I used LS3/5a speakers from 1976 - 2001 continuously, in either primary or secondary systems. They certainly stand as one of the landmark speakers of post-war audio history with longevity and relevance matched by few others. How do they stand up against current monitors? It depends on your frame of reference.
Like Quad ESL-57s and Apogees, the LS3/5a won its reputation on vocal fidelity and in this respect it was and remains exceptional with respect to human tone, its communication of expression and its general sweetness. Also, the original 15ohm impedance was beneficial to the sound of most solid state amplifiers. So while a tube amp really was needed to make them sing, the LS3/5a was a speaker that could make most solid state amps sound much more expressive than their performance and design otherwise led you to expect. They were one of the first speakers to demonstrate the imaging that could be achieved by a near-point-source speaker, and they made the case for very stiff cabinets.
The tonal excellence of the LS3/5a is compromised by its dynamic compression and some people found the euphonic bass bump that was engineered into the speaker to improve the listener's perception of full-range performance to be annoying. The LS3/5a was a fully engineered system with every aspect of its manufacture considered in the intended outcome. Drivers were KEF B110 with bextrene cones, advanced for 1971, and KEF T27 soft dome tweeters. There is a 15 element crossover playing traffic cop on the routing of signal to the drivers. The cabinets were specific density birch ply, if I recall correctly, and even the grill and the felt strips isolating the tweeter were critical to the sound. One thing often neglected in the equation were stands. For most of this speaker's life, stands were not very well conceived or made. I got a nice surprise around 1998 when I got a pair of Osiris stands for them, filled with shot and sand. I found a distinctly elevated level of performance compared to any stand I'd been able to find in the prior 22 years of using this speaker.
There are modern speakers that will outperform the LS3/5a in nearly every respect, and yet matching its midrange vocal expression is elusive even for those contenders. The Spendor S3/5 and S3/5se are both generally superior but not equally magical. Certainly their bass has more definition and discipline, and their dynamic performance is better. The larger Silverline SR16 sounds more like the LS3/5a midrange, and goes deeper, is more efficient and dynamic, but in its larger size gives up some of the uncanny imagining of the tiny Brit.
The big difference between what is possible now vs. when the LS3/5a was designed is primarily realized when you compare it with a newer breakthrough, which is the Zu full range driver. This allows you to hear a tonally rich and accurate speaker with excellent vocal expression, without the amp forcing the signal through a crossover, let alone a 15 element passive circuit. Prior full range drivers could not deliver any semblance of the BBC's midrange accuracy without annoying shout. The Zu driver can. So, at adimittedly more cost and larger size, a pair of $1700 Zu Tones will make the LS3/5a sound dated, and the presence of its dynamic constriction will suddenly seem unacceptably annoying and distracting.
However, if all you ever compare an LS3/5a to is other midget two-ways with complex crossovers, then it will remain competitive, though clearly more colored than, say, the Spendor update or, tellingly, the MUCH more expensive and excellent Sonus Faber Cremona Auditor. While the Spendor is the closest modern equivalent, I consider the "voiced" Cremona Auditor the 21st century spiritual equivalent to the LS3/5a in terms of emotional projection in domestic circumstances. However, at 4ohms, the Cremona Auditor demands a much more capable amp to sound good. The LS3/5a, in later 11ohm or preferred older 15 ohm form, makes alot of mediocre amps perfectly usable again.
Why doesn't someone in China just knock off the LS3/5a? Well, it could be done, but two critical elements are missing -- the KEF drivers are no longer made. Certainly many equivalent modern alternatives exist that are better in every objective sense. An alternate speaker can be engineered to attain the same BBC objectives and many companies can and do such a thing through designs that are outwardly similar but duplicating of nothing from the BBC spec. Without the KEF drivers, along with everything that can be duplicated, you're just not going to get the same speaker. You might however get a speaker you like better. An LS3/5a aficionado might not agree, and hence the climbing prices.
Phil
