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CADENZA DN14 SP1019 CROSSOVER

 
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AC2/PEN
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PostPosted: Sat Aug 27, 2011 10:48 am    Post subject: CADENZA DN14 SP1019 CROSSOVER Reply with quote

My Cadenza crossovers have L1 & L2 (B200 section) in reversed positions to that shown in the schematic on this site. They have not been switched and are both held in by original nylon straps. I do not use these Xovers having made my own using modern parts. Is the diagram wrong or were these Xovers wrongly assembled?


L1 (I/P) is 0.6mH (should be 1mH) according to diagram.

L2 is 1mH (Should be 0.6mH)

Any one else notice this before?

Wondered why it sounded 'so' different!

Regards,

David
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ColinR
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PostPosted: Sat Aug 27, 2011 1:42 pm    Post subject: Reply with quote

The crossover topography is electrically correct so there will be no difference in sound between it and its mirror image.
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speakerguru
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PostPosted: Sun Aug 28, 2011 8:57 am    Post subject: Reply with quote

The larger value, 1mH, should definitely be the one at the input side. If you have not misread the pcb tracking and are sure the 1mH is at the woofer side, then they were wrongly assembled Shocked .

Last edited by speakerguru on Sun Aug 28, 2011 10:14 am; edited 1 time in total
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AC2/PEN
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PostPosted: Sun Aug 28, 2011 9:10 am    Post subject: Reply with quote

Yes, thats what I thought - they were definitly assembled wrongly then. L1 measures 0.6mH, not 1mH. Unless of course the diagram is wrong? However, running a CAAD filter design program for the B200/T27 18db Butterworth, makes the input choke (i.e L1) larger than the second inductor. I would also mention that looking at the 'photos of the DN14 (on site) shows the inductor colour markings (red & black) to be in the same positions as on my(incorrect) pair (?)

Thanks for the replies,

regards,

David.
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speakerguru
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PostPosted: Sun Aug 28, 2011 10:29 am    Post subject: Reply with quote

As a general rule of thumb, re three element "T" section low pass and high pass filters, if you make the input element lower impedance than the output element, then the filter "peaks" before cut off and you get a corresponding impedance dip at that point. That's why you probably won't ever see a tweeter network with the output capacitor smaller than the input.

I must say, the location of the zobel network in the schematic is unusual. Normally the it would go across the drive unit, otherwise the second inductor just forms an inductive attenuator in conjunction with the drive unit voice coil inductance. However, Mike Gough was an inventive chap and may have had his reasons to do it that way. (or there has been a mistake in the tracing out?)
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AC2/PEN
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PostPosted: Sun Aug 28, 2011 3:10 pm    Post subject: Reply with quote

Just looked at the pcb and can confirm the diagram is correct regarding the Zobel network.
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speakerguru
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PostPosted: Sun Aug 28, 2011 6:11 pm    Post subject: Reply with quote

OK, well the T27 is a bit insensitive for a B200 with a big magnet, so maybe the inductive attenuator was the way to go.

If that was the case, then it may be that the larger inductor was used in the attenuator and the whole thing preceeded by a second order low pass filter using the smaller inductor. Confusing aren't they, these passive filters into reactive loads?!?
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AC2/PEN
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PostPosted: Mon Aug 29, 2011 8:45 am    Post subject: Reply with quote

Makes sense though - but, still confusing! In that case surely the diagram is incorrect?

regards,

David.
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ColinR
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PostPosted: Mon Aug 29, 2011 10:34 am    Post subject: Reply with quote

Quote:
surely the diagram is incorrect?


It's a L/R mirror image.

So make a copy of the existing diagrams' bass section components and put the B200 SP1022 on the left hand side and the input on the right Smile .
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