Setting LPF

I just got my new JBL 600.1 all hooked up!! Me and my friend did the install last night, and I think the whole thing looks pretty good, ill post some pics of I can get my hands on a digital camera. Today I have to put my back seat back in, botl everything down, clean everything up and tweak all the settings. Which brings me to my question. What is the best place to set my LPF at? On my other amps I just set it by ear. The LPF on the amp goes from 30hz to

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First, what size speakers are you using for your: sub, mid-bass, & mid-range??

For a mid-bass size of 5.25 I would set the LPF at ~100Hz
For a mid-bass size of 6.50 I would set the LPF at ~80Hz

That is also the same frequency you would set the HPF for your mid-bass. Set the LFP and HPF at the same frequency so as to not cause any overlapping.

Paul

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This amp is running my subs only, no other speakers.

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Right ... but you should still have some sort of crossover on your other speakers.  What size speakers do you have up front?  You should follow the guideline that francious gave you.

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New Project: 2003 Pathfinder

i agree with what you said about having his other speakers crossover kfr, but as far as 100hz, is that not too low for midbass. not too low as in it wont doit, but if you have a decent sub, can it not handle doing 200hz even?

if it was me, i would want to set it as high as possible without running the sub into frequencies which tend to be less 'bassy', ie: 120-150hz? and if you crossed over your speakers to around that would you not get more out of them?

maybe i misinterpurted the Francious's post.

I end up tweaking by ear, anyhow.  But note that the LPF is lowpass for the subs, and HPF is highpass for the mids and tweets.

/r7, no, crossing the sub over that high probably isn't a good idea.  First, you should know that a crossover doens't just stop at the crossover frequency.  It'll still be playing octave(s) above the xo frequency depending on the xo slope.  Many car audio subs will encounter breakup (some crazy freq. response) if crossed too high.  Second, bass is easier to locate the higher it is crossed over.  Third, by asking the sub to do more, you're taking power away from what it does well.  Fourth, his subs are probably located far away from his mids and highs.  As the wave lengths decrease at higher frequencies he'll start encountering more phase related cancellation effects. 

I'd keep the sub crossed over at 100hz or below if at all possible.

A good 6.5" midbass driver can be crossed over successfully at 100 or 80hz with a 2nd order or higher xo.  You're right though, this can stress the midrange... this is why some people upgrade to 3-way systems.  :-)

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New Project: 2003 Pathfinder

thanks, clears things up quite a bit. I understand that crossing over doesnt cut it off like black and white. however im not really clear on the difference between a 12db slope and a 24db slope, im assuming 24db is alot stronger and accurate, than a 12db slope? its time for some research.

kfr01] wrote:

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ou're taking power away from what it does well.

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is this the opposite for midbass speakers, i find crossing them over, allows them to get louder, and clearer as they go louder.
i assume this is because the speakers dont have to exert themselves with the lower frequencies.

/R7]th wrote:

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nks, clears things up quite a bit. I understand that crossing over doesnt cut it off like black and white. however im not really clear on the difference between a 12db slope and a 24db slope, im assuming 24db is alot stronger and accurate, than a 12db slope? its time for some research.

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When frequency doubles you have an octave.  80-160hz is an octave.  If you crossover at 80hz with 12db slope at 160hz you'll be 12db down from the pre-crossover level.  I say pre-crossover level because the crossover point is always 3db down for any slope.

Here's an excellent page on https://www.bcae1.com/ explaining this... https://www.bcae1.com/xovrslop.htm

btw - no problem, I'm glad to help and test my knowledge at the same time!  :-)

/R7]is wrote:

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this the opposite for midbass speakers, i find crossing them over, allows them to get louder, and clearer as they go louder.
i assume this is because the speakers dont have to exert themselves with the lower frequencies.

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Yes, generally whenever a speaker is asked to play less bandwidth near its limits it can perform better.  I recommend what I do because a decent 6.5" midrange can handle a 80-100hz xo better than a 10"+ car audio subwoofer can generally play with a 150hz xo.

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New Project: 2003 Pathfinder