What is 8+8 ohm, why two sets of terminals on woofer?

Hi, It is a DVC ( dual voice coil ) for the ease of wiring, so you can wire it parallel to 4ohm or in series for 16 ohm. ( most likely if you use two in a box and want it to be 8ohm, each woofer in series, 16 ohm, the two woofers in parallel ,8 ohm. )
Usually car subwoofers have dual voice coils.

Never use only one of it's coil , since it would be half the power it can handle. Also you can not wire stereo to it, let's say one voice coil on L and the other on R as it will cancel each other, no sound or very quiet and the voice coils cooking themselfes.

I have used in the past a car subwoofer by Pioneer, dual 4ohms, I used a stereo to mono, fed into an amplifier, and each coil on one channel, ( measured so the balance is perfectly centered ) it worked for a few years no problem, but I DO NOT RECOMMEND IT. if your amp isn't perfectly balanced it will destroy the woofer. anyway,
Cheers, Bruno.
 
it is a dual voice coil subwoofer.
Basically, summing stereo electrical to mono acoustical. The theory and practice is low frequencies are non-directional due to long wavelengths so just use one driver to handle that portion of the spectrum to save costs.
 
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you can not wire stereo to it, let's say one voice coil on L and the other on R as it will cancel each other, no sound or very quiet and the voice coils cooking themselfes.

https://jlaudio.zendesk.com/hc/en-us/articles/204374150-Speaker-Wiring-Tutorial
"dual voice coil woofers were developed so that a subwoofer or center speaker could be driven from the left and right channels of the average home stereo amp/receiver. Since sub-bass frequencies are hard to localize, the dual voice coil subwoofer allowed sub-bass reinforcement within one cabinet and one speaker. This cabinet could be placed inconspicuously in a corner or along a wall of the listening room. The obvious benefits to this are space-efficiency and lower cost than two independent bass cabinets or a larger cabinet with two subs in it. Many popular home subwoofer / satellite speaker systems still use this basic configuration."

https://techtalk.parts-express.com/forum/tech-talk-forum/45171-dual-voice-coils-in-stereo
"Is it perfectly ok to hook up a stereo L/R signal to a Dual Voice Coil woofer? . . . Yes. The funny thing is that was what they were originally created for, now there's people who say this can't be done."
 
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Basically:

The purpose of offering a woofer with 2x8 ohm configuration is to provide flexibility and compatibility with different audio systems and amplifiers. By having multiple voice coils, the speaker can be wired in different ways to match the specific requirements of the audio setup.
 
Never use only one of it's coil , since it would be half the power it can handle. Also you can not wire stereo to it, let's say one voice coil on L and the other on R as it will cancel each other, no sound or very quiet and the voice coils cooking themselfes.
If you're getting no sound, the VCs have been hooked up out of phase. One pair of leads needs to be reversed.
 
Ok, I only knew it was made for impedance flexibility so it can be wired parallel or series for different requirements, but if you send L and R to the same coil , if the left signal let's say wants to pull in and the R channel wants to push out at the same time, the voice coil would just sit in the middle.
 
but if you send L and R to the same coil
That should never be done because it shorts the two amplifier channels to one another and that is a great way to blow up the amplifier.
But a DVC driver has 2 completely separate voice coils so it is perfectly safe to connect two amplifier channels to the driver... unless the voice coils are linked together in series or parallel, then electrically the driver becomes the same as a single voice coil driver and only 1 amplifier channel can be connected.
 
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Wow I stirred up a hornets' nest, overwhelmed by all the responses!

Thank you so much.

So this now means I can just build one box for one driver, wire left and right speaker output from my amp to the subwoofer coil one and two, and I should have a decent subwoofer..., right? I should ideally have a low pass filter somehow though, a properly sized inductor?

I know I am over-simplifying things, but this is not supposed to become a high-end system... I just want a bit of ummmpf, more bottom end.
 
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Dual voice-coil subwoofers can be a little tricky. Now I can't find my book right now, but if you are going to do some simulations, the T/S parameters will change when you wire them in single-coil, parallel pair, or series pair.
I have a pair of old RS 12" "Subwoofer" 40-1350 DVC...as I simmed them for an enclosure I got radical differing results. Unfortunately both coils are rated at Four ohms each & in parallel they of course dropped slightly below Two ohms, the kind of load that would tend to "eat" amplifiers. Keep it simple, two channels, one channel per coil with a pair of big fat inductors to cut it off above 80 hertz or so.



---------------------------------------------------------------------------------------------------------------------------------------------Rick...
 
Ron E's DVC wiring chart:
RonE DVC Wiring Chart.PNG
 

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Dual voice-coil subwoofers can be a little tricky. Now I can't find my book right now, but if you are going to do some simulations, the T/S parameters will change when you wire them in single-coil, parallel pair, or series pair.
I have a pair of old RS 12" "Subwoofer" 40-1350 DVC...as I simmed them for an enclosure I got radical differing results. Unfortunately both coils are rated at Four ohms each & in parallel they of course dropped slightly below Two ohms, the kind of load that would tend to "eat" amplifiers. Keep it simple, two channels, one channel per coil with a pair of big fat inductors to cut it off above 80 hertz or so.



---------------------------------------------------------------------------------------------------------------------------------------------Rick...
Sounds good, especially the "Keep it simple" part :)

I will do some modeling and see what size box I'll need for this. It should fit under my desk.

Silly question but... what if I just use two, in the same box? Should have a bit more authority I suppose? Of course I would have to model the box accordingly.
 
You have a matching pair? Yipee! Do an isobaric-pair! If you do an isobaric-pair you can halve the volume of a sealed enclosure...The isobaric-pair in theory "cleans up" asymmetrical distortion anomalies. Use the "face to face" configured isobaric-pair, the smallest captured air volume best expresses the theory.
Considering the plentiful X-max of your driver pair, and the "flexible" Efficiency bandwidth Product, I would opt for a vented enclosure...to get the deepest of frequencies possible.

--------------------------------------------------------------------------------------------------------------------------------------------------------------------Rick...
 
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You have a matching pair? Yipee! Do an isobaric-pair! If you do an isobaric-pair you can halve the volume of a sealed enclosure...The isobaric-pair in theory "cleans up" asymmetrical distortion anomalies. Use the "face to face" configured isobaric-pair, the smallest captured air volume best expresses the theory.
Considering the plentiful X-max of your driver pair, and the "flexible" Efficiency bandwidth Product, I would opt for a vented enclosure...to get the deepest of frequencies possible.
Sounds interesting, but I can fit two separate 70 liter boxes behind my desk... I know some may laugh at me, but I do want my subwoofers in stereo :) They model quite nicely in a 72 liter box.
 
The inductance of the two identical voice-coils (Le) in parallel should be 0.001 Henries, not the identical values you have listed for the single-coil at 0.002 mH.
At a glance it would seem so, but Ron E explains why it's apparently not, though not educated enough to follow, so hoping you and/or others can 'dumb it down' enough or conclusively prove him wrong.