You can DIY! Build an Audio Dummy Load

An audio load is an essential piece of test equipment for any audio electronics workshop. Having created the very popular Heathkit ID-5252, more than 35 years ago, Gary Galo decided to design a new option for everyone to build now. The ID-5252 contains four 8Ω, 60W power resistors. The biggest limitation of the Heathkit load is power handling. Series and parallel combinations can be used to produce various resistances and power levels — up to 240W at 8Ω, using all four resistors. But, simultaneously testing both channels of a high-powered amplifier requires two ID-5252 units. Fortunately, the raw parts for building an audio load are easy to find.

This Test Bench is about Celestion's CDX1-1447 1” ferrite motor compression driver coupled with Celestion’s H1-7050 ‘No Bell’ 70° × 50° horn. Features for the CDX1-1447 include a one piece polyimide diaphragm and surround, with an exit (throat) diameter of 25.4 mm (1.0”). The horn is a new and rather innovative design. The H1-7050 “No Bell” is a cast-aluminum exponential flare-type horn with a 70° × 50° radiation pattern. This article was originally published in Voice Coil, March 2017.

Test Bench of the HF142 1.4” neodymium motor compression driver with the LTH142 60° × 50° horn, from Italian pro sound OEM FaitalPRO. Features for the HF142 include a ketone polymer diaphragm, with proprietary perforated suspension for acoustic tuning and a Finite Element Analysis (FEA) modeled and optimized four-slot annular phase plug. The phase plug’s design and its coupling with the diaphragm uses Faital’s proprietary simulation / modeling software. This article was originally published in Voice Coil, March 2017.

audioXpress March 2017 featured a thorough review by Stuart Yaniger of Audio Precision’s new APx1701 Transducer Interface. This compact solution, when combined with an APx500-series analyzer, creates a test center suitable for measuring speakers, headphones, and microphones, as well as electronics. As Stuart Yaniger finds out, the combination of the APx1701, an APx515 and APx500 software, provides an extremely comprehensive and convenient multi-functional measurement test center.

The March 2017 edition of Voice Coil is now available. Read everything you need to know about the 2017 ALMA International Symposium And Expo (AISE). Read Christopher J. Struck's Technical Notes on Equal Loudness Contours and Mike Klasco's Spotlight on Engineering Simulation Software for speaker design, which includes a directory of software manufacturers. This month's Test Bench, characterizes two new compression drivers from FaitalPRO and Celestion.

A long-standing tradition, audioXpress' Focus on Test and Measurement 2017 is now available. Start with a thorough review of Audio Precision’s new APx1701 Transducer Interface; explore the DIM-100 device for interfacing and measuring with sound cards; build an Audio Dummy Load; learn how to measure Harmonic Distortion and discover the effects of Community Noise and their measurements. And just how good TIDAL's streaming quality actually is? All that and more in audioXpress March 2017. Get your copy now.