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Just caught my speaker on fire!

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  • Wolf
    replied
    Re: Just caught my speaker on fire!

    Originally posted by davepellegrene View Post
    I should also mention when I pulled the first one out the night it happened the large cap was warm as well. I assume that should be expected.

    Thanks Dave
    I've never seemed to heat up any caps in my stuff. Could be just that it was an adjacent heat source?

    Later,
    Wolf

    Leave a comment:


  • davepellegrene
    replied
    Re: Just caught my speaker on fire!

    Originally posted by curt_c View Post
    Dave, You definitely need to open the other Mini and address this issue there as well. I don't think the tweeter resistors will need to be replaced, but let me know if they look like they show any signs of overheating.

    Keep in mind that the power ratings on the Arcol and Vishay resistors assume they are mounted on a properly sized heat sink, but it sounds like if we double up with the sandcast resistors, raise them up off the board, and get them out into free air, that Freddie won't be able to cause any more damage.

    C
    I got the other one opened up yesterday. Here is a pic of the mid xo. It appears it was on its way as well. The hot glue melted off the resistor and there is a burn mark on it. Probably from the foam that was covering them.



    I think I may just replace them with the same resistors paralleled as you suggest. I already have the resistors. Along with the proper installation techniques they should be fine. All the other ox boards look fine. I should also mention when I pulled the first one out the night it happened the large cap was warm as well. I assume that should be expected.

    Thanks Dave

    Leave a comment:


  • Deward Hastings
    replied
    Re: Just caught my speaker on fire!

    If you can smoke a shunt resistor you can smoke a voice coil.

    It's another benefit of active crossover . . . you can size the individual amps to their respective drivers, and avoid all the excitement . . .

    Leave a comment:


  • jonpike
    replied
    Re: Just caught my speaker on fire!

    Wow... glad it didn't do more damage, like melt/short a cap and cause a blown driver or something worse.

    Fire of course would also be bad. I would think that inside the box, you likely would have a limited enough supply of oxygen that a small fire might limit itself and choke out... but burning thru a cone and letting fresh air in could be another story...

    Strange that I was just thinking about this a few days back, not the fire part, but how much power various crossover parts might end up dissipating. Started mocking up a few XO's in a SPICE program to see what kinds of peak currents were flowing. Now, I want to model up a Mini Statement XO and see what that resistor will see with various power levels in. I'll report back when I do...

    Leave a comment:


  • curt_c
    replied
    Re: Just caught my speaker on fire!

    Dave, You definitely need to open the other Mini and address this issue there as well. I don't think the tweeter resistors will need to be replaced, but let me know if they look like they show any signs of overheating.

    Keep in mind that the power ratings on the Arcol and Vishay resistors assume they are mounted on a properly sized heat sink, but it sounds like if we double up with the sandcast resistors, raise them up off the board, and get them out into free air, that Freddie won't be able to cause any more damage.

    C

    Leave a comment:


  • replied
    Re: Just caught my speaker on fire!

    Taking the 4th of July to the next level, Dave?
    Oh well you've got some cleanup and repairing to do. Great lesson for all of us too. Thanks for the pics.

    Leave a comment:


  • Face
    replied
    Re: Just caught my speaker on fire!

    This is exactly why hot glue doesn't belong on resistors. I'm glad the damage wasn't worse.

    Leave a comment:


  • envisionelec
    replied
    Re: Just caught my speaker on fire!

    Active crossovers.



    Whaaaaat....? :D

    Leave a comment:


  • whatatrip
    replied
    Re: Just caught my speaker on fire!

    I try to avoid resistors if I can but I'm currently working on a 3-way that uses the DC200 woofer, ND28F tweeter and DC130BS-8 midrange. The mid needs an L-pad. I started with a 5 ohm 20 watt series and an 8 ohm 10 watt parallel resistor. They got quite hot to the touch so I used an infrared thermometer and got a reading of 180 F. I increase the series to 40 watts and parallel to 20 watts and the series was still pretty warm so I am now at 5 ohm 50 watt (2-25 watt in parallel) series and one 8 ohm 20 watt in parallel. Readings now get up to 120 F at 70% of full power on a 120 watt/channel amp. SPL readings at 2 meters was over 100 dB so I figure I should be ok.

    I've actually blistered my fingers on another system in the past while grabbing a resistor during the high power test of the xover and speaker system.

    My speakers are torn apart now for painting but with this warning, I plan to do some more testing. The crossovers are glued down. Now I wonder if the glue will melt. I put the resistors on top of some 1/8" brazing rods so that the rods look like railroad ties and the resistors look like railroad rails. One rod on each end of the resistors. That should give some some distance between the resistor and the hardboard and some ventilation.

    I keep trying to figure out some kind of external "box" to house the xovers in. Whenever a resistor is involved, external mounting should provide some safety. I've never found any other components getting hot. I even tried a 50 watt variable L-pad and it got quite hot.

    I did the testing with the amp in mono mode so both channels were being routed to one speaker. After I felt safe with the 50 watt series resistor, I ran the speakers in stereo and they didn't get as warm. The amp has a power meter for each channel and it seemed to hover around 25 watts with peaks of 120+ watts.

    Leave a comment:


  • maynardg
    replied
    Re: Just caught my speaker on fire!

    I'm becoming a fan of outboard XOs!!!

    Better ventilation.
    Been doing that awhile. Safer and easier to tweak.

    Leave a comment:


  • christianb
    replied
    Re: Just caught my speaker on fire!

    I'm sorry it had to happen to you but usually some good can come out of a bad experience. I will definitely test my passive crossovers outside the box for a long period of time to see how hot the resistors get and will double any that I feel are too warm for my liking.

    I'm just glad you guys are safe, especially the speakers. :p

    Leave a comment:


  • davepellegrene
    replied
    Re: Just caught my speaker on fire!

    Originally posted by billcurrier View Post
    Your cabinets look very nice from the little I could see of them.
    Here is the build pics on them if you are interested.
    Dave

    Leave a comment:


  • davepellegrene
    replied
    Re: Just caught my speaker on fire!

    The good side of it I have been to a Queen concert many years ago and I can say I was there again last night. That was the closest I have ever been, with any system I have ever had, of recreating a concert feel. The 52" plasma helps in the recreation as well. The down side is I didn't get to watch/ listen to the best part as the concert ramps up through the whole DVD. The few times I have watched it I have never had any amp left at the end. This was the first watch with my QSC GX3 with the Mini's and two subs. I can't wait for the replay. The amp wasn't even warm and I had it set two notches back from full.

    Interestingly I was listening in 2 channel and when I tried surround sound it seemed to bring the volume down. Not sure why that would happen but it did sound better in 2 channel.

    That does make sense about the shunt in the mid needing addressed . There is no restriction on the woofers so it would bottom out first, but wouldn't the tweeter shunt have the same concerns as the mid if it is attenuated as much as the mid?
    Dave

    Leave a comment:


  • billcurrier
    replied
    Re: Just caught my speaker on fire!

    Your cabinets look very nice from the little I could see of them.

    Leave a comment:


  • ravo2000
    replied
    Re: Just caught my speaker on fire!

    Freddy could have set the world on fire with that beautiful voice if only he could have stayed with us a little longer... nice to see he still has that affect from the great beyond. Someone aso mentioned his guitarist... Brian May... another monster among men in the music world. I'm going to listen to some Queen right now.

    This is a great thread... I'm sorry to hear about the speaker, but glad everyone is ok. Just think of the story you have to tell from now on... just don't sell it to J. Peterman like Kramer did with his stories... you'll want to tell this one for years!


    Johnny Ravo

    Leave a comment:

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