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anwaypasible 25th May 2012 07:13 AM

resistor confusion
 
i got some speakers from the junkyard.
i went with these speakers from an infinity system because they had a seperate tweeter.
when i got them home, i learned they were 2ohms (which is kinda what i thought was gonna happen)

my first thought was to go to radioshack and get some 2ohm resistors to increase the load to 4ohms.

later on,
i learned about people using dummy loads to benchmark amplifiers.
what they did to benchmark an amplifier was use two 8ohm (i forget the wattage, i think it was 300 watts)

well here is my confusion..
i get that a resistor can add resistance by whatever the ohm rating is.
but
i am confused about the power coming out of the resistor.

at first thought, i figured a 2ohm 10 watt resistor would add 2ohms to the line with a maximum of 10 watts allowed before the resistor would be over its rated capacity.
and if that is true, does the resistor simply add 2ohms to the line up until the 10 watt rating?

my cd player is rated at 22 watts RMS (at 4 ohms i think)
i put one 2ohm 10 watt resistor on each speaker terminal to keep the radio from seeing a 2ohm load.
i didnt connect the resistors together in anyway, other than through the voice coil.

it got me wondering about how much power my speakers are seeing.
and then i started to wonder if the 10 watt rating is actually not safe because the radio is said to put out 22 watts RMS.

i'm wondering if i am bleeding an extra 10 watts through the resistor when i shouldnt be.. or if the resistor on the other end of the coil will add another 2ohms, as well as another 10 watts of protection.



the other way i was thinking about resistors..
if i had two 2 ohm 50 watt resistors and had an amplifier that puts out 100 watts RMS at 4 ohms,
with each resistor in a speaker terminal, and then the other end of the resistor hooked up to a multimeter, why doesnt the multimeter read 0 volts?



i started to wonder if i should dial in my amp gain with a dummy load.. because that is what i had heard about.
it makes some logical sense to me that the amplifier might give a different reading with the very small resistance from a multimeter compared to the 4ohm resistance of the speakers.
to think it is possible, sure.. but practical in everyday consumer amplifiers?
that isnt something i would know about.

to me..
maybe the caps bleed different at 4ohms compared to 0.04ohms.
maybe the torroidal coil bleeds differently too.

i heard about dialing in the amp gain with the multimeter when there isnt an oscilloscope around.
they said they were using dummy loads.
it made me wonder why they can hookup some resistors and gather an accurate voltage from the amplifier output.
if its jst a dumb addition of resistance with the max wattage rating being the 'watt' portion on the resistor, then it makes sense to use the resistors to dial in the gain.


then i stumbled upon an MTX video that says jst use ohms law to find the voltage and hookup the multimeter with a 60hz sinewave (this is what i did).
but
then i found a video about some demo product that claims to be an oscilloscope for 1khz and 40khz to detect clipping.
in the video, they hooked up the ground to the actual ground of the amplifier.. and then the positive wire to the speaker terminal.
they said it doesnt matter if the speaker is connected or not because it works either way.
personally.. i think it boils down to the same thing about having a load connected to the amp.
for the purist i am, it says to me that the exact load needs to be on the amplifier and we should be thankful the multimeter is very little resistance.

jst like calibrating an equalizer..
you set the volume knob to a specific number, and that means the calibration takes place at that specific number.
so if you got the volume set to 45 .. dont expect the calibration to be valid at 40

can i leave the speakers hooked up and put the ground lead on the negative battery cord and the positive on the speaker output without damaging my multimeter?

should i think the resistors i put on those speakers will add 2 ohms to the line before the voice coil safely, or am i going over by 10 watts, or did i actually add 4 ohms to the coil because the other 2 ohm resistor is on the other speaker terminal?

i really started to think about jst how hot those resistors might get, and jst what kind of stupid danger i put myself in.
because at first thought,
i said.. okay i need an additional 2 ohms, but these resistors are only 10 watts.
i'll jst add two to bring the wattage up, and i will keep them seperated to keep the resistance from doubling.

now i am starting to think,
what if one wire pushes with 22 watts RMS and the other wire pulls with 22 watts RMS .. because that means i am 12 watts over the limit of those resistors.

i really dont need a fire in my ride.
i really dont need the resistor getting the glue hot, and then the resistor falls off and touches something that causes the cd player to get damaged.

that brought me to wiring the two resistors in parallel.
first of all, i disagree with the theory that two resistors in parallel is absolutely going to cause the electricity to flow through each resistor before it makes it to the other side.
i believe series is the only way to do it, and i refuse to touch the parallel method.

but when i seen other people were trying the same sorts of things with smaller resistors all grouped up together and taped.. it made me question just what makes them confident parrallel will flow perfectly without any bleeding or surging through jst the one resistor.
it made me curious more about how the electricity flows through and results to a lower voltage other than the subtracted 2 ohms.


perhaps all of that rambling seems a bit crazy, but there is some safety concern in there.
i thought the comparison of the two ways i thought about the resistor is very easy to help guide me.
either i've already got it and jst need an okay, or i've got something to learn.

