Part One – Speaker Design
At first glimpse, speaker design tends to look relatively simple and uncomplicated: the designer seems to have little more to do than select the right combination of drivers and electrical components, mount them in a cabinet which will enhance the sound they create together, and then send the results down to the production department.
However, technically speaking, the task at hand is converting electrical waveforms from an amplifier into acoustical, three-dimensional waves. The challenge is to accomplish this with the least possible distortion. Ideally there should be none. Usually there’s quite a lot. And that’s just the first problem.
The designer is challenged by the materials he must work with. The woofer, from which room-filling bass must come, in reality is generally a fragile paper cone with unpredictable minor movements, pushed by a wound wire moving in the gap of a MAGNET whose magnetic field should be uniform but seldom can be. The tweeter, on which the highest audible frequencies depend, is generally a tiny object called upon to perform the virtually impossible task of emitting sound identical to that which comes from large musical instruments with vast radiating surfaces. And, dividing sounds between woofer and tweeter is the job of an electronic or mechanical CROSSOVER which cannot, by definition, do the job perfectly.
Then there’s the problem of inefficiency. Almost all loudspeakers are notoriously inefficient, producing far more heat than music. Improving loudspeaker efficiency is certainly part of the goal. Large drivers, large magnets, and large enclosures help. However, improvements in efficiency are seldom free. They are usually paid for by narrowing of frequency response (bandwidth). (Bandwidth is enhanced by small drivers and long voice coils; both are enemies of efficiency.) Then there’s the problem of size versus performance. Large boxes give better bass efficiency and power output, but add to the cost of the speaker. Smaller boxes provide better dispersion and frequency response, but without the realism. Designers must therefore constantly compromise between cost and size in commercial designs.
Not only must the designer compromise between size and cost, bandwidth and efficiency. Each time he designs a new speaker, there are scores of factors to be juggled. Theory and math can only be a loose framework. Pure theory has its limits, first, because the rooms in which speakers will eventually be used can only be guessed at, yet will influence frequency response and dispersion, and also because psycho-acoustic factors (how and what the ear hears, how it selects and interprets) have a strong influence on the final sound or “response” of the speaker.
In its painstaking advance towards less and less distortion, successful speaker design requires of its practitioners a thorough grasp of how sound behaves and how the ear hears, but that’s only one prerequisite. A second qualification for success may be an attic or basement or perhaps a back room full of speakers of all sizes and shapes, all unique prototypes, each built with care and the hope that this particular combination of design considerations may be the designer’s finest speaker yet. Some designers seem to build one fine speaker after another, yet often the real secrets of their successful and famous designs derive from many unknown and even unnamed prototypes representing years of effort but now practically forgotten.
Hopefully, what the designer learned from them is not forgotten, so that when you choose a speaker by a good designer, you’re getting more than an enclosure and electronics. You’re also getting a unique blend of design factors and the designer’s experience: a share of the important things learned among the prototypes in the back room.