[midfiguy]

For a 12" Electro-Voice driver, I have seen recommended most often a 6 cu. ft. enclosure for running full-range. Yet, a cabinet such as the EV Marquis is nowhere near that large, and the 12" driver is only pulling woofer duties. Is it because the enclosures of that era had open backs?

[JCS]

The short answer is: a driver's Thiele/Small parameters (its electro/mechanical properties) will tell you what sort of enclosure will work best for a given driver.  You need to get your read on if you want to really understand how to design a speaker enclosure.  Until you buy a book or two on designing speakers, here is a place to start:
https://en.wikipedia.org/wiki/Thiele/Small_parameters

Cheers, Jim

[nickd]

Short answer is big (well designed) boxes and big paper woofers just maker better bass.
You can’t cheat the laws of physics on a budget. Efficiency is king, a 16” Altec 416-8C or a 3154 (now made by Great Plains Audio) in the proper box (about 6 cubic ft) will change everything you think you know about speakers. They will also embarrass $200,000. Audiophile models, usually machined from solid un-obtainium.

The big paper woofers just flat out rock and sound real, even with a good 40 watt amp. If it’s well engineered, you don’t need 1000 wats of amp power to get good sound in your home.

The down side, 2 big pieces of furniture in your listing room. My wife used to decorate them at Christmas. She actually liked the vintage look. 

Good luck on your project. Think you’ll like the results.

[Tyson]

Small, deep and efficient.  Pick 2.  That's physics. 

[FullRangeMan]

For a 12" Electro-Voice driver, I have seen recommended most often a 6 cu. ft. enclosure for running full-range. Yet, a cabinet such as the EV Marquis is nowhere near that large, and the 12" driver is only pulling woofer duties. Is it because the enclosures of that era had open backs?

Well these classic EV FR drivers were designed with the classic recipe from the FR drivers of that time that used a small cone excursion usually XMAX 1mm and a very soft suspension CMS what result in a huge VAS value i.e. require a big box.

In this AN Super15 datasheet below which also follow the classic recipe you can see:
-Cone excursion XMAX 1mm
-Air equivalent volume VAS 492L to Compliance CMS.
It need a big BR box, in case of a sealed enclosure the box required is even bigger.
https://commonsenseaudio.com/an15alnicospecs.jpg
Usually FR drivers have small cone excursion around XMAX 1mm to prevent they become woofers that works well in the bass freq but have no treble response useful.
Hope this make sense.