Anyone else running field coil based speakers?

[Azura]

Hi David, What are the filament voltage / current specs for those Tungar tubes?  Unless you are getting a custom wound transformer wound it may be easier to look for separate transformers. One for filament supply and another for your Field coil supply. 

 

There is a 30A 2.5V - 0 - 2.5V Hammond transformer that may  be suitable but it is 110V primary.

https://au.mouser.com/ProductDetail/Hammond-Manufacturing/167X5?qs=%2BICfH0Hx1eRN1QuKoC83mQ%3D%3D

 

perhaps the best way to go about designing hte FC power supply is first look for some low Henry, Low resistance chokes of the order of 30mH,  1 -2 Ohm DCR.

 

Then you can calculate the right transformer needed.

 

martin

 

 

[dcathro]

  On 16/10/2020 at 1:03 PM, Azura said:

Hi David, What are the filament voltage / current specs for those Tungar tubes?  Unless you are getting a custom wound transformer wound it may be easier to look for separate transformers. One for filament supply and another for your Field coil supply. 

 

There is a 30A 2.5V - 0 - 2.5V Hammond transformer that may  be suitable but it is 110V primary.

https://au.mouser.com/ProductDetail/Hammond-Manufacturing/167X5?qs=%2BICfH0Hx1eRN1QuKoC83mQ%3D%3D

 

perhaps the best way to go about designing hte FC power supply is first look for some low Henry, Low resistance chokes of the order of 30mH,  1 -2 Ohm DCR.

 

Then you can calculate the right transformer needed.

 

martin

 

 

Expand  

Hi Martin, 

 

It is the same as the GE 189049, 2.2V at 17A. I also ordered some tubes via the link you provided.

 

Mundorf make some transformer based inductors at 27mh or 33mh ~ 1 ohm

 

How high can the TX secondary voltage be?

 

Thanks David

 

[Azura]

With a choke input supply using two of those chokes (entered as 2 Ohm) the transformer will need to be about 45V - 0 - 45V  rated at 160VA minimum.  

 

It would be possible to zero in a bit if you have the transformer regulation spec.   

I am assuming  a 3B28 argon rectifier is similar to a Tungar rgds voltage drop. 

 

[Azura]

If you had a 38V - 0 - 38V  5A transformer with 5% regulation and the chokes with  1 Ohm DCR it would look like this...

 

[Lansche plasma guy]

I just wanted to thank everyone for this thread!

 

Threads like these with fantastic contributions from so many people are one of the things that make our community and Stereonet such a wonderful oasis from the all the crap that sometimes goes on in the world (Covid i'm pointing at you).

 

LPG

[dcathro]

  On 17/10/2020 at 1:52 AM, Azura said:

If you had a 38V - 0 - 38V  5A transformer with 5% regulation and the chokes with  1 Ohm DCR it would look like this...

 

Expand  

 

Hey Martin, thanks for these simulations!

 

What confuses me is where the other transformer comes in with 2.5V rails.

 

Am I correct in understanding that the voltage is varied via variable resistors into the tungars?

 

Cheers

 

David

[dcathro]

  On 17/10/2020 at 2:02 AM, Lansche plasma guy said:

I just wanted to thank everyone for this thread!

 

Threads like these with fantastic contributions from so many people are one of the things that make our community and Stereonet such a wonderful oasis from the all the crap that sometimes goes on in the world (Covid i'm pointing at you).

 

LPG

Expand  

 

Field coils are certainly in the weird and wonderful camp, and are more DIY than commercial. I am hoping that there are more people running field coils, or people who are considering them.

 

I have come across a few people on WBF who are running field coil systems.

 

Perhaps this thread will turn into a future resource. I will certainly post everything that I learn here.

 

Cheers

 

David

[dcathro]

  On 18/10/2020 at 3:44 AM, dcathro said:

 

Hey Martin, thanks for these simulations!

 

What confuses me is where the other transformer comes in with 2.5V rails.

 

Am I correct in understanding that the voltage is varied via variable resistors into the tungars?

 

Cheers

 

David

Expand  

OK, I understand, the other transformer is to power the filaments, that are marked with an X on your circuit. On the WE circuit it is a separate secondary on the mains transformer.

