ok, I just got a Scumback M75-PVC and compared it to a the Celestion G12M Heritage.
The Celestion is more aggresive in the upper mids, specifically it has around 4dB more push between 2.5 and 4k (Vintage 30-esque). It also has a little less low mids (2-3dB around 200 or 300Hz). These descriptions are better for me as they paint a clear picture but, in rock and roll speak, the Scumbacks are warmer, less spikey in the upper mids, thicker in the low mids and 'broader' and sounding. High end seems about right with my Marshalls, and is little more rolled off than the Heritage.
The are however 'looser' as expected, meaning chunking on the lower strings doesn't have the definition or firmness of the Celestion. Not a bad thing, they are overall aiming to reproduce the sounds of mid-60's speakers - not really for hard rockers
I really like the PVC though, very nice speaker. Before installing it the Heritage was my favourite greenaback type speaker I've tried (over the M75, G12M ri, 70's Blackback, 60's pulsonic).
Another winner for Scumback
