Sydney Recording Studios recording a Leslie Cabinet.
There are many different methods for recording a Leslie cabinet, and these methods can vary across Sydney recording studios. This post is about how we do it at Crash Symphony Productions.
Firstly, what is a Leslie Cabinet?
The Leslie Cabinet (or Leslie Speaker) is a loudspeaker and amplifier, most often associated with the amplification of the Hammond organ. It utilises reproduction of the Doppler effect to create its unique sound. By rotating the sound waves, amplification of the instrument is possible.
The Leslie Cabinet, which is what is miked up in the recording studio, contains the treble and bass speakers. Most Leslie Cabinets are divided up into three different sections. The top contains the two treble horns that rotate on a mechanical arm. The middle section has the loudspeakers and mechanics responsible for horn rotation. The bottom section contains the bass-rotating woofer. In terms of microphone placement, the top and bottom sections are what emanate the sound desirable for music recording.
The microphone placement method described below is really effective and gives a sense of stereo presence to the sound, so that what is used in Sydney recording studios. For those who get to place microphones on such an interesting cabinet regularly, this will be of particular interest to you.
Firstly, we need to have a better understanding of how the Leslie Cabinet works. Inside the upper section, there are two horns that rotate on an arm. Both horns are diametrically opposite to each other and the sound is directed radially outward from the centre of rotation. In other words, at any one point in time, the sound emanating from the horns are in opposite directions from each other. We can control the way we hear each horn through each individual speaker with the placement of two microphones. One like the AKG 414 large diaphragm condenser microphone is a good choice. This is because it gives a clear signal, has a variable volume pad switch (which is necessary for a loud Leslie Cabinet), and has a bass roll-off and multiple polar patterns.
To create separation from the bottom bass signal, it is worth experimenting with the roll-off to minimise undesirable frequency crossover between the treble and bass sections. Start with 80Hz roll-off and have a listen to whether a higher setting helps the recording, or starts to make it sound too thin.
In terms of the polar setting on the AKG 414, it is recommended to use the figure-of-eight setting, as this will reject any incoming signal from the side of the microphone. This is important for maximising separation between the left and the right speakers in the control room and, ultimately, will give the listener a more enjoyable stereo experience.
To start with, you’re going to need two channels set up for each AKG 414. Make sure that they are panned opposite to each other; one to the left and one to the right. You’ll also need a channel for the bass microphone.
When one microphone is placed in the front of the cabinet and one in the back, each horn reaches a microphone at the same time. Remember that the horns are diametrically opposite in position due to their construction. Therefore, when we listen to the signal that is coming through the left and the right speaker, we will hear them pulsing at the same time.
Alternatively, if we place one microphone in front of the cabinet and one to the side (left or right), then at no time will the horns be hitting the microphones at the same time. In fact, one horn will pass one microphone position before moving to the next on the side of the cabinet. The horn on the other end of the arm will follow the same trajectory shortly after.
To the listener, this will be perceived as the signal pulsing back and forth between the left and the right speaker. This is really interesting to listen to in the recording studio because it enhances the stereo experience.
For the bass section of the Leslie Cabinet, it is recommended to use a microphone like the Sennheiser 421 dynamic microphone. This is a great microphone for picking up bass frequencies. It isn’t necessary to have more than one microphone on the Leslie bass woofer. Have the channel panned to the centre- this way, the low bass frequencies are central to the recording and won’t interfere with the stereo microphone configuration on the top section of the cabinet. If necessary, try using a high shelf-cut filter to achieve this. Separation is key to a great Leslie sound.
It is important to note that the Leslie speaker isn’t just used for the Hammond organ. Other organs recorded with a Leslie include Wurlitzer, Conn, Thomas and Baldwin. It is also sometimes used to record an electric guitar. Also, some engineers prefer to use a Shure Sm57 in place of the AKG414. These are dynamic microphones and have a very punchy mid-frequency sound to them. An engineer might also like to take the cabinet covering off when they record the Leslie. This will completely alter the sound, as the structural dimensions and the materials that make up the Leslie Cabinet play a vital role in how the sound resonates. There’s no right or wrong as to how it should sound. It is a matter of taste, but it is important to know how to get to where you want to go.
When the microphones are set up on opposite sides (either side-side or front-back) of the cabinet, the signal that is pulsing through the speakers in the recording studio control room will be “in phase” (pulsing at the same time). When they are placed with one microphone on the front (or back) and the other on a side then the signal will bounce back and forth between the left and the right speaker. The sound will be “out-of-phase” and the sense of stereo will open up greatly to the listener. Whilst this is a great tool for recording engineers, it is also a creative method of recording a Leslie speaker that will ultimately be the music of the artist. So it is great for the artist to know about this possibility, as it is a creative choice they can make on their song’s recording.