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Audio Filters

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TheNewGuy

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Hey everyone,
So I recently I've been messing around with the sound system in my car, and here is the set up:

I got a head unit and ran RCA cables to the back of the car to an amplifier which is connected to two 12" subwoofers. So in total I have two speakers in the dashboard (don't know what size but smaller than 6" x 9") and two speakers in the back (6" x 9") and two subs in the trunk.

Right now, when I push the volume up to half way the subwoofers aren't playing that loud and the rest of the speakers sound like they are ready to explode.

So, now the problem to tackle becomes: I want the speakers and subwoofers to play the frequencies they were designed to play (subwoofers playing low and 6x9 speakers playing high frequencies).

That means I'm going to have to build four separate high pass filters (there's no way to do it with one without ruining stereo?). Also, that means I'm need to find out what is the max output of the head unit and build the circuit to be able to handle that output. Can anyone explain what that means in regards to the circuit, and possibly suggest a good one?

-TheNewGuy
 
Don't you have level controls somewhere you can adjust to balance the subwoofers with the rest of the speakers? I assume there's a separate amp for the subwoofers: does it have a separate volume control?

I guess that would be too easy if you're asking about building filters here ...
 
Might be easier to build low pass filters for the sub woffers and add some amplification for the RCA plugs. Or maybe just amplify the RCA plugs.
Do you want to build a circuit or buy something?
 
High end systems do limit the low frequency signals to the small speakers, but it isn't normally a problem to let those speakers respond to total signal, so I wouldn't bother adding a high-pass filter to the 6 x 9 speakers.

You do want a low-pass filter for the woofer amp. Also, as CZ noted, there should be a volume adjustment for the woofer amp. If not, you may have to add an additional amp with volume control to feed the subwoofer amp.
 
Don't you have level controls somewhere you can adjust to balance the subwoofers with the rest of the speakers? I assume there's a separate amp for the subwoofers: does it have a separate volume control?

I guess that would be too easy if you're asking about building filters here ...

That's what I thought! I thought my head unit would allow me to specify what frequencies I would want on certain speakers but it doesn't. :/

Might be easier to build low pass filters for the sub woffers and add some amplification for the RCA plugs. Or maybe just amplify the RCA plugs.
Do you want to build a circuit or buy something?

High end systems do limit the low frequency signals to the small speakers, but it isn't normally a problem to let those speakers respond to total signal, so I wouldn't bother adding a high-pass filter to the 6 x 9 speakers.

You do want a low-pass filter for the woofer amp. Also, as CZ noted, there should be a volume adjustment for the woofer amp. If not, you may have to add an additional amp with volume control to feed the subwoofer amp.

Yes, the amplifier has a both low and high pass filters and I've set the low pass filter. So the subwoofer is playing low frequencies only. It's just I can only go half of the volume on my head unit because it sounds like the other speakers are at their max.

EDIT: I guess I could turn up the gain on the amplifier? But I would have to do it just right to get it to sound good? Would a filter make the 6X9's last longer?
 
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EDIT: I guess I could turn up the gain on the amplifier? But I would have to do it just right to get it to sound good? Would a filter make the 6X9's last longer?
Typically you just turn up the gain until you get the amount of bass you like. Home stereos typically output a tone that you can use to balance the speaker outputs (with a sound level meter for exactness) but that's generally not available in an automobile sound system.

The 6x9's will likely last as long as your car with or without a filter. The filter would have little effect on their life unless perhaps you are seriously overdriving them.
 
to answer one question, line level outputs are generally 1.5Vrms for max output from an amp (and the gain of a power amp is usually designed to be such that the amp clips with a 1.5Vrms input).

there should be a gain control on the amp you're using for the subs, and there are amps designed for driving subs that also have the filters in them.

any bass that you are sending to small speakers that cannot reproduce bass is wasted power (and will distort, making them sound awful)

you can use a crossover filter to cut the bass to the small speakers and feed the low freqs to the sub amp (filter AND attenuate before going into the line level inputs).
 
Typically you just turn up the gain until you get the amount of bass you like. Home stereos typically output a tone that you can use to balance the speaker outputs (with a sound level meter for exactness) but that's generally not available in an automobile sound system.

The 6x9's will likely last as long as your car with or without a filter. The filter would have little effect on their life unless perhaps you are seriously overdriving them.

I wish all stereos would allow you to balance like that. It would allow for better tuning and so on.

to answer one question, line level outputs are generally 1.5Vrms for max output from an amp (and the gain of a power amp is usually designed to be such that the amp clips with a 1.5Vrms input).

there should be a gain control on the amp you're using for the subs, and there are amps designed for driving subs that also have the filters in them.

any bass that you are sending to small speakers that cannot reproduce bass is wasted power (and will distort, making them sound awful)...

Mine has filters, I think I'll tune the low pass filter for the amp for the subs a bit and turn up the gain a bit also.

...you can use a crossover filter to cut the bass to the small speakers and feed the low freqs to the sub amp (filter AND attenuate before going into the line level inputs).

I think that is what I'll do. The output RMS from the headunit be different (voltage/amperage) than the amp right? I wonder if I would have to find a schematic designed to handle that kind of wattage? (I think this headunit is 52 Watts per channel, I will double check that). I think I'll etch like four of them real small and somehow stuff them somewhere. Plus I think this kind of thing could come in handy somehow in the future if I get it working right. I would like to keep this speakers efficent and make them last long. From what I've heard Pioneer makes good quality audio products.
 
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I guess I'm still having a hard time believing that your problem can't be solved simply by adjusting your existing system. After all, you can't be the only person who needs a car stereo system to be tweaked to sound right.

Not that I'm trying to talk you out of building anything: I think it's great fun myself. But this might be a case where you really don't need to add any circuits to make your system work the way you want it to.

Do you have an owner's manual for it? does it tell you anything useful in this regard?
 
I guess I'm still having a hard time believing that your problem can't be solved simply by adjusting your existing system. After all, you can't be the only person who needs a car stereo system to be tweaked to sound right.

Not that I'm trying to talk you out of building anything: I think it's great fun myself. But this might be a case where you really don't need to add any circuits to make your system work the way you want it to.

Do you have an owner's manual for it? does it tell you anything useful in this regard?

Yes! I found a HPF setting on my head unit. No need for a circuit, haha. :p I can tell the difference with this setting though, it sounds better.
 
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