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Old 18th October 2012, 09:35 PM   #141
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Originally Posted by cotdt View Post
-9 db!? I'm not sure what's going on there, but I usually get -1dB or less on the woofer in my crossovers. Maybe he is including baffle step compensation into the losses?
No idea, you'd have to ask Billy Woodman.
But I would think that a complex passive xover might include bsc and/or zobels.
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Old 18th October 2012, 09:47 PM   #142
cotdt is offline cotdt  United States
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CopperTop, I've never heard anyone say that active is only for newbies. Maybe back in the day, the only options on the market were analog active crossovers, which had no baffle step compensation option and used terrible sounding op-amps. Even today, the options on the market for digital crossovers aren't great (I've compared, and this is my personal conclusion), though far better than in the past. The DIY options for great digital crossovers is already here today, just expensive.
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Old 18th October 2012, 10:00 PM   #143
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But there is a meme going about that while active are OK for beginners and philistines, an active is no match for a well-designed passive crossover.
This is nonsense.

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The argument may be along the lines that passive crossover design is "hard" and the designer has to serve such a long apprenticeship that he inevitably does it better than the idiot with the computer.
Neither passive nor active are any harder to a seasoned designer, this might be missing the point a little, but a skilled designer, who is going to be able to create a work of art with a passive xover, is going to be able to do the same with the active version. Mr Idiot with his computer and active xovers will never reach the same level of perfection as the designer who knows exactly what he's doing and how to go about doing it.

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But... we also hear the claim that passive crossover design is all about science and
measurements and objectivity.
Indeed.

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Well a computer can calculate in a second what even a member of The Crossover Designer's Guild would take a lifetime to do. There is no magic we're told, so the calculations and formulae are already defined. So let's stick them in a computer and come up with the truly optimum passive crossover and marvel at its beauty.
The trouble is that computers are horrible at noticing patterns, face recognition for example is something that computers struggle at immensely. A skilled designer is often capable of looking at the data provided and know within a minute or two, whether or not two drivers will work well together and then know pretty much what type of xover is going to be necessary to get the job done. The computer helps him fine tune the design saving an immense amount of time, but it doesn't pick the filters.

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But passive electronics is all about conflicting requirements and compromises (an 8th order passive is practically impossible, we're told, for example), so the digital active has simply got to be better in strictly objective terms.
If an 8th order active is required then yes things do start to add up. But the first part about conflicting requirements in passive xovers, this is absolutely true, because you do have losses in passive xovers and the simpler they can be made, whilst still doing an adequate job, the better. Often its this balancing act of getting the most bang for your buck of where the human shines over the computer. The human has the ability to again recognise where doing something for simplicities sake isn't going to cut it this time, but why another time it will.

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Personally I'm not interested in the slightest in any non-DIY considerations like hardware cost and size, so I don't think they have any place in this discussion; I want to build the best possible system and I haven't yet heard a real, non-magical, argument in favour of passive crossovers.
You wont get one.


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At very high level, active analog is not there yet.
This is nonsense.

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That might be me. Again, very reasonable, except the passive crossover designers want us to believe that it's so incredibly difficult, what with their having to juggle hundreds of variables written down on vellum (or whatever sounds best...), that the process of condensing all this down into three components takes hundreds of hours.
I think this is exaggerating things a little bit, but being able to reduce a crossovers component count whilst allowing it to keep doing pretty much the same job as it was doing 3 components more ago IS something that design experience gets you.
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Last edited by 5th element; 18th October 2012 at 10:04 PM.
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Old 18th October 2012, 10:15 PM   #144
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Cool. The audio hobby is crazy. Just mention your speakers, amplifiers, source code etc, and we will see.
Well the speakers are Mission M702e (being taken to to the council dump but I said I'd have them). I fixed the rattle, but they didn't sound great; woolly and muddled I thought, with unnaturally 'warm' bass. And yet... sometimes more pleasant to listen to than my Tannoys with certain types of music.

So I wanted to try active speakers, and these seemed ideal as a basis for experiment. I bypassed the passive crossovers and inserted a 100uF non-polarised electrolytic in series with the tweeters for protection (about 1 each). I bought two secondhand amps: Denon PMA355UK (about 30 each), an old Dell desktop PC which is almost silent (40) and a Creative X-Fi card (30). I then spent many, many happy hours writing the software to allow me to play any source in the PC through my own DSP code and thence to the analogue outputs of the card (cost 0). The crossover filters are strictly linear phase and complementary so if you add their outputs together the result is the original signal. If I want, I can obviously apply any sort of further processing to each driver and, if things had not worked quite so well, that's what I would have done. However, when I set the woofer and tweeter levels to be the same at the crossover point using a test tone, and ran the actual system for the first time with real music it was a eureka moment; I'd never knowingly listened to active speakers before, and in an instant I understood what the fuss was all about. Since then I've refined the crossover shapes and slopes, and added a fairly usable graphic interface, but very little else.

Now I don't yet know how lucky I've been in picking the perfect speaker for this conversion (in every sense!) enabling me to get away without applying any further correction, but my three-way Tannoys are about to get the same treatment...
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Old 18th October 2012, 10:20 PM   #145
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I haven't yet heard a real, non-magical, argument in favour of passive crossovers.
I don't know what you've heard, but you should have read it in this thread several times.

See posts 100 and 108. They sum it up well.

I have another "non-magical" reason. I don't like the hassle of active. I like to swap amps and listen to them full range. I can't listen to an amp project full range on an active system - unless I have 3 identical.

My "magical" reason? Passive sounds just as good, if not better than active. Different, yes. But not worse.

Want more magic? Think harmonics.
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Old 18th October 2012, 10:24 PM   #146
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So let's stick them in a computer and come up with the truly optimum passive crossover and marvel at its beauty.

But passive electronics is all about conflicting requirements and compromises (an 8th order passive is practically impossible, we're told, for example), so the digital active has simply got to be better in strictly objective terms.
I would stick to active
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Old 18th October 2012, 10:24 PM   #147
Jay is offline Jay  Indonesia
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This is nonsense.
At high level you can choose your best amplifier, best preamp, best speaker, best digital source. Those who work in audio shop selling high end stuffs will be familiar with the sound of certain high end system combinations. And one of these will be the ultimate passive system.

Now lets see the ultimate active analog crossover system... Let's list them.

As simple as that...
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Old 18th October 2012, 10:30 PM   #148
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And one of these will be the ultimate passive system.
only one ? not very good ods, considering you have all the finest gear in the world to choose from
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Old 18th October 2012, 10:34 PM   #149
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The crossover filters are strictly linear phase and complementary so if you add their outputs together the result is the original signal.
This in and of itself is useless for crossover design, it's nice in theory, but this only works if the drivers frequency responses are perfectly flat and extremely extended. 99.9% of drivers are not, so you will not be getting a flat response out of the loudspeakers, unless you've EQd them flat to start with.
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Old 18th October 2012, 10:35 PM   #150
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CopperTop, I've never heard anyone say that active is only for newbies.
Hi cotdt

Check out posts #39, #99 and #137.

Last edited by CopperTop; 18th October 2012 at 10:39 PM.
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