There is another issue of excursion which is commonly misunderstood. A subwoofer has a mechanical limit which it cannot exceed without mechanical damage and aberrant cone flex and modulation. This is the greatest factor in sound pressure level as cone area multiplied by excursion is directly proportional to the volume output. When a typical subwoofer system reaches its mechanical limits this is commonly heard as a sharp clapping or clicking sound which is the voice coil former making contact with its magnetic plate. Usually this will deform and damage the coil, but not always. No Shadow Works Subwoofer can ever make contact with its rear magnetic yoke plate. Even at the suspensions mechanical limit, damage is prevented by the safety buffer zone built in to every Shadow Works Subwoofer. The problem is at maximum mechanical excursion, distortion figures will be greater than 5% which is not acceptable for accurate sound quality. All suspension systems are progressive types and require much more power than each subwoofer is rated at. There is always a certain frequency and power level that will allow a subwoofer to reach its maximum limit very quickly so the enclosure is of great importance to each subwoofers power handling ability and more importantly, its perceived sound quality. All suspensions are made from the best quality parts available today, with very consistent batch quality for great pair matching ability.

Linear Excursion

Linear travel is the most important factor for accurate sound quality. Many subwoofers today boast 3 inch excursions, this may sound impressive but for fidelity and sound quality they will not be accurate in their usable range. Such an excursion cannot cover all other frequencies that are demanded from music. If the 3 inch excursion is at 32Hz signal and at the same time there is a 85Hz signal there is a conflict in which the larger low frequency excursion has to take precedence. The other higher frequencies are broken up and distorted vividly as it struggles to overcome the high exertion of the low note.

The old fashioned way to measure excursion was with a strobe light but with modern laser interferometry and the latest generation of new Heterodyne and Homodyne interferometry, the cone motion is measured in more ways than just positive and negative cycles The typical boast of other companies subwoofers is large cone travel but at what cost? Why do the best drive unit makers in the world not have these magical excursion figures? A sine wave and pure tone only gives us half a picture as music has many complex harmonic frequencies and tones which are vastly more complex than any test signal from any oscilloscope. With interferometry we can measure the standing waves and resonances in the diaphragm at very large excursions which shows us a multitude of distortions that can be easily analysed. The main reason for distortion is the acceleration and gravity effect on each positive and negative cycle places huge stress on a very thin cone membrane. Forces higher than 50 G can be placed on a cone, distorting its shape and producing resonance. Newton’s second law states, A=F/M or F=MA, so a 200 gram cone can have the force of 10,000 grams at the maximum of each cycle. No matter how strong the material is, a cone will flex with this amount of force as it changes direction as rapidly as 100 times per second. The greater the cone travel, the less linear the cone motion becomes as the suspension system flexes and the voice coils torque in the magnetic gap. Very strong magnets and dual spider dampers are needed to control this motion for a clean piston line of cone travel. The new fashionable tall surround systems are very poor for linear travel as they offer very little linear control but allow for a larger cone area and greater travel. This does not promote sound quality as larger cone travel only gives large sound pressure. It does not mean more quality, in any sense we can measure or hear.

Quality is not about loudness, is it about grace, control and Character.