haralanov wrote:

And the very same is with electromagnets. With those so widely used 12V power supplies (Fertin, Feastrex for instance) the sound is always softer than it should be in reality with severally restricted dynamics and transient response. But the people seems to like it...

I agree that each and single electromagnets driver that I head was dull and with restricted transients, something that the unfortunate filedcoil devotee mistakably call “harmonically rich”.

So, you feel that high voltage filedcoil do excite the electromagnets driver somehow? If some then I think if would be worth to try to experiment with high voltage electromagnet.

I will make a few inquires with my cold people and will see if they would propose any rational for it. In any case it might be a good idea to wind a high impedance coil around my S2 driver and to see what it will be able to show off. What voltage you feel is appropriate? Was your selection of 120 was some kind of arbitrarily?  If 120V is better then 12V then why not the 380V for instance? You went to the troubles to use DC battery to drive your 120V coils, why DC battery? How in your view the advantage of DC battery supply relates to the advantage of the high voltage supply? If we accept my above association with a wet Cat as accurate then can your extend that association to the use of DC battery power?

Romy the Cat wrote:

So, you feel that high voltage filedcoil do excite the electromagnets driver somehow?

Romy the Cat wrote:

What voltage you feel is appropriate?

Romy the Cat wrote:

If 120V is better then 12V then why not the 380V for instance?

Romy the Cat wrote:

You went to the troubles to use DC battery to drive your 120V coils, why DC battery?

cv wrote:

But I wonder if, Haralanov, you have experimented with current sourcing the coils - I would imagine that this would vastly reduce the differences you are hearing

cv wrote:

Dave Slagle is in the process of making some low impedance coils for what was a high impedance driver, so he may have the answers, both theoretical, and soon, practical: http://www.hifiheroin.blogspot.com/ (see the Wireman post)

Wireman wrote:

and decided to take them from high voltage to low voltage for safety reasons.

cv wrote:

Yet, I don't think the "safety" aspect may be neglected; I suspect he feels more comfortable with coils running at low voltage than (what I guess was) 200-400V or so.

cv wrote:

Whilst I will take risks with crazy voltages etc for myself, I will not subject others to them, no matter what potential sonic benefits.

cv wrote:

Obviously, targeted experimentation is preferable, but let's not pretend that progress never came from the occasional stab in the dark. So if something interesting comes out of a change that is motivated by making things safer, than why not?

cv wrote:

In any case, *very* interested to hear more about your devices, particularly the long fibre paper cones and leather suspension - are you willing to divulge more?

Romy the Cat wrote:

haralanov wrote: And the very same is with electromagnets. With those so widely used 12V power supplies (Fertin, Feastrex for instance) the sound is always softer than it should be in reality with severally restricted dynamics and transient response. But the people seems to like it... I agree that each and single electromagnets driver that I head was dull and with restricted transients, something that the unfortunate filedcoil devotee mistakably call “harmonically rich”. So, you feel that high voltage filedcoil do excite the electromagnets driver somehow? If some then I think if would be worth to try to experiment with high voltage electromagnet. I will make a few inquires with my cold people and will see if they would propose any rational for it. In any case it might be a good idea to wind a high impedance coil around my S2 driver and to see what it will be able to show off. What voltage you feel is appropriate? Was your selection of 120 was some kind of arbitrarily?  If 120V is better then 12V then why not the 380V for instance? You went to the troubles to use DC battery to drive your 120V coils, why DC battery? How in your view the advantage of DC battery supply relates to the advantage of the high voltage supply? If we accept my above association with a wet Cat as accurate then can your extend that association to the use of DC battery power? Rgs, Romy the Cat

haralanov wrote:

I will not call this excitement, let say it dynamic stability.

Hm, the “dynamic stability”. This is a new objective…

cv wrote:

I suspect [David]he feels more comfortable with coils running at low voltage than (what I guess was) 200-400V or so.

David had commented on this in private email. He looks like has no attitude about it and will be experimenting with it.

cv wrote:

In any case, *very* interested to hear more about your devices, particularly the long fibre paper cones and leather suspension - are you willing to divulge more?

Yes, the driver is very good and it is long know that a properly made leather suspension is the most interesting for MF drivers. The problem is that those cones is VERY difficult to get nowadays, I guess Haralanov use some kind very old diaphragms that he took from old driver. Those cones are not being made like this nowadays.

haralanovwrote:

Don't you think some of the old dirvers use high voltages (some of them 250V) for their electromagnets because of a very rational reason?

Haralanov, Haralanov, let do not mislead ourselves. The old drivers use high voltages for electromagnets not due to the sonic reasons but because economic reasons. They use fieldcoil of electromagnets combined with input choke filter of power supply for the entire unit. I have to note that all of drivers where high ripples just after rectifiers go into fieldcoil of electromagnets sound bad if they used “as is”. I do have quite many of them.

audiofilofine wrote:

are pair of jbl 2420 work with 100-130 volt power supply is with 5u4 tube i use with diy tactrix horn and jensen field coil woofers. crossover at 800 hz 6 db or when use 3 way multiamplification 800-8000 in this case tweeter is old jensen-magnavox.

Audiofilofine, I am sure you have compared the permanent magnet JBL 2420 with 2420 electromagnet. Would you mind to share your observations?

