Anyone else running field coil based speakers?

[dcathro]

Hi,

 

I am interested to hear other members experiences of running field coil speakers. 

 

What if any differences do you notice over fixed magnet drivers?

 

Also, what differences have you noticed with different quality power supplies and different voltage levels?

 

 

I am currently running a pair of DIY semi open baffle speakers that utilize a Wolf Von Langa 15" field coil bass in a sealed 130L box, and an 8" Supravox widebander in an open baffle. The bass runs at 13V, and the mid at 9V. The tweeter is an Alnico Seas T35.

 

Cheers

 

David

[Pops110]

@Aperalim

[aussievintage]

34 minutes ago, dcathro said:

Hi,

 

I am interested to hear other members experiences of running field coil speakers. 

 

What if any differences do you notice over fixed magnet drivers?

 

Also, what differences have you noticed with different quality power supplies and different voltage levels?

 

 

I am currently running a pair of DIY semi open baffle speakers that utilize a Wolf Von Langa 15" field coil bass in a sealed 130L box, and an 8" Supravox widebander in an open baffle. The bass runs at 13V, and the mid at 9V. The tweeter is an Alnico Seas T35.

 

Cheers

 

David

 

I did not know that had come back into use as a technology.  Very  interesting.  I am thinking back to when the field coil was used as a DC smoothing choke for the power supply for the radio equipment.    That could cause some hum due to the field having some ripple.

 

So yes, a quality power supply would essential.  I wonder how the magnitude of the flux developed compares to rare earth magnets?

 

I know I probably helped answer much, but thanks for posting about this.  Always good to hear of different things.

[dcathro]

14 minutes ago, aussievintage said:

 

I did not know that had come back into use as a technology.  Very  interesting.  I am thinking back to when the field coil was used as a DC smoothing choke for the power supply for the radio equipment.    That could cause some hum due to the field having some ripple.

 

So yes, a quality power supply would essential.  I wonder how the magnitude of the flux developed compares to rare earth magnets?

 

I know I probably helped answer much, but thanks for posting about this.  Always good to hear of different things.

 

They have been back in vogue for some time. I bought my drivers 10 years ago, and there are quite a few companies making them. I am not sure when Supravox began making theirs, or whether it was always part of their production.  Most field coils today run on low voltage (high current) as opposed to the vintage designs.

 

It was Paul Messengers enthusiasm for the technology and my own experience with the superiority of Alnico that enticed me into trying them.

[Lochawe]

I have been running Voxativ field coil 9.87 speaker system with AC-X2 field coil 'full range' driver with spruce timber cones with integrated 2 x 12" active Ripol bass modules per channel for last 4+ years.

https://voxativ.berlin/987

These are powered by 2 Voxativ N5 tube rectifier field coil power supplies each consisting 10 x GZ34 tubes per channel with adjustable DC output from 10V – 20V. 

https://voxativ.berlin/products/t211-dhtyt

Before settling on the far superior N5 I used 2 other solid state field coil power supplies. The Manson NP 9615 as well as the Voxativ N1 12V DC :

https://voxativ.berlin/products/t211-dhtyt-p8c9n-pp2st

 

I have used a variety of speakers over last 35 years that have used some of the most exotic and highly regarded drivers of their day from Dynaudio Esotars, Focal, PHL etc through to a fully active array of Accuton ceramic drivers.  The Voxativ field coil drivers are so much more vivid, dynamic than any other drivers I have used with astonishing clarity and coherence giving the sound a visceral presence I have never heard previously in my room.  Absolare's preamp and 845SET power amps certainly help but the Voxativ field coil drivers themselves are capable of delivering  incredibly nuanced and subtle sounds compared to any fixed magnet speaker I have heard.

 

So for me, field coil drivers have been a revelation.

 

[mwhouston]

5 hours ago, dcathro said:

Hi,

 

I am interested to hear other members experiences of running field coil speakers. 

 

What if any differences do you notice over fixed magnet drivers?

 

Also, what differences have you noticed with different quality power supplies and different voltage levels?

 

 

I am currently running a pair of DIY semi open baffle speakers that utilize a Wolf Von Langa 15" field coil bass in a sealed 130L box, and an 8" Supravox widebander in an open baffle. The bass runs at 13V, and the mid at 9V. The tweeter is an Alnico Seas T35.

