Building field coil speakers Rullit Aero

[Lautreamont]

Dear everyone


I'm looking for my next speaker to pair up with a single ended amplifier. It will probably by Yamamoto and Audio Antiquary (power and preamplifier respectively).

The more convenient approach is to upgrade my current Audio Note AN J/D speakers to the more efficient AN E/SPe HE (high efficient), however I'm not sure if that will be the right choice in the long run. I'd rather do a large upgrade now than upgrading slowly and in five years wanting something new.

I have read a lot about the magnificent field coil drivers by Oleg Rullit and I have also corresponded with him. There is an option of building your own speakers and a few friends of mine have encouraged me to do so, but I need to ally with the right people from the beginning since I have no experience or technical/practical knowledge when it comes to this.

A requirement is I want placement of the speaker near wall / corners and not like Open Baffle. Therefore I need recommendations on which cabinet to choose. Please can you recommend me some models or enclosures that would accompany my needs.

I have a 25 square meter listening room with almost 3 meters to the ceilings.

 

[dcathro]

The Rullits are fantastic drivers that can be an end game solution. When I first heard a pair of Aero 10s I was blown away.

From what I have seen, most people tend to put them in some form of open baffle, but I understand that Front loaded horn is another good solution.

@LanschePlasmaGuy has the Super Aero 9s and may be able to provide some advice.

What does Oleg suggest?

 

[Artnet]

I'm looking for my next speaker to pair up with a single ended amplifier. It will probably by Yamamoto and Audio Antiquary (power and preamplifier respectively).

I am running an Aero 8 in a Siemens /Telefunken OB (on loan until I have to build my own) and it can squawk with .75watt, talk with 9w and sing with 40 (EHT hybrid SET).
LPG will add more I hope on the beauteous Super Areo 9 and the benefits that the FL Horn will bring and allow the use of the lower watt SET more effectively.

What does Oleg suggest?

@Lautreamont Look forward to any developments

 

[Lautreamont]

The Rullits are fantastic drivers that can be an end game solution. When I first heard a pair of Aero 10s I was blown away.

From what I have seen, most people tend to put them in some form of open baffle, but I understand that Front loaded horn is another good solution.

@LanschePlasmaGuy has the Super Aero 9s and may be able to provide some advice.

What does Oleg suggest?

It is also what I hear.

I'm still waiting for Olegs answer but I will inform you when he replies.

I am running an Aero 8 in a Siemens /Telefunken OB (on loan until I have to build my own) and it can squawk with .75watt, talk with 9w and sing with 40 (EHT hybrid SET).
LPG will add more I hope on the beauteous Super Areo 9 and the benefits that the FL Horn will bring and allow the use of the lower watt SET more effectively.



@Lautreamont Look forward to any developments

That would be a clever and obvious solution for the use of the Rullit however as I stated I prefer speakers that are placed near the wall.

What is LPG? Can you please elaborate or send some reading material, articles, websites and alike, so that I will learn more about it?

I'm also thinking about the size of the driver. The Audio Note that I use are 8 inches. I heard that 15 inches will be way too much so perhaps 10 will be ideal.

 

[djsina2]

LPG = https://www.whatsbestforum.com/members/28507/

 

[Lautreamont]

LPG = https://www.whatsbestforum.com/members/28507/

Thank you.

Some will recommend:

Jean Hiraga "Onken" style cabinets
It seems though they are made especially for 15 inch woofers.

Front / rear loaded horns
This could be interesting to see examples of, preferably exquisite and genius vintage masterpieces.

Shindo Lafite / Latour
I know that these speakers are field coil driven, so perhaps one should try to look in that direction.

 

[LanschePlasmaGuy]

Hi Lautreamont.

I love Oleg's field coil Rullit's (have owned the Aero 8 (8 inch) and now the super aero 9 (much larger field coil structure and a 9 inch) and have a lot of experience hearing, playing and helping set up Super Aero 10's (10 inch). I've loved the Aero 8's. They can be so musical and enjoyable. The Super Aero 9's have tons more resolution, clarity, micro dynamics and really everything. They play at a far higher level but can be ruthless until you get them right. I admire the Super Aero 10's but if my experience is anything to go by they don't have the absolute magic or potential of the others mentioned (Different partnering gear and setups may change my view and prove me wrong).

