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Gerry E.

This is in response to Lance A.'s  Four Year Open Baffle Journey article. Like Lance, I'm a big proponent of OBs. My own pair consists of vintage Western Electric 754A 12-inch drivers on JE Labs-style open baffles with Jensen RP-302 tweeters. I consider the 754A and its 756A 10" little brother (or Altec's 756B) to be amongst the best cone drivers ever made.
I recently received a copy of a 1953 speaker building article that appeared in the Audio Engineering magazine. This article was written by a commander in the U.S. Navy with acknowledgements to an MIT Professor, several Harvard University Acoustic Laboratory personnel including Arthur Janszen and an employee of Bell Telephone Labs, the parent company of Western Electric.

This article gave detailed technical explanations for how to build an unusual speaker system which used four horizontally mounted 12" drivers mounted in separate tall thin wedge cabinets all placed cheek to cheek in an arc and in a corner. As can be seen in the excerpt below, the speaker used the WE 728B or 754A.  However, the Bozak B-199 woofer could also work well as long as it was used only as woofer and augmented by a separate tweeter.
At first I was skeptical about the B-199 woofer but the more I researched it, the more impressed I became with its design and specs.  The B-199 even enjoyed several similarities with the 754A - a special cone material, a special cone shape and a rated response well into the lower treble (40 - 4,500Hz). The person who sent me the article felt that the B-199 would work well on my type of open baffle project.

Still skeptical that a common inexpensive Bozak B-199 woofer would make a decent substitute for the mighty WE 728B or 754A, I went ahead and acquired a pair of 1964 Alnico B-199A woofer units. My cost was $75/pair plus roughly $15 for shipping. At first I merely replaced the left 754A with a B-199A. I wanted to hear how the two drivers would compare in mono by conveniently switching signal from channel to channel.

The first thing I of course noted was the huge difference in sensitivity. The 754A is rated at approx. 99dB so this was no surprise. To get equal channel balance, I needed to set the left channel's stepped volume control up by about 6 to 8 clicks. While the B-199A initially showed promise, it didn't sound nearly as smooth or good as the 754A. However, the 8-ohm B-199A was at a major disadvantage. Not only is my 1.25wpc 45 SET amp underpowered for driving it, it was set to the 4-ohm tap to match the 754As.

I still went ahead and did some critical listening at this point. The sound was too bright because of the major sensitivity mismatch between B-199A and Jensen RP-302 tweeter. I padded the latter down by adding appropriate resistors. With the system balance restored, the B-199As were finally displaying the promise I had sensed earlier.

Of course they were still being driven by the underpowered 45 SET. As luck would have it, I was able to borrow an all-out 2-chassis custom 300B amp.  With good recordings and the 300B amp, the B-199A performed close to the WE 754A. Without performing further A/B comparisons—not exactly convenient when it involves swapping drivers out of open baffles—it would be difficult to call a clear winner between the 45 SET + WE 754As or the 300B amp + Bozak B-199As.  On lesser recordings, the 754As were clearly better however. Why would make for an interesting discussion.

On the plus side, the Bozak B-199A woofer had the edge in bass response.  It has usable output a full octave lower than the WE 754A (approx. 40Hz vs. 80). This is significant because unlike with the WE 754A, I felt no need for a subwoofer. The 754A had the edge in sensitivity (it plays loud with just 1 watt), ultimate midrange smoothness and density and superior transient response. Still, who would have thought that the common and inexpensive Bozak B-199A woofer could make an acceptable substitute for the legendary WE 728B or 754A? There it was buried in a 1953 magazine article. All it took was trying it in an open baffle  A pair of Bozak B-199As on open baffles plus good tweeters could be an all-time speaker bargain. How so? If you're handy, it could be done for as little as $200. Okay? I reckon it'd sound better than anything at 10 times that price or even more.

My 8-watt 300B loaner amp was more than sufficiently powerful and you might be able to get away with less depending on room size and listening levels. The B-199A's lower sensitivity actually had one advantage. With the WE 754A and Altec 756B,  I tested at least a dozen different tweeters both vintage and modern.  I had to reject quite a few on principle because they weren't sufficiently sensitive. That won't be a problem with the B-199A. It should open the doors to a group of lower-sensitivity tweeters such as the Altec 3000, Janszen electrostatic and a number of modern ribbons.

I would have loved to keep the Bozaks and cash out on the 754As. In the end  I just couldn't bring myself to do it. While the B-199A was excellent with my friend's 300B amp, it just did not possess that ultimate smoothness and midrange tone density nor the high sensitivity of the WE 754A. But there was just one tiny thing in its favor. The lowly Bozak B-199A driver demands somewhere between 1/50th and 1/100th of what a 754A commands. That's significant.