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  1. #1

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    Default Crossover question?

    Okay, my question is, is car audio the same principal as home audio. Meaning, my Alpine CDA-9835 head unit has built-in crossovers and so do my Alpine amplifiers. Do I turn the crossovers on the amplifiers all the way up or disable them to allow my head unit to handle them to prevent double filtering or are the crossovers independent of one another? Here is a pic of the amplifier controls http://www.crutchfield.com/App/Produ...0MRPF300&g=120 Do I just set the filters to "OFF" which in return would disable the crossovers? Any help would be greatly appreciated.

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  2. #2

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    Disable which ever crossover you dont want to use.

    Maybe the deck has an 18db crossover you would rather use than the 12db in the amp or vise versa.

    I would use one or the other.

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    Your head unit has a MUCH better and more flexible crossover than your amps will so Id suggest using that one. Plus the fact that with all the controls on the head unit, you can tune things in real time as opposed to having to get out and go back to the amps everytime you want to make an adjustment. This way you will get a much better idea of what the changes do.

    So Id turn off the amp's crossovers and use the ones on the head unit.

    Id also suggest, if youre running a 4 channel amp, to run the tweeters off the front channels and the mids off the rear channels in a bi-amp configuration. This way you can adjust the crossover slope and cutoff point of each driver.
    Last edited by MacLeod; 01-10-2009 at 12:47 PM.
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    yeah, that'd b sweet

  5. #5

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    On a related crossover note...If my HU were to have (haven't actually gotten it yet) an 18db/octave crossover, but for some reason that were not a steep enough slope for the application; would an additional outboard active crossover placed before my amplifier behave strictly additively? like if i had an 18db HU crossover and a 24db active had them both set to 60Hz for my mid, would that be 42db/octave...or is there some other mathematical relationship for the effect on the signal. I figure that selecting the frequencies that i want the amp to work on before it actually amplifies would be much more efficient.

    Also, I am not sure which brands make good outboard active crossovers which can be used with any brands HU (like not having to worry about needing to match alpine crossover with an apline HU). Do the ones on the market now usually do a single job as crossover, or multiple such as crossover, power supply,DAC , phase regulation etc?

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    slow down there dude. your planning on buying a hu? then get one w/ 24db! that don't sound right. if u have a 12 and a 24 they would work 2gether. amps usually have 12db fixed. my cds 24. at same freq, 24 cuts off more so u would hear that. for my highs i use 6 on my hu, 12 on amp. amps r fixed. that help? 24 more cutoff of course, 6 less. same freq. go by whichever cuts off more

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    You dont want to mix crossovers. Your head unit would be attenuating at 18 db per octave then your outboard crossover comes in and starts cutting it at another possibly different slope. That can screw things up. There is more to a crossover than just cutting off a certain frequency - you have to make one driver blend with the other driver and that means both drivers rolling off together rather than opposing each other.
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    oppose this how do u turn an amp xovr off?? what else do they do besides cut off freq.? i think your hu xovr CAN b better depending on the amp. hu xovrs r basically fixed freq., amps usually variable, but fixed slope(of course depending) its hard for 5 1/4s to oppose 12 inch subs. i usually xovr for each speaker seperately(pair). first highs, then mid, then low. not all at same time. tweak highs, tweak lows, if nicely choosen system, it'll sound nice. i first set hu, then fine tune w/ amp hope that made sum sense

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    Its not hard at all for 5.24's to oppose a sub of any size. Both can easily reproducde 60 Hz and if theyre opposing, they cancel each other out. 5.25's can also fight against the tweeters. Oddball crossover slopes can and will cause phase issues and this can and usually does result in cancellation.
    polkaudio sound quality competitor since 2005
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  10. #10

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    Actually if you could get a 100hz crossover on your headunit at 18DB and a 100hz crossover point on you amp at 18db then the two would equal 36db at 100hz. But since that is almost impossible given the fact that even if the crossover point on both units says 100hz due to different tolerences in eletronic components you would not be at exactly 100 hz. The crossover built into the CDA9835 allows for different slopes and crossover settings which should be more than sufficient for your system. Plus as Mac said its easier to adjust thme from the headunit than the amp. So turn off the crossovers on your amp. If you are unable to turn them off completely then on a subwoofer amp turn the crossover to its highest setting and on a mid/high amplifier turn it to its lowest setting.

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    maybe not srs, not evry1 has $800 front speakers. 60hz easy? my eclipse comps r crossed at 125hz. how about 80hz(sounds reasonable). if both r crossed at 80 and both can handle it so what? more bass up front, no? oddball guru advice can and will cause sound issues and usually does result in ignorance. i'm sorry mac. what do u mean by phase issues and cancelation. u mean u won't b able to tell where sound is coming from? which speaker is sending those freqs? thought thats what u wanted. i'm def missing something. help me

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    Quote Originally Posted by Grimster74 View Post
    Alpine CDA-9835 head unit has built-in crossovers and so do my Alpine amplifiers.
    I have a 9831 and love it with my Alpine PDx's. What do u have ur different settings on ur deck and amps?

