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putting a resistor in series with a speaker to increase the impedence
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Adhith:
hello everyone...
I'm building a speaker setup using the 25w+25w amplifier board based on the class D amplifier IC  TDA7492P. The amp board also has an inbuilt Bluetooth receiver module and also I'm using a 4ohm driver at the output. The description about the amp board says that it is ideal for 8 ohm drivers even though it could work with 6 and 4 ohms without problem. Since 4 ohm was on the borders of limit and since Im powering the amp board with a 4S1P battery pack I'm thinking of using a higher ohm driver to reduce the total power consumption.
So what my question is, is there any way to increase the impedence with out changing the  4ohm driver that i'm currently using. does a 4 ohm resistor in series with the driver work?? if so what should be the wattage rating of it??
HB9EVI:
you can add a resistor, but you can also just keep the output level low enough to not exceed the rating of the amp
JS:
If you add a resistor you will just drop on efficency and peak power capability. Also damping factor will drop dramatically.

With 4S you have about 15V nominal, into the 4Ω it's baerly 25W rms if the tpa goes close to rails, as it should, with music the average power consumption will be much lower, like under 10W with a reasonable THD. But. You could get 800W PMPO if you want to sell it.

Adding the resistor makes no sense, higher impedance coils makes better response and efficency for higher voltage situations, but adding a resistor in series only makes those numbers worse.

JS

Adhith:

--- Quote from: HB9EVI on July 24, 2018, 05:06:17 pm ---you can add a resistor, but you can also just keep the output level low enough to not exceed the rating of the amp

--- End quote ---
The reason that I'm planning to higher the impedence is because, during startup the amp instantly consumes a peak current of 1.8A for 2 seconds and then lowers the current draw to a very low level. This peak current is making the problem of the bms to shut down(maybe it was kind of confusing as a short due to the high current draw of 1.8A). So the board is not at all even getting started up at the first place since  the bms turns off before it.
But if the drivers are disconnected during startup and connected after the first two seconds of startup, then there is no problem and everything works smoothly.
This board does have this thing of drawing too much current at the start up since i have  found some articles about the same on internet.
Adhith:

--- Quote from: JS on July 24, 2018, 05:32:51 pm ---If you add a resistor you will just drop on efficency and peak power capability. Also damping factor will drop dramatically.

With 4S you have about 15V nominal, into the 4Ω it's baerly 25W rms if the tpa goes close to rails, as it should, with music the average power consumption will be much lower, like under 10W with a reasonable THD. But. You could get 800W PMPO if you want to sell it.

Adding the resistor makes no sense, higher impedance coils makes better response and efficency for higher voltage situations, but adding a resistor in series only makes those numbers worse.

JS

--- End quote ---
Thank you very much for your reply. So I understood that adding resistor is a bad choice. So are you saying that the better option is finding another driver of some higher impedance like 8 ohm??
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