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RE: THE BOZAK GUY SPEAKS

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In Reply to: RE: THE BOZAK GUY SPEAKS posted by Pat Tobin on January 09, 2008 at 21:06:26

I'm wondering...You make reference to the early 60's as the time that Bozak made the "compromising" changes. Does that mean that all Bozaks made after this time have the "brightness hump", or was it confined to certain models? Was the change ever reversed?
I ask because I have a pair of Symphony's made in Nov. 1968 that have had thier caps replaced and I think they sound very nice.I've never been aware of any undue brightness, as you decribe. The mid-range, reproduced by the B-800 driver, is very smooth. Should I be concerned that I'm not hearing the "genuine" Bozak sound?

Edits: 01/10/08

Follow Ups:

RE: THE BOZAK GUY SPEAKS - Pat Tobin 12:49:23 01/10/08 (0)
*"I'm wondering...You make reference to the early 60's as the time that Bozak made the "compromising" changes. Does that mean that all Bozaks made after this time have the "brightness hump", or was it confined to certain models? Was the change ever reversed?

I ask because I have a pair of Symphony's made in Nov. 1968 that have had thier caps replaced and I think they sound very nice.I've never been aware of any undue brightness, as you decribe. The mid-range, reproduced by the B-800 driver, is very smooth. Should I be concerned that I'm not hearing the "genuine" Bozak sound?"*

I should have been more clear about that. The mid-high hump is worst in the 302A, single woofer 3-way 'basic' systems.

The key fact here is that B-200Y aluminum-cone tweeters are 9 dB louder than the woofer(s) and midrange(s). However, they roll off gently above 10 kHz.

In the big 2 or 4 woofer systems, Bozak chose to bring in the tweeters an octave or even two above the nominal xover frequency with the midrange. This is because the B-209B aluminum-cone midranges do not begin rolling off at the nominal 2,500 Hz. They sing along quite nicely up to 10 kHz. Bringing in the tweeters at 5,000 Hz or even 10,000 Hz in some cases, reduces the doubling of the lower range of the tweeters with the extended upper range of the midrange. This lessens the midlle-high hump compared with the 302A's. But the tweets still roll off gently above 10 kHz.

The disadvantages are that the output from the extended upper range of the midrange is more directional and has lesser transient response than the light tweeter diaphragms.

The situation is a little different with the early Symphonies which have the B-800 8" midrange. That midrange does not have quite the bright upper end as the 'standard' B-209 midrange. So there was less doubling with the tweeters and not so much of a middle-high hump.

But none of these variations yield the flat, extended top end that occurs with the right xover mods. It is a credit to Bozak that, even with these built-in 'flaws,' the sound is still considered great by many. But if you heard them 'right,' the improvement is amazing.

Sorry this got so long, but it represents years of my investigations and Bozak developments.

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