Modern Recording Studios

How a Modern Recording Studio works, an essay by Mark Payne, Managing Director

Sections:

• Microphones
• Mixing Desk
• Signal Processing
• Recording Device
• Monitor Loudspeakers
• Room Acoustic Design

Microphones

Alpha and Omega

As the start of the audio chain, 'Large Diaphragm' condenser microphones are at the top of the studio shopping list. The diaphragm is the 'ear drum' of the microphone and exotic materials (gold is popular!) are used to form an extremely thin and delicate, lightweight 'ear'.

As this diaphragm moves in sympathy with recorded sound, an electrical characteristic called capacitance is being changed within the capsule. A preamplifier built into the microphone body amplifies this tiny signal change to a useable level.

Above: Manley Gold Condenser Mic with visible diaphragm

Above: Frequency response (top) and Polar Plot (bottom) for Neumann U87 Microphone

Studio microphones must not introduce 'hiss', they must reproduce all naturally occurring tones without colouration or distortion and be sensitive enough to accurately represent dynamic sounds from the very quiet to the very loud.

Shaping Up

The Polar Pattern is a map representing the loudness (sensitivity) of the mic as you move around it. The heart-shaped (cardioid) pattern above is sensitive at the front, quieter at the sides and 'deaf' at the back.

The use of such a mic on a vocalist would result in a direct and focused sound with the ambience of the recording room being rejected by the off axis 'deafness' of the mic.

Other polar patterns include 'omni directional' for general ambient recording and 'figure of eight' for specialised stereo recordings.

Legends, Superheroes and Honest Joe

Legends and superheroes in the world of studio condenser mics include the Neumann U87 and AKG 414 (£1500 - £2000) being loved the world over for vocals, acoustic guitars, strings, wind, cymbals and percussion.

Other less expensive but worthy contenders would be the Sennheiser MD421, a must for recording drums and skin percussion with the ElectroVoice RE20 for bass guitars and bass drums, both examples of moving coil microphones.

From top to bottom: Neumann U87, Sennheiser MD241, EV RE20

The 'Honest Joes' must be the Shure SM58 and SM57. More famous in live music applications, at less than £100 each, the SM57 and SM58 are affordable legends, featuring on a surprising number of pop/rock vocals and electric guitar recordings.

Shure SM58 and SM57 (Top to Bottom)

Mixing Desks

As the audio hub of the studio, the mixer is likely to have over 40 channels with inputs from microphones in the performance area and from the main multi-track recorder.

Where a conductor uses a baton to influence the sound of an orchestra, a sound engineer uses the mixer, bringing together the sounds from individual recorded instruments to create the overall impression.

The outputs from the mixer are fed to:

• Multi-track Recorder - Placing individual instruments on separate tracks
• Main stereo mix - Monitored through high quality speakers
• Auxiliary mixes - For performers often via headphone amplifiers
• Outboard sound effects and processors

Virtual Mixers

Above: Screen Shoot from Adobe Audition software mixer

A high proportion of music and film audio is mixed within computer systems using software without the use of a traditional mixing console.

The digital audio process converts the 'real' electrical signals from microphones into a stream of representative 1's and 0's ready for processing by DSP (digital signal processing) within specialist studio mixing hardware or computers.

Above: Protools HD Mixing software and recording hardware

Digital vs Analogue

Digital mixers (hardware or software) bring flexibility, reliability and mixing power into one unit removing the need for masses of outboard gear. They also allow for the precise recall of settings allowing studios to jump from project to project without wasting valuable time.

Above: Yamaha DM2000 Digital Mixer

Some recording engineers still prefer to work on analogue mixers, especially true at the ultra high end where studios own the very best of what the analogue providers have to offer. However, digital mixing consoles have all but taken over in the midrange of professional recording. 

Above: Neve 88RS Automated Analogue Mixer

The characteristic sound of the classic mixer is formed primarily by the mic preamplifier quality and then secondly by the onboard tone controls. Consoles from SSL and Neve are the holy grail of audio performance with electrical bandwidths 5-6 times better than human hearing!

Modern techniques can seek to bypass the mixing console for in the pursuit of absolute audio quality. Products from TLA and Focusrite provide direct recording processors including a mic preamplifier (sometimes with classic valve electronics), compression, equalisation and digital conversion all in one box.

Above: Focusrite 'Liquid Channel' Preamplifier

Creative Mixing

The engineer uses the mixer as a creative surface to control and shape sound in terms of:

• The relative level of one instrument or voice against another
• The focus of attention to soloist passages, musical movements and overall power in a mix.
• The control of equalisation and tonal shaping of sounds.
• The spatial placement of sounds in the stereo space.
• The spatial placement of sounds in the front/back plane by manipulating reverberation

Additional audio processing comes by way of outboard equipment external to the mixer. With modern digital consoles much of this 'outboard' has come 'inboard' but the need for processing has not changed conceptually.

