Acoustic lenses

31 replies

Listened to a beolab 3 for some time now, and compared to classic speakerdesign I think I miss some "midrange". I don't know but perhaps I like the more straightforward sound of a non-acoustic lens speaker. Has anyone here had the same thoughts? I ask this because the acoustic lens design seems to get little or no critisism, reviews are without exeption very positive. Listening to the 3's I think the sound is perhaps too much dispersed, it's hard to hear a "focus" of the sound, also the sound is very light-weight (although the bass is good), perhaps some will call that "transparant", but I think I miss a bit of directness (if that's  proper English), and body. 

Would like to hear some opinions about these issues.

Are you using them right?

B&O consistently fails to mention that acoustic lenses are supposed to have their sound reflected from side walls, relative to the listener. You are supposed to get a direct wave of sound from the speakers, combined with the reflection of the sound from the side walls. The slight delay as well as reduction in SPL of the sidewall reflections will augment the tone that reaches your ears.

Even without such sidewall reflections (symmetrical placement of speakers relative to walls and listening position is ideal), the acoustic lens will reduce the amount of floor/ceiling reflections, which is good as our hearing is designed to work along a horisontal band "through our heads." Dave Moulton has written much about the philosphy behind the lenses over at his website, as has his co-inventor, Manny LaCarrubba.

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B&O marketing speak reduced the invention to "place them wherever you want" which is not very wise, unfortunately.

Even without sidewall reflections, the speakers measure flat as a dead calm in the region you are considering.

I have had a pair of Beolab 3's for a few years now, and I love them. Soundproof is absolutely right about the placement of speakers with acoustic lenses. Sometimes there's a lack of bass. but I can't complain about the midrange, however both improve when you add a Beolab 11.

Agreed.

B&O has long had a reputation for all show and no go when it came to speakers. The ALT technology was to put a big dent, but it seems that either B&O themselves didn't quite understand what they had, or didn't trust the clients to and so put the technology out there as a convenience feature.

I'll also mention that they should be listened to sitting down. It's a shortcoming of the B&O showroom design that you're often listening to loudspeakers standing up when the speakers are at ear level. It's not so much an issue of comfort (though you should be comfortable when auditioning speakers), but that the tight vertical dispersion of the ALT gives the music a hollow character if you're standing up too close to the speakers. It's like some of the sound is missing you.

Based on the way my house is set up, I'm listening to 3s and 9s the most and have to say that, to the extent that I still register an awareness of the technology, the 3s are often the standouts to me as they seem to outperform their size to a greater extent than do the 9s and 5s. 

To each their own, however. I still have older clients whose ears were nursed on speakers and amplifiers of a different age who still prefer the BeoLab 6000s as the best speaker. 

Can we expect a new alt loudspeaker this year Trip?

Trip: B&O has long had a reputation for all show and no go when it came to speakers

What about the seventies speakers? They gained a very good reputation, something I can understand as I own also a pair of Beovox S45-2, connected to a Beomaster 7000. 

Regarding the placement of my 3's; they are standing on top of their stands in a large (90m2) room without sidewalls very near to them. (switch set to "free").  

About the Beolab 6000 (which gets a lot o critisism here), I listened to those recently in the house of a friend, Chopin pianoconcerto was being played, and I was surprised how good they sounded, very clear and easy to listen to. 

Happy New Year, everyone!  May you prosper mightily this year!!!

jc makes an interesting point, and he's not wrong.  The BeoLab 3 is a 2-way speaker, and there is NO way that a 2-way speaker can cover the entire audio spectrum.  

Keep in mind that I use BL3s for professional production work, find them viable and like them a lot.  Nonetheless, there is less midrange energy (ca. 1.25-2.5 kHz.) than I'd like, simply due to the way the woofer is crossed over to the lens tweeter.  Lots of engineering thought (i.e. trade-offs) goes into a critical decision like that, and I for one don't want to second-guess the B&O acoustic designers that did that work, even though it might not have been my choice.  

I can live with it however, and enjoy the speakers a lot.  That characteristic has nothing to do with the lens function – it is simply a crossover decision.  But jc is physically correct, and his description is also, to my ears, accurate.    

Best regards,

JC, I'm referring to our reputation in the audiophile press and among audiophiles themselves. While I believe our speakers always sounded terrific, we were not taken seriously at our price-points. This may have been a different story in the 70s, but when I picked up the thread in the 90s, this was certainly the case. The BeoLab 5s seemed to be a turning point. 

@Mr Moulton: Thank you for your reaction, as it's very interesting to hear these technical background details from the person who knows the engeneering proces that produced the ALT speakers inside-out.

Can I therefore conclude that the crossover issue will be solved with the addision of a Beolab 11?

@ Trip: With the Beolab 5, perhaps the "audiophile" press in the end accepted that B&o in fact puts a lot of effort in R&D, a practice that up to then wasn't (and by some still isn't) recognised. But that's off topic.

jc wrote:

Can I therefore conclude that the crossover issue will be solved with the addision of a Beolab 11?

The BeoLab 11 crosses over at much lower frequencies (80 Hz I believe, I could be wrong) which won't affect the midbands to that extent.

There is a good argument as to why using a subwoofer would help clean up the midband (reduction in harmonic distortion from the BeoLabs and less upward masking etc...) but it won't change the tonality of the midband...

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