be wrote:

This time also make shure that the cavities in the two versions, the alnico and the fieldcoil, have the same size and volume of cavities behind the coil in the magnet structure. In this way you make shure that it is the two magnet types you are listening to and not some irellevant cavity resonance and reverbaration chamber.

Be, I am not sure what you mean. The volume of fieldcoil and core is slightly different then the volume on perm magnet but the cavities behind the coil are not the cavities where pressure passes, therefore I do not think that any resonances or reverberation in magnetizing chamber has any affect to sonic out of the driver.

be wrote:

Maybe the easiest would be to put a fieldcoil into the alnico version also, this would also open up to some experimentations by shorting the coil or even to try the electro-alnico magnet you sugested some time back.

Yes, I had this idea but I do not think that would go into it. Above someone told about an European guy who heated up his permanent magnets and was able to simulate by this the sonic attributes of fieldcoil. In my view it was a sanest thing I heard from fieldcoil crowd. I very much would like to try it myself, but I need a way to recharge the perm magnets as with Alnico the driver would lose magnet force with heating. There is a key in all of it – I do not feel that fieldcoil has any sonic advantages (I feel it is opposite – the fieldcoil sounds inferior) and I do not feel a need to change anything from how my S2 sounds now. However, if the heating up of the magnet would make the difference as expected then it might be a good direction to use “hard” drivers with “loose” cone and “soft” magnetizing force.

be wrote:

"the cavities behind the coil are not the cavities where pressure passes" Yes, but the speach coil and diphragm can "see" the air volumes behind the magnetic gap and will be loaded by the resonanses created, and the radiated sound might be affected also. Think of a 8 inch woofer put in a 10 litre or a 100 litre closed enclosure, no question that that is audible.

"the chamber where the magnet is (would it be perm magnet of electromagnet) is absolutely decoupled from any paths where sound flows"
The situation is the same as the backside of a woofer looking into a closed enclosure, and this relationship is audible.

Also, actually in a compression driver, there will be a narow opening between the inside of the speech coil and the central polepiece in the magnetic gap thru witch the throat and the phaseplug slits are connected to the inside of the magnet!! Audible? I dont know.

"In fact some drivers has no chambers for magnets and keep the space wide open"
The question is if they would sound different if this space where closed?

I think that now that you will make some experiments it would be a pitty if your results would be determinned by something else than what you are exammining, especially since it would be so easy to avoid (by putting something into the perm magnet)  Also it could open up for some new possibillities voicing.

be

Be,

this is an interesting thinking and if you are correct and if there is an opening from front chamber into magnet assembly then the volume of the magnet chamber would certainly affect the sound of the driver. The point that I argue is that such an opening shall not exist. The whole point of a properly made compression driver shall have a very smooth and no ripples transition from the diameter of diaphragm to the diameter of the throat. Any sudden change, any step in the transition is absolutely not acceptable, not to mention an opening into another cavity. Now, saying that I do not insist that such as an opening do not exist. I was trying to recall it but it is not in my mind now. Let look at the common design of a compression driver – where do you see this opening would be?

Anyhow, if such an opening into magnetizing cavity exists then I think it would be with the driver that have non-radial phase plug, like Altec after 808, RCA and many others. The drivers with radial phase have the last layer of the plug covers the diaphragm’s output, at least it is what I think.

Be, if you look at the picture of the S2 then you will see that between the exit of the phase plug and beginning of throat there is a circular channel that violates my view of proper transition in compression driver. This channel is on the side of the throat exit and it more looks like an added volume to post-compression front chamber. The pressure from throat in the way forward toward to the exit does not pass this channel as the channel is almost behind. I never liked this channel, I wrote about it before and I meant to patch it. How it affects sound I do not know. In context of this there I think it is worth to note that this channel is a few mm deep and it does not got all the way across the poll and is not connected with the chamber where the magnet is. So, regardless what kind magnet it would be permanent or electromagnet it would not be relevant from THIS perspective. Again, I do not insist that there is no vent from sound cavities to magnet cavities but I would not like it is. If it was true then the magnet chamber size would be certainly the factor.

BTW, I read recently a feedback for one guy who invested a lot of time in the electromagnets and he has many of them (I think he is associated with Rulit). I do not particular care about his views one of his comments I find interesting. He claims that his electromagnets drivers, being driver from all warned up amp, begin to sound in the way he likes only after 1 hour of operation. This would perfectly comply with the idea of the electromagnets to sound different due to heated magnet structure. So, hypothetically, if we a medium magnet that do not loose magnetic force with temperature and if you wind a heating coil over it with a thermostat, then we would get the same effect. Now, the bigger question would be if the effect is positive in any way. One of the thing that I would like to repeat with my electromagnet is to use non-plastic cones. I had worse sound with electromagnet but was it due to the fact that plastic suspension of the S2 diaphragm got warmed up?