Processing During Recording

Engineers are careful to not commit to special effects and creative mix decisions during the initial recording process (called 'tracking') as they cannot be undone.

Digital recording is unforgiving to over recording as no level of digital distortion is acceptable. A recording processor should include a 'dead stop' limiter to ensure no digital 'over' events take place, many have a valve section that can be slightly overdriven to generate 'friendly' harmonic distortion making up for the clinical performance of the backend digital recording process.

Processing During Mixdown

Compression

Above: Classic 2 channel Drawmer 1960 studio tube compressor

Compression is the most important tool in the sound engineer's tool box. The loudness range of real world acoustics is naturally beyond the capability of most hifi systems. It is therefore necessary to limit the dynamic (loudness) range of recordings to facilitate reliable playback.

Ideally each recorded track requires separate compression. Parameters including 'ratio, threshold, attack and release' are used to manipulate dynamics. Compressing a lead voice (for example) allows it to be placed at a higher energy level in the overall mix ensuring vocals are clearly heard.

A 'De-esser' is a compressor made sensitive to higher frequencies, reducing 's' and 't' sounds. This allows a vocal to me made 'bright' in a mix whilst attenuating any over-sibilance.

Above: BSS DPR 402 with de-esser

Multi-band Compression

Used during the final mastering phase of a completed mix, multi-band compressors provide separate bass, midrange and high frequency dynamic control without being obvious allowing 'louder' and more impressive mixes.

Above: Multi-band Compressor: TC Electronic Finaliser

Gates

Gates are used to isolate recording crosstalk from 'acoustically adjacent' channels. When inserted on drum channels for example, a gate can be set to only open when that particular drum is struck, increasing definition and separation. Care must be taken not to over process with gating resulting in dated 80's production values.

Gates can be used to close out background noise on a suspect electric guitar or bass channel although troubleshooting the real source of the noise should take priority.

Reverberation

Modern contemporary recordings are often made in relatively small studios with little natural ambience. The sense of 'space' is added at mixdown by the use of simulated electronic reverberation.

Relative differences in reverb times allow spatial separation of sounds; a dry (unaffected) sound will appear at the front of the mix at the speakers with a reverberant sound coming from deeper or at the back of the room.

Reverb times of 1 to 1.3 seconds may be suitable for percussive instruments including toms, snare, conga etc where as 1.8 - 2.3 seconds would suit a vocal or brass instrument.

Above: Lexicon 960L reverb processor.

Delay

Delay effects provide a number of discrete repeats or echoes. Longer delays used sparingly on featured soloists or vocals can add a sense of the ethereal where very short delays can be used to thicken a vocal or brass line using the classic ADT (automatic double tracking) technique.

Short delay times can be modulated over time to provide special effects including 'phasing', 'flanging' and 'chorus'.

Above: TC Electronic D-Two Delay

Recording Devices

Its Gone Digital!

Above: (Left) 24 Track 2 Inch Struder Tape Recorder (Right) Alesis HD24 Digital Recorder

Advanced digital sampling at 192 KHz (lots of samples!) with 24 bit (lots of accuracy and headroom!) is now possible, even in project studios. Modern recording formats are exclusively digital and mostly reside on hard drive where analogue tape recorders reside in museums!

A modest studio will have between 24 and 48 tracks of simultaneous digital multi-track capability.

Old and new Players

The old Tascam DA88 family of digital tape based recorders (16bit) are still used in film and TV due to their reliability and synchronisation ability with video time code formats. Older project music studios favoured the lower cost Alesis ADAT.

Above: Tascam DA88 (left) and Alesis ADAT (right) Digital 8 Track Tape Recorders

The modern studio on a budget is now more likely to buy Alesis HD24, a 24 track hard disk recorder which can be combined in modular blocks to any required size. The low cost of hard drive storage has all but killed tape based recording.

The Alesis HD24 limits digital performance to 48 KHz sampling at 24bit resolution. This still compares well with the high end offerings from companies like Otari with the well respected Radar DR-100 system doing no better.

Above: Otari Radar DR-100

Advanced systems like Radar allow cut and paste type editing enabling complete songs to be assembled from short passages.

Interface

Once in the digital domain, the issue of sound quality becomes academic as one man's bit is the same the as another's! This is especially true where the mixing console is providing the Analogue to Digital (AtoD) conversion and the recording system is merely storing the digital sound data.

Interfacing the digital mixer to the modern digital recorder is via cabling more at home in the computer industry. Connections include the ADAT optical link, Tascam's TDIF and the AES/EBU standards.