 

Cheers

 

David

Wild and unproved claims that tube power supplies for the field coil sound better than SS PSs. Varying field coil EMF I get but tube over SS. And of course you know which one is dearer.  Snake oil anyone? 

[dcathro]

8 minutes ago, mwhouston said:

Wild and unproved claims that tube power supplies for the field coil sound better than SS PSs. Varying field coil EMF I get but tube over SS. And of course you know which one is dearer.  Snake oil anyone? 

Yes, I have read varying stories on the web - must be true :)!

 

I have certainly noticed that a more powerful supply makes a difference on the bass drivers.

[tuyen]

I ran Atelier Rullit Aero 8" full range field coil drivers for a number of years. Still have the drivers and power supply. 
 

ive tried 4-5 diff types of power supplies. They do change the sound. Not always super obvious differences.  Theres deff a sweet spot in terms of  voltage.  For my drivers, feeding 120v dc per driver is nice. Music has life and relaxed. Too low voltage and music sounds bit flat.   Ive tried a tube based supply (tent labs modules), Selenium rect based one as well.  Current psu is a basic choke input LCLC supply. Running the supply to the field coils in series! 
 

These drivers really gave the music a sense of 'life'. Hard to describe.  Definitely not something that would be explainable from a REW frequency response sweep!

 

 

[dcathro]

2 hours ago, Aperalim said:

I have been running Voxativ field coil 9.87 speaker system with AC-X2 field coil 'full range' driver with spruce timber cones with integrated 2 x 12" active Ripol bass modules per channel for last 4+ years.

https://voxativ.berlin/987

These are powered by 2 Voxativ N5 tube rectifier field coil power supplies each consisting 10 x GZ34 tubes per channel with adjustable DC output from 10V – 20V. 

https://voxativ.berlin/products/t211-dhtyt

Before settling on the far superior N5 I used 2 other solid state field coil power supplies. The Manson NP 9615 as well as the Voxativ N1 12V DC :

https://voxativ.berlin/products/t211-dhtyt-p8c9n-pp2st

 

I have used a variety of speakers over last 35 years that have used some of the most exotic and highly regarded drivers of their day from Dynaudio Esotars, Focal, PHL etc through to a fully active array of Accuton ceramic drivers.  The Voxativ field coil drivers are so much more vivid, dynamic than any other drivers I have used with astonishing clarity and coherence giving the sound a visceral presence I have never heard previously in my room.  Absolare's preamp and 845SET power amps certainly help but the Voxativ field coil drivers themselves are capable of delivering  incredibly nuanced and subtle sounds compared to any fixed magnet speaker I have heard.

 

So for me, field coil drivers have been a revelation.

 

Thanks for your reply and the pictures.

 

Your room and setup looks amazing. Do your pictures show the history of power supplies you have used? What were the differences? The build quality on the Voxativs looks stunning. 

[dcathro]

12 minutes ago, tuyen said:

I ran Atelier Rullit Aero 8" full range field coil drivers for a number of years. Still have the drivers and power supply. 
 

ive tried 4-5 diff types of power supplies. They do change the sound. Not always super obvious differences.  Theres deff a sweet spot in terms of  voltage.  For my drivers, feeding 120v dc per driver is nice. Music has life and relaxed. Too low voltage and music sounds bit flat.   Ive tried a tube based supply (tent labs modules), Selenium rect based one as well.  Current psu is a basic choke input LCLC supply. Running the supply to the field coils in series! 
 

These drivers really gave the music a sense of 'life'. Hard to describe.  Definitely not something that would be explainable from a REW frequency response sweep!

 

 

Hi Tuyen, I was tempted to buy some of Oleg Rullits drivers.

 

What are you running now?

[Lochawe]

5 minutes ago, dcathro said:

Do your pictures show the history of power supplies you have used? What were the differences? The build quality on the Voxativs looks stunning. 

Yes, Voxativ drivers are exceptionally engineered and sound very good.

Correct regarding the field coil power supplies.

The order I used the power supplies was:

1. Manson NP9615 adjustable.
2. Voxativ N1 solid state fixed 12V.
3. Voaxtiv N5 Tube rectifier adjustable 10–20V.

Each field coil power supply upgrade seemed to increase the sense of presence and dynamics –  everything just seemed more obvious and apparent – like Tuyen said it is hard to describe.

