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Smoked a 3.5R Ribbon?

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Posted on July 3, 2015 at 09:20:23
HiOnFi
Audiophile

Posts: 1645
Location: Florida
Joined: January 11, 2004
Some here may recall I have blown quite a few 3.5R ribbons, mostly using cheap active XOs.

I was so frustrated that I bought a pair of Swan Diva IIs, which have a small 1" tweeter

After getting a handle on how good the Swan Divas sounded full range, bi-amped, using the Parasound P5 (bass management circuit, I decided to see how much more open/better my system would sound using the 3.5R ribbons utilizing the Maggie XO with the Swan woofers

About an hour into warming up the XOs, I was downstairs, when all of a sudden I heard the old familiar lack of high frequencies in one channel (the same speaker where the ribbon blows)

I came upstairs and saw smoke rising out of the top of the speaker. I called Magnepan, but no one there until Monday

Could it be a bad part in the XO, or is it something else?

 

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RE: Smoked a 3.5R Ribbon? , posted on July 3, 2015 at 09:43:51
It seems clear you have an issue you've yet to identify. I don't think it makes much sense to continue replacing ribbons until you find said issue.
It could be the XO, or the power amplifier, or any number of things. If you have someone locally who's a good troubleshooter I would enlist their help.

Dave.

 

RE: Smoked a 3.5R Ribbon? , posted on July 3, 2015 at 11:59:31
neolith
Audiophile

Posts: 4841
Location: Virginia
Joined: February 21, 2002
Contributor
  Since:
December 2, 2004
The only way you can get smoke is by producing heat. Heat is produced by current in a resistance and is I^2 x R. Therefore you have excess current flowing in your tweeter that seems to be bypassing the fuse. Conclusion you must have a short somewhere. I would follow Davey's advice and try to find someone with some technical skills to track down the problem. You are lucky you haven't burnt the house down. FWIW I have never blown a tweeter fuse (when I had them) or a ribbon tweeter. That's not to make you feel bad but just to point out there is something seriously wrong with your speakers.



"Our head is round in order to allow our thoughts to change direction." Francis Picabia

 

RE: Smoked a 3.5R Ribbon? , posted on July 4, 2015 at 08:36:13
In nearly 30 years of playing the ribbons on a Tympani IV-A, I have never "smoked" or damaged a ribbon. I'm not sure this is because they have been fused because it seems well known that a ribbon can blow protecting its fuse. Long ago I got a big kick out of playing those speakers real LOUD.

 

RE: Smoked Ribbon, posted on July 4, 2015 at 11:30:55
Cory M.
Audiophile

Posts: 1172
Location: Midwest
Joined: April 10, 2005
Edit: I read through your post again, but I still must be missing something. You're using the Swan's woofers on one amp, and the Maggie ribbons on another amp, using the original passive, speaker level crossovers? Are you running two pre-outs from the P5, with bass management for the treble section?

You're supposed to be seeing smoke from the fireworks, not your stereo. ;-)


It really sounds as if you have DC flowing through the ribbon in that channel. If so, I would suspect the ribbon's power amplifier. The culprit could likely be a leaky coupling capacitor, or the amp may just need some adjusting.

A way to check this would be hooking up a DMM to the speaker outputs, and measuring the DC offset. Set the meter up in the mV range, or the lowest voltage setting it has. You should be getting less than 20 mV DC. In some amplifiers, you can actually adjust the offset with an internal pot.

I really wouldn't think that it would have anything to do with the XO, with one exception. It could be that the frequency range is set too low on the ribbon in that channel. Even if the knobs are properly positioned, I would still check to make sure that channel is not passing any low frequencies. This could be done by hooking a bass driver up to it. I'd think that the ribbon would go out quickly under those circumstances, however.

Some questions:

This is a preamp level active setup, correct?
Which active XO are you using?
Are you bi- or tri-amping?
Which amp is on the tweeter (/mid)? Tube or SS?
Do you hear any hum? (Likely not, if DC).


Cory


 

RE: Smoked Ribbon, posted on July 5, 2015 at 03:27:25
HiOnFi
Audiophile

Posts: 1645
Location: Florida
Joined: January 11, 2004
Cory, thanks but way above my pay grade

There is one local guy who might know his way around a maggie

 

Guessing, posted on July 5, 2015 at 07:51:35
grantv
Manufacturer

Posts: 7719
Location: B.C.
Joined: January 15, 2002
I have a feeling you are running mid or bass level into your tweeter on that side. Question; does that speaker (prior to blowing the tweeter obviously) sound different than the other?

 

RE: Guessing, posted on July 5, 2015 at 08:25:38
HiOnFi
Audiophile

Posts: 1645
Location: Florida
Joined: January 11, 2004
Unless the OEM XO is wired backwards, no. I double checked that before firing it up

 

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