Can a faulty amplifier blow a tweeter or a woofer just by being turned on?

[EdW]

You can never completely exonerate the amplifier, but you haven't seen it do anything sufficiently naughty in the DC world to blame it for your speaker issues.

The next obvious question is does it run hot either after it's been on for a while but not playing music; or, if it's been playing music for a while. For example, too hot often means you can't hold your hand on it for more than a few seconds. Very cool means you know it's on, but only just.

Many, if not most quality class D amps run very cool overall (with the possible localised exception of coils in the switched mode power supply). I think we might need to know the make and model of the amplifier so that other ASR correspondents familiar with it could offer their thoughts.

EDIT: correct typo

 

[Veganfloyd]

Many, if not most quality class D amps run very cool overall (with the possible localised exception of coils in the switched mode over supply). I think we might need to know the make and model of the amplifier so that other ASR correspondents familiar with it could offer their thoughts.

Since the amp seems to be an increasingly unlikely culprit after the measurements, I hope that it will be to no detriment (and perhaps benefit, given the safe voltage output) of the company to reveal that this is Loxije A40.

The amp indeed runs cool. Barely any changes to the temperature felt by hand when running with no music playing, and a reasonable level of slight warmth when playing music.

 

[somebodyelse]

You can always try the amp with some cheap sacrificial speakers for a while before using it with any you care about.

 

[Veganfloyd]

You can always try the amp with some cheap sacrificial speakers for a while before using it with any you care about.

Thanks, that was my thinking too, I already ordered the sacrificial lamb earlier today.

I am increasingly skeptical that the amp could have anything to do with the blown tweeter and woofer, but in the extremely unlikely scenario that it did, that would have been specific to the Menuets whilst sparring the Rubicons despite substantially longer playing times and infinitely more on-off cycles completed.

So, I searched for the cheapest used speaker that I could find with matching impedance (not much choice at 4 ohms) and roughly matched sensitivity and size to the Menuets, and I ended up with Acoustic Energy AE100s for £100 as body doubles. Not exactly cheap-cheap, and I am not sure how much sense my matching criteria make, but either way I will report how they are doing in due course.

 

[restorer-john]

DC will not blow tweeters.

Ultrasonic oscillation will blow tweeters and you won't hear a thing.

Get the amplifier checked by a professional before you attach any more speakers to it.

 

[EDMoser]

Did you remove the drivers in question to make sure that an internal wire did not come loose? Since these speakers were pre-owned, they also could have been damaged on arrival.

 

[Veganfloyd]

DC will not blow tweeters.

Ultrasonic oscillation will blow tweeters and you won't hear a thing.

Get the amplifier checked by a professional before you attach any more speakers to it.

Thank you for the suggestion. Before I invest resources into this, I have to ask: is it possible for the oscillation to just happen randomly, kill one tweeter, and go into remission without affecting tweeters across several weeks in two further paris of speakers? Or do you mean that it could have also blown the woofer in the third pair of speakers?

 

[Veganfloyd]

Did you remove the drivers in question to make sure that an internal wire did not come loose? Since these speakers were pre-owned, they also could have been damaged on arrival.

I never opened a speaker in my life. Sounds like the right time to try. I will investigate how to do it. Thank you for the idea.

 

[restorer-john]

Thank you for the suggestion. Before I invest resources into this, I have to ask: is it possible for the oscillation to just happen randomly, kill one tweeter, and go into remission without affecting tweeters across several weeks in two further paris of speakers? Or do you mean that it could have also blown the woofer in the third pair of speakers?

It's unlikely but quite possible. Tweeters are hard to kill with normal music or even loud music. But HF oscillation can destroy a tweeter in a second or less.

You've had a run of bad luck, but there's too many variables to say with certainty what is going on as you've replaced several items in quick succession.

 

[AdamG]

I recently bought a 'chi-fi' class D amplifier

Hi Veganfloyd,

We know that you don’t mean this in a derogatory manner towards Chinese people. We have a Forum specific Policy to avoid this description. Therefore, we kindly request our Members avoid using this terminology “Chi-fi” as it can have negative connotations for such companies and individuals.

Thank you for your cooperation and understanding in this regard.

 

[Veganfloyd]

Hi Veganfloyd,

We know that you don’t mean this in a derogatory manner towards Chinese people. We have a Forum specific Policy to avoid this description. Therefore, we kindly request our Members avoid using this terminology “Chi-fi” as it can have negative connotations for such companies and individuals.

Thank you for your cooperation and understanding in this regard.

Thank you, my apologies, I deleted the term from my first post.

 

[Veganfloyd]

The cables seem attached as they should be. I thought I'd attach a picture in case any information on the cause of the woofer damage can be inferred from it.

