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Need help with speaker ohms

post #1 of 33
5/8/11 at 4:38pm
Thread Starter 
Here's the deal. I bought a second pair of speakers that i've had for years for use as zone 2. 1 driver was damaged in shipping and not worth the cost to send back. The damage was done to the 6.5" woofer(3), its very stiff and pops/crackles when playing.

My question is, if I simply disconnect both terminal's on the woofer(3) will it still be configured at 6 ohms? If not how can I rewire it for 6 ohms. All speakers say 6 ohms stamped on them but do not say anything else. I've done some reading on different wiring's for speakers but this type wasn't covered. All speakers in my HT are currently 6 ohms with the receiver set to 6 ohms.

The picture shows the original factory wiring.


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post #2 of 33
5/8/11 at 5:59pm
Those other drivers likely have some kind of filter on them so if you take out the 6.5 driver, you will lose a ton of bass. Will that be OK in what you want to do? Assuming so, the best way to figure out the impedance is to get a multimeter, set it to ohm setting and measure it. You can pick a multimeter up for a few bucks if you don't have one.
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post #3 of 33
5/8/11 at 6:10pm
Thread Starter 
Quote:
Originally Posted by amirm View Post

Assuming so, the best way to figure out the impedance is to get a multimeter, set it to ohm setting and measure it.

Thats a correct assumption. I forgot about the multimeter, I bought it years ago and lost the manual so I dont know how to use it properly

Any links for some easy training with them?
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post #4 of 33
5/8/11 at 9:14pm
Thread Starter 
I think I figured it out, kinda. The way they have it wired is basically in 2 lines. Line 1 6ohm+6ohm=12ohms, 2nd line takes away 6ohms resulting in a 6ohm configuration. So unless I get another 6ohm woofer my choices with the 2 remaining drivers is either a 3 or 12ohm load. Obviously 3ohms is too much stress but a 12ohm load for B speakers would almost be perfect.

Am I missing anything?
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post #5 of 33
5/8/11 at 9:53pm
12 Ohm in parallel with 6 ohms = 4 ohms, not 6.

Formula is 1/ (1/R1 + 1/R2) for R1 and R2 being parallel.

I still don't understand how you think the tweeter is wired directly. Is there not a capacitor en-route to it? If so, it is not a 6 "ohm" resistor.
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post #6 of 33
5/8/11 at 10:39pm
Thread Starter 
Quote:
Originally Posted by amirm View Post

12 Ohm in parallel with 6 ohms = 4 ohms, not 6.

Then how did they get a 6ohm configuration. Is it the capacitor changing the ohms or is all drivers 18ohms

Quote:
Originally Posted by amirm View Post

I still don't understand how you think the tweeter is wired directly.

mis-communication i guess, the mid is wired directly. I tried getting a better shot but no luck this time of day. from the terminals you can see the line goes to the woofer then tweeter.


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Quote:
Originally Posted by amirm View Post

Is there not a capacitor en-route to it? If so, it is not a 6 "ohm" resistor.

I thought that was just a frequency filter.


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Did i get the part about running a series/parallel at 12ohms correct? Maybe i've been reading the multimeter wrong.
Thanks for helping, I have so so much to learn...
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post #7 of 33
5/8/11 at 11:00pm
There is a hard part and easy part on this.

The easy part is this: the woofer and mid are parallel and therefore have a resistance of 3 ohms.

The hard part is that we don't get to add the tweeter to this with simple math.

The value that you see for the speaker is not a resistance but impedance. The difference being that the latter is for changing signals such as your music. Speakers have a complex impedance that changes up and down with frequency. The value provide by the speaker manufacture is a nominal value. Here is an example:



To figure out that curve, you need to know the full characteristics of the speakers. This is not something you are going to be able to do.

If I understand what you are trying to do, the above is not very material. If you disconnect the woofer, and the mid is still connected direct and has a nominal marked value of 6 ohm, you have a safe value for your amp and you can proceed to use it that way. Your effective impedance will now but higher than it was before which is a good thing from safety of not damaging your amp or causing its protection circuit to kick in.

