hey, i have a simple crossover question... sorry for having to ask but something was confusing me quite a bit. basically:

1) High-Pass Filters (HPF) allow the frequencies ABOVE the setting selected to go through right?

2) so does that mean Low-pass filters (LPF) only allow the frequencies BELOW the setting selected to go through?

3) will setting the HPF to 80hz on my alpine have any effect on the subwoofer output??

 

1. YES
2. YES
3. NO

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nsxxtreme &raquo;</TD></TR><TR><TD CLASS="quote">1. YES
2. YES
3. NO</TD></TR></TABLE>

thanks. i knew i was a genius.

 

not to make things more difficult, but a crossover is not a brick wall....if you high pass your mids at 80Hz they will still play information below 80Hz. The filter is not up and down, but has a slope associated with it. Typical slopes would be 6, 12, 18, 24 dB/octave. Generally speaking amplifiers and headunits use 12dB/oct slopes.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rcurley55 &raquo;</TD></TR><TR><TD CLASS="quote">not to make things more difficult, but a crossover is not a brick wall....if you high pass your mids at 80Hz they will still play information below 80Hz. The filter is not up and down, but has a slope associated with it. Typical slopes would be 6, 12, 18, 24 dB/octave. Generally speaking amplifiers and headunits use 12dB/oct slopes.</TD></TR></TABLE>

Now we are talking about filter masks. Which define the stopband and passband as well as any ripple. Butterworth filters are usually used because they are maximally flat. A little more complicated then I think the original poster wanted to go.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rcurley55 &raquo;</TD></TR><TR><TD CLASS="quote">not to make things more difficult, but a crossover is not a brick wall....if you high pass your mids at 80Hz they will still play information below 80Hz. The filter is not up and down, but has a slope associated with it. Typical slopes would be 6, 12, 18, 24 dB/octave. Generally speaking amplifiers and headunits use 12dB/oct slopes.</TD></TR></TABLE>
so does that mean (since most HU's use 12db/oct slopes) that having my decks crossover at 80hz mean that all frequencies below 80hz have a -12 db gain?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by noob with an RS &raquo;</TD></TR><TR><TD CLASS="quote">
so does that mean (since most HU's use 12db/oct slopes) that having my decks crossover at 80hz mean that all frequencies below 80hz have a -12 db gain?</TD></TR></TABLE>

Definition of octave...
http://www.bcae1.com/octaves.htm

Definition of crossover slope...
http://www.bcae1.com/xovrslop.htm


Modified by kontai69 at 5:19 PM 1/17/2005

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by noob with an RS &raquo;</TD></TR><TR><TD CLASS="quote">
so does that mean (since most HU's use 12db/oct slopes) that having my decks crossover at 80hz mean that all frequencies below 80hz have a -12 db gain?</TD></TR></TABLE>
No, the crossover point is -3dB down every octave below this point is an additional -12dB. The -12 dB/ocatve is the slope of the line so the further you go out the more is cutoff.

Edit: The -3dB down point is when the gain is .707 down if you take 20log(.707) you get -3dB.




Modified by nsxxtreme at 4:11 PM 1/17/2005

 

weee this is making me think maybe I should try a 100hz crossover... but 80 is working ok for me... oh well lol I like to tinker

 

ohhhh i SEE... very good informative info for me. ten Q ten Q berry much.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kontai69 &raquo;</TD></TR><TR><TD CLASS="quote">Definition of octave...
http://www.bcae1.com/octaves.htm

Definition of crossover slope...
http://www.bcae1.com/xovrslop.htm
[/i]</TD></TR></TABLE>

Now to complicate things a little more. The picture in the link you posted has a gain of 1. 20log(1)=0dB

Now if you were to hook an amplifier up to this that had a gain of oh lets say 100. 20log(100)=40dB this is where the 0 on that chart would sit you would have to shift the entire chart up by 40dB.

 

so this being said, would it be a good idea to overlap some crossover points to insure the dip directly at the say.. 80lpf and 80hpf doesnt occur? from that graph, it appears there is a dip at where I think they are saying the point is..

For example would a LPF of 100 and HPF of 80 (or visa versa), be better than 80/80

 

*bump, cause im curious about my add-on

 

ic what yur saying coolbluedab. when i imagine the slope crossover points visually of 100 LPF and 80 HPF, it looks like you'd get a nice line where all frequencies would seem to kinda even each other out. . maybe giving you a greater sound quality because your subs would push MORE of what your components wouldnt. so if you asked me i would say 100 LPF, 80 HPF "looks" like it'll give u better frequency responses from your system better than 80, 80. but then again I'm just smart, not experienced.

