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View Full Version : Negative Ohms Reading On Speakers?



walkychalky
10-07-2008, 02:35 PM
i have some boston pro comps in my front and some mb quart comps inthe rear. my amp has been going into protect lately and i thought it was the amp but i switched it out n still have the same problem. i check the ohm loads with a dmm and for the front comps it reads between 2 and 3 ohms and the rear speakers get like a negative 10 ohms....are they blown or is something hooked up wrong? i didnt even know ohms could be negative. any help is appreciated....

P.S. when the speakers actually do play (they play for a lil b4 the amp goes into protect) they sound fine n i dont hear any distortion

mokedaddy
10-07-2008, 02:38 PM
Ohms arent negative. You have the positive and negative lead backwards. Did you zero out your leads before taking readings?

walkychalky
10-07-2008, 02:39 PM
Ohms arent negative. You have the positive and negative lead backwards. Did you zero out your leads before taking readings?

what do u mean by zero out my leads?

Innovative:Cory
10-07-2008, 02:39 PM
Doesn't matter if you test with the leads backwards on impedence....resistance is resistance

jco1385
10-07-2008, 02:40 PM
there is no negative resistance... think about it

Innovative:Cory
10-07-2008, 02:40 PM
are you taking measurements with the stereo playing? what kind of dmm are you using? is the battery fresh?

Buck
10-07-2008, 02:41 PM
Ohms arent negative. You have the positive and negative lead backwards. Did you zero out your leads before taking readings?

I don't think that matters, because it still reads the same. Whether switched up or not.

walkychalky
10-07-2008, 02:41 PM
there is no negative resistance... think about it

yah i realize it makes no sense...which is why i am baffled at the reading...

mokedaddy
10-07-2008, 02:41 PM
what do u mean by zero out my leads?

Touch them together until they read at or about 0ohms.


Doesn't matter if you test with the leads backwards on impedence....resistance is resistance

Obviously that is a given. He was asking why it was reading negative.

walkychalky
10-07-2008, 02:46 PM
are you taking measurements with the stereo playing? what kind of dmm are you using? is the battery fresh?

i think the stereo was on actually...i jus retested with it off and i got a reading of ~3.5 on each speaker....dumb mistake....i didnt know the stereo had to be off...my bad


however, my amp is still going into protect.....could my rcas be bad? is there a way to test them?

walkychalky
10-07-2008, 02:51 PM
anyone? :)

jco1385
10-07-2008, 02:52 PM
check grounds.

grimreper912003
10-07-2008, 02:54 PM
check grounds.

x2 or check wires for the speakers and make sure they arnt touching.

walkychalky
10-07-2008, 02:59 PM
my grounds look good....i have my 20.1 running off the same neg batt post n have no problems whatsoever.....speaker wires are not touching either.....this is sooooo frustrating :/

jco1385
10-07-2008, 03:01 PM
voltage at protected amp? RCAs shouldnt put an amp into protect, unless the volts are too high.

DMM the RCAs with the radio on and see what you get

Innovative:Cory
10-07-2008, 03:02 PM
Touch them together until they read at or about 0ohms.



Obviously that is a given. He was asking why it was reading negative.




Thats funny, I was directing that statement to you .....You where to one who told him he had the leads backwards..... it doesnt matter when measuring resistance!! You can put the positive lead of the dmm on the negative lead and still have the correct reading.

mokedaddy
10-07-2008, 03:03 PM
What amp and how are your speakers wired?

mokedaddy
10-07-2008, 03:04 PM
Thats funny, I was directing that statement to you .....You where to one who told him he had the leads backwards..... it doesnt matter when measuring resistance!! You can put the positive lead of the dmm on the negative lead and still have the correct reading.

I understand that. But again he asked why it was reading negative ohms. That is the answer. ;)

Innovative:Cory
10-07-2008, 03:06 PM
op, here is the easiest way to find out what is wrong....

disconnect rca's turn radio on.....does amp go into protect yes or no, if it doesn't then you have a problem in head unit or rca cable itself...

disconnect speaker leads, turn radio on....does amp go into protect yes or no, if it doesn't then you have a speaker problem....

disconnect both rca's and speaker leads, turn radio on, does amp go into protect? if it does measure voltage on power wire at the amp, and the remote turn on...


how many amps are you trying to turn on from your head unit, are you using a step up relay on the remote turn on?


If voltage is good on all wires then you have a bad amp!!

walkychalky
10-07-2008, 03:06 PM
voltage at protected amp? RCAs shouldnt put an amp into protect, unless the volts are too high.