Ultimately I would like to commission a pair of Tungar field coil power supplies to be built.

The N5 made for a more fluid sound without sacrificing any of the stunning clarity.

[dcathro]

6 minutes ago, Aperalim said:

Yes, Voxativ drivers are exceptionally engineered and sound very good.

Correct regarding the field coil power supplies.

The order I used the power supplies was:

1. Manson NP9615 adjustable.
2. Voxativ N1 solid state fixed 12V.
3. Voaxtiv N5 Tube rectifier adjustable 10–20V.

Each field coil power supply upgrade seemed to increase the sense of presence and dynamics –  everything just seemed more obvious and apparent – like Tuyen said it is hard to describe.

Ultimately I would like to commission a pair of Tungar field coil power supplies to be built.

The N5 made for a more fluid sound without sacrificing any of the stunning clarity.

I am using Mastech HY1505Ds on my Supravoxs, and HP Agilent 10A 30V supplies on the bass.

The massive supplies made a big difference over a Mastech HY3003D - much more presence.

 

Like you, I would like to have some Turngar supplies made for the Supravoxs. Maybe we could work together on this.

 

Cheers

 

David

[Lochawe]

 

2 minutes ago, dcathro said:

Like you, I would like to have some Turngar supplies made for the Supravoxs. Maybe we could work together on this.

Have you seen these before:

https://oswaldsmillaudio.com/ts1

[tuyen]

24 minutes ago, dcathro said:

Hi Tuyen, I was tempted to buy some of Oleg Rullits drivers.

 

What are you running now?

I can happily recommend Oleg's drivers. Works of art.     I last paired the drivers with a pair of 200hz azurahorns.  Worked really well.  This was about 3-4yrs ago. 
 

I went on a bit of a hifi-hiatus for a number of years and sold off lots of gear. Couldn't make myself list the rullits.  Wanted to make a pair of big floorstanding plywood based horns for them.   Have to admit I got too many speaker ideas/projects.  Have some 'a for ara' prototype horn speakers and also in process of attaining parts for Troels 'the loudspeaker 2'.   

[dcathro]

7 hours ago, Aperalim said:

 

Have you seen these before:

https://oswaldsmillaudio.com/ts1

 

Yes, I was reading all about their speakers at the time that they developed their PS. They didn't believe that the PS could make a lot of difference and then someone lent them a Line Magnetics supply.

 

Theirs is a better built, better looking version, using Line Magnetics Tungars. Are you thinking of ordering from them?

 

I almost bought the Line Magnetics PS about 8 years ago, but held back. I was thinking of getting a schematic and building my own. Looking at your setup, I can understand why you would go for the Oswald Mill PS.

[dcathro]

7 hours ago, tuyen said:

I can happily recommend Oleg's drivers. Works of art.     I last paired the drivers with a pair of 200hz azurahorns.  Worked really well.  This was about 3-4yrs ago. 
 

I went on a bit of a hifi-hiatus for a number of years and sold off lots of gear. Couldn't make myself list the rullits.  Wanted to make a pair of big floorstanding plywood based horns for them.   Have to admit I got too many speaker ideas/projects.  Have some 'a for ara' prototype horn speakers and also in process of attaining parts for Troels 'the loudspeaker 2'.   

A friend of mine in the UK is building a pair of the Loudspeaker 2.

 

I understand the process of taking a hiatus. I started my speaker project 10 years ago and gave up, putting them in storage. I had a really bad room, and then problems with my gear - I blew my amp up, my preamp went off, and my cd player packed in.  It wasn't until we moved about 18 months ago and I had a decent room that I was able to get a system up and running well, and then use this lockdown to do the big speakers. 

[tuyen]

I get ya. Im moving to a new place in a week's time and shall finally have space to properly setup a system again. Quite excited about that.  
 

the loudspeaker 2 (and 1) seems like a simple build, but apparently its a lot of work. The BOM is not exactly considered low cost either.  Im putting my own little spin on the design and using a faital pro 18fh510 18" woofer instead of the BMS, and faital pro hf108r instead of the 18sound nsd1095n 1" compression drivers.   Curious to hear how your friend in UK finds goes with it.    Having heard the JBL 4345 studio monitors before, i was hooked on the presentation of a big 4-way and knew something similar would be in my hifi diy journey.  
 

