Yes indeed,there is some info on this,have look in the archives on this site for the particular speakers you have.

It's also worth pointing out that if you have disconnected drive units to refoam them,you should ensure that they are reconnected in the correct phase,ie,the same polarity that they were connected originally.You can check the polarity of each drive unit by applying a small battery across the terminals,and watching the direction of the cone movement.

Nick

Little bit off Beo maybe, but wander how much B&O and Jamo had common? They both had uniphase type speakers at that era. I dont remember that anyone else had.

I quote Jon:

As far as I understand it to be, Bang and Olufsen decided on using the filler-driver concept as a way to compensate for the phase shift introduced by a crossover.

Because of the resultant phase shift with a crossover, the driver's polarities usually are reversed so that their acoustic output sums flat at the crossover point. This, however, obviously means the speaker system can never achieve a minimum phase response (zero phase shift being the goal).

What B&O did with the 3-way Uniphase speakers is to design a crossover with symmetrical 2nd order low-pass and high-pass acoustic slopes, but with the drivers connected in phase. Then, in order to counteract the resulting cancellation in response, they used a midrange driver to "fill in" the response - that midrange driver's passband being centered in the middle of the high and low frequency driver's crossover point. Above and below it's passband, the midrange driver's acoustic response rolled off at a shallower rate. This meant that the overall frequency response of the speaker summed flat, yet the drivers were all in phase with each other.

As well, B&O "time-aligned" (physically lined up) the acoustic centers of each respective driver. This is why you see some of the drivers a bit more recessed on the baffle than others. So, the Uniphase designs are "transient-perfect" as well, in that they can (mostly) accurately reproduce a square wave. Notice that "time-aligned" designs which are not also either minimum phase (zero phase shift), or linear phase (the entire passband of the speaker phase-shifted by an equal amount), are not transient perfect.

I believe the 2-way Uniphase speakers have the response of the high-pass and low-pass sections overlapped, and then the hump in response is tuned out.

There are WAY more knowledgeable people than I who discuss this at length. You can probably Google things like "transient perfect" and "filler driver" and find alot of useful, in-depth information. Search for a man named "John Kreskovsky" - he's written a few papers about this subject.

The merits of this design are highly debated, with many people saying you'll never hear the difference. I'm the kind of person that doesn't always trust my ear, but I do believe what I can measure to be true. Within certain limitations, I believe in the merits of these designs.

Many people claim that due to the reflections and phase anomolies introduced just by your listening room, a transient perfect design is a moot point, and I can see where they're coming from.

Also, by nature, these designs have poor vertical polar response, illustrated perfectly by the big difference in sound quality you get when you listen standing up versus sitting down. Even if you could somehow get around the room influences, the Uniphase speakers' transient perfect quality (and really, it would be the same with ANY similar design, not just B&O's) would be evident only through a very narrow listening window. Move up or down off axis out of that listening window, and that phase coherency is lost.

These speakers were made back when B&O was more concerned with technical perfection, IMO. It's not an easy thing to do; what they did, that is. It resulted in a more complex and expensive design, but one they considered worth it. Again, many doubt the validity of these designs in the first place, and don't even bother to acheive these design goals. And I've heard many fine speakers that are nowhere near transient perfect in nature. But there are a number of manufacturers that do strive for this, so I guess it just depends on what you choose to believe.

Orava wrote:

Little bit off Beo maybe, but wander how much B&O and Jamo had common? They both had uniphase type speakers at that era. I dont remember that anyone else had.

DMacri wrote:

Orava wrote:

 

Little bit off Beo maybe, but wander how much B&O and Jamo had common? They both had uniphase type speakers at that era. I dont remember that anyone else had.

 

 

 

I think Thiel, Vandersteen, and DALI and a few others had similar design goals/attempts.

Not to mention the original Dahlquist DQ-10, phase and time alignment was a forte of this 5 way design. And it did have a fairly small sweet spot, but man, the sound in that sweet spot was amazing. Sounded best if you did the mirror image and cap mods. I used to sell these back in college. 

