$@#$#$% Help?
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From: Yuba City, California
Originally Posted by WLAURENT,Mar 12 2006, 06:17 PM
Must be something wrong on the sub or you are shorting it when you wire it - you read 0.2 with just the probes, same thing you are reading when you go parallel.
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Originally Posted by Haulin' S,Mar 12 2006, 10:43 AM
You've got everything right, but I am running only one sub. More comments to come...
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From: Secret Lair
Originally Posted by jwa4378,Mar 14 2006, 06:54 PM
^ He shouldnt have to....the amp is designed to handle a 2-ohm load. By upping the impediance, he will be lowering the output of the amp.
John
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From: Tallahassee, FL
He never actually got a reading of 1-ohm. Sebring Demon was saying what he should be getting if he was running 2 subs, which he is not.
He is running a single DVC 4-ohm sub. If the coils are not screwed up, he should get a reading of ~2-ohms when wired in parallel.....I think he got .2 (or some rediculously low number like that).
He got a reading of 3.3 / coil, which does not support the .2 reading when wired in parallel (it should read closer to 1.65 when wired in parallel, if they are indeed 3.3-ohms per coil). If they are 3.3-ohms each, that would read over 6-ohms when wired in series....which would not be efficient at all and would sound bad on a mono amp.
John
He is running a single DVC 4-ohm sub. If the coils are not screwed up, he should get a reading of ~2-ohms when wired in parallel.....I think he got .2 (or some rediculously low number like that).
He got a reading of 3.3 / coil, which does not support the .2 reading when wired in parallel (it should read closer to 1.65 when wired in parallel, if they are indeed 3.3-ohms per coil). If they are 3.3-ohms each, that would read over 6-ohms when wired in series....which would not be efficient at all and would sound bad on a mono amp.
John
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Ok folks. My father's an electrician. Has been for about 30 years. Here's what he says about why an ohm meter does't tell us ANYHTING about what the sub is doing...
"If you were to take a coil of wire as found in a speaker and stretch it out as one long run of wire the 'resistance' would be very low. Think it through..it IS just a long length of wire and wire is a good conductor (or..a LOUSY resistor).
If we were to connect a battery (DC) across the ends of the wire it would ALMOST act as a resistor in series. This is because there IS a slight resistance to any wire usually stated as 'ohms per foot'.
Whether we coil up the wire or leave it laid out in a straight line....THAT is what you read when you hook an ohmeter across a pair of speaker contacts. That is 'RESISTANCE'.
The value , even though it is given as 'ohms', given for a typical speaker is an IMPEDANCE value, NOT a resistance value.
Think back to science class...any time we run a wire through a magnetic field we generate an electron flow in the wire. That electron flow creates a magnetic field around that wire. It ALSO works in reverse...we can run the magnetic field across the wire and the result will be the same.....a magnetic field will be created around the wire.
Now we have a coil of wire with a source of power that is changing rapidly. The magnetic field around this coil is expanding and collapsing at a high frequency. The lines of flux being created are cutting across the wires of the coil as they expand and contract. WE'VE MADE A LITTLE GENERATOR!!!! NEAT!!!
There's a funny little fact though....due to the time that it takes for the magnetic field to build and collapse there's a DELAY in when we're MAKING electricity in realtion to when we're USING electricity. It seems that for every pulse (AC cycle) of power being consumed we SEND BACK a little pulse of juice. That pulse we send back actually SUBTRACTS from the power pulse that initially was sent. This makes it LOOK LIKE a resistance.....BUT IT'S NOT!
A resistance actually fights against the flow of electrons in a conductor......an impedance LOOKS the same...but it is really a 'counter flow' to the flow of electrons. Thus the term 'impedance' to differentiate between the two. Resistance is the same whether being supplied by AC or DC. Impedance only reacts to AC.
When wire is wound into a coil it has a unique ability to form a counter flow to any 'change' of power placed across it. That 'change' of power is another way of me saying 'AC power'. HMmmmm...speakers work due to varying the voltage potential across them??? Varying voltage=AC voltage.....Your speaker is really a coil of wire..placed in a magnetic field..and mechanically hooked to a diaphram that vibrates the air resulting in audible sound.
