Testing loudspeakers in a production environment - the P630 test system K & K International Ib Rasmussen

Requirements for quality test Fast Reliable detection of approve / reject Working in a production environment Easy to use Cost effective K & K International

Typical parameters for a quality test Frequency Response SensitivitySPLPolarity Rub & Buzz (THD) ImpedanceResonanceQ For R&D: IMD(THD)T/S K & K International

P630 Frequency response test’s  Frequency test against limits relative / absolute / SPL  Frequency curve test against 2. and 3. Limits  Polarity test  Phase curve test against limits  Sensitivity and curve shape  5 different sensitivity tests of 1 frequency point  2 different average tests of sensitivity points  Frequency average test of multi frequency points  Group indication K & K International

P630 Impedance test’s  Impedance curve test against limits  Resonance frequency test  Qms test  Qts test  F test  Measured Re  EBP test  Current curve Rub & Buzz test K & K International

P630 distortion test’s  Rub & Buzz test against limits Ch B  Rub & Buzz test against limits Ch D  THD or TD test  Ambient noise check limits K & K International

P630 access levels Operator Run-mode QC engineer Setup-mode R&D engineer Global-mode Utility’s Testing Measurement Parameters Limit’s Signal analysis Statistics User interface Utility's Data management K & K International

P630 high performance  Using system multiplexing  Parallel signal processing  Sine sweep for a reliable Rub & Buzz test  Impedance measurement done by current sensing  All measurements done by 1 sweep K & K International

P630 Main Menu

Example of Main Setup Menu

Example of sub menus

Easy to make curve references  Curve by hand  Generate data with a reference speaker  Using a compensation curve (straight line)  Generate references from statistical data  Out-compensate deviations (master compensation) K & K International

Example on a statistical processing of measuring data

Example of Statistical processing - STD

Example of P630 Run-Flag Mode with noise check enabled

Example of P630 Run-Graph Mode

THD and Rub & Buzz   Sensitivity of the ear   Masking threshold   Level of THD & Rub & Buzz K & K International

Sensitivity of the ear

Masking Threshold kHz

Example THD 3% Rub & Buzz 27 db 20 db OK Speaker Bad Speaker

Example THD 3 % Rub & buzz – 20 db below – bad speaker

Speaker distortion non-linearly elements, magnetic - mechanic missing / bad glue mechanical out of tolerance wire problems electrical - mechanical air noise problems particles in speaker K & K International

Different types of Rub & Buzz Harmonics generated Selective resonance Random generated Wide band noise - air noise K & K International

Examples of non-linearity Harmonic generated Voice coil Inductance Voice coil Inductance Motor – Force Factor Motor – Force Factor Mechanical Suspension Mechanical Suspension K & K International

Inductance & Force Factor Non-linearity Induction Field strength

Example of mechanical Non-linearity of Suspension

Example - 3 & 6 volt

Selective Distortion Passive selective resonance Passive selective resonance - Missing gluing - Missing gluing - Litze wire problems - Litze wire problems - Lose voice coil wires - Lose voice coil wires Power & Time critical Power & Time critical K & K International

Example of Selective resonance

Random Generated Distortion -Lose particles in magnetic gab -Lose particles in magnetic gab -Lose parts on membrane, spider or surrounding -Lose parts on membrane, spider or surrounding -Missing soldering -Missing soldering Power & Time critical Power & Time critical K & K International

Example of Random

Wide band distortion Air gab generated noise Air gab generated noise Dust cab missing gluing Dust cab missing gluing Speaker cabinet problems Speaker cabinet problems Port air turbulences Port air turbulences Power & Time critical Power & Time critical K & K International

Example of air-noise

Harmonic Generated Rub & Buzz Rub & Buzz K & K International

Time Related Rub & Buzz K & K International Rub & Buzz

Time Related – Harmonic Rub & Buzz K & K International Rub & Buzz

Practical test parameters Power Power must at a level to detect Rub & Buzz Find best power level regarding power/time if allowed Frequency range Low frequency take time Select start frequency before resonance The test time Start with a relative slow test time & then optimize test time regarding power/time K & K International

Noise problems in a productions environment Electrical Acoustical K & K International

Electrical noise Motors External power devices External transmitters Move instrument wires away from power wires Reduce noise from source Place power device far away from test equipment Be sure no device which can generate noise are active while testing K & K International

Acoustical noise Background noise less than speaker distortion level Environment noise tools - people - information systems - air condition Isolate noise by make use of test boxes Repeat test if test fail by noise? K & K International

The test box Placement of the measurement microphone Frequency range, systems - units Rub & Buzz - use more than one microphone Microphone placement for Rub & Buzz Test of the box Use the instrument as a analyzer Make the measurement in real production environment K & K International

Summary Be careful to select power and test time to optimize Rub & Buzz detection Be careful to select power and test time to optimize Rub & Buzz detection Select microphone(s) on a optimized position Select microphone(s) on a optimized position Be carefully to select a test box regarding environment Be carefully to select a test box regarding environment K & K International

End