There's a factor that maybe is sometimes overlooked in measurements, and perhaps it doesn't show up clearly in typical audiophile music, but I think that I sometimes perceive a system 'pulling its punches' i.e where there should be a devastating transient, the system doesn't quite deliver. If this was the case (and not my imagination) I would point to a passive crossover as being a very likely culprit. The world class passive crossover may give a flat frequency response but it's still a high impedance in series with the drivers (that gets hot when driven hard), doing weird things with the phase, and it's absorbing a large amount of the amp's power.
With the expectation bias caveat, my active system just seems fabulously 'transparent' at all volume levels, and perfect with particularly meaty transients. I don't get this with my (on-paper far superior, and now hardly ever used) passive system.
The only elements in passive xovers that should get hot when driven hard are resistors and this is deliberate. Capacitors and inductors do have their own internal losses, but if correctly chosen should remain cool under normal operating conditions.
Passive xovers also don't do weird things with the phase, both passive and active alter it in the same way.
What proportion of the amp's power does a crossover absorb? 30% typically? So if the amp's delivering 50W or something like that, the crossover surrounded by stuffing is presumably going to get quite hot. I see a lot of speakers for sale on eBay with burned out crossovers, at any rate.
And I'm pretty sure that my linear phase filters and direct drive off the amp are doing something quite different with the phase, compared to the passive version..?
Edit: I have to admit that I have little knowledge of passive filters because I've only just started fiddling about with adapting my own speakers, and I've gone straight for the Rolls Royce solution. But reading someone else's stuff about passive crossovers:
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Active or passive or no crossover at all, people have gotten together to do blind tests with two fullrange drivers crossed over to each other, and could not tell them apart. The key is to get the same frequency response in each crossover. Make sure that the same DAC and amps are being used with active, if you want to compare.
Well the passive components increase the impedance of the total network to reduce the current flowing through the circuit and reduce the overall power dissipated by the circuit. How much any of the components will dissipate is determined by the slopes and xover points chosen. 30% seems quite high, but it really depends on the xover specifics.
Ah see, but here, we're not really comparing like with like and we're doing things that a passive xover cannot do, it's also something that is quite difficult to do with an analogue active crossover too if I understand it correctly. DSPs on the other hand are different again and add in yet another set of things to the mix that an analogue active xover cannot really do well. So in terms of potential usefulness you've got passive, then analogue active, then DSP driven active crossovers.
But if you compare a standard second order electrical passive filter designed with a specific driver to arrive at a 4th order acoustic LW slope, then it will have exactly the same amplitude and phase response as the system doing the same thing but actively using standard sallen key type filters.
Passive crossover versus active crossover? Hehehe.... active crossover is "crossoverless" so it should be better from speaker point of view. But don't forget that this is NOT about speaker (crossover) but about AMPLIFIER 
Yes, the active crossover is part of the amplifier chain. So the question is can you design a good amplifier. If you use discrete opamps and are an amp designer already, you may be able to create a good active. The question is: can your complex multi-stage amp outperform the best simple full class-A amp?
It is just similar like CFB versus VFB debate. Or who can make a better amp, NP or JC. Useless.
What many may forget is that people preference or hearing capability is different. Active will easily impress everyone, and it will (yes, sonic is what will be heard first by everyone). But only a few who can hear a hint of fatigue (or minor flaw in the amp design) and take that kind of performance seriously.
And then many forget that in crossover design you don't take any two drivers arbitrarily and make a crossover for them. Some combo will never work well. From this point of view it is clear that passive has real limitation, regardless of design skill.
Yes, the active crossover is part of the amplifier chain. So the question is can you design a good amplifier. If you use discrete opamps and are an amp designer already, you may be able to create a good active. The question is: can your complex multi-stage amp outperform the best simple full class-A amp?
It is just similar like CFB versus VFB debate. Or who can make a better amp, NP or JC. Useless.
What many may forget is that people preference or hearing capability is different. Active will easily impress everyone, and it will (yes, sonic is what will be heard first by everyone). But only a few who can hear a hint of fatigue (or minor flaw in the amp design) and take that kind of performance seriously.
