diagonal vs in line speaker placement

I had heard diagonal is better since there is less phasing/cancellation - but that seems weird to me since speakers are round and radiate outward anyway.

I'd figure distance between the two speakers is more important than where they are, horizontal or diagonal.

IDK, maybe it doesn't matter

 

I would guess that phase cancellation still occurs, just in an angled plane containing the central axis of both speakers. Unless you're going to be putting your head really close to the amp (don't), I doubt the cancellation will really be an issue as long as you wire them up in phase.

 

Lift one end (left or right) to tilt your amp 45 degrees. Does it sound different?
What MIGHT make a difference is how much wood is between the speakers. If they are too close together I could see the the baffle flexing much more because it is weaker.
I could see a less-ridgid baffle sounding different.. but personally I doubt I could tell the difference.

 

Tweed twins were diagonal. Nuff said.

 

I don't know if the shape of the speaker cabinet has much to do with any of it. Check out this setup by ARK amps.

http://www.arkamps.com/Model C.html

 

I doubt it makes any difference at all, as long as there's room for everything and nothing touches the tubes or transformers. Just depends on the proportions of the cabinet. A horizontal 2x10 cabinet can look kind of "low and wide", an extreme example would be the 2x10 Music Man amps, which are not pleasing to look at in my opinion. If the diagonal placement will allow for a cabinet with more of a "golden ratio" proportion, then go for it.