There is a fast tacking pva known as FVS or flexible sheet veneer that can be used somewhat like contact cement, rolled on and pressed down with a veneer hammer or similar hand pressure, but it is made for use with paperbacked veneer. I have had reasonable luck with it in spots that were impossible to press, though with occasional edge curling that had to be clamped down.

There are hot melt adhesives in sheet form that can be pressed with a hot iron. I don't know how well they work with raw veneer. I would be leery of using them for a large piece. Some people have success rolling out pva glue, letting it tack then pressing the veneer with a hot iron.

It is possible to veneer an assembled box using a vacuum bag, which involves introducing a bladder at ambient air pressure inside the box, which is inside the vacuum bag, thus putting pressure on the veneer and box sides without imploding the box. Complicated, but possible.

If you are building the speaker boxes, it would be much more efficient to veneer a large sheet with a press, then assemble the boxes with parts cut from the sheet as John Bateman suggests. Vacuum press are quite common for cold pressing, though screw presses or even sufficient clamps and cauls work also. Pva is often used for cold pressing, with cycle times as short as an hour. Urea Formaldehyde is a more rigid glue and the most commonly used in industry, but requires a minimum 70F temp. They both can be accelerated with heat or rf. I think the portable "wood welders" start around $3k for a hand held unit with a fairly small field. That might or might not work for you.

It would be worth your while to check out the Veneer Systems website and talk to the owner, John Van Brussel. He is very knowledgeable about professional/industrial veneer practices. Another good source for supplies and advice is Darryl Keil at Vacuum Pressing Systems (vacupress.com). The site has a fairly active forum, and his videos on vacuum veneering are quite useful.