If you have a 4 ohm speaker and you add a 4 ohm resister to the positive wire. Do you have an 8 ohm speaker?
Is impedence the same as resistence?
I have 2 Scosche HD4004 HD Speakers 4 oms 30 wat RMS. I also have a Lepai LP-2020TI amp, 15 watts per changle.
So, will this amp drive the 2 Speakers?
Speakers 4 ohms 30 watt RMS. So, if you are sending 15 watts at a medium volume. is that OK.
The Lepai LP-2020TI amp has a TPA3118 chip, according to the ad the chip does not have a heatsink. If I add a heatsink and increase the power from the 12v 3amp power supply to say a 19.5v 90watts on amp, will it heat up that chip? Will it increase the output wattage of the amp? How do you glue a heatsink on a chip?

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    I’m voting to close this question because it is about car audio installation not 'music performance or practise'. – Tetsujin Apr 23 '20 at 7:26
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    @Tetsujin - this could easily be a question based on a practice amp and adding speakers. No difference, really. – Tim Apr 23 '20 at 7:36
  • @Tim - but it isn't about practise amps, it's about specialist 12v systems used in cars. That is not where this stack's expertise lies. Next we'll be doing home cinema & Powerpoint screen projection tips… got to draw the line somewhere & this would appear to be right there. – Tetsujin Apr 23 '20 at 7:45
  • @Tetsujin - whilst you're right, there are more amps now using 12vdc, and people will want to add extra speakers, so the end product would be the same. If that clue was removed from the question, it would boil down to the same. – Tim Apr 23 '20 at 8:16
  • Gary, it's good practice here to ask one specific question. You are asking about a dozen here, many of which are contradictory. I would recommend first reading up on audio electronics and what 'resistance,' 'impedance,' and 'watts' ratings mean in this context. – Carl Witthoft Apr 23 '20 at 14:20

Welcome Gary. It sounds like you might like to turn your musical situation into a laboratory situation, as with a list of questions like this you'll either need to have a designer/ engineer redesign your power supply and amplifier or be willing to risk having your whole set-up go up in flames to get the answers you are looking for. As for your question about whether or not your amp in its current configuration will match up with your current speaker set-up, from the information you given us here, I'd say it'll match up okay. And as for the resistor wired in series with the speaker, well it would need to be a 15 watt resistor and it would just convert your output to heat, so I would be more inclined to find another speaker to wire in the circuit in place of that resistor, where the amp output would be converted into sound. Two concepts in electrical circuit operation are resistance, which is not frequency altered, it stays the same rating, which is pretty easy to understand. The other concept is called reactance, where the resistance can be altered depending of the operating frequency of the circuit. This is how a speaker acts in operation, where the resistance of the speaker changes in reaction to the frequency of the signal being presented to the speaker. This type of resistance is referred to as impedance. This is about as simple as I can think to explain it.

  • This fails to address the key question of static resistance vs dynamic impedance – Carl Witthoft Apr 23 '20 at 14:18
  • @Carl Witthoft- I apologize, But I simply didn't recognize that to be the key question. – skinny peacock Apr 23 '20 at 14:35

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