I have a crossover question for any audio guru's or installers out there. Thisquestion has been plaguing me for the longest time, so hopefully you can help me understand the following a bit more. Sorry if this post is lengthy.

My current setup consists of:

Kenwood KDC-MP4028 HU
Polk MMC5250 5.25" - Front
Polk MMC6500 6.5" - Rear doors
JL Audio Stealth Box w/2 8" JL Audio 8W04 subwoofers
Rockford Fosgate P4004 running the front and rear components
Rockford Fosgate P4002 running the subs

I tinkered with my system for well over 4 months now, trying to adjust the crossover settings, searching for that ever-elusive "sweet spot". I've been running my current settings for well over a month now, and they seem to be okay, but i know i can tweak it just a touch more for better performance. In order to do so, i really need to understand the difference between the built-in headunit crossover settings and the crossover settings on the amps and howthey interact, or interfere, with one another.

Right now, i have the headunit's crossover settings set for 80hz HPfront,100hz HPrear, and Pass-Thru set for thesubwoofer. On the amp's crossover settings, i have the front set for 80hz HP, and the rears set at80hz HP. On the sub amp, i have it set for 80hz LP.

So with that being said, how does the flow of signal work from the headunit to the amp when dealing with a headunit that has abuilt-in crossover?

As an example: If i set the headunit to120hz HP for the front, and then set the crossover on the amp for 80hz HP for the front, what is actually being used? Does the amp see that all frequencies from the headunit below 120hz are beingblockedand only plays those frequencies even though the amp is set to block frequencies below 80hz? Or does the amp say, "screw you headunit, i'm going to reconvert your signal, and block out anything below 80hz"? Ordoes it split the difference 120hz HU + 80hz amp = 200hz/2, and play 100hz?

When i set the headunit crossovers to pass-thru all around, and rely solely on the amp crossovers, it seems to sound a littlebetter, but the bass sounds really muddy. If i use the headunit crossovers, the bass hits much tighter, but not boomy by any means. I listen to a lot of rock/metal so i'd like to find a happy medium.

Could anyone offer suggestions on where i should set my crossover settings for either the headunit, amp, or both? 80hz seems to be the right setting for these speakers, but i feel like i'm missing something in my system equation.

Any help or insight would be appreciated. If i haven't explained myself fully, or if you need more info, please let me know - thanks!

p.s. - i should mention, the crossover settings available on my HU are:

Pass-Thru, 80,100,120,150,180 HP (front and rear)
Pass-Thru, 60,80,120 LP (Sub)

 

Well if the radio is set at 120Hz and the amp is set at 80Hz then you should have something like 100Hz. The way I tune it in is 1st pop in the music that's getting played most in the car. Set the HU & amps according to the speakers rating and back off the power slightly at full power because all music is not the same. When its time for the subs its the same thing basically just with the interior off if posible. I dont have all the fancy instuments that shops use to tune a system but I must be doing something right since I always have someone asking me to tune there system in.

You could also get an EQ to dial in that system even more but as far as keeping it simple just set the amps and make adjustment on the HU if needed between music.

 

Thanks new2me -i believe what you've described is how to set the gains, which i'm familiar with. I guess i'm really looking on how to make my current setup run more efficiently by properly setting the crossover points so that the image comes from the front.

Right now it's not too bad, but i know i can get it to move forward a little bit more if someonecould dissect how exactly the headunit and amps interact with one another when it comes to thecrossover settings.

 

Gainis the amount of power you are applying but you need to setthe frequency to what your speaker's are made for along with a little tweaking to the music you listen too.

The amp and HU will perform exactly how you set it. If you set the amp to operate for low's and the HU for highs its going to sound like poop. Because the HU is sending high frequencies to the amp its not getting the lows which its set to except. So if you set the HU to 100Hz for the rear then the amp should also be set at that.

What is the problem that you are trying to tweak? High's low's..............

 

My components are recommended to be set, and sound best,at 80hz HP - per Polk technicians.

So i guess i'm asking: What is the best way to ensure that my components are running at the proper 80hz HP setting? Should i leave both the HU and amp at 80hz HP, or should i leave the HU at Pass-Thru HP and run the amp at 80hz HP?

You would think that either way, they would receive the correct 80hzHP setting, but i would disagree because they sound much differently between the two above settings.

 

I think what you are looking for is here

http://www.the12volt.com/caraudio/cross.asp

 

Since your H/U has an internal xover, I would defeat any xovers in the RF amplifiers. They're not needed. Use the 80hz highpass for both front and rear outputs, and 80hz lowpass for the subwoofer.

 

This is not true. In this example, it's a highpass filter, so the highest number 120hz will be dominant. Anything lower than that will be filtered out by this filter. There's no "averaging" of numbers/frequencies.

Similarly, if you have a lowpass filter, whatever number is lowest will be the deciding frequency.

 

Thanks guys. Flyboy - when you say to defeat the crossovers on the amp, are you implying that i setthe amp to the AP "all-pass" setting for each channel, and let the HU do the crossover work for me?

 

Yes. Exactly.