Amplifier to power JBL Voice of Theater Speakers

This kind of loudspeaker really will not sound right with transistors unless that transistor amp does not employ loop negative feedback (and most do).

Such amps tend to cause a speaker like this to sound quite shrill (and is part of the reason horns were often not taken seriously from about 1970 until about 1995). In addition, if the speaker is old enough (1960s or earlier; hard to tell from the photos) the crossovers might not work as designed if the amplifier has a low output impedance.

So the easy way to get them to sound right is with tubes. This speaker is likely no more than about 99db 1 watt/1 meter, so having a bit of power is nice. I have speakers of similar efficiency and so I use a set of our M-60 amplifiers which are triode and make about 60 watts.

The pictures look a lot like Altec Voice Of The Theatre. JBL speakers made early on (I own two pairs) offered cabinet styles and speaker crossover package to fill the cabinets with. So my C36s have the 030 If I recall correctly, using the 15 inch 16 ohm D-130 extended range woofer/mids speaker and the 075 titanium/aluminum Bullet horns also 16 ohm, and the N2400 crossovers.
Your speakers are from a later period, but make use of the JBL Lansing Heritage pages. In particular look at the product brochures in the "libray" section of the website.

I would also recommend a top notch tube amp.Atma-Sphere would be a first choice along with possibly Graaf,hot-rodded Mac 30-40 monos.......but start with AS,Ralph is a guy who will do the right things on all levels.......thanks,Bob

I dated a neurosurgeon's daughter in 1975, carded his ampitheater door, and checked out his stereo system. Voice of the Theater speakers. Massive beasts standing well over 6' high and ~3' wide. His Amp/preamp system was MacIntosh, a tubed system. He ran a reel to reel tape machine with classical music to unwind after a long day of brain surgery. I never had the cajones to fire up his system but I can still see it in my minds eye today. His budget was limitless so I would look for some older, high quality, MacIntosh equipment.