XO experts: what the heck is this??

Dave Milne

Supporting Actor
Joined
Jul 2, 2001
Messages
568
I'm looking at a schematic for a crossover designed by Dynaudio (shown below, hopefully) and there are a bunch of parts on the right side just hanging off the input. If the amp source impedance is really zero (or darn close)... what could these parts possibly do?

http://www.azstarnet.com/~dmilne/rev...eral005002.jpg

Text from Dynaudio states:
"The circuit following the tweeter area is no conventional circuit but it improves the electrical impedance of the loudspeaker and the electrical phase response of the filter until nearly ideal values are achieved. These additional filters produce an extraordinarily flat impedance response which reliably prevents reflections caused by cables up to a frequency of 500 KHz."

I built these and tried them with and without the "extra" network and didn't hear a significant difference. Is this snake oil?

Dave
 

Brian-K-Owens

Stunt Coordinator
Joined
Feb 6, 2003
Messages
194
Additional branches like that could be used for many things, like:

Resonant frequency traps for the tweeters Fs.
Getting rid of peaks in the tweeter's frequency response.
Controlling rising frequency response of a tweeter.
Changing phase response of the tweeter.

Brian
 

Dan Wesnor

Second Unit
Joined
Apr 28, 1999
Messages
389
Impedance compensation circuits (like that one) are intended for use with amplifiers that have problems with reactive loads - i.e., tube amps. If you are using a quality solid state amp, I doubt you would hear much difference. Usually, most designers will mark impedance compensation circuits as "optional".
 

Brian-K-Owens

Stunt Coordinator
Joined
Feb 6, 2003
Messages
194
Good call Dan. My bad, as I should have looked closer at the diagram. I just glanced at it and after reading "circuit following the tweeter area" and "up to a frequency of 500 KHz.", I thought all of the additional network was in parallel with just the tweeter. I now see it is in parallel with the entire network.

I agree with Dan's post. . .

Brian
 

Dave Milne

Supporting Actor
Joined
Jul 2, 2001
Messages
568
Brian,
It didn't sink in with me at first either, until I started building them and noticed that this network is straight across the amp terminals. What could possibly be the effect? But Dan's post makes sense. In my case, I've got a solid-state amp (Bryston 4BST) with only about 18" of 12ga wire to the crossovers. Yes, that's inches. I put the crossovers in separate boxes in my equipment closet so I could "tweak". Three separate 12ga runs connect the crossovers to each speaker. So I probably wasted my money on the Solen coils and caps (ouch) for these networks.

I guess the Dynaudio engineers were in one of those "cost is not object" moods. Oh well, maybe I can use the parts in the next projext...
 

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