Misure : larghezza 61 cm
profonditą 51 cm altezza 70 cm
I haven't seen too many comments on these
forums about Bozak speakers. I recently acquired a pair of Bozak 302A
Urban speakers from circa 1960. These are big, infinite baffle cabinet
design speakers, 2 ft x 2 ft x 2 ft cubes, beautifully simple, "early
60s modernistic" styling, and the single prior owner kept them as new.
Here's an image from the web of the 1960 ad brochure for Bozak's line,
the 302As (with matching cabinet that I also have) are at top:
I wanted to sing the praises of these speakers a bit here and talk about
some very simple mods that can be made to the older version of this
speaker - which I acquired - to bring them into the big leagues. I'm so
happy with these speakers after mods that I have stopped worrying about
spending big dough to buy Tannoy Concentric Golds off eBay that I
wouldn't even be able to listen to first. I still hope to pick up
Tannoys someday, but now there's no hurry, and I can wait until I can
find a pair at a garage or estate sale for $100 like Steve did! :) (I
can dream, can't I?)
I WILL POST PHOTOS LATER TODAY of the speakers and the mods when I'm
home. I'm NOT generally a guy who goes into making major mods to vintage
gear - my MC30s and Marantz 7 are stock, stock, stock and will stay that
way - but the Bozaks are a bit different. First off they are less
expensive to begin with, even if stock, so resale value isn't a big
deal. Second, the original Urbans I bought have some known major
limitations that need to be addressed, but once they are, you get a
world class speaker. So I took the plunge. Here's what I changed,
working with my dad over the weekend:
1) First off, the older/original version of this speaker had all paper
cones - each speaker had one 12" woofer (B199A), one 5" mid (B209), and
two small (2 1/4" I believe) tweeters mounted side by side (B200X). The
12" paper woofer is one of the things Bozak was famous for. It is superb
- more on that later. The paper mids weren't bad but not stellar either.
The paper tweeters are frankly terrible.
Enter Pat Tobin, probably the greatest expert on Bozak speakers. His
e-mail, in case anyone is interested, is firstname.lastname@example.org
VERY approachable, nice person who is very willing to help anyone get
their Bozaks singing. He was for example cited as "the" Bozak speaker
expert in a recent Stereophile article about the Bozak flagship model,
the Concert Grand B410 speakers (massive suckers, take most of a wall
up!): Concert Grand article (
Tobin has posted widely on many audiophile forums about the superiority
of the slightly later aluminum tweets (B200Y) and mids (B209A) that
Bozak developed, which are interchangeable in size with the older paper
versions. I saw these posts in doing Web searches on Bozak speakers and
then contacted him and after speaking was convinced this would be worth
pursuing. So first thing I did was pick up a pair of Bozak 1970s 313s
with whipped external cabinets - but which had pristine aluminum mids
and tweets - and this weekend dad and I pirated those and installed them
in the Urbans and took out the paper mids and tweets.
2) Second, a couple of crossover mods are optimal in improving the sound
of the Urbans. First, the old Bozak N10102 crossover in the original
Urbans has a huge cap box with 6 big paper caps. These are all out of
spec and really unnecessary nowadays - there for a couple reasons
originally that are no longer salient. 4 of the caps were for the
midrange network, 2 for the tweets. Working in the cap box would have
been a nightmare and I doubt worth the effort. Tobin agrees, and
recommends eliminating this cap box and replacing the 4 mid paper caps
with a single 25 uF Dayton Audio grade caps and the 2 paper tweeter caps
with a single 8.2 uF cap. We did that. Much cleaner.
3) Finally, the biggest issue with going to the aluminum tweets is that
they are much "hotter" than the original paper tweets, about 9dB louder.
So to balance them with the rest of the cones a tweeter network mod is
required, basically installing a 2.0 uF cap and some resistors (attenuation
circuit). This mod also allows the tweets to extend above 10 kHz - in
the original crossover, the highs roll off rapidly at 10kHz, a
purposeful limitation within the crossover and not an inherent
limitation of the aluminum tweeters. We used Tobin's instructions to
make this modification as well.
4) So in summary, the circuit diagram below shows the entire modified
speaker circuit, including Tobin's tweeter network mod WITH TWO SMALL
ERRORS - first, the 8.2 uF cap in the tweeter network should obviously
come BEFORE the attenuation mod. We wired things correctly, just didn't
have a chance to redraw the incorrect diagram. Second, the numbers of
the cones my dad put next to the speaker symbols are the older paper
ones rather than the updated aluminum ones.
5) BEWARE! We also found some wiring mistakes FROM THE BOZAK FACTORY!
Polarity was reversed on one of the speakers in the wires going from the
back of speaker hookup terminals to the crossover network input! We
fixed that. I'd suggest always checking Bozaks for stuff like this,
apparently there were some issues.
