6 db / octave for each "order"

4th order is 24 db / octave

Example: a bass blocker, the cap you put in line with your little speakers, is a first order crossover, only 6 db / octave.

 

Passive crossover networks are only easier to design if you have the design in your head already. Otherwise, they are more complicated to tune because you have to go by trial and error for each cars. Not all cars will respond with the same xover network. This is where active shines. You can adjust accordingly to your ears to hear what sounds better to you.

But a well design passive crossover is no slouch against an active setup

 

Well having listened to Orthonormal's setup tonight I can't even describe what a difference the individual time alignment of each driver makes. Way better than even simple L vs. R side time correction. I dunno, we could both sit here typing away on the internet about how great it was with just an Alpine 9833 running the internal amp, 4 way time correction, stock MY04 speakers and no sub. And how I turned the time correction off and it sounded like crap. But nobody will believe us- and I do mean nobody.

Time to wire my doors...

Peter

 

A couple notes just for fun. Opinions and food for thought, no flames intended.

Higher-order cross-overs have steeper slopes, but you're assuming that's a preference. Why? Higher-orders add more phase-shift problems and you don't get that corrected with tuning. Phase shifts are an integral part of adding capacitors and inductors to the circuit, whether they're in the pre-amp or power amp path doesn't change that. BTW - time-alignment usually adds more phase shifts.

Yes, adding those caps and coils in the low-power (pre-amp) stage means the amps are more efficient (no power lost in the passive cross-over) but the lost power is negligable, typically less than 1dB. I bet none of you can hear 1dB in a blind A-B test.

Passive cross-overs that come with high-end speaker combos are tuned to the speakers, but not the car. With active cross-overs you can tune to both but in most cases the car's design doesn't affect the cross-over point. Cross-over points should be chosen to match the drivers frequency response and dispersion characteristics, and veering away from those optimums is not really a "personal perference" unless you like lumpy frequency response or extra distorion in a particular frequency range. Of course it's possible the lumps you add might cancel out nulls in the car, but that's going to be pretty hard to work out and won't be done in average Joe's garage.

I don't doubt that time-aligned systems sound different, I just don't understand them. If you're correcting for the distance difference between the drivers and the listener, then once you get it aligned, moving your head 2 inches mucks it up again. And if you move to the passenger side it must sound like real crap because it's double-out-of-alignment. If that's not the case, then I'm not sure what the time alignment is doing, but it can't be time alignement.

I had a bi-amped car stereo in 1976. Wow. It was cool.

All this said I'm not at all opposed to active systems or time-alignment if you like it or feel like tinkering with it. To me, the biggest benefit of bi-amping (or active cross-overs or direct-drive, whatever) is the effect on bass response because it gets the cross-over out of the woofer path and the amp can properly damp the driver. But in nearly all car systems the woofer (sub) is direct-drive already and I'm not sure there's as much benefit on a mid-driver.

 

That's only looking at it one direction, the output of the amplifier. The difference on the amount of input power to the amplifier could be significant depending on where the crossover was made and what class of amplifier you are using.

 

From what I heard on Orthonormal's system, moving your head 2 inches one way or the other doesn't completely screw it up. The issue is that in the driver's position, the path length difference for the driver's tweeter and driver's mid-woofer are quite different, and also different from the right side.

I agree it screws things up from the passenger seat. One nice thing about the Alpine units with 6 way time alignment is that they have 6 presets, so you can save different settings and quickly switch depending on who is in the car.

I'm saying all this as someone who has played around with the time alignment on my Alpine in 2-ch mode (where you can only align the L vs. R and the sub) and never really found it to make things much better (only different). But listening to John's setup with each tweeter and mid-woofer set individually, that was a big improvement. I dunno it might not work for everyone with every system, but I was quite impressed by the difference it made in this case.

Peter

 

Huh?

You're saying the input power to the amp will change if the cross-over point changes? I agree, as long as you only consider the amp where the cross-over change lowers the power requirement. For every watt you "pull away" from the tweeter amp by raising the cross-over point, you have to add that watt to the mid to get the frequency coverage. More or less it's a wash as far as the total system is concerned.

If you're saying you can use a smaller amp on each driver, yes that is correct. But you're buyng 2 amps instead of one and the total power output has to remain the same to achieve the same dB level. I don't see a a 20W amp and a 80W amp being more eficient than a 100W amp. I'll bet it's less efficient as a total system because now you have two sets of "overhead" power losses instead of one. In general, higher-power amps are more efficient than low power ones because the overhead is a smaller percentage of the total power.

 

[QUOTE=PoweredByCamry,Oct 28 2005, 03:32 PM]From what I heard on Orthonormal's system, moving your head 2 inches one way or the other doesn't completely screw it up.

 

I agree it would be a good experiment. I have to say that in John's car, the sound from the driver's seat with his alignment settings was pretty close to what I got if I turned the time correction off and put my chin on the shift knob. With the drivers in the factory positions in the S2000 your results will also vary with the type of drivers you use. The driver tweeter, if aimed perpendicular to the door panel, is severely off-axis while the passenger tweeter is less so. Perhaps the stock MY04+ tweeters that John is currently using are not so sensitive to being off axis.

Peter

 

[QUOTE=modifry,Oct 28 2005, 06:12 PM] Huh?

You're saying the input power to the amp will change if the cross-over point changes?