I know very little about this company.

http://www.kilimanjaro-series.com

It called after an African mountain but the guy sells his drivers out of French ebay.

http://shop.ebay.fr/merchant/chlorophyllin

So, I presume that he is from French Equatorial Africa - had to say – a half of North-Western Africa speak French.

What I wonder if the Kilimanjaro company.  Are the same as the German “Great Vintage Loudspeakers”.

http://www.romythecat.com/Forums/ShowPost.aspx?postID=10467#10467

The drivers look similar but in the Kilimanjaro site there is no mentioning of “Great Vintage Loudspeakers” affiliation.

I think it might be a sign of two things. Ether they just try to crates different companies to promote these drivers at different locations with different flavor. Or the company was spit and somebody started his own venture with the similar products. Both cases are fine by me.

That is still do not answer the most interesting question: how those drivers sound. The $3.5K for a pair of converted JBL375 drivers is expensive but not the end of the world.  I would like them to write the critical review what they do NOT like in the sound of standard JBL375/2440 and what they feel their electromagnetic driver does better. But it would be too rational thing to wish….

twogoodears wrote:

Christine and Wolf Von Langa deal in nice mods, restorations and rebuilding from scratch of classic Altec's drivers, adding the sought-after "field-coils" feature instead using permanent magnets... a snobbish, yet highly considered practice in most exclusive audio circles worldwide to reach better frequencies control and overall better performance...

twogoodears wrote:

BTW: while in Berlin, last May, Frank Schroeder performed an interesting, provoking "blind-test" using '50s and '60 Telefunken's midrange loudspeakers (22 cm diam.), comparing FC vs. PM: almost everyone in the listening panel better ranked and appreciated the FC's - smoother, more natural, less beamy. Will read with interest any (informed) opinion concerning field-coils vs. permanent magnets comparisons.

The subject of field-coils vs. permanent magnets is well beaten at my site. I generally am not pleased how people out there cover this subject. The Frank Schroeder experiment in my view was interning but not conclusive. There was not comment how much that “50s and 60 Telefunken's midrange” driver sound off from what it shell. What it initially badly sounding driver, then what the Schroeder’s excrement would shows? Nothing in my view. The whole point is to take a good sounding driver, change the manger and to see what happen. This Von Langa guy looks like did with JBL 375 and his result  are very interesting because the 375/2440 is a very good driver with very well know performing parameters.

BTW. I did the similar experiments with my S2 driver; you might read the dairies:

http://www.romythecat.com/Forums/ShowPost.aspx?postID=1929#1929

Do not miss the linked threads from there if you want more about the field-coils and I have this subject spread all over the site. In my case I did not find the direction perspective for myself without a very substantial re-research the subject at very different level of commitment and dedication. I was not going to do it. I also do not do see anybody else do the field-coils at serious level of objectives. People out there just wind coils (thankfully it is cheaper then fix magnet), get “ANY sound” and then run and screams like idiots that because it was field-coil then the random crap that they got was the god-send Sound. Well, there is a reason why I consider that most of audio people out there are morons….

BTW, the most intelligent analysis in my view about the subject of the field-coils was exes by a “be” from Denmark. Her is his post:

http://www.RomyTheCat.com/TreeItem.aspx?PostID=10659

I feel that he is on something with it…. If you wish then bring the Wolf von Langa to the table and let him to express his view about the default 2440 vs. the 2440 with electromagnet.

In the thread “Vitavox S2 with Electromagnets.” there was plenty of discussion about RCA 1428 driver. Here is more to it:  the Great Vintage Loudspeakers made a new production of the RCA 1428 driver.

http://www.kilimanjaro-series.com/kilimanjaro-series/a1428wvl/

… they call it A1428WVL.

I am not well familiar with RCA 1428, so it difficult to analyze what is being done in there. It looks like the driver is driven by 30V – a bit too low. Considering the later high voltage discovers I would rather to have 100-200V field coil. The site said that the driver uses “composite cone”. I have no idea what it is. Anyhow, it is second attempt to remake the RCA 1428 after the Cogent. Sure it needs to be heard to see what they are trying to do.

What is very interesting to me is who the customers of Wolf von Langa’s products are. I am sure that the production of those things is expensive but there is dozen or so derange people around the world who curiosity in those things. I am sure to wish Mr. von Langa a prospers business venture but I just do not see it.

Anyhow,  a new Kilimanjaro-Series driver is out. I have no point of reference how good or bad they are and I do not see people talk about Kilimanjaro. It is sad as it would be interesting to hear from Kilimanjaro users.

