Do Loudspeaker Manufacturers Really Make Their Own Drivers?
Among the many things with which audio aficionados use to evaluate the engineering and technical expertise of their favored speaker companies, one thing certainly stands out:
Do they make their own drivers?
Why is this so important to the ardent hobbyist? Why does it seem to be such a bellwether of a company’s engineering bona fides?
The overriding thought is that a truly top-notch speaker company designs such sophisticated and specialized products that only custom-engineered and –manufactured drivers will fulfill the design’s requirements. Perhaps the bass response goals for the speaker are such that no “off-the-shelf” woofer is available that has the requisite low-frequency extension, the power-handling capability and the sensitivity to get the job done.
Likewise, it could be that the design engineer envisions a midrange or treble driver with a very specific set of electro/mechanical characteristics and no driver in readily-available land will do the trick.
But it’s one thing to specify the requirements to an outside 3rd-party fabricator and quite another thing to actually manufacture it yourself. These days it’s quite rare for speaker companies—even the big-name high-end companies—to actually make the drivers themselves in a US or Canadian or UK or Germany-based factory. It probably wouldn’t be an exaggeration to say it just doesn’t happen anymore.
However, the opposite used to be true. Most of the well-known brands actually made their own drivers right in their own factories, and then they assembled those drivers into finished goods, right on site. Some companies even had in-house cabinet-building facilities, so they built the cabinets, designed and built the drivers, assembled the finished speakers, tested them, boxed them up and shipped them out all from the same location.
The cabinet-building capability varied from company to company, but AR, KLH, Advent. Klipsch, JBL, EPI, Allison, Boston Acoustics, KEF, B&W and others were doing their own driver design and assembly right there in their home-based factories. I’ve been on several factory tours and seen the process myself.
AR was justifiably proud of the performance and tight unit-to-unit tolerances of their MA-built drivers. Indeed, for pure FR performance, freedom from distortion, and other important characteristics, AR’s drivers from the late-50’s through the mid-70’s were arguably superior to anything being built back in the day. AR invented the dome driver, and AR’s acoustic suspension woofers (they also invented the “sealed” enclosure as we know it today) had ground-breaking LF extension and low distortion. The AR-3 of 1958 with its industry-first dome midrange and dome tweeter exhibited a remarkably refined, accurate performance, far ahead of the competition of the day. (See figure 1.)
Figure 1: Textbook-perfect AR woofer frequency response, 1954-1974
Image courtesy of Tom Tyson
The difficulty in all this wasn’t AR’s engineering of that period—which was way ahead of its time—it was that the manufacturing processes and materials of the middle of the 20th century were hard-pressed to keep up. Automated, robotic manufacturing was a long way off. Instead, much of AR’s manufacturing was done manually. (See figure 2.) The small dimensions of many of the parts and their incredibly tight QC tolerances led AR to reject a huge number of drivers before they ever found their way into finished goods.
Figure 2: AR-12-inch woofer, mid-1950’s, hand-treated surround
Image courtesy of Tom Tyson
AR used to literally brag about how many drivers they threw away and they pictured that in their advertising (see figure 3.) as a way to demonstrate how high their quality standards were.
Figure 3: AR-12-inch woofer rejects, in trash bins
Image courtesy of Tom Tyson
On a 1976 Boston Audio Society factory tour of the original Advent plant in Cambridge MA conducted by Advent president Andy Kotsatos (known then as Andy Petite), we saw the factory in action. By far the most fascinating part of the tour was the tweeter fabrication process. For those that remember, the Advent and Smaller Advent speakers were two-way designs that used a rather unique tweeter crossing over at a very low (for a two-way system) 1000 Hz. In order to be able to cross over that low, the driver had to have sufficient radiating area such that its sensitivity and air-moving capability would be satisfactory down to that low a frequency.
However, the driver had to maintain adequate dispersion and transient response well into the upper treble ranges.
These seemingly conflicting requirements were satisfied by a custom-designed 2-inch cone driver that became known as the Advent “doughnut” tweeter, because the outer part of the driver resembled the shape of a doughnut sitting on the kitchen counter. The inner part of the doughnut—the dustcap area—was dome-shaped, about 1” across in diameter. But the entire tweeter was one piece, not a separate cone with a separate inner dustcap. To Advent’s credit, they never explicitly said that the “inner dome” section of their tweeter diaphragm functioned like a 1-inch dome tweeter; like much of Advent’s cleverly-written ads and literature during that time period, they let the implication speak for itself. (See figure 4.)
Figure 4: Advent 2-inch “doughnut” tweeter
It was made from a light, stiff cellulose-based material. This was the most interesting part of the plant tour: There was a large vat of liquid “goop,” about the consistency of watery oatmeal. The operator would take what was, essentially, a large ladle and grab a serving of tweeter goop. He would then pour the goop into a press that would form the tweeter into its unique shape. Then, the pressed tweeter diaphragm was taken out of the press and put aside to dry. There were trays and trays of tweeter cones in the factory, ready to be assembled into finished tweeters.
That is making your own drivers.