Auto woofer

I took the back of my back seat out of my car and was surprised to see that I have a woofer!

It has 4 wires running down the cone, two on each side. Is that because it has 2 voice coils, one for the left channel and one for the right? So it can combine the signals audibly but not electrically, because if they mixed here, they would get mixed on all the other speakers too?

But couldn't they do that in the woofer amplifier and use a standar speaker with only one voice coil?

Also one pair of wires, unplugged from the car, has 32 ohms between them, and the other pair has 2.5. That's a bad sign, isn't it?

I wish I'd noticed this before I spent $25 for a new foam surround, but the I bought that before taking the speaker out, and since the speaker was facing me, I couldn't see this.

How good do you think it will sound with only one channel? Will I keep steering the car towards the side of the road?

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That could be. Dual-voice-coil woofers are fairly common.

An advantage to using them, is that you can use a 2-channel audio amplifier (left and right), run each channel through a crossover, and then feed each channel's "woofer" signal to a separate voice coil on the woofer.

You can certainly do the trick you're thinking of, but it would require an amplifier with at least three channels (left, right, and woofer) and would require that the woofer-to-mid/tweeter crossover be performed prior to amplification. There are certainly audio setups which work this way, but they're somewhat more of a "custom" job.


Another possibility is that what you have is a specialized woofer, meant for use wiht an active-feedback "servo" amplifier. One wire pair (and coil) would be the actual "driving" voice coil... probably the one with 2.5 ohms DC resistance (a 4- or 8-ohm nominal impedance at audio frequencies). The other coil would be a "sense" coil, whose output would be proportional to cone velocity.

A servo amplifier would use feedback from the sense coil to control the output to the voice coil. This approach can allow the amplifier to provide deeper bass with a flatter frequency response, without requiring a critically-tuned enclosure for the woofer.

You'd probably need to find a model number on the woofer, and look up the data sheet, to figure out whether you have an actual problem (open or shorted voice coil) or a servo-amplified single-channel subwoofer.

Inspecting the wiring at your amplifier or head-end unit would also be instructive. Check to see if it has two outputs for the woofer, or a single woofer output and a "sense" or "feedback" or "servo" input for the other pair of wires.

No, but if you use it to listen to the radio, you might end up being pulled either towards right-wing talk radio or left-wing NPR/APR stations :-)

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Dave Platt

This is all very interesting. I understood most of it but will read it one or two more times.

Actually I have the model number because the Simply Speakers kit to repair in includes the model number, for my make, model, and year car, and tomorrow I'll go hunting for into.

I'm not sure how to get the amp out of the car or where I could look at it. It's behind the back seat, and attached somehow.

But I did look more closely at the speaker and alas, the wire to the

2.5 inch coil has been cut. At first I thought it just broke off, but the end shows no wire, both ends show some of the red insulation, and the wire is now 1 or 2 mm. too short to reach the other piece. I could pull some through the zip tie, but plainly the last guy thought this voice coil was a problem. And after he cut the wire, then he unplugged or never plugged in the speaker.

I had hoped the speaker was just never plugged in at the assembly plant. I had a 1965 car which had big fresh air vents at the driver's and passenger's outer ankle, but no fresh air. When I had time to take off the kick panel, I saw that the cable was never connected to the doors. Also, my brother couldn't pull the car away from a stop without lurching forward. I thought he didnt' know how to drive. After he gave me the car, it took a couple months before I found that the wire to the vacuum advance was missing. The T- connection was hidden behind something else, and only because I had climbed up on something to get to the middle of the engine compartment did I notice this. Adding a hose made everything good. But no such luck with this speaker.

I will repair it tomorrow or Friday and install it anyhow. I have wireless speakers working off my PC and two are the left channel and two are the right, and they are in 4 different rooms. More to the point, I didn't notice that one of my two desk speakers was not working. About 1 song in 30 or 40, I couldn't hear the singer. Maybe that was what made me put my ear next to the other speaker and learn that it was dead!

So apparently my standards are low, and I might like a one channel woofer.

That does sound dangerous.

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I looked for the specs, and found about 78 hits for the model number, but all of them were selling refoam kits or junkyard speakers or speakers from Toyota dealers. I found the same refoam kit I bought, from Florida, for sale in Russia and Israel too. None of the pages were JBL or any of the manual download sites.

And I went to the JBL pages and nothing there.

I think the model number was used only in speakers sold to Toyota.

And add to that that it's a 9" speaker. Not common iiuc.

JBL 86160-AA310 if you think I missed it. But the specs are an academic question now. Either it sounds good or it doesn't.

Anyhow I finally glued it today. The glue they included was really good. I wish I knew what it really is. I doubt they'll tell me but I still have quite a bit left and I waste too much time on the computer now and don't do as many repairs.

Glueing went well, as they promised -- I watched the video twice, and sent them a question in the middle of the night which they answered before 9:30 in the morning -- but we'll see tomorrow how it sounds and if the voice coil rubs. I think the coil's centered but the surround is not quite centered in the metal frame. It was when I laid it out without glue. Dunno what happened, but it shouldn't matter.

