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Old 26th October 2012, 09:27 AM   #521
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My perception of active systems (from my own experiments, and having heard various hyper-expensive actives and passives at a show) is that they are more 'linear' in the sense that they don't change character dependent on volume as much as passives. This thread has mainly been concerned with the accuracy of the frequency and phase response, but I think what I am talking about is independent of this; I am reasonably persuaded that our ears can compensate for inaccurate frequency/phase response.

My perception is that passives begin to sound strained at high volume, while the actives just keep on keeping on. If so, what would be the technical reasons for this?

It could be amplifier-related or maybe it's that steeper crossover slopes help - although I'm pretty sure that actives are better even at shallower slopes.

Do passive crossovers change character as power increases? We are told that air-cored inductors don't saturate, and that heat isn't a problem with normal listening levels.

Are there more implications to high series impedance than simple frequency response issues and damping? Does it also contribute to harmonic distortion/IMD in a real world driver as opposed to the simple models, especially at higher volumes?
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Old 26th October 2012, 10:28 AM   #522
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CopperTop, that pretty much reflects my experience too but every theory I have had has been shot down by someone at some point so I too would like to know.
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Old 26th October 2012, 11:07 AM   #523
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i guess high reactive currents in capacitors which arent rated sufficiently, could change in character, but id suspect an equivalent line level filter wouldnt show the same. That would lead me to believe the 'strain' would be from driving an awkward load or over stretching the amplifier, rather than a 'passives are evil' arguement.
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Old 26th October 2012, 11:23 AM   #524
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Quote:
Originally Posted by CopperTop View Post
My perception is that passives begin to sound strained at high volume, while the actives just keep on keeping on. If so, what would be the technical reasons for this?
A couple of possibilities I can think of. First since passive XOs have a non-zero insertion loss, the amps are going to be working harder to create the same SPL (all other things being equal).

Secondly the higher source impedance (which also rises with frequency due to skin/proximity effect in air-core inductors, and core losses in non-air cored ones) in the passive case will result in higher distortion of the voltage waveform at the bass driver's terminals, due to the driver's non-linear input impedance. But drivers are current driven so I don't know if this additional voltage distortion is at all significant in practice.

<edit> A third one has come to mind - for a given IMD performance, two amps reproducing restricted portions of the full audio spectrum will output lower distortion products than a single amp will. This effect does though have to be offset against the fact that IMD products outside the driver's passbands will be subject to attenuation in the passive case, not in the active one.
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Last edited by abraxalito; 26th October 2012 at 11:41 AM.
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Old 26th October 2012, 11:32 AM   #525
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I'll add to your list.
The non linear change in passive component parameters will probably be much greater than for the active (pre power amplifier) components, as output voltage changes with signal level.
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Old 26th October 2012, 12:04 PM   #526
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well, if you have small 2way I doubt playing loud will be any issue at all
and how about all the 2.5way speakers ?

as for the louder speakers you are talking about, yes they will probably mostly be active anyway
or what ?

but hey, that actually sounds good
I can throw together some fancy designs
just mount some drivers
and when asked about crossovers, I would just say, hey, thats your job, they are active, right ?
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Old 26th October 2012, 12:27 PM   #527
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skin effect at audio frequency in a coil of values typical in use and typical inductor size is a non issue, possible but probably the smallest contributor. The case for band limited amps is clear IMHO, but resistive insertion loss is less so. What distortion does such loss create if you have a capable amp in the first place? Multiple amps for multiple bands? Best idea yet. Does that place actiue filtering as the next best way to prevent distortion? Unlikely. Many more discretes and their losses to contend with, just as with the amp selection is just as valid. A good active filter SHOULD be better, but ANY active filter certainly is not.
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Last edited by mondogenerator; 26th October 2012 at 12:32 PM.
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Old 26th October 2012, 02:36 PM   #528
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Quote:
Originally Posted by CopperTop View Post
My perception is that passives begin to sound strained at high volume, while the actives just keep on keeping on.
How high a volume are we talking about? I can ceratinly understand that in P.A. application - tho Danley's Unity Horns seem to do OK - but in small rooms?
Do you think it's related to the drivers?
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Old 26th October 2012, 02:51 PM   #529
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If there's a difference in the dynamic range/compression of my speakers before and after I went active, I sure couldn't hear it. And when I first got them, I will admit to cranking a few albums into the three figure SPLs...
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Old 26th October 2012, 02:56 PM   #530
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Quote:
Originally Posted by Pano View Post
How high a volume are we talking about? I can ceratinly understand that in P.A. application - tho Danley's Unity Horns seem to do OK - but in small rooms?
Do you think it's related to the drivers?
Perhaps I should clarify: I'm referring to loud transients more than just sustained high volume narrow dynamic range stuff. My perception is that the actives simply deliver more 'punch' i.e. the recording demands a ten-fold increase in volume at the end of an orchestral crescendo, and the active delivers it. The passive (to my perception, at least) gives 95%. That may be an actual compression of dynamic range, or simply something like distortion conveying a sense of the system being 'strained' or running out of steam.
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