terminals acting sketchy.

[stevemead08 752]

It's a whole lot worse with 3 subs hooked up. Measuring at the amps, I can get a 6ohm or more even fluctuation.

[nadcicle 77]

Had similar issues. I've noticed it does it with some meters and not others. Did it to a Klein, but not my Fluke. Move the meter itself as far out of the field of magnetism as possible and see if it does it more/less?

[stevemead08 752]

I've tried 4 different meters. I even went out and bought the Milwaukee one because I thought my other 2 were broke. Also tried a fluke at a show.

Its just as bad at the back of the truck, away from the motors.

Though even with the direct leads, I still get fluctuations. If I use a different sub I have here as a sample, it stays at .7 steadily.

[nadcicle 77]

I felt that truthfully you were still getting the fluctuation with the direct leads as well. Thing is, with a higher impedance it was just more noticeable is all. I would venture to say the issue is under the dustcap where the leads meet the coil now unfortunately. I am going to go check my reconed ones now that you mention it. I will make a video to see if it does anything similar.

[stevemead08 752]

Like stated above your post, I am still getting weird readings. Much more tolerable than before though. I feel like the fluctuations is what might be sending my amps into protect.

It's hard to argue with success though. Truck still makes stupid numbers, for what it is.

[nadcicle 77]

So is it doing this with 1 or both coils on all of them, or just kinda here and there or what?

 

Made a quick video to show how quickly it settles on a fresh recone (Still processing higher resolution). Results vary a bit it seems. Also, disregard the setting the phone down to test out the second sub. The moment i set it down the magnet made the video stop. lol

 

[stevemead08 752]

That's awesome results for you!

Unfortunately for me, it's all 3 subs.

This is not a new issue for me, although I didn't test them fresh out the box.

I tested them the first time a while after I got them, after I'd played them a little bit. I noticed it first after I got to a show and it was all crazy. I thought I had a blown sub. I separated all three and tested individually. Granted I was at a show with music and bass blaring. I chocked it up to the environment around me. Put it back together and went and set some records at the same show.

I tested again in my quiet garage, same results.

[nadcicle 77]

I'll follow up with my used subs tomorrow. I know new wasn't fair now that I think about it.

[95Honda 486]

You kind of need to go back to basics to understand what is going on here.  The terminals aren't the reason for your erratic readings.

 

A loudspeaker is a transducer.  It takes one form of energy (electrical current) and coverts it to another form (acoustic energy).  It also can also do the opposite, change acoustic energy into electrical current.  

 

Your multi-meter measure DC resistance (in no way does it measure impedance).  It does this by applying a very, very minute amount of DC current to whatever circuit is placed in series with it and it measures how much current flows through the circuit and calculates the DC resistance from this.

 

Any, and I mean ANY small (talking micro to low milliamp) current introduced into the circuit under measurement will throw off the meter, substantially.  The subwoofer will produce milliamps of current with you talking in the same room at a low level and it being 10' away...  That is how easily it effects the meter readings.

 

So why are my direct leads making a difference?  Simple, due to tension on the leads you have changed the mechanical dampening on part of the suspension and reduced the woofers ability to act as transducer.  You have changed it just enough to dampen out some of the cone movement and therefore some of the current being introduced to the meters DC resistance measuring circuit.

 

It is also easy to see how this works if you have a recone by itself out of the motor.  You can hook up the leads any way you like and you won't get any more fluctuation than the meter leads by themselves as the recone cannot act like a transducer without the motor attached.

 

Additionally, if you were to place a tight shim in the gap that locked the cone in place you would not see the fluctuations.

 

And lastly, these measurements do not in any way AT ALL represent anything your amplifier sees. You are talking milliamps of current, once connected to your amplifier the output impedance dampens any of this, completely, and it will never effect the overall load your amplifier sees in the slightest.

 

I hope this clears up what is going on.

[95Honda 486]

Oh, and the fresh recone has more mechanical dampening since the spiders are new, so that is why you get less flucuation...

[swift 501]

Nice explanation.

Mine once was readings crazy high at the terminals on the box and we closed the door and it went back to normal instantly.

[stevemead08 752]

Thanks for all the input 95Honda.

I agree with everything you typed, except the direct leads adding tension to the suspension. The leads are suspended in the same manner as the terminals being connected.

I also agree that my lack of experience is clouding my expectations of this test.

[95Honda 486]

Believe me, it doesn't take much.  It could be as simple as the mass of the probes or the way the leads are angled from the terminal.  You are talking micro and milliamps...  The bottom line is, you don't have to worry about anything you are measuring being presented to the amplifier.

[95Honda 486]

That means 1 millionth of an amp...  Yes, .000001.... 

 

Also, take a 25 pound weight and lay it on the cone (find a way to do this without damaging the driver) and you will see the fluctuations drop because of the increased mechanical dampening...

[stevemead08 752]

Could you explain how what I'm reading has no effect on the amp?

Does it react differently under power?

My understanding is that you order the correct ohm drivers to present the amplifier a certain load.

Ive never experienced any sort of fluctuations on a driver in the past. New or used.

[swift 501]

It's funny, before me getting into the spl side of things I just would test once when it would be installed and never look again. Now I'm checking shit all the time, lmao.

[95Honda 486]

Re-read what I posted about the current levels causing your meter fluctuations.  They are anywhere from 1/1,000 to 1/1,000,000 of an amp.  You amplifier has what is called an output impedance.  It is very low, like well under 1/100 of an ohm.  It completely dampens out ANY current fluctuations caused by your woofers turning spurious acoustic energy into electrical energy...

 

Want to see how output impedance works?  Tap on your woofers with the amplifier off and then on.  You will see how it dampens out the woofer...  It literally acts like a brake on the cone...

[stevemead08 752]

Awesome!

Thanks for the very in-depth explanation.

[95Honda 486]

And don't forget, you CANNOT measure impedance with a mutimeter the way you have it hooked up.  You are in no way measuring what your amplifier sees...

[stevemead08 752]

I know DCR is not impedance.

While I'm walking the line of safe ohm load and way too low. I thought even the slightest fluctuation would be crossing the "too low" ohm load.

Some burps, I'm good. Another burp, I protect.

[95Honda 486]

Don't worry, the fluctuations you see the amp never does.  Also, what you are seeing can very well be lower than the driver DCR due to the current flow from the driver.  Again, the amp will never see this though, only your multimeter...

[nadcicle 77]

I'm sure you checked batteries already, but I don't think we're all alone in calling it impedance instead of resistance most times.

[stevemead08 752]

I've tried 4 different meters...

And other subs. These are the only ones I've seen this on.

[antoinez28 62]

It's funny, before me getting into the spl side of things I just would test once when it would be installed and never look again. Now I'm checking shit all the time, lmao.

that's what I do guess I need to look at my stuff more than once

[Sencheezy 689]

I've tried 4 different meters...

And other subs. These are the only ones I've seen this on.

 

Check under the cap.

Out of the 6 recones I've ordered for the ohm change, 1 coil was not reading, at all. The problem relied underneath the cap. Not sure if this is the same reasoning for your readings, but worth a look.