“Let our rigorous testing and reviews be your guidelines to A/V equipment – not marketing slogans”
Facebook Youtube Twitter instagram pinterest

Loudspeaker Manufacturers Make their Own Drivers? p2

By

Late 20th Century Drivers

JBL 2213 DriverDuring the 50’s and 60’s, perhaps through the very early 70’s, most of the other aforementioned companies made their own drivers in a similar fashion, depending, of course, on the materials involved. Paper/cellulose woofer cones were pressed and cut to shape, cloth surrounds were cut to shape and treated for porosity-limitation, voice coils and crossover chokes were wound, often by hand. It’s said that AR had a group of women who were so experienced and skilled at assembling AR’s drivers—having done so for many, many years, since the essential characteristics of many of AR’s drivers remained unchanged for almost 20 years—that they could reportedly do this faster and more accurately than any automated process.

That was fine for then, but as new production technology became available, companies found it possible to make larger quantities of drivers with fewer rejects and at lower unit cost.

By the late 1970’s, several companies still made their own drivers, but it had become more of a process of a company assembling their own drivers rather than actually making them.

A very good example of this was Boston Acoustics. BA made virtually all their own drivers (with the exception of a tweeter here and there) from the time of the company’s inception in 1979 right up until the late 90’s or so. First, they had a battery of highly-skilled design engineers, armed with the very latest SOTA computers and programs, like FEA and the like. Once a driver design was done in the virtual world, it was given over to the Transducer Group who would then either assemble prototype drivers from an incredibly comprehensive inventory of parts (cones, domes, magnets, spiders, backplates, voice coils, etc. of every imaginable size and characteristic), or if needed, they’d order in custom parts (the magnet, the cone/surround, etc.) from their roster of specialized vendors and then complete the prototype driver. BA could make just about anything their engineers could design.

Once the project engineer was satisfied with the driver’s performance (and assuming it fit into the overall cost structure of the project’s budget), the driver would then be released into mass production in BA’s factory.

BA had a very sophisticated woofer line, where they’d make every cone driver they used, from the 2 ½” wide-range driver in their computer “cube” speakers right up to the 10” woofers they used in their TOTL home speakers.

But as I said, this was more “assembling” rather than “making.” BA would get baskets from one vendor, cones from another, spiders from a third, voice coils, dustcaps, surrounds, top plates, back plates, magnets (actually, just round hunks of metal with holes punched in them—they’d magnetize them right there on the line) and so on. They had a very impressive custom-designed assembly line, highly automated, that would combine all the various components into a finished driver in very little time. From start to finish, an 8” woofer might take about 5 minutes to go through the entire process, including going through a bake oven to cure and set the adhesives and passing through a QC chamber at the end, where it was swept and its FR etc. compared with the Engineering reference. Workers would then load the completed drivers onto pallets for storage in the raw parts area, until the next Work Order was generated that required that part. The drivers themselves were subject to +/- 1 dB tolerance (a 2 dB window across its operating band) and BA had surprisingly few rejects and therefore enjoyed a commendably low per-unit cost. They used good, consistent parts and the assembly process was very precise and buttoned-down. Quite, quite impressive. (See figure 5.)

 BA cutaway.jpg

Figure 5: Cutaway of BA woofer, 1996

 Their custom tweeter line was even more impressive. This line was sort of like BA’s “Manhattan Project,” very secretive, very advanced. BA didn’t allow factory visitors to take pictures of the tweeter line and they never showed a detailed image of it in any of their literature. It combined either aluminum dome/surround assemblies or textile (they called it “Kortec”) one-piece dome/surrounds with voice coils, Neodymium magnets, the backplate, under-dome felt “button,” and the faceplate with diffuser into tweeters of amazing quality and consistency. BA’s tweeter line was not only highly automated, it was self-diagnostic as well. When the tweeters went through the QC chamber at the end of the line, the readout would not only tell the operator whether the unit was “pass/fail,” but it would also tell them why the unit failed: too much adhesive (resulting in too much mass, for a reduced upper-octave response, or sensitivity too low (possibly from the magnet not being “seated” properly in the yoke) or not enough adhesive (leading to non-linear excursion, so the distortion was too high), etc.

After that particular build, all the failures were analyzed and the line would automatically self-adjust to further optimize the amount of adhesive dispensed, the parts placement motions, etc. so the tweeters got better and better as time passed. Eventually, they were almost flaw-free, +/- 1 dB from 2000-20 kHz. Ruler flat. The tweeters were so good and so consistent that even after BA shifted most of its finished-goods production to China, they’d still make tweeters in MA and ship them over! It was less expensive to do it that way than to QC an incoming all-China shipment and find that 5% of the tweeters didn’t pass. (See figure 6.)

BA tweeter.jpg

Figure 6: Exploded view of BA tweeter, 1994-2003

I don’t know if BA still does that, but they did as late as 10 years ago.

 

Confused about what AV Gear to buy or how to set it up? Join our Exclusive Audioholics E-Book Membership Program!

Recent Forum Posts:

Electrodynamic posts on August 25, 2013 00:34
On a good note, the give-a-way is back in full force. It is not illegal. I will give a way an IB 24" and a BM mkIV prototype woofer to those who donated to the MS Foundation.
Electrodynamic posts on August 25, 2013 00:25
cpp, post: 984233
I was looking at your site and was attempting to pull up the “ About Us” to find out a little more about the company but I can't seem to pull it up.. Using Firefox and Chrome

Odd because I can pull it up just fine using Chrome. http://stereointegrity.com/images/aboutus.jpg
cpp posts on August 24, 2013 07:57
Electrodynamic, post: 984216
My sites have been edited due to your post. There never was a “pay us an you are entered into a raffle”. All proceeds went towards MS research. No amount of money went to the company or myself. And no one who gives/gave to the charitable MS organization will have a chance to get anything from us.

I was looking at your site and was attempting to pull up the “ About Us” to find out a little more about the company but I can't seem to pull it up.. Using Firefox and Chrome
cpp posts on August 24, 2013 07:49
Chu Gai, post: 983753
Electrodynamic, I checked your company's webpage and noticed you're running a raffle with a prize. Unless the laws are different in your state, which you should look into, you have to be a non profit organization with the proper credentials to actually do this. What you probably can do is to run a sweepstakes but then people would not be obligated to purchase anything or make a donation.



Is Your Fundraising Raffle Legal in Your State? | NALS…the association for legal professionals
Electrodynamic posts on August 24, 2013 00:18
Chu Gai, post: 983753
Electrodynamic, I checked your company's webpage and noticed you're running a raffle with a prize. Unless the laws are different in your state, which you should look into, you have to be a non profit organization with the proper credentials to actually do this. What you probably can do is to run a sweepstakes but then people would not be obligated to purchase anything or make a donation.

My sites have been edited due to your post. There never was a “pay us an you are entered into a raffle”. All proceeds went towards MS research. No amount of money went to the company or myself. And no one who gives/gave to the charitable MS organization will have a chance to get anything from us.
Post Reply