 

I noticed on your circuit diagram that you are driving two 555s from the one supply. Given that I need 8 to 12 volts, I assume that I will need a supply for each driver.

 

A mundorf BN100 choke 33mH has a DC resistance of 0.840hms and cost about $100.

 

It might be easier to get a power transformer ( or pair) made with all the secondary's like in the WE circuit. 

[Azura]

What is the current you need per channel?  Tungars are high current diodes so there's no need to build two supplies.  If you want isolation between the channels you can split the output via separate chokes like I did.

 

It might be easier to get the filament transformer wound separately on a torroid - just a few turns of thick cable. The important thing is to get it clamped to prevent buzz.  The high currents will induce a lot of force.

 

You could get a few taps on a conventional full wave trannie to get the voltage you need. Try and eliminate teh need to adjust output with series R.

 

martin

[dcathro]

I am still fine tuning the crossover and playing with the FC voltages. At the moment the Supravoxes are drawing 9.8V at 2.3 amps.

 

I think some variability would be useful. I certainly don't want to power the drivers in series.

 

Would an EI not be more structurally solid than a toroid? I was thinking I could try Voller to make one.

 

On you supply, when you split the output you had 80mH chokes. Did you make your own?

[Azura]

I happened to have two chokes that were made for 1.5A filament supplies. And one that was good for 3A. 

 

The best thing is to discuss it with your winder.  The challenge is to keep it cool and quiet.  You will find that small resistances of wire etc make a big difference to the voltage at the driver  FC  due to the high current.  That's why you may need that variable power resistor (rheostat).  Aim high and add series resistance til you get the output you want.

[Andy Moore]

I have been using Atelier Rullit aero 8 field coils for over three years. They are mounted in Seimens Klangfilm reproduction open back cabinets. What I love about field coils is their clarity and dynamics. What I love about the Rullit’s in particular is that they are designed to be used in free air or front horns, their light cellulose cone, light leather suspension, huge field coil magnets and phenolic spider. They stop and start like nothing else, except for compression drivers. And they are most certainly full range. No augmentation required. Being designed to work in free air means no more box. I can never go back to box speakers. 
 

Mounted in the OB Seimens baffles these are the most open, natural, dynamic, live like speakers I have every heard. And the mid bass is just extraordinary. I hear life like resolution that is missing with other speakers. I am using a simple bridge rectifier PSU that I had made. Keen to build a new PSU using mercury vapour rectifiers soon. 
 

Regards, Andy 

[Azura]

Stunning looking, I know what you mean by the sound as I had a pair of Tuyen's Rullits here on 160 Hz le cleac'h horns. You make me think of trying my Jensen 12As on front horns.  

 

Here is another power supply I built for them.  Simple CLC with a Russian 5U4G.  

 

martin

[dcathro]

  On 18/10/2020 at 10:22 AM, Azura said:

I happened to have two chokes that were made for 1.5A filament supplies. And one that was good for 3A. 

 

The best thing is to discuss it with your winder.  The challenge is to keep it cool and quiet.  You will find that small resistances of wire etc make a big difference to the voltage at the driver  FC  due to the high current.  That's why you may need that variable power resistor (rheostat).  Aim high and add series resistance til you get the output you want.

Expand  

Hi Martin, 

 

If I go with the Mundorf 33mH chokes at 0.84 ohms, and order a 35V transformer, I should have enough voltage that I can vary with a rheostat to get between 9V and 13V? If I  split the circuit as you have done, do I  need more volts, or is it just a matter of more amps?

 

With the Reohstats, is there a resistance range that I need?

 

Sorry that I am so inept at this.

 

I will approach Souther Electronics about making up the transformers.

 

Thanks

 

David

[Andy Moore]

  On 20/10/2020 at 2:51 AM, Azura said:

Stunning looking, I know what you mean by the sound as I had a pair of Tuyen's Rullits here on 160 Hz le cleac'h horns. You make me think of trying my Jensen 12As on front horns.  

 

Here is another power supply I built for them.  Simple CLC with a Russian 5U4G.  

 

martin

Expand  

Martin, stunning power supply! I am hoping to build a psu based on mercury 816 as the Rullit’s need high voltage low current, the opposite of Tungar. 

