ATC 100 SCM Monitor DIY

The pic in your file linked to has them driven by ARC amps I believe. These amps if tube designs will almost certainly change the balance and further screw around with the crossovers in these speakers - not purely an opinion as I'm certain it can be measured. The ATC active amps are precisely matched to the drivers used and if any of the drivers needs replacing, the phase and level matching needs to be precisely set, due to the mid dome not having any workable overlap as most two or three ways have (this is the main issue with this driver and in the past, no two batches were ever the same*). What I 'suspect' you're preferring is this extra compromise built in to the passive models and of course, bit expensive Top End amps always look better than a rear mounted plate with fins on and little else... earlier passive 100's I knew well always sounded inferior to the active version and it didn't matter one jot what the amp was! Back then it was only £1500 to convert a pair to active at the factory - probably several thousand now I admit I haven't heard the latest 100ASL's, but note the current ones have returned to having mid and top level controls, which mine lacked and really needed in the location I had them in. of course, domestic users don't have the same needs as pro's and hopefully you'll forgive me for having a toe in the pro side still, even if the rest of the feet are bridging the gulf between the two needs..

* Apologies, I had too many lunches with the powers that be in this company back in the day and many 'secrets' came out, one of them being the rather narrow bandwidth of the mid dome, how variable it was in production and how critical it is in these designs (when used as monitors especially) to get the driver matching spot-on for phase as well as frequency of the crossover. There was a sometimes heated thread on the defunct Zero gain forum about how compromised the ATC mid dome was when looked at on its own and PMC eventually abandoned their use and had a similar one made by Audax at the time due to the ATC's being so variable (PMC's Pete Thomas himself told me, so there!).

Have you heard these - Half the price of new ATC 100's and fabulously open, passive or otherwise -

A bit full of themselves sat on the floor, but I'm wondering if lifting them 30cm or so might not sort that. The tweeter in its waveguide is sublime and shows how well a 15" bass-mid can work with a tweeter, something the BBC types deny ('cos the current people lack the nous to try it and their market probably won't let them anyway!)