Bozak B-302A Century Speaker Project!!
- Thread starter hardbop33
- Start date
EQmeat
One of the usual suspects
I have related question which I hoe someone's experience can answer.
I am working on restoring B-302s as well, and I am finding this thread very helpful. Thanks to the OP and the astute contributors.
Unfortunately at this time I only have B209 mids to work with. I know these don't have the great attributes of the B209b. I am wondering what is the best crossover for these drivers. Mr. Tobin has just said don't bother with the inferior paper cone drivers but I don't have any alternative presently.
Does anyone have any frequency range info on the lesser drivers? Or crossover mod suggestions?
Thanks
I am working on restoring B-302s as well, and I am finding this thread very helpful. Thanks to the OP and the astute contributors.
Unfortunately at this time I only have B209 mids to work with. I know these don't have the great attributes of the B209b. I am wondering what is the best crossover for these drivers. Mr. Tobin has just said don't bother with the inferior paper cone drivers but I don't have any alternative presently.
Does anyone have any frequency range info on the lesser drivers? Or crossover mod suggestions?
Thanks
Tensleep - I am just outside of Chicago.
Since My last post I have had more progress with the red wine than with the crossover!
Snagged some terminal strips and alligator clips from a fellow audio cohort the other day and will perform some trial and error this weekend.
I got sidelined with a Bogen B50-16 idler turntable from the 50s. Thought it would make an interesting, semi-portable 78 player. Still working the kinks out. I post on Lenco Heaven occasionally and detail the beginnings of this project for any who care.
Not giving up on the Bozaks - just distracted.
Since My last post I have had more progress with the red wine than with the crossover!
Snagged some terminal strips and alligator clips from a fellow audio cohort the other day and will perform some trial and error this weekend.
I got sidelined with a Bogen B50-16 idler turntable from the 50s. Thought it would make an interesting, semi-portable 78 player. Still working the kinks out. I post on Lenco Heaven occasionally and detail the beginnings of this project for any who care.
Not giving up on the Bozaks - just distracted.
They're Alive!! - Bozaks appear to be providing a balanced, natural sound!
To review, soldering up my first crossover according to the 101T schematic, or at least how I deciphered the schematic (see above pic), resulted in weak, inarticulate (bloated) bass, mildly harsh tweeter, and a non-existent midrange - kind of like a hole in the middle of the sound kind of thing.
A friend suggested to me to try swapping the wire leads to each of the
drivers before dismantling the entire crossover. Something about a driver being possibly out of phase? I thought what the heck! (Note - the closeup pics of the crossover were taken before hooking up the drivers to the crossover.)
I first tried to swap the 1 & 2 (red & green) wires coming from the woofer to the B199A terminal - all that resulted from the bass going away and gaining nothing in return. Strike one.
I then swapped the 1 & 2 wires coming from the midrange to the B209B terminal - which appeared to have no effect on anything - midrange did not seem to emit any sound and the woofer and tweeter seemed unaffected. Hmmm?
I then swapped the 1 & 2 wires coming from the tweeter to the B200Y terminal and - voila! - the bass became tighter and deeper, the tweeter less harsh and the hole in the middle seemed to disappear!
To be honest I am not 100 percent I have the crossover and speakers wired correctly. Maybe its because I am not used to a speaker simultaneously presenting a deep and rich, yet balanced and natural sound.
After playing a few sides with a huge grin on my face I noticed that I had left the 1 & 2 wires coming from the midrange swapped! I returned them to their original position and the sound got a little better, though not dramatically.
I put a couple of pics of the first crossover (with soldered joints) along with the second crossover (alligator clips). I tried to wire them up exactly the same.
If anyone notices something funky or has any suggestions please post it.
You'll notice in the pictures that the tweeters are simply resting on top of the speakers, under a bit of foam sheeting. I opted to drill a 5/8" hole in the tops of the speakers to act as a pass through for the tweeter wiring. This hole also allowed me to place the crossovers on top of the speakers and route the midrange and woofer wires as well.
In non-crossover tweaking, I opted to install a 3/4" thick plywood bottom inset within the base of the speakers. This gave me a little bit more weight, tightened up the base, and most importantly allowed me to put casters on the speakers. All of this is reversible too. Although some here might cringe at the thought of putting casters on a set of speakers I need to be able to wheel them about on my concrete floor and my basement has flooded a little in recent months.
Thanks!
Troy
To review, soldering up my first crossover according to the 101T schematic, or at least how I deciphered the schematic (see above pic), resulted in weak, inarticulate (bloated) bass, mildly harsh tweeter, and a non-existent midrange - kind of like a hole in the middle of the sound kind of thing.
