Buying Used Subs?

Well I recently got screwed over big time for a 12" Eclipse SW8122DVC sub I purchased off LetGo and could use some advice on buying used subs. I'm somewhat new to car audio and thought usually if you compress the cone and hear a scratching sound then it's no good. Well I was a jackass and didn't fully hook it up and test it cause I at the time I had no amp so I figured if it doesn't make noise by compressing the Cone then it's good... Well was I wrong. I hooked it up and got nothing. At first I thought maybe the amp is no good since I got it used also but I removed the quick change magnet, looked inside the aluminum former that the voicecoils wrap around and it was ripped, or cracked 75% or so around it...The guy never responded back to me so what I'm getting at is, what tests can I do to used subs to make sure this doesn't happen again? Multimeter, or what? Thanks for the help in advance.

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How much was it ?

A 9 volt battery and some speaker wire.

honestly i wouldn't buy a used sub i couldn't hear 1st.. i got a brand new sub that had loose surround on it (no glue) so no way i would trust a used one i couldn't hear.. maybe if it was from a few of the guys on here would be only time i would trust it..

multi-meter, read the ohm loads of each coil, if its a dual 4 ohm each should read between 3.6 to 4.2, anything higher means the coil is pretty worn down. Do the scratch test, smell the coils for any funky smell, and a 100% play the sub free air to hear any mechanical noises.

To bad shipping is so bad. I've got the same sub is good shape sitting is storage with good coils

I recently sold a used sub, cheap. Nothing to brag about but served me fine for a few yrs until I was able to buy something better. So the easiest things to test a sub is a DMM and of course the ever famous never fails old school method of a battery check. A few short strands of speaker wire and a reg battery, like one your flashlight uses, is just fine.

if its a dual 4 ohm each should read between 3.6 to 4.2, anything higher means the coil is pretty worn down.

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So a copper coil "wears out" and gains a higher DC resistance? I'm dying for you to try to explain this one.

So a copper coil "wears out" and gains a higher DC resistance? I'm dying for you to try to explain this one.

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I actually cant, its just something I see happen from my buddy's setup where they tend to clip the setup(despite my warnings and clear instructions not to) a lot and a year they said the sub isn't anywhere near as loud as it once was. Coils look a bit darker, Checked the impedance, it went from 1.8 ohms on both coils when I first installed it to 2.4 ohms on one coil and 2.3 on the other. Reading is the same through several different multi-meters and there was no resistance on my multi-meter. The sub died out a few months later with only one coil working reading 5.2 ohms.

I would guess the copper is not as conductive when its at the point where its burning out hence you get higher resistance? I'd probably need to read up on it or if you can explain that'd be swell too.

Could be the coating on the copper is compromised by excessive heat thus shorting between tightly wound wires. I’m going to assume this is the same coating you get on many copper coils such as those found in electric motors and ignition coils. This also explains what Jeff said.

yeah when we cut out the sub, no slinky, just coils are extremely dark and no these werent anodized aluminium, they were bright shiny copper at the start.

Could be the coating on the copper is compromised by excessive heat thus shorting between tightly wound wires. I’m going to assume this is the same coating you get on many copper coils such as those found in electric motors and ignition coils. This also explains what Jeff said.

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IF a few turns were shorting out you would have less not more resistance.

I actually cant, its just something I see happen from my buddy's setup where they tend to clip the setup(despite my warnings and clear instructions not to) a lot and a year they said the sub isn't anywhere near as loud as it once was. Coils look a bit darker, Checked the impedance, it went from 1.8 ohms on both coils when I first installed it to 2.4 ohms on one coil and 2.3 on the other. Reading is the same through several different multi-meters and there was no resistance on my multi-meter. The sub died out a few months later with only one coil working reading 5.2 ohms.
I would guess the copper is not as conductive when its at the point where its burning out hence you get higher resistance? I'd probably need to read up on it or if you can explain that'd be swell too.

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The only thing on a speaker that could possibly partially fail adding resistance that I could imagine would be the tinsel which is made up of tiny thread sized wires.... if most of those were broken you might have higher resistance but even then I'd more suspect a problem with the DMM or something else like trying to measure in a noisy place or with some wind coming in the door. A coil is just solid 18.5 or thinner wire and copper/aluminum doesn't change its resistance with use and if it's burnt it'll burn open. Another thought would be the coil is open and is actually beginning to unwind and the broken bits are both touching the top plate and making the circuit through that.

I believe your experience with the resistance is something else, but if nobody can think of any science based explanation I'd consider this a red herring.

IF a few turns were shorting out you would have less not more resistance.

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O-yeah you’re right. Stupid me!

Well I recently got screwed over big time for a 12" Eclipse SW8122DVC sub I purchased off LetGo and could use some advice on buying used subs. I'm somewhat new to car audio and thought usually if you compress the cone and hear a scratching sound then it's no good. Well I was a jackass and didn't fully hook it up and test it cause I at the time I had no amp so I figured if it doesn't make noise by compressing the Cone then it's good... Well was I wrong. I hooked it up and got nothing. At first I thought maybe the amp is no good since I got it used also but I removed the quick change magnet, looked inside the aluminum former that the voicecoils wrap around and it was ripped, or cracked 75% or so around it...The guy never responded back to me so what I'm getting at is, what tests can I do to used subs to make sure this doesn't happen again? Multimeter, or what? Thanks for the help in advance.

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Sorry to hear what happened to you. Just wondering by chance where you purchased the sub as I too have been looking at purchasing another Eclipse sub that's why and I'm also located in SoCal, in the LA area.

Also, if you're still interested, Whitehorse Customz in Montebello is/was(?) selling a brand new 12" Eclipse SW8210 for $100. Don't know if it's DVC or SVC.