DMM the RCAs with the radio on and see what you get


check for volts right??....ill do that right now

Innovative:Cory
10-07-2008, 03:07 PM
I understand that. But again he asked why it was reading negative ohms. That is the answer. ;)

YOU ARE WRONG!!

go grab a dmm and set to Ohm and measure a speaker with the leads backwards.....

then come and tell the class what you find...

Let me break this down for you.....

when you use a dmm and measure VOLTAGE...if you have the leads backwards you will display a Negative voltage reading...ie...(-12.6)

when you use a dmm to measure RESISTANCE ....it doesn not matter if you have the leads backwards or not...it will still read the same...i.e. (4) or (7.8) or whatever....

Understand?

Brian Owens
10-07-2008, 03:09 PM
Check from each speaker wire to DC chassis ground. Maybe you have a speaker wire that is pinched and shorted to ground.

mokedaddy
10-07-2008, 03:11 PM
YOU ARE WRONG!!

go grab a dmm and set to Ohm and measure a speaker with the leads backwards.....

then come and tell the class what you find...

Let me break this down for you.....

when you use a dmm and measure VOLTAGE...if you have the leads backwards you will display a Negative voltage reading...ie...(-12.6)

when you use a dmm to measure RESISTANCE ....it doesn not matter if you have the leads backwards or not...it will still read the same...i.e. (4) or (7.8) or whatever....

Understand?

Than explain to me why it was reading negative then?

mokedaddy
10-07-2008, 03:13 PM
op, here is the easiest way to find out what is wrong....

disconnect rca's turn radio on.....does amp go into protect yes or no, if it doesn't then you have a problem in head unit or rca cable itself...

disconnect speaker leads, turn radio on....does amp go into protect yes or no, if it doesn't then you have a speaker problem....

disconnect both rca's and speaker leads, turn radio on, does amp go into protect? if it does measure voltage on power wire at the amp, and the remote turn on...


how many amps are you trying to turn on from your head unit, are you using a step up relay on the remote turn on?


If voltage is good on all wires then you have a bad amp!!

Could also be a speaker wired grounding out or trying to wire the amp too low.

Innovative:Cory
10-07-2008, 03:19 PM
Than explain to me why it was reading negative then?

If you are paying attention, you will notice I asked if he was taking his readings with the radio on.....

He said he was.....

That was the reason his reading was wrong.

He was getting a measurement from the amp itself... More than likely since there is something wrong with the amp, me may have gotten a voltage measurement instead. That would just depend on the type of meter used. Some will automatically transfer from Impedence to Voltage with you having to make an adjustment.

mokedaddy
10-07-2008, 03:26 PM
He also stated that he switched out amps and was still having the problem. Thus meaning it is probably a wiring or voltage problem.

walkychalky
10-07-2008, 03:32 PM
so i ran the amp for a while without rca's n it didnt go into protect....i jus hooked up the first 2 channel RCA's so imma give it a few min n see if it goes into protect b4 i hook the other 2 up

i measured volts at the amp....its about 10.9 DC and 23 AC...same as my 20.1

i have 2 amps turning on with the headunit....i jus have the remote start daisy chained to both amps

mokedaddy
10-07-2008, 03:34 PM
so i ran the amp for a while without rca's n it didnt go into protect....i jus hooked up the first 2 channel RCA's so imma give it a few min n see if it goes into protect b4 i hook the other 2 up

i measured volts at the amp....its about 10.9 DC and 23 AC...same as my 20.1

i have 2 amps turning on with the headunit....i jus have the remote start daisy chained to both amps

10.9 v is pretty low. That very well could be your problem.

jco1385
10-07-2008, 03:34 PM
you only have 10v at the amp? sounds like the problem

walkychalky
10-07-2008, 03:35 PM
you only have 10v at the amp? sounds like the problem

what should i have?

mokedaddy
10-07-2008, 03:36 PM
what should i have?

at least 12.0

jco1385
10-07-2008, 03:36 PM
12v+

car running should be at least over 13v. but off should be 12.*v

jco1385
10-07-2008, 03:37 PM
well me and moke are on teh spot

walkychalky
10-07-2008, 03:40 PM
what should i have?

nvm...dumb question....voltage at batt is about 12.5....and then voltage at the distro block which is like a foot away drops to 10.9 ...wtf is this all about??? im sooo confused

jco1385
10-07-2008, 03:41 PM
corroded wire?

