Crossovers

So again, "it depends," right? At least now I have a little better understand of what's going on, which is really all that I wanted. I guess no one's going to come down definitively on one side or the order? It seems as if the complication of the crossover doesn't really translate into a speaker sounding "better or "worse," and what's really important is the execution.

Facts:

1. For the same SPL excursion quadruples for each octave you drop in frequency.

2. IM distortion is a function of excursion.

3. The cross-over type determines the axis along which peak output occurs.

4. Steeper cross-over slopes reduce the effects of changing driver response beyond the pass-bind.

5. Higher order cross-overs have more ringing in the impulse response.

Opinions:

From 1+2 you need at least a third order slope so that excursion is decreasing below the cross-over point resulting in low IM distortion.

Adding 3 you need a 4th order Linkwitz-Riley XO that has its peak on-axis because this leads to the most natural sound.

4 means that the higher-order cross-over is an enabling technology that allows using stiff materials (magnesium) that are very pistonic in their passband (for low distortion) but ring like bells at higher frequencies.

5 means that you don't want to go beyond LR4.

Phase coherence doesn't matter. Time alignment at the cross-over frequency does as a tool to aim the peak response at the listening axis.

Other people have different opinions and subjectively excellent sounding speakers have been produced with all sorts of technologies.

Of course, the most important thing is what you find pleasing. If it floats your boat buy it or build it.

If you want a definitive opinion from me as to crossovers, I will tell you that first order are my favorite. Like most things in life, simple things, using the best ingredients often produce the best result.

Further, series, as opposed to parralel networks, are also more to my liking. You didn't want us to get technical, and so I will try not to...

First order networks are the easiest to drive, and sound the most natural to me. They are phase, and presuming the speaker allows, time coherent. Of course, the tradeoff is that the slow rolloff means that a superior driver (the finest ingredients) become more critical, as does the crossover components themselves. Otherwise, you get hit in the face with components operating out of their areas of comfort, and some drivers sound worse than others when this happens.

I don't want to get into dogma here, as just as many people exist who can tout the benefits or second, third, and fourth order networks.

I also feel series networks(99.999+% speakers use parallel networks) sound better to me, as I don't get a sense that I am listening to individual drivers. They also present a resistive, as opposed to reactive load to the amplifier - ooh sorry, don't get technical (but let me sneak in that the rolloff can be tailored via Zeta - balanced by the ratio of the cap to the coil, making even sharp rolloffs with a first order network easy). Let's just say they are a more friendly load to an amp!

If I remember correctly there is a 90 degree phase shift (between woofer and tweeter) for each 6 dB filter section. So, 6 dB is 90 degrees, 12 dB is 180 degrees, 18 dB is 270 degrees, and 24 dB is 360 degrees. Note that the 24 dB filter restores inphase signals for woofer and tweeter. Note also that with a 12 dB filter the same result can be obtained by hooking one driver up with wires reversed. There is no way to make a 6dB filter electrically "right", but perhaps the 90 degree phase shift is tolerable, and the benefits of a simple crossover offset the disadvantages. Also, the driver has its own natural roll off, perhaps 6 dB with a 90 degree phase shift, so that the net acoustical slope is 12 dB, with a 180 degree phase shift. Consistent with this, with 6 dB crossovers, the tweeter is often hooked up backwards.

The 24 dB design is not practical for passive crossovers because too many components are required. However, it is easily accomplished in a line level electronic crossover, and most of the electronic crossovers sold today are made this way.