Actually, actives do not wash out dynamic effects. Just another myth. I know a lot of people say that but it is simply not true. What actives do is keep the voltage transfer function constant. That sounds like a big deal but it is current, not voltage, the generates the force applied to the cone. So as the voice coil undergoes dynamic changes in impedance the current and resulting force applied to the cone still vary even though the voltage transfer function remails fixed. If you want to wash out dynamic changes in driver behavior you have to go to current drive.
Please do not quote the entire post just above yours. Over-quoting cleaned up.It's just double (3dB) . . . which is pretty much enough to account for crest factor and (passive) crossover losses (in a reasonably designed system). Some people will argue that the passive systems needs even more power, but I think that perhaps they exaggerate . . .
Oh yea, but I was thinking more in terms of draw from the wall though....I like saving a buck anywhere possible.
Parallel and series crossovers, however, have different nodes, and different resulting properties.
Again, the argument is flawed. What controls the driver is the current through the voice coil. It makes absolutely no different how that current gets there, directly from the amplifier's terminals or through a passive crossover. The only difference between active and passive is that with an active crossover the voltage transfer function is not affected by any variations in driver impedance.
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But when the values of the driver change, so does the transfer function. In a series XO things move such that things hang together, because everything affects everything. In a parallel circuit, HP & LP are independent.
dave
The linear components can only apply linear change.
As JohnK points out, current drive, which is really just current feedback, in active system that can and does dynamically respond to changing reactance
of driver.
Regards,
Andrew
That's not a trivial difference, and it's maybe not the only one. Depending on how you choose to look at it (perspective) the increased source impedance (caused by series resistance in the passive crossover) does change driver behavior (the higher the source impedance the more it behaves like current drive). There are even books on the subject
. that claim current drive reduces distortion. I haven't been able to measure it, but the theory's there . . .Hi Deward. I didn't say it was a trivial difference, but that the voltage TF doesn't change does not mean dynamic changes in the driver's impedance are washed out. That is the point that is missed.
I do agree that this is mostly a theoretical argument. both passive annd active speakers, parallel or series, can sound very good, or bad. It's more about good design than one or the other.
I do agree that this is mostly a theoretical argument. both passive annd active speakers, parallel or series, can sound very good, or bad. It's more about good design than one or the other.
I'm sure that's probably true . . .
I've just gotten so in the habit of thinking of "drivers" as having a constant Zin (of about 10k resistive) and equal sensitivity that I sometimes forget the "old ways"
. . . (actually I still sometimes use "passive" shaping circuits thrown in there somewhere to adjust the response, sort of like SL did between the mids).I'm always reading comments in these forums about amazing speakers that give fantastic imaging, soundstage beyond the speaker boxes etc.
I've recently been fiddling about with individual phase correction of drivers in my homebrew active crossover software, including many experiments and outright mistakes. The interesting thing is that many of the incorrect schemes sound exactly like people's descriptions of the best speakers they've ever heard. I can turn the 'correction' on and off in real time, and the results can be subtle or spectacular or both, depending on the choice of phase modification. A pedestrian orchestral recording can be transformed into a scintillating audio panorama: the flutes just there, the piano here, and timpani obviously at the back. The whole stereo image 'gels' and expands without any apparent detriment. I strongly suspect that a poll of listeners would identify the 'effect' as much better than the properly corrected version as long as you didn't tell them how it was achieved. The important thing seems to be to have artificially, and intricately, bumpy phase, different for each driver, in the crossover region - the effect reduces with steeper crossover slopes. The two drivers then presumably mix acoustically in the room in a very complex way that provides extra richness to the sound. Its result is actually not all that different to the extra richness that you get when you flick the Dolby Prologic button on your TV remote. It's not too far off the methodology of the 'Stochastic Interleave' function I mentioned a few posts back (which isn't meant to give an artificial enhancement) and which I still haven't got round to trying, not deliberately at least.
So my question is, are you sure you audiophiles aren't really chasing an artificial effect that could be arrived at very easily using an active system with an effect button or a couple of extra speakers a la Dolby Prologic? If a combination of strange rear- and side-firing drivers, drivers driven beyond their range, room treatment ('diffusers'?) and dodgy passive crossovers happened to give you the same result I think you'd ooh and aah about it, but in reality it would be just an artificial effect.
Having said all that, I'm a bit of a purist at heart, so I won't be using a magic effect button myself, but I'll bet I could sell speakers that had it permanently enabled.
I've recently been fiddling about with individual phase correction of drivers in my homebrew active crossover software, including many experiments and outright mistakes. The interesting thing is that many of the incorrect schemes sound exactly like people's descriptions of the best speakers they've ever heard. I can turn the 'correction' on and off in real time, and the results can be subtle or spectacular or both, depending on the choice of phase modification. A pedestrian orchestral recording can be transformed into a scintillating audio panorama: the flutes just there, the piano here, and timpani obviously at the back. The whole stereo image 'gels' and expands without any apparent detriment. I strongly suspect that a poll of listeners would identify the 'effect' as much better than the properly corrected version as long as you didn't tell them how it was achieved. The important thing seems to be to have artificially, and intricately, bumpy phase, different for each driver, in the crossover region - the effect reduces with steeper crossover slopes. The two drivers then presumably mix acoustically in the room in a very complex way that provides extra richness to the sound. Its result is actually not all that different to the extra richness that you get when you flick the Dolby Prologic button on your TV remote. It's not too far off the methodology of the 'Stochastic Interleave' function I mentioned a few posts back (which isn't meant to give an artificial enhancement) and which I still haven't got round to trying, not deliberately at least.
