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Sorta Bozak Urbans

caferacer59

caferacer59

Active Member
Hello Forum folks. I picked up a pair of Bozaks with home made cabinets. I dragged them home and as expected they aren't singing yet. Very average sound. I have been reading up and hava a couple of questions regarding these guys.

1. the cabs are made of plywood and are filled with fiber glass insulation. I plan to pull that out and use cotton Batting on all interior surfaces. The cabs have the same dimensions as my friends Urbans so they seem satisfactory on that front. I will also use cotton batting to create the curtain and also do the flower pot mod to the mid.

2. These speakers were manufactured in 1962. There are a pair or tweeters that are not (i do not think the aluminum ones. Is it that much of an upgrade to replace those? The mids are also paper cone, the look to be in very nice shape. Any opinions on the earlier speakers welcome.

3. The cross overs are the n-10102's and the connections say, b-200x tweets, B209a, and b 199a, so that indicates the ealier ones too, is that correct.

4. Does anyone on anybody that sells the Tobin crossovers competed? I dont even own a soldering iron.

5. I have heard not to even bother rebuilding the 10102, I assume thats the consesus.

6 in regard to the cabinets, How air tight to they need to be? and how much of a difference does perhaps a minor air leak make.

7. they sound ok at lower volume, at higher volume they are awful, especillay the mids, I am hopefull that is all about the crossovers.

8. lastly, they do not go as loud as I would have suspected, i am using a HK twin power I borrowed, and my speakers are KG-4, they drive those perfectly, I kinda assumed that these are about as efficient, might be wrong.

Anyways thanks in advance, my buddy has a pair that I fell in love with, these are a mile away from sounding like those.
 
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Hay,
I would suggest you pass those along. You're going to need to do a lot of work, plus get the newer aluminum tweeters, maybe the mids. It'd just be easier to start with a later pair with those drivers already in there. The only thing you'd be keeping are the woofers n inductors on the crossovers.

Biggles
 
Mr. Biggles, I know I know, but I have been looking forever and what's out there has never been close and folks seems to (like me) have caught onto the Bozaks.

Importantly, based on being Married and wanting to stay that way, and with two kids in private school, plus the mid life crisis 911 (used) I bought and the fact that I actually got them into the living room once my wifes shock at the size was overcome, well lets just say, I gotta run what i brung. I found 4 tweets for 100 so i'll get those. and I can do the batting and the flower pot and sealing of the cabinets as well as the aestetic stuff such as new speaker fabric and sand and paint for the cabs.

I would love to find pre built cross overs, do they exisit or is any one out there that takes on these things for hire. If not I will do it, though ive never held a soldering iron in my life.

I have def seen that the tweets need to be the later ones, what the deal with the mids?, I didnt realize they may get short shrift too.

even if I spend a few bucks more than i should, I beleive i can get these guys there. My close freind as a pair, that I told him about if you can believe it, several years ago. I listen to them all the time, I know for a fact that if I can match his sound, then I have arrived at my last set of speakers. I love the sound of bozaks.

PS, l love reading your stuff. and a guy named retrorvert.
 
The paper drivers are poor at best. You really want the Aluminum drivers and to rebuild the crossovers lowering the mid crossover to 400 HZ after switching the mid and tweets installing the Tobin mod.
 
We can get you there, and you can get your pair singing perfectly. Go over to to Facebooks Bozak users group and ask around for someone to build your crossovers for you. Consider that done. Ask for the mids too, you'll find then. You've got this.

Biggles
 
caferacer59 said:
Mr. Biggles, I know I know, but I have been looking forever and what's out there has never been close and folks seems to (like me) have caught onto the Bozaks.

Importantly, based on being Married and wanting to stay that way, and with two kids in private school, plus the mid life crisis 911 (used) I bought and the fact that I actually got them into the living room once my wifes shock at the size was overcome, well lets just say, I gotta run what i brung. I found 4 tweets for 100 so i'll get those. and I can do the batting and the flower pot and sealing of the cabinets as well as the aestetic stuff such as new speaker fabric and sand and paint for the cabs.

I would love to find pre built cross overs, do they exisit or is any one out there that takes on these things for hire. If not I will do it, though ive never held a soldering iron in my life.

I have def seen that the tweets need to be the later ones, what the deal with the mids?, I didnt realize they may get short shrift too.

even if I spend a few bucks more than i should, I beleive i can get these guys there. My close freind as a pair, that I told him about if you can believe it, several years ago. I listen to them all the time, I know for a fact that if I can match his sound, then I have arrived at my last set of speakers. I love the sound of bozaks.

