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Multi-Way Conventional loudspeakers with crossovers

B&O Beolab 90 - adjustable directivity by DSP
B&O Beolab 90 - adjustable directivity by DSP
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Old 8th October 2015, 01:07 PM   #11
Quip is offline Quip
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Originally Posted by Omholt View Post
Can you explain further how this is accomplished?

I assume the crossover between the tweeters and mids is fairly high. Meaning the spacing between them in this freq. area will cause lobing. Unless you use a very large amounts of drivers (like in a line-array) you will have lobing and comb filtering.

Omni is my opinion a waste to use indoor in a living room. It's more than sufficient to have a wide dispersion which covers all the listeners no matter where they sit. Making it omni only causes unwanted frontwall reflections.
I meant to say that smooth horizontal directivity is IMO fairly achievable with such a design, but I doubt the vertical performance. To put it another way, vertical lobing is a bigger problem with this design in my opinion.
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Old 8th October 2015, 01:36 PM   #12
Omholt is offline Omholt  Norway
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B&O Beolab 90 - adjustable directivity by DSP
I know you referred to the horizontal, but I don't see how it's much different than the vertical. As you can see from the picture below, the drivers are also placed next to each other. They are placed in a triangular fashion that minimizes the spacing a little but it doesn't solve the problem.
B&O Beolab 90 - adjustable directivity by DSP-bl90_reflection_01-jpg


So normally, even with the narrow setting, there would clearly be horizontal lobing and combing. This will increase when choosing "wide" and using the drivers on the side. But both the polars look great. Either they have solved this somehow or smoothing is covering it.
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Old 8th October 2015, 01:37 PM   #13
Snickers-is is offline Snickers-is  Norway
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Bjørn:
First off all, I think you are right about the vertical response. It has to be somehow affected by the number of drivers. However, the energy response in such a setup will benefit from the kind of dispersion control you have in the horizontal plane.

So if we look at the horizontal dispersion control to begin with, you can say that lobing will occur if drivers are spaced far apart, but then again, you only need 3 drivers to get perfect dispersion control at one frequency. So what BO is doing here is that they have two narrow band dispersion control speakers facing forward, one with midranges and one with tweeters. The three forward facing tweeters will work together to control the dispersion in a relatively narrow band, much like the first 3 rings of the ESL63. The band that is not covered by this is at a significantly lower frequency band. This means you can successfully extend the dispersion control with the additional tweeters on the side without running into serious horizontal loobing problems. The midrange array is slightly larger and can therefore perform the same task at lower frequencies.

Then if you imagine a mic in front of the speaker, and you lift it upwards you will off course get lobing. If you place the same mic behind the speaker, you will get almost nothing at all. If you start lifting it, you will need to lift it pretty high up before it starts picking up a significant amount of energy from the front. This is a good indicator that the energy response is pretty nice too. However, how nice it actually is will be up to the interaction between the vertically spaced tweeters and midranges.
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Old 9th October 2015, 12:01 PM   #14
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I really like what B&O are doing. These guys know their psychoacoustics and they are using modern technology. Too bad it's so insanely expensive. Earl, you really should check out what they're doing. Try to be open-minded and I'm sure you'll like it.

BeoLab 90: Measurements earfluff and eyecandy
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Old 9th October 2015, 01:05 PM   #15
Tenson is offline Tenson  United Kingdom
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Amazing design. I've had the same idea and even got many of the drivers here waiting for time to do it. I feel sore I didn't do it first now!
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Old 9th October 2015, 01:22 PM   #16
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Amazing design. I've had the same idea and even got many of the drivers here waiting for time to do it. I feel sore I didn't do it first now!
The concept is very much in line with Ken Kantor's Magic Speaker: http://www.kenkantor.com/publication...ic_speaker.pdf
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Old 9th October 2015, 01:41 PM   #17
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Legacy do a bit of directivity control too. I think the B&O is the first to use separate amping of every driver and advanced DSP to get it all integrated right.

One thing though - they say each speaker has 8KW of amps. But you can only draw a max of 3KW from a mains socket
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Old 9th October 2015, 02:16 PM   #18
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Originally Posted by Tenson View Post
Legacy do a bit of directivity control too. I think the B&O is the first to use separate amping of every driver and advanced DSP to get it all integrated right.

One thing though - they say each speaker has 8KW of amps. But you can only draw a max of 3KW from a mains socket
The Kii Three does it too: Kii Audio GmbH - High End Active Speakers for HiFi and Professional use.

All that power is there only for headroom. 8 kW amps doesn't mean it will draw that much power from the mains socket. Only if all amps were to deliver maximum output over a sustained period of time are you likely to run into trouble. You'll probably fry one or more of the drivers before exceeding the maximum power that can be supplied to the amps.
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Old 9th October 2015, 02:18 PM   #19
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The Kii looks like a really nice design, but some way off the attention to detail in the B&O.
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Old 9th October 2015, 02:42 PM   #20
Boden is offline Boden  Netherlands
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Does anyone here know what exactly the differences are between the B&O concept and the Ken Kantor AR Magic Loudspeaker (yes, 1985!).

BTW: what I found rather ironic is that the starting point of the current design, is a most conventional WWMTWW speaker, a design violating all controlled directivity principles..

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Eelco
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