Recently I ran across the crossover schematic for the DQ-10. Very odd, a combination of both parallel and series crossovers. I've never seen the like. If anyone is interested I'll try and find the schematic and post it. 

Oddly enough, the crossovers on the CX series of B&O speakers are series xovers as well, not something you see too often. 

Thanks for allt he information!

I have very little time to try out things at home in these days, but I'm happy that you confirm that this design requires finding a precise "sweet spot" (also on the vertical axis) for the best listening condition. This was exactly my feeling while experimentig a bit with the MS 150. The crossover still has the original caps for the moment (so it may not be working exactly as it should), but the general feeling while listening was something like: "Uhm... Let's try to sit higher... No, lower... No, closer... No, I'm too close... No, let's move the speakers a bit... Not yet...". Calssical piano music (very coloursful, with big extension and dynamics, things like Messiaen...) is expecially problematic at the moment.

Do you have any personal experience about an expecially well-working listening set-up in a room with such speakers?

Thanks!

DMacri wrote:

Orava wrote:

I think Thiel, Vandersteen, and DALI and a few others had similar design goals/attempts.

Not to mention the original Dahlquist DQ-10, phase and time alignment was a forte of this 5 way design. And it did have a fairly small sweet spot, but man, the sound in that sweet spot was amazing. Sounded best if you did the mirror image and cap mods. I used to sell these back in college. 

R

 

Ah, maybe they didn´t have distributor here at that time... or they were in price category I didn´t dare to look.

Orava wrote:

 

DMacri wrote:

Orava wrote:

I think Thiel, Vandersteen, and DALI and a few others had similar design goals/attempts.

Not to mention the original Dahlquist DQ-10, phase and time alignment was a forte of this 5 way design. And it did have a fairly small sweet spot, but man, the sound in that sweet spot was amazing. Sounded best if you did the mirror image and cap mods. I used to sell these back in college. 

R

 

Ah, maybe they didn´t have distributor here at that time... or they were in price category I didn´t dare to look.

They were mainly a product of the mid to late 70's. They looked like Quad electrostats but with cloth grills rather than metal, mainly since John Dahlquist loved Quads. A partner in the company was THE Saul Marantz. They were not efficient, really needed a good high current amp, and we're bass shy, which is why they developed a good subwoofer for them, but the imaging and smoothness were addictive. The midrange driver was a dipole, a conventional cone driver free air mounted with a felt pad over the back. Very placement critical, more so than the MS150, as you had the rear back wave to contend with, like all dipoles. 

Back then, there were two stereo stores on the same college town street, we sold Dahlquist, ADS, Polk, Harman Kardon, and a bunch of other high end stuff, and the other dealer sold Klipsch and, ta da, B&O!  They went out of business ao we moved into their storefront, then we went under, mainly due to mismanagement. The owner would trade equipment out the back door for coke, which doesn't pay the bills. 

When I had my MS150s restored, the restorer, Richard Allen loudspeakers commented that they were exceptionally fine units. He at his own expense had tested them and they produced a practically ruler flat frequency response.

I found that they produced a sound when used with the Beomaster 8000 not dissimilar to the Beolab 5 in that the bass was very detailed but one could play the system at very high levels and not notice until someone else came into the room. The treble was the weak area in my view as in common with the rest of the late range Uniphase speakers, they tended to shriek, probably as the Beomaster started to distort. The earlier M100 was smoother in this regard.  They were never my favourite speakers mainly because I found the construction poor in comparison to the earlier models. The grilles were a particularly cheap plastic and the stud for holding them on the speakers are prone to breaking. The wood veneer is nothing like the quality of the M100 though the cabinet construction is novel with the carcass having a bitumen filling. The internal finish is however poor compared to the earlier models, a sign of the decline of the cabinet skills.

These days, watch for the disintegrating foam surrounds and the sticking protection circuit which makes the bass speakers sound as if they have blown! Annoyances include the din plug feeding in directly behind the stand - a pain when these speakers weigh 30kg each!!