How to test speaker ohms?

Well, you can measure the "ohms" in several ways but that is quite inadequate for selecting a suitable replacement.

Kal

I think you want to toss it.

The impedance of the speaker is only one of about a dozen parameters that you need to measure for the driver. Vance Dickason's Loudspeaker Cookbook has a whole chapter on measuring T-S parameters of an unknown driver.

Sadly most folks are measuring inside the frame, and including the surround in the cone size.

Really, though... if this is what I think this is, it's a junk speaker and not worth the labour to haul it to the dumpster.

--scott

You cannot test the AC ohms of a speaker with an multimeter, because the multimeter only measures DC ohms resistance.

"Paul"

The DC ohms plus 15-20 % rule applies to any cone loudspeaker ( drivers only, not systems) - it accounts for the additional resistive losses in the magnet structure and suspension parts when that speaker is driven with AC at the frequency of its impedance minima.

..... Phil

Well being what they are, they sell for like $25 - $40 a pair used. So... for cheap and since you already paid for them, you can try fixing the tear using the paper unwrapped from a couple of teabags and some rubber cement. After it dries you can color it a bit with magic marker,

Or just call Fisher Sanyo and ask them

Reconing isn't so very hard for DIY, but being what they are you could just buy another pair on Craigslist for parts - and it would be better to buy something else, especially for working on music. Modern speakers are much, much better and 30 year old speakers have to be dogmeat by now.

Will Miho NY TV/Audio Post/Music/Live Sound Guy "The large print giveth and the small print taketh away... Tom Waits

Many nominal 8 ohm speakers I've seen measure as low as ~ 5 ohms at DC. Largely SR/PA types though.

Graham

Excepting Quad electrostatics !

Graham

The "nominal 8 ohms " value quoted by the makers is NOT derived by electrical test, but is a *marketing tactic*.

EV started this nonsense in the 1980s, in order to squeeze out a couple of dB extra sensitivity and so out-spec comparable JBL products - in the eyes of dim witted customers.

Hi-fi speaker brands often do the same and justify it as "compensation " for resistive losses in typical passive x-overs.

..... Phil

If you can find me some for $25 I'll take them - and recone 'em myself! A little saran wrap, ....

Will Miho NY TV/Audio Post/Music/Live Sound Guy "The large print giveth and the small print taketh away..." Tom Waits

That's a calculated estimate, not a measurement. There is a difference.

Take out the bad unit and show it to a shop that sells replacement drivers. Buy a couple of whatever they recommend. They won't be very expensive. Install them. If they sound good, fine. If not, buy some more speakers. Yours are worth spending a little time and money on, but only a little.

No, although you CAN measure the DC resistance and do some handwaving and say the impedance at 1 KHz is probably more or less about 1.5 times the DC resistance. This is usually enough to get you into the ballpark if you know the speaker is rated for a common impedance.

But, sadly, the impedance is only one of a whole lot of things the original poster needs to know to replace the driver.

--scott

That's still more or less within range, if you know it's a standard load. If you see 5 ohms DC, you know it cannot possibly be a 4 ohm speaker, and it almost certainly isn't a 16 ohm speaker, so it's probably an 8 ohm speaker.

--scott

There are speakers that have that 6 ohm nominal Z. Common in todays consumer market.

Z is probably the least important spec the guy will need. Efficiency and resonance, and physical size are more important. I was loking for some cheap looking units of about 8 ohms. Here Loook..

Whenever I replace something its usually to BOTH sides if not an identical replacement. Even that, it needs checked for uniformity.

greg

except when you put a 4 ohm loudspeaker on a passive crossover designed for a 8 ohm box it doubles the value of the crossover point so if it was crossing over at 1800 with a 8 ohm speaker it will now be crossing over ar 3600 with a 4 ohm load george

It depends on the crossover network, but even a simple 2nd order LC network has a nominal crossover point independent of load (The frequency where the impedance magnitudes of L and C are the same). The drive unit impedance will have an effect but it will be second order.

The fact remains that using a 4 ohm unit where an 8 ohm one is expected still won't work very well: the balance between them won't be right, and the impedance/frequency curve of the whole box will be even more wonky than usual.

Well it probably will not work well, but the nominal Z is not important. You have to know the exact graph of Z to know what the Z is at for some desired crossover. The order of the crossover is also very important to driver damping. You can get some really bad plots from some crossover using another driver with different stories. Unless you get real lucky, replacing it will cause some kind of grief. Its highly unlikely that the level matching will be on or the phase will be slightly off. Many speakers will have level controls, and sometimes that will be enough to compensate, but level controls often also change the plot.With the name of the manufacturer in mind, the crossover probably does not have any impedance compensation or response compensation. Everything is built into the drivers and simple crossover. Remember the driver can also cause an added pole depending on the phase shift.

greg

If it's really just a tear, and not a hole, you can repair the cone with a little fingernail polish and toilet paper.

Good Luck! Rich