I recently listened to the Proac D48 and the Vandersteen Quatro in the same room with the same electronics (Audio Research Ref 150 amp and Ref preamp with ARC CD) The Quatro's were setup first. My impressions: A very balanced and cohesive sound. Detailed yet smooth....natural. Nothing really called attention to itself. Yes, the detail, midrange, highs, and lows were all there but nothing made you think "wow, listen to that". Very engaging. The powered subwoofers had just the right amount of visceral impact and were only heard when it was their turn to play. Also, great looking speakers.
Next the Proac D48: The dealer removed the Quartos and replaced them with the D48s, After a few minutes of meticulous setup which involved tape measures and levels he invited me back into the listening room. We went through the same music in the same order we had with the Quatro. The first thing I noticed was the bass was missing but soon discovered in the process of switching out the speakers the dealer had forgotten to remove the high-pass filter between the pre and power amp. As soon as this was corrected we started over with the music and the speakers bloomed with deeper and fairly substantial bass. I will compare the bass between the D48 and Quatro first since one of the first musical pieces, "Hotel California" from the Eagles "Hell Freezes Over" cd contains that deep bass drum in the intro. Both speakers went low but the Quatro did so with a more visceral impact whereas with the D48 the bass bloomed. No doubt the built in sub on the Quatro was IMO better able to recreate the impact and the depth of those low drum beats.
Having said that, the Proac had plenty of low bass. In fact there were few if any other instances during the listening session I that noticed any difference in the bass between the two speakers.
The D48 was maybe just a bit more in your face with the midrange. A liveliness and immediacy that I have always enjoyed with every Proac I have listened to. Overall it was difficult to find fault with either speaker. To my ears the Quatro had a more natural sound, slightly smoother and less etched with all the details there but just not calling too much attention to itself.
The required high pass filters for the Quatro will add nearly a thousand dollars to the price (for balance connection; single ended are slightly less expensive).
Overall I preferred the Quatro. To my ears it just a slightly more of a natural sound and more cohesive presentation. Also, I like the ability to tune the bass to your particular room.
I hope you will share your impressions after you listen to the Quatro. Also, I hope the poster "aka_ca" is still following this thread and I hope he is familiar with the Quatro...and I really hope he can share his impressions of the two speakers as he did comparing the Tannoy to the D48.
"TANNOY .... bespoke refined, ethereal, XO Cognac snifter
PROAC .......forward striding, bold, Quatro-Cinco tequila shooters..."