[dcathro]

  On 19/10/2020 at 10:08 AM, springcreek said:

I have been using Atelier Rullit aero 8 field coils for over three years. They are mounted in Seimens Klangfilm reproduction open back cabinets. What I love about field coils is their clarity and dynamics. What I love about the Rullit’s in particular is that they are designed to be used in free air or front horns, their light cellulose cone, light leather suspension, huge field coil magnets and phenolic spider. They stop and start like nothing else, except for compression drivers. And they are most certainly full range. No augmentation required. Being designed to work in free air means no more box. I can never go back to box speakers. 
 

Mounted in the OB Seimens baffles these are the most open, natural, dynamic, live like speakers I have every heard. And the mid bass is just extraordinary. I hear life like resolution that is missing with other speakers. I am using a simple bridge rectifier PSU that I had made. Keen to build a new PSU using mercury vapour rectifiers soon. 
 

Regards, Andy 

Expand  

 

Hi Andy,

 

Another Rullit! Who made the cabinets/

 

the huge advantage you have is no crossover.

 

Thanks for sharing.

 

Cheers

 

David

[andyr]

  On 19/10/2020 at 10:08 AM, springcreek said:

 

And they are most certainly full range. No augmentation required.

 

Expand  

 

So the one driver delivers 20Hz to 40kHz, Andrew???

 

Andy

 

[dcathro]

  On 20/10/2020 at 8:22 AM, andyr said:

 

So the one driver delivers 20Hz to 40kHz, Andrew???

 

Andy

 

Expand  

 

50hz to 15Khz is full range!

 

My widebanders only do 50hz to about 6Khz, and my tweeters are -6db at 20Khz.

[Andy Moore]

  On 20/10/2020 at 7:57 AM, dcathro said:

 

Hi Andy,

 

Another Rullit! Who made the cabinets/

 

the huge advantage you have is no crossover.

 

Thanks for sharing.

 

Cheers

 

David

Expand  

Thanks David, the cabinets were made by a good friend of mine. He did a wonderful job. 
 

Having no crossover is such a big advantage. No dulling of the transients, no phase issues, just a piece of wire between my output transformers and the drivers. I replaced the binding posts on the drivers with WBT Nextgen. 
 

Every tiny detail comes through. The cabinets are also much thinner than normal (15mm) and shed energy fast and sound lively, but it does not hamper the sound. I use no deadening or wadding and no bracing. 
 

Cheers, Andy

[Andy Moore]

  On 20/10/2020 at 8:22 AM, andyr said:

 

So the one driver delivers 20Hz to 40kHz, Andrew???

 

Andy

 

Expand  

They do 15k to 40hz. That is where the music lives. I have no need for more. I have heard many, many speakers that do 20hz to 20k and they all bore my to tears. I wouldn’t swap these speakers for anything on the planet, no matter what technology or cost

[dcathro]

  On 20/10/2020 at 9:29 AM, springcreek said:

Thanks David, the cabinets were made by a good friend of mine. He did a wonderful job. 
 

Having no crossover is such a big advantage. No dulling of the transients, no phase issues, just a piece of wire between my output transformers and the drivers. I replaced the binding posts on the drivers with WBT Nextgen. 
 

Every tiny detail comes through. The cabinets are also much thinner than normal (15mm) and shed energy fast and sound lively, but it does not hamper the sound. I use no deadening or wadding and no bracing. 
 

Cheers, Andy

Expand  

 

Thanks Andy,

 

Are the cabinets open baffle?

[Andy Moore]

  On 20/10/2020 at 8:54 AM, dcathro said:

 

50hz to 15Khz is full range!

 

My widebanders only do 50hz to about 6Khz, and my tweeters are -6db at 20Khz.

Expand  

Yes absolutely. So many speakers have wider frequency response but lose the life and dynamics of the music. Most of the speakers that do 20-30hz I’ve heard don’t have natural sounding bass or midbass. And almost none have kick in the midbass. The Rullit’s in the wide baffle kick hard. I have not heard another speaker that has the resolution in the bass that the Rullits do. Old school blues sounds extraordinary through them. I drive them with 3.5 watts and they stomp and scale with ease. 

