Following on from the last entry on mastering dubs, I found this interesting excerpt from the Rane Notes series: Setting Sound System Level Controls:

"For sound systems, the maximum loudness level is what is achievable before acoustic feedback, or system squeal begins. While the minimum level is determined by the overall background noise. It is significant that the audio equipment noise is usually swamped by the HVAC (heating, ventilating & air conditioning) plus audience noise. Typical minimum noise levels are 35-45 dB SPL (sound pressure level), with typical loudest sounds being in the 100-105 dB SPL area. (Sounds louder than this start being very uncomfortable, causing audience complaints.) This yields a typical useable system dynamic range on the order of only 55-70 dB -- quite different than unit dynamic ranges".

This nicely demonstrates the difference between mastering dubplates (for use on sound systems) and mastering on other formats for listening say at home. This should not be seen as an excuse to compress tracks more than normal, but it does highlight the dynamic limits that are available when producing and mastering tracks for club use.