Possibly damaged subwoofer

[Dubizzle]

Hi all.
New member here seeking your advice.

I'm not an expert but i did readings before posting here, So please excuse me if im missing something and excuse my English as im not native English speaker, ill do my best to explain.

I bought second hand alpine subwoofer online model number X-W12D4, Which has dual 4 Ohm voice coils.

im planing to use it for a home theater build with a Yamaha p7000s Amplifier.

My concerns started when i checked the subwoofer with multi meter, Two actually to clear any doubts ( I Know ive should did it at the time of purchase but unfortunately i didint )

According to the manufacturer specs the subwoofer is dual 4 Ohm voice coils, Which i can never read across all terminals in all ways, This subwoofer has jumper that can be shifted in different positions which makes me more confused.

To make me more confused, The online installation manual shows one configuration with 2 Ohm stated on one of the connection methods.

The best reading i could get was around 2 Ohm across all terminals with all the jumper inserted position and without it being inserted, Is that normal or the subwoofer is fried?

I Know as well and from my readings if the speaker impedance is less than the amplifier recommended impedance will result in higher current flow ( Ohm law ) Which will result in either the amplifier, Speakers or both damage ( Correct me if im wrong )

I tried hooking the alpine subwoofer to the terminals of my Definitive technology subwoofer momentary to prevent any damage for its amplifire circut as the Definitive technology driver impedence was 8 Ohm and the alpine woofer produced sound.

Kindly advise me why im not getting the manufacturer specs regarding the voice coils impedance.

Sorry for the long talk, But im deeply concerned that the used subwoofer i bought is blown.

Click to read more...

 

[Buck 5,000+ posts]

Dual 4 ohms will either be 2 or 8 ohms final load (parallel or series). Does each coil read 4 ohms by themselves? There’s gotta be a way to read that. Can you post a pic of your issue with the jumper thing and hooked up to an ohm reading meter?

 

[audiobaun 5,000+ posts]

Pull the sub and set it on the Kitchen table and check Each coil on Ea sub with a DMM with Fresh Batteries.

 

[Dubizzle]

Hi again
Thank you guys for the reply.
Alright:

First the jumper and how does it look like:

The digital multy meter i have is acualy brand new which i bought particulaly for this purpose.
Ive tested it on another monitor audio driver that i have to confirm the readings and the multy meter readings are correct, im using the peep mode with 200 Ohm range:

Monitor audio driver readings:

Now the alpine readings:

With jumper removed:

With jumper inserted in parallel position:

i forgot to take photos measuring each voice coil in this position but the readings were similar

 

[Dubizzle]

With jumper inserted in series position:

Any thoughts on those readings?

 

[Jimi77 5,000+ posts]

Looks good to me.

 

[Dubizzle]

Looks good to me.

Hi jimi77

How come while its below the factory specs?

Please advise and will i have issues when its connected to amp that is rated at 8 or 4 Ohms?

 

[1aespinoza 10+ year member]

Hi jimi77

How come while its below the factory specs?

Please advise and will i have issues when its connected to amp that is rated at 8 or 4 Ohms?

You are good to go. Subwoofer voice coils usually read below their rated resistance. Once the coil begins to move, magnetic inductance will cause an impedance rise. All this is factored into circuit design so no need for alarm. This is how you test thise coils- For Parallel

For Series

Edit- Yours is a dual 4 Ohms! Something is wrong here. Remove the jumper and test each coil. Each should be close to 4 Ohms. It is reading as a dual 2 Ohms.
I just scrutinized the pictures, definitely a bad coil.

 

[Buck 5,000+ posts]

With jumper inserted in series position:

View attachment 40347

View attachment 40348View attachment 40349


View attachment 40350



Any thoughts on those readings?

I would put the probes on the top metal things above the whole jumper block or whatever, where it looks like there’s maybe solder. I would measure both of those, as those may be each individual coil wire. You need to measure the coils individually before they go into that jumper-block thing, IMO. That whole jumper device just is over complicated lol, to me.

 

[Buck 5,000+ posts]

If you use the ohm measuring mode that makes a noise when it’s a full circuit, you can use that to see if one coil or the jumper device isn’t completing the circuit, because it won’t beep without a closed circuit.

Side note: that is an interesting surround design.

 

[hispls 5,000+ posts]

Sounds to me like the woofer is fine and OP just needs to figure out how to set the jumpers to series the coils (if this is even an option?).

 

[hispls 5,000+ posts]

Sounds to me like the woofer is fine and OP just needs to figure out how to set the jumpers to series the coils (if this is even an option?).

 

[Jimi77 5,000+ posts]

You are good to go. Subwoofer voice coils usually read below their rated resistance. Once the coil begins to move, magnetic inductance will cause an impedance rise. All this is factored into circuit design so no need for alarm. This is how you test thise coils- For Parallel
View attachment 40358
For SeriesView attachment 40359
Edit- Yours is a dual 4 Ohms! Something is wrong here. Remove the jumper and test each coil. Each should be close to 4 Ohms. It is reading as a dual 2 Ohms.
I just scrutinized the pictures, definitely a bad coil.

I noticed that, but the coils aren't reading open or short, so I assume it's 2ohm DVC that's mislabeled.

 

[1aespinoza 10+ year member]

I noticed that, but the coils aren't reading open or short, so I assume it's 2ohm DVC that's mislabeled.

Probably not, because without the jumper they should read about the same. If they both would have read 1.3, you would have been good to go. Are those screws snug? Thats the best way for a good reading. Like Buck suggested, if you have access to the actual wires, give that a reading. You may get better results

 

[Jimi77 5,000+ posts]

Probably not, because without the jumper they should read about the same. If they both would have read 1.3, you would have been good to go. Are those screws snug? Thats the best way for a good reading. Like Buck suggested, if you have access to the actual wires, give that a reading. You may get better results

For some reason, I thought both coils read ~.6ohms, but reviewing the pics, one is at 1.3 and the other at .6 - not a good sign.