[Andy Moore]

  On 20/10/2020 at 9:35 AM, dcathro said:

 

Thanks Andy,

 

Are the cabinets open baffle?

Expand  

Yes David. 

[andyr]

  On 20/10/2020 at 8:54 AM, dcathro said:

 

50hz to 15Khz is full range!

 

Expand  

 

Not as far as I am concerned!  

 

16Hz to >20kHz is my definition of 'full range' ... but if you don't listen to:

a. (pipe) organ music, and

b. classical piano or violin music

 

... you probably don't know WTF I am talking about.  

 

(I run Maggies - tweeters rated to 40kHz - with subs ... which greatly increase my enjoyment of:

• Bach organ music
• Yello, and
• reggae.)

 

  1 hour ago, dcathro said:

 

My widebanders only do 50hz to about 6Khz, and my tweeters are -6db at 20Khz.

 

Expand  

 

So you:

a.  have a XO between your so-called "widebanders" and your tweeters

b.  don't have much HF delivery if you're already 6dB down at 20kHz, and

c.  you miss out on bass?

 

 

  On 20/10/2020 at 9:33 AM, springcreek said:

 

They do 15k to 40hz. That is where the music lives. I have no need for more. I have heard many, many speakers that do 20hz to 20k and they all bore my to tears.

 

Expand  

 

 

Sure, 40Hz to 15kHz is a good definition of where most of the musical frequencies reside ... but not to be able to hear a 16Hz (32' organ pipe) note means your enjoyment of Bach organ music will be severely degraded.    To say nothing of Yello!

 

 

  On 20/10/2020 at 9:33 AM, springcreek said:

 

I wouldn’t swap these speakers for anything on the planet, no matter what technology or cost

 

Expand  

 

Maybe you need to widen your horizons and listen to some 'box-less' spkrs - like, say:

• Maggie 30.7s
• or Maggie 3.7s plus a pair of good subs ... integrated well!

 

Andy

 

[Andy Moore]

  On 20/10/2020 at 10:37 AM, andyr said:

 

Not as far as I am concerned!  

 

16Hz to >20kHz is my definition of 'full range' ... but if you don't listen to:

a. (pipe) organ music, and

b. classical piano or violin music

 

... you probably don't know WTF I am talking about.  

 

(I run Maggies - tweeters rated to 40kHz - with subs ... which greatly increase my enjoyment of:

• Bach organ music
• Yello, and
• reggae.)

 

 

So you:

a.  have a XO between your so-called "widebanders" and your tweeters

b.  don't have much HF delivery if you're already 6dB down at 20kHz, and

c.  you miss out on bass?

 

 

 

 

Sure, 40Hz to 15kHz is a good definition of where most of the musical frequencies reside ... but not to be able to hear a 16Hz (32' organ pipe) note means your enjoyment of Bach organ music will be severely degraded.    To say nothing of Yello!

 

 

 

Maybe you need to widen your horizons and listen to some 'box-less' spkrs - like, say:

• Maggie 30.7s
• or Maggie 3.7s plus a pair of good subs ... integrated well!

 

Andy

 

Expand  

Andy

 

I don’t listen to much organ music, but I do listen to pretty much everything else and the Rullit’s do it all. And they make music come alive. 
 

I’ve never heard a sub I could live with, slow witted and dull. And it would be very difficult finding anything that keeps up with the Rullit’s. Maybe some of Oleg’s 15 inch field coils or some high efficiency drivers slot loaded. 
 

I have heard many big speakers over the years from Maggie's to Wilson’s, Evolution Acoustics MM7, plenty of big horns, etc, etc. Many of those systems were very expensive topping the million dollar mark. Some were good, like Mike Lavigne’s room in Seattle. But mostly they just sounded like hifi to me. None came close to doing what the Rullit’s do.
 

Sure adding some cone area would give greater scale and I might consider Oleg’s super aero 12s one day, but the aero 8 just sound so alive, so real, so dynamic, so present and so high resolution that I don’t really want for much. Other than some system tuning, some additional room treatment and building a mercury vapour field coil psu I’m kind of done. Just buying records. Though I would like to buy a Dava field coil cartridge one day, not sure my Schroder could handle the cartridge mass 

 

To each their own, as long as it makes you happy 

Edited October 20, 2020 by springcreek