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vintage homebrew mystery Bozaks

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dumptruck

Lunatic Member
Moved out of my own OT discussion in my own bartertown thread (viewable by subscribers only). I picked these up today from a nice fellow I have not met. He may even be a member here (I never think to ask when I'm busy thinking about new gear). Here's what I wrote about them in my bartertown thread:
Okay, now I've had a chance to inspect. Here's your rundown:

Yeah, I'm 99% sure they are home built. The owner was about to leave on vacation and left them out for me to pick up, so I don't have much info at the moment.

The cabinet sides+top are 3/4" lumber core plywood, which isn't too wimpy but doesn't seem to be very dense and will definitely need some bracing (I don't think there is any). It probably wasn't the best choice, but on close inspection I can tell the rosewood veneer, which is very thick and nice looking, was pre-applied to the plywood, so it was probably chosen for looks.

The edges where you would be able to see the core from the front and sides are finished with strips of solid wood that match the veneer exactly (took me a while to figure out what was going on). The strips are different thicknesses, which is why the front looks the way it does - the front would be totally flat without these strips.

The back, bottom, and baffle are a nice sturdy 3/4" normal plywood, which should help a LOT in making these into something great.

I don't know what the drivers are because I haven't mustered up the patience to unscrew the fifteen 2" flathead bolts holding on each back panel. They don't sound very good, just as the previous owner promised. The surrounds and cones feel pretty brittle - they may have been nice once.

They are filthy, but will clean up to like-new appearance with the exception of a 2"x1" chunk of missing veneer at one corner. I'm pretty pleased overall. I think they'll be getting some legs, though.

P.S. They will be built into essentially ewave deluxe, guess I hadn't mentioned that.
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Now I have removed a back baffle, and the drivers are Bozak. I don't know anything about Bozak. I mean, I know they exist, I know the style, I know the general level(s) of quality, but I don't know anything about what these specific drivers are. The frames seem pretty nice. I can't find a model number. Anybody know them? Sorry about the bad photos, but I don't see anything that seems important that doesn't show up in them.. Oh yeah, two things I forgot to mention from the btown thread is that these are 12" drivers and yes, these cabinets are pretty huge.
 

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The woofer is probably a early 199. But im unsure why it is just a single driver. Unless they had used another cabinet on tip housing other drivers for the upper frequency's. The cabinets look well built. The woofer does a very good job with bass, but as a single driver it wont be kick you in the chest stuff. Let us know what you end up doing.

Econowave?
 
saltwater said:
Let us know what you end up doing ... Econowave?
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Yes, deluxe like I said above, but just as a base for cabinet construction. These drivers are not for me, and I'm not sure they are okay functionally (seem dry/brittle), but I won't toss them in the garbage or anything. Wildly guessing by ear, I'd say they go up to about 10kHz, so it's listenable without any treble help, if not truly full-range. Frequency response above the middle-middle range sounds ragged, and I'm not getting any bass at all. They do sound relatively clean, though.
 
They seem to be generously sized boxes for Bozak 199's, so you should be getting plenty of bass as long as they are sealed more-or-less air-tight. They aren't even remotely full-range, so you will need mids/tweeters to pair them with. I wouldn't be surprised at all if these were originally used with Janszen 130 outboard tweeter units. These come up for sale quite often and would be the ideal add-on for your Bozaks.

http://gallery.audioasylum.com/cgi/...sion=&&moniker=realistico&invite=&w=734&h=950

http://www.martinlogan.com/images/esl-history-janszen.jpg
 
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Measure the interior volume. If less than 5 cubic feet, the cabinet is too small. You can not have too large a cabinet but can too small. From the photo it looks too small. If so, the badd will be severely limited. I have a set of 302s and while not thumoy bass the woofer does get down nice and smoothly. I agree it probably was used in a muti-way system, either a set of JansZens or possibly a set of Jensen soni-domes that I've seenused in combo with Bozaks years ago.

