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Multi-Way Conventional loudspeakers with crossovers

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Old 7th November 2012, 01:57 PM   #671
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Quote:
Originally Posted by 5th element View Post
Well the IMD of the amplifier, or any of the non linear distortion products for that matter, should be significantly lower then any of those produced by the loudspeaker.
There is something wrong here. The amplifier (unless it's a very very good one), by virtues of typical Class-AB amplifier distortions such as crossover distortion, under/over biasing, thermal issues, power rail modulation, etc*... will produce all sorts of distortions including IMD distortion. And these are audible in the sense that they are removed or diminished by (a) going to a better amplifier like a class-A bjt amplifier, (b) going fully active so the amplifier working bandwidth is narrower, or (c) both.

To put your argument in other terms, a normal, decent phono cartridge with a conical stylus can produce up to 10% of harmonic distortion in the mid-high range and up to 1% of intermodulation distortion, far above what most amplifiers produce. Yet the improvement in IMD is readily audible when using better speakers and better amps.

* not to mention all the problems that are created by driving a reactive load of varying impedance... and an inductance value that is modulated with the signal!!

Quote:
Originally Posted by weltersys View Post
As far as distortion, any decent amp operated in it's linear range has a tiny fraction of the distortion of the best drivers when run hard,
See my posts above. There is much more to audio than what the THD specification say. See Earl Geddles papers on distortion audibility. Amplifiers that even show little THD under the ancient way of testing still can contribute audible, significant distortion on real-world use.

While some speakers can have rather highish THD on paper, but under the Geddles criteria such harmonic distortion may be non objectionable.

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Originally Posted by weltersys View Post
At any rate, if amp distortion and noise sound bad, in my experience it will sound bad with a passive crossover or an active crossover.
Again, if you're using a fully active setup then you're narrowing down each amplifier bandwidth, which should reduce IMD products.

Last edited by flavio81; 7th November 2012 at 02:00 PM.
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Old 7th November 2012, 02:32 PM   #672
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Originally Posted by weltersys
As far as distortion, any decent amp operated in it's linear range has a tiny fraction of the distortion of the best drivers when run hard,

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Originally Posted by flavio81 View Post
See my posts above. There is much more to audio than what the THD specification say. See Earl Geddles papers on distortion audibility.
I have read Geddes opinions, my previous mention of amplifier crossover distortion was in agreement with that being an objectionable type of distortion that can make low volume listening worse than high volume, as the distortion percentage reduces as power is increased.

As far as IMD and THD audibility in an actively driven driver at low to high drive levels, you can listen for yourself and decide whether it is an audible problem:
High Frequency Compression Driver Evaluation
A shorter version (only 3000 rather than 8000 words, and a lot less pictures) can be found here:
High Frequency Compression Driver Evaluation

The sound files in the soundforums.net posts do not have the low frequency portion of the music mixed in, listening to the HF horn alone makes it easier to hear the difference in sound quality and distortion between the drivers.

The IMD and THD of the drivers was certainly evident to me at any drive levels approaching the rated power of the drivers.
Earl has yet to comment whether he could hear the difference .

Art Welter
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Old 7th November 2012, 02:36 PM   #673
Pano is offline Pano  United States
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We are starting to get into the "Amplifier distortions are more audible than speaker distortions" territory - aren't we?
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Old 7th November 2012, 02:45 PM   #674
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Originally Posted by weltersys View Post
Originally Posted by weltersys
...... any decent amp operated in it's linear range........
which is mostly very limited
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Old 7th November 2012, 03:03 PM   #675
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Originally Posted by Pano View Post
We are starting to get into the "Amplifier distortions are more audible than speaker distortions" territory - aren't we?
Yes. And some are, and some are not . . .
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Old 7th November 2012, 03:26 PM   #676
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Originally Posted by Pano View Post
We are starting to get into the "Amplifier distortions are more audible than speaker distortions" territory - aren't we?
Yes but note that "Distortions" is a veeeery broad generalization where we should discern between very low order HD, higher order HD, intermodulation (and... at which frequencies?) and -more importantly- other non-linear behavior.

