Meyer is highly respected in the world of live sound, as you say. On the monitoring side they make the traditional HD-1 monitor and the unusual and very high-tech X10 (which uses a compression driver/horn and weighs a modest 95kg).

I can't think of any studio, especially not any mastering studio (which is probably the closest experience to domestic hi-fi listening in terms of being interested in absolute fidelity), which uses horn tweeters for monitoring. There must be some since Meyer has presumably sold some X-10s - but I think it would be true to say that this is unusual and the world's best known studios don't use horns for monitoring. Horns ARE useful in live sound because they make it relatively easy to control the directivity of the sound, which is important both on stage - where you are fighting a battle between monitor/foldback volume and feedback from the mics - and in the FOH PA system where it is good to be able to be accurate about sending sound into precise areas of the venue, filling in dead spots etc. Horns have a tendency to "beam" the sound, which is a virtue if you are only trying to create a narrow beam to fill in an area but a vice if you are wanting to avoid the tonal balance changing catastrophically when you move your head 2 feet to the right while sitting in the near/mid field! Of course you can change the directivity by changing the shape of the horn but still it is very unusual to have monitoring speakers that use compression drivers/horns.

Someone mentioned Eggleston Works, which is an interesting company. I've never heard their "Andra" or "Ivy" speakers but I know that the latter was commissioned by Bob Ludwig who is one of the world's greatest mastering engineers. Their speakers all use dome tweeters (mainly Dynaudios), incidentally.

Andrew