Recording The Horn Section
The latest instalment deals with the recording of the horn section.
In rock and pop music, a horn section usually consists of trumpets, trombones and saxophones. Using Microphones this month deals with how to pick them up. At the end of this instalment we will also look at the ubiquitous problem of correct XLR wiring for connecting balanced and unbalanced lines.
The trumpet delivers frequencies of 160Hz to about 10kHz, and the treble is dispersed over a pretty narrow angle from the bell. Listen to a trumpet player playing sufficiently loud (that's when the trumpet sound gets that 'bite' so popular in pop and rock) and you get a feel for the highly directional radiation and also for the loudness that will be produced in front of the bell. For SPL (sound pressure levels) figures see Figure 1.
To avoid overload problems in the mic it's therefore best to aim the trumpet slightly to one side of the mic, not blowing directly into it. But getting too far away from the trumpet's narrow radiation angle means loss of treble frequencies. Figure 2 gives an idea of a good compromise.
For trumpet and trombone pick up a windshield should always be used. Even when using mics with an integrated windshield (vocal mics) for this application, an additional external windshield might be useful.
For recording the trombone, it's much the same as for the trumpet. Its frequency range is 80Hz to about 10kHz. Those high overtones that appear when playing 'forte' and make for the characteristic 'dirty' bone-sound, are radiated over a narrow angle. And SPLs achieved when playing loud high notes may be quite enormous as well.
Because of its rather limited bass range, a bass cut may be employed with trumpet and trombone microphones to reduce leakage, rumble, and pumping effects of compander systems etc.
There is one exception, though: if the trombone is going to play some kind of bass phrases or pedal notes (Bb1 down to maybe G1), which corresponds to frequencies down to about 50Hz. A bit unusual in mainstream rock trombone playing, but often heard as an effect.
Placement in the home recording studio of both trumpet and trombone players must take care of the high directionality of these horns. If your recording room's walls are too reflective, the sound may echo back to the player, giving a really unpleasant feeling. The use of thick damping material eats up the treble, producing a muddy sound. A good solution is some contraption that reflects sound in many different directions - it makes the room sound acoustically bigger. The cheapest approach is to use egg containers.
If condenser mics are used with trumpets or trombones, the high sound pressure levels call for types with sound attenuation facilities. As mentioned earlier in this column, condenser capsules tend to accept high SPLs, but their integrated preamp won't. So some attenuation must be applied in between. Attenuation pads bring down sensitivity and increase headroom (up to 20dB). Popular types in many recording studios include AKG C460, C414, Neumann U87.
Dynamic types won't present overload problems. Of course, all the attack transients may lose some of the 'edge' due to the dynamics' more 'sluggish' transient response - and brass players spend hours working their tongues for good 'attack'. Very often, mics with no or little proximity effect are used to allow for different mic distances without bass pick-up change eg. E-V RE20, AKG 222 or 202, Sennheiser MD441. Vocal mics will also work fine.
Small condensers (Countryman, AKG C567, or the like) will make trombone players especially happy (no more mic stand to hit with the slide, as they can be attached to the rim of the bell). However, overload will be a problem and I feel it's more of a device for stage use.
Many sound engineers prefer ribbon mics for horns. They feature excellent transient response combined with good performance at high SPLs. Ribbons were popular in the early days of mic technology; the RCA 44 and 77 are still used in many studios as the number one choice for brass. Nowadays, fine ribbon mics are manufactured eg. by Beyer (M260, M500...)
Of the large family of saxophones, the alto and tenor are the most popular in rock, both for solo and ensemble work. Frequency range covers 200 Hz to over 12 kHz, the high end consisting to a great extent of breath noise. Sound is radiated from the bell and microphone positioning depends on how much key click, breath noise or 'pure' sound should be captured.
Pointing the mic between keys and bell gives a warm sound with some key click, which gives an intimate touch to the sound (see Figure 4). Placing the mic nearly inside the bell produces a rather harsh sound when the sax is played loudly, but it will pick up lots of breath sound and it's best for 'sub tone' style (the kind of sound you associate with strip joints, jazz ballads and other dirty stuff).
Mics commonly used for sax pick up include: AKG C414, Shure SM58, Sennheiser MD441, Beyer M88 and M260. Vocal mics are fine too.
The usual horn section in the pop and rock idiom consists of a trumpet on top, one or two saxophones (alto or tenor), and maybe a trombone which mellows the sound a bit. Record them standing (or sitting, which is worse to me) side by side, in a straight line or in a semi-circle. You may use an omnidirectional microphone (one that picks up sound equally from all directions) placed in the centre for all of them, either going for this microphone's pure acoustic mix of the section, or as an addition to the individual mics.
A word of warning to the young, aspiring home studio owner, who is dealing for the first time with brass players: have your recording gear ready from the start. Some players are pretty reluctant to redo a difficult and exhausting high note part just because of a technical fault. To some degree, this is understandable to me. I personally know a guy who suffered from labial (lip) paralysis after being pushed to play lead trombone in a very long rehearsal!
Last month I mentioned problems that may occur through the use of different XLR wiring schemes by some manufacturers. You may run into trouble when connecting balanced and unbalanced (single-ended) gear.
A balanced signal always needs a 3-pin connector, where one pin is ground (earth), the other two audio (in-phase and out-of-phase). When going unbalanced (only one 'hot' pin and ground), one of the two audio pins must be grounded. It is always the out-of-phase pin that must be bridged (strapped) to ground.
As long as XLR connectors are used for balanced and jack plugs for unbalanced connections, everything will work fine. Unfortunately, some manufacturers use XLR plugs for unbalanced inputs and outputs.
Now, if this unbalanced XLR connector has pin 2 grounded, for example, and the connecting cable has pin 3, both pins are shorted to ground and there is no signal at all. (See Figure 5).
What to do? Stick to one XLR wiring convention, measure XLR connectors of newly acquired units for ground bridges and, if necessary, rewire them.