Vintage Asylum

Classic gear from yesteryear; vintage audio standing the test of time.

Return to Vintage Asylum

Message Sort: Post Order or Asylum Reverse Threaded

Bozak b -400 symphony

204.133.173.131
Posted on July 16, 2015 at 12:15:25
rockanroller
Audiophile

Posts: 84
Location: ohio
Joined: March 29, 2015
 I am trying to buy a pair of Bozak B-3000 .
Should I upgrade anything?
What would be good amps to power them?
Any other insights/comments or observations would be much appreciated. Thank you.

 

Hide full thread outline!
    ...
RE: Bozak b -400 symphony, posted on July 17, 2015 at 07:29:19
bill_stevenson@bellsouth.net
Audiophile

Posts: 418
Location: West Palm Beach, FL
Joined: January 6, 2015
 The Symphony had (2) 12" woofers. Cones are made of a wool fiber blend. They cannot be refurbed using modern surrounds. Look closely at the condition of the cones. Shine a strong light on one side (have a companion help if possible) while looking at the other side for holes. If there are holes, take a pass. Both the midrange (one 6" driver in the Symphony) and tweeters (four 2.75" drivers) use aluminum cones coated with a rubber compound. Look for any signs of dents or finger pokes. Listen to the speakers carefully to hear if there is anything wrong with the voice coils. Over driven/damaged voice coils will have a rasp. I find a frequency sweep particularly helpful for doing this test. Symphonies could be biamped with a Bozak electonic crossover network. This is highly desirable. Check to make sure the speakers have crossovers as sometimes they go missing. Assuming they are intact, figure on recapping the crossovers no matter if they are active or passive. If you need to replace the crossovers, you will need first order ones (i.e. 6 db/octave) which are easy to make. Avoid the temptation to go with second order ones, Rudy Bozak knew what he was doing. In terms of amps, Bozaks always sounded best biamped with transistor amps. 50-60 wpc is more than enough.

 

Eight tweeters (grouped in two's) in a line array. -nt, posted on July 17, 2015 at 10:42:14
Jim Treanor
Audiophile

Posts: 2167
Location: Pacific Northwest
Joined: June 1, 2003
 .
Jim

 

RE: Bozak b -400 symphony, posted on July 17, 2015 at 11:09:14
briggs
Audiophile

Posts: 1674
Location: Connecticut
Joined: April 16, 2002
 If I recall correctly, the original Bozak Symphony, the B4000, had two 12 inch woofers, a vertical array of eight tweeters and an eight inch midrange. It also seems to me that the crossover points were 400 and 1500 Hz, but it has been a looooong time.

The first ones I saw and heard were in the McIntosh exhibit at --I am going to say -- the 1961 New York Audio Show. They were behind a curtain, but you could tell from the sound that they were Bozaks, and that Rudy had done something different.

I frequently listened to a pair for about a year and thought they sounded particularly good playing classical music. I still recall them fondly when I hear Mozart's overture to The Marriage of Figaro, particularly Bruno Walter's reading with the Columbia Symphony.

 

BE aware, posted on July 17, 2015 at 11:14:34
unclestu
Dealer

Posts: 5851
Joined: April 13, 2010
 that Bozak alumunum mids have a cardboard blank behind the dustcap and a piece of foam between that cardboard and the speaker polepiece. Obviously originally intended to dampen the cone, oftentimes this foam has dried up and hardened and puts a severe limitation on the mid cone travel.

That coating, incidentally, can be mimicked by latex paint.

 

RE: Eight tweeters (grouped in two's) in a line array. -nt, posted on July 17, 2015 at 12:27:59
bill_stevenson@bellsouth.net
Audiophile

Posts: 418
Location: West Palm Beach, FL
Joined: January 6, 2015
 Yea you guys are right, 8 tweeters not 4. Early examples had the tweeters arrayed on a semi-circular bracket, later ones used the line array. Crossovers were at 400 cps and 2500 cps. The original midrange driver was 8" and had a paper cone as I recall, later ones used the 6" aluminum/rubber composite. I owned a pair of Concert Grands for about 8-10 years and sold Bozak in Seattle during my college years. Those speakers were goose bump good.

