SpeakerTalk

[David]

Does anyone know what he is talking about. I found this from the Interview section of the archives on the Stereophile site. Paul Barton is the founder of PSB speakers in Canada. At one time I owned one of his earllier designs. The KEF crossover for the T27 is specified at 3500 hz..

[quote]
Atkinson: The speaker that has been my favorite for a while, the B&W Silver Signature, is a two-way with an 8" woofer. So what you have is a little bit of off-axis flare at the bottom of the tweeter passband. But the woofer appears to be rolled off a little early to give a shallow depression in the on-axis response in exactly the same region where the power response has a little too much energy. So when you read about loudspeaker designers "voicing" their speakers, I think that what they're doing is playing around with the on-axis response to compensate for discontinuities in the dispersion.

Barton: Yes. I would definitely agree with that. Can I talk about other speakers? It's one that no longer exists, but the original KEF R104aB was very flat on-axis. But they crossed the tweeter over way too high. If you put a pair in a room that had reflections, it was a very laid-back speaker. Very distant-sounding. Very pleasant.

Atkinson: Because of the lack of presence-region energy in the room?

Barton: Because the total energy wasn't there. The 104 was a very well-respected loudspeaker, and quite frankly worked well in a dead-end/live-end situation, which was at that time the way KEF designed loudspeakers. But it was very room- and placement-sensitive.

Take a speaker that has smooth sound, power, good off-axis response, good on-axis response. When you think about it, it's probably the most forgiving speaker in any kind of environment. Because when the room is dead, all you hear is the on-axis sound, and it's okay! And when it's in a live room, you hear the sound power, or the reverberant energy, and that's okay! [quote]


David

[terry]

David
Interestingly you will find some more information about the KEF 104ab crossover design on the main allansonline site. Dave Dlugos provided the document through a post elsewhere on this Forum and I have published it for others to view. The link is at the bottom of that web page.
Terry

[David]

Thank you Terry. I have printed the article you referred to. it is most hellpful.

David

[boyzo]

[quote="David"]Does anyone know what he is talking about. I found this from the Interview section of the archives on the Stereophile site. Paul Barton is the founder of PSB speakers in Canada. At one time I owned one of his earllier designs. The KEF crossover for the T27 is specified at 3500 hz..

At 3500Hz c/o the 2 drive units are NOT acoustically close, the center to center spacing is large relative to the (in wavelength terms) crossover frequency.
So the off axis response will have a c/o dip, the reverberant field in the room will add to the on axis response and colour it at the listeners seated position.

The ideal Mid / Tweeter combination is for example a B110 and a 25mm dome @1500 hz c/o there almost NO dip of axis at crossover.
Today lower mid tweeter c/o frequencies are used which minimizes the off axis dip this is because of new thinking AND very robust low Fo tweeters with a 600 hz dome resonance.

With the KEF104AB its the directivity of the B200 thats the problem halve the c/o freq. and // or use a 150mm driver and considerable improvement occurs in driver integration.
The radiating area of the B200 does shrink at 3500Hz to the central area but the drivers spacing // c/o frequency is the major weakness

The new KEF UNIQ drivers are a step in the right direction 150MM mid and concentric tweeter.