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In Reply to: RE: T IVa tweeter tuning posted by SteveJewels on February 11, 2021 at 02:30:41
A long time ago, there was a movement to use a tiny inductor in series with a ribbon tweeter, to reduce RFI input to the tweeter.
However, I think they were talking micro-Henries - not milli-Henries?
Resistors are normally used to 'tame' the ribbon's output.
Andy
Follow Ups:
The "choke" tweak was promoted by the late Al Sekela and used a 10 uH choke to reduce RF noise. My experience was that it seemed to improved the resolution and imaging of my IIIa.
I married the perfect woman - the downside is that everything that goes wrong is my fault.
Al's tweak (may he r.i.p.)! :-))
Andy
Similar result with the 1.7..
so that means mine are probably 5mH.
Al's recommendation was ; 5522-rc Borne It is a knotted cylinder about 1.6 inches long- An inductor not a resistor. Saved my 1.7's
Micro is for rf applications, Milli is for lower impedance.
Use of the 0.5mh will attenuate at 6db/octave above the calculated frequency. If you just want straight level attenuation use resistors instead
0.5 mH would start rolling off at about 1 kHz in the case of the ribbon tweeter. It is below the range where the ribbon operates.
Do you have the 2 Ohm ribbon + series resistor in your T-IVa?
Yes @Roger Gustavesson here is a pic of the mid\tweeter panel connector.
@ SteveJewelsYour picture shows a Tympani IVa with a higher serial number, probably with the 2 Ohm ribbon and a 1 Ohm resistor behind the panel. You can change that resistor to a higher value. It is soldered.
Lower serial numbers have no tweeter attenuator and a thinner 3 Ohm ribbon. Like this:
Edits: 02/11/21
my post was meant to correct the milli micro henry confusion, so direct you're response to him.
If calculating for audio frequencies at low impedance we are talking milli H.
If radio frequencies, then micro H.
And here's why the possible benefit of micro - calculate and put the coil BEFORE amplification. That's where it might belong because it may be picking up r frequencies.
If you amplifier is oscillating and putting out rf into the speaker - THEN TAKE IT GET FIXED
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