  13. #13

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    yeah, i'm def missing something. so your saying having both sources at 100hz at 18db makes the slope twice as narrow(36db). wouldn't they b the same?and Not effect one another. so your saying the amp sees the 18db from the hu and sends out another 18db of slope? wouldn't the optimum b to set hu xovr and tweak w/ amp xovr. sure u could turn your hpf all the way down but couldn't u at least try to pull a few more notes out of those $800 fronts. specially when more $ Usually goes into amps, not hu. (except for most polk sr owners)

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    Quote Originally Posted by cadenceclipse View Post
    maybe not srs, not evry1 has $800 front speakers. 60hz easy? my eclipse comps r crossed at 125hz. how about 80hz(sounds reasonable). if both r crossed at 80 and both can handle it so what? more bass up front, no? oddball guru advice can and will cause sound issues and usually does result in ignorance. i'm sorry mac. what do u mean by phase issues and cancelation. u mean u won't b able to tell where sound is coming from? which speaker is sending those freqs? thought thats what u wanted. i'm def missing something. help me
    Dude your posts hurt my eyes. You really need to put a little more effort into making your stuff readable.

    Any midrange driver worth anything will play down to 63 Hz easily. Even the crappy paper cone speakers that came in your car will - and so will your sub so if theyre out of phase with each other they most certainly can cancel each other out.

    Phase issues and cancellation work like ripples in a pond. Throw 2 rocks in a pond about 10 feet apart and watch the ripples. They are nice and smooth until they run into each other then they break each other up. This is what happens when youve got one speaker playing a certain frequency and another speaker playing the same frequency but in a different phase. They cancel each other out.

    Im not saying that cascading crossovers will definitely cause phase issues - but I am saying that it certainly increases the odds this will happen. I find its always better to keep things simple.

    Quote Originally Posted by cadenceclipse View Post
    yeah, i'm def missing something. so your saying having both sources at 100hz at 18db makes the slope twice as narrow(36db). wouldn't they b the same?and Not effect one another. so your saying the amp sees the 18db from the hu and sends out another 18db of slope? wouldn't the optimum b to set hu xovr and tweak w/ amp xovr. sure u could turn your hpf all the way down but couldn't u at least try to pull a few more notes out of those $800 fronts. specially when more $ Usually goes into amps, not hu. (except for most polk sr owners)
    Yes, it would be 36 db. The head unit attenuates say 100 Hz by 18 db then when the amp gets it, it attenuates it another 18 db so its 36 db lower than it was originally.

    And its not about getting more notes out of your speakers - its getting them to work TOGETHER as seamlessly as possible.
    Last edited by MacLeod; 01-16-2009 at 10:48 AM.
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    ok that makes sense thanks again mac! aren't bigger slopes usually more desirable? what if your talking 2 different freqs, say 65hz at 18db and 70 hz at 18bd. would u still say 36db? hope u can read this mac!

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    Quote Originally Posted by cadenceclipse View Post
    ok that makes sense thanks again mac! aren't bigger slopes usually more desirable? what if your talking 2 different freqs, say 65hz at 18db and 70 hz at 18bd. would u still say 36db? hope u can read this mac!
    Bigger slopes are usually more desirable for the sub-mid cutoff, but play around to find what sounds best. 24 db is the most common.

    I wouldn't mess around with two different slopes, sometime less is more. I doubt you will want to use a 36db slope, but if you want the option then buy a Hu or crossover with the capability.

    You should do some research on your own. Google crossover and slopes to read up on how they work. This will help you understand what's going on. They have articles and articles of information that would be hard to post in a few paragraphs.
    Last edited by dirthog; 01-19-2009 at 12:20 PM.
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  17. #17

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    Quote Originally Posted by dirthog View Post
    Bigger slopes are usually more desirable for the sub-mid cutoff, but play around to find what sounds best. 24 db is the most common.

    that makes sense considering i always had bigger slopes at those (lower)frequencies.

    I wouldn't mess around with two different slopes, sometime less is more. I doubt you will want to use a 36db slope, but if you want the option then buy a Hu or crossover with the capability.

    unless i "turn off my amps crossovers"(whatever that means), won't i always....Usually less is more. why not 36db, been hearing bout some sik systems w/ 48db throughout!. r there hus or xovrs w/ that capability??

    You should do some research on your own. Google crossover and slopes to read up on how they work. This will help you understand what's going on. They have articles and articles of information that would be hard to post in a few paragraphs.
    read em.....think i know whats goijg on thanku sory bout anwers coulple lines up

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