PS, l love reading your stuff. and a guy named retrorvert.
Click to expand...
You’ll do great, now that you are committed to the effort. I’d be happy to help you with the crossovers. I can (as others can) walk you through rebuilding (recapping) your existing crossovers. You can PM me if interested and we can explore other options if you’d like. BTW, I am a student of the @drbiggles and @Retrovert school of Bozak!

You got this!

Regards,

Smiley
 
Based upon your description of the raw material and your skillset this sounds like very bad project for you.

A great deal of expense and effort will be required to line the cabinet and properly construct the curtain. Both may not succeed if you do not have the requisite expertise.

The cabinets may be too thin, or too loosely joined, to not have vibration or resonance issues. The baffle layout may be inappropriate.

The paper-cone tweeters have poor frequency response. I suggest looking into my super-tweeter modification. But if you cannot solder, that may be an additional expense.

The paper-cone midranges likely are better than many contemporaneous drivers for that era, but you are looking at additional expense for replacements.

As far as sealing, I have elsewhere explained that a perfectly sealed cabinet is a barometer:
###
As has been noted, some leakage is required for the cabinet to properly function. In acoustic suspension the pressure is the restoring force, but that does not mean that a perfect seal is desirable.

Here's what I previously wrote on that subject of sealed cabinets, in addressing infinite baffle and acoustic suspension, and why a bit of air movement is required:

Perfectly Sealed Box

When any sealed box, be it infinite baffle or acoustic suspension, is perfectly sealed then the air pressure internal to the box differs from the air pressure external to the box. The interior cabinet air would be trapped at the time of manufacture, and its volume fixed. As a result, as the external pressure increased or decreased the cone would be moved in or out, changing its resting position. This is how a barometer functions.

Air Exchange

To avoid having the resting position vary with air pressure — air pressure varies with altitude and with storms, so it constantly changes, which is how a barometer works — every cabinet must therefore have a means to permit air exchange between the interior and exterior. The mechanism of exchange must be small to avoid having the backwave exit through that orifice and thus (a) (in infinite baffle and acoustic suspension) interfere with the front wave or (b) (in acoustic suspension) reduce the restoring force on the woofer by reducing the interior cabinet pressure.

At the same time, the orifice must be sized large enough such that air does not rapidly move through it or the orifice will squeak, like one of those rubber squeeze toys for dogs or children. A pinhole will squeak.

Dust Cap as Exchange Orifice

The dustcap is a nice way to exchange air from the interior of the cabinet to the exterior, and this also cools the voice coil preventing it from overheating and even burning out. It provides a nice surface area so the rate of air flow through any spot is small.

Cabinet Sealing

Despite the need for tiny amounts of air exchange, in both acoustic suspension and infinite baffle the cabinet best functions with a nearly perfect air seal.

This is why a gooey caulking like Mortite (tm) or other filled butylene rubber was historically used around the drivers and the back. It is why the surround must be resealed after some decades, because the butylene rubber in the surround has oxidized, hardened, flaked off, or otherwise degraded. The drivers must be perfectly sealed to the baffle, the back must be perfectly sealed to the cabinet, and the surround must be perfectly sealed to prevent air from moving through it. The only air exchange is through an opening kept small and diffuse, and that is the dust cap.

As has been demonstrated, the dust cap must be a bit porous to allow some air flow to equalize the air pressure and to cool the woofer voice coil which can otherwise become quite hot.
###​

I suggest purchasing actual Bozaks to save yourself considerable time, effort, and misery. The fiberglass-to-batting rebuilds invariable turn into a deep pit for money and time, and the results never are quite right.

Not sayin', just sayin'.
 
meh it will do.jpg thanks retrovert and I don't disagree with you but I am gonna give it a shot. Fortunately, i have a lot of nerd friends. Have soldering/schematic help lined up.
These cabinets have the same dimensions as my buddies factory urbans so they seem a decent starting place. I'll get the Mids and tweets (even though its probably not cost efficient). Look at the end of the day, its a fun exercise, I have the juice where a couple bucks isnt gonna kill me. simply stated you can't fail if you don't try.

In the meantime, i have my St 70, pas 2, old dual 1218 , teacx700r and pair of KG4's to get me through the night.
 
