Stevie Ray Vaughan's musical influence has really hyped the blackface Fender Vibroverb. Because of him the Vibroverb has became the most expensive and sought after blackface amp on the vintage amp market. Though the Vibroverb is closely associated with SRV you can reproduce his tone with most Fender amps given the right speakers. Since Fender did not continue the Vibroverb after the CBS takeover in 1965, most likely because players didn't desire 1×15" amps at that time, there are only a few blackface Vibroverb amps out there. Given the hype and popularity, these few Vibroverbs are extremely valuable and collectable. So special with the Vibroverb, the 15" speaker sets it apart from most guitar amps. While most guitar amps have multiple 10" and 12" speakers, the Vibroverb came with a big Jensen C15n or a JBLd130f, the last one with a huge magnet, aluminium dust cap and flat speaker cone that can be hard to tame in terms of treble, punch and attack. Beside the speaker the blackface Vibroverb is very similar to the other Blackface and Silverface AB763 Fender amps. In fact, there aren't any different features or technical improvements in the Vibroverb that justifies its popularity. It's all about emotions. The Vibroverb belongs to the 6L6 Fender family. It is powerful and loud, but in a different way than the 10" and 12"-amps. The Vibroverb did not sell very well in '64 and '65. The Vibroverb did score among steel guitar players at the time. The 15" speakers are firm in the bass and have lots of sparkle but most importantly, they have an enormous spread carrying the lower mids to anyone on stage. Mid frequencies is exactly what you need on stage in an electrical band. The mids will blend in nicely with the bass, drums, piano and horns. It will not interfere with the bass like a 4×10" setup does. Of course this is a matter of taste, but a guitar tone with strong mids will contribute to a rich overall melodic footprint in a band.