Bozak B-4000 Symphony speakers

[lindsayt]

I've just bought a pair of Bozak B-4000 Symphony speakers from an eBay seller in London.

Collecting them will be fun. They weigh 70kgs each and are 115cm x 70 cm x 40cm. I'll need to collect them from a third floor flat and drag them up to my 1st floor listening room when I get home.

Here's a picture from the eBay listing.

More photos to follow after I get them home...

They have 2 x 12" woofers, 1 x midrange and 8 x tweeters in each cabinet.

I've already joined the Bozak Yahoo group for more information and help on these.

Bozak speakers seem to be rather rare in the UK.

The price I paid for these is about the same as the value of my DMS passive only Briks. I'll be keeping whichever speakers sound better.

The advice I've read so far on these Bozaks suggest the following upgrades:
1 new crossovers as per a Mr Tobin's design.
2 adding a super-tweeter to augment the rather rolled-off response above 12khz.
3 Bi-amping - 1 amp for the woofers and 1 amp for the midrange and tweeters. This is intriguing. I'd be very interested to hear how they'd sound with my ss amp for the bass and my valve amp for the midrange and treble. Could be a great combination.


I'll post the results of my £0.5k heavyweight speaker bake-off in due course...

 

[lindsayt]

I prefer the bass of the Bozaks and the midrange and treble of the Briks.

The Bozaks have a wonderful, deep, growly, punchy bass. You can feel the Bozak drums and bass guitar hitting you in the chest, bouncing the floor and kicking the air inside the sofa.

However, the midrange and treble sound muffled and shut-in compared to the Briks.

Put the Briks on and you think "Hey, where'd the bass go?". But guitars cymbals and vocals sound much sharper on the Briks. Acoustic guitars have a lovely sparkly sound to them after the Bozaks.

At the moment I prefer the Briks overall.

There are certain tracks where the Bozaks hint at greatness. "Believe it or not" by Alien Sex Fiend being one of them.

In their current form, the Bozaks would be most suited to someone with a decent sized room and a very bright front end / amplifier.

I can see why a fellow Bozak Yahoo group member recommended getting a pair of supertweeters for the Bozak.

I also quite quickly found that the Bozaks are much more directional than the Briks. It's important to get those tweeters firing straight at you with the Bozaks.

I've got some more experimentation to do with positioning to see if I can get a location where the bass dominates the overall sound less.

And a crossover make-over or redesign could bring some more life to the midrange and treble.

More tweaking and listening to follow...

 

[lindsayt]

I took the back off to get some info on what I've been listening to.

One of the 12" bass cones.

Part of the column of 8 tweeters.

Crossover.

Left hand speaker. I think they look nicer in real life than they do in photos, but that's not saying an awful lot.

Right hand speaker.

 

[Tony L]

Hooked my valve amp up to the Bozaks. Used the 8 ohm tap.

Surprise. The midrange and treble opened up with the valves. I didn't expect that. Thought I'd get a bit more detail and sweeter softer treble. Instead I got a bit more detail, plus more air plus more cutting edge to the midrange and treble. Maybe some of the effect is my ears getting atuned to the tonal balance of the Bozaks?

If they are anything like my Klipsch Heresy they just sit and sulk with solid state, they really are a different speaker when they like the amp upstream. Synergy is everything with old speakers IMO, especially efficient ones (which I bet the Bozaks are). I've never heard a pair but they look very interesting indeed.

Tony.

 

[lindsayt]

Bozak B4000's are supposed to be paired with amps ranging from 20 to 100 watts. So not quite SET friendly, but push pull friendly - which is what I've got.

A certain amount of care went into making them an 8 ohm load. Such as four pairs of 8 ohm tweeters wired in parallel and series. The woofers are supposed to be 2 x 16 ohms wired in parallel for an 8 ohm load. I need to check that this is, in fact, the case with mine.


One thing with the Bozaks and a push pull valve amp and a record like Aerosmith is that they produce a room filling sound.

 

[Markus S]

I can imagine!

 

[ter]

I once had Bozak Speakers. They were meant to be a 'add on' Unit, so they could be made more powerful. I found them a 'pig' of a speaker. If I am correct some of them used Audax tweeters. Mine were supposedy rated to 200 watts. After throwing climactic peaks of 130 watts RMS at them once, ( tested with full oscilloscope) they blew the tweeters. Also found a 'white fur like mold' growing on both channels - bass cone speaker material..............this... in a very dry climate! Never before had I had such a situation. (Nor one since, some 25 years later) I junked them at the time, without regret.
Bozaks went out of business long ago...'nothing to be sad about'.

