Panic

[neilmaui]

so my wife just texted me from home ....honey don't get mad, I was just listening to some music ( not overly loud) then I could smell a kind of electrical burning from one of your new speakers.... I look at the message again and think...maybe this is a joke..but no. I just completed some new Mini Statements ( about 2 months old) , assembled with pre made cross overs from Meniscus and driving them with an Emotiva XPA 2. I get home in 5 minutes ( usually takes me 20) and have a short time to check them before having to be back at work. Cannot smell any burning smell from the ports/ drivers. I turned them on and they sound OK, all drivers OK...couldn't conduct any precise listening checks. Will check them over tonight when I can...anything I should look for? Im sure my wife would greatly appreciate any advice!!!!

[jim1961]

I had a pair of speakers once where an incorrectly wired impedance circuit caught fire inside the speaker and cooked a resistor. After it had cooked itself and stopped burning, later I really couldn't smell anything either. But a look inside showed black score marks on the inside of the cabinet where the resistor lay black beside it.

I would say the only way to be sure and put your mind to rest is to take a look inside. Not saying what happened to me happened to you. But a visual check is probably the only solid proof that confirms everything is OK.

[JonMarsh]

The only other thing that occurs to me is to check for DC offset on the amp- this can be a problem for speakers, but usually manifests much more disastrously!

[neilmaui]

thanks guys, Jon, what is DC offset and how can I check this?

[neilmaui]

also seems strange that they have worked fine for 2 months and now decide to ignite!!

[jim1961]

also seems strange that they have worked fine for 2 months and now decide to ignite!!

This part doesn't make sense, agreed. Possible what she smelled wasn't coming from the speaker?

[neilmaui]

I really hope so!! or she may be sleeping on the sofa!....I'll take the drivers out and take a look at the cross overs when I get home this evening. Not the easiest as the cross overs are in a lower section of the cabs, but I stuck them on with super strong Velcro so may be able to at least see if I can see any burning...

[Mr.Ed]

This happened with another pair, if I remember correctly after playing them at high volumes one of the resistors overheated and burnt. I don't remember if it burned some of the insulation or not.
-Ed

[Jim Holtz]

This happened with another pair, if I remember correctly after playing them at high volumes one of the resistors overheated and burnt. I don't remember if it burned some of the insulation or not.
-Ed

That incident was the result of trying to play them at a volume sufficient to hear them while out in the yard. The amp was a big pro amp. We suggested paralleling mid-range resistors for better power handling for excessive volumes.

Jim

[neilmaui]

Thanks for all the input guys here is the damage I found when I checked the crossovers last night. This is the mid x-over...

[IMG][/IMG]

[IMG][/IMG]

[IMG][/IMG]

any idea's was this a component fail and how can I ensure this doesn't happen again?

[Mr.Ed]

Keep the resistor away from the cap and raise it off the board for air flow.
-Ed

[neilmaui]

thanks Ed, this was a pre assembled board from Meniscus, will send them some pics and see what they suggest.

[neilmaui]

Meniscus have been great, Mark said he could send me another resistor with a higher power rating but this will send more power to the mid, is this advisable?

[jim1961]

Meniscus have been great, Mark said he could send me another resistor with a higher power rating but this will send more power to the mid, is this advisable?

It wont send more power. It may allow more (maybe thats what you meant). In any case, you dont want a undersized (wattage rating) resistor being the element that limits midrange power.

Is he sending a matching one for the other channel as well? How much power (amp power) are you running? What are the midranges power rating? Are you sure the crossover is crossing over the mids at a high enough frequency and at a steep enough slope?

[Johnloudb]

thanks guys, Jon, what is DC offset and how can I check this?

Well, I'm not Jon but John and have had two speakers destroyed by DC at the output of two different amps. You can measure DC offset at the output of the amplifier with a volt meter. With the amp turned on put the test leads of the volt meter or multi-meter on the amp output. The DC should be in less than 0.1 volt. I've measured about 45mV at the output of properly working amps.

Sounds like you've found the problem but best to check out the amps to be sure, that it's not just an under rated resistor.

John

[neilmaui]

Just noticed if you zoom in on the cap in my picture it's value is 9.1uF, then checked the wiring diagram for the mini statements mid and that cap should 5.6uF so think i have the wrong value cap in there....what will this do to the mid sound? I got the x overs per wired in kit form.

[jim1961]

Just noticed if you zoom in on the cap in my picture it's value is 9.1uF, then checked the wiring diagram for the mini statements mid and that cap should 5.6uF so think i have the wrong value cap in there....what will this do to the mid sound? I got the x overs per wired in kit form.

The values have to be right. A difference like your describing will cause the driver associated with it to x-over at the wrong point in the wrong way, thus the speaker itself wont sound like it should. Given you already have discovered (the hard way) a resistor with the wrong power value and now a cap with the wrong capacitance, I would be highly suspect of the entire x-over.

[neilmaui]

Thanks Jim, I thought the speakers sounded good with the wrong crossover, once I get the right one in there hopefully ill notice a difference. Just wondered if it will just be noticeable in the mids or whether the whole sound will change.

[jim1961]

Thanks Jim, I thought the speakers sounded good with the wrong crossover, once I get the right one in there hopefully ill notice a difference. Just wondered if it will just be noticeable in the mids or whether the whole sound will change.

One would have to look at what that cap was doing in the crossover design (look at the entire crossover design) to make guesses on what will change.