You MAY have at sometime heard the term 'counter EMF'. That refers to the 'counter' electromotive force induced in an AC circuit due to the presence of a inductor (coil of wire). The sam 'impedance' term applys to ANY coill of wire..like the winding of a motor in your refrigerator. For every 'cycle' (1/60th of a second) of electricity that the power plant sends out.....every coil of wire in the system gives us a little push back........refered to as 'power factor'. It costs the power company a BUNDLE to overcome the effects of those little pushs.....
Your speaker is doing exactly the same thing to your amplifier. Thus..if you can match the impedance of the amplifier design to the impedance of your speaker you will get maximum power transfer and less heating of the amplifier as it tries to do its job.
An ohmeter can only measure static resistance..there is no meter to measure impedance..it has to be calculated from the characteristics of the individual circuit.
Makes perfect sense to me!!!!!
PHEW!!!!! Only SIMPLE questions from now on....yer old Pas gettin too damned old fer this stuff..
Love,
PA
This would apply if either AC or DC power was to be used as a source.
One more thing.....resistance in a circuit lowers the voltage.
Impedance in a circuit lowers the voltage.
Even though they do it in different ways the result is the same.
Thus.......the commonality of the term 'ohms' to resistance and impedance..
Pa"
"If you were to take a coil of wire as found in a speaker and stretch it out as one long run of wire the 'resistance' would be very low. Think it through..it IS just a long length of wire and wire is a good conductor (or..a LOUSY resistor).
If we were to connect a battery (DC) across the ends of the wire it would ALMOST act as a resistor in series. This is because there IS a slight resistance to any wire usually stated as 'ohms per foot'.
Whether we coil up the wire or leave it laid out in a straight line....THAT is what you read when you hook an ohmeter across a pair of speaker contacts. That is 'RESISTANCE'.
The value , even though it is given as 'ohms', given for a typical speaker is an IMPEDANCE value, NOT a resistance value.
Think back to science class...any time we run a wire through a magnetic field we generate an electron flow in the wire. That electron flow creates a magnetic field around that wire. It ALSO works in reverse...we can run the magnetic field across the wire and the result will be the same.....a magnetic field will be created around the wire.
Now we have a coil of wire with a source of power that is changing rapidly. The magnetic field around this coil is expanding and collapsing at a high frequency. The lines of flux being created are cutting across the wires of the coil as they expand and contract. WE'VE MADE A LITTLE GENERATOR!!!! NEAT!!!
There's a funny little fact though....due to the time that it takes for the magnetic field to build and collapse there's a DELAY in when we're MAKING electricity in realtion to when we're USING electricity. It seems that for every pulse (AC cycle) of power being consumed we SEND BACK a little pulse of juice. That pulse we send back actually SUBTRACTS from the power pulse that initially was sent. This makes it LOOK LIKE a resistance.....BUT IT'S NOT!
A resistance actually fights against the flow of electrons in a conductor......an impedance LOOKS the same...but it is really a 'counter flow' to the flow of electrons. Thus the term 'impedance' to differentiate between the two. Resistance is the same whether being supplied by AC or DC. Impedance only reacts to AC.
When wire is wound into a coil it has a unique ability to form a counter flow to any 'change' of power placed across it. That 'change' of power is another way of me saying 'AC power'. HMmmmm...speakers work due to varying the voltage potential across them??? Varying voltage=AC voltage.....Your speaker is really a coil of wire..placed in a magnetic field..and mechanically hooked to a diaphram that vibrates the air resulting in audible sound.
You MAY have at sometime heard the term 'counter EMF'. That refers to the 'counter' electromotive force induced in an AC circuit due to the presence of a inductor (coil of wire). The sam 'impedance' term applys to ANY coill of wire..like the winding of a motor in your refrigerator. For every 'cycle' (1/60th of a second) of electricity that the power plant sends out.....every coil of wire in the system gives us a little push back........refered to as 'power factor'. It costs the power company a BUNDLE to overcome the effects of those little pushs.....
Your speaker is doing exactly the same thing to your amplifier. Thus..if you can match the impedance of the amplifier design to the impedance of your speaker you will get maximum power transfer and less heating of the amplifier as it tries to do its job.
An ohmeter can only measure static resistance..there is no meter to measure impedance..it has to be calculated from the characteristics of the individual circuit.
Makes perfect sense to me!!!!!
PHEW!!!!! Only SIMPLE questions from now on....yer old Pas gettin too damned old fer this stuff..
Love,
PA
This would apply if either AC or DC power was to be used as a source.
