Beolab 5 - Four Questionable Technologies

From this plot it sure looks as if the direct sound from the driver and the reflected sound from the frizbee above it are mixing. I was expecting or looking for this but it took me a while to find a plot so let me explain...

This is an effect called flanging and it can be quite pleasant as it creates an extremely spacious sound effect such that you cannot locate the source. This trick is well known and can be used to create the impression of stereo from a mono track. One signal is delayed by a fixed amount relative to the other and when summed you get the characteristic "comb filter". In this case the flanger is a fixed delay rather than a swept delay (like you get from pumping a guitar pedal).

You can tell this is likely going on from the characteristic sharp notches on the frequency response of the horizontally mounted drivers with frisbees: the dome midrange and dome tweeter)

I am surprised Tom Nousaine did not remark on this possible issue. He is an engineer and should have at least explained why it might not be a problem of this design.

Clearly the dome drivers are visible from the side and therefore the listener must be hearing two tweeters and two midranges: one directly and one delayed by the distance between driver and the frizbee that it reflects from. The fact that some reviewers have reported being baffled that even a lone BeoLab 5 speaker makes it hard to detect the source of the sound is a dead give away that this might be happening: the spacey rock guitar sound. Since the tweeter is aimed upwards at the frizbee then this signal will be much stronger than the one radiated sideways directly from the driver to the listener, which means the notches will not be that deep (as seen on the plot).

I am sorry to say but this design fails the basic acoustic physics back of the envelope test. I remain flabbergasted by the outstanding reviews - perhaps I am completely missing something? Ironic that a spacey looking speaker might also make a "spacey sound".

YMMV, this is conjecture as I don't have these speakers available to me in a lab to test out what appears to be happening. Perhaps B&O have a perfectly reasonable explanation of how they deal with this design issue, in which case I would apologize for my erroneous ramblings/conjecture.

Shadorne - Scores of people who HAVE HEARD this speaker think it sounds great, yet, you who do not say that you have heard it, theorize that it cannot work.
Aren't you one of the people who cautions everyone never to buy a speaker without hearing it in their own system? Why in god's name would you suppose to know of a deficiency that you have not heard? What motivates you to caution against something you are guessing about?

Why in god's name would you suppose to know of a deficiency that you have not heard? What motivates you to caution against something you are guessing about?

Macrojack - I am curious and cautious because

1) this is a novel design
2) rave reviews
3) barely any audiophiles seem to own this design (yet it has been around for 4 years)

There are tens of thousands of ordinary box speakers with forward facing drivers that have been built over the years, with good reason => this type design works well. A novel design that looks like a Dalek has my "hype alert" sensors showing yellow warnings!

I agree that an audition is the best way forward but perhaps it helps to be aware that pleasant sound effects may not necessarily be accuracy and that there is very little of a track record behind this novel & very expensive design.

Shardone,
If you would be willing to audition these speakers I would be grateful. Then you can tell me if in the "real world" you can hear the design flaw you have detected.

B&O can only be auditioned at B&O stores. Their website lists them. Here is a link: http://www.bang-olufsen.com
On the left hand side of the home page is a a link called "Store Locator"

Shadorne,

Regarding your 1st and 3rd points,

-The Beolab 5 may be a novel design in terms of its unique implementation, but the one technological feature that you seem to be focusing on, specifically the use of acoustic lenses to achieve omni-directional dispersion, has actually been around for a while and is a proven concept (see Hegeman / Morrison, Walcott, Duevel).

-The point that "barely any audiophiles seem to own this design" is your weakest argument as it is an appeal to authority, which is a logical fallacy. The fact that you may know of few audiophiles that own a Beolab 5 speaks more of audiophile-accepted trends, attitudes and prejudices rather than the inherent qualities of the Beolab 5 (or any other non-audiophile accepted product, for that matter).

As Microjack rightly pointed out, you ought to listen first and then let your ears decide.