Midrange/Tweeter Axis question

[Tyson]

If mids tend to be more directional than tweeters (assuming a 5 to 7 inch mid driver and a one inch tweeter), why are speakers generally designed to put the tweeter on-axis with your ear? It seems like it would make more sense to have the midrange on axis with your ear, and the tweeter slightly above (or below) this, especially considering the fact that midrange drivers tend to beam at the crossover frequency (assuming 1.5 to 3khz) and tweeters have very wide dispersion at these frequencies.

[numberoneoppa]

Tweeters are more directional than mids. It's the frequency that matters. Where did you hear otherwise? This is why tweeters are on-axis with the ear.

:3

[Tyson]

I'm referring to beaming at the crossover frequency, in the midrange. A 6.5 inch driver is beaming quite a bit over 2khz, and a 1 inch tweeter will have massive off-axis response at the same frequency. This discrepancy is why it's difficult to integrate drivers. At least, that is my understanding. So, if you have one driver that has great off-axis response at the most critical range (the upper mids), and another driver that beams significantly at the same range, why in the world would you listen on-axis with the great off-axis driver, and off-axis of the beaming driver?

[1Michael]

Tweeters can be designed to either shoot sound like a laser beam where you will only hear sound by standing directly in front of it, or spread out like a Japanese hand fan. As you go down in the frequency band, the sound begins to radiate outward in all directions. FWIW the frequencies between 80-100 and below are recorded in mono so there is no such thing as stereo subwoofers, they are dual mono...

If I understand it correctly it's not the horizontal dispersion that the tweeter has a problem with it is the vertical dispersion that is the issue, so placing it on axis with our ears is the most desirable.

[gainphile]

A generic 1" tweeter will beam less than a 5" cone midbass at 1khz, let alone 2khz. So yes, my speakers are designed and measured at the midrange axis.

Additionally, when listened at tweeter axis generally the soundstage height is not natural. Almost like listening towards a horizon. When the tweeter axis is 2-5cm above ear level, the soundstage is tall and realistic.

At least these are my observations with dipoles.

[Tyson]

gainphile, you get what I'm talking about! It just seems odd to listen on axis to the driver that has the widest dispersion at 2khz (the tweeter), and off-axis to the driver that has the least dispersion at 2khz (the midrange). Seems more logical to listen on-axis to the mid driver. Maybe I'm on crack here, but these thoughts tend to occur to me when I'm 10 hours into insomnia while listening to Beethoven's "Kreutzer" violin sonata (with Perlman and Argerich performing, no less!).

[gainphile]

The issue I think is the resurgence of popular new tweeters with larger domes and/or large surround - the 27s, 29s, as well as ring radiators. These tweeters may sound dull-er when listened off-axis.

But they do give lower fs so that's the engineering compromise. Now, that reminds me why Seas Millenium is great. It's 25mm and has low Fs. Along with 0.5mm xmax. Not easy to achieve.