Time Alignment)

Measurement for Live Sound

Welcome! Instructor: Jamie Anderson

2008 – Present: Rational Acoustics LLC Founding Partner & Systweak 1999 – 2008: SIA Software / EAW / LOUD Technologies Product Manager 1997 – 1999: Independent Sound Engineer A-1 Audio, Meyer Sound, Solstice, UltraSound / Promedia 1992 – 1997: Meyer Sound Laboratories SIM & Technical Support Manager 1991 – 1992: USC – Theatre Dept

Education MFA: Yale School of Drama BS EE/Physics: Worcester Polytechnic University Instructor: Jamie Anderson

Jamie Anderson [email protected]

Rational Acoustics LLC Who is Rational Acoustics LLC ? 241 H Church St Jamie @RationalAcoustics.com Putnam, CT 06260 Adam @RationalAcoustics.com (860)928-7828 Calvert @RationalAcoustics.com www.RationalAcoustics.com Karen @RationalAcoustics.com and Barb @RationalAcoustics.com SmaartPIC @RationalAcoustics.com Support @RationalAcoustics.com Training @Rationalacoustics.com Info @RationalAcoustics.com What Are Our Goals for This Session? Understanding how our analyzers work – and how we can use them as a tool

• Provide system engineering context (“Key Concepts”)

• Basic measurement theory – Platform Agnostic Single Channel vs. Dual Channel Measurements Time Domain vs. Frequency Domain

Using an analyzer is about asking questions . . . your questions Who Are You? What Are Your Goals Today? Smaart

Basic ground rules • Class is informal - Get comfortable

• Ask questions (Win valuable prizes!)

• Stay awake

• Be Courteous - Don’t distract!

TURN THE CELL PHONES OFF NO SURFING / TEXTING / TWEETING PLEASE! Continuing Education AKA: What can I do after I leave here? • RYM (RTM, RTFM) – For Smaart, read “Getting Started with Smaart v7” – Skim the help ﬁles in the program

• Online at www.RationalAcoustics.com – Rational Support Forums – Rational Documentarium

• Attend training sessions

But most importantly, make measurements! Recommended Reading

www.rationalacoustics.com/store/books

***** SHAMELESS PLUG ******! The Only Math You Need Today: T= 1 ms T= .5 ms ƒ = 1 kHz ƒ = 2 kHz T=1/ƒ ƒ = 100 Hz ƒ = 250 Hz T= 10 ms & T= 4 ms ƒ = 20 Hz T= .1 ms ƒ = 500 Hz T= 50 ms ƒ = 10 kHz ƒ=1/T T= 2 ms T= .1 ms ƒ = 10 kHz Audio Frequency Spectrum

Audible Range: 20 - 20,000 Hz (1000 x) or more realistically . . . 30 – 18,000 Hz (600 x) System Alignment & System Engineering What is wrong with this system? Why doesn’t it sound good?

Data is meaningless without CONTEXT! System engineering is managing interactions . . .

. . . with a goal. System Engineering / Alignment: Goals • Engineering – Proper operation of equipment (Job #1) – Consistent coverage – Level / Power

• Alignment (Voicing ?) – The system alignment needs to ﬁt the goal • Tonality • Imaging

• Remember - listening is the goal! Just Because You Can Operate a CAT Scan . . . Doesn’t Make You a Doctor! System Engineering / Alignment: Quay Koncepts

• Systems Interact Most Where They are Equal Level

• Solve the Problem at the Source

• Use the Right Tool

• 20% / 80% Managing Interactions: The Big Question

+ = ?

or or Addition of Sine Waves! of Same Frequency and Equal Amplitude!

Φ = 0 Degrees Complete Addition

Φ = 90 Degrees Partial Addition

Φ = 120 Degrees No Addition

Φ = 180 Degrees Complete Cancellation

Φ = 240 Degrees No Addition Example:

1 kHz Comb Filters: Addition of Signals of Varying Relative Level

Equal Level 3 dB Level Diff. 6 dB Level Diff. System Engineering Key Concept:

• Interactions are greatest where signals are equal level - Crossover Points System Engineering Key Concept:

• Interactions are greatest where signals are equal level - Crossover Points

– Relative phase governs the interaction – Phase Shift (Filters) – Polarity (Wiring) – Delay (Time Alignment)

• Relative Level & Phase is KEY!!!!!!!! System Engineering Key Concepts:

• Solve problem at source

– The closer to the source . . . the more effective the solution. Example: Source EQ X-over Amp Speaker

The speaker you are measuring has a relatively ﬂat response except:

HF is 6 dB lower than LF above 1.6 kHz Target response: nominally ﬂat Substantial HF noise 6dB