Decent driver-makers go through great pains to ensure low, unobjectionable "distortions" proven that the driver is used within a certain bandwidth and below a certain SPL.

After you (or the speaker manufacturer) has selected pretty multiple good quality drivers, the extra "distortions" that blur the sound are to be contributed by the amplifiers.

And it's there that I claim that the "distortions" that are going to matter more are higher-order HD, IMD, and other non-linear stuff. It is on "IMD" and the other "non-linear" stuff where the active setup may bring significant improvements.

I claim that IMD can be significantly reduced simply by narrowing down the operating bandwidth of the amplifier... makes sense, really: narrower frequency range, less multiplication products possible.

I also claim that a fully active speaker setup gives the side effect of requiring significantly less amplifier power, particularly in the critical high frequency range (some tweeters can have more than 100dB sensitivity), which opens up many important routes for improvement, that truly do make a difference to the sound.

When you read a book such as "High performance audio amplifiers" by Duncan, you realize how compromised is a typical (high quality) amplifier when it's asked to drive a 85-91dB sensitivity speaker with a typical passive crossover network. Mainly, the power required for driving the woofer, significantly higher than the power for the sqwawker and tweeter, causes all sorts of things on the amplifier, and those things do destroy the clarity of the high frequencies, which are (sadly) travelling through the same canal.

Most high quality, low distortion, high clarity, no-nonsense studio loudspeakers have a provision for bi-amping...

Last edited by flavio81; 7th November 2012 at 03:34 PM.
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Old 7th November 2012, 04:01 PM   #677
dewardh is offline dewardh  United States
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Quote:
Originally Posted by flavio81 View Post
When you read a book such as "High performance audio amplifiers" by Duncan, you realize how compromised is a typical (high quality) amplifier when it's asked to drive a 85-91dB sensitivity speaker with a typical passive crossover network. Mainly, the power required for driving the woofer, significantly higher than the power for the sqwawker and tweeter, causes all sorts of things on the amplifier, and those things do destroy the clarity of the high frequencies, which are (sadly) travelling through the same canal.
And conversely there are a number of very inexpensive (think LM3886 inexpensive) amplifiers which will drive almost any tweeter with NO audible amplifier distortion of any sort. And by removing the high frequency/high slew rate demand from the "other" amps in the system it becomes much easier to design them to be inexpensive, high power and effectively distortion free (within their working range) as well. Thus spoke Mr Natural . . . "Use the right tool for the job".
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Old 7th November 2012, 10:18 PM   #678
AJ34 is offline AJ34  United Kingdom
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Whilst these posts are interesting and have given me lots of food for thought, there's still no clear ‘winner’ as far as I can see – even after nearly 700 posts of mainly technical argument.

Perhaps the way to decide whether passive or active offers the best listening experience of recorded music reproduced in the domestic environment is to know what system type (i.e. passive or active) people on this forum choose to listen to with the important proviso that ’serious examples’ of both system types have been used in your home for long enough to be able to express a valid preference.

(A lame idea as this forum doesn’t appear to support polls!)
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Old 7th November 2012, 10:40 PM   #679
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Quote:
Originally Posted by flavio81 View Post
There is something wrong here. The amplifier (unless it's a very very good one), by virtues of typical Class-AB amplifier distortions such as crossover distortion, under/over biasing, thermal issues, power rail modulation, etc*... will produce all sorts of distortions including IMD distortion. And these are audible in the sense that they are removed or diminished by (a) going to a better amplifier like a class-A bjt amplifier, (b) going fully active so the amplifier working bandwidth is narrower, or (c) both.
Yes and this is the point, that if your amplifier isn't suitably designed that going active will reduce the detrimental effects that higher order distortion products could potentially introduce.
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Old 7th November 2012, 10:40 PM   #680
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...... there's still no clear ‘winner’ as far as I can see – even after nearly 700 posts of mainly technical argument.

Perhaps the way to decide whether passive or active offers the best listening experience......
700 shots, a draw.......and you don't see the obvious conclusion ? there is no winner, never will be, and none needed anyway
the best is whatever works for you

lets just say I decide that active would the best for you
but if you can't make it work, what good is for you then
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