Flying mics and ominous cymbals

I recently read an article on the flying mic technique – not sure where, may have been TapeOp – but being a fan of the more esoteric side of recording, I thought I have to try that out.

The idea is simple, you suspend a mic from a pulley via a length of string which allows you to smoothly raise and lower the microphone. You then record a source and vary the mic position as the source sound decays, allowing you to pick up more of the detail in the decay of the sound.

This technique is particularly interesting with cymbals. If you have the mic too close, the initial attack will likely overload it so you won’t capture the detail in the moments immediately after the transient, but with the mic far away you can’t readily pick up the fine details of the decaying sound. And it’s in that decaying sound that a lot of the interest lies; cymbals produce lots of non-harmonic tones, i.e. frequencies not related to each other nor a fundamental pitch by integer multiples as we find with strings or pipes.

I set up a mic stand over my ride cymbal and improvised a makeshift axle from the clamp for a reflection filter, this would function as a pulley and allow a length of string to travel freely over it and up and down over the cymbal. For the microphone I chose my trusty Oktava MK-012  (modified by Micheal Joly) with an omni-pattern capsule so that I could get really close into the cymbal without the proximity effect. I tied the mic to one end of the string and made sure there was enough free XLR cable to allow the mic to travel freely up and down.  With the other end of the string in my left hand and a drum stick in my right, I practiced striking the cymbal whilst simultaneously lowering the mic. It took a few goes to get the timing right but eventually I could ride the mic in just after the initial hit and get it very close to the cymbal surface for the decay.

I also experimented with moving the mic around the cymbal surface to capture different harmonics. Monitoring on headphones also allowed me to get the movement right in terms of riding the volume.

So here are some results:

I think there’s some great scope for sound effects and soundscapes using these. With that in mind, here are a pair of hits reversed, hard panned and with an added splash of reverb to create an eerie, ‘something bad is about to happen’ kind of sound:

Happy experimenting…..

 

DIY Sub Kick

The concept of a sub kick is very simple, take a large speaker and use it in reverse as a microphone specifically for picking up low frequency information, from a kick drum for instance. This can be used in the mix to reinforce the sound of the kick alongside another kick drum mic,  providing additional depth to the sound due to it’s focus on the sub 100Hz frequency range. The subkick won’t pick up much spill from other parts of the kit either, and a good trick is to use it to trigger a gate on the internal kick drum mic, to get a very tight and clean kick sound.

Various companies make them, the  Yamaha SKRM100 for example, which is essentially a 6.5″ woofer mounted in a small drum shell, with mesh either side and a built in stand. The price, £350, quite a bit for speaker on a stand! Over the years I’ve seen various DIY versions in studios around the way including an NS10 woofer clamped into an old worktop vice as a base, all these incarnations functioned well, and cost significantly less than £350 to make. Time to get the tools out I thought.

This is an easy DIY project, it involves mounting a woofer speaker into a suitable frame (in this case a tambourine shell), and then a little soldering to attach an attenuator and a male XLR connector.

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First start with a speaker, I went for an 8″ Wharfedale woofer of EBAY (approx £18), you can use anything from 6″ up, though some say it doesn’t work as well with larger speakers. I’m not sure about that, the 8″ seems to work pretty well. Most important is the speakers frequency response, it should go down to about 20Hz to get all those sub bass frequencies.

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I thought a lot about how to mount it, I wanted something that would isolate it and look good, but not cost too much. The cheapest and most elegant solution I could think of was to use elastic hairbands to suspend the speaker within the circular frame of a tambourine (without the jingles of course). So I ordered a 10″ tambourine (£7 Ebay) and removed the jingles by pulling out the nails holding them in place.

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Slip the elastic hairbands through the screw holes in the speaker, then feed each end through one of the slots in the tambourine rim and push the upper loop (the one that goes over the rim) round and under so the 2 loop ends overlap. Take the nail that used to hold the jingles in place, push it back through it’s location hole so that it pegs the 2 loop ends of the elastic in place. Push all the way in so it’s secure. That was probably the trickiest step in all of this, required a lot of patience to get the elastic and the nail to all go in the right place. Repeat this for the remaining screw holes.

