Speaker coil winding

[J M Fahey]

Start by showing a couple speaker pictures, front , back, sideways (so we see the magnet).
How do you know itīs chinese?
Cut suspension and edge all around, cut tinsel wires, remove cone and voice coil carefully and post its pictures, looking at the coil, whether itīs complete or disassembled, charred, where are the toasted areas, I can reasonably "read" what happened to it.
Try not to leave bobbin pieces in the gap, youīll need to clean it well anyway.
You will need to measure coil diameter, height, winding length exactly; replacements wrong by a couple thousandths of an inch will "scratch inside" or "scratch outside" or plain noit fit in the gap, tolerance is that close.

Are you in or near any large city?
If you have to mail order everything it may be problematic, itīs not easy to mail Toluene or Acetone.

[anchor]

I am fairly close to industry in Frankfurt but the chemicals are still expensive.

[nosaj]

How about some pics of the said speaker?

nosaj

[J M Fahey]

I am fairly close to industry in Frankfurt but the chemicals are still expensive. I have an unrelated question about this website. I have clicked on links in recent posts and have been unable to access them. The dialog states I have insufficient priviliges. If this is a feature of the website and not a problem with my browser, how or when will my privilges be elevated to access these links?

Please post a detailed full list showing *all* links you canīt connect to.
Maybe itīs a problem about Member "being outside USA" ... which I also am.
So with your list I may try to access it from here.
Happened to me some times too, here and in other Forums, so I am not surprised.

As of the speaker, please post some pictures, *specially* one showing the gap, if possible close up sharp and well illuminated pictures showing what kind of debris is clogging it.
And some of the removed voice coil, to see how it burnt and how much it crumbled, show the burnt wire and from the inside of the former, to check whether it bubbled, melt, cracked or distorted.

IF you want to clone it, youīll need an aluminum, brass or iron core turned to exact dimensions, the one in "Video Rockola" will give you an idea about how itīs made and mounted.

[nickb]

I notice that in the video he may be confusing the DC resistance with the impedance. A voice coil DC resistance of somewhere around 6.5 ohms is typical for an 8 ohm speaker.

[Reader]

I notice that in the video he may be confusing the DC resistance with the impedance. A voice coil DC resistance of somewhere around 6.5 ohms is typical for an 8 ohm speaker.

I agree. I have the same thought. I'd also like to know just how you would design a voice coil for a specific impedance other than matching and old damaged voice coil turn for turn with the same size wire. For instance, when you send a speaker for recone you can ask for an impedance change. That is if it was an 8 ohm speaker you can ask for the reconer to install a 4-ohm voice coil when the speaker is rebuilt. How exactly do they do that?

[anchor]

Fur Reader:
I think going from 8R to 4R is only a matter of using fewer turns.

I will post some photos but there is not much to see. Even with a light, I cannot get a good shot of the voice coil. I was able to locate only one of the links I spoke of. Here it is below:
https://music-electronics-forum.com/...l=1#post514504

[nosaj]

Fur Reader:
I think going from 8R to 4R is only a matter of using fewer turns.

I will post some photos but there is not much to see. Even with a light, I cannot get a good shot of the voice coil. I was able to locate only one of the links I spoke of. Here it is below:
https://music-electronics-forum.com/...l=1#post514504

Pics will help so please show the basket and everything. Less turns possibly means different wire gauge also. Same gauge fewer turns means less power handling.

Where did you find the link? Cause you said " I have clicked on links in recent posts and have been unable to access them" So curious where you found the link.

nosaj

[J M Fahey]

I notice that in the video he may be confusing the DC resistance with the impedance. A voice coil DC resistance of somewhere around 6.5 ohms is typical for an 8 ohm speaker.

Well, yes ... "Rockola" is a quite crude site (technologically) but I praise them for rolling up their sleeves and doing it, and even more for providing all the data, PCBs, etc. plus tons of stepby step pictures and videos.
And they do not sell kits or transformers, do not ask for paid membership, anything $$$ , so they are quite altruistic in their area.