In fact I posted a question to Wolf and he replied that he can produce the coil of any voltage the customer would like to have. That is good. The below is data by Wolf von Langa:

MI-1428 - original version of the RCA 1428 - especially made for Manhatten Opera House (AKA MI-1437) - 100V field-coil motor, 8 section phasing cap and fibrous cone material (may have been hemp paper).
MI-1428A - second version of MI-1428 w/same 8 section phase plug but a new phenolic cone. 13V/1.7A (about 18 Watt) field-coil motor, 8.4 Ohm DCR, voice coil: about 4 Ohm DCR
MI-1428B - the phasing plug was changed to 15 sections. Same phenolic coated silk cone, except modified with cloth suspension and felt damping rings (replacement cone is RCA Stock No. 26414)
MI-1443 - same loudspeaker as the 1428B except the field-coil volatge is about 115 Volt
MI-1429 - 15" woofer made by Lansing Manufacturing Co. (Model 15X29) - 110V field supply (used in RCA Shearer/Photophone systems with Lansing 285 high-frequency driver)
MI-1434 - same as MI-1429 except field-coil motor is 13V
MI-1435 - same as 1428 except painted black and built to MGM specs for use in Shearer systems (13V, about 26 Watt)
MI-1437 - formerly known as MI-1428 prototype 100V field-coil driver - made for Manhatten Opera House
MI-1438 - formerly known as MI-1432 - companion 100V field-coil 15" woofer to the original 1428, also made for Manhatten Opera House
MI-1443 - same as 1428B except 115V field-coil

Parameter A1428WVL 8 Ohm 
Frequency response = 340 Hz – 16 kHz (w/2350 horn)
Power handling = 75 Watt
Sensitivity = 110 dB @1W/1m
Minimum impedance = 8.3 Ohm
Diaphragm = composite paper cone driven by a 2" voice coil
Flux density = up to 23 kGauss (measured in the gap)
Net weight = 15 kG
Diameter = 178 mm
Horn throat diameter = 2"

audiofilofine wrote:

to reel from 7 volts or 700 volts is equal to the reel. should rather ask why or why 7 or  700 volts. should be asked how you intend to use the horn driver, you should ask graphs of frequency response and power handling. build a field coil driver is easy , it is not easy calculate voltages, impedances and which trumpets used to equalize the driver .. I do not see any of this work in Kilimanjaro. I do not understand how we can provide a driver that works in 7 or 115 volts only changing the solenoid, but can not play sounds good in both cases, changing too many parameters. part of rca driver are like this?  :     http://voltiaudio.com/midrangedrivers.shtml http://www.toutlehautparleur.com/bms/bms-diaph-4591-p-3116.html

Audiofilofine, they all valid points. I agree that to build a field coil drivers is very easy, in fact  much easier then perm magnet and I did wrote before that field coils mast be less expensive then permanent magnet drivers. To calculate voltages and impedances is also VERY simple. A bit more difficult to get the core mass for core built only in case of conversion. If one build a new driver then it is very easy. Again, what does it mean difficult? A qualified engineer shall give you the specification for core mass and coil parameters with an hour of work. It is how long it took for my engineer when I converted my S2 driver to field coil. So, is it difficult? I do not think so.

In my short exchange with Wolf von Langa he told me that he coil build any voltage, even 5000V field coil. I do not know if he said it juts to be nice or he has no idea what take to build 5000V coil. To have a magnetizing coil to be over 5000V rates it shell be VERY different winding and anti-corona isolation employed – it very different then 12-100 coils. Still his opines to do higher voltage coils is a nice fact.
It was mentioned and discussed at this site that higher magnetizing voltage is beneficial as it offsets the sound softening that is comes with coil heating.  It was not my idea but I find it extremely well noted and I am very enthusiastically support the concept. I did not try it personally (I have enough projects on my table for now) but I am absolutely certain that the concept will work perfectly fine.

The biggest question is what else will change if the voltage of solenoid goes up with all other equal conditions? Sure, the different coil impedance but would it be it? I did post the question to Wolf von Langa but he did not reply. I asked him is T/S parameters of the driver change with voltage change – it got to be in my view. Frankly I do not think he have answer to this question. I do not think a lot of people out there do. Audio people generally do not question too much own actions or own thinking. specifically the field coil tend to be absolutely immune to any cognitive sensibility. For whatever reason a typical audio Morons when he see a field coil label he collapse any brain faction and approach the driver banded, backward and with his pants down.

