[jmdesignz2]

Hi
Appreciate anyones help on this?
I am a bit frustrated at this point. I have a pair of Aerial 10T v2 speakers and am now on my 4th tweeter. I am the second owner and have had these for well over 5 years.

They arrived with one dead tweeter - replaced within days.
Then recently- I had an issue where a connection was dislodged which caused spurious noise/transients - that damaged both tweeters.
Since then, all precautions have been taken and no such incidents of overloading / transients have occurred.
However, the left channel tweeter just quit working.

My questions are:
1) how is this happening?
2) could it be something wrong with the crossovers inside the speakers?
3) could there be something wrong with my amps?
4) how can I prevent this?

These are 86db sensitivity speakers, which dip into 3ohm range. The amps are McCormack DNA 1 DLX Monoblocks run off a 30amp dedicated circuit. As mono-blocks, these would put out 380watts per amp at 8ohms.
I am guessing these put out at least 450 watts into 4 ohms and close to 600 watts into 3 ohms?

I could not find any measurements for the monoblocks but found stereo measurements from stereophile 1995 DNA DLX Stereo measurements:

"With clipping defined as 1% THD, the DNA-1 comfortably exceeded its specifications, putting out 178W into 8 ohms (22.5dBW), 315W into 4 ohms (22dBW), and 530W into 2 ohms (21.2dBW). These figures are with both channels driven at 1kHz—except the 2 ohm measurement, which was made with one channel driven so as not to blow the 8A rail fuse. The THD percentage vs output power plots are shown in fig.2. The amplifier's clipping behavior is unusual in that it soft-clips before the distortion shoots up. The sharp "knee" in the distortion traces typical of solid-state amplifiers is absent.
Read more at http://www.stereophile.com/content/mccormack-power-drive-dna-1-power-amplifier-1995-measurements#CpAcWcHMfZA0TZE4.99"
"...FFT on the Deluxe's output when it reproduced a combination of 19kHz+20kHz at 150W into 4 ohms (fig.4). The intermodulation components at 1kHz, 2kHz, 18kHz, and 21kHz are moderately high in level, although the rest of the spectrum is fairly clean."
Read more at http://www.stereophile.com/content/mccormack-power-drive-dna-1-power-amplifier-1995-measurements#CpAcWcHMfZA0TZE4.99

[Mike B.]

Have you measured the DC offset at the outputs of the amp? This can be done with a multimeter set to DC and measure across each channel output terminals.

[richidoo]

DC should be blocked by the crossover high pass filter caps. But always good idea to check power amps for DC.

Two other things to check:
Could be an oscillation from electronics. Since it happens slowly after replacing the tweeter, it's probably not full power oscillation from power amp's output stage because that would fry them in a second with fireworks show as a bonus. But a lower amplitude oscillation could still be originating from the power amp's line level stages. If the power amp is high bandwidth type then it could be ultrasonic (>20kHz) oscillation coming from components upstream of the power amp. Any DIY components, kit built, amateur designed, opamp swaps, tube type swaps, component mods, or vintage components with worn out parts (old electrolytic filter caps) are all suspect for oscillation. An oscilloscope and/or a good tech is required to find and repair the oscillation.

The other thing to check is damaged speaker crossover board from tampering ("modded") or shipping damage, etc. You would probably see this problem on an impedance sweep of the speaker, using a tool like Dayton DATS system from Parts Express ($100.) You could also open up the speaker to inspect the crossover board for shorts, damage or mods. If the tweeter's high pass filter is bypassed by a short circuit, or if the signal from bass/mid drivers is injected to tweeter signal after its high pass filter then the tweeter could have mechanical damage from overexcursion trying to play LF signal. This would be delayed by low volume playing and fail when you crank it up. You would probably hear the bad sound though, so if it sounds "normal" before it fails, then it's probably high freq oscillation.

Good luck

[jmdesignz2]

I just got off the phone with Steve McCormack. Great guy and surprised to get a personal call about the amps and how / what could be causing the tweeters to blow. He agrees that the amps are perfectly capable of driving the Aerial 10T speakers cleanly and without clipping that would destroy the tweeters. The level of sound required to clip long and hard enough would be immediately noticeable and incredibly loud and obvious as Clipping. Thus, I am 100% sure I have never used them at that level in the past two months since installing the new pair of tweeters.

Michael Kelly of Aerial is also great to deal with. I want to make clear that each of these Four tweeters were purchased and not free.
However, having support of a product made in the late 90's is fantastic.

My conversation with Steve of SMCAudio has lead me to believe that there could be some source of ultrasonic noise down chain. I am going to implement a hi freq slope filter in my LIO8 to see if that increases the lifespan of these tweeters.

Steve McCormack is a fantastic stand up guy

[jmdesignz2]

Turns out - it was a loose connection. No fault of the speaker or amplifier 

[max190]

Turns out - it was a loose connection. No fault of the speaker or amplifier 

Where at?

[jmdesignz2]

The Aerial 10T head unit has banana plugs that connect to the body. Due to age, the bananas are no longer as snug. One of those plugs had worked loose. I am going to replace those plugs very soon.