@EdW , would you by any chance know a place in or around Cambridge that could do the ultrasonic oscillation check for not too silly money?

 

[Sokel]

The cables seem attached as they should be. I thought I'd attach a picture in case any information on the cause of the woofer damage can be inferred from it.

@EdW , would you by any chance know a place in or around Cambridge that could do the ultrasonic oscillation check for not too silly money?

Judging by the condition of the driver...wow!
That's not a few volts passed in there,it's like they were plugged straight to mains 230V AC voltage.

You should be careful yourself with the gear you have,there's some serious voltage there.

 

[Veganfloyd]

Judging by the condition of the driver...wow!
That's not a few volts passed in there,it's like they were plugged straight to mains 230V AC voltage.

You should be careful yourself with the gear you have,there's some serious voltage there.

Thank you for the warning. Would this kind of damage normally occur with substantial audio/audiovisual effects? There were no 'fireworks' prior to when I noticed the woofer was dead. Also, would one normally feel a smell of the burnt-down elements as the damage occurs? Positive responses would suggest that I received the woofer in this state.

Finally, could this ultrasonic oscillation be responsible for damage that looks like this? Or is a blown woofer a blown woofer and you can't tell how it was blown by the looks of it?

 

[Sokel]

Thank you for the warning. Would this kind of damage normally occur with substantial audio/audiovisual effects? There were no 'fireworks' prior to when I noticed the woofer was dead. Also, would one normally feel a smell of the burnt-down elements as the damage occurs? Positive responses would suggest that I received the woofer in this state.

Finally, could this ultrasonic oscillation be responsible for damage that looks like this? Or is a blown woofer a blown woofer and you can't tell how it was blown by the looks of it?

Audio effects maybe no but definitely smell (it should still be there if you smell it up close) and also heat,this could easily start a fire if it find something flammable close.
Looks like you got them this way if nothing of the above occurred.

Can you take some more pics from different angles?

 

[Veganfloyd]

Audio effects maybe no but definitely smell (it should still be there if you smell it up close) and also heat,this could easily start a fire if it find something flammable close.
Looks like you got them this way if nothing of the above occurred.

Can you take some more pics from different angles?

There was no smell then (2 days ago) and it does not have a burnt-down smell now. The woofer smells pretty much the same at the burn/cable site and the other side of the woofer, and overall it has a similar smell to the inside of the speaker, plus some metallic tones. Hooray!

 

[Sokel]

There was no smell then (2 days ago) and it does not have a burnt-down smell now. The woofer smells pretty much the same at the burn/cable site and the other side of the woofer, and overall it has a similar smell to the inside of the speaker, plus some metallic tones. Hooray!

Here's how the points I have marked should look like:

Yours are completely burned.
That's not an easy thing to do.

Edit:Also what's with the crimps?One is soldered,the other is not.
Something is not right there.

 

[Veganfloyd]

Thank you very much. I missed the initial request for further pictures. I took a few all around the circumference - please see attached. The woofer itself looks normal and the back of the unit looks as though it was brand new.

 

[Bob from Florida]

Here's how the points I have marked should look like:


View attachment 365959

Yours are completely burned.
That's not an easy thing to do.

Edit:Also what's with the crimps?One is soldered,the other is not.
Something is not right there.

I am not so sure the speaker is burned. The lack of any "burned" oder is the red flag. Take a look at a zoomed shot of the OP's original picture. The black stuff on the voice coil coupling leads is an insulating/damping material - I've seen this before - not burned wiring. Another red flag is - the black wires crimp connector has been solder by someone - maybe previous owner. If they did this with the connector plugged into the speaker, that would explain why the voice coil wire is partially or completely unsoldered from its terminal. Look carefully at the zoomed photo and you will notice many strands of that wire have pulled out of the terminal hole. Unplug one of the wires going to the driver and check the resistance of the driver with your multimeter.

 

[Sokel]

I am not so sure the speaker is burned. The lack of any "burned" oder is the red flag. Take a look at a zoomed shot of the OP's original picture. The black stuff on the voice coil coupling leads is an insulating/damping material - I've seen this before - not burned wiring. Another red flag is - the black wires crimp connector has been solder by someone - maybe previous owner. If they did this with the connector plugged into the speaker, that would explain why the voice coil wire is partially or completely unsoldered from its terminal. Look carefully at the zoomed photo and you will notice many strands of that wire have pulled out of the terminal hole. Unplug one of the wires going to the driver and check the resistance of the driver with your multimeter.View attachment 365970

Now that I saw the other pics you're probably right,if it was like I thought it was it would also destroy part of the cone where they attach to it.
It's ironic that I searched before posting to see if there is some insulation and I saw none on the new ones.