 

RE: Bozak b -400 symphony, posted on July 17, 2015 at 15:27:33
Crazy Dave
Audiophile

Posts: 14371
Location: East Coast
Joined: October 4, 2001
 I am very fond of Bruno Walter's readings in general!

Dave

 

RE: Bozak b -400 symphony, posted on July 18, 2015 at 10:44:04
Bold Eagle
Audiophile

Posts: 6936
Location: America's Heartland
Joined: May 27, 2001
 Im not sure why Bozak went to the line array as it was directional in the vertical direction. I always thought the "sector-of-a-sphere" array was better. I do think the B-501 with a horizontal array of three tweeters was the best. Metal cone tweeters also have some damping behind the cone which deteriorates over time.

I've always liked the Symphony, and thought it was better sounding than the Concert Grands.

Jerry

 

RE: Bozak b -400 symphony, posted on July 18, 2015 at 10:54:09
Bold Eagle
Audiophile

Posts: 6936
Location: America's Heartland
Joined: May 27, 2001
 I have to question the use of transistor amps, unless they are McIntosh with the autoformer outputs. It seems to me that Bozaks need the higher source impedance of transformer coupled amps, whether biamped or not.

Jerry

 

Tube Amps, posted on July 18, 2015 at 12:12:59
briggs
Audiophile

Posts: 1674
Location: Connecticut
Joined: April 16, 2002
 I never heard the B4000s with anything other than McIntosh tube amps, but I am sure you are right.

 

RE: Bozak b -400 symphony, posted on July 18, 2015 at 13:16:09
BillH
Audiophile

Posts: 3913
Location: Baton Rouge
Joined: December 23, 1999
 Bozak and McIntosh were joined at the hip when I first heard the Symphony speakers. Paired with a McIntosh 2105, they were better sounding than the Concert Grands. And better looking, too, in the traditional cab with the fabric and the brass wire front.

 

RE: Bozak b -400 symphony, posted on July 18, 2015 at 13:33:23
DaveV
Audiophile

Posts: 513
Location: SC
Joined: December 26, 2009
 I worked at Bozak and spoke with Mr. Bozak often. He did indeed endorse transistor amps and Bi-amping the larger systems. There wasn't one tube amp in the factory, that I know of, by the early 1970's.
His reasoning was that the woofers needed a higher damping factor than tube amps can provide.
When I bi-amped my 4000's with a SS amp on the woofers and a tube amp on top, there was more bass tightness and slam if that's the kind of bass you like.
The input sensitivity on both amps were same so I didn't have a problem with balancing low/high.
Jerry mentioned the line array that later became known as "slot loaded" by some but it was a reviewer that coined that term. Mr Bozak thought it was amusing and just let the term stick even though the idea wasn't to "slot load."
I do think he preferred the sector of a sphere array of eight tweeters like in the 4000 lowboy but being buried like it was there must have been a lot of reflections because the end tweeters fired into the particle board tweeter compartment and then there were the Walnut arches and front trim on the cabinets. But the power handling capacity was there.

 

RE: Bozak b -400 symphony, posted on July 18, 2015 at 14:24:59
Bold Eagle
Audiophile

Posts: 6936
Location: America's Heartland
Joined: May 27, 2001
 I know his electronic crossover was transistor based.

What kind of SS amp did you use for the bass?

My earliest experience with Bozak was in a Music Appreciation 102 class in college in early 1956. The prof. whose listening room it was had a Bozak 302 kit speaker he had built, Dynaco power amp and PAS-1 preamp, Rek-O-Cut table and arm on a home made base, and a GE RPX-050 cartridge. Everything was either a kit, or DIY. The sound was excellent, including the bass which was solid. The front end of the room had a deep bay window, and there was a raised area, about a foot high in that part of the room - the speaker was on that raised area. After that I became a Bozak fan.