Yes, that winding "formula" applies just to *one* voice coil type and model, is useless for other diameters, winding lengths or impedances ... but at least cover 8 ohm 2" voice coil woofers, and is reasonably close for 2.5" ones, which cover most of the generic woofers they will ever meet.

"Build your own rockola" site in practice covers typical small town DJ needs, or Tropical Music dance bands PA, I bet both regularly burn a fair amount of woofers which to them are expensive to replace.

Of course 8 ohm DCR is high, but since he did not discount 1 ohm or so parasitic meter resistance, in the end both sort of compensate ; REAL DCR must be somewhat less than 7 ohm which is fine
Often, Ignorance is bliss

[nosaj]

Well, yes ... "Rockola" is a quite crude site (technologically) but I praise them for rolling up their sleeves and doing it, and even more for providing all the data, PCBs, etc. plus tons of stepby step pictures and videos.
And they do not sell kits or transformers, do not ask for paid membership, anything $$$ , so they are quite altruistic in their area.

Yes, that winding "formula" applies just to *one* voice coil type and model, is useless for other diameters, winding lengths or impedances ... but at least cover 8 ohm 2" voice coil woofers, and is reasonably close for 2.5" ones, which cover most of the generic woofers they will ever meet.

"Build your own rockola" site in practice covers typical small town DJ needs, or Tropical Music dance bands PA, I bet both regularly burn a fair amount of woofers which to them are expensive to replace.

Of course 8 ohm DCR is high, but since he did not discount 1 ohm or so parasitic meter resistance, in the end both sort of compensate ; REAL DCR must be somewhat less than 7 ohm which is fine
Often, Ignorance is bliss

i am not the OP is really with us. To get a shot of the voice coil means the speaker will have been dissected at this point , no?

nosaj

[anchor]

Same gauge fewer turns means less power handling.

What makes you believe this? A lower ohm rating should not change the amount of amps going through the wire if is the same gauge. You are correct observing that I have not removed the voice coil. I left it as I found it as I have not decided to fix it.

[eschertron]

What makes you believe this? A lower ohm rating should not change the amount of amps going through the wire if is the same gauge. You are correct observing that I have not removed the voice coil. I left it as I found it as I have not decided to fix it.

You are exactly right. Same current but fewer Ohms. Power = I^2 * R so fewer Ohms for the same current means lower power rating.

[nosaj]

You are exactly right. Same current but fewer Ohms. Power = I^2 * R so fewer Ohms for the same current means lower power rating.

Well isn't that what I said?
Quote Originally Posted by nosaj
Same gauge fewer turns means less power handling.

nosaj

[J M Fahey]

I will post some photos but there is not much to see. Even with a light, I cannot get a good shot of the voice coil. I was able to locate only one of the links I spoke of. Here it is below:
https://music-electronics-forum.com/...l=1#post514504

That makes two of us
I can not even see a link there, let alone open it.
I wouldnīt worry about that anyway, old stuff.

Fur Reader:
I think going from 8R to 4R is only a matter of using fewer turns.

Thereīs more parameters involved:
* coil diameter
* winding length
* actual wire diameter (which may or may not match what raw Gauge # indicates)
* number of turns
* insulation thickness
* copper or aluminum
* number of layers.
Usually 2 but some dome tweeters use only 1 (and made out of aluminum).
Some subwoofers use 4 layers.
* high performance PA speakers and horn drivers use a single layer of *edgewound* aluminum or copper ribbon.

That said, 99% speakers use 2 layers copper roundwire because all other options are orders of magnitude more difficult to make.

* Guitar speakers generally have short coils, same or 1mm longer than gap height, woofers generally are up to 2X as long, and some special high excursion subwoofers *up to* 4X gap length.

* Some supertweeters have coils *shorter* than gap length.

[nosaj]

What makes you believe this? A lower ohm rating should not change the amount of amps going through the wire if is the same gauge. You are correct observing that I have not removed the voice coil. I left it as I found it as I have not decided to fix it.

Then how did you expect to take a picture of it? Are you sure you know where the voice coil is? You'll have to remove the cone and the spider.

nosaj