Anyone know what this contraption could be ?

amplifiers, receivers and loudspeakers
Adamo0926
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Anyone know what this contraption could be ?

Post by Adamo0926 » 21 Jul 2019 19:59

I was putting the original Ohm C2 tweeters back into my C2s (I had been using the upgraded tweeters I ordered from Ohm since I had only one working original tweeter, but I was able to find a couple of basically new original tweeters on EBay from a former parts rep for Ohm up in Canada). I wanted to see if there was any difference in sound characteristic.

Anyway, the tech guy I bought the speakers from had originally installed the upgraded mids and tweets I had ordered from Ohm. When I took out the first tweeter I discovered it had been wired with the polarity reversed, the other tweet was wired as Ohm suggests, green wire to positive, black wire to ground. He had the green wire connected to the ground connector not the positive connector. And this guy is allegedly a tech !

Anyway, since those were wired incorrectly, I thought I would double check the mids. When I took both mids out I found the following (see the attached pictures). The wire from the crossover is not connected directly to the drivers terminal, but to another wire that has something (fuse ? resistor ?, etc ?) that is wrapped up tightly. I wasn't about to unwrap it to see what it was, though I suppose I could do that. Then the end of that wire with whatever is wrapped up is soldered onto the terminal of the mid range driver. The same contraption is on both mid range drivers.

I know for a fact that this is not how Ohm wired it because I removed the drivers from my friend's C2s which were totally originally and he is the original owner. And there was no such wiring in his speakers. I don't know if this is something that was done by the tech guy that sold me these C2s, or if they were like that when he got them from whoever he got them from. But obviously someone did some tinkering for some reason.

Can anyone hazard a guess as to what this might be ?

It seems like each day brings a new adventure with this insidious hobby....
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gofar99
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Re: Anyone know what this contraption could be ?

Post by gofar99 » 21 Jul 2019 20:35

Hi, without actually measuring it ...I would guess a fuse. Likely put there to keep from frying the driver. Another possibility is a resistor as the replacement driver might be more sensitive and put out more sound than the originals and this would pad it down a bit. Just guessing, if you measure across it with a meter it would show if it was a fuse (pretty low resistance, perhaps 1 ohm or less) or an actual resistor (some value likely in the 2-25 ohm range typically.)

Adamo0926
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Re: Anyone know what this contraption could be ?

Post by Adamo0926 » 21 Jul 2019 22:06

gofar99 wrote:
21 Jul 2019 20:35
Hi, without actually measuring it ...I would guess a fuse. Likely put there to keep from frying the driver. Another possibility is a resistor as the replacement driver might be more sensitive and put out more sound than the originals and this would pad it down a bit. Just guessing, if you measure across it with a meter it would show if it was a fuse (pretty low resistance, perhaps 1 ohm or less) or an actual resistor (some value likely in the 2-25 ohm range typically.)
Is that all it takes to protect a speaker driver ? Just adding a fuse to the connection from the crossover to the positive speaker terminal ? If it's that simple you would think that every mid and tweeter would have fuse protection. How would you know what type of fuse to use with the connection ?

I tend to think it is your guess of a fuse. The C2s already have attenuator switches on the back to adjust both mids and tweeter drivers. So why would someone go through all the trouble of adding a resistor when there must ones built in already to adjust the mids and tweeters for O db, -3 db and -6 db ?

Alec124c41
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Re: Anyone know what this contraption could be ?

Post by Alec124c41 » 21 Jul 2019 23:25

Sometimes a mid or tweeter will be much more than 3 or 6 db more sensitive than the woofer, and will need some serious cutting back to make it compatible.
The first speakers I built, 3-ways with Philips drivers, had the AD160-t8 tweeters, and were harsh, before I put a 10 Ohm resistor across it. I also added L-pads.

Cheers,
Alec

Adamo0926
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Re: Anyone know what this contraption could be ?

Post by Adamo0926 » 22 Jul 2019 03:22

Alec124c41 wrote:
21 Jul 2019 23:25
Sometimes a mid or tweeter will be much more than 3 or 6 db more sensitive than the woofer, and will need some serious cutting back to make it compatible.
The first speakers I built, 3-ways with Philips drivers, had the AD160-t8 tweeters, and were harsh, before I put a 10 Ohm resistor across it. I also added L-pads.