what distro?

mokedaddy
10-07-2008, 03:42 PM
nvm...dumb question....voltage at batt is about 12.5....and then voltage at the distro block which is like a foot away drops to 10.9

Sounds like you have loose connection, bad connection, loose fuse, etc... Pics?

walkychalky
10-07-2008, 03:43 PM
corroded wire?

what distro?

i have a optima yellow top up front....ran to 2 kinetik 2400's in the back....which are ran to a PG distro block for both pos n ground.....at the rear batts i get ~12.5 with car off.....then at the distro it drops to 10.9 and it is this same reading at the amps

i'd take pics but i have no digi camera....im going to mull over the connections again to see if i notice anything that looks loose

jco1385
10-07-2008, 03:46 PM
what is between the battery and the distro? wire? is it loose or corroded?

this is where the problem is :fyi:

shaneb
10-07-2008, 03:50 PM
what should i have?

Check the voltage at the batter, one post to the other,
your voltage and the power and ground terminal on the amp should be the same.
no higher, no lower.
i.e my amp is 12.5, my battery is 12.5 voltss...
this probably means you have a bad ground, a way to check that is to run a lead from the ground post on your battery and put your neg lead from your dmm on it, and put the pos lead on the pos terminal on the amp, if it reads 12.5 or whatever your battery is, then you kjnow youave a ground problem.

Edit: I can't type fast enough....

jco1385
10-07-2008, 03:51 PM
Check the voltage at the batter, one post to the other,
your voltage and the power and ground terminal on the amp should be the same.
no higher, no lower.
i.e my amp is 12.5, my battery is 12.5 voltss...
this probably means you have a bad ground, a way to check that is to run a lead from the ground post on your battery and put your neg lead from your dmm on it, and put the pos lead on the pos terminal on the amp, if it reads 12.5 or whatever your battery is, then you kjnow youave a ground problem.

Edit: I can't type fast enough....

this is true as well

walkychalky
10-07-2008, 03:57 PM
Check the voltage at the batter, one post to the other,
your voltage and the power and ground terminal on the amp should be the same.
no higher, no lower.
i.e my amp is 12.5, my battery is 12.5 voltss...
this probably means you have a bad ground, a way to check that is to run a lead from the ground post on your battery and put your neg lead from your dmm on it, and put the pos lead on the pos terminal on the amp, if it reads 12.5 or whatever your battery is, then you kjnow youave a ground problem.

Edit: I can't type fast enough....


so i did what u said and i got the reading for my batt (12.5).....then i did the reverse of that....put pos lead at batt and neg lead at amp and i got the reading for my batt (12.5)....what does this mean?

walkychalky
10-07-2008, 04:03 PM
???

mokedaddy
10-07-2008, 04:06 PM
so i did what u said and i got the reading for my batt (12.5).....then i did the reverse of that....put pos lead at batt and neg lead at amp and i got the reading for my batt (12.5)....what does this mean?

It means your ground is solid. Since its grounded directly to the battery that shouldnt have been a problem anyways. Check your connections. Like stated you have a loose or corroded connection, most likely at the d-block.

jco1385
10-07-2008, 04:07 PM
so, pos at amp with neg at battery is 12.5

and neg at amp, pos at battery is 12.5 also?

walkychalky
10-07-2008, 04:08 PM
It means your ground is solid. Since its grounded directly to the battery that shouldnt have been a problem anyways. Check your connections. Like stated you have a loose or corroded connection, most likely at the d-block.


if i put the leads on the d-block itself i get the low 10.9 reading....does this mean that the connection from the batt to the d-block is the likely culprit?

walkychalky
10-07-2008, 04:08 PM
so, pos at amp with neg at battery is 12.5

and neg at amp, pos at battery is 12.5 also?

correct

jco1385
10-07-2008, 04:08 PM
run straight to the amp, take out the block and try it.

mokedaddy
10-07-2008, 04:10 PM
if i put the leads on the d-block itself i get the low 10.9 reading....does this mean that the connection from the batt to the d-block is the likely culprit?

