NHT crossover badly damaged, what caused this??

Hello all,

Long time lurker here; I LOVE this site.

About 9 years ago, I was *given* a pair of NHT 2.9s for helping someone move. I have NO business owning these as I couldn’t afford them then and could barely afford them now used. For the at least the past ~year (I’m kicking myself for not checking things sooner) or so my NHTs haven’t sounded right.. I thought it was due to a move and very sub-optimal furniture positioning in the new place. Then I thought it was my NAD 2200... the output relays went and need to be replaced. I recently bought my first true hi-fi amp, a PSE Studio IV (It’s incredible) and the NHTs STILL did not sound right. After tracking the problem down to the crossover, I pull them out to find that one channel had a badly burned resistor and the other channel showed some signs of heat damage. See photos at linked album.

I then saw that the speakers I have are NOT a matched set; they have differing serial numbers.

What I would like to know is if the crossovers were damaged prior to me receiving them OR if there is anything *I* did to damage these speakers. The speakers are my most prized possession and I want to keep them the rest of my life if possible. I plan on getting the crossovers fixed (NHT is helping! They have been AMAZING). Still, any clue as to HOW such a catastrophic failure occurred? Once I get them fixed, I do not want this happening again.

Quick note: The drivers all check out fine; I measured the resistance across the terminals of each. Thank goodness the crossover took the damage.

Amplification history since I have owned them:

1) NAD 2200 in stereo

2) For about a year, I split preamp out with metal jumpers and horizontally biamped with NAD 2200 on tweeters an NAD 2400 on bass.

3) NAD 2200 developed output relay issue, then tried NAD 2400 in stereo. During this time was in a house with electrical issues (frequent black outs).

4) NAD 2400 developed output relay issue, for the past ~year or so I have run them in stereo with an NAD 3020. I know this is not enough power for them.

My listening habits are very reasonable. I do not like to push the speakers as I have had small listening rooms.

So, any clues on how to avoid this in the future? THANK YOU!



The previous picture link was not working; it's been fixed.

Note the issue is with the board directly behind the speaker terminals; the board at the board of the cabinet looks fine.

Heat damage for crossovers suggests that a lot of power had been sent through the speakers for a sustained period.  It takes more than a few seconds of high power to get a speaker that hot.  I am amazed that the drivers survived, but, then again I saw a crossover that had inductors with plastic bobbins that had melted into a little pool of plastic and the drivers were still good.

I don't know what kind of problems you had with relays in your amp, but, if it meant loud pops, the damage you showed would NOT be the result of such a short-term event.

Thanks Larryi, I will be sure to check the drivers again to make sure all is well. I am at a loss for what could have done this... perhaps something was amiss when I got them and regular use eventually caused the final failure. Sent the crossovers into NHT today and I am very curious as to what they say when they are received.