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The next challenge was figuring out how to mount the the subkick using a normal mic stand. I happened to have a broken mic stand lying around so I took the pivot mount from it (the bit that screws onto the top of the vertical part of the stand and allows the boom to attach to it and swivel up and down). The advantage of using this was that it had a standard screw thread on the end which meant I could attach it to a regular mic stand (as shown in the picture above). The pivot mount itself attached to the tambourine rim with a nut, bolt and a couple of washers (through one of the existing slots in the tambourine).

Next step is connecting it up to a mic pre-amp. The output of the subkick is pretty hot, an attenuator (or pad) is recommended to bring the signal level down to the region expected by most pre-amps. You can buy an inline attenuator that connects between the subkick and the XLR cable to the pre-amp, or you can knock together a basic potential divider circuit to do the job for you. I opted for the latter as you probably guessed. Another point worth mentioning here is that I’m going to use an unbalanced connection, providing the environment isn’t to (electrically) noisy and cable runs are short, this shouldn’t be an issue. If you wanted to go for a balanced connection, you would need to wire in an audio transformer, and to get one that has good sub-sonic frequency response isn’t going to be cheap. You could also use a DI box, again, a good quality one with good bass response would be preferable.

Circuit 1

The schematic for an attenuator circuit is shown above, I used a simple potential divider, the values I chose for the resistors R1 and R2 are:

R1=680 Ohm , R2 =150 Ohm

There are many combinations you could use and they also depend on your speaker, Google “attenuator for Subkick” if you want to get lost in that world!

 

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With the resistor values chosen, I soldered them directly to the speaker terminals and covered them with heat shrink. Easiest way I found was to solder one end of R2 to the speaker – terminal, and one end of R1 to the speaker + terminal, slide a sheath of heat shrink over each resistor then twist the exposed ends together, before applying heat to shrink the insulation (see above).

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I then soldered a short length of guitar cable to the speaker – terminal and the exposed resistor ends, ensuring I had a sleeve of heat shrink in place to insulate the connection.

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Finally I soldered the male XLR connector onto the end of the cable, (Pin 1 to Speaker -, Pin 3 to the resistors, Pin 2 unconnected). I had a retaining clip lying around so I used that to secure the connector to the frame, so as not to put too much mechanical load on the soldered joints.

So there you have it, a fully functioning subkick that doesn’t cost an arm and a leg, doesn’t look to shabby, and is not to difficult.

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Here is a quick audio example of the subkick in action. The audio is as follows

Bars 1-2 : Internal kick mic only

Bars 3-4 : Subkick only

Bars 5-6 : Internal mic + Subkick

Bars 7-8 : Internal mic + Subkick (with gate on subkick)

Bars 9-10 : Full kit, no subkick

Bars 11 – end : Full kit with Subkick

https://wijproductions.files.wordpress.com/2014/10/example-subkick.mp3

Zen and the Art Of Microphone Modification

 

 

 

After much standing on the side procrastinating, reading various websites, blogs and how-to guides, I decided to get my hands dirty and take on a microphone modification. I had recently bought an Apex 460 valve mic from the states, and an upgrade kit from the very helpful people at Microphone-parts.com. The kit comprises everything you need to convert the stock Apex 460 into a very nice sounding mic. The stock mic sound is nothing special, but it’s only when I did a comparison with the modified version did I realise how big a difference the mod really makes.

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Basically, the modification involves changing the tube to a better quality, lower noise one, removing the RF filter circuit, swapping critical capacitors, diodes and resistors with higher quality components, and changing the capsule for a better quality version.