Yes, I do feel that change voltage from 12 V to 120 or to 240V will make a driver to be a different driver. It is possible that the diaphragm and it’s suspension need to be modified to optimize it for higher voltage and working with more energized magnetic field. But where did you see the field coil people ever talk about specifics not to mention to talk about the actual results. Did you even see anybody from the field coil clan to talk about sound of the divers? Never! At least I did hear/see it. Funny, but if they are trying to show off that they talk about sound then they avoidably copy each other words. So, I pretty much discard the field coil experience of others as I did not find it credible. My own experience with electromagnets made me do not want to go there - my perm mans drivers were clearly better. Still I would like to try the high voltage electromagnets as I do feel that there is a lot of promise in there.

About Wolf von Langa’s new RCA drivers. I do not know. To ignite interest of public, at least he public of my level of understanding he need come up with something more than historical essay and a few pictures. I do not care about history and I do not stupidly assume that it was vintage then it shall be good. Wolf von Langa made his own new driver and it need to be treated as a new driver. The fact that it uses the RCA architecture is fine - it make it no better or worse. It is a new driver and it need to be treated as a new driver. It’s it.

audiofilofine wrote:

for me is not new driver , is only a mechanic  puzzle without research . is beautiful  work if make for personal game but is fake if make for business.

be wrote:

Hi! Let me point out that two field coil magnets with identical iron parts, but different field coil wire thiknesses, will at the same field coil power dissipation produce exactly the same magnetic field and the loudspeaker will hence have same parameters. Naturally since the impedance of the field coils are different the required voltage applied will differ. Therefore if fieldcoil drivers with higher voltage ratings tend to sounds better, it must be due to other indirect factors like difference in power suplies or maybe different mechanical or heat conducting characteristics of thin and thick wires.

I agree that the total flux will be the same but therefor in the same iron structure, the field in the gap will be the same, at least in the statical case.

If the system is modulated by the speach coil, a simpel measure of how well the system resists this modulation, is the ratio of resistance to inductance of the field coil, lets call it Fc.
If the  insulation thickness of the field coil wire is negligable, this ratio is unchanged and therefor the dynamic behavior will be the same as well.

Real insulations have a thickness and this inperfection will tend to upset the ballance, so that higher voltage coils by unchaged statical flux will tend to be softer (higher Fc) or more easy to modulate and therefore the unit will have higher distortion due to the magnetic nonlinearities of the pole pieces.

Higher distortion might be beneficial for the sound, I dont know.

The point to make is that it should be possible to get the same result if you put a resistor in series with the field coil voltage source, keeping the voltage over the coil the same by increasing the suply voltage.
Or even using a current source (maximum distortion)

This could, if the speculations are right, open up for tuning the sound by simple means. 
Have anybody experimented with this?

Regards
Erik

 

Romy the Cat wrote:

I think to conduct any more or less methodologically cleaner experiment the best would be to have the field coil with multiple taps. Make the coil standard 600V rated and to design the coil to have let say 4 taps that identically fill the bobbin. Let say it would be 12-48-96 and 192V. Then driving the coil from a powerful PS that has a lot of buffer it would be possible to switch taps on the field coil and adjusting the PS to maintain the same faux.

be wrote:

I agree that the total flux will be the same but therefor in the same iron structure, the field in the gap will be the same, at least in the statical case.

be wrote:

If the system is modulated by the speach coil, a simpel measure of how well the system resists this modulation, is the ratio of resistance to inductance of the field coil, lets call it Fc. If the  insulation thickness of the field coil wire is negligable, this ratio is unchanged and therefor the dynamic behavior will be the same as well. Real insulations have a thickness and this inperfection will tend to upset the ballance, so that higher voltage coils by unchaged statical flux will tend to be softer (higher Fc) or more easy to modulate and therefore the unit will have higher distortion due to the magnetic nonlinearities of the pole pieces. the high voltage coil will at the same flux have higher dissipation, this could mean that it will run at a higher temperature and thereby softening the mooving parts more. If this is the case and is benneficial, the resistor mentionned in the post above could be mounted at the back plate of the electromagnet or the magnet could be insulated to run at a higher temperature!

Be, is that your own thoughts or you had read it somewhere?  

haralanov wrote:

Unfortunately this method is not going to have success, simply because you can't mantain the same flux in gap using the low voltage taps (compared to the 192V tap) because you need substantially more current (192/12=16 times more) flowing through the wire and you are going to melt it.