A 25 metre squared room is I would think close to an ideal size for the Rullits. You still I believe would need to run them with some sort of augmented bass solution.

I think of them as a little bit like a wild thoroughbred racehorse. Glimpses of very rarely experienced audio magic with lots of audio hell and pain while they go through a crazy long run in process where they seem to change character every time you turn them on. Initially also they are very hard to drive. I've been told they become much easier to drive one they have run in (many hundreds of hours). I haven't experienced this personally because I in general prefer the sound of small triodes / amps. With these speakers you will hear every little change in your system and every little tweak you do. Change the toe in of the speakers by a couple of mm's and you will hear it. Get it right and they will dissolve your listening room and connect you with the musicians.

Have had a few Sansui amps in my time along with the 9500 and I think it sounds very musical but more because they have good transformers and have a reasonably powerful and rich sound (but you also lose a lot of detail information in that thickness). As your system get's better my experience has been the amp becomes more and more the limiting factor.

You mentioned Audio Antiquary, Yamamoto and Shindo. Love the Yamamoto 45 amp and a crazy bargain for the price. The AD1 Yamamoto which I almost bought and was powered by original era AD1's was wonderful but couldn't get rid of the hum and noise it had and the tubes are difficult to find in good nick so I regretfully gave it back. I still have one of the Shindo amps (300b) and I really enjoy it (with qualifications). The Audio Antiquary gear is just incredible (for my listening tastes) but is super revealing of every aspect of your audio setup and is a real microscope into your setup and the recording. When you get everything write though Misho's gear is just bonkers amazing (if your gear is sympathetic to what it needs and if you can get away with only a few watts (even though they may be the ballsiest 4 or so watts on the planet).

Anyway back to the Rullit's. When setup right, run in and depending not the size of the space and so many other factors they can be truly magical in a way that may just take your breath away. I've spent many hours with them just being lost in the beauty of music and not really thinking about the hifi chain at all. They like open baffle (and I suspect (and have been told) they absolutely sing in a large front loaded horn / waveguide which I will be experiencing in the near future once the enclosure are finished.

Some people also talk about Rullit's being full range. For me I just think that is not the case at all. They are wide range if your room is small enough to be loaded by the driver and they go surprisingly low but unless your space is tiny and you listen very close and to comparatively limited bandwidth smaller scale music you really need a supplementary bass solution.

Being so crazy revealing they really cry out for a simple small wattage tube or equivalent amp. The problem is they are not efficient enough to work with those amps at higher volumes. At low to mid volume they are magical with amps like the Audio Antiquary (assuming as per the above the rest of your system is sorted out and your using really good quality vinyl / digital front ends. This and other reasons is why I think playing with a front horn / waveguide for them is of benefit. You will gain around 6 db of gain along with a much better transformer for the air to grab onto and push into the room. For the frequencies that are not boosted by the front horn you can compensate at the high end by tweaking the field coils strength to balance the sound out and in the low end you can employ a bass solution below 150 odd HZ (depending on the size of the front horn). Having had similar type front horns before I would suggest a semi corner loaded approach where you have them pretty close to the side / back wall boundaries to increase efficiency again and also kind of cheat by extending the low end (you might be able to yield a crossover point closer to 70-80 hz if done correctly. Then assuming the front horn / waveguide doesn't colour the sound too much (or if it does at least be sympathetic with the music) then you should be able to play with all those beautiful small watt tubes.

You mentioned wanting speakers that could be close to a rear wall so that solution may fit your bill. Bear in mind the Rullits prefer to be open backed (open baffle or open backed horn). For open baffle you need some diffusion at the back wall if they are too close to it and really want a minimum of about 70 cm (ideally more) to start being able to breathe. If front horn loaded then the rear of the Rullit can be maybe around 20 cm or so (but again ideally a little further into the room but nothing crazy. (Playing with diffusion / absorption will be your friend and pay real dividends here.