A friend suggested to me to try swapping the wire leads to each of the
drivers before dismantling the entire crossover. Something about a driver being possibly out of phase? I thought what the heck! (Note - the closeup pics of the crossover were taken before hooking up the drivers to the crossover.)
I first tried to swap the 1 & 2 (red & green) wires coming from the woofer to the B199A terminal - all that resulted from the bass going away and gaining nothing in return. Strike one.
I then swapped the 1 & 2 wires coming from the midrange to the B209B terminal - which appeared to have no effect on anything - midrange did not seem to emit any sound and the woofer and tweeter seemed unaffected. Hmmm?
I then swapped the 1 & 2 wires coming from the tweeter to the B200Y terminal and - voila! - the bass became tighter and deeper, the tweeter less harsh and the hole in the middle seemed to disappear!
To be honest I am not 100 percent I have the crossover and speakers wired correctly. Maybe its because I am not used to a speaker simultaneously presenting a deep and rich, yet balanced and natural sound.
After playing a few sides with a huge grin on my face I noticed that I had left the 1 & 2 wires coming from the midrange swapped! I returned them to their original position and the sound got a little better, though not dramatically.
I put a couple of pics of the first crossover (with soldered joints) along with the second crossover (alligator clips). I tried to wire them up exactly the same.
If anyone notices something funky or has any suggestions please post it.
You'll notice in the pictures that the tweeters are simply resting on top of the speakers, under a bit of foam sheeting. I opted to drill a 5/8" hole in the tops of the speakers to act as a pass through for the tweeter wiring. This hole also allowed me to place the crossovers on top of the speakers and route the midrange and woofer wires as well.
In non-crossover tweaking, I opted to install a 3/4" thick plywood bottom inset within the base of the speakers. This gave me a little bit more weight, tightened up the base, and most importantly allowed me to put casters on the speakers. All of this is reversible too. Although some here might cringe at the thought of putting casters on a set of speakers I need to be able to wheel them about on my concrete floor and my basement has flooded a little in recent months.
Thanks!
Troy
Hi Troy,
Sorry I haven't checked back for a while. Sounds like you may have discoverd, what I've read has been the case sometimes, that some of the drivers are wired out of phase on the factory crossover. Remember too that there is a jumper that should be changed. Also, it looks like you have the 8.2uf cap on the wrong side. It should be on the amplifier side, not on the driver (tweeter) side. In other words, it should be "before" the 2uf cap and the two resistors, not after them. It's hard to tell from the pictures if everything else is correct, but that is one thing I can see that doesn't look right.
Sorry I haven't checked back for a while. Sounds like you may have discoverd, what I've read has been the case sometimes, that some of the drivers are wired out of phase on the factory crossover. Remember too that there is a jumper that should be changed. Also, it looks like you have the 8.2uf cap on the wrong side. It should be on the amplifier side, not on the driver (tweeter) side. In other words, it should be "before" the 2uf cap and the two resistors, not after them. It's hard to tell from the pictures if everything else is correct, but that is one thing I can see that doesn't look right.
Gang-Twanger
Resident Wharfedaliophool
The medium-sized Bozaks are on my bucket list. The CG's and Symphonies won't work well in my smallish room, but I'd like to try one of the medium-sized models and see how they do in my place (This is why I like Wharfedales... Even their biggest models work in a small room). I've heard Bozaks before, but I've never owned a pair. Like someone said, Bozak sure knew how to make some damn-good drivers (as did Wharfedale).
I spent a lot of time today messing with this crossover and think I've got a lot of it figured out now after digging through AK, the Yahoo Bozak group, eBay pictures of crossovers, and Steve Hoffman forums. It took a while, but ultimately paid off well.
Back in Post #24 there was a concern about the sound and I noticed a wiring issue. It appears that the poster has wired both legs of the circuit together in one leg and left the inductor out of the other.
If you look at the yellow arrows in the pic below you can see that the big cap is wired correctly to the #1 terminal for the 209B, but it also has the reversed jumper from the inductor still attached; that should have been moved to the #2 terminal, which looks like it's connected straight back to the #2 input. The OEM comes with the inductor on #1, and cap on #2. The 101T/104T shows cap on #1 and the inductor on #2. Reversed.
Also, it seems to me that the coils have lugs for different values. There was no need to buy a 3.0 mH coil as that value is available by moving the wire up to the higher lug on the "B" terminal strip.
Back in Post #24 there was a concern about the sound and I noticed a wiring issue. It appears that the poster has wired both legs of the circuit together in one leg and left the inductor out of the other.
If you look at the yellow arrows in the pic below you can see that the big cap is wired correctly to the #1 terminal for the 209B, but it also has the reversed jumper from the inductor still attached; that should have been moved to the #2 terminal, which looks like it's connected straight back to the #2 input. The OEM comes with the inductor on #1, and cap on #2. The 101T/104T shows cap on #1 and the inductor on #2. Reversed.
