High sample‑rate recording formats offer an extended audio bandwidth, but there are currently few microphones with a frequency response to match. Hugh Robjohns tries out the first commercial studio microphone designed specifically to address this new market.
The MKseries of microphones has been around quite a few years now and has established an excellent reputation. Most of the models have fixed polar patterns, and all use Sennheiser's unique RF condenser technology (see box). The flagship model, the multi‑pattern MKH80, is the most versatile of the range, and is intended for general‑purpose studio applications.
However, the latest addition to the family, the MKH800, is, in effect, a reworked MKH80, identical in external appearance and facilities but with a flat frequency response extending to 50kHz, whereas its ancestor tails off after 20kHz. This has been achieved through a modified capsule arrangement minimising interference at high frequencies, plus a revised head amplifier to accommodate the considerably wider bandwidth.
Digital recording and mastering systems with elevated sampling rates — 96 and 192kHz, or Sony's DSD format — all have audio bandwidths far wider than conventional digital systems and, arguably, most analogue ones too. However, few microphones have been designed to capture frequencies above 20kHz (indeed, many have purposely curtailed HF responses) and those that are capable of recording ultrasonic frequencies are largely intended for use in acoustics laboratories. Sennheiser claim their new MKH800 is the first commercially available studio condenser microphone with a flat response to 50kHz and specifically designed to complement high sample‑rate recording.
The academic arguments over the alleged advantages of high sample rates are complex and lengthy, but many believe there are sonic benefits over conventional digital systems, including a greater and more natural sense of 'air' or 'space' together with better stereo‑image precision and localisation. This is not the place to pursue these points in any depth, but my own experience of several high sample‑rate systems largely supports these findings.
The MKH800, like its ancestor, is a side‑address microphone. Its 20mm dual‑diaphragm capsule is protected by a black wire‑mesh grille open to the top as well as both active sides. The front of the microphone is identified by a column of four black rotary switches, a red 'aiming' LED, the Sennheiser label and the model name. A standard 3‑pin male XLR socket is provided at the base of the microphone which requires standard 48 Volt phantom power.
The four rotary switches each have a recessed horizontal slot together with a raised vertical bar carrying a marker dot at the top. Although stiff, I found they could be adjusted without too much difficulty. The uppermost switch determines the polar pattern, which can be selected from omnidirectional, subcardioid, cardioid, hypercardioid, or figure‑of‑eight, while the second control provides pre‑attenuation of 0, 6 or 12dB. Low frequencies can be rolled off with 0, 3 or 6dB attenuation at 50Hz, and the higher frequencies emphasised by 0, 3 or 6dB at 8kHz. This last control is unusual on a microphone of this type and is intended to rebalance the upper register when the microphone is positioned a long way from the sound source. In this 'diffuse field' condition, high‑frequency energy is rapidly absorbed during transmission through the air and by boundary surfaces, tending to dull the sound. The switch allows two levels of compensation to be introduced, there being a noise advantage in adjusting the frequency balance at the microphone rather than with console equalisation.
A nice ergonomic point is that the HF emphasis switch turns clockwise to increase gain whereas the pre‑attenuation and LF filter switches turn anticlockwise to reduce it. With all switches set to their vertical position the microphone functions at maximum sensitivity, as a cardioid with a flat frequency response. The red LED just below the capsule is recessed deeply into the body, giving a small angle of view to facilitate precise visual alignment. Careful aiming of the microphone is important, apparently, as the polar patterns narrow considerably at ultrasonic frequencies.
The polar response plots shown in a brochure supplied with the review microphone are stylised to the point of perfection, so I am unable to comment on how much the polar patterns narrow above 20kHz. However, I can tell you that careful listening suggests the responses to be well defined and consistent across the (my) audible frequency range. They all exhibited smooth off‑axis responses, free from coloration and the figure‑of‑eight has deep, tight nulls on either side. Similarly, the rear rejection of the cardioid and hypercardioid is extremely good across the majority of the frequency range (they open out a little at the bottom end, but that is not unusual). The omnidirectional pattern also appears to be very consistent at all audible frequencies and in all planes. Interestingly, the frequency response plots all showed a prominent peak of a good 5dB centred around 35kHz, and all but the cardioid and wide cardioid patterns displayed a small suck‑out around 20kHz. These peaks did not cause any obvious problems.
Apparently, the revised head‑amplifier of the MKH800 not only delivers a wider, flatter frequency response than its ancestor, but is also 1dB quieter. Its equivalent noise level is claimed to be an astonishingly low 9dB(A) so the technical quality of this microphone will challenge even the best microphone preamps!