The glue is clear, in a tube and goes on like Duco cement used to but it gets sticky in 30 seconds or so, and sticks well in 2 minutes, but if the pieces aren't together yet, you can still push them together.

Here's their glue page

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Not sure what the first three are but the one included with foam is the 2nd row on the right. $8 for a tube that's 4" long (the white part). plus $3.64 first-class postage. I'm sure someone sells the original for much less money, but if I can't find it, it might be worth paying them just for glue, for other projects. It's that good.

While Home Depot seems to be selling fewer glues (and Ace Hardware selling many) I was at a fabric store and they had a bunch of possibly new glues

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I was reading some crafts webpage and everyone raved about Aileene's Tacky Glue. They make another one that's not Quick Dry, and Jo-annes sells a set of 3 little bottles of different products. Plus another set of 3 other ones. Enough to see if you like them. I forget how many, 2 to 4 of them are especially for sewing, but the other 2 to 4 are for anything. Neither set of 3 is on their webpage! and they sell all 6 products in bigger bottles and I don't think a couple of the 6 are on their Aileene's search page.
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I guess you have to go to the store to see them all. But I don't especially think any glue at Jo-annes is the speaker glue, except for the word Tacky, which does seem closely related. Still, I only mention that store because it has glues I haven't seen before.

Maybe that's the difference between their kits for $25 to 22.50, depending where you buy it. Versus the company that charges 12 iirc, maybe the glue isn't as good. Or the video?

I don't have the name in front of me but I also found a page with a mach broader selection of speaker parts, grill cloth, metal grills, speakers with crossovers but no cabinet, for mounting in the wall perhaps. etc. etc.

I read that foam started being used in the late 60's iirc but it only lasts 20 years. This car is only 16 years old, tan top, white car, never gets that hot inside, and it looks like the foam has been gone for at least a year.

OTOH, I have speakers with paper surrounds instead of foam from the '30's. Still in great shape. I suppose they'll say they restrict the sound. But at least you don't have to replace them in 15 years.

My other car speakers are good I think, and they're just as old. I took one door speaker out and didn't notice anything. I'lll look again when I find it to put it back in. They're smaller of course.

Maybe they don't use foam.

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What should I do now? I measured again and both sides had 31.2 ohms. I'm sure one side was 2.5 ohms last time. I check more than once, esp. when the two numbers disagree. But I've been moving the cone up and down by hand a lot, as part of centering, glueing, and squeezing. And a couple days ago for the first time, I turned the speaker over** and it says 4.6 ohms.

So should I solder the cut lead back to the speaker? Unfortunately, I didn't note if that was the 2.5 ohms part or the 32 ohm part the first time.

If the resistance is higher than it should be, that's safe for the amp etc. is it not? But if there's an intermittent short and it goes down to 2.5 when it should be 32, that risks damaging the amp, right?

But if it damages the amp, won't it damage only the side that I wouldn't be using anyhow if I leave the wire cut?

How much importance should I give to the fact that someone before me cut that wire?

A replacement speaker for 100 to 200 is out of the question. I'm keeping the car at most 2 more years and if I find a nice car sooner, I'm buying that.

** it's magnet is v. heavy and that keeps it upright, and I'm always afraid I'm going to drop
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Mostly never mind. Dave, you weren't here in my crisis, so I went ahead without you.


That is, I installed it anyhow. I tried to do it before it got sun got bright and hot, but I'd forgotten to glue the 'gasket' to the front**.

And I had to let the glue dry and it took a few minutes to solder the cut wire.

I only played it a couple minutes with talk and it sounded okay. Too hot to go for a drive; this evening.

Could it have read low ohms because the voice coil moved from the center and touched something on the side the hole? It's been decades since I tore apart a speaker, but I think it was metal on both sides of the coil.

Or if the ohms are high, 31 instead of 7 or 4, how come they're both the same amount of high, now?

** (It doesn't do anything much, because the speaker doesn't touch anything in front of it, but maybe it will help keep the foam from detaching, and I don't know where else to put the gasket ring.)

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if speaker ohms doahn match amp ohms then the mismatch will blow the amps output circuit ....

speakers are cheap.


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glue is not glue....glue is ADHESIVES search: adhesives...there's a sheet.

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I'm sure I posted NeverMind to my first crisis post, but I don't see it coming back to me. I posted a couple hours after the first one to say that I installed it anyhow, Tuesday morning. Then Tuesday evening I went for a drive and the speaker is great. It booms like crazy. When I get the seatback back in place, it will be muffled a little bit, so it will be more balanced with the other rear speakers.

I don't know how you mean that. They don't last long; they're cheap to make; cheap to buy, they break easy? If you made the voice coil heavier, the speaker would not be as responsive, I think. This speaker is not cheap, lists at $260, sells for about $200.

There are 18,000 hits there. I wouldn't know which one to read.

I'm sure there are more than 18,000 hits on adhesives. Even harder to know which one to read. Everyone knows what is meant when someone says glue. And why do you think glue is not glue? How does it differ from adhesives?

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