Also, it seems to me that the coils have lugs for different values. There was no need to buy a 3.0 mH coil as that value is available by moving the wire up to the higher lug on the "B" terminal strip.
Attachments
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Yep, the inductors are tapped for different values. Part of ol' Rudy's "one basic crossover that can be made to do anything" concept. Send me a PM with your email address and I'll shoot all of my relevant documentation over to you to make sure you have everything I've found.
serioushifi
New Member
Could use some help with (Tobin 104T mod)
I have a pair of Bozak 302A Century speakers that I want to modify the crossovers with the Tobin 104T mod.
Bought caps & resistors, but do not read a schematic well.
Tried looking at others' pics but most are of the 101T mod, not the 104T modification.
Could someone send me pics of their 104T mod or perhaps give me a step by step guideline of the cap & resistor connections?
Sorry for being a novice.
Am I correct in understanding that I can change the 1.6 coil into a 3.0 coil, simply by changing the wire from the B terminal N-101 connection, to the B terminal N102/104 connection?
Finally, where do I connect this "jumper" people refer to?
Any help would be greatly appreciated!
Thank you, Brent
I have a pair of Bozak 302A Century speakers that I want to modify the crossovers with the Tobin 104T mod.
Bought caps & resistors, but do not read a schematic well.
Tried looking at others' pics but most are of the 101T mod, not the 104T modification.
Could someone send me pics of their 104T mod or perhaps give me a step by step guideline of the cap & resistor connections?
Sorry for being a novice.
Am I correct in understanding that I can change the 1.6 coil into a 3.0 coil, simply by changing the wire from the B terminal N-101 connection, to the B terminal N102/104 connection?
Finally, where do I connect this "jumper" people refer to?
Any help would be greatly appreciated!
Thank you, Brent
tensleep
Addicted Member
I received and replied to your pm and sent you an email, Brent! My work week and evening schedule is pretty full this week. It may be the weekend before I can really get into this circuit again. Others here can certainly help you as well. I may go ahead and order some parts to modify my second set of crossovers and do a step by step with pictures and text.
Check out this post for info on the coils and the reverse phase
http://audiokarma.org/forums/showpost.php?p=8503665&postcount=30
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Steven Ver
Active Member
I just bought a pair of one owner Bozak B302a in cherry French provincial cabinets. Same family for 60 years and working fine (seller claims) I plan on powering them each with a Bogen Db130 mono amp. What should I know before hooking them up....crossovers need rebuilding? Dangerous to use without new caps? Comments appreciated!
quiet
Addicted Member
I have the 302A's. I like them. Used parts are easy to get, so plug and play.
Retrovert
Addicted Member
I suggest you search for "Bozak Tobin" to find the necessary modifications, detailed in other threads.
Rebuild the crossovers or the sound will be muddy and distorted. Numerous threads here explain how to do that.
Move the woofer-midrange crossover point from 800 Hz to 400 Hz. (Tobin.)
Tame tweeter impedance rise, add attenuator. (Tobin and my L-pad mod.)
Cover the midrange with a flower pot. My postings on that explains how removing cross-modulation between midrange and woofer cleans up the sound. Then you're good to go. (My mod.)
Any Bozak 60 years old may have two other issues: (a) paper-cone tweeters (shiny dustcaps) which should be upgraded to aluminum cone, (b) paper-cone midrange which should be upgraded to the aluminum cone B, Bc, or C variety but never to the A variety (my postings explain why, but the A has ringing and requires a special damping foam ring which has turned to dust and is not replaceable).
Adding to this four year old thread to try to be helpful. I just found a pair of B-302a. Urban cabinet. The drivers are B-209Bc, B-199Bc, B-200Yc.
I don't know what the lower case "c" is about on the driver label since I never see it in any posts on any forum. Also they seem to date from later than "the early 60s" that the seller mentioned.
The "Yahoo Bozak group" mentioned is now https://groups.io/g/BozakSpeakers
The grilles have three screw on the underside of the top trim, and three more on the underside of the front of the cabinet. I would caution that after removing the screws also gently off the Bozak badge on the lower right corner. It has pegs on the back. You don't want it to tear a hole in the fabric when removing the grille.
There are four wood screws on each side of the back off. The back is not light masonite, it is maybe 1/2" solid plywood. It is a tight fit, so the cabinet is well constructed. Once the 16 screws are out I used an awl bent into a hook shape at the end to fit into a screw hole and pry it out enough to get a grip to open it.Turn your amp off first, so removal of the back doesn't accidentally cause a short at the speaker terminals.
