Tweeter problems

[seashell]

I've had a Marantz PM6002 amp for a while. It has been paired in it's time with Mordaunt Short 902i standmounts and Tannoy F4 floorstanders. Both sounded great through the amp. In both sets of speakers however the tweeters have gone. Music is never turned up ridiculously loud as I live on a terraced street so never going to go crazy!

I don't really like getting bogged down in ohms, etc as realistically very variable but seemed like only way to look at it! On paper, there shouldn't have been any problems.

The Marantz is running 2x 45w into 8ohms, 4ohm to 16ohm speaker load impedence.

The 902i's stated as 8ohm on this site, others suggest a range of 4-8ohm impedence. Recommended amp range from 15-100 watts.

The F4's are stated to be around 8ohm, with max power output of 200w and with recommended amp power from 10 - 140w.

I know this isn't a definitive way to look at things as these numbers can be extremely variable. Anyone any ideas on problems that may be going wrong or other things to look at to think of issues? Don't really want to spend money on new speakers for same thing to happen again. A pair of replacement tweeters for the Tannoys are going to be £200 so just not worth it.

Thanks.

 

[andyjm]

This is unusual. When amp's output drivers pack up, they often put DC across the speaker terminals. The speaker crossover blocks DC to the tweeters, so they survive, but the bass driver voicecoil gets fried. For anything nasty to get to the tweeters, it has to get through the crossover first. This is most often the case when the amp is driven into clipping, and the resulting clipped waveform has a large HF component which goes through the crossover and fries the tweeter.

Clipping sounds dreadful, and usually only happens when the amp is being overdriven. Even if the amp had something weird going on that causes it to clip early (supply rails under voltage for example), you would notice the sound was very poor.

There is one possibilty, though unlikely. Amps can self oscillate, quite possibly as supersonic frequencies. Good designs have circuitry to stop this, but maybe yours has a fault or was a poor design in the first place. In this case, the amp will be pumping out high frequency sound you can't hear that is still heating up the tweeter voicecoils.

Any decent repair shop should be able to test the amp very quickly with a 'scope.

 

[shafesk]

Hi, any chance you were running both speakers simultaneously? If you were doing so then that might explain it since the marantz can only power 2 speakers at a time.

OR

If you were running them together as zone a and b speakers, you might have accidentally powered all 4 at the same time.

OR

Tweeters usually go bad if you biwire incorrectly, if you biwire without removing the biwire links first.

If you don't want to spend that much on repairing the speakers get new speakers and sell these off. You might also try a third party repair shop.

 

[davedotco]

Hi, any chance you were running both speakers simultaneously? If you were doing so then that might explain it since the marantz can only power 2 speakers at a time.

OR

If you were running them together as zone a and b speakers, you might have accidentally powered all 4 at the same time.

OR

Tweeters usually go bad if you biwire incorrectly, if you biwire without removing the biwire links first.

If you don't want to spend that much on repairing the speakers get new speakers and sell these off. You might also try a third party repair shop.

What.....?

The number of speakers is irrelevant. The Pm6002 can drive two pairs with ease providing the combined impedence does not drop below 4 ohms.

For both sets of tweeters to blow the amplifier must have been operating in 'fault' conditions.

This may have been temporary, overdriven most likely with the impedence dropping significantly below 4 ohms or the amp may be faulty. Have it checked.

 

[seashell]

It's a while back but I think I did probably run both together at some point, although they didn't blow during this time, changed it back due to space issues! Sorry if this may sound stupid, but the amp would only be able to run one set of speakers at any one time?

 

[shafesk]

well its a stereo amp and in a stereo setup the amp runs only 2 speakers at the same time, driving two pairs of speakers (at the same time) through a stereo amp reduces the impedance and depending on the speakers and the volume level might have caused it. Anyway would recommend that you run only one pair of speakers at one time. If it is a requirement of yours to run 4 speakers at once, a 4 channel amp is a much better choice.

 

[Anderson]

Does anyone else have access to your HiFi when you're not around?

 

[shafesk]

Hi, any chance you were running both speakers simultaneously? If you were doing so then that might explain it since the marantz can only power 2 speakers at a time.

OR

If you were running them together as zone a and b speakers, you might have accidentally powered all 4 at the same time.

OR

Tweeters usually go bad if you biwire incorrectly, if you biwire without removing the biwire links first.

If you don't want to spend that much on repairing the speakers get new speakers and sell these off. You might also try a third party repair shop.

What.....?

