Hi Paul,
Welcome to the dark side !
Yes, they are extremely reliable and can handle a very high SPL. Remember, these speakers were originally made for theaters. They were not designed for home hifi.
The Altec 19 is the "Vott for the home".
But some examples were badly treated by their owners during all these years so you must be very careful if you decide to buy a pair and cannot listen to them.
Some compressions can also be in bad shape. We are talking of drivers that are often more than 50 years old and had often numerous owners.
The 416-A ( Alnico) Altec driver is certainly the best driver up to 800-1200 Hz depending on the set up, ever made on earth. The GPA 416-8B is very close though.
These drivers do not go very low but the bass they give is just the most natural one imho.
My 414A is not very far.
The problems with the VOTT and any vintage Altec speaker are :
-are the drivers in good shape ? And if they were restored, was it done properly ?
- how is the filter ? I think that the need for a tweeter comes from a filter not designed correctly. The VOTT is originally a two way speaker. And that is how it sounds the best imho, when the filter is properly made.
High Eff systems who sound the best are the most simple ones. 2 drivers. A compression with its horn and the "boomer". The Altec compressions are more than enough to reproduce natural music at realistic levels. There is never the feeling of missing some highs.
Look at the 19, the Shindo Latour, the Valencia... You won't find any tweeter or super tweeter. Just two way plain and simple designs.
My friend who built for me my speakers made a remarkable filter, especially for my drivers. He measured everything and listened.
Well made Altec speakers sound like heaven. Nothing comes close to them.
Look on the web for the many japanese set ups using VOTTs or TADs speakers. The rooms are not huge. The VOTTs can be used in rooms of only 20-25 m2.