That's quite funny, sounds like I burst into your party or something
(oh, I can fill a pair in a few of minutes, but who wants to rush the job
)Whatever the gas used, I'm sure they were ''filled'' under pressure as this can be regulated with an actual number/unit of pressure and then manufacture would be consistent, but then again I could be wrong.
But seriously, far more useful would be an actual reading of pressure to which they were originally filled, I've experimented with different pressures and fairly content at present, but without the equipment to measure frequency changes at different pressures you can only go with listening pref.
That's quite funny, sounds like I burst into your party or something
Yes and we were celebrating the solutions to conveniently fill the HD3P with air (the correct gas mind you) when you came up with your solution seeming like squared wheeles for us. Well that´s ok but when you for real meant that the previous methods sucked and one should not take offence, that´s only bad manners I think.
I have been experimenting with a couple of transformers for this application, using some Pioneer HPM tweeters as test subjects. They are also metalized kynar film, but curved with a foam backing in place of the "air bubble" of the Audax. The 4 ohm resistor you mentioned is before the transformer. Pioneer used a laminated steel core, and I am playing with a nickel core, but air core sounds like the best option!
Ok, 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!
@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!
Hi nyatt,
unfortunatly I do not know the ratio on this air core (no iron) transformer. I´ve just measured the AWG and DC resistances on the origianal Audax HD3P transformer. The length for the primary/secodary wires I have estimated by tables for DC resistance on each AWG diameters. Anyhow I think this is near
enough to get the same results of the original transformer. In Sweden it is fairly easy to find the enamelled copper wires to use and so it should be in the US I guess. I´m here to assist if you, or others,have further questions.
/Leedh Bo
Do you happen to have a meter that can measure inductance? If so, you can measure the inductance on the primary and secondary windings and I will have all the info I need. And I would appreciate a picture, if possible. If not, my sincerest thanks for the efforts you have gone to. You have gone above and beyond!
As a matter of fact I do.
For the primary I get 0,142mH and for the secondary I get 32,9mH.
Thanks for your apriciations, hope it will work for you.
Sorry no picture yet but I´m still here.
Again, I really appreciate your efforts. I have been playing with old Pioneer HPM Piezo film tweeters, and have been trying different crossovers and step up transformers to get the best results. I am thinking the Gallo CDT in the HPM -016 Omni frame might be really interesting. I will be sure to post my impressions. Thanks again my friend.
So, my best experiments have been with toroidal transformers not intended for this frequency range, but they do well. The voltage gain is about 33, and about twice what the air core transformers you measured (thanks again, I really appreciate the kick-start). My first try is with old Pioneer HPM tweeters. Next will be the Gallos. I am going to try something new with the Gallos. If successful, I will let you know. But even with the aluminized kynar of the old pioneers, there is some magic here.
Glad to see you are progressing with a toroidal tranformer. Are you using a standard 110/3V or have you wounded one yourself? My suggestion is that you only use one capacitor in series with the input forming a 12dB slope together with transformer input inductance. Audax also used a series resistor @1 ohm to smoothen the Q and not loading amp too hard. In their case they used 2-6 uF. If you use an oscilloscope, and I am sure you do, you can lab this out. Audax also use a series output resistor (1k5) for not burning the diaphragm with high voltage spikes. (So they said anyhow)
So keep on testing, hear you.
So keep on testing, hear you.
I am using a small 230/7V toroidal (maybe 10VA). I am not using a ‘scope yet, but I know I should. And I am using a 2uF Polystyrene cap in series with the xformer. It Works well, but I would love to find a purpose built transformer. I don’t want to wind my own (that sounds like too much work, especially with a toroidal), so I am always looking for interesting alternatives. Gallo has stated that the silver ink used in place of aluminizied kynar of the HPM has a much higher voltage rating, so hopefully I can get the most out of these units. I like what i am hearing already!
HD3P
I have just reinflated a pair of these tweeters using a vacuum cleaner ( what a brilliant idea !! ) I sealed them in a container and put them in the freezer for about 10 mins prior and this really helped. Anyway here is the problem, I need to match sensitivity to a pair of Lowther DX3's so from approx 90dB to about 96dB. I intent to wind a transformer from scratch. From an earlier post I will need approx 6m of AWG24 for the primary to give about 0.5 ohm. Can anybody estimate the length or resistance of the secondary that will achieve this. I understand the transformer will have to be slightly larger to hold the extra wire - I don't really understand dB ratios transformer turns and so on, am I correct in thinking that a 6dB increase is perceived as 4 times as loud so will need 4 times the turns on the secondary ?? Can anybody help with this or is there an easier way
I have just reinflated a pair of these tweeters using a vacuum cleaner ( what a brilliant idea !! ) I sealed them in a container and put them in the freezer for about 10 mins prior and this really helped. Anyway here is the problem, I need to match sensitivity to a pair of Lowther DX3's so from approx 90dB to about 96dB. I intent to wind a transformer from scratch. From an earlier post I will need approx 6m of AWG24 for the primary to give about 0.5 ohm. Can anybody estimate the length or resistance of the secondary that will achieve this. I understand the transformer will have to be slightly larger to hold the extra wire - I don't really understand dB ratios transformer turns and so on, am I correct in thinking that a 6dB increase is perceived as 4 times as loud so will need 4 times the turns on the secondary ?? Can anybody help with this or is there an easier way
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.