Hi,
Wirewound resistors working at their power rating can get seriously hot up to the point of unsoldering from the bord. These are rugged devices and resistor can sort of survive short term overloads but not necessarily parts around it.
So if there are any doubts about power rating limits it's good idea to mound the resistor to a heat sink using a thermal compound.
Regards
Wirewound resistors working at their power rating can get seriously hot up to the point of unsoldering from the bord. These are rugged devices and resistor can sort of survive short term overloads but not necessarily parts around it.
So if there are any doubts about power rating limits it's good idea to mound the resistor to a heat sink using a thermal compound.
Regards
The total resistance of the resistor(s) and speaker in parallel will be less than the smallest value of either. If your woofer is 4 ohm, and you add 4 ohm parallel, the total resistance will become 2 ohms. Now, if your amp can deliver 25 watts into 8 ohms, it will try to deliver 100 watts into 2 ohms. 50 watts into the woofer and 50 watts into the resistor. This effort will fry the speaker/resistor, or the amp might go into overcurrent protection mode, if that is provided, or else self destruction mode.
The speaker is still 8ohm and probably nothing will happen to it. Only the resistor and amplifier will suffer.
The amplifier won't tolerate 4ohms. It's actually very close. The popping sound ceases if I block the port. Added the 4ohm resistor & all is well. The ceramic cement resistor becomes very warm (50 degrees-ish) when driven at full power for extended periods. I'm guessing the amp would be happier with 6ohms, no?No, of course, now neither the resistors nor the amplifier will survive that test.
It's just not clear to me what the purpose of this intention is, to burn the amplifier?
It's very cheap, assembled from components I have laying around.
So, to be clear, the amplifier is designed for an 8 ohm load? if so, connecting a 4 ohm driver will result in the amp trying to deliver a higher output current than it was designed for. And connecting a resistor in parallel will make things worse.
If you have a second 4 ohm driver, you can connect them in series.
If you have a second 4 ohm driver, you can connect them in series.
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"So, to be clear, the amplifier is designed for an 8 ohm load? if so, connecting a 4 ohm driver will result in the amp trying to deliver a higher output current than it was designed for. And connecting a resistor in parallel will make things worse.
If you have a second 4 ohm driver, you can connect them in series."
This is getting confusing.
Currently there is a 4ohm driver and a 4ohm resistor in series - 8ohms, right?
I'm proposing 2 x 4ohm resistors in parallel (2ohms) in series with the 4 ohm driver - 6ohms.
Is that correct?
If you have a second 4 ohm driver, you can connect them in series."
This is getting confusing.
Currently there is a 4ohm driver and a 4ohm resistor in series - 8ohms, right?
I'm proposing 2 x 4ohm resistors in parallel (2ohms) in series with the 4 ohm driver - 6ohms.
Is that correct?
Ah, now I get it. In the first post you said the 4 ohm resistor is in parallel with the woofer, but they are actually in series.
That's right. The amp will try to deliver 37,5 watts into these 6 ohms. If it can, that means 25 watts into the speaker and 12.5 watts into the resistors. So that is 6.25 watts per resistor.
You said in parallel. Connect whatever resistors you want in series, you will only spoil the sound. That 4 ohm resistor in front of the bass driver reduces the damping factor of the amplifier to 1 (one).
If the amp isn't designed to run at 4ohm, just don't drive it too hard and you'll be fine with 4 ohm speakers. Almost any amplifer can run at 4ohm load (and below) if not overpowered. Or look for 8ohm speakers.
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You also have to consider the impedance curve of the driver, which can dip well below the "rated" average impedance. If the signal fed into the amp has most of its frequency range focused around the driver's min impedance dip, the amp could be driving less than a 3 ohm load in that operating range.
On the off-chance that someone would actually want to get a clue of what they are doing.
https://www.electronics-tutorials.ws/resistor/res_5.html
Jan
https://www.electronics-tutorials.ws/resistor/res_5.html
Jan
"If the amp isn't designed to run at 4ohm, just don't drive it too hard and you'll be fine with 4 ohm speakers. Almost any amplifer can run at 4ohm load (and below) if not overpowered. Or look for 8ohm speakers."
I believe the chip is a TDA1558Q with two channels bridged. The bridged (sub) channel has no tolerance for 4 ohms even at low volumes.
I believe the chip is a TDA1558Q with two channels bridged. The bridged (sub) channel has no tolerance for 4 ohms even at low volumes.