using series and parallel Xovers in the same design, is it ok?

Puggie

Member
2004-10-11 5:21 pm
I'm trying to do a 4 way design completely passively (its actually in a car but I feel my question fits in this section better) and part of the critera for the system is to be completely passive off a single stereo amp. My drivers are as follows:

12" sub (dual 2 ohm) up to 125Hz
6.25" midbass (4Ohm each) 125Hz to about 1.6kHz
Horn and Compression driver (8Ohm each) 1.6kHz to about 5kHz
28mm tweet (8ohm) 5kHz up.

I want the sub wired to show 4 ohms and bebridged accross both channels of the amp (so parallel Xover, 125Hz Lowpass probably 12dB/oct). I want the Horn and Tweet to be crossed over very gently most of the sound is from the horn, which is positioned under the dash, the tweet is just to lift the image, this will be up high and have a slightly shorted path length than the horn, I was thinking first order series for these two, maybe even just using a coil and no cap.

Now the midbass to horn, is where I'm puzzled. I would like 12 or 24 dB/oct between the midbass and horn, I would like about 12dB high pass on the midbass at 125Hz to reduce the LF excursion to prevent the cone breaking up.

Can I do a 12dB/oct bandpass filterfor the midbass and then do a 12dB high pass for the horn, BUT still have the series filter for the horn/tweet? so effectively I would be treating the horn-tweet-series crossover as a tweeter and put a high pass 12dB filter infront of that?

am I rambling or making sense?

also can you build passive bandpass filters with different slopes for the high and low pass components? so I could use a 12dB between sub and midbass and 24dB between midbass and horn, or even horn and tweet series unit?

Am I making sense?
 
There is nothing particularly unusual with what you propose and it should work fine when/if you get the network values right. This is going to be your biggest problem.

But, connecting the woofer to the two + outputs will only reproduce the difference between the channels where you want the sum. The way around this is to use a phase inverter at the input of one of the amp channels. This will, of course, put one channel out of phase with the other for the rest of the speakers. Solve this by reversing phase when hooking them up.
 

Puggie

Member
2004-10-11 5:21 pm
as for the bridging most (99%) of Car audio amps are designed so if you connect accross the -Ve of one speaker output and the +ve of the other it bridges it, no need for inverting one input tom-foolery :) I could also use two seperate subs on on each channel, which may be an option with them mounted infinite baffle between the rear shelf and trunk (see I said trunk and not boot ;) )

How do a I make a bandpass with different HP and LP slopes, literally just design the individual filters and cascade them?
 
Puggie said:
as for the bridging most (99%) of Car audio amps are designed so if you connect accross the -Ve of one speaker output and the +ve of the other it bridges it, no need for inverting one input tom-foolery :) I could also use two seperate subs on on each channel, which may be an option with them mounted infinite baffle between the rear shelf and trunk (see I said trunk and not boot ;) )

How do a I make a bandpass with different HP and LP slopes, literally just design the individual filters and cascade them?

If you say so. I haven't paid much attention to car amps.

Yes, cascade HP and LP for a BP.