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Discussion Starter #1
I got a friend who has 3 subs that he cant find information on, he says they were CDT test models, although I couldnt verify that

How do we go about figuring the ohm load for each coil?

Thanks guys
 

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Is the meter analog (sweep needle) or digital (numbers displayed) ?. If it's analog them put the meter scale (rotary switch) on the lowest ohms setting and then touch both test leads off of it together. The needle should then swing to 0 ohms. If not see if there is a zeroing adjustment on the meter to get the needle to be at 0 ohms. If it still cannot be adjusted or made to read 0 ohms then replace the battery in it and try it again.
If it's a digital model the rotary knob gets set to the lowest ohm scale and you can check by touching both leads together but it should read 0.00 ohms or possibly 0.05 or so which is fine.

Now take one test lead to one terminal on the speaker and the other test lead to the second terminal and note the meter reading. If it's a 4 ohm speaker it may read 3.4 to 4.5 ohms which is fine. All you are reading is DC resistance not AC resistance. If it's a 2 ohm speaker it may read 1.7 to 2.4 ohms.
When measuring do not touch the speaker cone or have the speaker in a windy area or in a loud background room because if the speaker cone moves you will get a fluctuating ohms reading.
Once you get the measurements then you can figure out the wiring so the amplifier can put out it's maximum power without being too low of a load.

On a side note you can lossely pinch a test lead with one in each hand and your body will be of so much resistance. Now pinch your fingers real hard on the test leads and watch the resistance go down.

You will find out later after music has been played through the subs at a high volume the resistance will increase due to the voice coils heating up and the systems volume may go down a tad.

Jim
 

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Discussion Starter #3
Originally posted by Custom Jim@Aug 15 2006, 03:53 PM~5974557
Is the meter analog (sweep needle) or digital (numbers displayed) ?. If it's analog them put the meter scale (rotary switch) on the lowest ohms setting and then touch both test leads off of it together. The needle should then swing to 0 ohms. If not see if there is a zeroing adjustment on the meter to get the needle to be at 0 ohms. If it still cannot be adjusted or made to read 0 ohms then replace the battery in it and try it again.
If it's a digital model the rotary knob gets set to the lowest ohm scale and you can check by touching both leads together but it should read 0.00 ohms or possibly 0.05 or so which is fine.

Now take one test lead to one terminal on the speaker and the other test lead to the second terminal and note the meter reading. If it's a 4 ohm speaker it may read 3.4 to 4.5 ohms which is fine. All you are reading is DC resistance not AC resistance. If it's a 2 ohm speaker it may read 1.7 to 2.4 ohms.
When measuring do not touch the speaker cone or have the speaker in a windy area or in a loud background room because if the speaker cone moves you will get a fluctuating ohms reading.
Once you get the measurements then you can figure out the wiring so the amplifier can put out it's maximum power without being too low of a load.

On a side note you can lossely pinch a test lead with one in each hand and your body will be of so much resistance. Now pinch your fingers real hard on the test leads and watch the resistance go down.

You will find out later after music has been played through the subs at a high volume the resistance will increase due to the voice coils heating up and the systems volume may go down a tad.

Jim

Wow I really appreciate the example and help! You have helped a ton! My multimeter (analog) only reads in 1k ohm scale, so we gotta pick up another.

Thanks!
 
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