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phish368
06-18-2007, 03:32 PM
Sorry for the noob question but its something I never quite understood.. Maybe someone can explain it to me like im a 3 year old (yea im totally serious too.. lol)

If my fronts System Frequency Response is 59 Hz - 25 KHz 3 dB does that mean:

A. the HPF crossover point I set them to should be as close to 59hz as it can be? Also, if its closer to 59hz, should my slope be higher or lower? (i can choose between 6/12/18/24/30)

B. If I select a slope of 6 or 18db I believe I was told i should change the phase from 0 to 180, is that correct?

Thanks for whoever decides to help me

MiniVanMan
06-18-2007, 03:57 PM
Whoa, back up a bit there.

Frequency response doesn't necessarily dictate crossover points.

Here's a few links to get you started. If you have questions, and you will, after reading these, then by all means ask then.

This is a very tough subject.

To answer your first question though. 59hz - 25 khz +3db means that output of the speakers will not deviate more than 3 db either direction across the entire bandwidth of the speakers. Remember +3db is double the output, and -3db is half. Those are huge fluctations. There's also a ton of other factors involved.

So here are the links.

http://www.caraudio.com/forum/showthread.php?t=239080

http://www.caraudio.com/forum/showthread.php?t=239081

Stel
06-18-2007, 05:33 PM
Frequency responses listed like that are not usually very useful. It's usually measured at power levels lower than normal listening levels.

Generally the higher you cross them over the more you hear from the direction of the subs and subs usually won't player higher tones well (bad for a SQ based system). Too low and your fronts won't have enough output at those low frequencies (bad for a SPL or SQ based system). I would try a 18 or 24db slope. Subs and fronts are commonly crossed over in the 70 - 100Hz range.

squeak9798
06-18-2007, 05:49 PM
Sorry for the noob question but its something I never quite understood.. Maybe someone can explain it to me like im a 3 year old (yea im totally serious too.. lol)

If my fronts System Frequency Response is 59 Hz - 25 KHz 3 dB does that mean:

A. the HPF crossover point I set them to should be as close to 59hz as it can be?

No.

As was mentioned; It simply means that at 59hz the response of the speakers will be down by -3db and alone is not very useful. I doubt they mentioned how they determined the frequency response; But chances are good it was either anechoic (meaning no reflections or other environmental effects) or some other form of measurement that is not going be similar to your installation or environment.

How you install the speakers (in an enclosure or "infinite baffle") as well as the acoustics of your vehicle are going to dictate the response.

Manufacturer's rated frequency response is not good for much of anything, really.



Also, if its closer to 59hz, should my slope be higher or lower? (i can choose between 6/12/18/24/30)

Your installation and environment is going to dictate the crossover frequency and slope. How you install the speakers (again; enclosed or infinite baffle), the power you are sending the speakers, your listening material and listening habits, the vehicle's acoustics aswell as proper integration with the rest of the system (i.e. integration with a subwoofer) is going to determine what xover frequency and slope is the best fit.

It's honestly one of those things you just need to get in the car and listen to. Play various types of music that you are familiar and fiddle with it until you find the best combination of xover point and slope.




B. If I select a slope of 6 or 18db I believe I was told i should change the phase from 0 to 180, is that correct?


Not necessarily.

In a perfect world (and primarily in home audio where things can be closer to "perfect" than they are in our world of car audio) you could determine proper phasing of drivers based on xover slope. But in car audio, where there is a huge amount of reflections aswell as differing and less-than-ideal speaker placement it's really darn near impossible to know what drivers will need to have their polarity reversed without installing the system and going through the proper tuning steps.

So the short answer is no, not necessarily....but possibly. It all depends on the installation and your vehicle's acoustics.