Owning now lots of field coil based drivers once you get some familiarity with the better ones it's very hard to listen to anything else. They really are a new frontier for me. Much of the clarity of things like my direct drive tube driven electrostatics or Lansche plasma tweeters without the drawbacks.

You could also look at some Klangfilm style dipole solutions but you're talking a whole other metric of cost and commitment. But.....they can be truly amazing.

I don't want to pour shade on Audionote speakers. They are super musical and I love much of what the company does but I think the direction you are thinking about moving into is a really exciting one for you.

Hope some of this helps.

LPG

 

[Lautreamont]

Hi Lautreamont.

I love Oleg's field coil Rullit's (have owned the Aero 8 (8 inch) and now the super aero 9 (much larger field coil structure and a 9 inch) and have a lot of experience hearing, playing and helping set up Super Aero 10's (10 inch). I've loved the Aero 8's. They can be so musical and enjoyable. The Super Aero 9's have tons more resolution, clarity, micro dynamics and really everything. They play at a far higher level but can be ruthless until you get them right. I admire the Super Aero 10's but if my experience is anything to go by they don't have the absolute magic or potential of the others mentioned (Different partnering gear and setups may change my view and prove me wrong).

A 25 metre squared room is I would think close to an ideal size for the Rullits. You still I believe would need to run them with some sort of augmented bass solution.

I think of them as a little bit like a wild thoroughbred racehorse. Glimpses of very rarely experienced audio magic with lots of audio hell and pain while they go through a crazy long run in process where they seem to change character every time you turn them on. Initially also they are very hard to drive. I've been told they become much easier to drive one they have run in (many hundreds of hours). I haven't experienced this personally because I in general prefer the sound of small triodes / amps. With these speakers you will hear every little change in your system and every little tweak you do. Change the toe in of the speakers by a couple of mm's and you will hear it. Get it right and they will dissolve your listening room and connect you with the musicians.

Have had a few Sansui amps in my time along with the 9500 and I think it sounds very musical but more because they have good transformers and have a reasonably powerful and rich sound (but you also lose a lot of detail information in that thickness). As your system get's better my experience has been the amp becomes more and more the limiting factor.

You mentioned Audio Antiquary, Yamamoto and Shindo. Love the Yamamoto 45 amp and a crazy bargain for the price. The AD1 Yamamoto which I almost bought and was powered by original era AD1's was wonderful but couldn't get rid of the hum and noise it had and the tubes are difficult to find in good nick so I regretfully gave it back. I still have one of the Shindo amps (300b) and I really enjoy it (with qualifications). The Audio Antiquary gear is just incredible (for my listening tastes) but is super revealing of every aspect of your audio setup and is a real microscope into your setup and the recording. When you get everything write though Misho's gear is just bonkers amazing (if your gear is sympathetic to what it needs and if you can get away with only a few watts (even though they may be the ballsiest 4 or so watts on the planet).

Anyway back to the Rullit's. When setup right, run in and depending not the size of the space and so many other factors they can be truly magical in a way that may just take your breath away. I've spent many hours with them just being lost in the beauty of music and not really thinking about the hifi chain at all. They like open baffle (and I suspect (and have been told) they absolutely sing in a large front loaded horn / waveguide which I will be experiencing in the near future once the enclosure are finished.

Some people also talk about Rullit's being full range. For me I just think that is not the case at all. They are wide range if your room is small enough to be loaded by the driver and they go surprisingly low but unless your space is tiny and you listen very close and to comparatively limited bandwidth smaller scale music you really need a supplementary bass solution.