The number of speakers is irrelevant. The Pm6002 can drive two pairs with ease providing the combined impedence does not drop below 4 ohms.

For both sets of tweeters to blow the amplifier must have been operating in 'fault' conditions.

This may have been temporary, overdriven most likely with the impedence dropping significantly below 4 ohms or the amp may be faulty. Have it checked.

Sorry, you are wrong if you think the number of speakers is irrelevant and the pm6002 can drive 2 pairs with ease is also an exaggeration. The pm6002 is no beast of an amp. You can easily ruin a driver trying to power more than 2 speakers from a stereo amp because it is not something they are designed to do, unless you play it very softly. But why risk it in the first place?

 

[davedotco]

Hi, any chance you were running both speakers simultaneously? If you were doing so then that might explain it since the marantz can only power 2 speakers at a time.

OR

If you were running them together as zone a and b speakers, you might have accidentally powered all 4 at the same time.

OR

Tweeters usually go bad if you biwire incorrectly, if you biwire without removing the biwire links first.

If you don't want to spend that much on repairing the speakers get new speakers and sell these off. You might also try a third party repair shop.

What.....?

The number of speakers is irrelevant. The Pm6002 can drive two pairs with ease providing the combined impedence does not drop below 4 ohms.

For both sets of tweeters to blow the amplifier must have been operating in 'fault' conditions.

This may have been temporary, overdriven most likely with the impedence dropping significantly below 4 ohms or the amp may be faulty. Have it checked.

Sorry, you are wrong if you think the number of speakers is irrelevant and the pm6002 can drive 2 pairs with ease is also an exaggeration. The pm6002 is no beast of an amp. You can easily ruin a driver trying to power more than 2 speakers from a stereo amp because it is not something they are designed to do, unless you play it very softly. But why risk it in the first place?

Are you suggesting that a PM6002 can count?

If it sees a 4 ohm load it matters not how many speakers make up that load, the amplifier neither knows nor cares. In fact driving two pairs of 8 ohm speakers is probably safer than driving a single pair of 4 ohm speakers, at least the speakers will handle more power should that ever be an issue.

 

[shafesk]

the number of speakers count because 2 pairs of 8ohm speakers will reduce impedance to 4 ohm, 3 pairs will reduce it further so its obvious the number of speakers matter for a given impedance. 2 pair of 8 ohm speakers can dip well below 4 ohms as these are nominal figures. I know many 8 ohm speakers which go down to 2 ohms and many 4 ohm speakers that dip to only 3 ohms. It depends on how low the impedance falls for a given speaker and not the nominal impedance.

 

[iQ Speakers]

Davedotco only last night I thought I hadn't seen you around for a while. I was worried about you!

 

[davedotco]

Lots of people worry about me. Mostly that I will fall off my soapbox and break something.

Mind you, as a fully fledged speaker manufacturer I'm surprised you have the time to hang out with us amateurs.

Mind you I am thinking of taking a course on quantum mechanics, easier than trying to explain basic science to a lot of people on here.

 

[davedotco]

the number of speakers count because 2 pairs of 8ohm speakers will reduce impedance to 4 ohm, 3 pairs will reduce it further so its obvious the number of speakers matter for a given impedance. 2 pair of 8 ohm speakers can dip well below 4 ohms as these are nominal figures. I know many 8 ohm speakers which go down to 2 ohms and many 4 ohm speakers that dip to only 3 ohms. It depends on how low the impedance falls for a given speaker and not the nominal impedance.

So please explain this to me.

What is the difference between an amplifier driving one 4 ohm speaker and two 8 ohm speakers wired in parallel?

 

[TrevC]

Tweeters usually go bad if you biwire incorrectly, if you biwire without removing the biwire links first.

Nope. Twaddle.

 

[kitkat]

This is rare but sometimes the crossover inside the speaker can reverse, its called reverso flash over, if this has happened the woofer becames the tweeter and the tweeter becames the woofer, because the tweeter cannot handle the powerful low bass sounds it blows but as the woofer can handle the tweeter sounds that remains OK, no one still knows why this happens.

 

[TrevC]

This is rare but sometimes the crossover inside the speaker can reverse, its called reverso flash over, if this has happened the woofer becames the tweeter and the tweeter becames the woofer, because the tweeter cannot handle the powerful low bass sounds it blows but as the woofer can handle the tweeter sounds that remains OK, no one still knows why this happens.

Sometimes a fairy connects lightning to the wires which causes the speaker to take off and disappear into never never land. Nobody knows why I think this can happen.