6) Finally we also replaced the fiberglass baffling inside the cabinets
with new fiberglass insulation material. The old stuff was crumbling to
even gentle touch, a mess. Nice and clean now.
SO HOW DO THEY SOUND? In a word, unbelievable! The 12" paper bass cones
Bozak made were amazing. I'm still learning and have a lot of speakers
to hear, but the transient response on these woofers is amazing. Plus I'm
coming from much smaller speakers with 8" woofers, so to me the visceral
impact is simply amazing with the Bozaks, drums sound like drums and
bass like bass, and it's not bloated or rounded off bass - you hear the
growl and twang of string bass on jazz recordings, and it sounds
different than the round fatness of the electric bass on a disc like
Steve's BOB JAMES IN HI-FI - just as it should be! The aluminum mids are
to die for - you listen to ELLA AND LOUIS and they are standing there in
your listening room (particularly when these are paired with MC30s!). I
am hearing vocal nuances I have never heard. And the aluminum tweets are
a HUGE improvement over the paper versions, which hissed and spat in
response to anything in the 5-10 kHz range. With the aluminums, it's
smooth as silk and Tobin's crossover mod allows you to get extension
above 10 kHz. I haven't done any test tone testing yet but I'm guessing
they go all the way up to 20 kHz as modern speakers do.
The only remaining weakness I can see with these speakers is the tweeter
placement. Tweets are placed in front of the bass cone as you can see
from this brochure (it's the 207A woofer/tweet combo:
...and the bass cone is mounted down low in the cabinet. This places the
tweets only about a foot off the floor, below the midrange cone. No good.
Next project which will be easy will be to dismount the tweets from the
woofer bracket and build a very small enclosure for them to sit on top
of the Urbans. We'll run the tweeter wires through the back of the
cabinet and up on top. This will get all the cones properly oriented and
at that point we'll be done. Make no mistake even with this flaw the
highs are gorgeous, but clearly this needs to be addressed based on my
listening tests (sitting on floor versus in usual chair - highs better
when I'm on the floor).
So anyway, wanted to share this for a few reasons:
1) Bozaks are fantastic speakers, don't let anyone tell you otherwise.
Maybe one of the best bargains in vintage speakers. Altogether I paid
about $500-700 for these speakers, including buying the upgraded
aluminum cones and all the crossover mod parts - PLUS I also got the
matching audio component cabinet Bozak made to go with them. I can't be
exact about price because I bought these as part of a larger sale where
I acquired an entire single prior owner vintage system for a lump sum.
Bozak was notorious for not publishing speaker sensitivities but I'm
guessing based on where I have to put my volume knob on the preamp, as
well as the era of manufacture and use of paper and very thin aluminum
cones that they are in the 94-96 dB/watt range. Great for vintage tubes.
2) Bozak Urbans will likely require some work to get them up to snuff.
If you plug them in as is, stock, you'll be disappointed, especially
with the older all-paper cone versions. Very boxy, dull sound with
terrible highs. The contrast after the modifications is amazing, they
become world class speakers. I don't think you need to worry much about
resale if you do these mods - in fact, I'm guessing the value of mine
has not been hurt and may actually have gone up with the "Tobin mods."
But I could care less because I'm not selling! :D The combo of the paper
12" woofer and the aluminum mids and tweets is to die for.
3) Even with the mods, these speakers still have a wonderful, "vintage"
sound - and it's primarily the amazing midrange cones that provide this.
So don't worry about making them into something they shouldn't be, I
view this as bringing out their best. They sing with all kinds of music
but I have to say, they sound most magical with well-recorded material
from the 1950s-60s.
4) Anyone who can read a circuit diagram and solder can make these
modifications! Totally simple with Tobin's help/guidance. I'm the poster
child for "if I can do this, anyone can do it!" And if you're still gun
shy about doing the mods, Tobin will make the crossover mods for you for
$60 if you send them to him. A really, really great guy who in my book
has great ears - what he said the mods would do to the sound is exactly
what I'm hearing.
5) Finally: if you buy the slightly later Urbans that already have the
aluminum mids and tweets, beware: you will STILL need to make the
crossover mods Tobin recommends because Bozak did something weird to the
tweeter network on that later model - generating a really off-putting "hump"
at 5-10 kHz which sounds harsh and fake, plus the highs still roll off
sharply at 10 kHz. Good news is that the later N10102A crossover in
these later Urbans can be modified just exactly as the older N10102s can
- they end up looking and sounding just the same as you will rip out the
crappy sounding stock tweeter network.
Happy to field questions/comments - and I'm hoping there are at least
some other Bozak fans out there.
Il foofer da 12 pollici
Davvero ottimi diffusori di un tempo
andato , ma sempre attuale se ricerchiamo qualitą riproduttiva.
La storia della azienda:
Un altro modello Bozak
La storia del progettista:
Big Bertha con
punto vendita di :
E tanto Altro