Being so crazy revealing they really cry out for a simple small wattage tube or equivalent amp. The problem is they are not efficient enough to work with those amps at higher volumes. At low to mid volume they are magical with amps like the Audio Antiquary (assuming as per the above the rest of your system is sorted out and your using really good quality vinyl / digital front ends. This and other reasons is why I think playing with a front horn / waveguide for them is of benefit. You will gain around 6 db of gain along with a much better transformer for the air to grab onto and push into the room. For the frequencies that are not boosted by the front horn you can compensate at the high end by tweaking the field coils strength to balance the sound out and in the low end you can employ a bass solution below 150 odd HZ (depending on the size of the front horn). Having had similar type front horns before I would suggest a semi corner loaded approach where you have them pretty close to the side / back wall boundaries to increase efficiency again and also kind of cheat by extending the low end (you might be able to yield a crossover point closer to 70-80 hz if done correctly. Then assuming the front horn / waveguide doesn't colour the sound too much (or if it does at least be sympathetic with the music) then you should be able to play with all those beautiful small watt tubes.

You mentioned wanting speakers that could be close to a rear wall so that solution may fit your bill. Bear in mind the Rullits prefer to be open backed (open baffle or open backed horn). For open baffle you need some diffusion at the back wall if they are too close to it and really want a minimum of about 70 cm (ideally more) to start being able to breathe. If front horn loaded then the rear of the Rullit can be maybe around 20 cm or so (but again ideally a little further into the room but nothing crazy. (Playing with diffusion / absorption will be your friend and pay real dividends here.

Owning now lots of field coil based drivers once you get some familiarity with the better ones it's very hard to listen to anything else. They really are a new frontier for me. Much of the clarity of things like my direct drive tube driven electrostatics or Lansche plasma tweeters without the drawbacks.

You could also look at some Klangfilm style dipole solutions but you're talking a whole other metric of cost and commitment. But.....they can be truly amazing.

I don't want to pour shade on Audionote speakers. They are super musical and I love much of what the company does but I think the direction you are thinking about moving into is a really exciting one for you.

Hope some of this helps.

LPG

Dear LPG

Thank you very much for your detailed response. It is truly the most helpful reply I could have hoped for, and I deeply appreciate the time you took to share your experiences.

I do have a few follow-up questions based on your post, and I would be most grateful if you might have the time to share further thoughts or offer your opinions.

It seems that the super aero 9 significantly outperforms Aero 8 in resolution, clarity, and dynamics but is more demanding to set up.

1. What should I consider when setting it up? Is it in terms of amplifier pairing, choice of enclosure or something else?

Right now I don't see open baffle as a solution in relation to my interior and I would rather strive for a solution where I have speakers placed near the walls. 20 centimeters as the front loaded horns require is quite alright.

2. Do you have any advice of the enclosure design? I have allied with a person that knows how to operate a cnc milling machine and could be helpful in cutting out a design in baltic plywood. Furthermore I have a friend who knows how to veneer wood.

I'm happy to hear that the front loaded horn designs promote efficiency since I would most likely go for the Yamamoto Sound Craft VT-52 amplifier that produces 3W per channel. I want to prioritize the speaker so if I needed more power I could choose a 300B or even 211-based amplifier. It's just that I have become madly intrigued by the 45 tube.
In my room I seldom listen to music at loud levels. It does occur, however, that I sit and listen critically to a symphony or an album, but usually I read while I listen to music. I would like to maintain perspective, depth and character in the music whilst listening at lower volumes. Sometimes I feel that It's a great way to test the quality of a system - by simply lowering the volume. I guess the horn loading from the front loaded concepts will bring me the efficiency.

I'm trying to make a list of components I need. I read an article about adding a super tweeter but I'm not sure if that is necessary and also, which one that would pair with the Rullit. I don't want to overcomplicate things.
You recommend me to look at a bass solution. I listen to jazz and classical and I prefer to listen (and feel!) the nuances of the double bass, the touch, the tone and the detail. I don't listen to electronic music that requires a deep bass.

3. Can you please elaborate on the bass system? What could that be?

System matching is probably one of my weaknesses. I still consider myself as a beginner in the world of high fidelity audio. Please feel free to comment my choices. Keep in mind that the Sansui is one that I have inherited from my father but it will soon be replaced. Don't worry I will keep it and use it for something else.

Yamamoto Sound Craft "VT-52"
Audio Antiquary preamplifier + (RIAA)
Abbas Audio RIAA

Once again thank you very much.

 

[Don Reid]

Does anyone know if the Aero 8 is configured so that it would fit horns such as BD Design Oris 150 horns designed for AER or Lowther 8" drivers?