 

[lindsayt]

A more thorough investigation of my Bozaks has shown that:

My bass units are 8 ohms each - wired in parallel. They should be 16 ohms each. The 16 ohm bass units are rarer and more valuable becuase they were only used on this model. All other Bozaks used 8 ohm bass units because they had either 1 or 4 of them in each cabinet. This explains the dominant bass I've been getting from them. It's an impedance mismatch between the bass units and the midrange and treble.

Ideally I should buy four 16 ohm bass units. Easier said than done. The pragmatic solution might be to go down the bi-amping route...

According to the stamps on them, I have 4 B200X tweeters from 1957 and 4 B 200Y tweeters from 1966 in each cabinet. The B200X's should have metalic dustcaps - but I can't see this through the dense grill material.

My midrange units are stamped as B209's from 1957 but have stickers on saying they're B209B's - which were made later.

I've also got an N104A crossover in the left speaker and an N104 in the right one.


More unsolved mysteries than an Agatha Christie novel...


At least there's no sign of mould on my speakers. The bass units were dipped in a Bozak special recipe that included organic compounds. This resulted in the cones being denser towards the middle than the outside.

The midrange and treble units, apparently have a latex coating.


As far as I know, all units used on 1950's to mid 1970's vintage Bozaks were Bozak units. "Rudy Bozak was a purist".


Someone voiced the opinion on Interwebland that Bozaks have a better bass and midrange than Klipschorns, whilst the Klipschorns have a better treble.

I don't think that my Bozaks are the best speakers ever made, but I can see the potential for them to be very good value for money speakers.

 

[lindsayt]

I've bought a used Ashly XR1001 active crossover, 6 RCA leads plus 60m of Cat 5E networking cable (cheapo speaker cable).

My plan is to open the lid of the Ashly and cut one end off the RCA leads and solder them into the Ashly. I'll need to do this because the Ashly has XLR and TRS sockets, whilst my phono stage and amps have RCA connectors only.

The RCA leads only cost me £5 - which was cheaper than getting RCA to XLR leads. And soldering them will be cheaper than buying adaptors.

So the Ashly will sit between my phono stage and my ss amp for the woofers and my valve amp for the midrange and tweeters.

I'll solder the cat 5e wire directly onto the woofers, bypassing the crossover in the speaker cabinet and going direct to my ss amp.

I'll still need to use the in-speaker crossover for separating the midrange and tweeter signal from my valve amp. A future possibility might be to tri-amp - ie go fully active.

Then I'll have some fun twiddling with the controls on the Ashly to get the best sound. I'll start with a crossover frequency of 400hz...

 

[smithy]

Just get some XLR plugs from Maplin and knock your own leads up,good to see another Ashly user I use a XR 2001 the 3way version.The boys on the Lansing Heritage site seem keen on using the Ashlys with beefy SS amps on their Altecs.

 

[lindsayt]

My Ashly XR1001 arrived from the States.

I've now got my phono stage with volume knob feeding the Ashly which splits both channels into a low and high signal. The low signal below 200hz at the moment goes to my ss power amp which goes to my home-made speaker lead that's soldered to my Bozak bass units. The high signal goes to my push-pull valve integrated and then to the terminals at the back of the speaker, that feed the crossovers inside the cabinets that are connected to the midrange unit and the 8 tweeters inside each cabinet.

I've got the volume settings equal for low and high on the Ashly. The volume on the integrated valve is at about 7/8ths. This is my brightness control.

If I touch the Ashly case when it's powered up I can feel transformer vibration. With the volume at max the Ashly adds some hiss and a faint 50hz hum. A possible future upgrade might be to get the transformer offboard or maybe even to try a different transformer.

I've still got a few tests and adjustments to do such as: testing that bass units and midrange are in phase, trying a range of crossover frequencies, fine tuning the bass v midrange volume levels (at the moment my prefered setting depends on the record being played).

How does it sound?

Well, I won't be going back to single-amped Bozaks. I've got better tonal balance now. No more totally dominant bass due to the impedance missmatch. The midrange muffling effect has gone as far as I can tell (I'll have to swap back to my Briks to check this). They also sound more dynamic. Or is it just that they sound more effortless at louder listening levels?


Anyway, I don't really know how good the Bozaks are on a global scale.

Anyone fancy a sub-£500 speaker bake-off? Or a sub £2000 amp and speaker combination bake-off? Or a sub £4500 total system bake-off?

 

[smithy]

There was a Stereophile article on the Bozak Concert Grand if I remember right about 18 months ago I will try and find it in my magazine pile.l

 

[lindsayt]

The sterophile article makes interesting reading.
http://stereophile.com/historical/1005bozak/index.html

After further listening I feel that the Ashly has slightly reduced the amount of detail in the midrange and treble. The treble also sounds less sweet than when I was using the valve amp in passive mode. Hey, but then I wasn't expecting miracles from a device that only cost me £120.