One more thing.....resistance in a circuit lowers the voltage.
Impedance in a circuit lowers the voltage.
Even though they do it in different ways the result is the same.
Thus.......the commonality of the term 'ohms' to resistance and impedance..
Pa"
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From: Mesa
Yes and no.
Your father is correct that the impedance/resistance on a speaker is not a measurement of a resistor but rather an inductior. However, you can measure it with a DMM and get a ball park measure to determine if the coil is shorted or not. This works well for determining if the coils in a DVC sub are balanced. You are not measuring a true resistance because the resistance of an inductive load changes with frequency.
Another thing to consider is that wire is just a very low impedance resistor. For example: If you take 40 feet of 30 gauge copper wire, the effective resistance of that wire is about 4 ohms. If used that wire to run a signal to a 4 ohms speaker you would be dropping 50% of voltage (and effective power) across the wire.
Still no reason you are measuring 3.3 ohms on each coil and then measuring 0.2 when you put them in parallel. If your DMM shows 0.2 ohms on the leads then you should be measuring 1.75 ohms when you put your coils in parallel (taking the 0.2 baseline of your DMM into consideration).
Heres a cool little tool you can use to calculate resistance of wiring:
http://www.cirris.com/testing/resistance/wire.html
Your father is correct that the impedance/resistance on a speaker is not a measurement of a resistor but rather an inductior. However, you can measure it with a DMM and get a ball park measure to determine if the coil is shorted or not. This works well for determining if the coils in a DVC sub are balanced. You are not measuring a true resistance because the resistance of an inductive load changes with frequency.
Another thing to consider is that wire is just a very low impedance resistor. For example: If you take 40 feet of 30 gauge copper wire, the effective resistance of that wire is about 4 ohms. If used that wire to run a signal to a 4 ohms speaker you would be dropping 50% of voltage (and effective power) across the wire.
Still no reason you are measuring 3.3 ohms on each coil and then measuring 0.2 when you put them in parallel. If your DMM shows 0.2 ohms on the leads then you should be measuring 1.75 ohms when you put your coils in parallel (taking the 0.2 baseline of your DMM into consideration).
Heres a cool little tool you can use to calculate resistance of wiring:
http://www.cirris.com/testing/resistance/wire.html
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From: Yuba City, California
Originally Posted by WLAURENT,Mar 16 2006, 08:45 PM
Yes and no.
Your father is correct that the impedance/resistance on a speaker is not a measurement of a resistor but rather an inductior. However, you can measure it with a DMM and get a ball park measure to determine if the coil is shorted or not. This works well for determining if the coils in a DVC sub are balanced. You are not measuring a true resistance because the resistance of an inductive load changes with frequency.
Another thing to consider is that wire is just a very low impedance resistor. For example: If you take 40 feet of 30 gauge copper wire, the effective resistance of that wire is about 4 ohms. If used that wire to run a signal to a 4 ohms speaker you would be dropping 50% of voltage (and effective power) across the wire.
Still no reason you are measuring 3.3 ohms on each coil and then measuring 0.2 when you put them in parallel. If your DMM shows 0.2 ohms on the leads then you should be measuring 1.75 ohms when you put your coils in parallel (taking the 0.2 baseline of your DMM into consideration).
Heres a cool little tool you can use to calculate resistance of wiring:
http://www.cirris.com/testing/resistance/wire.html
Your father is correct that the impedance/resistance on a speaker is not a measurement of a resistor but rather an inductior. However, you can measure it with a DMM and get a ball park measure to determine if the coil is shorted or not. This works well for determining if the coils in a DVC sub are balanced. You are not measuring a true resistance because the resistance of an inductive load changes with frequency.
Another thing to consider is that wire is just a very low impedance resistor. For example: If you take 40 feet of 30 gauge copper wire, the effective resistance of that wire is about 4 ohms. If used that wire to run a signal to a 4 ohms speaker you would be dropping 50% of voltage (and effective power) across the wire.
Still no reason you are measuring 3.3 ohms on each coil and then measuring 0.2 when you put them in parallel. If your DMM shows 0.2 ohms on the leads then you should be measuring 1.75 ohms when you put your coils in parallel (taking the 0.2 baseline of your DMM into consideration).
Heres a cool little tool you can use to calculate resistance of wiring:
http://www.cirris.com/testing/resistance/wire.html