For a check, set your multimeter to "ohm" setting. Connect the two leads together as a check and it should read a value very close to zero. Now connect them to the terminals of the mid speaker. If it reads close to 6 ohms, you are golden. For grins, read both values (mid and woofer) and report back.
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post #8 of 33
5/8/11 at 11:27pm
Thread Starter 
The readings Im getting for the woofer is 5.6 and the mid is 5.8.
I tried re-using the installed wires but couldn't get any readings through the terminal and a continuity test failed without the woofer plugged in, that truly confused the life out me. I then tried a continuity test on both of the caps and they failed. So i was forced to re-wire.
right now it is:
+TERMINAL> +TWEETER
-TWEETER> +MID> -TERMINAL
and getting a reading of 11.5
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post #9 of 33
5/8/11 at 11:30pm
Oh, oh. I hope you didn't make this worse . You weren't supposed to remove the capacitor from the tweeter. Leave it in series with it. Without it, it would instantly get damaged! You weren't supposed to see any reading across the cap. So that was OK.

Wire it just the way it was. + and - terminals to go to mid and the same two wires go to the tweeter except that there is a capacitor inline with it as there was. don't worry about anything else for now. Just hook it up this way.
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post #10 of 33
5/8/11 at 11:41pm
Thread Starter 
I took out the whole line so everything is still intact. The mid also has a cap on it. So I should hook it back up the way the manufacturer had it with the exception of the woofer being disconnected?
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post #11 of 33
5/8/11 at 11:43pm
Yes. But keep in mind that you will have very little bass if there was a cap on the mid too. But it will make some sound .

You may want to buy another woofer of that size. Anything will do as long as it has the same hole pattern and size.
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post #12 of 33
5/8/11 at 11:54pm
Thread Starter 
Its back in and im not getting any readings from the terminal. Im going to try to guess why, the caps are blocking it. When I read the terminals on the fully functional speaker its just reading the woofer, the tweeter/mid are blocked. right?
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post #13 of 33
5/8/11 at 11:55pm
Correct. The voltmeter reads the DC value which is now infinite. Go ahead and connect it up and start the volume low and gradually go up.
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post #14 of 33
5/9/11 at 12:23am
Thread Starter 
first I disconnected the woofer on the good speaker, hooked them both up and they seem to be working fine. tried the radio first but signal was to static, switched to a loss-less source and they sound ok (bass would help but thats what my subs are for). the volume was eventually raised to -10db without protection turning on.
Are they running at 6 or 12 ohms now? I'll be meditating on this thread for weeks
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post #15 of 33
5/9/11 at 9:18am
They are not running on either. It has a graph that is frequency dependent. As I mentioned before, it wasn't 6 ohm before either when playing music.

The reason I asked you to be careful with the volume is that now you have a "capacitive load" which can cause some amplifiers to become unstable as it is a very unusual speaker load. But if you played it enough at -10db, it should be OK.
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post #16 of 33
5/9/11 at 9:42am
Quote:


the best way to figure out the impedance is to get a multimeter, set it to ohm setting and measure it.

Quote:


Thats a correct assumption. I forgot about the multimeter,

Sorry, but you can't measure impedance with an ohmeter.
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post #17 of 33
5/9/11 at 9:44am
Thread Starter 
Whats is the primary function of the capacitors? Would it be to block low frequency's or maintain a safe load with all speakers wired? You mentioned not having them in the series would damage the tweeter, was that because they would be receiving a full range signal?
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post #18 of 33
5/9/11 at 9:52am
Quote:
Originally Posted by sebring8259 View Post

Whats is the primary function of the capacitors?

They have a number of uses in general. In that specific configuration, it is creating a high-pass filter where low frequencies are attenuated.

Quote:


Would it be to block low frequency's or maintain a safe load with all speakers wired?

Correct although it is the crudest form of filter you can put in there so some of the low frequencies still get through.

Quote:


You mentioned not having them in the series would damage the tweeter, was that because they would be receiving a full range signal?

Correct.
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post #19 of 33
5/9/11 at 9:54am
Quote:
Originally Posted by SAM64 View Post

Sorry, but you can't measure impedance with an ohmeter.

Sorry that was a typo. Puzzled that you thought it should be pointed out given the text of my posts explaining the difference but I will live .
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post #20 of 33
5/9/11 at 10:10am
Thread Starter 
If I was to re-wire without the caps going:
+TERMINAL>+TWEETER
-TWEETER > +MID
-MID> -TERMINAL
giving me a 12ohm load, would I eliminate the danger to the tweeter using the high frequency cross-over terminals on a Cerwin Vega SW-12B?