I was under impression that neodymium is more resistant against temperature, mechanical shock and flux modulation, it turned out that I was wrong about temperature:

http://www.intemag.com/magnetic_properties.html

It turn out that Alnico is the best material to heat it up. I just need to have my own magnetizing devise and I would try it.

be wrote:

I just spoke with a guy who have made both permanent magnets and electro magnets for loudspeakers. He said that the reason that electro magnetic speakers have a smoother and more grain free sound, is due to the temperature rise in the mechanical parts of the magnet

Hi Haralanov.

My "friend" said that he made an experiment where he heated a permanent magnet up and thereby made it sound more like a field coil magnet, both with the same front.

If we can take this claim as true, it is evidence that the acoustical-mechanical vibrational properties of a transducer depends on the temperature, this is not counter intuitve to me, especially with the mechanical interfaces causing damping and the temperature dependent softening of glues and insolation of speech coil etc.
I dont think this would be the only explanation, obviously the magneto-hystersis properties of the hard and soft iron parts could in adition be as, or more important.

Regards
be

rullit wrote:

Good field coil speakers mean an entirely different dimension in music reproduction. If I compared ferrit to tap water, AlNiCo would have more or less the range of a middle or maybe, depending on the material of the magnetic wire, high class mineral water, while field coil, manufactured properly and correctly would be the equivalent to mountain water you get directly from the source.

Haralanov,

I would not make any assumption about be’s friend who proposed that the heating up magnet describes the major difference between perm and electromagnet. In fact what he proposed I find very stimulating and to a degree might be very plausible.

I think to confirm it would be necessary to measure an electromagnet driver as soon it went off and then an hour later after it heat up. Why where do you see the people who use electromagnet are trying to talk about facts? They, at least that hat I have seen, mostly stress the “much deeper emotional involvement with music”. Ironically the each time I visited the people with electromagnet inhalation I witnessed that they listed predominately garbage and have musical demand of very limited complexity.  Haralanov, I do not mock you, I juts report the facts of my past experiences.

What I have seen was that electromagnet do have own different sound but I would not describe it as “denser harmonic content” or something that would make the “musical phrases more meaningful”. In fact I personally feel that to a large degree all those comments about advances of electromagnet harmonics come from the facts that the electromagnets are more rolled off at the competitive flux force. Look for instance you, Haralanov, report:

“…typical "screamyness" is still there as if the sound comes from a very little zone, stuffed and compressed in the middle of the speaker with tizzing top octave response …. as it shoots with laser gun right in your eyes. “

They are fear accusation if it is what it is but it is not my expense with my Alnico drivers. In fact my experience with them is that they are lush and very elegant. The harmonic density is to a large degree is the subject of the output tube loading. If your tube runs too idle then you might have the sound you have described. Take your driver with “tizzing top octave response” and short if with a few watt resistors – this will load the tube harder and will take the edge off your divers (as a temp solution). Alternatively run a shit of toilet paper over your driver and see how the transients got eaten. Ironically right alone with subduing of unreasonable transients we got the “denser harmonic content” but pay attention that we do not change magnet yet.

What I am trying to say is that in my view methodologically you all guys do a mistake by comparing badly performing perm magnet drivers with badly performing electromagnet. What you need to do instead is to get the identically good sound from perm magnets and electromagnet and then to observe what one topology can do and another can’t. To comment that one driver sounds screamy and tizzy but another sound “better” is in my view not serious and disrespectful not only to the subject of conversation but also to own time we spend to educate ourselves about the things.

Romy the Cat wrote:

Haralanov, I do not mock you, I juts report the facts of my past experiences.

Romy the Cat wrote:

In fact I personally feel that to a large degree all those comments about advances of electromagnet harmonics come from the facts that the electromagnets are more rolled off at the competitive flux force. Look for instance you, Haralanov, report: “…typical "screamyness" is still there as if the sound comes from a very little zone, stuffed and compressed in the middle of the speaker with tizzing top octave response …. as it shoots with laser gun right in your eyes. “

Romy the Cat wrote:

Take your driver with “tizzing top octave response” and…

Romy the Cat wrote:

What I am trying to say is that in my view methodologically you all guys do a mistake by comparing badly performing perm magnet drivers with badly performing electromagnet.

be wrote:

The diference you observed between high and low impedance fieldcoils, where they in the same unit and did you use the same kind of power supply?

haralanov wrote:

My driver has not even a single trace of  tizzing top end. Tizzines is intrinsic feature of ribbon drivers (including RAAL), not of well designed paper drivers. Actually, the heart of my acoustic system is ultra high performing midrange – high midrange driver with central alnico magnet, wooden spider and leather surround. You could see it here:   http://bgaudio.org/forums/viewtopic.php?f=1&t=17682 Now I’m listening to even better drivers (field coil) powered with 10 x 12V accumulators. You can see a close shot of the paper it uses…

