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Discussion Starter · #1 ·
Hi guys. I have two Mordaunt-Short MS 5.20s wired up to a JVC AX-A372 amp (very old, I know). The woofers(?) on the speakers (the bottom ones) work well and have a nice solid bass etc, but the tweeters(?) at the top of the speakers don't appear to be making any noise at all. I use the setup for making music and I struggle to hear a piano over some bass (for instance) but I've read that they're pretty good speakers, so I'm guessing that there must be something wrong with the speakers in some way - there's no way the top end is supposed to sound that muddy (and I'm no audiophile). I've got the treble turned all the way up on the amp and it's just about okay, but still definitely not what they're supposed to sound like.

I'm no expert on this, so I have no idea what's going on!

Here is what the wiring at the speaker and the amp is like (set up by a friend, not me). The positive wire at the speaker is passing through both "holes" (same for negative). I've tried wiring it so that it only went into the top one (marked as treble, the bottom two say bass) but then the speakers don't work at all.

The amp is fine, I get a very clear sound through headphones. What is going on here?

Thanks,
Dan
 

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Here is what the wiring at the speaker and the amp is like (set up by a friend, not me). The positive wire at the speaker is passing through both "holes" (same for negative). I've tried wiring it so that it only went into the top one (marked as treble, the bottom two say bass) but then the speakers don't work at all.

The amp is fine, I get a very clear sound through headphones. What is going on here?

Thanks,
Dan
Your wiring looks fine. What is the history of the speakers? It sounds like there may be an internal wiring problem or issue with the crossover, but it would be odd for the exact thing to happen on two speakers at once.
 

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Same thing happened to me. I noticed both tweeters not playing. Probably they went out at different times but I (and you) didn't notice. The crossovers (simple capacitors) in my case were blown. Took them out, went to an electronics supply store and they sold me two replacement capacitors for $1.29. Twisted them in and everything was fine. Capacitors don't last forever. Don't know if yours are blown or if it will be so easy to fix. Good luck.
 

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The odds are the tweeters are blown. They are easy to replace. Go to a dealer who carries the brand and they'll order a pair for you. A blown crossover component is very unlikely. By the way, the following are typical reasons why a tweeter might be blown: 1) you played them too loud. 2) you turned up the treble control and played too loud. 3) you used too small an amplifier, power-wise, and played too loud. A small over-driven amplifier will add high frequency distortion at high levels if you play it too loud. 4) you use a very powerful amplifier and played to loud.

When you take out the old tweeters, observe the polarity of the hook up cables. Hook up the replacements the same way.

Finally, know that tweeters make relatively soft sounds--amost a whisper at times (depending on the loudspeaker) so if you do hear sounds, they may be okay but from your diagnostics, it seems you have indeed blown the tweeters. That JVC may not have the headroom to handle piano.
 

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The odds are the tweeters are blown. They are easy to replace. Go to a dealer who carries the brand and they'll order a pair for you. A blown crossover component is very unlikely.
As another poster stated, capacitors failing is a common cause of this type of symptom (far more common, I think, than actual damage to a driver -- ripped cones aside, most "blown" speakers are actually crossover or other passive component problems rather than, say, a melted coil).

It also appears that this brand of speaker has some sort of "soft" protection circuit, which I would bet is what has failed here.

Again, I wonder what happened before this was noted. When were these previously known to work properly, and what changed in between? If these were a garage-sale or similar find, I'd guess that anything from bad caps to totally removed tweeters might be at fault.
 

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I've had speakers with internal fuses, a low current quick-blow one on the tweeters, and a slow blow one on the woofers.

A spike, perhaps from connecting something to the audio inputs without turning the amp down or off, could have blown the fuse.

Otherwise it could be blown tweeters. Ensure you get a matched pair.
 

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Oh, and I have also seen speakers with fake tweeters, where they are just a dome with no actual driver. However, it seems you would have noticed this!!
 

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Discussion Starter · #8 ·
Your wiring looks fine. What is the history of the speakers? It sounds like there may be an internal wiring problem or issue with the crossover, but it would be odd for the exact thing to happen on two speakers at once.[/QUOTE]

I have no idea, the speakers in question are actually at my school in a crappy studio-type thing and it was all rigged up a long long time before I ever set my hands on it. I've been using the speakers for more than 18 months though and they've never sounded different between uses. I guess someone must have screwed them up a long time ago
 

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Discussion Starter · #9 ·
Same thing happened to me. I noticed both tweeters not playing. Probably they went out at different times but I (and you) didn't notice. The crossovers (simple capacitors) in my case were blown. Took them out, went to an electronics supply store and they sold me two replacement capacitors for $1.29. Twisted them in and everything was fine. Capacitors don't last forever. Don't know if yours are blown or if it will be so easy to fix. Good luck.
How do you go about replacing the capacitors? I've never taken a speaker (or anything electronic, for that matter) apart in my life and they're the schools so I'm not entirely sure how much I'm allowed to do to them
 

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Discussion Starter · #10 ·
The odds are the tweeters are blown. They are easy to replace. Go to a dealer who carries the brand and they'll order a pair for you. A blown crossover component is very unlikely.
As another poster stated, capacitors failing is a common cause of this type of symptom (far more common, I think, than actual damage to a driver -- ripped cones aside, most "blown" speakers are actually crossover or other passive component problems rather than, say, a melted coil).

