Do resistor add impedance to an OB speaker

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goodguys

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Do resistor add impedance to an OB speaker
« on: 20 Jan 2024, 07:34 am »
Hi Thanks for reading. I have a 4 ohm sub with a dual voice coil. With both coils connected in parallel the nominal impedance is 2 ohms and the minimum impedance is one ohm.
My amp can handle a 4 ohm nominal speaker, so can probably go down to a minimum impedance of 2 ohms.
Can i place a high power one or two ohm resistor in series with the driver to make sure the impedance is not too low which may damage the amp
I was told years ago that resistors add resistance and not impedance, so do not raise the total impedance the amplifier sees, what do you think

mix4fix

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Re: Do resistor add impedance to an OB speaker
« Reply #1 on: 20 Jan 2024, 08:00 am »
What amplifier and what subwoofer do you have?

Is your subwoofer dual 4 ohm (8 ohm series/2 ohm mono) or dual 2 ohm (4 ohm series/1 ohm mono)?

GeorgeAb

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Re: Do resistor add impedance to an OB speaker
« Reply #2 on: 20 Jan 2024, 09:53 pm »
Impedence is a combination of the resistance, inductance and capicitance. So yes a 2 ohm resister will add 2 ohms of resistance in addion to the capcitors Xc and Inductance Xc (resistance that changes as a function of frequency(simpler explanation then next one)) (resistance at 90° phase shift (inductance and capitance being each 90° (in opposite directions) from resistance). So yes you can add a 2 ohm resistor in series (inline not across the + and - of sub) with the subwoofer and increase the load the amp sees, while attenuating the signal by half so you will have to provide more signal to get same SPL. Will have to be a high wattage resistor. 

You may look into a L pad. It is designed to do just what you are looking for of attempting to maintain a continuous 8 ohm load while attenuating the signal making it adjustable and can be found in 50 or 100W (wattage (power handling)). They are $15 at parts express.
 https://www.parts-express.com/speaker-components/crossover-components/speaker-l-pads I explained how they worked in a post just a while back. Will insert if I can find. Here it is: https://www.audiocircle.com/index.php?topic=187757.msg1968423#msg1968423

mix4fix

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Re: Do resistor add impedance to an OB speaker
« Reply #3 on: 20 Jan 2024, 10:05 pm »
Let's wait until we find out what amplifier(s). subwoofer(s), and speakers this person has before we start ordering crap we may not need.