Protools

Digidesign Protools leads the way in the provision of computer system based recording where a PC is expanded with special hardware to provide almost limitless track capability. Protools systems can be used stand alone as 'studio in a box' or in conjunction with more traditional studio infrastructures.

Above: Protools HD Environment

Monitor Loudspeakers

Above: Genelec G1034B Main control room monitors

Studio control room speakers are critical to the recording process as every sound is critically judged and processed in reference to them.

They must have oodles of headroom, able to generate high levels of sound pressure without colouration or distortion whilst producing a wide frequency range within the 20Hz to 20KHz bandwidth of human hearing. They must not be falsely 'flattering' in terms of tonality leading to lifeless mixes when the programme material is transported to other systems.

Near Field, Far Field

The recording engineer will want to work with 'near field' monitors close (within a 1-2m) to the listening position so as to 'process out' the room acoustics by focusing attention on the reproduced sound directly from the speakers and not from the room.

A larger control room may need a secondary and larger alternative 'far field' monitor system focused on the general listening area behind the mixing console for performers, producers and artists. Experienced sound engineers know to mostly work at low sound pressure levels so as not to stress critical hearing judgement over the working day. Performers being recorded 'in control room' are likely to desire much higher levels from the larger system.

Bad is Good

Above: Yamaha NS10 Near Field Monitors

The industry standard Yamaha NS10 near field speaker system (now discontinued) is well known for being 'bad in the right way'. This speaker is reckoned to be the acoustic average of the planet's middle-of-the-road hifi systems and has become a kind of perverse reference.

Really Bad is Good

The Auratone 5C (nicknamed the 'Horror Tone') is a 'must have' reference monitor with a small 5 inch driver, representative of how bad a mix will sound on a typical TV speaker or cheap radio. Engineers will audition a work in progress to a single Horror Tone periodically to ensure the mix has sanity in the mono low fidelity world.

Getting the Point

Speaker manufacturer Tannoy pioneered the concept of 'dual concentric' speaker design in the 1960's with the 'Red' and 'Gold' studio monitors. The high and low frequency drivers share the same physical axis with the tweeter firing through a small horn flare in the centre of the woofer.

This creates a near point source sound field with no tonal shifts due to the relative position of the listener to the speaker. Big speakers can otherwise tend to work against point source advantages.

Above: Tannoy 15 Inch Dual Concentric Main Monitor

Room Acoustics

The acoustics of the control room should be like a well behaved child ie. 'Seen and not heard'! The objective of the control room space is to hear, judge and process the recording ambience of sounds made elsewhere.

Above: Large live room with triple glazed window to control room.

The live room may be similarly characterless for the recording of contemporary music but it may be required to impose character and natural ambience for acoustic and classical recordings. To have significant and realistic character, a room needs significant size.

Live rooms often have different areas with a choice of floor and wall finish to provide acoustic options to the recording engineer. For example, the sound of a string quartet being recorded on a carpet tiled floor with curtains surrounding the walls is quite different to a wooden floor with exposed brick work for the walls.

Golden Ratios and Complexity

Rooms are designed with dimensions (height, width, length) unrelated by simple fractions. Accepted 'Golden Ratios' exist to avoid 'boomy' sounding rooms.

Walls, ceilings and floors are made non-parallel to further prevent standing waves (sound bouncing between surfaces). Reflective concave surfaces are avoided to prevent the focusing of sound into 'hot spots'.

Above: Avenue Edit Studio, Shaped walls and non parallel ceiling

Live End / Dead End, Absorb and Diffuse

Good practice dictates that the monitor speaker end of the room should be absorbent leading to increased separation and accuracy heard from the monitors. This is known as the 'Dead End'. The sides of and ceiling area around the mixing desk and sound engineer should also be semi absorbent to cut down on confusing early reflections.

Above: Alicia Keys' Studio with RPG diffusers on rear wall

The rear of the studio behind the sound engineer should be primarily diffusing. This is the 'Live End'. Sound hitting the diffusing rear wall will be spread into complex reflections in all directions. This leads to a natural acoustic and reverberation that does not interfere with the intelligibility and accuracy of the monitor loudspeakers.

Noise and Isolation

The live room and control rooms must be acoustically isolated from each other and the building around them. Good recordings cannot be made in the presence of noise. Similarly the use of a studio needs to not cause nuisance to local residents and other building users.

Studio builds include high performance acoustically isolating walls and ceilings with floating isolated floors and triple glazing between the control and live rooms. Access to the control room or live room should be via heavy duty sealing doors off of a corridor with no direct access between the live and control rooms.

Above: Magnetically sealing doors at The George Martin Studio, LIPA

Air conditioning and ventilation systems need to be designed so as not to generate noise themselves or compromise the sound insulation of the recording rooms.