Cheers,
Alec
Hi Alec....the replacement mid-ranges that were installed I ordered directly from Ohm Acoustics. They are upgraded mid-ranges designed specifically for the Ohm C2s, so they have the same specs as the original mid-ranges. I can't see where there would be any need for a resistor to be put there since the attenuator switch on the back should be just fine for adjusting the out put of the mid-range. I also don't think the tech that I bought them from did this bit of tinkering. I think when he got them this was already done.

But here is something interesting I just thought of. If that is indeed a fuse designed to protect the mid-range that is all wrapped up there, then I assume the mid-range could not be blown since the fuse would blow first, correct ?

If that's the case, when I first tested the speakers neither the tweeter or the midrange were working on one of the speakers. When I brought it back to the tech that sold them to me he tested the mid and tweet and said they were both blown. But how could the mid be blown if there was a fuse protecting it ? And if that is a fuse, if it were blown and not replaced wouldn't that prevent the new mid from working ?

So now I'm thinking maybe it is some kind of resistor, but like a previous poster said I can't be sure unless I test it with a meter.

And let me ask this as well....whether it's a fuse or a resistor why would it need to be wrapped up like a mummy like that ? Is there a reason for that ? If that's not essential I could just unwrap the thing and see what it is.

But I guess if the speaker sounds good to me wired as it is, I should just leave well enough alone instead of risking opening Pandora's Box.

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Re: Anyone know what this contraption could be ?

Post by Alec124c41 » 22 Jul 2019 04:25

Use a multi-meter to measure resistance of that piece of wire, from crossover to speaker end.
Also good for testing drivers for continuity, among other things.
Fuses are usually mounted next to the level controls, or on the back, so you can change them without tearing the speaker apart.
It could also be a capacitor, to filter out low frequencies, but that seems unlikely if the crossover is still there.

Cheers,
Alec

Adamo0926
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Re: Anyone know what this contraption could be ?

Post by Adamo0926 » 22 Jul 2019 05:18

Alec124c41 wrote:
22 Jul 2019 04:25
Use a multi-meter to measure resistance of that piece of wire, from crossover to speaker end.
Also good for testing drivers for continuity, among other things.
Fuses are usually mounted next to the level controls, or on the back, so you can change them without tearing the speaker apart.
It could also be a capacitor, to filter out low frequencies, but that seems unlikely if the crossover is still there.

Cheers,
Alec
If I really want to know could I just unwrap the thing and see what it is ? I think at this point since it doesn't seem to affect the sound in any adverse way maybe I should leave well enough alone. I'm just really curious about it.

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Re: Anyone know what this contraption could be ?

Post by theclosetguy » 22 Jul 2019 16:06

More than likely a self-resetting fuse. A value close to the max rating of the tweeter in watts. So if the tweeter was rated for 20 watts and you feed the system 30 watts the fuse would trip and after a short resting period would reset.
Mike M

Adamo0926
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Re: Anyone know what this contraption could be ?

Post by Adamo0926 » 22 Jul 2019 16:09

theclosetguy wrote:
22 Jul 2019 16:06
More than likely a self-resetting fuse. A value close to the max rating of the tweeter in watts. So if the tweeter was rated for 20 watts and you feed the system 30 watts the fuse would trip and after a short resting period would reset.
Mike M
Very interesting....thanks ! I learn something new every day on here. The "contraption" is actually on the mid, so I can assume what you said about a self-resetting fuse for the tweeter could also apply to the mid ?

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Re: Anyone know what this contraption could be ?

Post by Gravitar8 » 23 Jul 2019 12:57

Good post. I was just discussing phase with an audio noob a couple of days ago. Though that discussion was more about phase switches on mixing boards (why they are there and how they are used) I think phase is something that gets missed in our hobby. Though it seems like here, the focus of the thread is on a "mystery device" the underlying notion of phase is what led Adamo to investigate. I have no doubt that most (many?) speakers arrive properly wired and 'in phase' but there is always that chance they are not. More regularly in the pro audio world- things are more confusing. I've found microphones, microphone cables, effect devices, pre-amps, etc to be 'out of phase' and there is a reason why even some entry level tube microphone pre-amps have a phase switch- not only to compensate for multiple microphone setups (such as with an acoustic drum set) but also to 'fix' components that are 'out of phase'. Perhaps someone with more of an engineering background can straighten out this 'phase' sub topic and how it applies to audiophilia. Alec?

Alec124c41
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Re: Anyone know what this contraption could be ?

