How to test speaker ohms?

he

s in

As the other poster said, your method is a very rough guestimate.

My point, Dumbshit, was that the impedance of a speaker is measured with AC, not DC.

"Anahata"

Cos the word "nominal" means " in name only ".

In *reality*, a 2:1 impedance mismatch with a x-over filter has DRAMATIC effect on its performance and the load impedance seen by the driving amplifier in the region of the crossover frequency.

Eg An under loaded LC x-over filter turns into a series tuned circuit - it then has a VERY low input impedance at the resonant frequency and MULTIPLIES any input signal by many times creating a huge peak in the response around that frequency. Very bad news.

..... Phil

It's ages since I ran a plot, so it's a bugger to remember. Note that the cabinet will influence actual AC Z too.

And now you get home hi-fi and especially 5.1 systems where the speakers are actually rated at 6 ohms nominal to extract that extra dB or so.

Graham

Only with a first order crossover. As the fliter order increases, the difference will be less, but the filter damping suffers, so the response will still be affected.

Not to mention a GOOD crossover compensates for the T-S characteristics of the driver ( especially voice coil inductance ).

Graham

will have

controls

All the more reason to use active crossovers and bi / tri amping.

Graham

I once did a sweep of a driver without thinking, cone downwards on the bench. Turning it cone up made a visible difference to the plot. This is because the speaker is doing mechanical work.

Graham

I tend to use PVA as the glue. More flexible.

Graham

"Eeysore"

No wonder the impedance curve was NOT the same as for "free-air" !!!

The correct procedure for finding the Fs of a driver involves dangling it from the roof on a string.

..... Phil

You cannot properly measure impedance with a DC device.

VOM read both ac and dc here is how to use a VOM to measure impedance of a unknown but working speaker, it does involve injection of signal

george

A multimeter (see above) does not provide that signal.

the multimeter is doing the measurments. I am simply showing that a VOM is a useful tool that can be used to measure impedance

you do not need a fancy occiliscope/signal gen rig a amp passing noise such as between radio stations is sufficent

I use the Part Express /Dayton WT3 for my impedance measuments but years of in feild service to commercialsound system required that i understand how to get the most out of a VOM

link to the WT3

One of the fascinating things about UseNet is coming into contact (even if only at a distance) with people who, at the very least, need someone to talk to.

"Phil" (that's a Hitchhiker joke), do you think I'm actually bothered by your remarks?

I don't know anyone besides you that hasn't killfiled the aussie scumbag george

"Richard Crowley = yet another PITA wanker "

Nobody needs your posturing BULLSHIT shoved down their throats either.

And nobody give a flying f*ck what idiots like you think.

So piss off.

...... Phil

You are almost certainly correct. They tended to use OEM custom drivers for mass-market consumer goods back in the day (just as is the custom today).

You have not stated any motivation for this. In the likely opinion of most people here, you have a speaker that is not worth any effort to repair.

As others have observed you cannot measure AC impedance with a device that measures DC resistance. And AC impedance is only a small part of the picture. Your chances of finding an exact replacement depend on finding another set of speakers and cannibalizing the driver. Else you have no practical way of finding an exact (or even close) replacement. Fortunately, the speakers likely aren't worth the effort anyway.