And then many forget that in crossover design you don't take any two drivers arbitrarily and make a crossover for them. Some combo will never work well. From this point of view it is clear that passive has real limitation, regardless of design skill.
For example an active XO (as opposed to a PLLXO which have different issues & advantages) will introduce higher order harmonic distortion products (which the ear/brain readily detects at very low levels) that a passive XO will not have.
Some active XOs have very complex circuits. A pre-amp is very hard to make transparent, an XO will often have many times the circuitry.
As with everything it is all about execution.
I'm a fan of active systems but not unless they are well done.'
dave
By default, one that is in a system where the budget it less than the cost of the DEQX.
dave
Not if the active is digital, you can have linear phase, plus time delays to acousticaly align the drivers. You can change the xover freq, the filter slopes, the delays, the phase, the amplitude, etc very easily. You can use class A for the tweets and mids and D for the woofs and get (pretty much) class A sound with a punch for a lot cheaper than passive.
And manufacturers like Meyer and Genelec have long ago given up on passives, for a reason.
That is why i own a DCX2496, an XO only a mic could love (both examples i've used sound like crap, and i've not been motivated to install the full set of transformers to replace the shoddy analog section)
dave
I've used analog active crossovers and liked them. However it is easier to work with passive to make changes.
But the analog sections of digital crossovers sound like crap. Grainy. It would ruin the sound of the system I built with 10+ years of redesigning and tweaking with new DACs, analog stages, amp topologies both SS and tube, going through over 60 different speaker units. For a digital crossover I would have to redo each of the analog sections, or build own my digital crossover system. It's a lot of work to do it right, but it's on my list of projects.
But the analog sections of digital crossovers sound like crap. Grainy. It would ruin the sound of the system I built with 10+ years of redesigning and tweaking with new DACs, analog stages, amp topologies both SS and tube, going through over 60 different speaker units. For a digital crossover I would have to redo each of the analog sections, or build own my digital crossover system. It's a lot of work to do it right, but it's on my list of projects.
You're guessing wrong.
I matched the output using a 1/3 oct analyzer (the thing that was at hand) to within +-2dB from 50-20 000Hz.
At superficial listening one would say the bass output was less but that is because passive the bass sounded 'smeared' and 'bloated' while active it is 'tight' and much more 'detailed'.
Which is what my friend noticed since he has been playing bass for over 35 years and this was one of the few times it sounded like it does when he is playing his instruments (electric and upright).
This is commensurate with what I hear from people who have compared active and passive ATCs.
It's no surprise, that 2 different speakers sound different.
If you want to compare only an active and a passive crossover, you need to match the frequency response to within 0.5 dB.
You might be right, but to me, my system doesn't sound grainy at all. Whereas I did spend a day recently listening to 'high end' systems at a show, mainly valve and vinyl based, with many hyper-expensive passive speakers and horns, where the deficiencies were so obvious and the sounds so twisted and contorted that it made me question my fellow audiophiles' ears. Perhaps they worry too much about the wrong things, or only ever play tinkly piano music through the 5' diameter horns that grace their living rooms.
(To me, the definition of "grainy" is the last track on an LP, where it's moving painfully slowly).
There is no eq on the bass whatsoever with either the active or passive version, there is however eq on the treble which, being a horn, needs a notch at around 2.5k and a 6dB boost above 5k.
I had to reduce the gain of the woofer amp by 3dB to get an exact level match.
The FR on the bass should remain the same as the box and therefore the porting remained as before. The 3dB are commensurate with manufacturers literature who give a power rating of 100W (woofer) and 25W (tweeter) with the passive xover in place while the woofer itself is clearly marked 50W.
I had to reduce the gain of the woofer amp by 3dB to get an exact level match.
The FR on the bass should remain the same as the box and therefore the porting remained as before. The 3dB are commensurate with manufacturers literature who give a power rating of 100W (woofer) and 25W (tweeter) with the passive xover in place while the woofer itself is clearly marked 50W.
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