Bozak B-305 Urban Restore

[mccuskerkt]

Picked these up from another AKer, Cabs need some work, but they sound good. May do the tobin mods, not really sure yet. Main thing for now is getting the cabs looking shiny and new. Fair warning, there's a chance I may paint these instead of refinishing. If you have something against painted wood, maybe don't read on :-D

The back panels were nailed and glued--no other way in. In related news, I got a new reciprocating saw today.

Got the panel off, cleaned up the glued wood bits.

Don't know much about the insulation, other than there is a lot of it.

 

[drbiggles]

Hey man,

That's a really large, most excellent project. I'm jealous and congratulations!

Put the insulation in a large trash bag and set it aside. When you're done, put it all back in. That's what you do with that!

Pah, you're going to get into the crossovers to make them fresh. You might as well put Pat Tobin's changes into effect and put the crossover points back to where Rudy Bozak had originally intended.

Time to get to work! What does the exterior wood look like now?

Biggles

 

[PastTechFan]

Don't know much about the insulation, other than there is a lot of it.

That there is "Kimsulate", a paper insulation by Kimberly-Clark ( think Kleenex) from 40's-50's. Same stuff forms the back blanket behind the Tannoy in my EV Aristocrat cab. Apparently used a lot for trailers and quonset huts back in the day. Fairly dense stuff. As biggles said, I think it should go back in.

I do love the look of a Bozak crossover. Very "business" like. Should almost have safety wire on the fasteners. I'd be tempted to mount on top of the cab, but my wife wouldn't see the beauty.

 

[drbiggles]

I do love the look of a Bozak crossover. Very "business" like. Should almost have safety wire on the fasteners. I'd be tempted to mount on top of the cab, but my wife wouldn't see the beauty.

Use 3M spray adhesive and cover it in Hello Kitty pink heart confetti, that might work.

Biggles

 

[mccuskerkt]

Thanks for the tip and support!, I will bag it and put it back in when it's time. One less pile of stuff in the landfill. And I'm keeping my eyes peeled for a bunch of the aluminum tweeters and midranges. Those might need to come later, though. The new back panel will be screwed in, not glued, so access for future tobin mods won't be an issue. I am looking for a badge and legs, if anybody happens to know of some. Might just find some generic tapered mid-century style legs if I cant find the originals.

 

[drbiggles]

Thanks for the tip and support!, I will bag it and put it back in when it's time. One less pile of stuff in the landfill. And I'm keeping my eyes peeled for a bunch of the aluminum tweeters and midranges. Those might need to come later, though. The new back panel will be screwed in, not glued, so access for future tobin mods won't be an issue. I am looking for a badge and legs, if anybody happens to know of some. Might just find some generic tapered mid-century style legs if I cant find the originals.

Hop into Barter Town and put up a Wanted To Buy ad in Parts, you may be able to find the badges and tweeters. The B209's may take a little more time and effort to find. As far as legs go, you could spend the next 48 hours on the net and not find all the selections that are available to you. I love vintage legs! The tough part in finding those nice teak, mid-century tapered legs is that you need 8. Finding 4 is easy, but 8 is exceptionally tough. Oh, and they're expensive. I would suggest just going down to your local hardware store or mega home improvement store and see what kind of new legs they have. That's how I found mine for my Stephens Trusonic project. I included a picture so you can nearly see how good they look. The best part though? The new mounting plates are the same as the vintage mounting plates. In that they both use a 1/4" 20 bolt to attach the legs into. So, if and when you find the vintage ones, you can just unscrew the new ones and put the old ones into place. Or you can look into the steel hair-pin style legs. I love the look of those too. Here's the ones I got from the hardware store:

Biggles

 

[mccuskerkt]

That's how I found mine for my Stephens Trusonic project

those trusonics look incredible. The white grill cloth is a nice touch. Great tip on the legs. Hadn't thought about how difficult finding 8 matching legs might be. I had an ad up in the Bartetown section, no bites, should probably resurrect it.

 

[mccuskerkt]

Found some time to do a bit more dis-assembly. Ordered the grill cloth and xover caps from parts express. I found a source for some (pricey) legs here that may work, I do have a huge favor to ask anyone with a set of 305 urbans: can you tell me the leg dimensions? Before I disassemble the other speaker, I am gonna do some pre-recap measurements with my UMIK-1 calibrated mic.

NUDES!!! speakers look great. Gonna keep the paper mids and tweets for the time being. Maybe some aluminum drivers will fall into my lap someday, but if these were good enough for Rudy Bozak in 1958, they're good enough for me

Grill cloths. You can still see the driver silhouettes. Not bad for nearly 60 year old cloth though.

