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EPI tweeter - unmarked terminals

anytune

anytune

Super Member
I bought a replacement inverted-dome, masonite-flange tweeter for an EPI M90. The tweeter works, but the terminals are unmarked. I have looked closely and cannot find any indication which one is positive and which is negative.
I tested the tweeter briefly using a very low audio signal, then reversing the cables, and could not hear any difference.
I know that with a woofer, wiring it backwards (out of phase) will sound softer with less depth. But again, I can't tell any difference with this tweeter.
The other EPI tweeter, looking at it from the back with the terminals at 6 o'clock, is clearly marked left terminal positive.
Question: Does anyone know if left/positive was standard for these EPI tweeters? If not, is there any risk of damage if I happen to hook it up backwards? Thank you for your assistance.
 
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I don't think there's any risk of damage. You have a 50/50 chance that the tweeter will be out of phase if you connect it incorrectly. However, I don't think that matters much on a tweeter.

Wait for the real experts for a definitive answer though! ;-)
 
There's no danger hooking it up backwards, but the speaker won't sound quite right, since the tweeter output and woofer output will cancel rather than sum (or vice versa depending on whether they are supposed to be in phase (as I suspect) or out of phase. Theoretically all drivers ought to be in phase, but actually having them is phase is complicated because the crossover components change the phase of the signal, and the physical location of the drivers changes how the signals interact at the listening position.
And its not clear that phase matters more than flat frequency response, in fact, probably in the messiness of the real world, with all its unpredictability, flat response is usually way more audible. So often designers will change phase to get rid of a peak or fill in a trough, regardless of correct phase.
But: if the two speakers have tweeters in different phase, they will be cancelling each other at certain distances and frequencies, and this isn't good. so put the signal in mono, face the speakers towards eachother and move them very close to eachother. If the new tweeter is phased wrong, you won't have much high frequency audible, and when you change the phase you will hear much more. Try turning the balance control one side or the other and compare to in the middle.
 
That's a very interesting explanation, Nat. Thank you very much. And thanks to fde and westend also.
 
Anytune,

Just looked at the tweeter I kept and it was unmarked and I just installed it the same as the old tweeter which was the left terminal positve. I have not listened yet as I'am waiting for caps. Did it turn out that the positive was the same on both tweeters.
 
Roger
I went ahead and installed it left/positive and it sounds fine. I did the mono test Nat mentioned and didn't notice any obvious phase issues. We're jamming. Many thanks to all! :thmbsp:
 
Interestingly, some tweeters are deliberately wired out-of-phase with the woofers. Since I have no clue as to why, I'll leave it to the engineers.
 
If the drivers are in phase, their outputs in the area where they overlap will be added to each other, which, depending on the frequency of each driver's roll off, and how steep it is, may cause too much output. Reversing one of the drivers will make the outputs subtract from eachother, so there will be less output.
Of course, in a perfect world, all designers would choose ideal crossover points, and all drivers would be well behaved and predictable in their out of band response, and there would be no budget to be met. We don't live in that world, so reversing phase is an easy solution. Granted it fouls up phase response, but so do so many other things, that it may not be audible.
 
anytune said:
I bought a replacement inverted-dome, masonite-flange tweeter for an EPI M90. The tweeter works, but the terminals are unmarked. I have looked closely and cannot find any indication which one is positive and which is negative.
I tested the tweeter briefly using a very low audio signal, then reversing the cables, and could not hear any difference.
I know that with a woofer, wiring it backwards (out of phase) will sound softer with less depth. But again, I can't tell any difference with this tweeter.
The other EPI tweeter, looking at it from the back with the terminals at 6 o'clock, is clearly marked left terminal positive.
Question: Does anyone know if left/positive was standard for these EPI tweeters? If not, is there any risk of damage if I happen to hook it up backwards? Thank you for your assistance.
Click to expand...


The EPI tweeters have a very large x-max compared to most others. I was able to determine the correct terminal polarities of a few samples by using a battery to check the direction of the inverted-dome movement. These tweeters also have very good power handling.

The displacement was certainly more than 1mm for the units I tested which should be easy to visually resolve for most people with average eyesight.
 
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