 

[LanschePlasmaGuy]

Does anyone know if the Aero 8 is configured so that it would fit horns such as BD Design Oris 150 horns designed for AER or Lowther 8" drivers?

Hi Don. The field coil Aero 8 Rullit driver I think would work pretty well in the Oris 150. I had a 150 for many years in lots of different configurations and they gave me a great deal of joy and musical pleasure. In the final setup I used them in I had two pairs of Klipschorns (the bass enclosures only and upgraded with Altec 421 bass drivers) serving bass duties crossed at between 130-150 hz depending on slope and active crossover. It was a tall speaker and was a nice change from a range of other speakers I was using which included Tannoy GRF Autograph corner horns with a range of early to late Tannoy 15's and some custom drivers.

Anyway Tuyen in Australia is using a Martin Seddon Azura horn (similar to Bert's Oris 150) but he is using the smaller model. The field coil is useful for adjusting the balance to taste so it isn't too dark at the area where the horn boosts the lower end / mid where the Oris 150 gives most boost. You might ideally want to look at one of the super aero drivers in the Oris though for best results (I think from memory the Oris boosts the lower end mid around 6 db or thereabouts so the greater snap and control of the cone along with the greater adjustability of the Super Aero would be desirable.

LPG

 

[LanschePlasmaGuy]

Dear LPG

Thank you very much for your detailed response. It is truly the most helpful reply I could have hoped for, and I deeply appreciate the time you took to share your experiences.

I do have a few follow-up questions based on your post, and I would be most grateful if you might have the time to share further thoughts or offer your opinions.

It seems that the super aero 9 significantly outperforms Aero 8 in resolution, clarity, and dynamics but is more demanding to set up.

1. What should I consider when setting it up? Is it in terms of amplifier pairing, choice of enclosure or something else?

Right now I don't see open baffle as a solution in relation to my interior and I would rather strive for a solution where I have speakers placed near the walls. 20 centimeters as the front loaded horns require is quite alright.

2. Do you have any advice of the enclosure design? I have allied with a person that knows how to operate a cnc milling machine and could be helpful in cutting out a design in baltic plywood. Furthermore I have a friend who knows how to veneer wood.

I'm happy to hear that the front loaded horn designs promote efficiency since I would most likely go for the Yamamoto Sound Craft VT-52 amplifier that produces 3W per channel. I want to prioritize the speaker so if I needed more power I could choose a 300B or even 211-based amplifier. It's just that I have become madly intrigued by the 45 tube.
In my room I seldom listen to music at loud levels. It does occur, however, that I sit and listen critically to a symphony or an album, but usually I read while I listen to music. I would like to maintain perspective, depth and character in the music whilst listening at lower volumes. Sometimes I feel that It's a great way to test the quality of a system - by simply lowering the volume. I guess the horn loading from the front loaded concepts will bring me the efficiency.

I'm trying to make a list of components I need. I read an article about adding a super tweeter but I'm not sure if that is necessary and also, which one that would pair with the Rullit. I don't want to overcomplicate things.
You recommend me to look at a bass solution. I listen to jazz and classical and I prefer to listen (and feel!) the nuances of the double bass, the touch, the tone and the detail. I don't listen to electronic music that requires a deep bass.

3. Can you please elaborate on the bass system? What could that be?

System matching is probably one of my weaknesses. I still consider myself as a beginner in the world of high fidelity audio. Please feel free to comment my choices. Keep in mind that the Sansui is one that I have inherited from my father but it will soon be replaced. Don't worry I will keep it and use it for something else.

Yamamoto Sound Craft "VT-52"
Audio Antiquary preamplifier + (RIAA)
Abbas Audio RIAA

Once again thank you very much.

Hi Lautreamont.

That's a lot to answer because to give a proper answer to each of those questions would require a pretty long in depth response.

To provide basic answers I would say that I'm not sure if one of the Rullit's is going to work for you for a few reasons.

