers will put acoustical treatment inside the grill, such as foam padding to absorb the sound, with a hole cut out in front of the capsule for the sound to come in.
That's sort of all I can tell you for now. I don't understand much more of it, but hopefully you can now understand microphones a little bit more now because of this. Perhaps not on the building level, but I sincerely hope that you have a curiosity for how the equipment you use works.
So I got this new tape machine, and I've been somewhat disappointed with my luck with tape machines. I just want a tape machine that a) can playback what's being recorded to tape b) can run at a constant reliable speed of at least 7.5 ips, and c) sounds decent.
So far I've only met 2 of those requirements. The one I am currently using doesn't play back what's being recorded to tape, which is annoying when I'm trying to use it as an effect. It sounds decent though, and surprisingly can keep a constant speed (after applying at least a gallon of oil).
This was a suitcase style reel to reel tape machine, with detachable speakers. So I was recording the piano when I decided to take the machine apart, and I started fiddling with it, as usual. Then I took the piano apart, and started figuring out how that all worked. Basically then I put the speakers inside the piano, put the piano back together, and played my recordings of the piano.
I used a stool to hold down the sustain pedal and I basically made a reverb out of my piano. I think this would be a great way to turn MIDI piano into a more realistic piano. My problem with MIDI piano has always been the fact that when a note is played, the other strings don't react, reducing the resonance that a piano is known for. By playing your MIDI piano through a real piano with the sustain pedal down, you can record those strings resonating, and it should sound more like a real piano, because it is one!
Next what I'm going to do is get some speakers, mount them on the inside, and have an auxiliary input so I can play music from my iPhone into the piano.
So you're listening to a record that has a kick drum that's rattling your car and pumping through your chest, and you're wondering why your kick drums always sound dumb and flabby. One way to get that super low bass coming out of your kick drum is to use a subkick, which is a speaker.
A little bit about why this works: a microphone is a pressure sensitive element moving back and forth converting acoustic energy into electrical energy. A speaker is a device that converts electrical energy into acoustic energy. These devices are called transducers. It's exactly like how a windmill can create electricity from wind, and a fan can create wind from electricity. I guess a fan is a transducer...
A little bit of history: Don't ask why, but the Yamaha NS-10m is one of the most popular speakers in studios ever. Engineers would put the speaker right next to the kick drum resonant head (NOT the porthole) and the acoustic pressure wave that resonated off of the resonant head would vibrate the speaker in and out. They would just use an XLR male-to-male connector, or patch it some other way, and they'd plug it in just like a microphone, and out would come FAT BASS!
Before you go rushing for your stereo system and taking it apart, it's important to know the sizes of speakers that work well for this application. A kick drum is a huge instrument, and produces huge pressure waves, known to you as fat bass. You've got to get a speaker moving back and forth 40 to 60 times per second in order to get that fat bass you want. Yamaha's NS-10m speakers are about 7 inches in diameter. Yamaha caught on, as always, and to sell more stuff, they created this:
It's basically a 10" speaker inside of a drum-shell. Genius. To be honest, I don't like this thing much, and all of my best luck with subkicks have had wires hanging out the back and were hanging from a stand with duct-tape.
So go find a speaker. I recommend 8-10". I used a 10" Fisher speaker that I found off craigslist for 10 bucks. I took it out of the speaker cabinet and started soldering.
What I did, since speakers were not designed to be microphones and therefore have a very hot output, was put a pad on it. The pad was about 15-20 dB, and I did it by using a bridged voltage divider out of resistors. On both the cold and hot connectors of the driver, solder a 1KOhm resistor to each of them. Across the two resistors, solder a 150Ohm resistor. Then connect pin 2 and 3 to the hot and cold ends of the 150Ohm resistor respectively. This will be a passive attenuator so that you have a better input level.
Get creative on how to put this thing on a stand. I used wood, and metal brackets that aligned with the speakers screw holes, and just made a hole big enough to put on a stand, and tightened it in place with washers and nuts.
This is a pretty easy project, so go make your first microphone!
Here are some pictures of mine.
Yes, that is a live application. Routed directly to the subwoofers. Ah yeeah!
