What would be a reason for putting a tweeter on top of the loudspeaker?

[Koeitje]

Some loudspeaker designs put the tweeter on top of the enclosure. The most notable example of this is B&W. What is the reason for doing this? I guess it helps with diffraction, but without a waveguide there wont you run into a directivity issues?

 

[freemansteve]

Guessing that if the tweeter was too close to floor or ceiling you'd get too much reflection, or if you had thick carpets, too much absorption...

 

[kthulhutu]

So many speakers have a tweeter directivity dip that it's become a de-facto standard at this point. Perfect directivity speakers are the outlier in this regard and while technically better, may not sound as right for many recordings without EQ in this region.

 

[antcollinet]

I'm going to go out on a limb and say:

"Marketing"

 

[AudiOhm]

Removes the baffle from affecting the tweeter response.

A good video on a speaker baffle...

Ohms

 

[ROOSKIE]

Good primer.
Great place to start what will be a long journey to fully understand the pluses and minuses of a variety of design choices.
Most everything is a double edged sword.

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[NTK]

Quoting Dr Toole:

...
A feature of the 800 series not commonly appreciated is that its behavior is predictable from visual inspection. The midrange speaker is quite large, meaning that it is becoming significantly directional before it crosses over to the tweeter. When the tweeter comes on, it has wide dispersion which is enhanced by its unbaffled mounting, which aggravates the problem. Today, it is becoming common to see tweeters on baffles with waveguides to improve the directivity match with the midrange speaker at the crossover frequency - thereby achieving what is widely regarded as a desirably smooth directivity index as a function of frequency.

I am confident that the B&W engineers know all of this, but by now the 800 has achieved a certain status among consumers and professionals and the attractive physical form and appearance are iconic symbols. Sadly they make good acoustical design very challenging. Wise studios would have an alternative, neutral loudspeaker, to audition as well, and many do.
...

 

[dualazmak]

Interesting thread...

I have intensively investigated the positioning of super-tweeter Fostex metal horn T925A with the 3-way Yamaha NS-1000, and found really unique best position which is under the woofer+midrange squawker, with the Beryllium dome tweeter on the top position. Consequently, woofer+midrange squawker is sandwiched with upper Be tweeter and lower metal horn super tweeter. Of course, this SP driver physical alignment is just unique for my specific multichannel multi-driver multi-way multi-amplifier stereo audio system in my room acoustic environment.

Here, let me show you the positioning investigation photo which I shared and discussed in my post #27 on the above project thread;

Just for your additional reference, I recently established 0.1 msec precision time alignments between all of the five SP drivers, i.e. subwoofer, woofer, Be-squawker, Be-tweeter and the metal horn super-tweeter (my post #520 entitled "Perfect (0.1 msec precision) time alignment of all the SP drivers greatly contributes to amazing disappearance of SPs, tightness and cleanliness of the sound, and superior 3D sound stage" on that project thread and the related posts mentioned there).