Ascend Sierra Tower + Emotiva XPA-11 = Burnt Voicecoil

[highfigh]

I don't believe Doc's statement is extreme at all, the possibility of a fire with a amp design like that could happen. "Potential" is there for it to happen. Back when EMO had that XPA-2 amp umm around 2011 there was one dude who had one, if I remember he stated it caught on fire, blew up or something like that. But it was found out that he was using it in bridge mode if I'm not mistaken and with the speakers he was driving had dropped to around a 2 Ohm load.

It's likely that the output transistors 'blew up' because they couldn't handle the heat which, as I have posted many times, is what kills components. It's not an explosion, it's a pop, accompanied by a flash and some bad odors. Same goes for power supply filter caps, but they're larger, smell worse and it's a lot louder. If the cover was on the amp,. the fire wouldn't likely spread too far unless it was in a wooden cabinet and the space above it wasn't adequate. Yeah, 2 Ohm loads on amps in bridge mode- sounds like he didn't RTFM.

 

[highfigh]

No huh! 20 watts can fried Tweeter?. I think you missed my point on what Gene's finding of his test results.

Cheap AND more expensive tweeters have died for decades when connected to low power- care to post a quote, so we don't need to search for what you're referring to?

 

[Replicant 7]

Cheap AND more expensive tweeters have died for decades when connected to low power- care to post a quote, so we don't need to search for what you're referring to?

Gene stated (power handling number is meaningless). Plus Gene used two midget drivers to run those test on. I have 3, 6 1/2" driver's in each of my speaker cabinets, and they all have 4 layer voice coils in each driver. If one voice coil burns out I got 3 more backup voice coils! .

 

[TLS Guy]

That's probably a bit extreme- in the 50 years since I started working with audio equipment, I haven't seen an amplifier cause a fire that wasn't short-lived. I have seen caps pop, tubes burst, resistors flash and wires burn, but they weren't speaker wires and they were always contained within the chassis. Amplifier kits, OTOH, are a wild card and if they were built by a hobbyist who didn't know the risks, it could start a fire. Even Sansui at their worst (the R-series receivers and whatever integrated amps they were troweling out at the time) launched output transistors so often one of our service techs used to say "Sansui put those outputs in, to protect the fuses".

In the last episode I had, the polypropylene cone caught fire and set the grill alight. I had to douse it down in a hurry. 90 volts DC or more into 8 or four ohms, is a LOT of heat. It is literally like connecting a speaker to an arc welder.

 

[PENG]

You probably know this but most meters don't react fast enough to measure power output at anything above 60Hz because they don't need to in general use but if it has a frequency counter, it might be accurate enough. Still, a scope is best.

Yes, but you missed the test condition I specified for the test, that is: with the volume of the preamp at minimum, disconnect the speakers and measure the dc voltage. So most meters will do for sure as there is no "power output involved..", just measuring D.C. voltage.

 

[PENG]

I didn't check with a multimeter, but I did connect an old/cheap speaker to the amp... and there wasn't any humming or pops when turning on/off. This is why I was wondering if the happened at a certain temperature, reached under higher load...

Thank you, based on that, I am doubling down on my bet that it was was not DC offset that did your mid woofers in. Most likely the culprit was "over driven..".

 

[jeeper]

Yes, in that case, I would think there is likely a cap in series in the crossover circuit for mid range. I highly doubt dc offset is the root cause in this case if his amp is performing normally otherwise. Given the volume setting so high, I think it is quite possible that the mid woofer just got cooked due to being driven at high level for a prolong period of time.

@jeeper , I think when @ryanosaur asked about the trim level, you said "no boost" but I am not sure if your "boost" means the trim level setting Ryan was referring to, can you confirm that? "Trim level" generally refers to the level settings in the speaker menu, not boost via GEQ, or REQ or the boost set in the source level via the input menu. Also, when that happened, was Audyssey on, if yes, was DEQ on?

All these need to be factored in when trying to correlate volume setting (such as your -6) with the actual amp output level. Anything is possible, but I do think there is a greater chance that the speaker was over driven than it was damaged by dc. By the way one question to ask Emotiva is whether their amps have d.c. offset protection. Even AVRs have such protection.

Trim levels were all set to zero when this happened.

 

[PENG]

55? 20W can kill a tweeter. It's all about heat and lack of ability to dissipate it.

The criteria for power handling specs in consumer speakers aren't the same as what commercial/industrial speaker manufacturers use.

Here's an Ascend page for the Sierra Tower-

Sierra Tower Specifications

From the link-
"1 Half-space 2 Continuous Pink Noise rating is IEC-shaped pink noise with a 6 dB crest factor for 100 hours continuously.
- Continuous Program power is a conservative expression of the system’s ability to handle normal speech and music program material, and is defined as 3 dB above the Continuous Pink Noise Rating.
- 3 Calculated based on power rating and measured sensitivity, exclusive of power compression Note: Reference Axis=0 degrees/on axis, Reference Plane=on axis, Horizontal Plane=on axis. "

https://jblpro.com/en-US/site_elements/control-25av-ls-spec-sheet

The speaker in the link is also rated for use in 'Life Safety' applications, which means that in use for paging during an emergency, it needs to work, period, to the point of total destruction. Not that it's inherently a better speaker, but the testing for this kind of speaker is more stringent because home audio speakers aren't usually expected to receive the max power shown in the spec sheet. IF the amp was at full power + and/or the Marantz was overdriving the input of the power amp, I would say that the expectations for the system are less than realistic and possibly, the setup menu needs to be checked to make sure this can't happen again.

