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In Reply to: RE: about Absolute Polarity posted by b.l.zeebub on December 18, 2008 at 03:52:08
with even ordered slopes invert polarity, You can correct this by simply inverting the leads to the drivers which simply follow the signal and is passive in that regards.
The issue is that many designers invert polarity in order that the adjacent driver(s) produce a steeper crossover slope due to the cancellation effects. This can give a more even amplitude response but totally screws up the timing information, which ultimately gives a better cues for soundstaging, individual tonality and such. Properly selecting crossover points to minimize the overlap can work equally well, in my expereince.
IMHO there is no real advantage for an active crossover except in the case where you really need more power. After all, the crossover circuit in the active unit still follows the designs of a passive one, except in a digital crossover design. Being an analog guy, I find that adding such a design to my system destroys certain aspects of the sound I am achieving and seeking.
Of course, YMMV.
Stu
Stu
Follow Ups:
IMO the real advantage of an active xover is that they do not smear transients like passives do.
And the lack of phase issues and distortion. They do add a bit of noise though.
Analogue active xovers (like mine) do follow the design of passives with one major difference: Inductors are replaced by opamps. An infinitely superior solution, your transients will thank you and the bass response will be much more defined (due to a) the lack of an inductor in the signal path and b) the full benefit of the associated amps damping).
I have had the chance to directly compare a number of active speakers with their otherwise identical passive brethren and the result has always been the same: Actives are more accurate and passives 'mushier'. If 'mushiness' is what you seek then actives are not for you; in all other cases actives are clearly superior.
Again, I do admit my experience is limited with active rossovers. One with which I have extensive experience with has been the Marchand which is remote controlled and adjustable which makes for inteesting comparisons of speaker topologies. It also has a choice of different order crossover networks, IIRC.
Still, if a speaker is properly time aligned and phase aligned from inception I find that the added complexity of the system takes away from the overall presentation. Curiously I get tighter and more coherent sound in my experience from top through bottom in the avoidance of an active system. I'm not saying that it can't be done, however, just that it makes things more difficult.
As I said YMMV.
I have also listened to several active loud speakers and have found that the vast majority of those I have listened to have serious issues with time and phase. To be quite honest I do not recall any that were as well aligned as some passive speakers I have heard. Of course part of the issue is the amplification modules which are used with many speakers. Many are not up to high end, high resolution standards, a problem I find with many subwoofers these days. Again, YMMV.
Stu
I on the other hand am not aware of any higher quality main monitors which are not phase compensated. This may not be immediately visible but its easy to do electronically.
The problem is that they are all pug-ugly as they are designed to be soffit mounted but can also easily be used free-standing if one can live with the looks.
My own 4way actives are also completely phase compensated and pretty much retain the point-source character of the Tannoy DC they are based on. There is a slight timing error of <3microsec though. Not actually audible.
For high quality active monitors you might want to check out ATC 150, 200 and 300 from their pro series or Quested HM412 and HM415. They might seem expensive but I doubt you could buy the components for less.
Sadly there are no more high-quality analogue active xovers being made today (I have no experience with Marchand products) I am aware of so I will keep modifying my old BSS 360s.
It is actually a lot easier to design active speakers from scratch then passives.
It just costs a lot more to implement…
I am far from an expert, but this looks like an analogue active xover.
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