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NHT crossover badly damaged; what caused this?

AMAZINGLY cool! I am blown away, Thank you again DC!

Just a few more updates.. the "good" channel is also showing signs of major heat at exactly the same spot on the board. I added pictures to the album link in my first post and put one inline below. Problem seems to coming from the same side of the same resistor as in the bad channel. Obviously, this side is not as bad as the other. Note though, per my OP, the serial numbers do NOT match on these. The "good" channel is significantly newer than the "bad" channel. What on earth is happening? Was there some sort of defect in these boards or have I (or someone else prior to me) run these things into the ground. If it's something I did, I want to make sure I never do it again.

Any ideas.. and THANK YOU, this is seriously been an amazing day. I told my wife about your offer DC and she said, "you have a calmness about you I haven't seen in days". I have been worried about my speakers!

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Hmmmm that IS roasted! Looks like some lightening strikes I have seen, or possibly an amp that blew its finals.....were ever it came from I sure hope it's fixed or is bottled up.
My kinds is reflective of many folks here, I am just rocepricating is all.
DC
 
So strange. I have checked every amp I have used with these speakers. None show catastrophic failure. Now I'm wondering if I received them in damaged condition and regular use eventually broke the already weakened joint. I wish I could pinpoint what happened.
 
jquark said:
So strange. I have checked every amp I have used with these speakers. None show catastrophic failure. Now I'm wondering if I received them in damaged condition and regular use eventually broke the already weakened joint. I wish I could pinpoint what happened.
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I would suspect this! What ever was hit, in line first, had surely been turned to burnt toast.........how these managed to play on is something of a wonder!
DC
 
I'm sending them in to NHT today. We will see what happens and I will update here when I have more information. In the meantime, if anyone has any more ideas on what could have caused this, please chime in. And DC, what can I say, thank you SO much for you very warm welcome to AK.
 
You are most welcome. Hope NHT can get you back on the road to recovery. They are a class group. Ken Kantor, who drops in here from time to time, inspired a great company.
DC
 
Could be a marginal crossover design coupled with high power exposure? Dunno but seems your amps are ok. Supercool NHT is offering to help.
 
NHT has been amazing. Just going to ship off the crossovers today.

I never ran these with more than a 100 watt amp. For a small period of time, I biamped with 100 watt to each speaker. However, I don't know the history before I got them.

I'm skeptical of a faulty design. This would have happened to a lot of NHT 2.9s and 3.3s if it was a design problem... I hope NHT can give me a probable cause!
 
I too am banking on pre-existing damage from another owner. You sound like a responsible operator, but this is, well, abuse.

Speaking of which...

 
jquark said:
Agreed! Thank you. But what made the resistor overheat? Or am I focusing on the wrong thing?
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A 15watt resistor can not handle too much moore than these 15 watts. Seen a lot like this in speaker-filters, tiny components like this kills sound quality.

To avoid this for later you could upgrade this resistor by using 2,4 or moore of them in paralell. 2x4ohm in paralell gives 2ohm, 4x8ohm=2ohm and so on. Four 15 watts resistors in paralell (or 20 watts) should make the filter safe.
 
Is that actually the HF board? I see a 11uF & 6uF marked for the other side plus the bypass cap so I am guessing it is. An amp DC dump would be blocked by the caps and since the bypass I can see doesn't appear to be blown out, I'd bet an amp in HF oscillation or flat out clipping for awhile. Eventually the heat build-up starts scorching everything around the resistors.

The NAD 2200 had a soft clipping feature and not a huge amount of power so the damage shown would be tough (not impossible) to do unless you were absolutely flogging the crap out of it. I tend to associate that kind of damage with +10dB drunk distortion blasts. If you didn't do that my bet is on the previous owner. But who could blame him? The NHT 2.9s sort of beg for it.
 
soundmotor said:
Is that actually the HF board? I see a 11uF & 6uF marked for the other side plus the bypass cap so I am guessing it is. An amp DC dump would be blocked by the caps and since the bypass I can see doesn't appear to be blown out, I'd bet an amp in HF oscillation or flat out clipping for awhile. Eventually the heat build-up starts scorching everything around the resistors.

The NAD 2200 had a soft clipping feature and not a huge amount of power so the damage shown would be tough (not impossible) to do unless you were absolutely flogging the crap out of it. I tend to associate that kind of damage with +10dB drunk distortion blasts. If you didn't do that my bet is on the previous owner. But who could blame him? The NHT 2.9s sort of beg for it.
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I *think* this is the HF board; the 2.9s are a four-way speaker; there is another board that these plug into (attaching pic below). These bigger boards look absolutely fine in both channels.

I have a feeling the previous owner abused these pretty good and then my regular use eventually did them in. To double check my listening habits I hooked up my NHT 1.5s and measured the SPL at my listening position; I tended to want to listen in the 75-85 db range; the highest I saw on my meter was 89. I never recall driving the NAD 2200 to clipping or protection.

How could someone want to listen THAT loud?? I assuming you would need to be pushing 105 db or so AT least to cause this kind of heat. Yep, the 2.9s are absolute beasts and are power hungry but wow, this seems to be intense.



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jquark said:
How could someone want to listen THAT loud??
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