Can one use a Fluke 325 Multimeter directly on a HK tweeter? To check its not defective?

Submariner1

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Just checking out a few things before replacing the suspect HK Amplifier. (problem noted below)

Q. Can one use a self ranging multimeter directly on the tweeter to check its not burnt out or shorting? i.e. disconnect the wiring plug, and put the meter probes directly on the tweeter speaker terminals.

The range of this meter is
400.0 - 4000 - 40000 Ohms. I am hoping when it passes through a current to test the resistance, that current will be so low it won’t fry the tweeter.

Q. Does it matter which way around, and if so, is my memory correct that the Negative is normally the fatter terminal?

I know one technically really needs an AC Impedance Ohms Meter to determine the exact impedance of the speaker. As I dont have one, and know one can use a Multimeter to get a rough check on a ‘full range’ speaker; that will at least determine if its OL or dead shorting. (E.g. an 8 Ohm speaker may show circa 6 Ohms actual resistance and a 4 Ohm speaker may show 3 Ohms etc. ).

Note I am not trying to accurately verify the impedance, like one would when critically determining the load of a speaker circuit on an amplifier.
Just identify is this tweeter burnt out or intermittantently shorting?


Problem if interested:
Intermittently all the Speakers all go very quiet, but the left Tweeter gets very loud and has an overlay of loud distortion.

When it last did this, I gave the tweeter speaker pod a very hard slap, and it magically instantly all sounded perfect! And has remained working for 2 days!

Yes as soon as it break again I intend to have it put on STAR. Hopefully then to get the actual current fault code and any old stored ones. Not sure if it stores earlier wiring and amplifier fault codes.
 

LostKiwi

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You could always put a 100 ohm resistor in series with the speaker and just look to see the difference? The resistor will limit current to a very low value.
 

M80

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A simple multimeter won't do any harm.
As you say it being an impedance rated device I wasn't aware that the reading would be anything other than a near short, and as such will tell you it isn't open cct.
I would expect a reading of around 1 ohm.

But if it was open cct or indeed a dead short you wouldn't get any sound from it, and you do.
It's beyond my knowledge to say what would happen if it were drawing too much from the amp due to partial shorting.
My suggestion would be to disconnect it and see if the issue re occurs. While it will reduce the load on the amp, by a little, I would assume it will be after the crossover filter so I wouldn't expect the amp to notice.
 

Paul1948

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Sounds as if you have a dodgy contact, any multi meter will help you to trace the fault and cause no problem, this is the sort of problem that the multimeters are designed for, this heavy engineering compared with what I use them for. good luck finding the fault.
 
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Submariner1

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A simple multimeter won't do any harm.
As you say it being an impedance rated device I wasn't aware that the reading would be anything other than a near short, and as such will tell you it isn't open cct.
I would expect a reading of around 1 ohm.

But if it was open cct or indeed a dead short you wouldn't get any sound from it, and you do.
It's beyond my knowledge to say what would happen if it were drawing too much from the amp due to partial shorting.
My suggestion would be to disconnect it and see if the issue re occurs. While it will reduce the load on the amp, by a little, I would assume it will be after the crossover filter so I wouldn't expect the amp to notice.

Hmm I thought the resistance reading was usually about 15% less than the true impedance reading (of course that in itself is for a given frequency)
So of its a 8 Ohm speaker 6-7 Ohms , a 4 Ohm speaker circa 3 Ohms
Interested why You would be expecting circa 1 Ohm ?

I agree on your point regarding hearing sound. One of my thoughts was, if it was in fact rapidly making and breaking contact? ... hence the scratchy distortion/arcing like sound.

There appears to be only one harness connector/plug on EPC; whereas it correctly says there are 2 tweeters, I assume thats a mistake?
I was thinking of getting a new harness plug, when I get the new tweeter ... more to eliminate a possible poor connection than anything.
 
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Submariner1

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Sounds as if you have a dodgy contact, any multi meter will help you to trace the fault and cause no problem, this is the sort of problem that the multimeters are designed for, this heavy engineering compared with what I use them for. good luck finding the fault.

Thanks
I do find intermittant faults very irksome.
 

M80

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Hmm I thought the resistance reading was usually about 15% less than the true impedance reading (of course that in itself is for a given frequency)
So of its a 8 Ohm speaker 6-7 Ohms , a 4 Ohm speaker circa 3 Ohms
Interested why You would be expecting circa 1 Ohm ?

I agree on your point regarding hearing sound. One of my thoughts was, if it was in fact rapidly making and breaking contact? ... hence the scratchy distortion/arcing like sound.

There appears to be only one harness connector/plug on EPC; whereas it correctly says there are 2 tweeters, I assume thats a mistake?
I was thinking of getting a new harness plug, when I get the new tweeter ... more to eliminate a possible poor connection than anything.

My tweeters are plugged into the woofers, and they are fed from the head. I thought yours might be the same but you have the HK so I guess configured differently.

