I have some free time. Sometimes I make recordings of trombone quartet concerts or of myself playing, and I’m aware that I don’t know much about positioning microphones, except that it makes a huge difference to the sound.

I went to a local church for an hour and played around a bit.

What I learned:

• It’s not surprising that I can’t get a good sound in my study – you need 3m at least
• As expected: on-axis (pointing straight at the bell from in front) is harsh, trebly, and you hear all the breathy fuzziness.
• 90 degrees off-axis (pointing at the bell but from the side) is too muffled, lacks life, a bit thin – but at least there isn’t all the breathiness.
• My favourite sound was from a pair of omnis (and a Jecklin disk) about 7m away, and 60 degrees off-axis. This of course depends on having a beautiful room.
• I play very differently in a lovely, big church. It’s wonderful to enjoy the sound!

Detail, and some clips

Angle

I placed three identical (SE8 cardioid) mics 3m from the bell, at 90º, 60º and 30º off-axis. (None directly in front of the bell). This is three simultaneous recordings of the same event.

If the difference isn’t clear … then (a) this article isn’t for you, and (b) this should make it clearer:

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Distance

Simultaneously I had another cardioid SE8 at 30º and 7m away. Moving further away seems to make the sound a bit “fuller” – maybe because there’s a lot more “room” relative to the direct signal.

This is 3m and 7m at 30º:

For interest, the loop of 3 mics from earlier, now with the fourth, more distant one at the end:

Finally: Jecklin pair

This is (obvs) a stereo signal and the others are mono. Here’s the pair at 7m and on-axis. It’s quite harsh, and it’s the reason you shouldn’t play brass instruments at people!

Here’s 7m and 60º off-axis. It’s a different performance because I only have one Jecklin pair. Much less aggressive. I think maybe 45º might be a good compromise.

Conclusion?

There’s so much more playing around to be done here, and I’m not sure I want to spend the time, but it turns out that the most pleasing configuration that I tried on this one-hour session was a pair of SE8 omnis separated by a Jecklin disk, at 7m and 60º off-axis.

I have no idea whether the JD made any difference.

The Result

Well: I played a sonata twice: with the Jecklin pair at different positions, and I much preferred the sound of the second. Unfortunately I didn’t press “record” on the video camera the second time (and the phone camera that I had set up had gradually slipped, so it just recorded the organ pipes above me). So, here’s the first session. I took the nicest of the mono signals (haha: an AKG 414B-XLS in hypercardiod mode, co-located at 7m and 30º) … and shoved it through a Lexicon reverb, to give it a bit of stereo! Sounds pretty similar to my “favourite” configuration, above but lacks a bit of life.

Further work

With the off-axis thing, it’s tempting to think that the difference is spectrum occupancy (filtering), in which case it could be equalised using … equalisation. I have yet to try this.

Jecklin vs omni pair? … or cardioid pair?

I’ve had mixed experience with digital reverb. If the source is completely clean (e.g. close-mic @ 0.1m) it works well but IMHO doesn’t reproduce the sound in a real room.