SPEAKER AND SYSTEM ACOUSTIC MEASUREMENT AND PERFORMANCE DOCUMENTATION CAPABILITIES

We maintain a well equipped loudspeaker laboratory for raw driver and speaker system development. We can perform the following:

• Acoustic measurement of raw drivers and compete speaker systems
• Electronic measurement of crossovers, equalizers and passive filters
• Impedance, both at nominal levels, and at high power
• Speaker power handling tests, up to 2.3Kw RMS (destuctive and non-destructive)
• Competitive product analysis

Our equipment list is constantly expanding, and currently includes:

• Ariel SysID v6.50, FFT measuring system, in dedicated host computer
• Linear-X LMS v3.72, analog measuring system (2 systems)
• Linear-X M51 calibrated microphone (2) and VI-BOX interface
• Neutrik 3300 Audiograph system, 3302 system mainframe with 3312 & 3322 modules
• Neutrik 3382, 6.3mm measuring microphone & phantom power supply
• UREI 2000+2010, X-Y audio measuring system
• UREI 201 pre-amp/sweep modulator (2)
• K&K P730 measurement system, with UA25 interface
• Hewlett Packard 403B, true RMS reading voltmeter (2)
• Hewlett Packard 652A, audio generator
• Hewlett Packard 334A-03, distortion analyzer
• Sencore AA165, AM-FM audio and RF performance analyzer
• AudioSource PNG-1, pink noise generator
• Trinity DR1, pink noise generator
• Numark REF-100, pink noise generator, and 6.3mm calibrated microphone
• Trinity DR4 rev E, cone excursion measuring system
• Realistic 23-2050, sound level meter
• Quest 211, precision sound level meter
• Quest CA-12M acoustic calibrator
• Navone Engineering N-PD-10 polarity checker
• Millbank LZM 1000, 25/70/100v audio test set
• Wavetek DM2, digital multimeter
• Radio Shack 22-215, analog RMS reading multimeter
• EBC 510, high-speed cone motion strobe
• FW Bell 4060, magnetic gaussmeter with PB70-S (1mm) hall-effect probe
• DBX 260, digital loudspeaker management system
• Leader LFG-1310, audio burst and sweep generator
• AKG C451 calibrated microphones (2) with CK1, CK2 & CK22 elements
• Josephson C55H, 6.3mm high output calibrated microphone, and AT power supply
• QSC DCA2033, lab power amplifier
• Crown/Amcron DC300A, lab power amplifier
• ART Studio Linear-1, power amplifier

• JBL/SIA Smaart Pro v5 audio analysis system
• SpeaD v1.03, (Redrock) advanced driver unit design program
• Reverse SpeaD v1.0 (Redrock) iterative drive unit design program
• Bassbox 5, (Harris) low frequency enclosure design program
• Data v1.03 (Scientific Design) Thiele-Small parameter extraction program
• FLDES v1.1, (Sitting Duck) iterative crossover design program
• Fluxcalc, (General Magnetics) magnet topology modeling program
• FG, (LeMarchand) audio function generator
• Gemini v1.01, (Infolytica) boundary element magnetic modeling program
• LEAP v3.10 (ATI) speaker enclosure modeling program
• LEAP v4.65, (LinearX) speaker system modeling program
• LFDES v3.02, (Sitting Duck) iterative enclosure modeling program
• HORN v23, (McBean) horn development software
• PG v1.43, (Kloosterhuis) sine and tone burst generator
• Spconv, (Perception Inc) Thiele-Small to electro-mechanical parameter converter
• SPEAK v1.0, (Earl Geddes) advanced system acoustic modeling program
• SpeakerBox v2.0, (Visaton) low frequency enclosure design program
• SpeakerShop 1.0, (JBL) low frequency enclosure and crossover design program
• Win ISD, (XXX) enclosure modeling program
• Blaubox, (Blaupunkt) low frequency enclosure design program

• EIA 426-B standard disc for power testing
• 'Soundcheck 2' disc for evaluating sound quality
• IASCA test disks, various
• and many others

How we test low frequency components -

We begin by running-in the speaker with pink noise, to exercise the suspension and stabilize behavior in subsequent measurements. Then we use Linear-X LMS, and Ariel SysID measurement systems to establish Thiele-Small parameters. We transfer the data to LEAP and LFDES software to establish the appropriate type and size of enclosure. The driver is loaded into an adjustable-volume lab enclosure, acoustically measured, then auditioned in our listening room. If more than one design is under test, the better candidate is given a complete listening test, using known program material. Back in the lab, we perform SysID spectral contamination (picket fence) tests to examine the drivers' self-noise. This test correlates very well with subjective listening tests, since the drivers with the least eigentones universally score highest in listening tests. After the listening tests, we check excursion using a bias signal to displace the cone, while monitoring a midband sine wave pilot tone util it drops by 3dB. Power handling is determined by raising the power in small increments, until 6% harmonic distortion is reached, indicating the end of a speakers' useful dynamic range, rather than the (less useful) point at which it catches fire. Finally, we test maximum SPL with pulses of increasing power until compressiom reaches 3dB, or the unit shows signs of distress.

How we test other speaker systems, and other drivers -

Since Thiele-Small parameters describe primarily low-frequency performance, full range speakers, tweeters, midranges and complete speaker systems are tested differently. We primarily use LMS and SysID to measure frequency responses in a diffuse, well damped environment, both on-axis and at 15, 30 and 45 degrees off-axis. Individual drivers may be combined with other components and mounted into lab enclosures, to allow listening tests. Complete speaker systems are auditioned in 'as received' condition. tOur second level of listening may use custom designed enclosures. Because of the danger of damage, listening, impedance and spectral-contamination tests are completed before SPL or high power testing takes place. Again, we use the established 6% distortion level as the non-linearity limit.