Are there Any members who really understand speakers and crossovers technically?

Submariner1

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Q1. Can I “safely” test the wiring integrity and speaker voice-coils on one channel by using a Fluke auto-ranging multimeter, attached to the Amplifier’s disconnected speaker terminal block ? I.e. test in situ.

Reason for testing
Basically to rule out any shorting on the channel’s wiring and or rule out any broken/faulty voice coils, which might account for the intermittent loss of sound on all channels except This one.

My Logic
Whenever the sound distorts, its only on the left door’s Mid-Range and Tweeter speakers. The wiring diagram shows me this tweeter is joined in parallel to the mid range Speaker, the Tweeter has a capacitor to filter and block the low frequencies, I therefore assume the midrange may? (But I can’t see without taking off the door card) have a coil and a capacitor to isolate the mid range.

It seemed sensible, while the Amp is away being tested, and hopefully repaired at BBA, to test from the disconnected speaker terminal block. See below.
963EE7FD-3854-40EB-B32C-66E1E7441B9B.jpeg

Reasons:
- enables me to verify the Amplifier has been repaired properly
- if there was a wiring / speaker problem, it would be stupid to re-connect a repaired amplifier ... only for potentially faulty wiring or a faulty voicecoil to blow the amplifier’s output stages again.

... the circle could go on forever.

- the shortest route to a full cure.
- it may prevent faulty wiring damaging any speakers that have survived todate.

The shortcomings of my logic
Ideally one should have an Audio AC Impedance Meter to test the impedance of a speaker. But a DC Resistance meter will give me a close enough reading, at least to know they arent going OL or are wildly off, or shorting to ground or each other.

Likewise, I think technically I should:
1. Disconnect both speakers and test the wiring on its own Amp to Mid range.
- and then Disconnect the connector ( mid-range speaker to tweeter ) and check the Tweeter’s extended wiring.
2. Then, Test each speaker individually excluding coils and caps , and later test each coil and cap.

The difficulty is I dont want to take the door card off , and that is essential to get to the midrange speaker and the Tweeter connector.

I dont know if one tests the whole Channel by touching the Amplifier speaker wiring terminals inside the connector block, if one could damage the Capacitors in HK’s basic crossovers. Any views on this?

My other idea was to also test the resistance of the Right Midrange- Tweeter channel.
I.e. if they are the same, then I can assume all is well with the left door’s wiring and speakers.

The question is, is it safe for the speakers voicecoils and associated coils and especially the capacitors to simply test by connecting the Multimeter to the + and - at the Amplifier connector block?
Could I damage anything within the left midrange speaker channel?
 

Ken_R

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Do you not have an old Radio/Tape/CD player with an Ext Speaker socket? Or even a laptop?

Strip back t'other end of cable, plug into output device, and use the exposed wires as 'probes'.
 

BillyBoy

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Can't see any issue with the test. Dont know the impedance of the MB speakers, but most likely between 2 and 8 ohms. The meter will be pushing milliamps down the wire to measure this, even at 100 mA, the voltage over the terminals will be leas than a volt. The capacitors that filter out the low frequency to the tweeters will almost certainly take 50v plus, so you won't do any damage to them I don't think.
 

Botus

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you have a broken amp and a broken speaker,

why do you need to use time checking stuff that isn't wrong, when you know you need to replace two components?
of course your life, your time and if it floats your boat enjoy, but why bring the whole forum in to your special world when there are plenty of merc owners who cars don't want to drive we could be helping?
 
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Submariner1

Submariner1

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Do you not have an old Radio/Tape/CD player with an Ext Speaker socket? Or even a laptop?

Strip back t'other end of cable, plug into output device, and use the exposed wires as 'probes'.

Sadly I dont have one.
But a nice idea. Not ideal, as a reading would be better to compare with the other side due to the intermittant nature of the fault.
 
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Submariner1

Submariner1

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Can't see any issue with the test. Dont know the impedance of the MB speakers, but most likely between 2 and 8 ohms. The meter will be pushing milliamps down the wire to measure this, even at 100 mA, the voltage over the terminals will be leas than a volt. The capacitors that filter out the low frequency to the tweeters will almost certainly take 50v plus, so you won't do any damage to them I don't think.

Thanks
I didnt think it would, just would rather check.

One last question does it matter polarity wise, not a biggy as I think I have worked out the polarity of the wires correctly.
 
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Submariner1

Submariner1

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you have a broken amp and a broken speaker,

why do you need to use time checking stuff that isn't wrong, when you know you need to replace two components?
of course your life, your time and if it floats your boat enjoy, but why bring the whole forum in to your special world when there are plenty of merc owners who cars don't want to drive we could be helping?

Actually I dont know which part or parts are broken.

Remember the full STAR test could find NO FAULTS .. despite the system hissing like a pig.

I also dont have all the classic Amp problems, but have sent it off to be checked and mended Anyway and the intermittent nature was driving me crazy.

I initially thought it was the Tweeter , but on careful listening I noted it was also the midrange speaker distorting. I then found the tweeter spurs off the midrange speaker wire ... a blow as that ment any distorted signal would hit both speakers.

So I think its quite logical to try and determine, is it the amp or the speaker wiring or the tweeter or both the tweeter and the midrange.? No ?

Originally as the Tweeter was only £30 I would replace that anyway; as distortion kills tweeters pretty quickly.
But the discovery that the Tweeter spurs off the midrange, and that was also distorting a bit, is a big blow as that is £226 plus vat! ( its one unit with the woofer :()

So tell me where I am wasting time, eh!
Personally I would rather not shell out £300 on top of an amp fault repair, for crappy HK speakers!

As for “checking stuff that isnt wrong” .. where the f*ck did you get that from.
Chill out and read the post carefully.
Or are you so brilliant you can determine which components are faulty?

For all I know any of the following is the culprit.
Amplifier, wiring to mid range, wiring to tweeter, mid range voice coil, tweeter voice-coil.
Or a few of them.
As I said Star could find No Faults.
Neither could my MBII find a fault or register with this amp.

Sorry if my audio electronics is not brilliant but I thought it was sensible to check whether one could test a tweeter with a multimeter as it save taking off a Door liner, which would be a bastard in 3” of snow.
 

BillyBoy

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Thanks
I didnt think it would, just would rather check.

One last question does it matter polarity wise, not a biggy as I think I have worked out the polarity of the wires correctly.
As the audio signal is AC, the filter capacitors are not polar, so no issue which way you connect the meter. The polarity only matters to the audio signal ( so all speakers in the system go "out" together. If you got the polarity wrong on one speaker, that would be on the "in" stroke while the other would be on the "out" stroke leading to out of sync sound waves and poor sound quality.)
 
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Submariner1

Submariner1

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As the audio signal is AC, the filter capacitors are not polar, so no issue which way you connect the meter. The polarity only matters to the audio signal ( so all speakers in the system go "out" together. If you got the polarity wrong on one speaker, that would be on the "in" stroke while the other would be on the "out" stroke leading to out of sync sound waves and poor sound quality.)

Thanks so much, I had forgotten that its AC! :):)
Looks like you solved my questions perfectly. And I can now test with confidence. And try and rule out any of the “possibles”.

It would be so much easier if one was working indoors.
Then I could take off the door liner and check the components easily.

Although its a hideously expensive Amp, the components look pretty cheap as chips, so I have little faith they put in any good stuff like output stage failure shut down.
So imo its essential to verify the speaker side is ok before re-installing the repaired amp.
 
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