Post by Alec124c41 » 23 Jul 2019 14:14

I am not a trained electronic technician, but have some experience i building speakers.
If you have a woofer and a tweeter, both direct wired plus to plus, minus to minus, they will be in phase, but you will blow the tweeter out.
Put a capacitor in line with the tweeter to cut the lower frequencies, and the capacitor reverses the phase of the tweeter. Where the two speakers share bandwidth, the signals will cancel each other, so you reverse the wires to the tweeter, plus to minus, minus to plus, to restore the phase.
I have come across a few old 3-way speakers from a local manufacturer, in which the midrange was fed by a capacitor, but not reversed, putting the mid out of phase with the woofer and the tweeter. Apparently the maker thought that this would give a spacey sound, but the big suck-out of the middle frequencies was horrible.

Cheers,
Alec

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Re: Anyone know what this contraption could be ?

Post by Adamo0926 » 23 Jul 2019 16:12

Alec124c41 wrote:
23 Jul 2019 14:14
I am not a trained electronic technician, but have some experience i building speakers.
If you have a woofer and a tweeter, both direct wired plus to plus, minus to minus, they will be in phase, but you will blow the tweeter out.
Put a capacitor in line with the tweeter to cut the lower frequencies, and the capacitor reverses the phase of the tweeter. Where the two speakers share bandwidth, the signals will cancel each other, so you reverse the wires to the tweeter, plus to minus, minus to plus, to restore the phase.
I have come across a few old 3-way speakers from a local manufacturer, in which the midrange was fed by a capacitor, but not reversed, putting the mid out of phase with the woofer and the tweeter. Apparently the maker thought that this would give a spacey sound, but the big suck-out of the middle frequencies was horrible.

Cheers,
Alec
Alec....let me see if I understand this correctly. Does this mean in a 3 way system that crosses over to the mid and the tweeter that both the mid and the tweeter will have their phase reversed and both be out of phase with the woofer ? Does that also mean that to have all 3 drivers in phase you would either have to connect + to - and -to + on the woofer to bring it into phase with the other 2 drivers ? Or if the woofer is left at + to + and - to -, you would need to have both the mid and tweeter wired as + to - and - to + in order to have all drivers in phase ?

When manufacturers build a speaker do they have everything wired that takes all this into account and will have all the drivers in phase ?

You said that when drivers are out of phase, because one is moving in while the other is moving out you will have some cancellation of signal. Would this be audible to most people if anybody ? And if audible what would the audible difference be ?

When I discovered one of the tweeters in my Ohm C2 was wired in reverse, I talked on the phone with John Strobheen the President of Ohm and he said that would change the dispersion angle of the tweeter since the polarity would be reversed 180 degrees. He said that could mean you could hear a slight difference from the tweeter if you were standing up listening to the speaker as opposed to sitting down. He told me that Ohm always has things wired + to + and - to - (- to - is the ground, correct ?)

I find all of this very fascinating.

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Re: Anyone know what this contraption could be ?

Post by Woodbrains » 23 Jul 2019 20:47

Hello,

Like Alec, I have built a couple of sets of speakers and what he says is correct. Generally, a 2 way speaker with a crossover will usually (but not always) have the tweeter reversed to the woofer. A 3 way generally has the mid reversed from the woofer, but the tweeter back to pos to pos, neg to neg with the woofer. However, it is possible to series wire speakers, also, high order crossovers can mean that the speakers can sometimes remain in phase. Listening can tell you if something is wrong, as Alec pointed out.

I do strongly suspect that your tweeters should both be wired the same as each other, so someone might have inadvertantly swapped the wires in one cabinet. I would guess your 3ways should have the mid reversed and the tweeter the same as the woofer.

Mike.

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Re: Anyone know what this contraption could be ?

Post by Alec124c41 » 23 Jul 2019 23:35

It depends on the complexity of the crossover.
If you want to see what phase does, listen to a pair of speakers, then reverse the wires on the back of one of them and listen. Now put the speakers face to face, with a small space between them.
BTW if the last bit gives good sound in one of the driver ranges. then one of those drivers is wired wrong.

Cheers,
Alec

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Re: Anyone know what this contraption could be ?

Post by Woodbrains » 24 Jul 2019 00:07

Hello,

Regarding the contraption you are asking about: the green wrapping looks like heat resistant sleeve to me. So the component obviously generates some heat, so I think you might have a wire wound resistor or a choke, which will attenuate the driver or alter it's impedance, in that order. Obviously generating heat is unwanted in an enclosure that is presumably stuffed with some wool or similar material. If you carefully slip off the green sleeve, you will be enlightened as to what the component actually is, but be sure to replace it.

Mike.

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