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D7BCA35B-6A23-4C75-B58F-11111421AF94.jpeg FF45F6C5-9D2C-4428-8C6B-8563228043E4.jpeg 55EB11EE-CE4C-4A34-8EA2-F22D34E7D311.jpeg 204C6A39-6AEB-45A1-84B6-2F7549CFC60B.jpeg FF8027F5-DF7F-4F78-B2D6-C4237C731470.jpeg 2B3CCA03-CF5E-4245-918F-349CA247D2A3.jpeg If anyones interested my progress on my build of bozak urbans is moving at what can only described as rapid. 8 days ago I picked up the home brew cabinets, I have removed all of the drivers, and in under a week found and picked up a pair of 8 ohm 209bc mid ranges that had the factory enclosures (flower pots). A pair of 200yc tweeters in 16 ohm pairs. And inside a pair of rhapsody’s I got in which I found mismatched woofers one was a 207 as it should be but the other was a 199, so I guess I now have a spare199 woofer, also got the all the Tobin crossover parts. Big shout out to gadget who really hooked me up. Amazingly everything was pretty local so I hopped in my 41 year old fiat spider and cruised new jersey and Philly to pick it all up.

sanding the old cabinets and preparing to prime and paint in a neutral gray/blue using oil paint to fit my decor. Grills will be a klipsch type gray weave.

it will be interesting to hear them soon. I have two amps. An st-70 with a pass 2 and a pristine pioneer sx 750 fully recapped and really singing for what it is. Not the fanciest amps but I like them both. Off to get some batting and figure the Curtain out.
 
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The B-207 is a B-199 woofer combined with a tweeter bracket.

Each B-200Y tweeter is 16 Ω, with the pair parallel wired to yield 8 Ω.

I suggest exercising a bit of caution when handling or attaching the midrange domes, as the plastic is brittle and may easily be cracked. I have seen a number for sale which were cracked.

Excellent work on acquiring the parts.
 
thanks retrovert, I wanted to do the boards with a little guidance so I had a buddy watch me follow the schematics and I got a 89.9 on the test. I spent an hour practicing soldering and got fairly tidy at it by the end. So.... all drivers secured, cabs have been puttied and sanded a few times, batting ordered, grill cloth from guilford of maine ordered. Need to make some bracing for the cabs. getting close. (12 days from starting from scratch) Hell, I am already thinking about what records to play on the test run.

In the running, Bill Evans Sunday at the Village Vanguard for the mids,
Marqee Moon, Television for the tweets,
and for the woofs, stella from Yello particulary the track Oh Yeah). suggestions always welcome.
 
You need a pair of 8ohm B-209B midranges and a pair of Morel CAT408 tweeters, and to build the Tobin crossover (8.2uf on tweeter, 50uf on midrange, 1.1mh inductor on midrange, 3.0mh inductor on woofer). The N-10102 has the 1.1mh and 3mh already.

They will sing like no others from that era. Paper cone drivers + old caps is a no go.

-Facebook Bozak Group Admin
 
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all of that is done not going with the modern tweets for now, I have later BC mids and later xc tweets. i did the tobin mod precisely. for these drivers.
 
yes, I own 2 amplifiers, an st70, and a pioneer sx750. will be fun to see how each perform. as you said the Urbans are not quite as efficient, but both amps currently drive my KG4 to block party levels, if one is so inclined. I'm more of bourbon, and just fill the room a bit sort of listener.
 
caferacer59 said:
yes, I own 2 amplifiers, an st70, and a pioneer sx750. will be fun to see how each perform. as you said the Urbans are not quite as efficient, but both amps currently drive my KG4 to block party levels, if one is so inclined. I'm more of bourbon, and just fill the room a bit sort of listener.
Click to expand...
I have a set of b300s. They don't have the mids but the tweeters are aluminum in mine. At any rate they sound way better than a 12" two way should and I drive them with a solid 15 watts/ch from an allied(pioneer) receiver. They don't rock the block but my living room is pretty well moved by them.
 
Hope it works out well for you. I could never fall in love with the sound of these things. I always thought the upper midrange was a little too harsh. That may have been the Rhapsody crossover though, its considerably different than the one used in older models and not compatible with the Tobin mods on it's own. Also probably partly my ears. I tend to prefer 2-way speakers that many people describe as having a "hole" in the middle.
 
@gadget73 I fell in love with my close friends Urbans, so very hopeful. YOU, were a super help to me, tell the doggies I said hi! Thanks for all the drivers and parts!!

and I have no complaints with certain 2ways, you were running KG4's when I stopped by your place, and thats what the Bozaks are replacing, 4's are no slouch and I have and do like them, did the Crites crossovers and tweets on those maybe 6-7 years ago.
 
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