Totally dependant on the components you're using and how they are installed. Generalizing:
6db/oct: Best phase and amplitude response (Butterworth). Worst off axis performance and modulation distortion. 90 degree phase shift. Stresses drivers such as tweeters and delicate midranges, as 6db/oct isn't enough to limit excursion in many cases. Very sensitive to driver alignment, both in relation to each other and also the axis of the drivers themselves. Best results usually come with installs where the tweeter is very close to the mid, and careful attention to positioning is taken (kick panels, angled door).
12db/oct: 2nd best phase and amplitude response. Less sensitive to driver misalignment than 1st order crossovers. May still be too shallow for certain drivers. A natural crossover for a car, gives a good response. Good for installs that are slightly off axis, and drivers that are decently close to one another, more forgiving than a 1st order crossover in that respect.
18db/oct: Good amplitude and phase response. The steeper slope can minimize modulation distortion and it improves off axis performance. Less sensitive to driver misalignment. Good for off axis installs like a stock door panel, and the tweeter being further from the mid.
24db/oct: Can produce a very flat amplitude and phase response. Steep slope equals least modulation distortion. 360 degree phase shift, so the drivers are "in phase", but the time alignment is off. Least sensitive to driver misalignment. These are typically used in off axis installs and give good results if you want to locate the tweeter far from the mid.
Phase alignment or time alignment does essentially the same task. You're simply trying to align the drivers acoustically to provide a coherent output to your ears. Best done with experimentation, as even with equations the end result can and will be affected by the environment, especially talking about a car with multiple reflections to distract the originating signal.
Replies (4)
ttocs on 12/20/2006 15:36:04
hey mo, wanna introduce yerself?
swez on 12/20/2006 22:53:10
Yes, please do MO... say more about your background.
Also, just so you understand the way CK does things, we appreciate technical expose's such as these and often add them to out DIY articles when submitted.
The only stipulations are accuracy of details and that the information is in our own words. If we quote an extended resource, note the source. However, Walt is pretty strict about copy & paste here. We can do C/P's on info contained in this site to save time, but not a wholesale practice OK?
Swez
cplkittle on 12/20/2006 23:33:23
Great information.
One question on the 6db/oct paragraph....
6db/oct: Best phase and amplitude response (Butterworth). Worst off axis performance and modulation distortion. 90 degree phase shift. Stresses drivers such as tweeters and delicate midranges, as 6db/oct isn't enough to limit excursion in many cases. Very sensitive to driver alignment, both in relation to each other and also the axis of the drivers themselves. Best results usually come with installs where the tweeter is very close to the mid, and careful attention to positioning is taken (kick panels, angled door).
How does this constitute or relate to the butterworth alignment?
and where does the 90 degree phase shift come into play?
This sounds like a 1/4 wave TL enclosure instead of a filter slope.
swez on 12/21/2006 08:55:41
Hint: Capacitors give a leading 90 degree phase shift in AC signals.
Inductors provive a lagging 90 degree phase shift in AC signals.
When we use them in pairs, they null each other out and we get roughly Zero phase shift and a -12dB filtering slope. This is why the 2nd order filter network is most popular alignment.
Swez
6db/oct: Best phase and amplitude response (Butterworth). Worst off axis performance and modulation distortion. 90 degree phase shift. Stresses drivers such as tweeters and delicate midranges, as 6db/oct isn't enough to limit excursion in many cases. Very sensitive to driver alignment, both in relation to each other and also the axis of the drivers themselves. Best results usually come with installs where the tweeter is very close to the mid, and careful attention to positioning is taken (kick panels, angled door).
12db/oct: 2nd best phase and amplitude response. Less sensitive to driver misalignment than 1st order crossovers. May still be too shallow for certain drivers. A natural crossover for a car, gives a good response. Good for installs that are slightly off axis, and drivers that are decently close to one another, more forgiving than a 1st order crossover in that respect.
18db/oct: Good amplitude and phase response. The steeper slope can minimize modulation distortion and it improves off axis performance. Less sensitive to driver misalignment. Good for off axis installs like a stock door panel, and the tweeter being further from the mid.
24db/oct: Can produce a very flat amplitude and phase response. Steep slope equals least modulation distortion. 360 degree phase shift, so the drivers are "in phase", but the time alignment is off. Least sensitive to driver misalignment. These are typically used in off axis installs and give good results if you want to locate the tweeter far from the mid.
Phase alignment or time alignment does essentially the same task. You're simply trying to align the drivers acoustically to provide a coherent output to your ears. Best done with experimentation, as even with equations the end result can and will be affected by the environment, especially talking about a car with multiple reflections to distract the originating signal.
Replies (4)
ttocs on 12/20/2006 15:36:04
hey mo, wanna introduce yerself?
swez on 12/20/2006 22:53:10
Yes, please do MO... say more about your background.
Also, just so you understand the way CK does things, we appreciate technical expose's such as these and often add them to out DIY articles when submitted.
The only stipulations are accuracy of details and that the information is in our own words. If we quote an extended resource, note the source. However, Walt is pretty strict about copy & paste here. We can do C/P's on info contained in this site to save time, but not a wholesale practice OK?
Swez
cplkittle on 12/20/2006 23:33:23
Great information.
One question on the 6db/oct paragraph....
6db/oct: Best phase and amplitude response (Butterworth). Worst off axis performance and modulation distortion. 90 degree phase shift. Stresses drivers such as tweeters and delicate midranges, as 6db/oct isn't enough to limit excursion in many cases. Very sensitive to driver alignment, both in relation to each other and also the axis of the drivers themselves. Best results usually come with installs where the tweeter is very close to the mid, and careful attention to positioning is taken (kick panels, angled door).
How does this constitute or relate to the butterworth alignment?
and where does the 90 degree phase shift come into play?
This sounds like a 1/4 wave TL enclosure instead of a filter slope.
swez on 12/21/2006 08:55:41
Hint: Capacitors give a leading 90 degree phase shift in AC signals.
Inductors provive a lagging 90 degree phase shift in AC signals.
When we use them in pairs, they null each other out and we get roughly Zero phase shift and a -12dB filtering slope. This is why the 2nd order filter network is most popular alignment.
Swez
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