This might be an interesting post. I'm just going to drown myself out with some vinyl In Rainbows and type this. I seriously need to get this blog together theme-wise. I'm sorry that I don't have pictures for all of this, but you're just going to have to trust me. I have an audio file to prove it.
Alright, in this post I will describe two recording techniques for drums, that only take up 2 channels, and don't use more than 3 microphones. These techniques are as old as The Beatles, and require a well tuned drum set, and a drummer who can play. (That's important.) Off we go.
Recording drums can be a bit tricky, and when you only have an M-Box mini with 2 XLR inputs, you have to resort to recording multiple tracks. Another way of adding more mics is adding a mixer like a Bheringer 8 channel mixer, and take the main stereo outputs of that into your M-Box, but this still only gives you two channels when you track to Pro Tools, or Logic. If you have both of these programs, you can use my instructions on Syncing Logic to Pro-Tools that I posted in December and get 4 tracks going! It saved me once, that's for sure, and I used one of these techniques I am about to describe to you.
Recorderman Technique (2 mics)
The first technique requires two microphones, of the same make and model. It's called the Recorderman Technique. It's an old technique, but apparently was recently named "Recorderman" after a DIY recording blog. (Kind of like this one....) The type of microphone is up to you, and depends on the sound you want. I like to use AKG 414's for both of these techniques. The U87 is also probably a good choice, but you, in your bedroom, probably can't afford this, so I'll suggest that any condenser mic would do the trick. Hey, use 57's. It's been done before, and worked well.
You will need the two microphones, a long piece of string or an XLR cable and two drumsticks. (Or a tape-measure.) The first microphone will go over the snare. Some say the center of the snare, but it honestly doesn't matter, as long as you're measuring from the same distance. I like the 11 o'clock lug nut on the snare that's closest to the first tom and the hi-hat. Directly above this point is where you will place your first mic, pointing directly at that point. Use your two drumsticks end on end to measure how high it should be from the point on the snare. It doesn't need to be exact right now, we'll move it as needed. Now, sitting on the drum throne, the second mic will go behind your right shoulder, equidistant to the snare. Here's where the string comes in. (Tape measure though, if you want to get all phase-coherent when adding a spot mic on the kick.) Measure 3.75 ft. from the beater of the kick drum to the end of the capsule on mic number two. Make sure the snare is also 2 drumsticks length away from the point you measured on the snare.
Almost there! Take the end of one of your strings and hold it in place with the beater pressed against the kick drum. Run it to the "shoulder" mic, and back down to the point on the snare. Don't start playing cats cradle. Now, with your fingers holding the end of the string to the point on the snare, and your other hand pinching the string where it met the microphone capsule, swing your pinching fingers over to the other microphone to ensure that your mics are both equidistant from the kick and the snare.
These level of these microphones being recorded should yield the same level when the snare drum is hit. Pan the mic above the snare Left, and the other one Right, however much you want, and you should have a pretty nice sounding recording!
Glyn Johns Technique (3 mics)
This technique is named after the famous engineer Glyn Johns, who recorded The Who, The Rolling Stones, The Eagles, The You Name It. He also did Led Zeppelin, so think Led Zeppelin when you think this technique. This one is easier to set up and requires three microphones all of the same make and model. (Some people say this technique is a 4 mic technique, but fail to realize that the 4th microphone is a spot mic.)
Here's how it works; take your first mic, and place it in the same place above the snare as the recorderman technique, measured from the same point 3 or 4 feet. (The further you go, the more room sound you will get.) The second mic will be to the drummers right hand side, a few inches above the floor tom. This will be pointed at the snare, and equidistant from the snare as the first mic. The third mic will then be placed just above the lip of the kick drum, a few inches, and moved back about a foot. This one is hard to measure because of the toms, but it should also be equidistant from the snare. Use an XLR cable or string or a measuring tape to get the distances right.
Again, all three of these mics should have the gain set so that when the snare is hit, it yields the same amplitude on each of them. Pan the mic over the snare to the Left, the mic beside the floor tom to the Right, and leave the mic in front of the kick in the center. If you're using a mixer, use the mixers main L+R outputs to go to your laptop or whatever you're using.