 

got to agree with you, id ask caraudiopro, but this is an extensive convo this thread has, ... hopefully someone can say so

 

You have to do what sounds best to you. Someone can tell you how to set things up. You can even use a meter to tune your car to a completely flat response (if your speakers are capable of this) but this doesn't garantee it will sound good to you.

There will always be some margin of error. When you design a circuit exspecially mass production you choose parts around a specific frequency (if your designing a crossover). On a large scale these parts will vary in values. So even though it might be designed for 80Hz it might not actually be that. It will be close just not garanteed to be at 80Hz.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by noob with an RS &raquo;</TD></TR><TR><TD CLASS="quote">ic what yur saying coolbluedab. when i imagine the slope crossover points visually of 100 LPF and 80 HPF, it looks like you'd get a nice line where all frequencies would seem to kinda even each other out. . maybe giving you a greater sound quality because your subs would push MORE of what your components wouldnt. so if you asked me i would say 100 LPF, 80 HPF "looks" like it'll give u better frequency responses from your system better than 80, 80. but then again I'm just smart, not experienced. </TD></TR></TABLE>

you can't look at anything in car audio and say it will sound better....you can guess, but unless you listen, you will never know.

Sometimes underlap works well because speakers get cabin gain in certain areas and are being boosted by the car, not by the eq/crossover.

 

hey rcurley, i noticed your signature and saw that you have a setup that includes ID subs. I just hopped on the bandwagon and am looking to get one. how many are you running, what model, what size, what amp is pushing it, and HOW DOES IT SOUND???

 

About the Dip at x-over point: There will be a measurable abberration in the response, but because the slopes of the x-over are usually the same on either side of this point, the output will even out to something resembling a flat response. It won't be too bad if the levels are matched.

Objective measurements: To accurately measure and correct these issues, you'd need a measurement mic (and a powersupply for the mic), a laptop, and some software. An RTA or the mic's which come with current headunits are not adequate for this task. Note that the quality of the mic won't matter too much as long as its' characteristics are mapped in the software you use (the software will auto-compensate for shortcomings in the mic; imagine adding a response graph onto the ideal linear one in order to re-calibrate).

 

archmage.. do you know any web sites that go in-depth about using RTAs to tweak systems? im very experienced in computers. ive got just a LITTLE understanding as to what your talking about with measuring the frequencies. i really want to use an RTA to tweak my system. ive got a computer mic but i doubt that will work?? please help with info.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by noob with an RS &raquo;</TD></TR><TR><TD CLASS="quote">how many are you running, </TD></TR></TABLE> 2

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by noob with an RS &raquo;</TD></TR><TR><TD CLASS="quote">what model, </TD></TR></TABLE> IDQ12v2 d2

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by noob with an RS &raquo;</TD></TR><TR><TD CLASS="quote">what size, </TD></TR></TABLE> 12"

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by noob with an RS &raquo;</TD></TR><TR><TD CLASS="quote">what amp is pushing it</TD></TR></TABLE> PPI A600.2

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by noob with an RS &raquo;</TD></TR><TR><TD CLASS="quote">and HOW DOES IT SOUND???</TD></TR></TABLE> not installed right now, but I wouldn't have chosen them unless they were some of the best

 

I honestly don't have much RTA experience, but people who use RTA's to tune generally do it just to maximize their RTA score at organized judging events. An RTA will work in bands (generally 31), displaying an SPL for each frequency, but no information about what is in-between. Effectively, you get a segmented graph.

If you use a mic + software, you get a continuous graph = much more useful.

When I refer to RTA/software, I'm referring to the use of a microphone to measure the frequency response of the car; ideally this should be linear throughout the audible range. The RTA and Software are just methods of using the microphone.

As for websites about RTA - again, I wouldn't know. I'm sure you could google something up though...

http://www.etfacoustic.com/ -- I know this is a popular software choice. This is a popular measurement mic: http://www.partsexpress.com/pe...8-625 (And probably the best deal I've ever seen on it, ends Jan 31st).

And the Behringer deq2496 is a popular RTA choice; there are more expensive options of course.

They should have a list of compatible mic's for the software. If you mic can plug into the RTA / laptop, and can pickup frequency 20hz - 20khz, then I don't see why it wouldn't work.

You can prob. tell that I'm not a fan of RTA tuning by now...

Also: measurement setups like these should be used only by those who are extremely serious about their systems. This is a lot of effort...Must note that these measurements are also useless if you can't EQ to permanently tune your system.

 

And the IDQ subs are great.

I think a few people have had excellent results with Arc Audio's new subs. It seems that we don't know much about them, but their old line was a modified IDQv2, the new line is ? --- well reviewed I guess...

Don't forget the IDMAX though...