Back to fc power supplies, a friend Martin (azurahorn) is running tungars for his LM555 drivers and 866 mercurys for his jensen woofers.     Incredible music making system. 
 

more info here:

https://www.azurahorn.com/azurahorn_system.html

 

 

[dcathro]

8 hours ago, tuyen said:

I get ya. Im moving to a new place in a week's time and shall finally have space to properly setup a system again. Quite excited about that.  
 

the loudspeaker 2 (and 1) seems like a simple build, but apparently its a lot of work. The BOM is not exactly considered low cost either.  Im putting my own little spin on the design and using a faital pro 18fh510 18" woofer instead of the BMS, and faital pro hf108r instead of the 18sound nsd1095n 1" compression drivers.   Curious to hear how your friend in UK finds goes with it.    Having heard the JBL 4345 studio monitors before, i was hooked on the presentation of a big 4-way and knew something similar would be in my hifi diy journey.  
 

Back to fc power supplies, a friend Martin (azurahorn) is running tungars for his LM555 drivers and 866 mercurys for his jensen woofers.     Incredible music making system. 
 

more info here:

https://www.azurahorn.com/azurahorn_system.html

 

 

 

Moving house is a huge hassle, but a good room is something to look forward to!

 

Bryan (LPG) is in the finishing stages of building some 4345s. They look stunning.

 

Martin' system looks fun, and I love that he has done it himself.

 

I am looking for a schematic to build a Tungar supply ( 8 to 12V). Do you think Martin would share?

 

It seems that you can buy them - expensive, but there is little information for DIY.

[Azura]

Hello, I would be happy to share what I did, over a few posts. I am no great expert  and my design was based on what I had in the shed rather than a clean sheet . I wound secondaries for the 17A Tungar filaments on an old Trimax transformer, but there are easier ways!  We can go thru it.  Building a Tungar supply is not that difficult, and need not be expensive.  It may not get you invited to WE Chateaux parties, those guys only rate the sound of original WE equipment, but it's a fun project. 

 

First off here is a supplier for the tubes:  https://www.aliexpress.com/item/32827239504.html

Ignore where it says 6.3V .  The sheet says 2.2V and 18Amp  - it's not clear.  I am using Philips 1163 which has 2.2V 17A filaments.  If 17 Amp seems rather a lot it is actually still under 40W.  The problem is buying or winding a suitable transformer.  Also you need to wire up the sockets with thick cable.  There is a Hammond transformer, I will look for the number..  Or winding  secondaries on a torroid might be possible.  

 

Sockets are E39  (Edison screw) available here: https://www.ebay.com.au/itm/E39-Screw-Mogul-Ceramic-Socket-Bulb-Holder-Hydroponic-Grow-Light-Lamp-CFL-MH-HPS/350870622682 

 

Next post I will post a schematic of mine and discuss the design issues.

 

very best, martin

 

[davewantsmoore]

 

On 10/10/2020 at 5:31 PM, dcathro said:

different voltage levels?

This is driver dependant, and adjusts the shape of the frequenc response mainly around the system resononance frequency..... so there's no overall generalisation which can be made with high/low - as the main effect would be swamped out by a) the frequency response (which you'd need to correct for to do an apples-apples comparison ... and b ) the driver design.

 

That being said, I would lean towards a strong magnet.

 

On 10/10/2020 at 11:35 PM, tuyen said:

These drivers really gave the music a sense of 'life'. Hard to describe.  Definitely not something that would be explainable from a REW frequency response sweep!

Definitely, you need to use much more sophisticted stimulus than that....eg. some type of tone burst.

 

 

 

[dcathro]

23 hours ago, Azura said:

Hello, I would be happy to share what I did, over a few posts. I am no great expert  and my design was based on what I had in the shed rather than a clean sheet . I wound secondaries for the 17A Tungar filaments on an old Trimax transformer, but there are easier ways!  We can go thru it.  Building a Tungar supply is not that difficult, and need not be expensive.  It may not get you invited to WE Chateaux parties, those guys only rate the sound of original WE equipment, but it's a fun project. 

 

First off here is a supplier for the tubes:  https://www.aliexpress.com/item/32827239504.html

Ignore where it says 6.3V .  The sheet says 2.2V and 18Amp  - it's not clear.  I am using Philips 1163 which has 2.2V 17A filaments.  If 17 Amp seems rather a lot it is actually still under 40W.  The problem is buying or winding a suitable transformer.  Also you need to wire up the sockets with thick cable.  There is a Hammond transformer, I will look for the number..  Or winding  secondaries on a torroid might be possible.  

