Soundfield SPS422

Paul White tests a mic that's outstanding in its field — without going out and standing in a field.

SoundField are almost legendary for their microphones, which are unique in that they use four independent capsules to capture the sound field (hence the name). By varying the contribution of the different capsules, the system can emulate any discrete mono or stereo coincident microphone setup, all remotely controlled from a box up in the control room. Their top‑end Mk V mics even allow the engineer to record the capsule outputs as a 4‑channel matrixed signal, (4‑channel B format), then use the controller box to reconstruct the stereo outputs in such a way that the microphone pattern, angle and even direction can be changed. This is obviously very useful for specialist recordings and orchestral work, as changing the mic pattern allows the engineer to change the balance of direct and reflected sound, or to steer the mic's axis. And remember, all this can be done after the recording has been made, and the tape brought back to the studio.

The new SPS422 microphone system reviewed here is based around the same capsule geometry and matrixing principles as the SoundField Mk V and ST250 microphones, but its operation has been greatly simplified, and the price much reduced. The high audio quality, however, would appear to remain unchanged; the same hand‑made, individually tested capsules are employed as in the Mk V.

All the capsule matrixing parameters are linked to just two main controls for setting the capsule Pattern and the stereo Width, and the result is a single microphone that can take on just about any job you can imagine (apart from doubling as a tie clip model!). The benefit of remote pattern and width control allows the engineer to make adjustments while monitoring the result in the control room, but the option to record first, and dial in the mic parameters afterwards, has been omitted from the SPS422 on the grounds of cost and simplicity of operation.

The SPS422 may be used as either a variable‑pattern mono microphone or as a variable‑width, coincident stereo pair, where the mic patterns are again fully variable. As with the other SoundField mics, there are four sub‑cardioid capsules set in a regular tetrahedron (see pictures), and by adding or subtracting the outputs from these four capsules in different proportions, the different polar and width characteristics are produced. Additional compensation circuitry is employed, so that the small physical distance between the capsules is cancelled out, making the SPS422 a true single‑point microphone.

Those familiar with the existing SoundField range of microphones will notice that the SPS422 is in many ways similar to the ST250 system (reviewed in SOS June '95), the main differences being that the more costly ST250 also includes a B format output and a battery power facility, making it more of a broadcast tool than a studio microphone system.

The Package

The system comprises the mic itself, the 1U controller box, and a 20‑metre multicore cable to link the mic to the controller. An optional heavy‑duty shockmount is available, but a basic standmount is included with the standard package. All the necessary controls are on the controller box (there are none on the mic), which has two fully balanced outputs for connection to a mixing desk.

It's possible to use the mic in either end‑fire or side‑fire modes, and a switch for selecting the desired mode is provided on the control box. The output signals are also available in either XY or undecoded MS (Mid and Side) formats. The bargraph metering system provides level readout of the left/right signals in XY mode, and of the M/S signals in MS mode. A separate headphone output is provided, so the mic output can be monitored during setting up — again, useful for live recording work, where there may not be a suitable monitor system available.

If I had just one mic to take onto a desert island with me, it would probably be a SoundField, because it's the nearest thing to a no‑compromise jack of all trades that I've ever played with.

To set the microphone gain, there are two controls; one of which provides 10dB switchable steps from ‑30 to 0dB, and a further, continually adjustable Fine control with a +/‑ 10dB range. A further button allows the left and right outputs to be swapped over when the mic is used in an inverted position in side‑fire mode.

Most professional microphones have a switchable high‑pass filter, but in the case of the SPS422, an 18dB‑per‑octave low‑cut filter acting at 40Hz is built into the controller. The Mid/Side button switches the controller from conventional XY output to MS, but there is no MS decoder provided with the system, so you'll either need to buy an MS matrix box or use three mixer channels to set up your own sum and difference decoder. In practice, I feel few people will use the MS facility, unless they have a specialist reason for doing so.

Changing the microphone pattern is accomplished via a single knob, which may be continually varied from omni, through cardioid, to figure‑of‑eight, with all the hybrid options in between. In MS mode, the Pattern control sets the polar pattern of the equivalent XY pair, so the only difference is the setting of the MS switch. If the SPS422 was two separate mics, the Width control would change the physical angle between them, but here nothing moves — you have to imagine that you're changing the angle between two virtual mics. When Width is set fully anti‑clockwise, the SPS422 produces a mono output.

Using The SPS422

The microphone should be powered up for a few minutes before use, to allow the capsule‑charging process to stabilise, and to allow any condensation to disperse. For close‑up vocal work, a conventional pop shield is a good idea, but for any other application, it's just a matter of plugging the controller into your mixer and getting on with it. You'd normally feed the controller directly into a console line input or into a recorder such as a DAT machine, but you can also feed it into mic inputs if need be, providing they have a pad facility.

To use the microphone as a coincident cardioid stereo pair, which is always a good starting point, you set the Pattern and Width controls mid‑way and the Mid/Side switch out. Press End if end‑fire operation is required, otherwise leave this button out. The first test was to record a friend playing 12‑string guitar. Straight away, I was greeted by a marvellously clear, three‑dimensional sound. Experimenting with the Pattern control, I found I could let in more of the room ambience, by moving the pattern more towards omni. I could focus on the guitar while excluding most of the room sound, by going to narrow cardioid. The biggest surprise was the coincident figure‑of‑eight pattern, which produced a very tightly focused sound that cut out virtually all the boominess from the room, and actually seemed to produce a slightly brighter result than the cardioid pattern. In theory, the mic has the same response for all patterns, so the difference is most likely caused by the acoustic properties of the room — and it may be that the proximity of the wall behind the microphone plays a significant part. Whatever the reason, I found I could get a whole range of sounds that would normally have necessitated a lot of tedious mic moving.

The same is true when you come to mic up a drum kit, and although the SPS422 makes a good stereo overhead, it can also be used on its own to make super drum recordings — if you have a suitable acoustic space to record in. For these tests, I set up a kit in a friend's hallway, which has bare wooden floors and reflective walls. The mic was set up on a stand around five feet in front of the kit. Over the monitors, the kit sound was virtually indistinguishable from the live sound of the kit — except it wasn't as deafening!

On vocals, the mic has a big, rich sound and can hold its own against any of the large‑diaphragm condenser models popular in vocal recording. To record in mono, all you need do is turn the Width control to zero. Again, you can adjust the pattern during performance, to fine‑tune the sound instead of varying the mic distance.

Summary

The SoundField has two big things going for it — one is the sense of spaciousness it creates, and the other is the ability to remotely control the microphone, particularly the polar pattern, allowing you to hear any changes in real time in the control room.

Overall, the sound quality is superb, and other than the simpler facilities on offer, the SPS422 seems to be every bit the equal of its more expensive counterparts. If I had just one mic to take onto a desert island with me, it would probably be a SoundField, because it's the nearest thing to a no‑compromise jack of all trades that I've ever played with — though getting a mains lead long enough could be a problem! There are other mics that work as well in specific applications, but when it comes to choosing a 'mic for all reasons', I can't even think of an alternative to a SoundField.

Evaluated on price, the SPS422 is obviously a lot of money, but it's really not much more than some of the big name mono mics, and is vastly more flexible. It's also a lot less expensive than buying a Mk V if you don't need the B format facility, but if you need battery operation, you'll have to opt for the mid‑range ST250. Having experienced the luxury of the SoundField's sound and its controllability, working with conventional mics is always going to seem just a touch primitive.