I don't mean to lecture; but Damping Factor is a misnomer. What actually happens is the series impedance in the amp and cable, works with the speaker impedance to form a voltage divider. Since the speaker impedance varies with frequency, there is a frequency dependent loss which is greatest at the speaker's lowest impedance. This has the effect of making the bass resonance stand higher above the midrange. This was first pointed out in a paper in 1954 by the Chief Electronics Engineer at E-V who showed the effects on frequency response by adding series resistance. He used the term "voltage divider effect". While it may sound like more damping, it is actually just a frequency response effect, and by adjusting the series impedance, you can tune the bass for a higher or lower Q.

Jerry

 

RE: Bozak b -400 symphony, posted on July 18, 2015 at 15:17:56
DaveV
Audiophile

Posts: 513
Location: SC
Joined: December 26, 2009
 I had been using a Dyna Stereo 70 on 302'a so I already had that. Then I fell for the "specs" of the Dyna Stereo 120 and bought one only to find out that the treble wasn't as nice as the Stereo 70. I called Dyna in Pa. and was told that the 120 did have "rabbit fur highs" what ever that meant but I didn't disagree.
So when I got the 4000's I used those two amps but with a Bozak bi-amp xover that was upgraded by a Bozak tech.
I know you don't like the term "damping factor" but that's the term Mr Bozak used and I'm just repeating exactly what he said.
At the time, all the Bozak SS electronics were being made down the road by CM Labs and that's what the factory used to demo the speakers.

 

RE: Bozak b -400 symphony, posted on July 18, 2015 at 19:22:09
Bold Eagle
Audiophile

Posts: 6936
Location: America's Heartland
Joined: May 27, 2001
 CM Labs had a good reputation for sound in those days.

The term Damping Factor is a "thing" of mine. Sorry to burden you with that.

Jerry

 

RE: Bozak b -400 symphony, posted on July 18, 2015 at 20:22:01
DaveV
Audiophile

Posts: 513
Location: SC
Joined: December 26, 2009
 I suppose it is a somewhat confusing issue because some mono amps had a "damping factor" control or variable pot on them so the name stuck.

In any event the issue is real because I have had several experiences with weak bass and strong bass from the same speakers but with different amps.
I can think of a 15" woofer that had a resistor hidden and glued behind a frame member and a complete very expensive speaker system that had a resistor in series with the woofers to change the Q.

I just thought it would be interesting/informative to note that Mr Bozak said his woofers worked better with SS amps and for the reason he gave me but I do wonder how big a difference it would make on a single woofer system that wasn't driven as hard as the larger ones could be.

He didn't mention his older woofers so I'd also have to wonder if that applied to earlier woofers or the latest ones because there were changes.

What a nice man he was. I'll never forget him or the guided tour of the "chamber" or big walk-in dead room and the huge electromagnetic speakers he made for the 1939 worlds fair.

 

RE: Bozak b -400 symphony, posted on July 18, 2015 at 21:49:14
E-Stat
Audiophile

Posts: 37672
Joined: May 12, 2000
Contributor
  Since: April 5, 2002
 Using four tweeters may technically constitue a line array, but a poor one at that IMHO. As you observe, such are directional in the vertical plane.

My electrostatic line arrays eliminate from that being problematic since they are at least seven feet tall. There is no difference in vertical dispersion regardless of your listening position. Just as I perceive live music. :)

 

RE: Bozak b -400 symphony, posted on July 21, 2015 at 11:28:43
bill_stevenson@bellsouth.net
Audiophile

Posts: 418
Location: West Palm Beach, FL
Joined: January 6, 2015
 Jerry,

When I biamped my Concert Grands, McIntosh MC2505 amps were chosen for the reason you suggest. But later Rudy Bozak recommended direct coupled amps and in fact even developed his own amps which followed his ideas. The ones I finally settled on were ARC D100As. I still regret selling my Bozaks.

 

Page processed in 0.029 seconds.

[ Top Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]