Very interesting video. I had an old Vox guitar amp with Alnico drivers in it. One of the sweetest amps I’ve ever owned. I’ve also got those old 50’s Pioneer Alnico drivers and compression horn drivers I mentioned, that i can’t wait to build cabinets for that’ll do them the justice they deserve. Thanks for such a fascinating vid, Janos.
Can't wait for you account on the finished Pioneer cabinets! ; ) I found that whichever Alnico driver I used, I was very happy with them. And, I kept them all... even though my big VOLs are much better than anything else I have, I can go back to my other Alnicos and enjoy them with a big smile. With the ferrite drivers, when I hear them I'm always thinking on how to improve them....
I remember reading that the change to Ferrite only occurred due to a war in the Congo stopping access to Cobalt, needed to produce Alnico and that the early Ferrite motors (1970ish) were engineered to perform exactly like Alnico. The reason they were still popular after Cobalt and hence Alnico became available again is that Ferrite magnets did not demagnetise which is, I’ve read, the one major flaw with Alnico. So sonically it should be impossible to tell the difference between Alnico and (at least) the early Ferrite mag’s that replaced them.
Hi Eddie, indeed, the "durability" was a big factor, as applications that abuse the drivers (eg on the road speakers for bands) need that stability. Also, poorly designed drivers (overhung coils) demagnetised when large signals were cranked through. That did not happen in the lower power tube gear, but transistor era 100s of watts definitively damaged the low-end Alnico drivers. The high quality ones with underhung coils were safe in this aspect, usually you melted the coil first before demagnetization occurred. So, high quality Alnico, home use, perfectly safe. Just don't drop them to hard surfaces. Mines saw ultra high duty service in PA application for 3-4 decades, mounted to their position (before they came to me). They are fine, kicking strong, like new in all aspects. Just beware the Alnicos that were on the road, those were possibly demagnetized to a significant degree due to the rough handling.
I hope you could make a video about the Japanese fringe scene of drivers.. From Goto and Ale.. and the defunct YL Acoustic (grand daddy) and Onken.. giant Permendur magnets.. And the field coil stuff from Japan.. Maxonic, GIP Laboratory, Eltus..
I have been wondering about that as well... so far found no explanation. My suspicion is that ferrite is cheaper than the iron used to close the magnetic gap, so it's more cost effective to use more ferrite and less iron... As the key driving force to change from Alnico to ferrite was lowering the production costs, this additional cost-saving seems as a decision fitting that goal.
@@realworldaudio Thank you very interesting. Qvortrup said that progression is usually to obtain lower cost or get higher efficiency - not better sound. One driving force for using Neodymium like Alnico would to save shipping weight, especially those brands that delivery directly to customers. I just bought 2 vintage 800ohm Philips AD3800AM drivers (better impedance match?) and an Alnico P610 clone from ebay and it has lower freight costs for sure. Like you I build my own tube amps, so I find all your videos enormously insightful, eye-opening and inspiring - so thank you so much for sharing!!
I certainly appreciate all the merits of an alnico driver. Even JBL’s newest, most advanced drivers, at least their woofer used in the M2 speaker, I believe uses an alnico magnet. However, when one uses a 4” voice coil such as in the JBL 2235H woofer with a ferrite magnet, then is one gaining certain efficiencies with such a large surface area of voice coil under the influence of a very strong ferrite magnetic field? And what about field coil speakers which were some of the first used in audio playback?
Sadly, due to the motor construction the advantages of ferrite do not translate well into voice coil gap strength, partially because a lot of the magnetic lines are wasted in ferrite drivers, while Alnico motors keep ALL the magnetic lines in the voice coil gap. Sadly, it's in practice the opposite, ferrite magnet motors do much worse in magnetic strength at the voice coil, despite much higher Total magnetic strength. (Similar to a stronger person but using one arm only...) The benefit of the ferrite motor construction is that they provide longer gaps, which allows higher excursion & higher power handling, although at much lower efficiencies. The field coil is the ultimate for loudspeakers, however, you need a separate amplifier to power the field coil. To execute that at high level, it gets as expensive and as big as your power amplifier! We are suddenly talking about a room dedicated to stereo, and nothing else.... can't fit in normal rooms/systems.
@@realworldaudio So even with symmetrical field magnetic geometry a JBL 2235H may not be exactly as pure as an alnico Altec 515 but I would say it comes fairly close. My friend has a pair of Altec Magnificents and I must say they are indeed magnificent! My only option (as far as I can see) is buying a new pair of Altec woofers from Great Plains Audio for a huge price but then why not get some 604 -8H III’s with the Manta Ray coaxial horn? But then I am looking at over $5k with cabinets and crossover. I understand the scientific angle with magnets but not sure that type of expense is justified in what I may experience in overall enjoyment of music reproduction from what I currently experience from modified JBL 4430’s and how I have them set up.
