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First Order Crossovers: Pros and Cons

I wonder if some folks might share their expertise on the question of crossover design. I'm coming around to the view that this is perhaps the most significant element of speaker design yet I really know very little about it and don't really understand the basic principles. Several of the speakers I have heard in my quest for full range floorstanders are "first order" designs. I have really enjoyed their sound but do not know if this is attributable primarily to the crossover design or to a combination of other factors as well. In addition, I have heard that, for example, because of the use of this crossover configuration on the Vandersteen 5 one has to sit at least 10 feet away from the speakers in order for the drivers to properly mesh. Is this really true and if so why? Another brand also in contention is the Fried Studio 7 which also uses a first order design. Same issue? Could someone share in laymans terms the basic principles of crossover design and indicate the advantages and disadvantages of each. Also, what designers are making intelligent choices in trying to work around the problems associated with crossover design? Thanks for your input.
dodgealum
skrivis
30 posts
 
A 2nd-order x-over with the tweeter's leads reversed gives you an in-phase output if you're considering _absolute_ phase (polarity). The 4th-order x-over is similar.

However, you're still seeing a phase shift. If you look at the electrical input and output with something other than a simple sine wave, it becomes obvious that the output is different from the input.

The classic statement I keep repeating is "a 1st-order x-over sums to a piece of wire." This is not true of other standard x-overs.

It's possible to add a delay in an active x-over to put things closer to normal, and this is even easier when the x-over is digital.

Technologies like DEQX hold a lot of promise. It's like having your cake and eating it too. :)
eldartford
4,262 posts
 
Skrivis...If, as you say "a 1st-order x-over sums to a piece of wire" it must follow that a second order crossover, which amounts to two first order filters in series, is the sum of two pieces of wire.

But I agree that digital crossovers can do wonderful things.
greenmountainaudio5317
8 posts
 
Hi Eldartford.
Thank you for your comments. Just a quick note, however. A second-order filter is not two first-order crossovers in series, nor "cascaded". The parts in a second-order filter, the capacitors and inductors, are of different values than those used in a first-order circuit.

Best regards,
Roy Johnson
Founder and Designer
Green Mountain Audio
eldartford
4,262 posts
 
[email protected] the component values, for a particular frequency, differ from a first order filter because the cascaded filters are working from and into different impedances. But they are still two series filters. In the case of an electronic crossover, fourth order L/R for example, each of the four filter sections includes a buffer amp, so that each stage is similarly driven and loaded, and in this case the component values are the same.
biomimetic
252 posts
 
Ok, not to be over the top, but if speakers are time coherent and each cone, if I understand correctly, is 180 degrees out of phase from the other, wouldn't a perfect set-up only work with bi-wiring, where you can flip one of the sets of wires for the cone you want to put back into the same phase? Or am I wrong?
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