If you can find a pair, the Urei 813 studio monitor is an excellent bargain. Deep bass, a time-aligned crossover, and the foam UREI horn takes care of many concerns with the original Altec/JBL drivers. UREI also QCed and blueprinted every driver used in their speakers. UREI speakers were used throughout American studios in the 1980s and can still be found in use even after all these years. There are three different iterations - the original rare Alnico magnet Altec based 813, the ceramic magnet 813A with the foamed horn, and the JBL driver based 813B.
From Mix Magazine:
In the mid-’70s, UREI founder Bill Putnam—unhappy with the sound of the Altec 604 monitors in his United Western Studios—worked with UREI’s Dean Austin and Dennis Fink on ways to improve the 604. They replaced Altec’s multicell horn with a wider dispersion design and added a 15-inch Eminence woofer to boost LF output. Ed Long applied his Time-Align™ crossover techniques to achieve time- coherent, true point-source performance. Engineers and producers mixing on the system were so enthusiastic about its sound that UREI started producing the monitors as a commercial product, with the first UREI 813 debuting in 1977. Typically soffit-mounted, these large, double-15 monitors were ideal for the larger, higher-SPL control rooms of the time.
I was lucky enough to pick up a pair of 813As from a local speaker manufacturer. Mine were particularly well-cared for with intact foam on the horns. They are extremely heavy and required two (relatively) fit adults to drag them down the stairs. If you ever have the misfortune of having to move these monsters, make sure to remove the drivers beforehand.
So how do they sound? In a word explosively dynamic, clean and powerful. The only speaker that I've ever owned that truly captures what impact a drum kit can have. They also capture guitars and bass just right. Vocals are amazingly real with the ability to pick up the different types of microphones used.
Weaknesses? Maybe because of the large baffle area, these are not soundstaging champions. Most mixes never go beyond the sides of the speakers. Another downside is that the sound never truly opens up until these are playing very loud. This makes them unsuitable for apartment and condo dwellers. Because of this, they don't quite work with baroque music either. They are also a touch dry and unrelenting - a bad recording is well, a bad recording and they will certainly show you the weaknesses of your favorite not-so-well-mixed music.
If you enjoy hard rock, run them with a solid-state amplifier - bass was deep and controlled even with my McIntosh 250. However for the best overall sound I preferred to use my refurbished Dynaco Mark IIIs off of the 4 ohm tap.
Sadly the UREIs are sitting under the stairs in my new house with the drivers out and safely tucked away. For my current living conditions they were permeating my entire house with music - even at normal listening levels - annoying my other family members. So they will stay retired until I have a larger area to use them in.