One, the Rullit driver looks like it is super efficient but it really isn't. I'm not convinced that 3 watts from a VT52 is going to do it. With the front horn solution using one of those drivers you may have no problems with even 1 watt, I just haven't received the front horns yet so don't know. I know that Semrad audio get away with a 4 watt give or take type 50 amp so it may well be a great match (I hope so). Rich from Treehaus audio builds a beautiful 300b amp that I think is about 8 watts or so and that drives his speakers so you could look at something like that. I think he uses interstages which would definitely help drive and control. But............

Another reason the Rullit solution may not work for you is I've been told by a few people that the Rullit driver in a box is not a great match. I don't think having that super light paper cone in an enclosure sounds like a great idea to me but I may be wrong.

So if a box is out using one of his drivers that leaves you with an open baffle or a front horn / waveguide.

You mentioned not wanting the speakers too far into the room and wanting them near(ish) to the back wall. the open baffle solution really wants more room than you seem happy to provide for it to sound its best.

The front horn then sounds like a good solution but is it for you? The Rullit plans call for a front horn that is almost 1.2 metres wide and without looking at my plans something like 60 cm deep (not allowing for the depth of the open backed driver and the room it needs to breathe because it is open backed so you need another probably 30 cm or so making each speaker around 1.2 metres wide, 1.2 metres high (and that would be on the floor and they need to be raised up at least about 30 cm so your looking around 1.5 metres high give or take) and then 90 cm deep. You could organise someone to calculate and build a cut down version (mine will be slightly smaller but still enormous) but you have to be careful because very quickly loose the low end augmentation you are after.

So you have a few competing issues.

The other reason they may not be suitable is I would not recommend them to anyone who doesn't have deep experience with putting systems together, tuning etc. There are so many variables you can very easily go sideways and end up hating the sound of what you have put together.

That leaves you with the potential solutions of looking at buying a ready built speaker using those drivers (Semrad for the front horn) and Treehaus Audio for the open baffle (which you mentioned you may not be willing to give space behind the driver / baffle to). At least with those two options you get two amazing speaker systems but then it comes down to if you are ok to spend the money they cost buying a "turn key" solution.

In saying that I think Semrad (and in particular Treehaus Audio) speakers are ridiculously inexpensive compared to the cost of the drivers and work that goes into them.

Rich from Treehaus is a super nice guy. Maybe have a chat with him about options and if something he does will work for you?

Lastly bass. The Rullit driver is way better than most full range drivers in this regard but they need a bass solution to augment them period (in my very opinionated opinion (and someone who has been playing with horns and full range drivers and single ended amp style solutions in a pretty deep way for more than 35 years). Cello, double bass etc. needs a helper woofer. I'm not talking about a subwoofer though that would be nice if the helper woofer can go down that low. But you really need an augmentation driver to give the right weight and balance down below (unless in a tiny room or really using the gain of the boundaries to give you enough of that to satisfy you (and compromising other aspects of having them positioned this way). If your listening to classical pieces larger than a basic quartet or so this is non negotiable in my opinion.

LPG

 

[LanschePlasmaGuy]

Lautreamont,

Songer Audio might be an option for you. They are supposed to sound wonderful (I haven't heard them), are full range and field coil with beautiful looking (and I'm sure sounding) hand made drivers, are supposed to have great bass and be easy to drive (and I'm pretty sure he has a closed box model). They are also supposed to be I think very efficient.

LPG

 

[dcathro]

Lautreamont,

Songer Audio might be an option for you. They are supposed to sound wonderful (I haven't heard them), are full range and field coil with beautiful looking (and I'm sure sounding) hand made drivers, are supposed to have great bass and be easy to drive (and I'm pretty sure he has a closed box model). They are also supposed to be I think very efficient.

LPG

That would also be my suggestion, @songeraudio produce great looking speakers that have been getting great reviews. Worth investigating.

 

[Lautreamont]

Hi Lautreamont.

That's a lot to answer because to give a proper answer to each of those questions would require a pretty long in depth response.

To provide basic answers I would say that I'm not sure if one of the Rullit's is going to work for you for a few reasons.