i figure you might say..
well.. you added 2 ohms to a 2 ohm coil, and that is step one to keep your cd player safe.
at worst, the electricity goes through the resistor and through the voice coil until it sees the second resistor.
but
this raises another question,
does the amplifier send a push signal down the positive wire and all the way up the negative wire.. or does it push the signal down the positive wire and simply leave it there to linger and dissipate into heat?
(what are the two differences between amplifers, mainly the name or class of each one?)


i'm hoping somebody will simply take the time to answer my questions for the sake of helping another person 'up' their knowledge a bit.
but
i am seriously thinking about maybe removing those speakers, or at least checking how hot those resistors get.
but
i dont know how resistors fail.

i'm wanting to take my little 'quick fix' to the next step of safety to keep myself calm and out of some seriously big problem because i tried to duct tape something and did it wrong.

anwaypasible 25th May 2012 07:18 AM

here's my protest against oscilloscope usage..

i think this is necessary to think about.

people say.. jst get an oscilloscope to see the soundwave on the screen and turn it up until it clips, and then jst turn it down until the clipping goes away.
BUT
think about this..
if
say the pieces inside the amplifier start out with 6 arms and hands to help carry the audio signal.
if those pieces are pushing out 35 volts when they are only ment to work at 24 volts .. the extra volts MAYBE takes some of those arms and hands away.

i think
if
the extra arms and hands go away BEFORE the soundwave starts to clip.

when you carry bags of groceries, your fingers hurt before your arms meet the limit.
finger pain first.
then your biceps and forearms say 'no'

sofaspud 25th May 2012 07:52 AM

Quote:

i'm hoping somebody will simply take the time to answer my questions for the sake of helping another person 'up' their knowledge a bit.
Everyone will be helped if you do a little self-editing. Your post reads like a less-than-organized stream-of-consciousness rant that I honestly don't have the patience for. Please re-ask your questions in a more cogent manner.

anwaypasible 25th May 2012 08:28 AM

no need to be cruel about 'stream of consciousness' when there is nothing more open or honest.

i'll take my freedom from torture, freedom of speech, freedom of conscious, and right to a fair trial.

if you want your freedom from torture and freedom of conscious, it simply means you are too insecure to be socializing in public.

you dont have the patience, yet you posted anyways.
your hypocritical choice tortures us both.

you really shouldnt be allowed to talk to innocense the way you did.
i doubt you obtain the consequences of your actions.

i dont want to continue arguing with other posts in this thread, i simply wanted to reply and move forward without your welcome.

**for what it is worth**

if you read it and you know the answer, then sharing it is your choice.
if you read it and you dont want to answer, then you simply dont want to socialize about the topic you are reading.. making me question why you read it ever in the first place.

sofaspud 25th May 2012 08:38 AM

Umm.... yeah.
I was making an effort to help you, and wanted your help in return to do so. That's why I replied to your post. No cruelty intended. Are you sure you can recognize "open or honest."
Best of luck to you.

PS
Quote:

perhaps all of that rambling seems a bit crazy
That's your own description of your post.

anwaypasible 25th May 2012 08:55 AM

i seen a youtube video moments ago, but i accidentally closed it after reading the flatulance from sofaspud.

but
the video stated the same thing i said about '2 ohms is the amount of resistance added and 10 watts is the rated limit'

as for hooking up the negative lead to the battery cable and hooking up the positive lead to the speaker terminal .. depending on the type of amplifier, that soundwave might be cut in half horizontally and either not work with the multimeter or damage the meter.

i do not have the energy or the patience to go into detail about my feelings of 'divide and conquer'
especially when a forum is ment to bring people together.

i think i'll leave this section of the forum and ask in the amplifier section.

anwaypasible 25th May 2012 09:02 AM

i also said:
Quote:

very easy to help guide me.
and:

Quote:

i'm hoping somebody will simply take the time to answer my questions for the sake of helping another person 'up' their knowledge a bit.
realize you asked me to be closed-minded in a place of open discussion.

an effort you succeeded is indecency.

HawaiiGuy 25th May 2012 09:05 AM

Quote:

Originally Posted by anwaypasible (Post 3036043)
i learned they were 2ohms

What method did you use to determine that they were 2ohms drivers?

anwaypasible 25th May 2012 09:53 AM

digital multimeter.

the importance is this:
maybe only 11 watts RMS of 'push' goes down the positive speaker wire, while another 11 watts RMS of 'pull' goes down the negative speaker wire.
if this is true, then i am only 1 watt over the limit and i dont run the amplifier at full blast to see all 22 watts RMS .. therefore i should be safe and sound.
but
this brings up the question.. did i add an extra 2 ohms to the amplifier load for a total of 6 ohms ?

HawaiiGuy 31st May 2012 08:53 PM

Quote:

Originally Posted by HawaiiGuy (Post 3036272)
What method did you use to determine that they were 2ohms drivers?

Quote:

Originally Posted by anwaypasible (Post 3036303)
digital multimeter

A DMM alone does not give you the impedance of a speaker. You probably measured the DC resistance of the driver which is almost always lower than the speaker's impedance.

Car stereo tweeters are most likely 4ohm. Remember to put a non-polar capacitor (film or electrolytic) in series with each tweeter (unless you are already using a crossover).


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