The edge prbably is not brittle as it is cloth pleated and not foam/rubber. There is little excursion when operating.
 
interesting... They are 5.75 cubic feet internally, with a ton of musty fiberglass. They can't be 100% airtight because the input wire goes from outside through a hole drilled in the back.

Judging test tones by ear, they are relatively flat to 4kHz (although there is a bit of a dip at 400 and 700) and then roll off rather smoothly, dropping out at 10kHz (yeah, that's right, exactly where I guessed they did :tongue: ;)).

The bass is rolling off starting around 200Hz. There is output down to at least 40, but far below where you could hear it while playing music. They are effectively silent at 100Hz.

The surrounds feel like old brittle paper instead of stiff doped fabric. I don't know if that's what they are supposed to be like or not, but they definitely don't feel like any other cloth surrounds I have. They are pretty dirty though.. I wonder if that is affecting my perception that they are about to crumble into dust :scratch2:.
 
My first "Econowave" build was with Bozak 199 woofers in 5 cu.ft. boxes. I was very impressed with how real bass guitar sounded with that set up. They were also rather efficient. With your woofers mounted near the top of the cabinet, a small horn sitting on top would be an easy project.
 
Well I could put DE250s on top while they sit around waiting for the woofers I want to use, but they aren't even going low enough to meet my subs' max LP setting (100Hz). Maybe at lunch I'll try adding a resistor for a tube amp damping factor and see what that does.
 
They had paper surrounds. Is there an apon of fiberglas hanging from the top dropping behind the woofer? If not then you should put one in as it should be there.
 
Brian said:
They had paper surrounds.
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Well that explains that. In that case I'm less concerned about them. They do feel similar to aging guitar speakers I have used with paper surrounds, but with a quite bit more excursion which makes them feel closer to cracking.. I'm just going to stop poking them.

No, the cabs are loosely packed with fiber glass everywhere except directly between the driver and the back panel.
 
Well, everything I read seems to say these drivers should have dramatically more bass than I'm getting. There are obvious fixes I could to fix leaks and block resonance, but I don't see anything like that stopping the 200Hz rolloff. I wonder what's up?
 
I wonder what's up?

These are probably 16 ohm speakers, so if you are attempting to drive them with a contemporary AV receiver, the amps may not be able to deal with the load. Try a good old fashioned ST-70 on the 16 ohm taps and see what happens. If you are using the Adcom, well -- I dunno -- they always sounded tinny and light on the bottom end to me no matter what speakers they were used with. Good Luck!
 
They are 8-ohm, and yeah I'm also using the Adcom, 300W+ into 8 should do it. I can assure you that GFA-565 are not weak in the bass dept. Oh well, I didn't intend to use these drivers in the first place. I suppose I should really try out the 2nd one before I put them away though. edit: nope, other one sounds the same. Also, further research indicated they were intended to be used with high-as-possible damping factor, so I didn't bother experimenting with that.
 
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Sorry for shouting but DO NOT DRIVE THESE HARD!!!!!!!!!!!!! They open up with about 30-50 watts rms max and were rated at 100 rms max. Too many got fried from thinking driving them with a megawatt amp would help. I am using a 20 watt rms amp to drive a pair of these in my Symphonys.
 
I am using a 20 watt rms amp to drive a pair of these in my Symphonys
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what amp is that brian? im curious as i will be picking up a set of b4000 symphonys(moorish) on the weekend and always appreciate your input.
 
a quick & dirty simulation earlier today convinced me that the bass problem may actually be the combination of over-stuffing and tons of leaks. I haven't tried a temporary sealing yet, but I will.
 
I haven't opened-up a Bozak in a long time, but iirc, the early ones used a 2"-3" blanket of rockwool or similar on all interior surfaces except the front baffle. I like your idea of adding series resistance and, since you have some serious horsepower available, think you should try it after you seal-up the boxes. Does the other speaker sound/measure the same?
 
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