Haralanov, your diver might be a very good MF diver but it does not go to region where the “tizzing” live. It just has too large and to heavy diaphragms for it. You can take driver from 30 and 40s (Telefunken, Klangfilm, Tesla and few others) and accommodate them for MF. They have similar to your diver paper structure and generally they sound fine. However, you can’t not make the claims that those drivers does not do “tizzing” as they are juts MF diver and perform more or less comfortable in sub 7kHz area. What you saying is similar to somebody saying that a compression driver tweeter does not have the “boomy baas”.  I also disagree with ribbons. Tizzines is not an intrinsic feature ribbons, it might be if ribbons are not properly used. But anything if not properly used sound like shit…

The better field coil driver powered with 10 x 12V accumulators? Hm, you claim that you were not able to make a PS that would power your driver to a sufficient level of sound? Are you sure about it? At 12V you can use 5F-6F car capacitors that shall cancel any PS influence… I do not know, the buttery-powered electromagnets is too unpractical in my view.  I do like your diver, the suspensions is very cool but still it is very difficult to evaluate how effective all of it and how it sound in reality unless one heard the thing.

Romy the Cat wrote:

your diver might be a very good MF diver but it does not go to region where the “tizzing” live.

Romy the Cat wrote:

It just has too large and to heavy diaphragms for it

Romy the Cat wrote:

(Telefunken, Klangfilm, Tesla and few others) ... However, you can’t not make the claims that those drivers does not do “tizzing” as they are juts MF diver and perform more or less comfortable in sub 7kHz area.

Romy the Cat wrote:

you claim that you were not able to make a PS that would power your driver to a sufficient level of sound? Are you sure about it? At 12V you can use 5F-6F car capacitors that shall cancel any PS influence

Romy the Cat wrote:

it is very difficult to evaluate how effective all of it and how it sound in reality unless one heard the thing.

haralanov wrote:

You may not believe me, but the driver start to  roll off (very smoothly) after 14kHz and at 20kHz is at -6dB. I intentionally do not use it so high, because I have ultra light weight alnico paper tweeter: http://www.bgaudio.org/forums/viewtopic.php?p=9833971#p9833971  So my eliptical driver is able to reproduce almost all of the high frequency information, and as I already said - without any trace of harshness.

Of course it has no “trace of harshness” – it has too heavy cone to operate in the zone where harshness might take place. Yes, the diaphragm does not work as a piston as the properly implemented break-up might do very good job. I also have no doubts that your driver goes to 14kHz and has -6dB at 20kHz.  However, the question is not how far it goes but what kind HF it reproduce, if it possible to get the same 14kHz from another dedicated HF driver and if those “dedicated” HF might be better in quality. My experience shows that use of light cone MF drivers and to push them into HF does not produce the stimulating enough HF. Even if you got some kind of very unique cone, and 4.4g (with suspension) shall be very good, then how low you driver this 4.4g cone? Thins about the Doppler and intermodulation distortion for this type of the driver… Anyhow, it is not my philosophy to try pushing a driver to work in widest bandwidth – I truly see no reason to do it. You can put on cello the short strings and try to play soprano or mezzo violin, the question would be why one need it to play a quarter? The whole point to have 4 individual instruments in a quarter is because when they play together then the combination of them gives birth of new interesting possibility, particularly in the moments of complex polyphony. Anyhow, your accomplishment with this MF driver might be very good for what you are looking for but it is not a direction that I personally find perspective. All my experiences with similar topology that you advocate lead me to confirmed it.

haralanov wrote:

My field coils are powered ot 120V, not at 12V, and the batteries are wired in series

THAT is VERY interesting in context of this thread. I did not pick it up while you were talking above with “be” about impedance that your driver use 120V magnetizing coil. Do you see advantages in it? A am not sure that I do. OK, less current but who cares? From different perspective you shall have much more isolation on coil to handle high voltage. I do not think it is a problem as well. So, what the advantage? When you were talking about high voltage motors I did not realized that it is 120V!!!! To do it you shall have a coil with high amount of DCR and it would tale a LOT of copper to wind. More turns would make more layer and more layer would make the external layers be less affective from perspective of flux/temperature ration.  I do not know how it all works, I would need to consult with my coil people but I do not immediately see any advantage to go for high voltage in electromagnet. Care to educate me on the subject?

Romy the Cat wrote:

Take (hypothetically only!) your Cat or if you are less lucky your dog. Dump her in bathtub, wash he with soup. Then dry your pet with towel. Then put your pet on a middle of carpet and looks at her fur. It is wet and it is not stick out as it should. Now begin to dry your pet with hair blower for instance. The dryer the pet’s fur will be the more distinctive and the more spatial each individual practical of hair will be. The very same is with upper MF and SET amplifiers.