I'll have a play on speakers I have in the loft. I seem to remember that the resisitance of the coils on speakers were very low when I tested previously, I'm interested to learn if different.
Aren't your speakers 4 ohm?
 
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Submariner1

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My tweeters are plugged into the woofers, and they are fed from the head. I thought yours might be the same but you have the HK so I guess configured differently.

I'll have a play on speakers I have in the loft. I seem to remember that the resisitance of the coils on speakers were very low when I tested previously, I'm interested to learn if different.
Aren't your speakers 4 ohm?

I am not sure how these speakers are configured, I assumed they were all driven from the Amp via on board cross overs. I can see capacitors on the tweeter in an ebay photo.

I just assumed they would be 4 Ohm speakers with maybe 8 Ohm tweeters.
See pic off eBay of my HK tweeters
44ECA2EF-676D-4663-BA62-6163280F6FB2.jpeg
I cant see the Ohms value in this pic ... but I am pretty sure that is a capacitor on the positive terminal, this would stop any low frequencies but its not exactly a sophisticated 2nd or 3rd order crossover ... very basic.
So Imwould imagine somewhere else is a more exacting crossover, maybe in the Amp output stage??

As an aside, can you imagine a CL500 with that revolting colour interior trim OMG ... you couldn’t even sell that to a drug dealer in Lagos! :):):)

If I measure my old Subwoofer, labelled as 4 Ohms impedance they measured something like 3.4 Ohms if memory serves me well.
And I was told by a pretty clued up audiophile, that they generally measured in resistance terms about 15% less thsn the rated impedance. No idea if he was right, but he seemed to be. However he did say the rated impedance was only for a specific frequency, which was often at 100Hz.
 

M80

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Looks like you were watching the Olympics, I gave up around 2. The Ladies curling was just too late (early).

I didn't need to go up to the loft as I've a pair of 4 ohm speakers here that I bought to upgrade the Viano, they don't so back they go.
Anyway after knocking off the 0.2 ohm for the leads (I would exepct the Fluke to have to have a REL function for that) these speakers do measure at 3.6 ohm, so I've learnt something here thanks.

With woofers connected the tweeters are pretty hard to monitor, but I would have expected an intermittent faulty connection to produce clicking at minimum. I don't see how an over driving that you describe can be from anywhere else but the amp. But that doesn't explain your slap remedy.

Besides eliminating possible poor connections I'm not sure what else you can do here.
 
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Submariner1

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Looks like you were watching the Olympics, I gave up around 2. The Ladies curling was just too late (early).

I didn't need to go up to the loft as I've a pair of 4 ohm speakers here that I bought to upgrade the Viano, they don't so back they go.
Anyway after knocking off the 0.2 ohm for the leads (I would exepct the Fluke to have to have a REL function for that) these speakers do measure at 3.6 ohm, so I've learnt something here thanks.

With woofers connected the tweeters are pretty hard to monitor, but I would have expected an intermittent faulty connection to produce clicking at minimum. I don't see how an over driving that you describe can be from anywhere else but the amp. But that doesn't explain your slap remedy.

Besides eliminating possible poor connections I'm not sure what else you can do here.

Yep your woofers at 3.6 Ohms are close to that guys estimate of them reading less 15%.
I do get this loud almost “scratchy distortion” over the top of partial-music on the tweeter.

My thoughts are
1. Its either an intermittant Amp problem, and the slap cure was just one almighty coincidence, and an even bigger coincidence, that its run perfectly for 3 days solid (normally it plays up everyday or at least every other one ).
2. Its a tweeter wiring issue or tweeter voice coil on the way out. And the Amp has very poor/no protection on the output stage and that resulted in the other speakers going quiet etc..

My plan is to wait till it fails, and then get it on a STAR system for a full Comand and Amp test.

If its easy to get the tweeter out I might look at that.
And if I get some feedback re removing the boot side panel, I would like to take that out, to check its got no rainwater damage.

And pretty much follow the Star fault code diagnosis.
 

rayhennig

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So Imwould imagine somewhere else is a more exacting crossover, maybe in the Amp output stage??
I very much doubt that. Although I have no experience of more modern car systems, I imagine that serious cross-overs would be an unlikely sophistication.

Is the woofer fitted with any similar (1st order) roll-off?

Your "scratchiness" sounds a bit like a distorted voice coil. Replacement drive, I think.

Good luck.

RayH
 
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Submariner1

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I very much doubt that. Although I have no experience of more modern car systems, I imagine that serious cross-overs would be an unlikely sophistication.

Is the woofer fitted with any similar (1st order) roll-off?

Your "scratchiness" sounds a bit like a distorted voice coil. Replacement drive, I think.

Good luck.

RayH

Do you think its just a cap or a coil job then?

We think alike on tne scratchiness .. hence I haven't replaced the amp yet.
What I dont understand is the shift in power level ( upwards ) to the tweeter?
 


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