 

[drbiggles]

Hey man,

They're looking great! No help on the legs, but I would guess between 6 and 8 inches will do just fine.

Go do the measurements, I want to see the results!

Biggles

 

[mccuskerkt]

It was nice out today, so I spent some time under a tree and stripped the old finish. Here's what the cab top looked like before I got to work.

Not a whole lot of finish to remove, but what's there definitely has to go.

 

[drbiggles]

Keeripes man! With a little sanding and a lot of finish work, they will look tons better than they did from the factory. Wow!

Congratulations man!

Biggles

 

[Hawkeye83]

Following with great interest! Proud to say I owned these for a little over a year. Sorry I didn't get to the restoration, mccuskerkt! These are going to look (and sound) like a million bucks when you're done with them, I'm sure!

Would have loved to tackle this project myself...would have been my first restoration...but as mccusker can attest to, they were way too big for my 10' x 13' office!

Good work so far, man!

 

[mccuskerkt]

Made some time to work on the speakers today, and even took some rudimentary measurements--I'm still learning the Room EQ Wizard software, so take them with a grain of salt. Here's what I learned today

A) The second speaker wasn't glued completely together, and the bottom panel came off as it was supposed to. Huge relief.
B) The second speaker has a different crossover (N-102 vs N-10102) I need to do a little research to find out the differences between the two and then plan out how I will make them the same.
C) Both speakers have some nasty distortion in the mid-range and upper range. The distortion becomes worse as the volume goes up. I am using a weak Sony receiver that is probably having difficulty with the 16ohm load, so that may be the issue, maybe it's the 50+ year old caps, maybe it's a combination of both, or maybe it's something different altogether.
D) The second speaker uses drivers built in 57, while the first speaker uses drivers from 58. Same drivers, but interesting nonetheless.
E) The second cab is in worse shape than the first. I'm leaning towards repairing the damage with putty and painting them white. I'll know more after I strip the second cab.
F) I love restoring these speakers. There are all sorts of little problems to solve and issues to consider and things to learn. Its awesome.

N-102 Crossover. Those caps tho.

57 B-199a driver

58 B-199a driver

 

[mccuskerkt]

Click on the graphs, and then again to see a larger version

20 to 20,000 hz sweep, 1/6th smoothing. Mic centered on speaker placed 1m away

Distortion. To this seems to confirm what I am hearing--the gnarly distortion at the upper ranges. Hopefully new crossover caps and better amplification (Citation II connected at the 16 ohm taps) will resolve the issue.

 

[mccuskerkt]

Did some sanding work over the weekend, there are some pretty good gouges in the wood. A little work with the 80 and 150 grit makes them less noticeable.

Top cab of 1st speaker. Seriously not bad for 60 year old speakers. I have 5 year old furniture that hasn't held up as well.



One more light hand-sanding and these will be ready to go. There are one or two deep scratches that I will not sand out (Doing so will either sand through the veneer or leave low spots).If the other cab looks this good I will definitely not paint them



More to come.

 

[drbiggles]

Scratches and gouges are OKAY. Embrace the imperfections, embrace the character. Man, they look absolutely stunning. Wow.

Biggles

 

[Hawkeye83]

Wow is right! Holy cap they don't look like the same speakers already! I agree...a few flaws adds character. Those are going to be gorgeous.

 

[mccuskerkt]

Worked on the 2nd cab today. It's rougher than the 1st--plenty of character, and I'm good with that.

Here's the worst of it.



and this bottom corner: I'm thinking I'll fill in the area with putty or bondo or the like, and then patch it with a bit of veneer.



Stripper time. Nasty stuff, snot consistency.



Wait for it to bubble. The fumes pair great with a Ballast Point Sculpin



wildly satisfying.



Gotta wait 24 hours to sand.

 

[mccuskerkt]

Early Sunday morning crossover work. When I am trying to understand a circuit I often separate each part. Helps me make sense of the whole thing. I also have to do the same thing when dealing with almost any type of math. Anyway, this is base off the original 1959 N-102 schematic posted over at the Bozak yahoo group. I believe this will set the Xover points at 800Hz and 2500Hz with 6db falloff. Tobin mods bring the high pass down to 400, but I'll start with the original specification.

Break it down Barney style.




Cap from the N-102 crossover. I'm gonna go ahead and say this isn't original. Capacitance is spot on, but it's not staying.




Meanwhile on the N-10102 crossover, the 50uf Chicago caps are all over the place. This one is reading 33 nf




Time to order parts.

 

[Drugolf]

Why not keep that spot on PIO cap? (looks like a pio)