Enhanced audio quality at compact sizes

Makers continue to improve overall speaker performance, developing smaller models and exploring alternative materials to enhance efficiency.

Speaker

Audio quality enhancements and miniaturization are the development priorities among China suppliers of micro speakers. Makers in particular are gearing up to increase input power and sensitivity while lowering frequency response. At present, most available products deliver 50Hz to 20kHz but many companies are targeting 20Hz to match the requirements of foreign buyers.

Manufacturers are exploring other materials for the diaphragm, which is critical in achieving good sound quality. Mylar, paper and cloth are typically used. The first is the least expensive and easiest to shape. Paper offers a low-cost solution and a more natural sound than Mylar but is more difficult to process once the speaker diameter falls below 30mm. The defect rate may increase as well. Cloth, which changes the frequency response range depending on the kind of fiber, delivers the best sound quality among the three. It has the highest outlay, however, and is therefore usually found in large speakers.

Besides using better materials, suppliers are matching surface patterns with application requirements. These are either concentric or radial, each with distinct frequency response characteristics. Speakers adopting the first design boast a greater output SPL at 5kHz but radial ones are below this figure. The former suits the human voice. The other one is best for music playback.

Diaphragm width is another consideration. Micro speakers with a high input power need one that is thick enough to endure immense loads and strong vibrations. Yet, the broader the width, the lower the frequency response.

In terms of compact size, models from China currently measure 8, 9 and 10mm in diameter. These are designed for mobile phones, earphones, MP3/ MP4 players, PDAs, laptops, video game consoles and toys.

The main challenge for those pursuing miniaturized and lightweight designs is how to raise the input power. The average value is 0.6 to 2W, with the highest reaching 10 to 20W. Speakers for earphones have 3 to 100mW. With maturing technology, companies are able to reduce the defect rate.