ReaktoLite

Welcome to Reaktolite, I'm a Sound Engineering student at UWL in London.  This Blog charts the projects and other stuff I am working on.

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And recorded with only the SM58.

Can you tell the difference?

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This is the drum track with the sub-kick included.

The sound immediately feels much bigger with a bit more phatness to it.

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More tests.

This one shows the spectrographs for the SM58 (top) and the sub-kick (bottom), this time with the back panel removed.

The peak frequencies are highlighted in red, and again this show sthe sub-kick picking up frequencies more strongly in low frequency ranges.

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It sounds like...

The sub-kick has made a difference, although with the back on the sound is a bit boxy, much like you would expect from a small speaker. 

The next test will try a recording with the back off.

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Ans this is the same track with the sub kick taken out.

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If you have some good headphones or decent monitors get them.

This is the first test recorded using the sub-kick.  Sadly the first thing I hear is the terrible kick drum, but the sound is otherwise pretty good.

Listen to this then listen to the next track with the sub-kick taken out.

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So some test data.  The first spectrograph is the recording of a single kick with the SM58, the second the same kick with the Sub-Kick.

Straight away it is clear that the Sub-Kick has captured much more low frequency audio than the SM58. 

This first test was carried out with the back of the device in place.  The later tests will be with it off.

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The final tests

Finally got into a studio with a couple of days to spare and do some test recordings with the Sub-Kick.  The setup used was the device and an SM58 on the kick, to maintain consistency with the original tests done.  To make a nice drum recording I added a pair of AKG C414′s as overheads.  No processing has been used and a couple of demo tracks will be posted later.

The setup was not the same kit as in the original tests, the intention being to try and see the difference in captured audio from one drum to another.

This was not without problems.  The original kit used was very good, the drums in great condition.  The kick drum in the studio however was pretty shoddy.  The skin was flappy and no amount of tuning would make it sound any better.  For now the test had to be carried out with that kit, but in future a decent kit would be better.

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Transducer Selection

Which one and why?

After the initial testing, I chose to use the Mordaunt Short MS-20 driver. This was for a number of reasons.  First, the 15″ driver was clearly an impractical choice, much too heavy and making it into something usable would have meant producing something the size of a guitar amp.  In a live situation this really wouldn’t be much use.  In testing the two 8″ drivers gave the best performance in the desired frequency range.  While the Tannoy, to my ear, lacked some low end punch. 

Between the two 8″ drivers, there was clearly a broader frequency response from the MS-20 and this driver also produced better low frequency performance. 

So the choice was fairly easy I guess...

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And this is the built product ready for testing.

Just need to find a drummer!

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Needed a stand.  Started with a busted old microphone stand and modified it, with my angle grinder skills, to fit into the drum mount on the side of the tom shell.

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The back panel, which is intended to be adjustable/removable for the tests is made from 12mm MDF and has some egg profile foam glued to the inside.  This has the double effect of providing some damping of high frequencies inside the enclosure as well as forming a seal around the edge.

The wooden rectangles are offset to form expanding wedges inside the drum shell.  This provide sufficient seal at the back to hold it in place while testing.

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Wanted to use metal grille, but couldn’t find any.  So what I have done is cut a circle inside the drum skin, leaving 30mm around the edge to maintain the structure of the skin which will allow use of the drum ring to hold the front into place. 

Have slightly roughly sewn in some speaker cloth, my needlework skills are not as good as my skills with say, an angle grinder.  When inplace in the drum ring this looks pretty nice.

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Working on the front. the white stuff is vibration proof adhesive acting as a sealant around the O ring mounted for the transducer.  Placed on top of that, but not glued into place, is some simple foam intended to absorb high frequency reflections from around the transducer.

The transducer is mounted with a simple foam gasket behind to reduce acoustic leakage around the basket frame.

Next is to figure out a way to convert the drum skin into a nice front grille.

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And this is what it will look like from the outside when everything is secured in place after the final tests.

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All that algebra pays poff in the end though.  Have tested the output from the pads and am getting a pretty reliable -10dB and -20dB attenuation.  Not loving working with this really fine microphone wire though, it keeps breaking!

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All that time at school when you thought, when the hell will I ever use algebra?  Turns out it is pretty much all the time for me right now!