Lately there has been a trend towards using Hiquphon tweeters in car audio applications. While I am not a car audio enthusiast, I can easily understand the difficult environment presented to the tweeter. This is true in the acoustic realm and the climate realm. One gentlemen from Canada prompted me to ask Oskar about how cold weather might impact the OW1. Following this question, Oskar performed a fairly rigorous test. His commentary follows:
Hi Dave,
Sorry it took a couple of days more than I expected to come up with a reliable answer to the cold tweeter question.
I had to check it several times with different units and also several times with the same unit to make sure that the results would be of some value.
Now I feel I have a (non scientific) conclusion for the behavior of the OW1 being frozen down (several times) to at least -21 deg Celsius and back again to normal temperature.
Freezing an OW1 to -21 deg Celsius (I can't go lower with the in-house freezers) seems to be harmless. Or it is at least almost harmless, as I am not 100% sure yet if sensitivity (maybe the magnet change a bit?) may after all suffer a tiny bit.
I found in a couple of tests that a small drop in sensitivity (up to 0,5 dB) seemed to have happened.
Especially to be seen a short time after having settled back to normal temp 20 deg C.
Then again after yet another 24 hours at 20 deg C I could hardly see any difference from the original condition and the new response (sensitivity and curve shapes exactly the same as before cooling down).
I also tried to re-magnetize 2 days later and then found that maybe a tiny drop in sensitivity was brought back to fully normal, so I suspect there might be a small problem with the magnet system, but I am still not sure that this was because of cooling down or because of other reasons (magnetizing twice may add a bit without any other reason - have to check that as well).
I guess I have to do some more tests to be absolutely certain what really happens here.
Anyway, the output from a frozen OW1 (minus 21 deg C) is really bad! This much I can say with certainty!
See attached curves.
So we may conclude in general that OW1 does not function properly at very low temperatures! I doubt any soft dome will (or for that matter any tweeter with a kind of rubber/fabric surround).
RECOVERY - coming back to life again:
But, when it reaches normal 20 deg C again, it works (almost) perfectly normal again.
This seems to be correct after having repeated the warm - cold - warm procedure several times.
I also forced the OW1 to respond to heavy power at low freq (0 - 1000 Hz) while frozen to minus 21 deg C. I did this simply to see if any part of the moving system would crack or otherwise be damaged (after all the surround and coating get very stiff and might not be able to handle high peak-peak movements. But that went well.
Recovery temperature inside however is a slow process, and I would not expect the tweeter to play normal just because the car-cabin temperature reaches, say 20 deg C.
One should expect a delay of quite some time for the temperature inside the OW1 to adjust to cabin temperature and thus until playing at its best again.
Well, this issue may not be completely clarified/solved, but after all dealt with and in my opinion one can conclude whether to use an OW1 or not under very cold conditions in a car.
Can I recommend to use OW1 in cars that are often used under very cold conditions?
- If played cold: NO!
- If played at normal temperature most of the time, and only occasionally frozen: Yes!
- Will the OW1 survive such a hostile environment and treatment?: To the best of my knowledge, Yes!
Best regards
Oskar Wrønding
HIQUPHON
to music with love...
http://www.hiquphon.dk
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