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I've opened the back of the exemplars!


illbarto
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Hi Guys,

I opened up the back of the exemplars because I heard something rolling around when I moved the tweeter cabinet to clean behind the speakers. 

The attenuator (?) has come loose and the postive has fallen off, problem is there are three tabs on the attenuator, does it matter which one it is soldered back on to?

A little explanation of what's going on here would be nice too!

 

IMG20200823100946.jpg

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G'day @illbarto

 

From the picture it looks like one terminal has solder and the other looks clean... I would assume it was connected to the middle terminal.

 

I'm new to speaker building, and yet to tackle any crossovers until I have some software and a microphone to measure things... unfortunately I can't help with what's going on there... but I'm sure you will have informative responses very soon.

 

Cheers.

Ant.

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12 minutes ago, Jventer said:

the soldering in that photo does not look good. 

Looks like my soldering ( it ain't mine ), which needs a lot more practice.

I've started reading and watching videos posted by another member ( name escapes me right now - sorry ), and found them most helpful.

 

I recently sent some crossovers to @Tubularbells  for upgrades.  I had re-done the internal wiring and I was most embarrassed about my soldering.

Edited by BuzzzFuzzz
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It does look like it should be soldered to the middle tab but in the other cabinet it is soldered to the tab furtherest away.

I guess during this melbourne lockdown I'll have to have a go at the soldering myself!

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12 minutes ago, BuzzzFuzzz said:

I'm out the door for work in a minute, but will locate the soldering info for you this arvo.

Thanks buzzzfuzzz, now that I've seen the insides i might have to track down someone in Melbourne to tidy it all up for me so i can move on with my life.

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Geez that does look rough as guts doesn't it? The centre terminal on the pot (potentiometer) will be the wiper, so you need one wire to the wiper, and one to either end of the pot, depending which way around you want the knob to work. ie clockwise more, or clockwise left. Presuming it is a linear pot of course.

 

In the case of your pic, red wire to centre tab on the pot. The other speaker will have similar. One wire to centre, the other to one end of the pot. Unless of course it has been wired up incorrectly, which is possible looking at the rest of the work.

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1 hour ago, bob_m_54 said:

Geez that does look rough as guts doesn't it? The centre terminal on the pot (potentiometer) will be the wiper, so you need one wire to the wiper, and one to either end of the pot, depending which way around you want the knob to work. ie clockwise more, or clockwise left. Presuming it is a linear pot of course.

 

In the case of your pic, red wire to centre tab on the pot. The other speaker will have similar. One wire to centre, the other to one end of the pot. Unless of course it has been wired up incorrectly, which is possible looking at the rest of the work.

Thanks Bob _m.  This is what is confusing me, in the other speaker the wires are connected up on the 1st and third tabs but on this one it looks like the 1st and second tabs.  what would be the result of incorrect wireing or a disconnected wire in this case?

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In the case of your picture, there would be no current through the pot, and the smaller 12ohm? resistor. Without knowing how the pot and resistor are connected in the circuit, I can't say what the resultant outcome would be. But turning the pot will have no effect.

 

Connecting the red wire to the centre terminal will allow changing the total resistance of the circuit from red wire -> pot -> white wire -> black resistor, from the value of  black resistor only, variable up to the total of the back resistor and the full resistance of the pot. (actually it would be a rheostat in this configuration).

 

Connecting the red wire to the opposite outer terminal will give a fixed resistance through red wire -> pot -> white wire -> black resistor, of the total of both black resistor and the pot. Turning the knob will have no effect.

 

Another way it can be connected is red wire to one outer terminal, white wire to opposite outer terminal, and a shorting link between the centre terminal and one of the outer terminals. This will have a similar operation to the first situation.

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Thanks guys, mental crises averted. I guess the volume pot (that Ive never used) hasn't been working the entire time I've had the speakers.

It does peak my interest to get it operational and have a play with the tweeters though!

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