Yes. Is it 10.9 at the input and output of the d-block? If it is at both, its most likely the connection between the wire and the input of the d-block. Also could possible be at the battery term as well but that is less likely of a possibility.

walkychalky
10-07-2008, 04:11 PM
run straight to the amp, take out the block and try it.

ill try that next....unfortunately i have to be to work in less than an hour or id do it right now....jus one quick question tho b4 i go......since the 20.1 is getting the same voltage but not going into protect does that just mean that the other amp (cadence) is just more sensitive to the low voltage input?

thanks for everyones help too btw

jco1385
10-07-2008, 04:11 PM
but if the block is the bottleneck, how is he getting 12.5 with the pos at the amp, neg at battery?

walkychalky
10-07-2008, 04:12 PM
Yes. Is it 10.9 at the input and output of the d-block? If it is at both, its most likely the connection between the wire and the input of the d-block. Also could possible be at the battery term as well but that is less likely of a possibility.

yes its 10.9 at both

jco1385
10-07-2008, 04:12 PM
yes its 10.9 at both

how is this true? i am :confused: now

mokedaddy
10-07-2008, 04:14 PM
but if the block is the bottleneck, how is he getting 12.5 with the pos at the amp, neg at battery?

You are reading it backwards. :)

Its 12.9 pos on batt and neg at amp. Amp is grounded to batt so it makes sense.

mokedaddy
10-07-2008, 04:15 PM
ill try that next....unfortunately i have to be to work in less than an hour or id do it right now....jus one quick question tho b4 i go......since the 20.1 is getting the same voltage but not going into protect does that just mean that the other amp (cadence) is just more sensitive to the low voltage input?

thanks for everyones help too btw

Yes. the 20.1 is pretty bullet proof, but I wouldnt recommend doing it for long periods of time.

jco1385
10-07-2008, 04:16 PM
You are reading it backwards. :)

Its 12.9 pos on batt and neg at amp. Amp is grounded to batt so it makes sense.

read the first post on this page ;)

i'm lost because of it :fyi:

walkychalky
10-07-2008, 04:18 PM
so this is gonna sound weitrd but i jus went out n retested all connections....im now getting 12.3 everywhere....wtf is up with this?? maybe i bumped something n made it more secure again??

jco1385
10-07-2008, 04:19 PM
so this is gonna sound weitrd but i jus went out n retested all connections....im now getting 12.3 everywhere....wtf is up with this?? maybe i bumped something n made it more secure again??

something is loose somewhere. check everything.

mokedaddy
10-07-2008, 04:20 PM
read the first post on this page ;)

i'm lost because of it :fyi:

I see. I misread your post, but I that is what I took his post to mean.

And to the OP, yes it means it it/was a loose connection. Make sure they are all tight.

Buck
10-07-2008, 04:20 PM
Listen to jco :fyi:

jco1385
10-07-2008, 04:22 PM
Listen to jco :fyi:

:rolleyes:

edit: you speak troofs

walkychalky
10-07-2008, 04:27 PM
thanks for all the help guys....everything is reading pretty well i think....i get 12.3 @ the batt and then 12.1 at the amp right now ( i figure .2 drop is somewhat normal)...when i get a chance (probably tomorrow) im going to resecure all my connections

jco1385
10-07-2008, 04:28 PM
i would not turn it up too much, incase some dumb **** happens and kills everything

walkychalky
10-07-2008, 04:31 PM
i would not turn it up too much, incase some dumb **** happens and kills everything

yah i hear ya....i jus might not even play it until i redo my connections....im late for work cause of this tho lol.....thanks again for ur help

jco1385
10-07-2008, 04:32 PM
it's why i am here (other than getting banned)

let us know what was loose.

jco1385
10-08-2008, 05:14 PM
so what was it??

thch
10-08-2008, 09:04 PM
to the first post:
the most likely causes are:
1.) speaker still connected to amplifier. In this case the amplifier will force a voltage onto the speaker, and you'll measure whatever the DMM thinks that is.
2.) someone pressed on the cone. In this case, the back-emf will force a changing voltage on the coil, similar to how a microphone works. This will be measured as all sorts of random things.
3.) meter was calibrated with a large offset. there may be a "zero" button to allow you to calibrate the meter. connect the two leads together and press the "zero/calibrate" button.
4.) faulty meter.

from a quick glance, i'm guessing #3.

Brian Owens
10-09-2008, 10:32 AM
He already said it read negative because the stereo was on. Measured fine with it off.


i think the stereo was on actually...i jus retested with it off and i got a reading of ~3.5 on each speaker....dumb mistake....i didnt know the stereo had to be off...my bad


The question was why was the amp shutting off???

jco1385
10-09-2008, 11:10 AM
He already said it read negative because the stereo was on. Measured fine with it off.



The question was why was the amp shutting off???

it was low voltage. something is/was loose.