Resistance of car sub-woofer

audioguru said:

For hundreds of "8 ohm impedance" speakers I have measured 7 ohms DC.
For many "4 ohm impedance" speakers I have measured 3.2 ohms DC.
But this "4 ohm impedance" speaker measures almost a dead short DC.

The voice coil of a speaker is a coil of wire that has a fairly high resistance. The impedance should be a little higher than the resistance. Or you could say that the resistance should measure a little less than the impedance. But not this low. I think something is wrong with this speaker.

Click to expand...

I always saw the DC resistance to be just a shade under rated impedance as you have also posted.

I think it's likely this speaker's voice coil is hosed.

Hi Electrician,
Your tiny speaker has a resonant frequency (500Hz) about 15 times higher than most speakers (33Hz).

audioguru said:

Hi Electrician,
Your tiny speaker has a resonant frequency (500Hz) about 15 times higher than most speakers (33Hz).

Click to expand...

It's not that tiny; it's a 4" midrange from a junked out Japanese 3-way system.

It's an exaggeration to suggest that "most speakers" have a resonance at 33 Hz; "most woofers" maybe, but not "most speakers".

I've attached the impedance vs. frequency characteristic of the 12" woofer and the 1.5" tweeter from that same system.

The general shape of the impedance curve is the same for all three drivers.

The impedance is not much more than the DC resistance for several octaves above resonance (the woofer has 5.9Ω DC resistance) for all of them.

yes neoprene rubber foam....meant to be more resilliant in larger high excursion or smaller violent subs.... also used in photocopier transfer rollers with a bit of carbon mixed in....... Ive worked with many subs, Nigel is right.
a cheap meter on ohms reads just bellow 4 ohms on a 4 ohm rated sub



anything else bellow around 2.5 and shes likely fried or like others have said a higher power handling 2ohm sub that had the wrong sticker slapped on it.

Sadly it sounds fried,

if it has a vent arround the magnet whats it smell like? Ozone / electrical smell ,burned paper , cooked glue or old socks?? may be an indication of friedness....
also check its travel, if the voicecoil rubbs or grates when you carefully push the cone down then shes possibly got bubbled coil glue and is deffinitely not going to sing.
all in all Id need to know its model number,it will be simillar to ts-wx80 or something like that..... Then i can tell you what its meant to read.

if you still need to know that is, after almost a year