Balanced active crossover advice

zigzagflux · 9th April 2007, 03:38 PM

I am in process of building my next amplifier, and was heading towards a Lynn Olson Amity/Karna type. I currently run a set of ME-2 Ariels with a ST-70 and powered subwoofer.

I do not get enough midbass (100-500Hz) out of the ME-2's, and have read a number of articles (some written by Lynn) about what to do about this. Alas, not a simple solution.

My first preference is a passive linestage 6 dB filter for the ME-2's, with a separate midbass/bass driver. Attached is a possible attempt for the amplifier input.

It seems to me frequency-wise the filter would work, but if the components are not perfectly matched, which they won't be, the benefits of balanced topology are lost.

Is this a waste of time, or is it possible to get good performance if I attempt to match components? Like buy 10-20 capacitors and pick the best matches.

Better solutions?

EC8010 · 9th April 2007, 04:47 PM

Why not move the 0.01uF capacitors to the primary, and combine them into one single series capacitor?

zigzagflux · 9th April 2007, 04:57 PM

Could certainly try that, but I have read a number of cautions about attempting to cap couple to transformers. Don't have any links to those cautions in front of me, but I do remember reading it.

Maybe it was at K&K, don't know. If it's really that simple why all the fuss about the difficulties in using active crossovers? Not talking 12/18/24 dB, of course.

http://www.clarisonus.com/blog/?p=17

EC8010 · 9th April 2007, 08:51 PM

Yes, there's a possibility of an LF resonance between the capacitors and the primary inductance of the transformer. The only way to be certain of how a transformer is going to behave is to set it up and measure it.

zigzagflux · 10th April 2007, 12:22 PM

So sweep the input from 1Hz to 40kHz, and check the output?

What if I find a resonant peak? Do I try damping with resistance, or return to the secondary balanced filter?

Is this considered the best approach for a passive HP filter?

EC8010 · 10th April 2007, 12:27 PM

Sweep it and see what you find. I've never done this before, so I really don't know what to expect. It may be feasible, it may not. Only experiment will prove it either way.

planet10 · 10th April 2007, 06:07 PM

Quote:

Originally posted by zigzagflux
I do not get enough midbass (100-500Hz) out of the ME-2's

With an 8" baffle width, that is likely baffle step loss... lots of ways to deal with that http://www.t-linespeakers.org/tech/b...intro-bds.html

Given my dislike for MTM... i'd look at building a bipole...

dave

9th April 2007, 04:47 PM	#2
EC8010 diyAudio Moderator Join Date: Jan 2003 Location: Near London. UK	Why not move the 0.01uF capacitors to the primary, and combine them into one single series capacitor? __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

9th April 2007, 08:51 PM	#4
EC8010 diyAudio Moderator Join Date: Jan 2003 Location: Near London. UK	Yes, there's a possibility of an LF resonance between the capacitors and the primary inductance of the transformer. The only way to be certain of how a transformer is going to behave is to set it up and measure it. __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

10th April 2007, 12:27 PM	#6
EC8010 diyAudio Moderator Join Date: Jan 2003 Location: Near London. UK	Sweep it and see what you find. I've never done this before, so I really don't know what to expect. It may be feasible, it may not. Only experiment will prove it either way. __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

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9th April 2007, 04:57 PM	#3
zigzagflux diyAudio Member Join Date: Oct 2006	Could certainly try that, but I have read a number of cautions about attempting to cap couple to transformers. Don't have any links to those cautions in front of me, but I do remember reading it. Maybe it was at K&K, don't know. If it's really that simple why all the fuss about the difficulties in using active crossovers? Not talking 12/18/24 dB, of course. http://www.clarisonus.com/blog/?p=17

10th April 2007, 12:22 PM	#5
zigzagflux diyAudio Member Join Date: Oct 2006	So sweep the input from 1Hz to 40kHz, and check the output? What if I find a resonant peak? Do I try damping with resistance, or return to the secondary balanced filter? Is this considered the best approach for a passive HP filter?

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