One, the Rullit driver looks like it is super efficient but it really isn't. I'm not convinced that 3 watts from a VT52 is going to do it. With the front horn solution using one of those drivers you may have no problems with even 1 watt, I just haven't received the front horns yet so don't know. I know that Semrad audio get away with a 4 watt give or take type 50 amp so it may well be a great match (I hope so). Rich from Treehaus audio builds a beautiful 300b amp that I think is about 8 watts or so and that drives his speakers so you could look at something like that. I think he uses interstages which would definitely help drive and control. But............

Another reason the Rullit solution may not work for you is I've been told by a few people that the Rullit driver in a box is not a great match. I don't think having that super light paper cone in an enclosure sounds like a great idea to me but I may be wrong.

So if a box is out using one of his drivers that leaves you with an open baffle or a front horn / waveguide.

You mentioned not wanting the speakers too far into the room and wanting them near(ish) to the back wall. the open baffle solution really wants more room than you seem happy to provide for it to sound its best.

The front horn then sounds like a good solution but is it for you? The Rullit plans call for a front horn that is almost 1.2 metres wide and without looking at my plans something like 60 cm deep (not allowing for the depth of the open backed driver and the room it needs to breathe because it is open backed so you need another probably 30 cm or so making each speaker around 1.2 metres wide, 1.2 metres high (and that would be on the floor and they need to be raised up at least about 30 cm so your looking around 1.5 metres high give or take) and then 90 cm deep. You could organise someone to calculate and build a cut down version (mine will be slightly smaller but still enormous) but you have to be careful because very quickly loose the low end augmentation you are after.

So you have a few competing issues.

The other reason they may not be suitable is I would not recommend them to anyone who doesn't have deep experience with putting systems together, tuning etc. There are so many variables you can very easily go sideways and end up hating the sound of what you have put together.

That leaves you with the potential solutions of looking at buying a ready built speaker using those drivers (Semrad for the front horn) and Treehaus Audio for the open baffle (which you mentioned you may not be willing to give space behind the driver / baffle to). At least with those two options you get two amazing speaker systems but then it comes down to if you are ok to spend the money they cost buying a "turn key" solution.

In saying that I think Semrad (and in particular Treehaus Audio) speakers are ridiculously inexpensive compared to the cost of the drivers and work that goes into them.

Rich from Treehaus is a super nice guy. Maybe have a chat with him about options and if something he does will work for you?

Lastly bass. The Rullit driver is way better than most full range drivers in this regard but they need a bass solution to augment them period (in my very opinionated opinion (and someone who has been playing with horns and full range drivers and single ended amp style solutions in a pretty deep way for more than 35 years). Cello, double bass etc. needs a helper woofer. I'm not talking about a subwoofer though that would be nice if the helper woofer can go down that low. But you really need an augmentation driver to give the right weight and balance down below (unless in a tiny room or really using the gain of the boundaries to give you enough of that to satisfy you (and compromising other aspects of having them positioned this way). If your listening to classical pieces larger than a basic quartet or so this is non negotiable in my opinion.

LPG

Dear LPG

I must admit that I was reading your initial reply with great joy and satisfaction. It gave me hope that I might was getting into a "life-changing" quest in terms of finding satisfying speakers that could give me years of transcending experiences.

Concluding there are two design options that I proceed with:
1. Front Loaded Horn
Cons: They are large and need space.

2. Open Baffle System
Cons: They are medium sized but needs space behind them.

One of my livings rooms in my apartment (that also functions as my listening room) is 25 square meters with 2,7 meters to the ceilings.

Concluding there are a few considerations before proceeding:
1. Beginners naivety
I have no technical or practical experience putting together a system which means it could be rather risky to proceed.

2. Lack of understanding of field coil
I do not have the necessary understanding of the field coil driver so it would be unwise to strive for an idea without knowing the basic concepts.

 

[Lautreamont]

A friend recommends Open Baffle but with the necessary adjustment of absorbing/damping behind the speaker. Please see the link: https://jelabs.blogspot.com/2024/05/silbatone-box-adventures.html


Options:
Furthermore. I am corresponding with Azurahorn. Could a Le Cleac'h horn be of any support of my mission or would that too be an enormous construction?

