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If you wire an 8ohm and 4ohm load in parallel, you'll get a 2 2/3ohm load:

8 x 4
------ <- formula for figuring two coils wired in parallel
8 + 4 it gets more complicated when you have more coils.

A capacitor has the effect of resisting voltage as the frequency approaches DC, allowing AC current to pass depending on the capacitor value. In English: the capacitor cuts lower frequencies while letting higher friequencies pass. The rate is at 6db/octave.

I forget the math to determine this, but for example on a 4ohm load at various high-pass frequencies:

x-over hz/cap value in uF (microfarad)

50 / 53mF (milifarad)
60 / 442uF
70 / 379
80 / 331
90 / 294
100 / 265
120 / 271
140 / 189
160 / 165
180 / 147
200 / 132

Note: the capacitor will be placed inline with one of the leads of the speaker, it doesn't matter which one + or -. One other thing to remember: as the coil ages, gets hot or the frequency changes the impedence on the coill changes. This may effect the crossover point by a few hz, not too much.

Hope this helps!

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604 Posts
GSteg said:
what does frequencies and octave slopes gotta do with what he's doing?:confused:
My post was answering the suggestion on using an inline cap to filter out low frequencies from the 4" speakers up front.

you said run compasitors to get the bass out...i would like to do that for the front so i wont kill them...cant u make those?
The value of the capacitor (note: bi-polar capacitor only!)will determine the highpass crossover frequency. The 6db/octave aka "First order" cutoff slope is what you'll get by using a capacitor. High-end active crossovers (with adjustments for gain and cutoff; the ones that have to be powered and are inline with the interconnects/RCA lines) can feature up to 18 and 24db/octave slopes. For example, as you drop fequencies by one entire octave (explaining octave here is beyond the scope of the topic, though there are 7 in the human hearing range-I think) the power is reduced by 6db to the speaker.


it helps but can u break it down a little..?? haha im not too it safe to do what i am thinking of doing??
Depending on the amplifier that you have running your 6x9's, it may or may not be safe. Check the specs and make sure that it's stable to 2ohm stereo.

The highpass crossover formulas are IF you want to use a cap and keep your front end sounding good. Those 4's will probably distort with low frequencies, so I would recommend it.

Unfortunately, I can't explain this "graphically" since it is all math and theory. If you want me to suggest to you a crossover frequency, I'd use around 150hz for those 4's. So... find a pair of 170uF to 180uF caps and simply insert (crimp, but preferrably solder) them inline with the speaker wires to the input terminals on the 4's.

I'll try to find you some websites that'll make it clearer if you need. Or, tell me what you need me to clear up for you and I'll fax you a diagram (unfortunately, I won't be able to draw up and post an image anytime soon for everyone to see).

o what about my power rating??? if my amp is 280 and each channl puts out about 100 rms...then splitting one side with 2 speakers would put it down conciderably?? or not as much? the fronts are not that big, only like 45 watts.
Is that the rating of the amp @ a 4ohm load stereo or what? If it is @ 4ohm and you put a 2ohm load on it, the power will increase (sometimes up to 200% or more on high-current amps... so check with the manufacturer of your amp).

Now that I think about it, this is a bad idea. The only solutions I can think of is using a different amp or attenuating the 4's with some resistors... which messes up your impedence loads and crossover frequencies. The best option would be to run an 8ohm load (wire the right side and left side individually in series). The output of the amp will be lower, but it'll run cooler and your fronts won't blow up.

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604 Posts
AccOrDZteCh said:
i was looking over my performance paper that came with the amp. it said ona 4 ohm testing max power 69wrms/ch
-188db signal to noise ratio

2 ohm testing
max power 126wrms/ch

so let me get this straight...a 2 ohm is bridged right? i feel dumb. lets say i am going to wire my speakers front and i wire in parallel or series? damn now i have to upgrade my power wire from 10 guage.
Bridging is summing two channels into one (or 4 into 2) for more output from your amp. Impedence is measured in ohms, and acts similarly to resistance and is calculated in the same way.

Going back to the formulas at the top of the thread, if you wire two 4ohm speakers in parallel you get a 2ohm load for BOTH. If you wire them in series, you simply add up all the impedence values for your final load.

I mentioned wiring your speakers in series before we knew what you amp is capable of. It'll do fine pushing a pair of lefts and a pair of rights which are wired in parallel (++ and -- just wired together). You won't be able to fade this setup forward/back unfortunately.

..u guys are really help full just to let u know.
No problemo!
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