I've been talking about spot mics here and there throughout this post. Spot mics are basically close microphones to pick up any drum that you want to be able to control in the mix. Usual go-to spot mics are the snare, and the kick drum. If you have the extra channels, just mic those normally. (If you used my measuring tape method on the Recorderman technique, flip the phase of the two mics when using a spot mic on the kick.)
This is a sample of the Glyn Johns technique that I did in a very low budget recording situation. I had 3 small cap condenser MXL 993's, which I summed into two channels with a mixer and recorded the output into Logic. I used a subkick mixed with a Beta 52 on the kick, and a 57 on the snare and ran those to Pro-Tools and synced the two programs to record the four channels, but for the purpose of showing this technique, I took off the spot mics, and you are only hearing the Glyn Johns Technique.
You've had this experience before. You've recorded some awesome tracks, and you're mixing, and it's sounding great. You've got the gated 40Hz tone on the kick drum and it's shaking your house to the ground. You bounce to disk, and put it into iTunes and it's super quiet compared to all the other music out there. Why?
The reason lies in compression of the overall mix. This is a dangerous subject. Before I go any further, let me say that loudness is a psychoacoustic phenomena that initially leads you to believe that a song sounds "better", but over a period of time, it becomes fatiguing to the ear, and that's probably why you don't listen to popular music on the radio for very long. If you take a popular song and turn it down to the loudness (unmeasurable and only perceived by the listener) to roughly the same as the mix that you have done, you'll notice that your mix is much more defined, and clear, and has much more impact. That's because it has more dynamic range. (I'm saying all this assuming your mix is a quality mix, which I'm sure it is.) Any compression to your mix will degrade the quality. Actually, any processing to the signal will degrade it, but sometimes these degradations are what we like.
Compression is a form of dynamic range reduction. You've probably acted is a form of compressor yourself, if you've ever turned down your volume knob when a song jumps into a loud section, or turned it up if you couldn't hear something clearly. A compressor works on a ratio basis. If the signal goes above a certain level, called the threshold, then the signal passing through will be reduced by the amount of the ratio applied. For example, if we have a compressor on a 2:1 ratio, then every 2 dB louder than the threshold will come out of the compressor as 1 dB. If it were 4 dB going in, you'll get 2 dB coming out. The compressors put on most pop/rock music today has a ratio of 8:1 or higher. That means as soon as you pass the threshold in amplitude, you have to pass it with 8 dB or more to get 1 dB of dynamic range, which isn't a lot.
Think of it like this; imagine a person whispering to you from across a quiet room, and then all of a sudden starts yelling at you in your face. You can imagine how much of an impact yelling in your face would suddenly be. Now imagine that when they're yelling, they aren't any louder than when they were whispering. Compression actually turns down the amplitude of the louder portions of the song, and then the whole level is brought up. So now the person is whispering as loud as they yell, which I've actually heard on a song before, so if you thought it was a ridiculous analogy, well, you're right. It's retarded.
I'm not saying that compression is a bad thing. I <3 compression. If you need to even out a sporadic drummer hitting a snare with uncontrolled attack, then a compressor can easily bring all those down to roughly the same amplitude. Heavy compression with high ratios on the entire mix is something to watch out for though. Like I said before, a high amount of compression will allow you to raise your levels to an unholy average level, but it's going to mess with people's ears, and it will be fatiguing to listen to. You'll keep turning it down, and it will still sound too loud. Have you ever heard Metallica's newest album? I think it flat out won the Loudness War, and no one else wants to compete with it, because that much compression just sounds like fecal matter being processed through a meat grinder.
If you use a compressor on your stereo bus for the output of your mix, please use it sparingly. People like dynamic range, and the more you compress, the less dynamic range you are giving someone. The "downside" to dynamic range is the apparent average loudness of the song. If you want your song to be louder, locate your volume knob and turn it clockwise until the desired amount of amplitude is reached. Seriously, stop being so lazy.
OMGZ it's taking over! Here I have taken a song and went all Metallica style on it. (The red portion is the overly compressed, and the dark blue portion is the normal uncompressed music.) You can see that the one guitar intro to the song in the over-compressed portion of the song is louder than the loudest part of the song. And then you have zero dynamic range when you get into the verse right before the loud portion. Now the chorus will have no impact. Don't do this. It's about as dumb as not having breaks on your bicycle.
