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Old 27th December 2002, 07:14 PM   #1
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Default X/O - active/passive? fewer components?

Hello all,

I'm still assembling my cabinets and have got to the point where I must seriously think about the crossovers.

For background info:

Bass 2 x scanspeak 6515-01 10" per cab (sealed)120L Q.71
mid focal audiom 6wm (sealed) 10L Q.61
tweet scanspeak revelator 9500/9900

I have all the amps to power each unit seperately, and will be able to time align all units.

I originally planned on using a 3 way linkwitz-riley at 300Hz and 2000Hz, and already have the esp boards siiting here next to me (with the power supply board almost finished).

However

Lots more reading suggests that the fewer components the better, and I reckon I can utilise this theory for some of my units.

The mid naturally rolls of in the bass at 12Db/octave, and is 6Db down at around 120Hz - don't need to actively x-over this bit then? - just use a L-R lowpass on the bass units to be down 6Db at 120Hz..

Also a lot of people quote at just using a capacitor on the tweeter - could I do this passive line level before the tweeter amp? -

Then I just have to build 1 lowpass for the mid unit, and 1 low pass for the bass unit using the least possible components.

Am I talking sense , or just confusing myself even more?

Will post the response curves of the drivers below...

Cheers, and hope you've all had a great Christmas this year...

Rob
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Old 27th December 2002, 07:16 PM   #2
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tweeter response:
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Old 27th December 2002, 07:21 PM   #3
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mid response:
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Old 27th December 2002, 07:23 PM   #4
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mid's bass response:
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Old 27th December 2002, 07:32 PM   #5
Pan is offline Pan  Sweden
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Hi Rob,

my only/first thought/question :-) would be about the upper response of the focal.
It looks like it has some serious nasty behaviour starting @1k.
Using these drivers I would suggest that you consider 24dB LR at 1.5k. Mr Linkwitz uses SS 9700 with 4th order at 1440Hz I believe, so that would work fine with 9900.

If you use lower order x-ing at 2k Im pretty sure you will hear these nasty break-up resonances from the focal.

/Peter
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Old 27th December 2002, 07:49 PM   #6
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Hi Peter,

Your reply tends to point me back to the full active x-over that I originally planned. I was hoping that I'd get away with a 12Db on the mid/tweeter as I have read bad things about 4th order slopes.



Thanks for your input..

Rob
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Old 27th December 2002, 08:29 PM   #7
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What about a 3 order passive crossover easy to build!
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Old 27th December 2002, 08:40 PM   #8
Pan is offline Pan  Sweden
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Rob,

an alternative if you want low order slopes (which I have a tendency to prefer with the right driver) would be to chose another mid with a flatter better controled response.

First that comes to my mind is the Peerless HDS 6.5"
or Skaaning 6". The Peerless (below $100 in Sweden) is considered one of the absolute best 6.5"er no matter the price. The Skaaning is costly though, about $300 or so I think.

Yet another alternative (my favourite) is Accuton 7".

Or.... :-) you could try to find a ribbon/planar tweeter that could live happily with shallow slope at 1k-1.5k.

Its not easy to create the dreamsystem :-9

/Peter
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Old 27th December 2002, 08:46 PM   #9
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""What about a 3 order passive crossover easy to build!""

Hi,

I'm not too concerned about the difficulty of the build, but am kind of attatched to the LR x-over - its phase acurate at the x-over point, which is only possible with 2nd or 4th order.

I was trying to lose the x-over on the mid hi pass as it rolls off 2nd order anyway, and was hoping(praying ) that I might be able to lose the buffer stages on the tweeter and keep the signal path as short as possible..

Cheers

Rob
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Old 27th December 2002, 08:56 PM   #10
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Quote:
Originally posted by Pan
Rob,

Its not easy to create the dreamsystem :-9

/Peter

Tell me about it!

I basically commited to these drivers way back :

about to build this - whad`ya reckon?

And in that post I stated a 4th order LR. Its only after 3 months more of reading that I've been put off by the 4th order...

I've got all the drivers sitting here waiting so I'm loathe to change them now....If I did I'd go for the ATC mid..

Rob
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