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

Recording a 9-piece latin band (in layers) – Timbaterra Salsa EP

This recording of the Bristol-based latin band Timbaterra comprises 4 tracks covering Reggaeton, Salsa Romantica and modern salsa styles with influences from Cuban Timba. Recorded in Bristol and featuring vocals of Indira Roman and Sandra Lord, and the piano and vocals of Raimundo “El Nene” Fernandes. Rhythm section features Rory Francis playing all percussion, myself on bass and the horns were played by Ralph Tong (Trumpet) and Dave Smallwood (Trumbone).

The aim of this recording was to get the full sound of a 9 piece latin band, but doing it in layers rather than everyone playing together live. The key to this is having a good, grooving rhythm section  foundation to build the rest of the tracks on.  Thus we first layed down bass, piano and percussion together, the percussion was done timbales first to get all the breaks marked out, then we overlaid the congas, bongos, guiro and cowbell. I borrowed a set of Audix drum mics for the percussion, mic’ing the timbales with a pair of overheads and 1 dynamic under each drum, then individual mics on the snare, kick and bell tree.

Vocals were done next, fantastic performances from everyone made this very quick and easy. I used an Electrovoice RE20 for all the lead and layered background vocals, worked very well on these voices.

Finally the horns were done, we couldn’t get both players in at the same time so had to go with layering each part individually. This makes things a bit more tricky in the mix when it comes to making it sound like a section, but not impossible. Again, the RE20 microphone did the job of tracing the horns, I used it about a metre away and it seemed to capture the tone nicely.

Once recorded, the mixing began in earnest. Although I’d played in latin bands for years, I’d never recorded and mixed latin music, the learning curve was steep! Thankfully Raimundo was there to bounce the mixes off, he patiently listened to a lot of iterations before he finally said, “yes, that’s it!”.

In a nutshell, the cowbell needs to be prominent (but obviously not too prominent, unlike here), the congas driving and the rest balanced. Obvious right? Took me a while to get it though. A lot of work went into gelling the horns together to sound like a section rather than individuals playing in separate sessions. I used sample replacement to reinforce the kick and snare drum sounds too, adding more punch than was available in the original recorded sounds.

I also go the opportunity to trial a Universal Audio Apollo system, and used the UAD analogue emulation plugins to mix the songs with. Specifically, I used the Studer A800 tape sims on each instrument bus, the EMT 140 plate reverb as a general reverb, the Neve 88RS channel strips for the percussion, Cambridge EQ and LA-2A and 1176LN compressors for vocals and horns. The overall effect was amazing, I got closer to that sound I was searching for than I ever managed with all the other plugins I’d been using. So blown away was I that I decided to invest and bought an Apollo and a bunch of plugs, haven’t regretted that decision!

I’ve been studying Mastering courtesy of Ian Shepards Home Mastering Masterclass (which I thoroughly recommend by the way), I thought I’d put some of that knowledge to the test and do my own masters on these tracks too. Still learning on that front, there is a lot information to absorb and experience to gain. During the mix process the band had a regular gig at a salsa club, so we had opportunity to test out the mixes on a larger sound system and get an idea of how people responded (they danced!)

All in all I’m very happy with the way this recording came out, it took a while but I had a lot to learn, I’m  looking forward to doing a lot more latin music in the future.