So my question is, are you sure you audiophiles aren't really chasing an artificial effect that could be arrived at very easily using an active system with an effect button or a couple of extra speakers a la Dolby Prologic? If a combination of strange rear- and side-firing drivers, drivers driven beyond their range, room treatment ('diffusers'?) and dodgy passive crossovers happened to give you the same result I think you'd ooh and aah about it, but in reality it would be just an artificial effect.
Having said all that, I'm a bit of a purist at heart, so I won't be using a magic effect button myself, but I'll bet I could sell speakers that had it permanently enabled.
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Yes, dull flat reproduction of music and recorded sounds is much more accurate than anything that sounds real.
Please forgive my sarcasm, but I hear this argument all too often. If it sounds better, it must be wrong. I disagree. There are funky tricks one can do with phase, a number of these have been discussed across the forum. But funky phase tricks are not the only way to achieve sonic realism. Actually getting the phase right opens up amazing windows into the recording - without the downside that sonic tricks can bring.
Being a purist does not mean you have to stop at flat and boring. Top performing systems can give the sense of reality without gimmicks.
That said, I don't mind a well placed gimmick or two. I have a Yamaha DSP-1 that produces 4 channels of ambient sound. Used judicially it can do a lot to help envelopment and involvement. Not as good as true multichannel recordings, but fun for the majority of stereo (and even some mono) recordings.
Please forgive my sarcasm, but I hear this argument all too often. If it sounds better, it must be wrong. I disagree. There are funky tricks one can do with phase, a number of these have been discussed across the forum. But funky phase tricks are not the only way to achieve sonic realism. Actually getting the phase right opens up amazing windows into the recording - without the downside that sonic tricks can bring.
Being a purist does not mean you have to stop at flat and boring. Top performing systems can give the sense of reality without gimmicks.
That said, I don't mind a well placed gimmick or two. I have a Yamaha DSP-1 that produces 4 channels of ambient sound. Used judicially it can do a lot to help envelopment and involvement. Not as good as true multichannel recordings, but fun for the majority of stereo (and even some mono) recordings.
Most people have DACs in their system which are a long way from being transparent, but naturally enough do not realize this. I didn't myself for a long time - that's because noise modulation, the major cause of lack of transparency - doesn't have an accepted measurement. So we get people like Ethan Winer giving out lists of measurements for transparency which don't include it.
It may "depend" on what your definition of "wonderful" is.
Flip the polarity of one side - or better yet of just the mids and highs on one side - and you can get some pretty spectacular imaging. You'll also get a hole in the middle. If you pay attention, you'll soon hear that it's just a fun trick with some unpleasant consequences. There are better, more satisfying ways to get good imaging.
Flip the polarity of one side - or better yet of just the mids and highs on one side - and you can get some pretty spectacular imaging. You'll also get a hole in the middle. If you pay attention, you'll soon hear that it's just a fun trick with some unpleasant consequences. There are better, more satisfying ways to get good imaging.
I tend to agree with CopperTop on this. The real benchmark should always be the live event. In a concert hall I never heard "the sound stage expand beyond the room boundaries" or "room filled with music", the musicians usually just play in front of you.
Such artificial effects may sound impressive at the first moment but get tiresome rather quickly.
Such artificial effects may sound impressive at the first moment but get tiresome rather quickly.
Can't say I've heard "outside the walls" in a concert hall, either. But "room filled with music", yes. That said, if the recording and your speaker give you a sense of a concert hall that is bigger than your listening room, is that wrong?
My point is - don't confuse phase tricks (or even mistakes) with speakers that reveal a better picture of what's going on in the recording. The problem being that both of those can sound similarly surprising at first listen. I think that most of us here care enough to listen and learn which is more accurate. I'd hate to see speakers with really good, accurate imaging lumped in with silly phase tricks. It's not the same thing, even if the effect is sometimes similar.
My point is - don't confuse phase tricks (or even mistakes) with speakers that reveal a better picture of what's going on in the recording. The problem being that both of those can sound similarly surprising at first listen. I think that most of us here care enough to listen and learn which is more accurate. I'd hate to see speakers with really good, accurate imaging lumped in with silly phase tricks. It's not the same thing, even if the effect is sometimes similar.
Fiddling about is steering driver array where driver bands overlap; thus more pronounced with shallow slope filters.
Depending on driver separation two complete sound fields are present; room fills with pattern much like rings in water with stones dropped simultaneously a small distance apart.
With phase highly controlled it is easy to see crossover point by simply moving the microphone around:
Regards,
Andrew
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But unless you're listening in an anechoic chamber, you can't avoid phase tricks anyway, even if they're unintentional. You say that discerning people can learn to distinguish between accuracy and phase tricks, but in real rooms how could they? Isn't a multiway speaker always going to constitute two or more sound sources with different directionality characteristics, whose drivers are individually 'phase processed' by the room, and mixed acoustically i.e. artificial phase trickery? At an audio show I heard speakers recently that had rear- and side-firing drivers that, to me, seemed to resemble an audio equivalent of that Philips TV trick of projecting 'ambience' onto the wall behind the set - and sounded terribly 'comb-filtery' to my ears. Open baffle seems to be a similar trick in a real room, even if, ostensibly, there is a different rationale for it. It just seems to me that while my phase manipulation above is a clear 'trick', the interaction of beaming drivers and imprecise crossover filtering with the room is simply a less obvious trick.
As always, I'm sceptical that speaker designers know secret stuff that they're just not telling the rest of us. And in these pages I just don't read anything that convinces me that speaker design is anything but a case of following a few rules of thumb, and pot luck when it comes to the finer points of toeing-in etc. Maybe the phase effects of a particular room sound good with that speaker, and maybe they don't. At least the active DSP people have some better control of things, but it's never going to be a precise science. I'd love to be proved wrong, though.
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