0dB 125 250 500 1k 2k 4k 8k

-6dB Example: Source EQ X-over Amp Speaker

The speaker you are measuring Potential Solutions has a relatively ﬂat response EQ: except: Bring up HF on EQ HF is 6 dB lower than LF above 1.6 kHz Add extra HF to program material Substantial HF noise 6dB

0dB 125 250 500 1k 2k 4k 8k

-6dB Example: Source EQ X-over Amp Speaker

The speaker you are measuring Potential Solutions has a relatively ﬂat response Level: except: Turn up HF on Amp HF is 6 dB lower than LF above 1.6 kHz Turn up HF at X-over output Substantial HF noise 6dB

0dB 125 250 500 1k 2k 4k 8k

-6dB Example: Source EQ X-over Amp Speaker

The speaker you are measuring Potential Solutions has a relatively ﬂat response System Maintenance: except: Loss of 6 dB and in crease in HF noise a good HF is 6 dB lower than LF above 1.6 kHz indication of a bad cable on X-over HF out. Substantial HF noise 6dB

0dB 125 250 500 1k 2k 4k 8k

-6dB One Bad Cable . . . System Engineering Key Concepts:

• Use the right tool

– “Every item in your tool box is a hammer . . . except your wood chisels, they’re screwdrivers.” Tools in Order of Use

• Acoustic Design //Treatment Treatment 1 • Equipment Choice / Maintenance • System Design - “Design to align”

2 • Level • Delay / Timing

3 • And lastly . . . EQ Example: Soluon(s) Our goal is to ﬁx our system . . .

. . . not the trace on the screen!

Smaart is NOT a video game! System Engineering Key Concepts:

20% / 80%

– The ﬁrst 20% of effort provides 80% of the beneﬁts.

– System alignment takes as much time you have.

– Each task can take 100% of your time. Kinkade’s Korollary System Alignment & Smaart

System Alignment: Is a Series of Decisions Made in Context It is Optimizing Your Compromises

Smaart: Is an Analyzer . . . Is a Tool An analyzer is only a tool: YOU make the decisions

You decide what to measure.

You decide which measurements to use.

You decide what the resulting data means.

And you decide what to do about it. System Alignment

“Smaart-ing” a System System Engineering & The Serenity Prayer . . .

Grant me the Serenity To accept the things I cannot change…

Courage to change the things I can,

And Wisdom to know the difference. Measurements & Analyzers Analyzers

• Analyzers are our tools for asking questions

• Different measurements are good for asking different questions Our Two Basic Questions

What do we have?

What do we have, relative . . . Our System Measurement Model

Input System Output Measurement Types: Single Channel vs. Dual Channel

Input System Output

• Single Channel: Signal Analysis What is the Input Signal? Absolute What is the Output Signal? Measured Directly

• Dual Channel: System Analysis What did the system do to the signal passing through it? Relative - In vs Out Measured Indirectly Why Dual-Channel?

The measurements have a reference – they can tell: • Arrival time of direct signal • Signal from noise • Direct from reﬂected

… And they are Signal Independent Transfer Function

System Input Signal Output Signal

Measurement Channel (RTA) Transfer Function Reference Channel (RTA) Transfer Function

System Input Signal Output Signal

Measurement Channel (RTA) Transfer Function Reference Channel (RTA) Transfer Function

System Input Signal Output Signal

Measurement Channel (RTA) Transfer Function Reference Channel (RTA) Fourier Analysis

• Jean Baptiste Joseph Fourier – All complex waves are composed of a combination of simple sine waves of varying amplitudes and frequencies Transforms A transform converts data from one domain to another. From one view to another

Time Domain Freq. Domain (Amp vs Time) (Amp vs Freq)

Waveform Spectrum FFT = Fast Fourier Transform What do you get if you transform a transfer function?

• IFT produces impulse response

Transfer Function . . . To . . . Impulse Response

*So . . . If Frequency Response can be measured source independently - so can Impulse Response* How Smaart Works

Input System Output

Measurement Signal

Reference Signal

Wave How Smaart Works

Input System Output

FFT Spectrum Views

RTA FFT

Spectrograph Wave Spectrum How Smaart Works

Input System Output

FFT

= FFT Transfer Function (Frequency Resp.)

Wave Spectrum How Smaart Works

Input System Output

FFT

IFT = FFT Transfer Function Impulse Resp. (Frequency Resp.)

Wave Spectrum Time Domain vs. Freq. Domain

Amplitude vs. Time Magnitude vs. Frequency

FFT

IFT Spectrum (RTA) Waveform Spectrum

Amplitude vs. Time Magnitude and Phase vs. Frequency

FFT

IFT Analysis Signal Analysis Response Dual Channel vs. SingleChannel vs. Channel Dual Impulse Response Frequency Response (Transfer Function) Basic Measurement Set-up Multi Measurement Set-up Thank You