Some ask for direct comparison of active vs passive of the same speaker and I have done this many times. SCM 40 passive vs SCM 40A active, plus SCM 50 passive vs SCM50 Active. In both cases using ATC P1 or P2 amps to drive the passive. So this yields the same exact speaker, same exact model, same exact amp design and same exact output devices in the passive amp vs active amp set up. Pretty much a direct comparison except the cable being a factor, I used Cardas 6 foot clear light speaker cable and Cardas clear light 6 foot XLR line cable in both.
I have done this at shows and at home as well as the shop. I'm the US ATC importer so obviously I have to do this to be informed and accurate in answering people's questions. I was also the one who provided the passive and active ATC 50s to Neil Gader for his review in Absolute Sound.
The simplest way to state the comparison is the tone and timbre (frequency response) are the same between active and passive, the difference comes in image and resolution. The actives image much better and more finely resolve things like reverb tails, harmonic structures of complex instruments like piano and "room sound" - elements of a recording that reside in the background of most recordings. You can hear placement of instruments more clearly and hear the ultra fine details of the microphone/gear used in the recording process. For example, in Stevie Ray Vaughns live recording of Tin Pan Alley, you can tell the microphone Stevie uses for his vocals is a dynamic mic, as the bandwidth of the instruments is much wider in bandwidth than his vocal mic.
Most of the negatives I read in this thread are from people not really understanding the simple difference. In its most simplistic difference is there is nothing to be improved or gained with a large quantity of copper (wire) and inductors/capacitors (passive crossovers) placed in line between the amp and the driver. That's it, in a nutshell. The endless arguments over cable should be evidence of the sonic influence of cable/copper/silver/wire/etc. This "passive" solution may be the best idea if you like to play around with different sonics, changing amps, cable and all the rest and it IS fun. But removing all this copper and inductors/capacitors and wire DOES have direct performance benefits.
The most significant advantage IMHO is the ability to create linear phase of a speaker, by controlling the individual phase of the drivers. The second advantage is precise level calibration of individual drivers which can vary by 1/4 to 1/2 dB or more from unit to unit (even more variance in machine produced drivers). Passive crossovers do not offer this kind of adjustment. The third advantage is avoiding the change in sound of drivers/loudspeakers as they heat up (power compression for example). The values of the combo of driver/passive crossovers begin to change with temperature changes (increases) therefore changing the sound of the overall speaker. This is most audible after long periods at higher level, such as experienced in a recording studio where a mix session can last 10-12 hours at 85-90dB SPL (or more). [note: listening at low level for an hour may not reveal this temperature issue so this may not affect every passive speaker the same. Some drivers have better cooling or venting than others so there is variance in this side affect among loudspeakers based on driver design and length of listening sessions]
With a properly designed active the differences in the front end are far more dramatic than ever before, yielding just as much fun in experimenting with cartridges, tonearms, DACs, etc. So from my experience, active enables even greater insight into the minute details of recordings and all the associated gear.
Brad
Lone Mountain Audio
TransAudio Group
ATC USA Pro and Consumer