Here is the multimeter im using with the woofer getting a reading.
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post #21 of 33
5/9/11 at 10:32am
Quote:
Puzzled that you thought it should be pointed out
I guess I was puzzled that someone with your expertise would make such a simple mistake
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post #22 of 33
5/9/11 at 12:07pm
Thread Starter 
Quote:
Originally Posted by sebring8259 View Post
If I was to re-wire without the caps going:
+TERMINAL>+TWEETER
-TWEETER > +MID
-MID> -TERMINAL
giving me a 12ohm load, would I eliminate the danger to the tweeter using the high frequency cross-over terminals on a Cerwin Vega SW-12B?
edit 1
and that resulted in a 2.3ohm load...

edit 2
I just made things more difficult for me trying to learn this. Using the same method testing the woofer in the picture above, the reading im getting on one of the fully functional 6ohm speakers while hooked up to the receiver is fluctuation from -.3 to +1.0 when on and around +6 when off...
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post #23 of 33
5/9/11 at 3:18pm
Wouldn't that depend on the scenario? If you took an ohmmeter and measured a purely restive circuit, your impedance should be correct.

Seems to me, that you can get a pretty good idea of average speaker impedance with an ohmmeter from just knowing the VC's impedance.
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post #24 of 33
5/9/11 at 10:17pm
Quote:
Originally Posted by sebring8259 View Post

edit 1
and that resulted in a 2.3ohm load...

edit 2
I just made things more difficult for me trying to learn this. Using the same method testing the woofer in the picture above, the reading im getting on one of the fully functional 6ohm speakers while hooked up to the receiver is fluctuation from -.3 to +1.0 when on and around +6 when off...

What do you mean when "on?" You must not try to measure its resistance while playing it. You can damage your meter (or blow its fuse).

Here is what I suggest if you want to play with it and don't mind damaging things . Bypass the cap going to the *mid* woofer. Just short it out with a wire. Leave the tweeter as is with the cap inline. This will put all the bass frequencies to the 3 inch driver.

Now, if you are using an AVR to drive it, set its cross over point as high as it will go (hopefully above 100 Hz). Then connect the speaker and slowly turn up the volume and see how much bass the mid will handle. Hopefully fair bit before it starts to get distorted.

And oh, don't try to figure out the impedance. It just can't be done with the meter.
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post #25 of 33
5/10/11 at 4:07am
Quote:
Originally Posted by MichaelJHuman View Post

Wouldn't that depend on the scenario? If you took an ohmmeter and measured a purely restive circuit, your impedance should be correct.

Seems to me, that you can get a pretty good idea of average speaker impedance with an ohmmeter from just knowing the VC's impedance.

As you say, DC Resistance is a pretty close estimate of speaker driver nominal impedance. The DC resistance of a speaker driver is usually about the same as its minimum impedance. It's rated impedance or average impedance usually runs about 25% higher.

Another factor that relates to minimum system impedance might the the DC resistance of any inductor that is in series with the woofer driver. This inductor usually doesn't exist in cheap speakers, but it is often added in better speakers.

So, in cheap, simple speaker systems woofer DC resistance + maybe 25% gives you a good estimate of its nominal impedance. In expensive systems the system impedance might be a bit higher than that. But, there is no rule that the speaker system's actual impedance can't be higher than its rating.

What you can't figure out with just an ohm meter reading is much of a clue about the speaker driver's entire impedance curve. For the past 40 or so years there have been procedures involving voltmeters, signal sources and precision resistors that could be used to deduce the Thiel-Small parameters for the speaker driver, which can be used to estimate its effective impedance curve.

These days you can get a gizmo from Parts Express for about $100 that hooks to your computer's USB port and comes with some software that does the heavy lifting for you.
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post #26 of 33
5/10/11 at 11:42am
Thread Starter 
Quote:
Originally Posted by amirm View Post

What do you mean when "on?" You must not try to measure its resistance while playing it.

I thought that maybe if I was to try to get a real-time measurement it might solve the question of what the impedance/load is. Right now I'm going to focus on a better understanding without the use of random experiments. If I break my AVR I will cry!