I spent the best part of a day doing this, but I was going slowly because it was

a) My first time, particularly doing desoldering work

b) I was ultra paranoid about wrecking the mic

Here’s what I got, where I got it and how much it cost:

– APEX 460 Tube mic from Ebay (MegaToneMusic) Total cost including shipping to UK and customs = £205

– Apex 460 mod kit (The Fox SG version from Microphone-Parts.com), approx £140

– Thermostatically controlled soldering iron and desoldering pump – Ebay – £15.99

– Desoldering Braid – Ebay – £3.49

– Helping Hand crocodile clip and magnifying glass (for holding PCBs whilst soldering) – Ebay – £2.88

– 4% silver solder (1m) for audio connections – Ebay – £1.99

– 99.9% Isopropyl alcohol – Ebay – £3.95

These items I already had lying around:

– A clean toothbrush and some cotton buds

– regular solder for de-soldering

– wire cutters, screwdrivers

– clean containers for storage

So you can see that it’s actually quite cheap (compared to spending several hundreds of pounds on a valve mic). I’m not a particularly experienced solderer, I know how to do it and have done the odd repair job, but nothing major, and I’ve never desoldered and replaced components on a board before. I found the overall process of moderate difficulty, once I got the hang of desoldering it was actually quite quick. The kit recommends using the vacuum pump to desolder, but I also ended up using the braid in some places because it was easier and cleaner.

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The first task is to swap out a pair of diodes in the power supply, this is fairly straightforward and a good way of easing yourself into the job, you have to make sure the power supply has been disconnected from the mains for at least 1 hour so all the caps have fully discharged and you avoid the risk of electric shock. Once this swap is done, fire up the mic and check all is ok, then it’s time to work on the mic itself.

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Opening up the mic, firstly you remove the old tube, which is held in place by a spring loaded pad at the bottom, once done you can unscrew the 2 PCBs from the frame, desolder the capsule wires and open up the 2 PCBs to access the joints on the underside. The very detailed and comprehensive instructions tell you exactly which components to desolder. A useful tip here is to always bring the soldering iron in from the edge of the board, to avoid burning any wires or components on it by accident (as I did!). The “helping Hand” tool was also quite useful here, allowing me to hold the PCBs at the best angles to facilitate access to the joints.

Once the necessary components had been removed, it’s time to repopulate the board with the new components (taking care to observe correct polarity for certain capacitors). The FOX SG kit comes with a bit of 4% silver solder (audiophile grade apparently), however I bought a meter of the stuff off Ebay, probably my soldering but I ran out of the stuff they provided before the last component was done. Once the components are in, time to clean the boards with the alcohol to remove flux and other contaminants (taking care not to get any on the polystyrene capacitors).

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At this stage, they recommend testing the mic, probably wise, so put the new tube in, reconnect the capsule wires and plug in. Providing this goes successfully it is then time to remove the headbasket and swap the capsule. This was the bit I found most fiddly, probably because I was so paranoid of touching or damaging the new diaphragm that I ended up being over cautious. Suffice to say, it was actually quite straightforward in the end, and the new capsule was on in no time at all. The wires onto the PCB need to be trimmed as short as possible to reduce capacitance, but be careful here, I cut mine a little too short and had real trouble accessing the joints to reattach them.After a final clean and inspection it was time to reassemble and test.

Initial results were very encouraging, on vocals the mic sounded big, warm and deep, listening to the pre-mod version it sounded thin and harsh, this new mic is very smooth indeed, looking forward to putting it too work in the coming days. I did a quick comparison with a few other mics to get an idea of how it sounds:

I had been lent a Sontronics Aria for a few days to play with, which was perfect timing as it gave me a high quality reference to compare with. Although the Aria ultimately performs better (slightly quieter and smoother), it is over twice the price and the 460 holds it’s own very well.

As a final mod, I decided to remove 2 of the 3 layers in the headbasket, this took a bit of patience and fiddling with a pair of pliers to get them both out, I found using a sharp pointed object to prise up some of the mesh before getting stuck in with the pliers worked best.

So there you have it, if you are thinking about doing this and are reasonably handy with a soldering iron then I would thoroughly recommend it, the mic is quite easy to work with and the upgrade kit is great, well documented and the choice of components really makes a massive difference. I’ll be doing this again I think!