Acoustics, Monitoring, Leads and signals

Acoustics

• The way surfaces in a room absorb, reflect and diffuse sound gives us our perception of that space

• A room with lots of hard surfaces (for example, glass and painted concrete) will be reflective, and a room with lots of soft surfaces (carpets, curtains, sofas and so on) will be less so.

• The more reflcective the room, the longer the reverb time

• A larger room will have a longer pre-delay; a smaller room will have a shorter pre-delay

• On a reverb unit, the pre-delay paramter allows you to alter the apparent room size without changing the reverb time

• Acoustic treatment can help to ensure the accurate capture and monitoring of audio without unwanted colouration from the room.

• Using acoustics treatment to control absorption, reflection and diffusion can help to solve issues such as flutter echoes, standing waves and comb filtering

Reflection and standing waves

• Sound waves bounce off any reflective surfaces in a space

• This can make the room very reverberant if there are reflective surfaces, but it also mighrt be too dry if there aren’t any

• To make a room less reflective, soft surfaces or acoustic treatment can be added to the walls

• Reflections can cause cancellation or an increase in amplitude for a sound wave at a specific frequency

• We use acoustic treatment to prevent standinf waves from affecting our recordings in a live room or our perceptions of frequencies in a control room.

Isolatrion Booths

• Isolation booths are normally acoustically treated and insulated.

• These booths are normally rooms within a room and have a dual purpose, isolating the performer from other instruments that could mean that spill is recorded onto that track, and isolating that musician from creating spill on another

• This tends to be most important when recording drums (which often spill onto other tracks because of their loud volume), and vocals (whcihneed to be the most isolated)

• You can also use screens to increase the separation between different instruments when recording them at the same time.

Monitor Speakers

• Studio monitors have a relatively flat frequency response, meaning they don’t emphasise particular frequencies.

Monitor Speakers - Lost in Translation

If you mix on speakers that aren’t completely accurate, some frequencies will be reproduced louder or quieter than they should be. You are likely to boost or cut these frequencies further when preparing you mix, and when the mix is played back on other speakers, the problem frequencies will either be lacking or over-emphasised; we call this issue ‘translation’.

• Studio monitors normally have two separate speakers within them: a tweeter and a woofer

• The tweeter is designed to handle high frequencies (2kHz-20kHz), and the woofer everthing else below this.

• Some audio systems might also use a sub-woofer, which handles very low frequencies (below 100Hz)

• Some studios use three-way monitors for even greater acoustics

• A crossover is used to separate out the signals for the speakers so that the tweeter doesn’t get any of the signal meant for the sub-woofer. It basically works as series of filters - a high pass filter for the tweeter and a low pass filter for the subwoofer.

Cables and connections

• XLR

• Jack

• RCA (Phono)

• TOSLINK

• MIDI

• USB

• FireWire

Electromagnetic induction in speakers

Cables and Connectors - XLR Connections

• XLR connections have male and female ends; male connectors have pins, wheras female connectors have sockets

• There are three pins: hot, cold and ground

• They can daisy-chained, to create a longer lead.

Cables and Connectors - Jack Connections

• There are two different sizes of jack connection: 3.5mm and 6.35mm (or ¼”)

• There are also two types of jack connection: TS and TRS (Tip-sleeve and tip-ring-sleeve)

• TS jacks consist of two wires, and TRS consists of three

• TRS jacks can be used as a balanced, or as a stereo connection

• A variation of the TRS jack is used as one end of an insert cable connected with two separate TS jacks.

Cables and Connectors - Unbalanced and balanced connections

• XLR cables and TRS jacks are what we call balanced connectors

• They cancel out noise picked up as part of the cable run

• A balanced cable contains three connections: hot (+), cold (-) and a ground

• The cold signal is a polarity inverted version of the hot signal

• Noise is picked up equally on the hot and cold signals

• When both of the signals reach their destination, the cold is polarity inverted again. This means that the polarity of the signals is now the same, but the nosie is of oppoiste polarity in the hot and cold signals.

• Combining the hot and cold signal means that the noise completely cancels out, and the signal becomes twice as loud.

• Cables also include shields; this is a ground connection that protects against interference

• Long cable runs can result in signal loss.