One thing I noticed when I took the grille off and listened to a frequency sweep test record was distortion from the woofer. So with no music I gently pressed the woofer cone and heard rubbing. I learned that the cones could sag over the decades. So from the back I removed the eight 8-32 nuts around the woofer circumference. The head of those bolts is in the front of the baffle, with wood caps to retain them. Not the four nuts holding the woof basket together. Then I rotated the woofer 180 degrees to counter the suspected sag, and now there is no rubbing! There was plenty of wire slack to do this, but remove the tweeter wires from the wire clamps on the woofer basket before doing this.
I do have a mystery. When I play the phasing track on my test record, which uses a Fender bass guitar, I get the wrong answer. That is, when I should hear the sound centered, it is dispersed, and when the test record says it should be diffuse, the guitar sounds like it is directly in front of me. So I reversed the leads on one speaker and the test record is now heard "correctly". Honestly the music sounds good, but different, with one speaker connected either way. I am presently listening with one speaker cable reversed. I am not new to vintage audio, so yes I checked the phasing test LP with another set of speakers, and yes I checked the wiring from turntable to pre-amp to amp to speakers. The sound stage seems wider with the one speaker's leads reversed.
I don't know what the lower case "c" is about on the driver label since I never see it in any posts on any forum. Also they seem to date from later than "the early 60s" that the seller mentioned.
The "Yahoo Bozak group" mentioned is now https://groups.io/g/BozakSpeakers
The grilles have three screw on the underside of the top trim, and three more on the underside of the front of the cabinet. I would caution that after removing the screws also gently off the Bozak badge on the lower right corner. It has pegs on the back. You don't want it to tear a hole in the fabric when removing the grille.
There are four wood screws on each side of the back off. The back is not light masonite, it is maybe 1/2" solid plywood. It is a tight fit, so the cabinet is well constructed. Once the 16 screws are out I used an awl bent into a hook shape at the end to fit into a screw hole and pry it out enough to get a grip to open it.Turn your amp off first, so removal of the back doesn't accidentally cause a short at the speaker terminals.
One thing I noticed when I took the grille off and listened to a frequency sweep test record was distortion from the woofer. So with no music I gently pressed the woofer cone and heard rubbing. I learned that the cones could sag over the decades. So from the back I removed the eight 8-32 nuts around the woofer circumference. The head of those bolts is in the front of the baffle, with wood caps to retain them. Not the four nuts holding the woof basket together. Then I rotated the woofer 180 degrees to counter the suspected sag, and now there is no rubbing! There was plenty of wire slack to do this, but remove the tweeter wires from the wire clamps on the woofer basket before doing this.
I do have a mystery. When I play the phasing track on my test record, which uses a Fender bass guitar, I get the wrong answer. That is, when I should hear the sound centered, it is dispersed, and when the test record says it should be diffuse, the guitar sounds like it is directly in front of me. So I reversed the leads on one speaker and the test record is now heard "correctly". Honestly the music sounds good, but different, with one speaker connected either way. I am presently listening with one speaker cable reversed. I am not new to vintage audio, so yes I checked the phasing test LP with another set of speakers, and yes I checked the wiring from turntable to pre-amp to amp to speakers. The sound stage seems wider with the one speaker's leads reversed.
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Hey Woggles,
Welcome to AK. The c is for a ceramic magnet vs alnico magnet. Not sure what's going on with all your phasing issues. 1 is negative, 2 is positive. In the mid 1960s Bozak reversed phase on mids. That's easily identifiable and remedied. All your other drivers? No idea!
Biggles
Welcome to AK. The c is for a ceramic magnet vs alnico magnet. Not sure what's going on with all your phasing issues. 1 is negative, 2 is positive. In the mid 1960s Bozak reversed phase on mids. That's easily identifiable and remedied. All your other drivers? No idea!
Biggles
mitchalee
Active Member
Yeah, I expected the same thing. But the fact is that the dispersion and the loudness of the tweeters work best off center. I found them much too bright and searing pointed right at me. But at about knee height-- yes, I did raise them up some by putting he whole thing on casters like all my BIG EV, Klipsch, and now Bozak loudspeakers--they sound about right. Also the imaging is MUCH better with the tweeters directly in front of the woofer. Now mine has nothing in the top hole. I've been told some had a midrange there. No idea if that is historically accurate; but if so what a weird arrangement that would be!
Also, oddly I find this Bozak to be particularly well suited to Jazz from before the 60s and mono vinyl records. Frankly, I much prefer the Cornwall and the EV Regency for 60s stereo and nice Columbia Six Eye records. But this Bozak beats them all with early Ellington, Parker, Armstrong, combo jazz, and big band vocal tracks.
It does have a very particular sound with almost too solid upper bass down to about 40 Hz and nicely defined brass and VERY defined reeds. I am not fond of strings on this Bozak. They are a bit too hard and opaque. But every speaker has a weakness. And this Bozak is very enjoyable!