The 2235H has a 1.2T field strength at the voice coil gap, and the 515C-H versions have significantly higher 1.6T, which translates to the 93dB/Wm (in speaker) of the 2235H VS 102-105dB/Wm (in speaker, depending on cab construction) of the 515C. I'd say though that the 2235H is a superb driver, no need to spend an arm and a leg to go for a new 515... Field coil: what people do not factor in, is that they need an amplifier to provide the field for the coil. That means an amplifier (or a pair of monoblocks) the size and price of your main amplifiers... a whole new level in expenses.
@@realworldaudio I used to have tube mono blocks at 50 watts each in push pull mode (can’t remember which tubes I used) but the design allowed for several types of tubes to be used. After careful comparison, my ears preferred solid state. With my current listening setup I have 600 watt mono blocks that can be switched to 60 watts class A via a switch in the front. So efficiency is not a huge deal and I can easily achieve 110 dB levels in my listening room and that is continuous not counting peaks. That by the way is way too loud for me but 102 dB with 110 dB peaks is very pleasant on many occasions. So 102 dB efficient/sensitive speakers are probably not an absolute necessity? I might add that I can listen at those elevated levels because it is smooth and not harsh and irritating to my ears. The louder I turn it up, the clearer it gets, at least to a point (as mentioned earlier 110 dB is sort of my limit). But I might also add that anything much below 93 dB begins to sound sluggish and wrong. I have another pair of speakers that are 96 dB and they sound good but often a little too bright even with Direc live room correction. So might there be a middle ground between ultimate efficiency/sensitivity and great sound reproduction?
Interesting but I have not heard alnico as I don't have budget maybe one day, anyways I like neo magnet. Actually and I prefer to Ferrite , maybe it's the drivers used
Very interesting video. I had an old Vox guitar amp with Alnico drivers in it. One of the sweetest amps I’ve ever owned. I’ve also got those old 50’s Pioneer Alnico drivers and compression horn drivers I mentioned, that i can’t wait to build cabinets for that’ll do them the justice they deserve. Thanks for such a fascinating vid, Janos.
Can't wait for you account on the finished Pioneer cabinets! ; ) I found that whichever Alnico driver I used, I was very happy with them. And, I kept them all... even though my big VOLs are much better than anything else I have, I can go back to my other Alnicos and enjoy them with a big smile. With the ferrite drivers, when I hear them I'm always thinking on how to improve them....
I remember reading that the change to Ferrite only occurred due to a war in the Congo stopping access to Cobalt, needed to produce Alnico and that the early Ferrite motors (1970ish) were engineered to perform exactly like Alnico. The reason they were still popular after Cobalt and hence Alnico became available again is that Ferrite magnets did not demagnetise which is, I’ve read, the one major flaw with Alnico. So sonically it should be impossible to tell the difference between Alnico and (at least) the early Ferrite mag’s that replaced them.
Hi Eddie, indeed, the "durability" was a big factor, as applications that abuse the drivers (eg on the road speakers for bands) need that stability. Also, poorly designed drivers (overhung coils) demagnetised when large signals were cranked through. That did not happen in the lower power tube gear, but transistor era 100s of watts definitively damaged the low-end Alnico drivers. The high quality ones with underhung coils were safe in this aspect, usually you melted the coil first before demagnetization occurred. So, high quality Alnico, home use, perfectly safe. Just don't drop them to hard surfaces. Mines saw ultra high duty service in PA application for 3-4 decades, mounted to their position (before they came to me). They are fine, kicking strong, like new in all aspects. Just beware the Alnicos that were on the road, those were possibly demagnetized to a significant degree due to the rough handling.
Wow.... finally back after the move.
I'm glad it's over! Time to enjoy life! ; Janos
Cube Audio is in the process of developing electromagnet drivers. Should be quite interesting.
I hope you could make a video about the Japanese fringe scene of drivers.. From Goto and Ale.. and the defunct YL Acoustic (grand daddy) and Onken.. giant Permendur magnets.. And the field coil stuff from Japan.. Maxonic, GIP Laboratory, Eltus..
Why are they not using the neodymium magnet in the style of the Alnico, with a north-south orientation in the centre of the coil?
I have been wondering about that as well... so far found no explanation. My suspicion is that ferrite is cheaper than the iron used to close the magnetic gap, so it's more cost effective to use more ferrite and less iron... As the key driving force to change from Alnico to ferrite was lowering the production costs, this additional cost-saving seems as a decision fitting that goal.
