I've hit a bit of a snag with my stereo project.

I have a 2-channel amplifier from eBay, and I've been using it with 4Ohm speakers, one on each channel.

Now I planned to upgrade it with tweeters. I got a 3.9uF capacitor for my tweeters, thinking of connecting it in parallel. I got a set of tweeters of 8Ohms each.

I realized something..

Connecting my 4Ohm speaker and 8Ohm Tweeter (Tweeter in series with a Capacitor) in Parallel, results in a net resistance of 2.67 Ohms and will cause a problem for my amplifier.


simulate this circuit – Schematic created using CircuitLab

It seems putting these two speakers in series will be better as it will give a net impedance of 12 Ohms. But Where how can I connect the capacitor (as a high-pass filter) for my Tweeter?

Any other way I could proceed with this?

I saw a method to do it in series..

enter image description here

But I do NOT have a Low pass filter (I assume an inductor)..It would be better, because I don't have the time to procure other components :(

  • \$\begingroup\$ how do U know it is a problem in shunt? Series is a bigger problem. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jul 16 '17 at 23:55
  • \$\begingroup\$ u need 2 LC pairs nonpolar \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jul 17 '17 at 0:03
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    \$\begingroup\$ Always start with a spec. ! How you want power to be shared, breakpoints, peaking (Q), overall impedance (f) ok, got it? or if you prefer, passband loss at f, stop band loss at f for each. Crossover f. ok? \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jul 17 '17 at 0:25
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    \$\begingroup\$ I made this for you tinyurl.com/ya388rzl \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jul 17 '17 at 0:37
  • \$\begingroup\$ what you have should be fine if you run it at slightly reduced volume levels. \$\endgroup\$ – Jasen Jul 17 '17 at 4:59

If you are worried about overloading the amplifier then I wouldn't be overly concerned unless you were intent on playing very loud passages of sound that were exclusively in the low to mid kHz region (not something that normal or even modern music attempts to do).

The 3.9 uF capacitor starts to "bring-in" the tweeter at a few kHz and above so if you are really worried about loading then consider putting an inductor in series with your woofer so that as frequency rises, the woofer is progressively removed from circuit. Something about 1 mH should start reducing the loading effect of the woofer from about 1 kHz upwards.

Alternatively, find one of the several web-site tools that calculates proper cross-over components values and do the job properly.

I don't have the time to procure other components

Sometimes, you just can't make a silk purse from a sow's ear

  • \$\begingroup\$ Thanks for your answer. It looks like I'll just buy a new set of speakers. I'll probably take your advice on the Series Inductor. BTW - do you feel a 3.9uF capacitor is enough for a tweeter? Would you recommend going for a 2nd order High Pass Filter? Not that it's an expensive tweeter, but it's also nice to know. :) \$\endgroup\$ – Paolo Jul 20 '17 at 0:12
  • \$\begingroup\$ The capacitor needs to be selected with respect to the tweeters impedance. I would say on this occasion that if I assume the tweeter is 8 ohm then 3.9 uF is a little low but there are good website calculators that can provide values. Thanks are appreciated but even more so when an answer is formally accepted. \$\endgroup\$ – Andy aka Jul 20 '17 at 6:24

Usually cabinet and P.A manufacturers (as Peavey , Ashdown , D.A.S) solve this problem with a 10 Ohm serial resistor to one of the tweeter terminals. It would be a big one; for example, a 2 watt resistor.


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