I wonder if there's a valve equivalent to the Ashly? Or a passive device that would do the same job in my system?

Some records such as Human League and Bachmann Turner Overdrive sound spectacularly good with a lot of bounce to them. Other records like Eagles sound a bit uninvolving (when I listened to it 15 minutes after switching my amps on).

 

[RustyB]

Could you try connecting the woofers in series, given that you have a bass-heavy balance?

 

[lindsayt]

If I went passive single amped and wired the bass drivers in series I'd get a bass light balance. Mids and tweeters at 8ohms, bass drivers at 16ohms.

I could disconnect one bass driver in each speaker to restore the balance, but that would probably decrease the bass impact.

With the Ashly I get a completely adjustable tonal balance.

 

[lindsayt]

Here’s an edited version of a post by Thomas W on the Bozak Yahoo group.

There’s an interesting explanation on why Bozak Symphonys and Concert Grands use 8 tweeters in a line array (and I used to think it was just because 8 tweeters made power handling easier!).

I fully agree with his comments about listening to Bozaks all day without fatigue. Or in my case all evening and well into the night without fatigue.

The purpose of the Bozak tweeter line array is to concentrate the range from 2,000 hz to 13,000 hz to the seated listening position. By doing so it keeps the sound off the floor and ceiling, where destructive reflections can muddy the sound, cause bad reflections destroying the stereo image. They line array increases the size of the free field being produced by the speaker which gives you optimum articulation of the voice and musical instruments. Speakers that spread the sound everywhere depend on you spending large amounts of money to control your room acoustics, or as an alternative being seated at very close distances to the speaker. This reduces room reflections from the room that smears the sound being reproduced by the speaker...

…Speakers made by Snell, B&W, KEF , Wilson all depend on you treating your room acoustically and using the latest electronics with frequency control to get optimum results. Bozak was from a different period of time where speakers were placed against walls and seeing positions were in the created sweet spot. AR started the other way of listing with the AR-3. They changed all the rules. They won the war. But A Bozak Symphony set up properly can be listened to all day with no fatigue of the ear a full listening levels with moderate power. None of todays speakers can say that. TWI

 

[stackowax]

If I went passive single amped and wired the bass drivers in series I'd get a bass light balance. Mids and tweeters at 8ohms, bass drivers at 16ohms.

I could disconnect one bass driver in each speaker to restore the balance, but that would probably decrease the bass impact.

With the Ashly I get a completely adjustable tonal balance.

Don't know whether something like this would be worth exploring? They could be used to manipulate the impedance the amplifier sees. I gather that, in some cases, there are benefits to doing this.

 

[lindsayt]

I suppose I could cobble something together so that my amps saw the bass cones as an 8ohm load.

But even Symphony's with the correct dual 16ohm bass drivers sound best when bi-amped.

I'm on the look-out for a Bozak N-106 active crossover. These have sold on eBay in the past for less than $300. Although I guess I'll be bidding against a lot of other Bozak owners for the next one that comes up.


I've also found an odd effect from connecting my ss power amp directly (bypassing the in-speaker crossover inductor that would usually filter out frequencies above 400hz) to the bass cones of my Symphonys. The case feels warmer than when the amp's powering my Briks. And if I leave the amp on overnight with everything else in my system turned off, the amp will be quite hot in the morning. I'm sure with my Briks that it was cool in the morning after being left on?

No big deal I've just got in the habit of switching everything off when the system's not in use.

 

[lindsayt]

Just came across this info posted by Ken Seger on the Yahoo Bozak group showing the US retail price of Bozak speakers as well as a few other interesting speakers in 1976 / 1977:

April 1977
B201A Sonora vinyl $209/pr.
B301 Tempo Vinyl with fabric grill cloth $339/pr.

March 1976 CPI = 56.0 so multiply by 3.5678
B201 Sonora vinyl $199/pr $12 extra for foam grill
B301B Tempo vinyl with fabric grill $319/pr.
B301FD Tempo Walnut floor standing $379/pr.
B401 Rhapsody $549/pr.
B407A Monitor C $995/pr.
B4000-4005 Symphony $1,265 - 1,516/pr
Concert Grand $2,222 - 2,387/pr

For comparison from the same sheet:
Magnepan MGII $625/pr
Tympani TIC $1,325/pr
Tympani IIIA $1,895/pr
Quad ESL $930/pr.
Klipsch Heresy $496-594/pr.
Cornwall $788-1,050/pr.
LaScala $1,050/pr.
Belle Klispch $1,680/pr.
Klipschorn $1,350 (K-D-BR) - $2,080(K-B-WO)/pr.