Birth of a Classroom Speaker

Birth of a Classroom Active SpeakerChallenge - to design an active speaker system for interactive whiteboards that meets the needs of a classroom to a demanding target price.

We researched the acoustic qualities expected of an average UK classroom, which was not good being a 10 metre by 6 metre room often with concrete floor and walls with windows on one side and full of desks and children. The distance from the whiteboard to the rear of the class was typically 6 metres and average background noise level of around 60dB, mostly expected from the pupils. Research suggests that the signal to noise ratio needed to be at least 15dB above the general noise level. So we were looking to design an active speaker system that was loud enough to be heard, could amplify different sources from the teachers equipment and stand up to the “rough and tumble” of a classroom environment.

We tried and tested two “off the shelf” models but neither the product or the suppliers met our design criteria or quality standards, one sample failed on extended testing and neither were really suitable for the classroom. Our normal manufacturer was a large producer for Walmart which meant they would only be interested if the production volumes were high but they had the production engineers and quality systems to get our new product into manufacture. The product had to be a winner in the market place if this factory was involved.

The design progressed with a 30 Watt amplifier in crystal white wood speaker cabinets, steel speaker grilles, special security wall brackets and a wired remote control so that the teacher could control the unit without climbing up a chair to adjust the volume. When we tested a prototype in an anechoic chamber the sound levels at the speaker at 1 metre were just right but at 6 metres the sound level was a little low, were our calculations wrong?. Then it struck me that a classroom was nothing like an anechoic chamber with special sound absorbing walls. We tested again in a classroom with concrete floors, walls and ceiling of the right dimensions. The result a resounding success and the choice of speaker cone and wood cabinet paid off with a >75 dB sound level and a better than expected frequency response at mid-range ideal for voice reproduction.

The price was right, the product was right and the market was just ready. We couldn't find a competing speaker with all the classroom features that we had built-in at anything like our price. The product proved a great success, sales exceeded 20,000 units in the first year which met the factory minimum production runs and the quality levels were better than 99% AQL. By end 2010 the EA015 wall mounted active speaker system had been installed in more than 150,000 classrooms around the world. The pangs of birth had produced a powerful player for us.       

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