 

Sockets are E39  (Edison screw) available here: https://www.ebay.com.au/itm/E39-Screw-Mogul-Ceramic-Socket-Bulb-Holder-Hydroponic-Grow-Light-Lamp-CFL-MH-HPS/350870622682 

 

Next post I will post a schematic of mine and discuss the design issues.

 

very best, martin

 

Hi Martin,

 

Just came across your post - thanks for your support. I will comment more tomorrow when I not so tired.

 

Cheers

 

David

[Azura]

Here is the schematic of mine.  Also a WE schematic.  You can use PSUD2 to design your power supply ripple reduction in the normal way by using perhaps the 3B28 option which is an Argon rectifier.  There is no model for the Tungar rectifier so the voltage drop is not going to be accurate.  You will need to aim a bit high and insert some series resistance. 

 

martin

Tungar FC supply for 555.pdf

Edited October 12, 2020 by Azura

[dcathro]

On 11/10/2020 at 11:11 PM, Azura said:

Hello, I would be happy to share what I did, over a few posts. I am no great expert  and my design was based on what I had in the shed rather than a clean sheet . I wound secondaries for the 17A Tungar filaments on an old Trimax transformer, but there are easier ways!  We can go thru it.  Building a Tungar supply is not that difficult, and need not be expensive.  It may not get you invited to WE Chateaux parties, those guys only rate the sound of original WE equipment, but it's a fun project. 

 

First off here is a supplier for the tubes:  https://www.aliexpress.com/item/32827239504.html

Ignore where it says 6.3V .  The sheet says 2.2V and 18Amp  - it's not clear.  I am using Philips 1163 which has 2.2V 17A filaments.  If 17 Amp seems rather a lot it is actually still under 40W.  The problem is buying or winding a suitable transformer.  Also you need to wire up the sockets with thick cable.  There is a Hammond transformer, I will look for the number..  Or winding  secondaries on a torroid might be possible.  

 

Sockets are E39  (Edison screw) available here: https://www.ebay.com.au/itm/E39-Screw-Mogul-Ceramic-Socket-Bulb-Holder-Hydroponic-Grow-Light-Lamp-CFL-MH-HPS/350870622682 

 

Next post I will post a schematic of mine and discuss the design issues.

 

very best, martin

 

 

Hi Martin,

 

I have little experience at building at building high voltage valve supplies, hence my trepidation.

 

I do have the sockets - bought them about 5 years ago, and a friend has a stash of NOS Tungar valves. The Tungars are Continental Electric JAN-GEQ-4B26, packed in 1957.

 

As you say the main issue is the transformer.  I will look over you circuit diagram.

 

Thanks

 

David

[dcathro]

On 12/10/2020 at 11:52 PM, Azura said:

Here is the schematic of mine.  Also a WE schematic.  You can use PSUD2 to design your power supply ripple reduction in the normal way by using perhaps the 3B28 option which is an Argon rectifier.  There is no model for the Tungar rectifier so the voltage drop is not going to be accurate.  You will need to aim a bit high and insert some series resistance. 

 

martin

Tungar FC supply for 555.pdf 426.41 kB · 2 downloads

Thanks Martin,

 

Thanks for this!

 

Some observations:

 

- R2 is a massive variable resistor. I guess that all the resistors have to be high voltage.

- C1 is 2 Farads?

- inductors L2 and L2 are 200mh

- don't know what the ballast lamp is.

 

Thanks for your help

 

David

 

P.S. Silly me, I didn't open the pdf to see that you have your own circuit. 

Edited October 13, 2020 by dcathro

[dcathro]

Thanks for the circuit layout Martin.

 

Some questions:

• You have a main transformer that appears to have dual 20V outputs with a center tap. You also specify a fill transformer with 2.25V output. Is there 2 trannies or just 1?
• Are the 1ohm resistors on the secondary's the giant resistors used to contol the output voltage?
• The large inductors, do you use transformer types?
• My power requirements are a little different from yours, I need between 8 and 12 volts, 2 to 3 Amps, do I need to make any modifications to achieve this?

Thanks

 

David