DIY 802 field coil drivers may be a reality!!

[GM]

For me, there's only two audible advantages to field coils and that's until the advent of Neo mag drivers there's been none as strong as a field coil can be made for lowest practical effective motor strength [Qts] and its ability to be quickly adjusted to vary it over a wide [Qt] without having to insert any parasitic device[s] in the signal chain and all the sound quality [SQ] potential this implies.

GM

[Elitopus1]

For me, there's only two audible advantages to field coils and that's until the advent of Neo mag drivers there's been none as strong as a field coil can be made for lowest practical effective motor strength [Qts] and its ability to be quickly adjusted to vary it over a wide [Qt] without having to insert any parasitic device[s] in the signal chain and all the sound quality [SQ] potential this implies.

GM

So your magnet of choice would be neodymium? I think I have heard you mention this before.

How about ranking them by strength? From strongest to weakest

Neodymium
Field coil
Ferrite
AlNiCo

Is that correct? I would think that ferrite and AlNiCo would be close.

Also where does cobalt fall in this list?

[GM]

Yes, correct; pound for pound, that's my understanding as borne out doing R&D of SOTA slot car motors, but shouldn't be compared on strength alone since each requires its own optimization and the main reason AFAIK why some of the 1st gen ferrites generally don't perform as well as their AlNiCo counterparts.

Neodymium
Field coil
Samarium-Cobalt
Cobalt
Ferrite
AlNiCo

Again, based on doing R&D of SOTA slot car motors between 1965 [AlNiCo SOTA]-2002 [Samarium-Cobalt SOTA]. Ferrite was/is strictly for toys, entry level racing. Like in most racing, weight was a major factor, so with each material change, weight came down significantly for a given motor strength and since armature, brush technology set the upper RPM limit, the S-C magnet was little more than a small sliver of the AlNiCo. Haven't kept up, but assume they're using Neodymium only a fraction of the S-C.

The Cobalts gave no real improvement overall until we decided to grind some up and tested various powder densities in epoxy molded magnets, which netted a big improvement in weight reduction while maintaining field strength.

AlNiCo and S-C really came alive after being broken, so while we sold them intact, those few of us 'in the know' experimented with various configurations of machine damage with nicked corners working for AlNiCo and slicing the S-C into numerous bars spaced slightly apart; a major pain to assemble, but worth it to a true competitor.

Fun times, really miss them!

GM

[Elitopus1]

Very cool GM. Sounds like a fun hobby

As far as speakers, with me being into mostly home audio, I have always thought of neo drivers as being for DJ's or roadies with torn up backs. Lol.

I should get a pair of neo drivers and seriously try them

[mah]

Bill, this one was very hard to find and may not soon be available. Save it for reference.

http://nutshellhifi.com/library/Hill...-in_Emilar.pdf


I think Bfish posted it in a thread about 10 years ago but it didn't come up in my Google searches.

[LowOhms]

Bill, this one was very hard to find and may not soon be available. Save it for reference.

http://nutshellhifi.com/library/Hill...-in_Emilar.pdf


I think Bfish posted it in a thread about 10 years ago but it didn't come up in my Google searches.

Way cool to find that mah. Enjoyed reading it, and seeing a photo of the two authors.

The use of a polyimide film surround with a metal diaphragm, to me, is the mark of Jonas Renkus. His Renkus-Heintz drivers used such a surround. To my limited knowledge, Jonas never commercially tried to offer a field coil driver commercially. In the one inch throat realm, he made nice sounding EA-175s, A for Alnico and EC-175s, C for ceramic.

For a VALENCIA re-do, ( a rough pair I found locally in March of this year ), we elected to exchange the 806 ALTEC drivers for rebuilt EA-175s. Coincidentally, Jonas' son, Algis Renkus, was my client in the early 1980s. I was his stockbroker at Prudential-Bache Securities' Beverly Hills office. Algis was a nice man.


Low Ohms......Jeff Medwin.

[Elitopus1]

Way cool to find that mah. Enjoyed reading it, and seeing a photo of the two authors.

The use of a polyimide film surround with a metal diaphragm, to me, is the mark of Jonas Renkus. His Renkus-Heintz drivers used such a surround. To my limited knowledge, Jonas never commercially tried to offer a field coil driver commercially. In the one inch throat realm, he made nice sounding EA-175s, A for Alnico and EC-175s, C for ceramic.

For a VALENCIA re-do, ( a rough pair I found locally in March of this year ), we elected to exchange the 806 ALTEC drivers for rebuilt EA-175s. Coincidentally, Jonas' son, Algis Renkus, was my client in the early 1980s. I was his stockbroker at Prudential-Bache Securities' Beverly Hills office. Algis was a nice man.


Low Ohms......Jeff Medwin.

Very cool that you knew Algis Renkus.

I have a few of their drivers (both Renkus-Heinz and Emilar). I am listening to some Renkus drivers right now in my small Altecs with 414-16b woofers. The SSD-1400's I have are the smaller version of the more popular SSD-1800 driver. They are similar to an Altec 806 versus the 802.

Running the 414 full range, and bringing in the Renkus drivers in at 6.5khz with a first order xover sounds excellent.

On this system I use a SS 2.8 wpc Realistic amp. It sounds great, and is the perfect volume for family listening levels. I used to run this system with a SE 6bq5 amp prior to using the Realistic