Did you have your coffee yet? It was an Axiom mid woofer, not tweeter..

 

[PENG]

If this has been seen before with this amp, be very careful. A properly designed amp should never cause this issue, not one case. That would make me drop that amp like a hot potato. That is also a potential home fire risk.

?????????????????

What has you seen, that made you say that?

 

[Pogre]

Thank you, based on that, I am doubling down on my bet that it was DC offset that did your mid woofers in. Most likely the culprit was "over driven..".

I think you mean "that it was not DC offset". Not trying to be pedantic, but figure you forgot to type the "not" and it completely changes your sentence, lol.

 

[PENG]

I don't believe Doc's statement is extreme at all, the possibility of a fire with a amp design like that could happen. "Potential" is there for it to happen. Back when EMO had that XPA-2 amp umm around 2011 there was one dude who had one, if I remember he stated it caught on fire, blew up or something like that. But it was found out that he was using it in bridge mode if I'm not mistaken and with the speakers he was driving had dropped to around a 2 Ohm load.

Design like what though? Did you mean he has seen the design of that amp, the XPA-11? If yes, okay I haven't seen the design so no comments. If not, then I would have to agree with highfigh.

 

[PENG]

I think you mean "that it was not DC offset". Not trying to be pedantic, but figure you forgot to type the "not" and it completely changes your sentence, lol.

You caught me again, thank you life saver. Time for my second cup..

 

[Replicant 7]

Design like what though? Did you mean he has seen the design of that amp, the XPA-11? If yes, okay I haven't seen the design so no comments. If not, then I would have to agree with highfigh.

Yes that one, and no to the other one, and than yes I to would have to agree with all 3 of you guys. Don't ask me, I'm I the leader here? I'm following the guy in the red helmet, umm where's is he at?

 

[Verdinut]

Then there are those hemp cone speakers. If you destroy the voice coil, you can smoke the cone!

The Original Hempcone Speaker - Tone Tubby

Tone Tubby speakers are the new sustainable standard for natural sound tonality and cone dependability. A luxury sound based on hard working technology.

www.tonetubby.com

 

[jeeper]

So Emotiva confirmed that dc offset protection is built in, along with a bunch of other faults. Their opinion was that i drove the speakers too hard, causing clipping

 

[Verdinut]

So Emotiva confirmed that dc offset protection is built in, along with a bunch of other faults. Their opinion was that i drove the speakers too hard, causing clipping

IMO, if the amplifier had been clipping, then the tweeter would have been more subjected to blowing than the midwoofer.

 

[Pogre]

IMO, if the amplifier had been clipping, then the tweeter would have been more subjected to blowing than the midwoofer.

I asked Dave the owner and designer at Ascend about that.

"For any other tweeter, yes - heavy clipping would take the tweeter out first. However, the RAAL 70-20 has a unique damping feature (unique only to the 70-20) which enables the ribbon to better handle the problems associated with a clipped signal. This is one of the reasons why I love this tweeter and am willing to pay a fortune to use them..."

 

[Verdinut]

I asked Dave the owner and designer at Ascend about that.

"For any other tweeter, yes - heavy clipping would take the tweeter out first. However, the RAAL 70-20 has a unique damping feature (unique only to the 70-20) which enables the ribbon to better handle the problems associated with a clipped signal. This is one of the reasons why I love this tweeter and am willing to pay a fortune to use them..."

I wasn't aware that the speaker was using a ribbon tweeter. I agree with the fact that such driver as well as some air motion transformer tweeters can handle more power than another type.

 

[Billy106]

Fwiw...I had a mid range unit go...not totally fried but you could certainly tell it was damaged. For the record I wasn't playing it all that loud but the recording was bad most likely....iirc.... Leonard Cohen's "Suzanne" was the recording I noticed it on ...but likely not the culprit.
This is why I recently bought headphones for more actual critical listening.

 

[highfigh]

Gene stated (power handling number is meaningless). Plus Gene used two midget drivers to run those test on. I have 3, 6 1/2" driver's in each of my speaker cabinets, and they all have 4 layer voice coils in each driver. If one voice coil burns out I got 3 more backup voice coils! .

Uh, it's not four voice coils, the voice coil is wound in four layers. Unless it melts, in which case, it's a hunk of Copper or Aluminum that's stuck to the former.

Another cause of driver failure is HF oscillation, but the tweeter and woofer didn't cack, so I would look elsewhere- I'd like to see a full set of parameters for the mid.