Solid State Logic (SSL) recently released LMC-1, a faithful recreation of the Listen Mic Compressor from SSL's legendary "E" Series console.
The SSL Listen Mic Compressor was originally designed to prevent overloading the return feed from a studio communications mic, its fixed attack and release curves were eminently suitable for use on ambient drums mics.
Featuring the same sound and dynamic response as the original unit, the LMC-1 plug-in is available for free in VST and AU formats for Mac OS X.