Shifter Kart FX Recording

Exactly a week ago today, I had that nervous sense of anticipation when you have a major record session happening that day. And at times like that I remember the words of some forgotten performer who explained that those butterflies in your stomach are important, because they keep you on edge & slightly worried so that you are fully prepared, double-check everything & make sure you can give it your best shot. Thanks butterflies!
So the reason for this kart recording session was primarily because the previous kart I recorded was too low revving; it was a 250 and the one I was now set up to record at the Mt Wellington track was a 125 that can rev past 12,000rpm! And it has a wild expansion chamber on the exhaust… so YES!!! its pretty damn LOUD!!! Spot the good Dad in this photo:

loud!

The previous Kart session wasn’t a total write off – I got some useable material, but in hind sight I realised the main benefit was experience. I doubt I would have been half as prepared nor got such great clean recordings from this session if I hadn’t already tried once before. So maybe thats a moral of vehicle recording; if the vehicle plays a prominent role in the film make sure you can have multiple access to it. Even if the session goes perfectly, when you are back in the studio cutting the material, you may discover you need to do a quick revisit to pick up a few specific extra sounds…

So the most difficult aspect on the first recording session was rigging the mics; when you see how small & low to the ground these karts are you realise two things: firstly there isn’t a lot of room for bulky gear, and secondly the engine, chain, wheel etc are all VERY close to your mics & cables – if something were to come loose eg a cable to get tangled in the axle, the results could be very dangerous to the driver…

loud!

So first I set about mounting the mics – on the last record session I got a lot of low end vibration which at times overloaded the mics, so this time we used a small piece of high density foam, and gaffer taped the mic (which was wrapped in polar fleece for wind protection) to the top of the radiator. I wanted to use two mics for a couple of reasons: first is paranoia – if one of the mics distorts then maybe the second mic will be ok… the other is for variation, so even though both mics are close to a very loud sound generator we mounted the other mic on the back of the seat & gaffer taped it to radiator hose. Obviously all of this was done with help & advice from the drivers eg how hot that does that radiator hose get?

setup!

I bought a bag with me to put the recorder in, but also to contain any spare cable – ideally I needed some very short mic cables eg 1m, but all of mine are more like 4m so I knew I’d need to route the cables, gaffer them in place & then safely wind them up & secure the spare cable beside the recorder. You can see the bag lieing open in front of the radiator in the photo below.

setup!

Now a word about the recorder – you might think I’m nuts but I decided to use a DAT machine as the onboard recorder. I have a few good reasons, firstly because it worked well in the past – we used the same DAT machine to record the onboard sounds for Burt Munros V Twin Indian and got great results, and as this session was critical (& expensive to repeat) I did not want to be experimenting. I also know a friend had a bad experience using a hard disk recorder when recording onboard Formula 1 sounds – the G Forces & vibrations caused the hard drive to produce errors & stop recording. I understand the solution to this problem is to transfer the OS onto the CF flash card & disable the hard drive, so recording to the CF card too… I will give this a try when I have spare time to experiment eg on my own car or something, but I wasn’t game on this session. I also wanted to use my Sound Devices 722 to record exterior moves at the same time as the onboard recording, so DAT it was! The DAT machine I have (a Tascam DAP1) has built in switchable -20dB pads which I used from the start as those dynamic mics produce a hot signal which will distort the mic preamps, even with the input gains turned down. A sidenote: you can see distortion in the meters – on the first kart recording, I did a first run without the pads in, but with the input gain turned down so the level was peaking at -12dB or so… As soon as I stopped him to check the recording, I rewound & hit play and before I even listened I could see the meters went rapidly up to -12 and then had practically no dynamics or movement in the meters. It was like they were smacking into a brickwall limiter and thats exactly what was happening, but it was happening BEFORE it got to the recorder side of things. After turning on the -20dB pads & turning up the input gain to compensate the levels similarly went up to -10 or so, but there was dynamics & movement in the meters. Experienced soundies will already know all of this but for everyone else, be very aware that loud sounds can distort the mic preamps BEFORE they become a digital signal. So while your meters are nowhere near clipping, you may well just be cleanly recording an already distorted signal. Accordingly every record kit should contain some inline pads!
Heres a photo of both mics rigged & ready to go:

both mics

So……. what’s it sound like? Well small high revving motors like these need to be warmed up, so there is a ritual of starting them while they are on their stands & then blipping the throttle for a while. Along with warming up the motor this also gave me a chance to check levels etc… I recorded this on both the onboard DAT and my 722 with Sanken CSS5 mic, so I’ve synced up the recordings & I switch mics on the video so you can hear the difference in tonality. There are also some shots from on the track, where I repeat the footage switching mics each time (please excuse the shaky cam – its hard recording sound & shooting video at the same time!) I’ve also added captions identifying what mics you are hearing – Onboard Mic 1 is an EV RE27, I need to check what Mic 2 is… Last time I used an AKG D112 but it really captured too much bottom end (which is what it is designed for)

 

Obviously when we premix these scenes the dubbing mixer will EQ and compress the onboard mics… And I have another whole stem of FX dedicated to onboard tyres, movement, vibration etc… Serious fun! Next week we are doing Ambience & then Foley predubs, so it will be mid the week after before we crank up the Kart FX in Theatre 2 at Park Road Post – I can’t wait!!!

 

PRP mix

ps I’d really appreciate hearing about others experiences with onboard recording in similarly tricky situations – I wish I could find that article about people recording F1, I’m pretty sure it was in an old Mix magazine…. A solidstate recorder would be the ideal…

ps if you are into gaming, check this video

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