# Simplifying electrical circuits

I have looked everywhere, but I can't seem to find a way to simplify this circuit. I wish i could tell you some of my ideas, but I'm really lost here, can someone help me? If you could explain how to go about it, it would be awesome.

• This is a crossover filter arranged so that one loudspeaker receives high frequencies whilst the other loudspeaker receives low frequencies. – Farcher Sep 23 '19 at 15:29
• Would Electrical Engineering be a better home for this question/ – Qmechanic Sep 23 '19 at 15:41
• @Farcher How does that work? – Keinicke Sep 23 '19 at 15:47
• Alright, so i get the idea now, of how this works, we have a low pass filter on one of the speakers and a high pass on the other, naturally the speakers are parallel to the filters so the get the same voltage drops across them. What i don't see is whether the speakers are/should be in series or parallel. It sure looks like a series but i found other illustrations looking differently? Btw @Qmechanic i don't know how i can move this thread to Electrical Engineering, do i have to make a new post? – Keinicke Sep 23 '19 at 16:35

The schematic is a bit confusing, because the 2nd loudspeaker is drawn "upside-down" with its driving signal connected to its lower terminal. It might be more clear (but take more space) if you draw it this way,

simulate this circuit – Schematic created using CircuitLab

There is nothing more to simplify. You can use mesh or nodal analysis to complete the analysis of the circuit.

The speakers are neither in series nor in parallel. They are just sharing a ground node.

• Oh i see, this makes a ton more sense, i thank you! – Keinicke Sep 23 '19 at 17:37
• @Keinicke, do you see why my schematic is equivalent to the original one? – The Photon Sep 23 '19 at 17:38
• Yes i do. you basically mirror the filter for speaker 2 and the speaker itself on the "output wire", nothing fancy going on. Which program do you use to draw these? – Keinicke Sep 23 '19 at 17:40
• @Keinicke, it's CircuitLab, which is built in if you click the "circuit diagram" icon when editing a question or answer here (on EE, not Physics; and on desktop rather than mobile) – The Photon Sep 23 '19 at 17:52
• I do have a question though, if the speakers aren't in parallel nor series, then they don't share the same voltage, so how do the filters do anything? They way i see it is that the speakers and their filters are parallel to the other speaker and it's filter, this way the same voltage gets to the filters so they can do what they do? – Keinicke Sep 23 '19 at 17:52

simulate this circuit – Schematic created using CircuitLab

Figure 1. A redrawn schematic.

The clue to untangling is that you have a common line running from the signal source to both so we'll make that our reference at the bottom of each circuit.

To understand what each circuit does just remember:

• A capacitor blocks DC completely (and low frequencies almost as much) but lets high frequencies through.
• An inductor blocks high frequencies but lets DC (and low frequencies) through.

From this we can quickly deduce that:

• The upper circuit will let low frequencies through L1 and any higher frequencies that do get through will tend to bypass the speaker via C1. It's a low-pass filter. Connect your big loudspeker here.
• The lower circuit will pass high frequencies and low filters will be blocked by C2 and shunted by L2. It's a high-pass filter. Connect your tweeter here.
• Thank you so much for the answer, both this illustration an the one above this one, helped me a lot, thanks. – Keinicke Sep 23 '19 at 17:37