We have seen a growth in interest in high resolution recording and the continuing debate around the merits of recording at higher sample rates. In his recent piece on working at 192KHz Dan noted both pros and cons although many of these were practical and related to the operation of equipment and plug-ins rather than the effect of capturing audio at extended sample rates.
Microphones Operating At Extended Sample Rates
In the video above, a team working with Sony use their new range of Hi Res microphones to address the fact that the majority of microphones are designed to operate within the range of human hearing, not at all unreasonable and hardly a criticism, and to take advantage of potential contribution of of frequencies over 20KHz it is essential that the microphones used in hi res recording operate properly over 20KHz. Something which can’t be guaranteed in mics which aren’t designed to do this.
Mics For 96K Recording
The new C-100, ECM-100U and ECM-100N mics from Sony have all been designed to operate predictably up to 50KHz and it is these which were chosen for the case study in the video above where they were used in combination with a DAD AX32 to capture the sound of a newly built and unique piano created by Australian piano builder Wayne Stuart which goes beyond the, previously unchallenged king of pianos, Bosendorfer Imperial Grand with its 96 keys by extending this to 108 keys, that’s 9 octaves!
There are other contenders for mics, which are designed for this kind of very high frequency use. Earthworks have their QTC50 which, although an excellent mic for audio recording does illustrate the fact that microphones that are designed to operate at very high frequencies do tend to owe some provenance to measurement mics and test equipment, particularly as one of the more common uses for these very high frequencies is in acoustic testing where scale models of spaces are built and correspondingly high frequencies are used to extrapolate the behaviour of the full size buildings.
Mics For 192K Recording
Most of us know about Nyquist and if we are recording at 96K ideally we should be using mics which are designed to work to 50KHz. By the same logic, if we are using 192K then ideally we would be using equipment which is good to 100KHz. The only contender I’m aware of is the Sanken CO-100K, if you know of others please share in the comments below. I suspect that many of the best quality small diaphragm condenser mics actually perform well beyond their quoted specs and it is just that testing stops at 20KHz.
A Recording Is Only As Good As its Weakest Link
While the transducers are the most important part of a signal chain, that is not to say the the rest isn’t important and if your mic preamp isn’t up to the job then the recording will of course suffer. 192KHz is the limit of performance for most equipment, a lot of the appeal of 192 for those who use it is that it is the “best”. However it sort of isn’t.
DSD Recording At 384KHz With the DAD AX32
The AX32 is the ideal choice for a ‘high-res’ project like this piano recording because DAD were the first to design converters that handle sample rates up to 384 KHz. The AX32 follows the track of the earlier AX24 with an enhanced performance on the standard sample rates and the high sample rates like 192 KHz, DXD, 384 kHz and the one bit DSD format. DSD isn’t well known outside the ultra high end of classical recording because, while the quality and resolution is unparalleled, it is a fundamentally different system than the familiar PCM digital we all understand.
Preamps and Converters
Of course the preamps are going to be challenged by high resolution recording just as much as any other component in the chain and as well as the challenge presented by the wide dynamic range of a recording, this dynamic range needs to be faithfully captured at frequencies not usually in the brief of a typical recording. In my multi part review of the AX32 I was struck by the quality of the mic preamps and in particular by the effortless operation of them at the limit of their available gain. These also impressed Craig Field, the engineer on the piano recording:
In order to capture every single note in as much detail as possible, Craig Field used Sony C100 high-resolution microphones and fed their signals directly to one of our AX32 units with the preamp card installed. As Craig Field puts it: "I've been seeking a transparency in my recordings for quite a long time", and with such a microphone in combination with our super-transparent mic preamps and AD-conversion, it is a setup that is hard to beat.
96K workflows are more common than ever, it won’t be long until as much work is being done at 96K as at 44.1/48. 192K will inevitably follow and it is important that the entire signal chain works reliably and predictably at high sample rates if the benefit is to become more than theoretical. Equipment like these mics and the AX32 are an essential part of this journey but I for one am intimidated by the demands that 192K and Atmos workflows will put on our systems, never mind our backup regimes if they were to be used together. What do you think?