NSF Reverb Plate
Although there are many different ways of producing reverberation, the plate is still the traditional method of producing high quality, natural sounding reverb.
The NSF plate is designed to give professional performance at an affordable price and in this respect it fills a gap in the market, falling between the better spring units and the further up-market digital devices, and full sized plates.
For those unfamiliar with the workings of plate reverb units, a brief recap is in order.
A metal plate under tension is forced into vibration by means of a transducer which is driven by an amplified version of the required signals. The resulting vibrations emanating from the transducer source are reflected back and forth from the edges of the plate and are picked off by strategically placed surface pickups to be reamplified and mixed with the original signal.
The NSF plate is smaller than most of its counterparts, external measurement being 42 inches square by 8 inches deep with the case made of plywood. The plate itself is made of a titanium steel alloy, three feet square, and is held under tension in a steel frame formed from one inch square tubular steel finished in white enamel. Tension is applied by threaded tensioners positioned at the corners of the plate. The input signal is applied via separate high and low frequency transducers.
The low frequency transducer is a moving coil device, the coil of which is fixed to the plate and the magnetic assembly of which is fixed to the frame.
High frequency drive is applied by means of a piezo-electric transducer mounted directly on the plates' surface, it is the use of these two drivers that is largely responsible for the wide frequency response which extends from 100 Hz to 17 kHz.
The pickup transducers are also piezo-electric devices and are mounted close to the edges of the plate, the optimum positioning having being determined empirically.
Also mounted on the frame is the PCB containing the head amplifiers which are based around the LM381, two channel pre-amplifier IC, this being remotely powered from the main control unit.
The natural decay time of the plate is approximately four seconds, this is too long for many requirements and so a remotely controlled damping device is fitted.
A small hand-held controller is provided enabling the amount of damping to be varied by means of a motor driven pad which is moved towards or away from the plates' surface.
The bulk of the electronics is housed in an attractive, if unremarkable 19 inch, 3U rack case, this being finished in blue and white. All controls except the remote damper switch are mounted on the front panel with the power switch and fuse labelled ZAP and POW respectively! A modular 30 watt amplifier drives the transducers and an illuminated blue meter indicates the signal level. A level control is provided to adjust the input signal gain, tonal variation being provided by two controls, a variable treble cut and a bass cut switch which enables the low frequency signal to be rolled off below 200 Hz at a rate of 6 dB per octave, thereby reducing any booming effect.
Connecting up is straightforward, requiring only a mono input with a stereo unbalanced output. Test programme material included drums, keyboards and vocals though it must be remembered that this type of appraisal must necessarily be subjective.
I found the bass cut switch position to be mandatory in order to keep the bottom end under control, but otherwise the sound is bright, characterised by a fairly rapid high frequency diffusion and a certain amount of metallic colouration, mainly apparent on percussive sounds.
The damper works well though it does generate a noticeable amount of electrical interference during adjustment. It is therefore impractical to alter the decay time during a mixdown. When fully damped the reverb sound is little more than ambient whilst withdrawing the damper completely, produces an effect which is best described as cavernous.
The small physical size of this plate unit means that it can be used in most environments providing that it is acoustically isolated from its surroundings.
I know of an NSF plate currently installed in a mobile recording studio mounted horizontally under a bed! Apparently most of the NSF plates have so far been sold to eight and sixteen track studios, with a few exceptions at both ends of the market. Another application might well be the video production business or even theatre groups.
With a quoted signal-to-noise ratio of better than 70 dB unweighted, the system would not be out of place in a fully professional environment, however, the all inclusive price of £595 puts it well within reach of smaller studios and even serious home enthusiasts.
I would have preferred the sound if the high frequency end did not decay so quickly, but in general, the sound quality was satisfactory and exhibited none of the bad habits found on spring units.
The rugged construction and the simplicity of the mechanics means that there should be no reliability problems, but in the event of a failure most of the components are commonly available and a good backup service can be provided by NSF themselves.
Ultimately the commercial success of this reverb system depends on the quality of competing digital units in the same price range, this will inevitably mean that in the near future there will be some very stiff competition in this area.
For further details contact NSF, (Contact Details).
Review by Paul White
Previous article in this issue:
Next article in this issue:
mu:zines is the result of thousands of hours of effort, and will require many thousands more going forward to reach our goals of getting all this content online.
If you value this resource, you can support this project - it really helps!