Quote:
Originally Posted by amirm View Post

Here is what I suggest if you want to play with it and don't mind damaging things

Its not that I don't mind breaking things. In fact if I do break something unintentionally I'll be upset but will have only myself to blame.
The main thing I want to keep from damaging is the AVR. Its a tragedy that a perfectly fine speaker was rendered useless just because of poor packaging. But because of this it has allowed me to play around with things that I yearn for knowledge on. If the capacitor is doing its job I'd rather not short it out deliberately, maybe save it for trying other experiments in a different quest for knowledge. I dislike waste and that's exactly what I'm trying to eliminate by using these speakers in this trial. Please don't get me wrong here, your help is very much appreciated! If it comes down to not needing/wanting a functioning capacitor then I will absolutely use it in a manner that may or may not destroy it so long as there is a goal of learning the unknown.

Quote:
Originally Posted by amirm View Post

And oh, don't try to figure out the impedance. It just can't be done with the meter.

What can be done with the multimeter?
Before answering that I need to understand electrical theory better: SOURCE

Quote:


ohm is the unit of measure for impedance.

-err, So I cant use a multimeter to measure impedance and in turn I cannot measure the ohm? where does resistance fit into this? Is it just another term for impedance or does that vary?

Quote:


flow of electrons through the wire is measured in Amperes.

-ok
Quote:


Voltage is the force of electricity that pushes the electrons through the wire.

-ok

Quote:


things that restrict or control the flow of current are said to impede current flow, and are described as having impedance.

-err, so in this situation the driver is a restrictor and the capacitor is more of a controller?

Quote:


In an electrical circuit, the device that uses electrical energy and has impedance is called the LOAD.

-umm, speakers use electrical energy and the driver has an impedance. But I (can) use the multimeter to measure the load with the ohm function?

Quote:


Current (in amperes) equals voltage (in volts) divided by impedance (in ohms).

err, without risking damage to the AVR, can I use the meter to measure the amp's amperes? (V)120/(ohm)6= (current) 20 amperes? That can't be right..

Quote:


Impedance (in ohms) equals Voltage (in volts) divided by Current (in amperes)

-ahh, without knowing what the current is, the impedance is currently beyond my reach. But if I was to find that out I could use that data to then know what the ohms are?

Quote:
Originally Posted by sebring8259 View Post

Receiving assistance on uber-noob questions is a blessing.

You got that right! Thank You!
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post #27 of 33
5/10/11 at 2:04pm
Two quick points: 1 - the current carried by the speaker wire is not DC - it represents a fluctuating signal and shouldn't be considered the same as "normal" direct current described by those introductory principles. 2 - When your multimeter is set to the resistance setting (to measure "ohms") it will apply voltage and use it's ammeter to calculate resistance. (resistance equals voltage divided by current - you can't measure resistance directly)

You're getting good help, and I'm reading along learning - but I just figured I'd butt-in to correct quickly where I could. Also, if I can plug a good resource Hyperphysics is a great way to read about all the principles - the key is recognizing where they apply (such as - audio signals are not DC).
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post #28 of 33
5/10/11 at 2:44pm
Quote:


the current carried by the speaker wire is not DC - it represents a fluctuating signal and shouldn't be considered the same as "normal" direct current

But, Ohms law still applies, weather it's AC or DC.
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post #29 of 33
5/12/11 at 11:09am
Quote:
Originally Posted by SAM64 View Post

But, Ohms law still applies, weather it's AC or DC.

True enough - I suppose the error specific to the way the OP was trying to apply Ohm's Law was in assuming that a 120V appliance was going to apply 120V to his speaker wire. That said, calculating the current load of speaker wire in this case is not relevant and I wanted to call attention to the idea that just because you (think you) have two out of three variables, doesn't mean you should use an equation to come up with the third...
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post #30 of 33
5/12/11 at 11:33am
Thread Starter 
And the op appreciates that keeping things basic is alot more helpful for me. Starting at the bottom and working my way up is what im trying to do. By posting 120v there, im basically saying "i dont know where to start and I know thats not it, could someone please point me in the right direction".
I did not know that "the current carried by the speaker wire is not DC - it represents a fluctuating signal and shouldn't be considered the same as "normal" direct current" so that was very helpful to me
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