Hello Jabiru, why don´t you try reading below message one more time it is all in there.(?) AWG32 is a very thin wire. You´ll get at least 90dB sensitivity with this air-transformer.
So, here goes. What you´ll need is AWG24 emanelld copperwire for the primary (inner)winding and AWG32 for the secondary. You´ll need about 6 meters off AWG24 to get
@0.5ohm primary input DC resistance and you´ll need about 262 meters AWG32 to get @141ohm secondary output DC resistance. At the input you should add .68ohm in series with the transformer to (-)input as well as a 4,7uf in series to the (+) input. At the output you should have 1,5 kohm resistor in series with the tweeter (very important to use this resistor otherwise you may melt the diaphragm on transient signals ). Use 5W wirewounds in both cases. The bobin should be 15mm in diameter and 15mm in height.
Good luck and Hear you!
So, here goes. What you´ll need is AWG24 emanelld copperwire for the primary (inner)winding and AWG32 for the secondary. You´ll need about 6 meters off AWG24 to get
@0.5ohm primary input DC resistance and you´ll need about 262 meters AWG32 to get @141ohm secondary output DC resistance. At the input you should add .68ohm in series with the transformer to (-)input as well as a 4,7uf in series to the (+) input. At the output you should have 1,5 kohm resistor in series with the tweeter (very important to use this resistor otherwise you may melt the diaphragm on transient signals ). Use 5W wirewounds in both cases. The bobin should be 15mm in diameter and 15mm in height.
Good luck and Hear you!
Ok, reduce input series resistor (0,68ohm) to zero and the output series resistor to 470ohm. In parallell with with the transformer primary winding a RL series network consisting of a resistor 0.12ohms and a air coil at 0.13mH. The input series capacitor should be 2.7uF for @7400Hz. This gives you 96dB sensitivity with the above mentioned and original transformer. That is all I can contribute you with, the rest I leave to you and others.
Hi, so on your advice and additionally putting a 0.24mH inductor with a 2uF capacitor across the lowther to cut frequencies above 7500Hz the honest truth is I am unable to hear the difference. The HD3P's are audible close up but in the normal listening position disappear - but maybe that is not a bad thing. In any case now the tweeters are mounted they will stay and actually ( in my opinion ) look quite good !
Jabiru
Firstly, did you manage to wind the transformer I adviced? Secondly, did you manage to raise the output 6dB? Because that was what you requested and I answered, now I was just wondering how did that go. I did not see anything in your answer refering to those requests only how you made a complement filter to your Lowter.
HD3P
But on the 8th April you said " Ok, reduce input series resistor (0,68ohm) to zero and the output series resistor to 470ohm. In parallell with with the transformer primary winding a RL series network consisting of a resistor 0.12ohms and a air coil at 0.13mH. The input series capacitor should be 2.7uF for @7400Hz. This gives you 96dB sensitivity with the above mentioned and original transformer. That is all I can contribute you with, the rest I leave to you and others. " - Original transformer - so no I did not wind a new transformer !! I assumed making the changes above would raise the output to 96dB ??
But on the 8th April you said " Ok, reduce input series resistor (0,68ohm) to zero and the output series resistor to 470ohm. In parallell with with the transformer primary winding a RL series network consisting of a resistor 0.12ohms and a air coil at 0.13mH. The input series capacitor should be 2.7uF for @7400Hz. This gives you 96dB sensitivity with the above mentioned and original transformer. That is all I can contribute you with, the rest I leave to you and others. " - Original transformer - so no I did not wind a new transformer !! I assumed making the changes above would raise the output to 96dB ??
Atmospheric pressure is 14.7 psi versus full vacuum. Seems like that could bust the diaphragm. So care is recommended? Someone recommended 1 or 2 psi. inflation pressure. Maybe you had leaks with this method which avoided too much vacuum pressure drop, or not a strong vacuum cleaner? I'd like to know what method was used to seal the diaphragms against the holes in the box.
Care should definitely be taken here when using a vacuum cleaner, otherwise the diaphragm might "implode". The mylar is very strong much stronger than for instance household plastic but of course it has its limit. Use some sort of leakage (hole) or motor regulator for the sucktion strength when the vacuum is applied.
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