Romy the Cat wrote:

So, I guess you do not measure flux if are getting. You might measure sensitivity and we might presume what when perm magnets has the same sensitivity as electromagnets then the drivers have the same magnetic flux density. Let also presume that when you report that “at 100 volts sounds almost equal” then you have equalized flux and the drivers output. I think you do not see a lot of HF restrain with electromagnet because the JBL 2420 is not so strong HF performer and it rolls off relatively fast, right after 9K-10K. So, you drive your electromagnet with more voltage (in fact with more current) that yields more flux and to “stiffer” sound. Then you wait until the driver warm up and soften sound to the level you like. Here is in my view is the most interesting thing happen. I am in contrary to haralanov do not deny the proposal of the be’s friend that heat might do magnetic benefit (softening). The key question would be in my view if heat induces mechanical benefit of magnetic benefit. If we were are taking about the drivers like Vitavox with new diaphragms or Goto or any other driver what a metal cone surrounded with softer syntactic suspension then I would undeniably felt that the temperature-susceptive plastic suspension doe warmed and change sound. However, the diaphragm in the small JBL 2420 driver is full metal (correct me if I am wrong) and there is absolutely nothing in that driver that might be soften mechanically. So, there is a very high possibility that a hot magnet radiate some kind of different flux that makes some kind of difference. That is the qestuion that I would like to keep as opened question. The Cat

be wrote:

Romy wrote: "However, the diaphragm in the small JBL 2420 driver is full metal (correct me if I am wrong) and there is absolutely nothing in that driver that might be soften mechanically." The speach coil former seems to be made of some kind of fiber and capton, the speach coil wires are fixed by glue and the insulation on them must be a polymer. I think these must be as strongly influenced by temperature as a plastic suspension.

Be,

I thought about it but I do not think that it is the reason. There are two motives:

1)    VC glue is usually epoxy-base and for epoxy 30-40 degree difference is not a difference at all.

2)     If the glue got soften and begin to damp the compliance between the turns of VC and the former then everyone would note that driver would stop to react or became less sensitive to the low level signals. I mean the very minimum currents would be consumed by elasticity of the glue and would not acknowledge by diaphragms. You do not see the field-coil peoples report it. In fact they look like report opposite. I do not have a lot of credibility in their reports as most of what they esteemed sounded very mediocre in my view but I do NOT think that electromagnets do it details.

So, I do not think that the temporary “liquefying of glue” would be the case, but who knows…

Haralanov,

I spoke with a guy who consulted me during my Electo-Vitavox project. He helped me with selection of core material, deliberated the core and calculated the right coil to keep the core mass optimally magnetized. He has over 40 experiences to deal with all of it, so I pretty trust his expertise. He read your posts and I asked him if what you report has any justification. He was supervised with my question as according to him what you report is very self-evident. He insisted that higher voltage will substantially fasten rise time and will make VC to react much faster. I asked him why his did not tell me about it before and he replied: “You did not ask”.

Well, if so then you, Haralanov, have “discovered” a cool way to cure those always inappropriately soft-sounding to my taste electromagnet drivers. Most of the electromagnets that I have seen were under 20V, I think the first RCA versions used 110V and they switch to 12V… and no one Moron had noticed it. So, the high voltage can inhale some transient live into them – that is cool and it has revised my interest in the electromagnets.

I have ordered an experimental coil for my Vitavox. It will be with anti-corona measures (vacuum impregnated and so on) and I asked the coil to be able to be rated for 400V-450V. I think (home) sometime in the end of summer or during the fall I will have my fully functional playback back and will be able to try it. Thanks, Haralanov for the high-voltage tip, I am VERY surprised that no one spoke about it before. I am not sure about your battery experience – I think experimenting with different type of power supplies and filtering would be more fruitful, but the idea to excite and to energy the field with more voltage I think is very much worth to explore.

Romy the Cat wrote:

Haralanov, I spoke with a guy who consulted me during my Electo-Vitavox project. He helped me with selection of core material, deliberated the core and calculated the right coil to keep the core mass optimally magnetized. He has over 40 experiences to deal with all of it, so I pretty trust his expertise. He read your posts and I asked him if what you report has any justification. He was supervised with my question as according to him what you report is very self-evident. He insisted that higher voltage will substantially fasten rise time and will make VC to react much faster. I asked him why his did not tell me about it before and he replied: “You did not ask”. Well, if so then you, Haralanov, have “discovered” a cool way to cure those always inappropriately soft-sounding to my taste electromagnet drivers. Most of the electromagnets that I have seen were under 20V, I think the first RCA versions used 110V and they switch to 12V… and no one Moron had noticed it. So, the high voltage can inhale some transient live into them – that is cool and it has revised my interest in the electromagnets. I have ordered an experimental coil for my Vitavox. It will be with anti-corona measures (vacuum impregnated and so on) and I asked the coil to be able to be rated for 400V-450V. I think (home) sometime in the end of summer or during the fall I will have my fully functional playback back and will be able to try it. Thanks, Haralanov for the high-voltage tip, I am VERY surprised that no one spoke about it before. I am not sure about your battery experience – I think experimenting with different type of power supplies and filtering would be more fruitful, but the idea to excite and to energy the field with more voltage I think is very much worth to explore. The Cat