Ok.. So I'm not incredibly knowledgable about this, but I thought I could set crossovers.. I'm not talking about getting them perfect, but here's my dilemma:

Since I have a saperate amp for my speakers, it's obviously set to hi-pass.. It has to different amp settings, Amp 1 and Amp 2, so that, for example, front speakers could take highs, and back mids, or whatever.. You get the idea though.. In my setup, my front are my components, rear are the 6x9's... Both amps (In the same physical amp, mind you) are set to hi pass...

I have been checking and testing this, because it hasnt been sounding quite rights.. My crossovers are set from the installer, hi pass, and like 80 or whatever HZ. Regardless, when playing a 50hz tone, my comps, and even the rears a little, are straining themselves almost to their peak to reproduce it.. Mind you, it's not loud at all, but geez, they shouldn't do this! Why are they?!

I need help...

 

Anyone? I know it's not working right.. I mean, it can't be, right? Why would I want bass through my components like that, when that's what the sub is for?

 

A crossover isn't something that just blocks 100% of the signal below a certain frequency. It's a filter with a gradual slope. What this means is that if you have your filter set at 80hz, it doesn't mean that everything from 79hz and down disappears. It just means that it begins to roll off at a certain rate. Most cheap amps use a 12dB/octave filter. This means that for every octave you go below the set frequency, the signal is attenuated 12dB.

One octave below 80hz is 40hz, so with a normal filter, the 40hz signal is going to be reproduced at a level 12dB lower than an 80hz signal. The 50hz tone that you're pushing through is probably attenuated around 9dB, which is probably still loud enough to cause problems with the speakers.

The answer? Move your crossover frequency up higher, use a crossover with a steeper slope, or if your head unit has a built in crossover, use that in conjunction with the one on the amp. If they both have a 12dB/octave slope, your result will be a 24dB/octave filter.

 

1 more thing -- if u change your crossover slope, don't forget to take the phase difference into account. A slope of 12dB/octave creates a 180* shift in phase. So if your subs are crossed at 12dB/octave and your mids are at 12dB/octave, everything will be in phase. But if u set your mids to 24dB/octave, they will now be 180* out of phase w/ the subs. That means the bass from your mids will cancel out some of the bass from your subs -- resulting in weaker, sloppier bass. Like Jim said, the crossover pt isn't a 100% cutoff, so even though the mids are crossed over above the subs freqs, they still will produce some bass.

A lot of newer HUs have phase controls built in, so u might be able to switch the phase from there. If not, simply reverse the speaker wires going to the subs so that the + wire goes to the - terminal and vice versa.

 

if its an electronic (active) xover then this doesn not apply. This is one of the benifits to going all active. Active also doesn't suffer from ohm load problems at different frequencies that passive (caps and inductors) do

 

I get the same problems with my 3inch alpines in my dash on certain Lil John/Ol Dirty Bastard songs. Bass is getting to the front speaker and it sounds bad...

I noticed it MORE when I turned the fader more towards the front channel VS rear..Is there a reason for this.

Note: the 3inchs are running off the deck and so are the 6-9s. Obviously I have a amp for the subs though.

Ive got settings on my head unit to set my treble and bass. something like 100 200 80 60 or something for bass. And like 12.5 10.0 and something else...

suggestions?

 

Once I get a 4 channel amp Im going to buy a cheap EQ to try and fix this problem....But on certain songs the +6 to the fron channel VS rear sounds worlds better but on other songs its the complete opposite.

 

All right, that pretty much answers it... Hmm, I guess I'll buy an inline filter, that ought to help a bit..


Thanks alot all.. I was under the impression that it did indeed cut off all below x freq., so that was my problem...
Its worrisome to see 6.5 inch speakers pushing that hard...

 

The phase issues do apply to active crossovers... w/ an active crossover works basically the same way as a passive crossover -- it just does it w/ a weaker, non-amplified signal. But whether the phase is changed before or after it's amplified, the phase change must still be taken into account. The only way to crossover a signal w/o altering the phase is to do it digitally, but such things are very rare in the car audio world