Just caught my speaker on fire!

[davepellegrene]

Wow! I was playing my Queen Live in Montreal DVD tonight on my Mini Statements. I was playing at pretty high volume and kept bumping up the volume, but really being careful to stay below distortion levels. About a half hour into the DVD my daughter worked her way front row. I'm kind of smiling getting a kick out of it right behind her. We hear what sounded like the woofer bottom out. Kind of surprised me because it wasn't bass heavy. We look at each other so I turn it down a couple notches. My wife is out on the deck watching through the slider and comes running in and says there is smoke coming out of your speaker. I look at her like yeah right. So I walk up to the speaker to see what she is talking about and sure enough I smell smoke from the ribbon. Everything is still playing. I backed the volume way down and all the drivers sound fine. After about 10 minutes I put my hand on the back of the speaker and its warm. This can't be good. So I pull one of the woofers out. Unbelievable there was no sign of distortion at all. I can't believe I could get something that hot and not even know it.

[kingsnake2]

Re: Just caught my speaker on fire!

Holy crap! thats awesome and sad at the same time

[Wolf]

Yikes!!!

What seemed to give up the ghost?

I've never had one do that...
Later,
Wolf

[davepellegrene]

Re: Yikes!!!

What seemed to give up the ghost?

I've never had one do that...
Later,
Wolf

I am really shocked. My wife did say that's the loudest she has hear me play it. Still I was listening closely for distortion. It looks like the resistor got hot, but wow! To get that hot to burn.

[davepellegrene]

Re: Just caught my speaker on fire!

There doesn't seem to be anything visually wrong with the resistor either.

[Wolf]

Re: Just caught my speaker on fire!

Dave- get some of these....

http://www.mouser.com/Search/Refine.aspx?sa=&N=4294572354+4294741732+4294619412+1323043&Ne=254227%20254072%20254459%20254136%20254271%20254158%20254613%20254085%20254539%20254148%20254584%20254429%20254559%20254593&Keyword=Arcol+HS25&FS=True&P=1z0z7xgZ1z0wljoZ1z0vl8i&Ntx=mode+matchany&Ntk=Mouser_NoResults

That'll fix it...
Wolf

[DoubleTap]

Re: Just caught my speaker on fire!

Rock on dude! Way to celebrate the birthday of the USA!

[davepellegrene]

Re: Just caught my speaker on fire!

Rock on dude! Way to celebrate the birthday of the USA!

:D

[Pete Schumacher]

Re: Just caught my speaker on fire!

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

Better ventilation.

[davepellegrene]

Re: Just caught my speaker on fire!

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

Better ventilation.

I could have been keeping an eye on things a whole lot better that way. Had no idea things can get that hot.

[curt_c]

Re: Just caught my speaker on fire!

From what it looks like Dave, it was the 4 ohm shunt resistor in the mid network that failed, and the good news is, it is unlikely that it did any other damage when it went. The cable ties on the 1 ohm series resistor look a little discolored as well, but maybe this was just from being adjacent to the shunt resistor, I can't tell from here.

This is the first MiniStatement network failure that I am aware of. You can tell your wife and daughter that it was the designer's fault (me) and not yours, as I didn't anticipate them being played at such high SPL's. -Or maybe it was because I never auditioned that particular Queen CD on them...

In any case, I'm glad the damage was limited to the resistor and board, and I apologize for the scare it must have given you and your family.

I would suggest you rebuild both mid networks with the following modification:

Replace the 4 ohm resistor with two 8 ohm resistors in parallel. This will double the power dissipation to 20 watts. If the 1 ohm looks like it has been overheating, replace it also with two 2 ohm resistors in parallel. None of the other resistors in the design should need to be replaced or modified, but if you see any other indication of overheating, please let me know, so we can address it.

When installing them, make sure the resistors are mounted so they are not flush to the board. This allows airflow on all sides. In addition, insure the crossovers are not covered with foam or stuffing. They need airflow to provide their rated power dissipation.

If I can be of any further assistance please let me know either here, or by email.

C

[robwest]

Re: Just caught my speaker on fire!

Crack-pot engineering!:eek:

Nah! Just kidding!:D (Hey! Don't throw that shoe at me!)

I've never heard of that happening before. Was anything else in the box charred?

[davepellegrene]

Re: Just caught my speaker on fire!

From what it looks like Dave, it was the 4 ohm shunt resistor in the mid network that failed, and the good news is, it is unlikely that it did any other damage when it went. The cable ties on the 1 ohm series resistor look a little discolored as well, but maybe this was just from being adjacent to the shunt resistor, I can't tell from here.

This is the first MiniStatement network failure that I am aware of. You can tell your wife and daughter that it was the designer's fault (me) and not yours, as I didn't anticipate them being played at such high SPL's. -Or maybe it was because I never auditioned that particular Queen CD on them...

In any case, I'm glad the damage was limited to the resistor and board, and I apologize for the scare it must have given you and your family.

I would suggest you rebuild both mid networks with the following modification:

Replace the 4 ohm resistor with two 8 ohm resistors in parallel. This will double the power dissipation to 20 watts. If the 1 ohm looks like it has been overheating, replace it also with two 2 ohm resistors in parallel. None of the other resistors in the design should need to be replaced or modified, but if you see any other indication of overheating, please let me know, so we can address it.

When installing them, make sure the resistors are mounted so they are not flush to the board. This allows airflow on all sides. In addition, insure the crossovers are not covered with foam or stuffing. They need airflow to provide their rated power dissipation.

If I can be of any further assistance please let me know either here, or by email.

C

You are right it is the shunt resistor. By no means was this your fault or a design flaw. I was pushing them very hard with my QSC GX3. I believe is rated at 450 watts per channel at 4 ohms.
I was thinking the same thing paralleling the resistors. I am just happy I didn't do anything to the ribbons. That was my biggest concern. There is also some melted foam so that probably had something to do with it also.

I guess it should tell you something about the volume when my wife was sitting outside watching the DVD through the sliding glass doors.

It is also a really rocken DVD. I was trying to hold back a few notches for the end when Freddy comes out in his white shorts. :o Anyway what an amazing voice he had.
Dave

[davepellegrene]

Re: Just caught my speaker on fire!

I should also ad what a geek my daughter is. As I'm pulling out smoking parts she's snapping pictures so I can post them on techtalk.

Dave

[curt_c]

Re: Just caught my speaker on fire!

Another option would be using higher wattage Arcol or Vishay/Dale non-inductive resistors. They can be purchased at Mouser Electronics.

I agree, Freddie was a great singer/songwriter, and Queen's music was meant to be heard LOUD...

C