Hey all, a ribbon tweeter like to ones in Apogee or Magnepan - if the ribbon were to be run from bottom, over top and continue down backside to bottom - open to each other within the unit - these would effectively cancel each other out and very low output would be realized, correct?
I look at the Apogee Scintilla Tweeter with the larger (2"?) mid aluminum ribbon, and the much thinner (1/4"?) tweeter ribbons on each side in front and back - the 2" mid serves to drive the mids AND separate the 1/4" tweeter ribbons in front and back from canceling each other out, correct?
I am thinking of building a 1" wide ribbon tweeter (I have a Apogee Caliper tweeter unit - no ribbon) and would like to start at bottom and continue over and down backside side - more resistance and more efficiency - but believe they will cancel each other out (if I follow the right hand rule), thus I would likely need a barrier between to prevent cancellation, yes?
I look at the Apogee Scintilla Tweeter with the larger (2"?) mid aluminum ribbon, and the much thinner (1/4"?) tweeter ribbons on each side in front and back - the 2" mid serves to drive the mids AND separate the 1/4" tweeter ribbons in front and back from canceling each other out, correct?
I am thinking of building a 1" wide ribbon tweeter (I have a Apogee Caliper tweeter unit - no ribbon) and would like to start at bottom and continue over and down backside side - more resistance and more efficiency - but believe they will cancel each other out (if I follow the right hand rule), thus I would likely need a barrier between to prevent cancellation, yes?
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If you're talking about both ribbons running in the same magnetic circuit, but the current direction being "up" in one while "down" in the other, then yes they would move in opposite directions and cancel.
Right hand rule #1 here
Right-hand Rules
You could use two separate ribbons and connect them with a separate wire to fix the direction problem, but another issue with running this kind of arrangement is the spacing between them has to be quite small to keep from having other response anomalies related to constructive and destructive interference. At 20 kHz, half a wavelength is only about 0.33 inch.
Right hand rule #1 here
Right-hand Rules
You could use two separate ribbons and connect them with a separate wire to fix the direction problem, but another issue with running this kind of arrangement is the spacing between them has to be quite small to keep from having other response anomalies related to constructive and destructive interference. At 20 kHz, half a wavelength is only about 0.33 inch.
I think you're right about the midrange ribbon separating the front and back tweeters on the Scintilla, thereby improving performance. I have no direct experience with them though, so I'm speculating.
I'm also not sure it's the best idea from a transparency standpoint. People normally try to keep reflective things away from their transducers. If your barrier is fully absorptive at the frequencies of interest it would probably take care of that issue.
If your front and rear output are in phase acoustically, you'll also have bipole radiation, which may or may not matter to you depending on the rest of your design.
I'm also not sure it's the best idea from a transparency standpoint. People normally try to keep reflective things away from their transducers. If your barrier is fully absorptive at the frequencies of interest it would probably take care of that issue.
If your front and rear output are in phase acoustically, you'll also have bipole radiation, which may or may not matter to you depending on the rest of your design.
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Roger, I mean the added thinner looped ribbon in series with the main wider mid ribbon would add overall resistance (good for your amp), and since the looped, thinner ribbon is still in the magnetic field, creates additional HF output, so more efficient overall unit than just wider mid ribbon alone, yes?
1" wide 40" Mid Ribbon tweeter - .1 ohm
1/4" tweeter - four 40" passes - 1.5 ohm
And yes, I understand the Scintilla had the 2" wide Mid and the thinner outer tweeter ribbons in parallel, not series... it did have a goofy but effective maze of aluminum tape to add .7 ohms to the mid ribbon resistance - not a resistor. Kinda like that idea...I think I can do the same, just put that maze of ribbon in magnetic field and put it to use...
1" wide 40" Mid Ribbon tweeter - .1 ohm
1/4" tweeter - four 40" passes - 1.5 ohm
And yes, I understand the Scintilla had the 2" wide Mid and the thinner outer tweeter ribbons in parallel, not series... it did have a goofy but effective maze of aluminum tape to add .7 ohms to the mid ribbon resistance - not a resistor. Kinda like that idea...I think I can do the same, just put that maze of ribbon in magnetic field and put it to use...
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But I think the additional ribbon will act like a resistor, padding down. In this case the additional resistor will make its own sound.