The SSL mix room was opened in the early 80s, it houses an SSL 6048 E desk which is fast becoming a classic sound.
There is an overdub room which is big enough to track a band in, full drum kits and other acoustic instruments are easily recorded, although it's most often used for vocal, guitar and percussion overdubs.
The most important thing for a mixing room is that it be as "true" sounding as possible. i.e. what you hear when mixing is what you hear when you take it away. The Konk SSL room is renowned for being an exceptionally true and honest room in which to mix records.