high and low pass x-overs

[87AccordsterLx]

ok I have been battleing this for a while now and I just want to make sure that I have this correct.... the high pass filters the low frequencies and the low filters the highs right...??? like if i set the lowpass at 160hz and the high at 80hz it would give you a frequency interval of 80-160hz...???? That doenst sound right??? anyone on this??? I want to filter the highs to stop at a certain frequency and let the lows go as low as they can.. so which one would I leave at "Flat" and which one at 160hz or whatever....

[merlindavis]

is this for a sub? i'm guessing since you have both features built in it's on your ht system... if you want the sub to hit from the bottom of it's range to, say, 120Hz (good number actually, mine is set for this), then you would set your low pass x-over at 120hz.... on tweeters, you'd have a high pass filter...

you had it right, although your example was wrong... the filter does essentially it's name... a low pass filter lets low frequencies pass, not allowing frequencies above a set freq. pass through... high pass does just the opposite, letting through all frequencies higher then the filter... so, we get these examples

a 120Hz low pass x-over/filter will let all frequencies 120Hz and below pass through, this is usually an ideal frequency for a ht system with smaller main speakers. with bigger mains, you can set the x-over lower because the mains will be able to hit lower than small mains will...

alternately, a 120Hz [i]high pass[i] crossover/filter will let all freqencies 120Hz and above pass through... the built in x-over on my system sets both at the same time... right now, it's set to 120Hz... the sub recieves the freq. below and the mains get everything above...

to answer your original question... if you are setting this for a sub, which it sounds like you are, you want to set your low pass x-over to whatever freq. you don't want to go above... if you are setting it for your entire speaker system, you'll want to set a low pass for your subs, a high pass for the other speakers at the same or near the sub filter, and a low pass way up at the frequency you don't want to hear above...

i hope that helped!!!

[Bobs89LXi]

What merlindavis is saying is essentially correct. High or low pass filters are technically known as bandpass filters. The allow frequencies either above or below the "set point" to pass, while blocking frequencies outside that range. If you want to pass or block specific frequencies, you'll need an EQ. The only drawback to an EQ is the fact that it must be installed between the pre-outs of the head unit and the amp. Most newer EQ's have separate bass or subwoofer outputs.

[87AccordsterLx]

sorry guys I should have specified that this is for my car sterio head unit.... I have the Alpine CDA-7893 ... It has options to set low and high pass x-overs as well as the center frequency... The center frequencey is basicaly a way to tune the frequency to a certain tone... what would be the correct setting to use for the x-overs on the deck? also what should I set my amps x-over to?

[merlindavis]

hmmm... if you have it built in to the deck, it may possibly be different... if you are running a sub, you'll probably want to have it on a non-faded or sub-specific pre-out, and also to use the crossover on the amp instead of off the headunit... what i'd maybe do is try to use the EQ for your mids and highs... heh, i only have an EQ on my deck, no x-over... i run with my bass flat and treble about mid-way... sub frequencies are set with the amp...

[87AccordsterLx]

I have the Alpine H/U powering 4 speakers... a 100 watt fosgate amp powering 2 6x9s on the rear deck (in the middle of the 6's) and a 400w Interfire Amp running 2 12' pionner IMPP's rated at 600w's ea. On the head unit the x-overs are for subs as well as the speakers... the Interfire amp is running off of a 4v sub pre-out and the fosgate is running of off a 2.5v rear pre-out... So if I wanted to set the low frequencies to have to limit and the highs to filter at a certian frequency which x-over would I set to what on the deck...? also what is a good frequency to set the amps x-over..? Sorry if this is really confusing....

[merlindavis]

hah, with the way you're asking it, it is kinda confusing... lol... anyways... if you are using a crossover on the amp, you shouldn't be using one on the deck itself, unless you are trying to get the speakers to run in a set range, not just limited at one end or the other...

here's my advice to you, for the amps, at least... i'm assuming you're using the 6x9's for mid-bass and not full range, so here goes:
set your sub low-pass somewhere around 60-80hz, especially if you have dedicated mid-bass woofers...
set the low-pass for your 6x9s between 130-160hz or so... i have no idea how Alpine's crossover system works so i can't tell you how to set it, but if possible, try and set your crossovers for the 6x9s so that they run only between near the cut-off freqency for your subs and whatever your high end cut-off for them is... that way you won't distort cause of too low freq's getting to them and they won't distort trying to play highs along with bass... then, if you can, set a crossover for the 4 speakers running off the head-unit to run at around the cut-off for your 6x9s and above, unless you have tweeters, too...

i'm sorry if i'm confusing... it's just that it's much much easier for me to explain in person and if i have access to a setup similar to yours...

what you can do is run to car-toys or the goodguys or whatever car audio places you got in georgia and tell them what you want to do... setting the crossovers for the subs should be no problem, setting them for the rest of the car may be more difficult...

okay, i don't want to go edit the stuff above so i'll just type it here... i was just thinking about how my setup is and may have a solution for you... here's what i'm thinking:

set the crossover for the subs on the amp, don't mess with the pre-outs for it.
if you can, set a high-pass for the pre-outs on the 6x9s at whatever your sub crossover is at, or set a low pass at whatever your 6x9 high end will be at... next, set the crossover on the amp for the 6x9s at whatever one you didn't set on the head-unit... in fact, if you can, just set a low-pass for all your pre-outs at the high end of the 6x9s, the set the low-pass on the sub amp, you'll have no problem cause it will be just blocking more... and set your 6x9 amp on a high-pass crossover, down near the freqeuncy where your subs cut off...
set a high-pass at your 6x9 high cut-off for the speakers running off your deck amp...

if you can get it setup like that, you will have your subs bumping the low end, your 6x9s for exclusive mid-bass, and the rest of your components won't sound nasty cause they aren't really trying to hit much bass...

if you take your car to a shop to have them try and help, try not to pay, sometimes those guys are nice and will tell you what to do just by chatting with them... go in and say "i have {insert head-unit, amps, and speakers here} and i want to run them like this, what do i do?"... if they have your deck or a similar alpine on display, have one of them show you how to set the crossover for your needs...

again, i hope this helps!!!
(bob, please criticize/add to my answer, you sound like you know what your talking about!!!)

[Mike's89AccordLX]

:super:

[87AccordsterLx]

thanks Guys.... !!! I have next weekend planed out for sure... I'll see what I can do and post the findings... on the H/U ... You can only set one range for the x-over I'll have to refer back to the manual 4 the deck and see exactly what it filters... as far as the tone of the music is concerned.. I have that center frequency option which lets me adjust the tone to certian frequency (ie. bass at 80hz, 70hz, 60hz etc... and treble at 150hz 160hz and 180hz... is it better to make your bass sound lower pitch and treble higher or is there a certain frequency that it should sound best at...??? Thanks for all the help guys and sorry for all of the questions....

[Bobs89LXi]

No need to apologize for all the questions. That is what we are here for.