1st,2nd,3rd order crossovers,etc

What are the differences and pros/cons between the various crossovers?
Thanks Bob
1st order = 6 db per octive electronic slope
2nd order = 12 db per octive electronic slope
3rd oder = 18 db per octive electonic slope
and so on. The steeper the slope the less bleed through you get from the frequencies you want to filter out. As for pros and cons....I will leave that to someone more knowledgable.


A first order crossover uses a single filter (inductor and capacitor) to separate frequencies into low and high frequencies and then direct them to the woofer and tweeter.

A second order crossover uses a double filter. A third order crossover uses a triple filter, etc. The higher up you go, complexity increases.

Also, the higher the order, the more sharply that the frequency rolls off in this process of frequency filtration. A first order crossover rolls off at 6dB per octave, a second order at 12 dB, a third order at 18dB.

There are numerous advantages and disavantages to each. The cross-over is not chosen in isolation. In choosing a cross-over, the designer has to have regard to driver and cabinet characteristics. In other words, it's a package. The designer makes trade-offs. Disadvantages in a cross-over can be compensated for in cabinet design and driver choice, and vice-versa. For example, a first order cross-over, because of gradual frequency roll-off, will have a larger band of frequencies shared by both the woofer and tweeter. This can produce phase errors where the same frequency comes out of both drivers at different points in time. So, for example, the designer might compensate by placing the front plane of the tweeter slightly behind the plane of the woofer so that when the same frequency comes out of both drivers, one travels a longer distance to reach you This compensates for the phase error otherwise produced by the cross-over. Another designer might prefer to tackle phase error by using a higher order crossover, where there is less overlap of frequencies because of sharper frequency roll-off. But he would then have to deal with other problems unique to the higher order cross-over. I don't have sufficient technical knowledge to describe all of the advantages and disadvantages of each. The bottom line is that there is no one type which is best. Cross-over choice has to have regard to the drivers and cabinet characteristics so that they complement each other.
As much as i post and as fast as i can type, even i'm not up to writing the novel that such an answer would turn out to be.

I would suggest reading these two books. You should read the Weems book first as it will give you the basic background that you need to better understand the much more complex and technical rantings in Dickason's book. Both are very good books and most audiophiles would be dollars ahead if they read and at least tried to understand them.

David B. Weems / How to design, build & test complete speaker systems

Vance Dickason / The Loudspeaker Design Cookbook

Hope this helps and at least points you in the proper direction. Sean
Please do a search on phase and time coherence in loudspeakers on this forum. Many threads on it which address just such questions.
I'll bet many here are in the dark about such matters. I ain't got the brain to understand; so in my case the prof is in the pudding--listening.---YET, not knowing ahead of time how they work;what to look for and such.My only criteria is the pudding.
If you're asking out of a need for education, then this is not the forum - your question is way too encompassing and requires a book for an answer as Sean states above.

However, if you're asking with an eye towards purchasing speakers and you're worried their crossover design might not be "the best", then consider that there is no crossover design that can be called across-the-board superior. The selection of crossover by a speaker designer depends on a lot of factors. Some designers, such as Thiel, feel that a first order is superior for the sound they're looking towards and will build around that. Others will find a 4th order Linkwitz is the way to go for a particular driver/enclosure combo. Whatever they decide will be based on what they are looking to accomplish withing a certain price point. Suffice to say that whatever speaker you are looking at has been designed to the best of the mfr's ability to meet the goal of the speaker. Whether they've succeded is a different story. Listen critically, and don't worry about what makes it spin.
The 4th order Linkwitz is particularly well suited to line level electronic crossovers (but overly complex and costly for a passive crossover). Apart from that, every variation of crossover has its advocates, and detractors. Some say that a 0th order is best (none), but that puts a big burden on the driver.