@@realworldaudio Thank you very interesting. Qvortrup said that progression is usually to obtain lower cost or get higher efficiency - not better sound. One driving force for using Neodymium like Alnico would to save shipping weight, especially those brands that delivery directly to customers. I just bought 2 vintage 800ohm Philips AD3800AM drivers (better impedance match?) and an Alnico P610 clone from ebay and it has lower freight costs for sure. Like you I build my own tube amps, so I find all your videos enormously insightful, eye-opening and inspiring - so thank you so much for sharing!!
I certainly appreciate all the merits of an alnico driver. Even JBL’s newest, most advanced drivers, at least their woofer used in the M2 speaker, I believe uses an alnico magnet. However, when one uses a 4” voice coil such as in the JBL 2235H woofer with a ferrite magnet, then is one gaining certain efficiencies with such a large surface area of voice coil under the influence of a very strong ferrite magnetic field? And what about field coil speakers which were some of the first used in audio playback?
Sadly, due to the motor construction the advantages of ferrite do not translate well into voice coil gap strength, partially because a lot of the magnetic lines are wasted in ferrite drivers, while Alnico motors keep ALL the magnetic lines in the voice coil gap. Sadly, it's in practice the opposite, ferrite magnet motors do much worse in magnetic strength at the voice coil, despite much higher Total magnetic strength. (Similar to a stronger person but using one arm only...) The benefit of the ferrite motor construction is that they provide longer gaps, which allows higher excursion & higher power handling, although at much lower efficiencies.
The field coil is the ultimate for loudspeakers, however, you need a separate amplifier to power the field coil. To execute that at high level, it gets as expensive and as big as your power amplifier! We are suddenly talking about a room dedicated to stereo, and nothing else.... can't fit in normal rooms/systems.
@@realworldaudio So even with symmetrical field magnetic geometry a JBL 2235H may not be exactly as pure as an alnico Altec 515 but I would say it comes fairly close. My friend has a pair of Altec Magnificents and I must say they are indeed magnificent! My only option (as far as I can see) is buying a new pair of Altec woofers from Great Plains Audio for a huge price but then why not get some 604 -8H III’s with the Manta Ray coaxial horn? But then I am looking at over $5k with cabinets and crossover. I understand the scientific angle with magnets but not sure that type of expense is justified in what I may experience in overall enjoyment of music reproduction from what I currently experience from modified JBL 4430’s and how I have them set up.
The 2235H has a 1.2T field strength at the voice coil gap, and the 515C-H versions have significantly higher 1.6T, which translates to the 93dB/Wm (in speaker) of the 2235H VS 102-105dB/Wm (in speaker, depending on cab construction) of the 515C. I'd say though that the 2235H is a superb driver, no need to spend an arm and a leg to go for a new 515... Field coil: what people do not factor in, is that they need an amplifier to provide the field for the coil. That means an amplifier (or a pair of monoblocks) the size and price of your main amplifiers... a whole new level in expenses.
@@realworldaudio I used to have tube mono blocks at 50 watts each in push pull mode (can’t remember which tubes I used) but the design allowed for several types of tubes to be used. After careful comparison, my ears preferred solid state. With my current listening setup I have 600 watt mono blocks that can be switched to 60 watts class A via a switch in the front. So efficiency is not a huge deal and I can easily achieve 110 dB levels in my listening room and that is continuous not counting peaks. That by the way is way too loud for me but 102 dB with 110 dB peaks is very pleasant on many occasions. So 102 dB efficient/sensitive speakers are probably not an absolute necessity? I might add that I can listen at those elevated levels because it is smooth and not harsh and irritating to my ears. The louder I turn it up, the clearer it gets, at least to a point (as mentioned earlier 110 dB is sort of my limit). But I might also add that anything much below 93 dB begins to sound sluggish and wrong. I have another pair of speakers that are 96 dB and they sound good but often a little too bright even with Direc live room correction. So might there be a middle ground between ultimate efficiency/sensitivity and great sound reproduction?
Interesting but I have not heard alnico as I don't have budget maybe one day, anyways I like neo magnet. Actually and I prefer to Ferrite , maybe it's the drivers used
Utilise a thrown away driver to lay bare ..........
Educational ss always Janos. Just a simple question: what are those highly praised field coil drivers?
Field coil or elecromagnets are the grand daddy of motor structures, before the permanent magnets discussed here appeared.
@@rickg8015 Hi Rick. Sorry about the late reply. Thank you for the explanation. I would love to hear some one day :) Claus