audio-talk

Does anybody know why the usual layout for a 2 way speaker is tweeter on top?

The setup with my monitors on their stands puts the driver at ear level(or thereabouts) with the tweeter about 2 or 3 inches above. I've just turned the speakers upside down, basically because every time I stand up I get a completely different sound scape. I quite like the tweeter at ear level at the moment, it's certainly a bit brighter, but also the focus is a tad sharper. There's every chance I'll get tired of the sound, but it's interesting to investigate.

I'm suspecting it's got something to do with the fact that the ribbon tweeters have no vertical off-axis projection and at ear level they are more present.

I remember when I first put them together I was having problems balancing them and I brought them to Owston with the tweeters disconnected...

anyway, I digress, anybody got a view on why the tweeter is usually on top?

Because the centre of gravity for the speaker cabinet is lowered.

Usually for convenience. As you know, the majority of multiway speakers are designed assuming the listening axis is on the tweeter. So in most cases, it tends to be more convenient to have the HF driver at the top purely to keep the overall height (either enclosure height for floorstanders, or height to which a standmount is elevated) as small as possible. Where you can start getting exceptions is with low order crossovers. Most tweeters are physically quite shallow compared to a typical midbass or midrange driver, so their voice coil and the acoustic centre is therefore also physically further forward than the acoustic centre of the midbass / midrange when they're both mounted on the same flat baffle. As a result, the tweeter's output will arrive at the listening position slightly ahead of that of the midbass / midrange, and especially with something like a 1st order or LR2 design, that's a problem because they won't sum properly at the crossover frequency. So assuming passive speakers, you've got four options to prevent that (assuming you don't want to move to a higher order filter or use asymmetric filters to compensate).

1/ You can use a stepped baffle (mount the woofer on a sub-baffle slightly ahead of the tweeter)
2/ You can use a sloping baffle (or tilt the speaker back)
3/ You can use an all-pass delay network (ladder / trellis delay), or
4/ Put the listening axis on the midbass / midrange, which usually means the tweeter is below it. Same sort of approach as the tilted baffle, it moves the tweeter physically further away from the listening position, delaying the arrival of its output to match that of the midbass / midrange unit[s].

This may be less of an issue at low frequencies where wavelengths are long, but it can be a major consideration at the XO frequency of a typical 2-way. Anyway, that's basically 'it' in a nutshell, in most cases anyway.

The tweeter is at ear level because that makes us believe that the image is at that level. Most people do not like to look up or down to live sonic events (we even have descriptions like "eye to eye"), and that preference carries over to hifi.Only teachers learn to look down at seated students...