Being one of the first two models brought into the country, the review mic was supplied without any of the usual accessories. However, Sennheiser suggest that it will ship with a padded plastic case with simple shockmount, stand adaptor and windshield like the MKH80. These accessories, as supplied with the MKH80, are effective and well designed.
Rigging this microphone in front of my usual range of test subjects was a real pleasure because, as you might expect from a flagship mic of this kind, it coped superbly. The MKH800 captures the most subtle nuances of complex instrumentation perfectly and responds very well to small adjustments to its axis and distance, allowing precise tailoring and balancing of the captured sound. Microphones with less well‑behaved polar responses and unpredictable off‑axis coloration can rarely be controlled in this way.
When used at greater distances on woodwind and piano, the HF boost switch was effective in capturing the ambience and natural acoustic which compared well to that experienced in the room itself. I found the results obtained by using this onboard boost sounded more natural and integrated than I could achieve with simple console EQ. However, leaving the HF boost switched in when close‑miking a 12‑string guitar is definitely not recommended, as the over‑emphasised high‑order harmonics were positively painful! I also tried using the HF boost as a kind of 'aural exciter' effect on close‑miked vocals. Surprisingly, it worked quite well with the 3dB setting on a male voice, although I suspect the results would be very source‑dependent.
The MKH800 really is a top‑notch microphone, achieving technical excellence few can match. With no discernible character of its own, it is extremely clean‑sounding with an obviously wide, extended frequency response, and manages highly accurate renditions of even the most complex sources. Some may not think its neutral character endearing, but I found its crisp top end, rich controlled bass and detailed mid‑range to be similar to those of my favourite Soundfield microphone. The MKH800 can capture low frequencies below 30Hz, but suffers only modest proximity effect in the directional patterns, and is not unduly prone to mechanically induced noise, particularly when used with a shockmount.
The existing MKH80 can accommodate sound‑pressure levels of up to 142dB, and it seems reasonable to assume that the new 800 can match this performance. It certainly coped with everything I threw at it without any sign of distress! The microphone generates a very high output level of around 40mV/Pa (around ‑30dB ref:1V/Pa) — a good 15dB more sensitive than an AKG C414 and about 8dB louder than a Neumann U87. This means considerably less gain is required in the console mic amps than with most equivalent microphones, and so a lower noise floor should result — particularly welcome in distant‑miking applications.
Most of my auditioning was carried out through an Apogee PSX100 A‑D converter which I switched between 48 and 96kHz rates in search of any significant changes to the upper register. Although the effect was pretty subtle, I did end up convincing myself that the MKH800 provided a sense of detail and naturalness which was preserved by 96kHz sampling but discarded at 48kHz. However, I have to say that similar effects were obtained from other, more conventional capacitor microphones (particularly a small‑diaphragm model), so I don't honestly know if what I was hearing was attributable specifically to the MKH800, or the Apogee, or both!
Even if you are unconvinced of the pressing need to record bat conversations, the MKH800 is undoubtedly Sennheiser's best microphone yet — and that is quite something given the high quality of its stable mates. Although a high‑budget purchase, this is a very versatile mic which will never be found wanting.
The microphones in Sennheiser's MKrange share a unique operating principle. In a conventional capacitor microphone, the condenser capsule operates in a very high‑impedance circuit, where its varying capacitance modulates the DC biasing voltage applied across the plates. In this way sound is translated directly into a varying audio voltage. However, this system requires a head‑amplifier with an enormous input resistance (over 1 GigaΩ) which is technically challenging and, in humid conditions, is susceptible to noise and distortion caused by the electrostatic biasing charge leaking into the atmosphere. The high biasing voltage also attracts dust particles to the diaphragm, reducing its efficiency and linearity.
The RF Condenser principle employed in the MKrange uses the capacitor capsule in a completely different way. Essentially, the capsule capacitance is used as the tuning element of a radio‑frequency oscillator. Changes in capacitance reflecting sound‑pressure levels phase‑modulate a 10MHz carrier wave which is subsequently demodulated back to a changing audio voltage inside the microphone.
The advantage of this technique is that the capsule operates in a very low‑impedance circuit (say, 400Ω instead of 200MΩ). This makes it virtually immune to the effects of humidity, and it no longer attracts dust particles electrostatically to the diaphragm surface.
- Extremely quiet, with a very high output.
- Accurate and consistent polar patterns.
- Very low coloration.
- First mic to offer 50kHz bandwidth.
A flagship microphone designed to meet the challenges of high‑resolution recording, with a 50kHz bandwidth and phenomenally low noise floor. Superbly accurate and consistent polar patterns, very low distortion and coloration, and a high output level make this the microphone of choice given a suitable budget.