Wow, so it's definitely 2am right now. That's usually not abnormal, but I had a midterm at 9am this morning, which means I've been up for about 18 hours. I'm just going to dive right in.
I've been talking about this microphone for a few weeks now. I finished it last month, and I haven't tested it on any real equipment yet, although it sounds fine through my Bheringer mixer into Logic via 1/8" stereo line input. So, audio engineers, I'm going to tell you how to build a microphone, with exception to the circuit, because I'm not about to explain electronics to you, and you're not about to suddenly understand it.
The microphone that I built was a Large Capsule Side Address Condenser microphone. Long name, but it's big enough to fit on the side. Basically, it looks like a Neumann U87. I fashioned the grill based on that microphone, so it looks quite similar. Before I go any further, I'd like to point out that I'm not an expert at this. This is the first time I've ever looked past the grill of a microphone. Hopefully you're in the same boat, so all this will be informative. Mics shouldn't be scary to understand.
Let's get some of the circuit design out of the way so we can get on to the fun building stuff. I used a condenser type circuit, which means that the microphone is powered by +48V Phantom Power supplied by almost any channel strip or little mixer ever. This means that the circuit actually amplifies the signal of the capsule, which which allows your mixing console to recognize the signal coming in. There's much more to that, but I'm just studying that now. It's not necessary to know it when building your first microphone for fun.
The body of my mic is made out of 2" brass tubing, or kitchen railing. It was easy to cut, and easy to find the bottom of the microphone, which is a railing end cap. I drilled a hole in the end cap to fit the XLR connector through, and screwed that on. On the inside of the end cap, I attached a metal rod that angled straight up. When the end cap was fitted to the brass tube, the rod would go through the tube and end up about 2" short of reaching the end of the tube. Then I soldered a round plate 2" in diameter to the top of the rod, perpendicular, so parallel to the end cap. To this, I screwed on a small flat metal strip, which was bent at a 90 degree angle to continue upward. To this I screwed on a small flat metal strip that was bent into a circular shape, which held the capsule in place.
The grill was probably the most fun. I had to hand bend the brass mesh, as well as roll it on counters, chairs, thick pens, or anything I could find that was the right shape. The right shape was somewhat difficult. To copy the U87, the grill had to come out of a round mic body, and then flatten out into more of a rectangular shape at the top. I took a thicker metal strip and bent it around the top to enforce the rectangular shape, and soldered it to the mesh from the inside. That was difficult, because my soldering iron is weak sauce.
From there I got some black fabric at Michaels, and covered the inside of the grill, apart from a large hole for the capsule. I didn't do this for any other reason than look, and to be honest, it looks awesome. Other than that, I had to screw the end cap to the tube, and that was probably the hardest part, because you have to tap the end cap, and also countersink the screws into a really thin tube. So, of course, I only have one screw instead of the planned two, because you really can't tap with brass, and so now part of that screw is still stuck in there. I just about threw the whole thing across the garage.
Here is the mic, strapped onto a tripod with a velcro strip. Very ghetto, but I just ordered a shock-mount yesterday, so it should look a little more professional after that.
I tried it on several instruments, and I concluded, through the gross little set-up I had it running through as described earlier, it sounds best on the cello. The capsule has a slight raise in the frequency spectrum around 5-10KHz, and it has a good low frequency response, so it picked up the fundamentals of the cello as well as the friction caused by the bow.
Overall, this mic sounds "OK". That's my official rating until further testing. I'm not going to be a fool and believe everything I make sounds amazing. I'm comparing this against the best microphones on the market. It fairs ok, to say the least, and I'm very pleased with that, for not having a clue what I'm doing. Seriously.
I'm already planning on the SX-II, this being the SX-I. (No, that doesn't mean Sony X-plode.) The SX-II is going to be a phantom powered tube microphone, so it won't need an external power supply. I'm working on the schematic now, and it's coming along quite nicely. As far as look, it's going to be a combination of the Neumann M149 and the Blue Woodpecker. This microphone I will know what I'm doing. Since the SX-I, I've been studying microphone design and condenser microphone circuits.
So, folks, I venture on, preparing myself into a weapon of knowledge against the vast darkness of the unknown.