Dave Moulton wrote:

I've never auditioned the BL11, and have no opinion of it.  However, it will not solve the problem I discussed.  2 drivers (as a general rule) do not have enough bandwidth to cover the 10 octaves of the audio spectrum (say, 20 Hz. to 20,000 Hz.).  A good, well-implemented driver might cover 2.5 octaves in a reasonable way.  So, 2-way speakers (including the BL3, which actually is a bit more than a 2-way) have serious limitations.  

The brilliance of the BeoLab 3 lies in exending the low frequency response of the woofer through using passive side radiators with a different resonance than the driven front-firing woofer, thereby teasing almost an extra octave out of a tiny design.  I wish I'd thought of that!  

This brings up two related questions:

- It seems like the shape of the Beolab 11 make it almost like a vertical acoustic lens- does it not such a dispersment issue as an ALT since the frequencies are so low?

- There are remarks made about the Beolab 2 being "slow" for bass because of the passive side radiators- if this really an issue, wouldn't it also be a problem with the BL3's? Here is a very positive comment about passive side radiators, but most comments related to the BL2 seem negative.

Guh, how irritating, I just posted a great big long response then accidentally closed the tab!

I know I can respond to the first question with some degree of knowledge if I may?

The lower the frequencies you're expecting your speaker to handle, the larger your horn or 'directivity device' needs to be. In the case of a subwoofer, this would have to be massive. An 'Acoustic Lens loaded' subwoofer would have to be wider than your average estate car is long. A horn-loaded BeoLab 5 subwoofer would have to be at least 8.5 metres across in order to make the deepest notes directional. This is because longer wavelengths wrap around smaller objects more easily. With an Acoustic Lens, you're trying to STOP the sound from wrapping around the horn, you want it to get directed in the 180ºx30º arc heard in the BeoLab 5, 9 and 3.

A BeoLab 11 is producing notes which have wavelengths as long as 6 metres, even longer in some cases. Even the highest notes it reproduces will have a wavelength of 1.5 - 2.0 metres. All of these are sufficiently long that they can wrap around the tulip design of the BeoLab 11 without being affected by it's shape at all. As the drivers are so close together, their sounds add together almost perfectly and more-or-less double the volume output. The BeoLab 11 is IMO a fantastic design!

As far as the BeoLab 3/2 thing goes, I have some theories in my head, but Dave will have much more knowledge about these two designs than anybody else on the forum! IMO, the tuning of the BeoLab 2 passive radiators is too low. A subwoofer of that size really shouldn't be able to reproduce such low frequencies at the sort of volumes the BeoLab 2 does. The result of this is higher levels of distortion. That's all in my opinion though!

Good questions:

The shape of the BL11 has little effect on its dispersion, because all of the wavelengths it produces are "large" relative to the device (ca. 3 - 18 meters).  It is definitely NOT an acoustic lens!  

Regarding the BL2, I've never believed it was "slow" in an auditory sense, as described by many.  I've found it to be really nice with BeoLab 3s for both video/film and music.  I don't use it in the studio bcause (a) for my production work BL3s alone are better and (b) with 5 BL5s on hand, I can "check the bass" extraordinarily easily!  The physics of passive side radiators are well known, and particularly with the mass added on the BL2 there must be some lag, manifested as phase shift,  relative to the driven woofer.  The difference between that and what I suspect happens with a BeoLab 3 has to do with the difference in size.  The BeoLab 3 will have negligible lag (relative to the BL2) because the size of the drivers is so much smaller.  

So I'm one of the ones that doesn't have a problem with this, especially on the BL3s.  I think they are both great examples of audio engineering!  

Thanks for listening!  

Dave Moulton wrote:

The brilliance of the BeoLab 3 lies in exending the low frequency response of the woofer through using passive side radiators with a different resonance than the driven front-firing woofer, thereby teasing almost an extra octave out of a tiny design.  I wish I'd thought of that!  

Dave, thanks for you comment to my earlier question. One more thought though about your BL3 comment and BL2s and the extra octave, just an observation- do the BL2's get further down in the frequency range for the same reasons? I heard a BL2 in a store years ago that were with BL1s, and as a test track I had an organ piece which featured a soft 64' stop, which is around 8Hz. So this is well below the "spec" but it made a rumble! Later I tried the same track on BL5 and frankly didn't hear so much. Of course the 64' stop was a "resultant" stop, meaning it is really two pipes, neither 64' long for practical reasons, a 32' stop (16Hz low C) and a 2nd rank tuned a fifth above (24) so the beat frequency is 8, this is sometimes done for very low notes on organs. Of course any two tones close in frequency has a beat (major 3rd in equal temperament at some ranges).

The crossover characteristics of the Beolab 3's as discussed above did remind me of a earlier thread about the presumed lack of midrange of the Beolab 9's. Does anyone know if the 9's are designed with comparable crossover frequencies? 

jc wrote:

The crossover characteristics of the Beolab 3's as discussed above did remind me of a earlier thread about the presumed lack of midrange of the Beolab 9's. Does anyone know if the 9's are designed with comparable crossover frequencies? 

Being a three driver speaker the crossover freq's in the 9's are as follows:

The frequency range of the 10 inch woofer is 30 to 180 Hz,  being exactly 2,5 octaves. The 5 inch midrange operates from  180 Hz to 2 kHz, which is approx. 3,5 octaves and finally 3/4 inch tweeter takes over from 2kHz all the way up to 20kHz, which is if I' am all calculating correctly 3,3 octaves. 

Thinking of the presumed lack of midrange (I have experienced more or less the same) it just reminds me of the following paragraph in Beocentral's productdescription of the BL9's:

Quote  "The BeoLab 9 used 3 drive units, described as a 10” woofer, a 5” midrange and a 0.75” dome tweeter. This made for a nominally 3-way loudspeaker, though given the sizes of the drive units and their crossover points the effect was more akin to a small 2-way loudspeaker working in conjunction with a well-matched subwoofer." Unquote

So if we want to haven a "complete" speaker, we will have to save for the Beolab 5...

jc wrote:

So if we want to haven a "complete" speaker, we will have to save for the Beolab 5...

No, I most certainly would not say the 9's are "incomplete" speakers soundwise.

The frequency response remains generally flat with a few db's frequency rise above 10 kHz. After experimenting for a while (based on several valuable advices of fellow Beowolders) to find the correct placement, I highly admire and appreciate the overall performance of these stunning speakers. I certainly would not part with them.

I can't say I am enjoying the read, but it is an intriguing one.  That said, if I am going to part with 11 large for a pair of speakers, I will appreciate and thoughtfully listen to what people say and base my decision on what I, not they, think are my reasons for buying.  Actually, I think most people do something similar.

Edit: PS, If that didn't translate as appreciative and friendly, I apologize.  I meant it in a positive, taking responsibility, kind of way.