It also appears that this brand of speaker has some sort of "soft" protection circuit, which I would bet is what has failed here.

Again, I wonder what happened before this was noted. When were these previously known to work properly, and what changed in between? If these were a garage-sale or similar find, I'd guess that anything from bad caps to totally removed tweeters might be at fault.
These speakers actually belong to my school, I use them in our crumby little studio bit quite a lot. They've always sounded like they do now since I've been using them (18 months+) but there are also a lot of idiots at school so I wouldn't be at all surprised if someone had blown them
 

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Discussion Starter · #11 ·
The odds are the tweeters are blown. They are easy to replace. Go to a dealer who carries the brand and they'll order a pair for you. A blown crossover component is very unlikely. By the way, the following are typical reasons why a tweeter might be blown: 1) you played them too loud. 2) you turned up the treble control and played too loud. 3) you used too small an amplifier, power-wise, and played too loud. A small over-driven amplifier will add high frequency distortion at high levels if you play it too loud. 4) you use a very powerful amplifier and played to loud.

When you take out the old tweeters, observe the polarity of the hook up cables. Hook up the replacements the same way.

Finally, know that tweeters make relatively soft sounds--amost a whisper at times (depending on the loudspeaker) so if you do hear sounds, they may be okay but from your diagnostics, it seems you have indeed blown the tweeters. That JVC may not have the headroom to handle piano.
Could you elaborate on what you meant about the amp? I have no idea about these things but the school (who own the speakers) were looking at getting a load of new kit soon - I'm sort of in charge of looking for what they should get (within reason) because I use it the most.

If it's something that should really be replaced, why and what should I/they look for in a new one? We've also got a Focusrite preamp which we don't use at the moment (we haven't got any Macs etc. to plug it into) as well if that makes any difference
 

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Replacing tweeters isn't very hard, unless they're not removable (but usually they are). I'd lean more towards the tweeter having been blown than the crossover (at least the last several I blew left the crossover intact). Only one way to find out, start taking the speakers apart and test the components. Anyone familiar with electronics at your school? They may have the necessary skills to help you out....
 

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Over the last 50 years, I have consulted for or represented the following manufacturers (there are more but I tire of these threads): Bose, a/d/s/, AR, Apogee, Advent, platinum, Sonus FAber, JM Lab (Focal), M&K, Totem, Canton, Sunfire and now, the new Bob Carver company. I've rarely seen blown crossovers I've seen hundreds of blown tweeters. Before we tell this poor fellow to start tearing into his crossover networks, let him simply remove the tweeters and bring them to a dealer for testing. It is so much easier And far more likely to be the problem then a failed capacitor.
If he's stuck, he can call me at 847-668-4519 and I will walk him through it for free as I have done for dozens of Sunfire owners with failed subwoofers on this forum. For better or worse, we are all in this together.
Frank Malitz
 

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Remove the tweeter(s) and connect a 1.5 volt AA(A) battery with some wire to the tweeters terminal and make and break just one of the contacts.
If you hear a clicking noise when the wire touches the tweeter(s) is/are ok.


You can also do this when the tweeter is in de speaker cabinet by touching the speaker terminals.


If the separated tweeter clicks but doesn't does click when in the cabinet the fault is in the crossover. This can be the capacitor or there may be a blown fuse in the crossover circuit.
 

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Remove the tweeter(s) and connect a 1.5 volt AA(A) battery with some wire to the tweeters terminal and make and break just one of the contacts.
If you hear a clicking noise when the wire touches the tweeter(s) is/are ok.


You can also do this when the tweeter is in de speaker cabinet by touching the speaker terminals.


If the separated tweeter clicks but doesn't does click when in the cabinet the fault is in the crossover. This can be the capacitor or there may be a blown fuse in the crossover circuit.
I like that, and appreciate the info! I have a couple of tweeters from my old Hafler 200's to check. One sounded bad after 20+ years of use (and kid abuse) so I had swapped tweeters in both speakers for Vifa equivalents. Now I can assure myself that one really is faulty and convince myself to part with the 1989 vintage piece.
 
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