I looking at why some crossover slope combinations seem to work.
I will use the midbass/subwoofer crossovers as a example.
If for example i have>
sub @24 db slope and midbass @6db slope
sub @24 db slope and midbass @12db slope
sub @24 db slope and midbass @18 db slope


sub @18 db and midbass @6db slope
sub @18 db and midbass @12db slope
sub @18 db and midbass @18db slope



sub @12db slope and midbass @6db slope
sub @12db slope and midbass @12db slope
sub @12db slope and midbass @18db slope


Is combining different slopes causing some SQ problems??......cors

6db/oct slope adds 90 degrees phase shift
12db/oct slope adds 180 degrees phase shift
18db/oct slope adds 270 degrees phase shift
24db/oct slope adds 360 degrees phase shift

Actively it will make minimal difference,
I tend to stick with 12/24 and 6/18db combos,

the phase difference is only at the x/over point, for the distance of the slope over 3-6db when your running actively depending on the design of the electronic filter, usually with passive filters you can result at a complete 180, or 90/270 degree shift, the shift is wider but still not the entire range.

Juls

the only issue will come from low frequency transients, where you may need to time-align the woofer to the midbass, due to the combined phase 'lag' (not just a shift) between the two drivers.

at 12dB you need to reverse the phase on the sub (as you know) but reverse polarity is not the same as 180 degrees phase shift (due to time differences in phase, as compared to a general invertedness of the signal).

is invertedness even a word??
who cares...

at 6dB you generally don't need to worry about phase, as the shift is quite small and not usually audible.

18 and 24dB phase becomes an issue, as 360 degrees is in phase, but 1 cycle lagging, so TA the sub by 1 period less to bring it back. (i.e. 60Hz crossover, adjust the TA lower by 1/60th seconds - or 16.5ms

yep

fury u always leave a comment likened to a morsal of bread for the mice to look at and ask for more.........cors

Well each different slope has different phase shift, as long as you accomodate for this (via inverting phase/ta etc) then there's no issue...

Ofcourse the drivers arent all on the same plane/axis so it's not quiet as easy as that...



Keeps em coming back for more?

talking about more Fury - my pencil went blunt again.

I'm sure you're capable of sharpening your pencil

Hrm i think we might be getting a wee bit off topic.

16.5 ms? Are you crazy? Bass engine pro offers up to 5ms delay options, which is plenty for almost any install.

the only way to get 16.5ms, is if you have a alpine processor which offers up to 20ms..

thats a MASSIVE delay, if it was that bad a delay at 24db, then you would hear it drastically..
I can hear a 0.05ms delay difference in my system, 1ms is a black and white difference, 16.5ms is a total catastrophie.

Juls

The theory is correct Juls, I just nutted that through with one of the engineers here. As you said though, the difference would be in the slope, and that slope is very steep at 24db/oct, which may make it inaudible.

more info on phase something please? ........cors

Ah, yes, if you need that much delay, I'd say you have issues elsewhere that may need sorting first.

The funny thing is - when 99% of car audio units are set for 'phase 180deg.' they are actually polarity inverted - no phase shift.

darndest thing huh?

what led me to this was some testing I did on my Behringer unit versus the Alpine PXA-H701. The Behringer has both phase (0 to 180deg. variable) and polarity (normal/reverse) adjustment. The Alpine has only '0' or '180' degrees.

The Alpine (and I suspect many others) is a polarity adjustment, not phase adjustment as advertised.