Options:
A friend recommends a Silbatone 755A box design.

I understand that there are people who have audio system that is larger than church organs and that is fine by me. It's not that I dislike large speakers, but some of them can be too large. I too enjoy that speakers are aesthetic and can blend in the interior as a piece of designer furniture.

 

[Lautreamont]

One more question.

I've been told that efficiency is a bit different when it comes to field coil drivers and in comparison with regular speaker units.
Since the field coils need a power supply, the concept of efficiency changes a bit.
Can someone elaborate or verify?

 

[songeraudio]

One more question.

I've been told that efficiency is a bit different when it comes to field coil drivers and in comparison with regular speaker units.
Since the field coils need a power supply, the concept of efficiency changes a bit.
Can someone elaborate or verify?

Hi Lautreamont,

I just read through this thread and your other seeking a high efficiency full-range speaker, and just wanted to share a few thoughts - I hope they may be helpful.

There are two key advantages to field coils over permanent magnets. The first is that they are adjustable, as I think you may be referring to in your most recent post. If you have a variable power supply, you can simply adjust the voltage and that in turn changes the efficiency and other performance characteristics of the speaker. It's just a nice way to fine-tune the sound of the speaker to your taste, assuming the efficiency remains high enough for your amplification.

More importantly however, field coils have much greater permeability than permanent magnets and are therefore far more accurate. When permeability is low (as it is with neodymium, for example), regardless of strength the magnetic field behaves like a trampoline. As the magnet interacts with an AC signal and oscillates the cones, it overshoots the points in space it should for accurate sound reproduction. Why do many audiophiles prefer alnico drivers over neodymium? I believe it's because alnico has significantly higher material permeability. Field coils on the other hand have a permeability (or, self-damping) limited only by the saturation of the metal. That figure is hundreds and often thousands of times higher than any permanent magnet drivers are capable of, and results in an uncannily lifelike reproduction of music.

I agree with LPG's comments regarding open baffles. While distance from the wall minimizes unwanted room effects, it's also key to bass performance. If the distance from the front wall is a quarter-wavelength of the frequency being considered, the reflected back wave will arrive at the speaker with the correct phase to reinforce the original front wave, effectively doubling the bass output at that frequency. As a rule of thumb, a spacing of 1/3 of the length of the room will be ideal. With that, the effective frequency response of the Rullit drivers, and your preferences in mind, it may be wise to opt for something in an enclosure.

Rich Pinto and Radu Tarta are brilliant, wonderful people. Considering your high-efficiency low-wattage goals, you can hardly hope for better than a Treehaus 300B option. You can take my word on that - we ourselves collaborated with Rich and Radu to create the A3, our integrated amplifier that debuted in Chicago last month.

We don't currently have distribution in Europe, which may be too much to consider - but, if it isn't I think the S1 (or, the S1x) would be a great option for you. In a space the size of your listening room you can expect full, articulate bass response to 30Hz or better. The S1 is likewise a point source, phase coherent throughout the audible range and free of multiway interaction and time-alignment issues. And, we routinely work with wood species and finishes for cabinetry that matches our clients furniture and tastes. If you'd like to read a little about the speaker, you can find a link to a full review from Enjoy the Music here, along with awards and further impressions from the press:

press | Songer Audio

Songer Audio is a maker of finely crafted field coil loudspeakers and amplifiers, 100% hand-made in the USA.

songeraudio.com

I hope some of this is helpful, Lautreamont, and thank you @LanschePlasmaGuy and @dcathro for the kind recommendation! Best wishes and good luck as you make decisions about your system.

Best,

Ken

 

[LanschePlasmaGuy]

Lautreamont, just a Little thing. I read through some of your other threads (and this one). I spent over an hour and a half writing to you my digested thoughts and experiences to try and give you some help. Other's have done the same. I've noticed you haven't "liked" anyone's posts who have replied to you and it's been bothering me. It might be nice to like peoples posts when you ask questions and fellow members take the time to write huge replies to you giving you their experience.

Anyway good luck in your journey. You will figure it out. Your lucky that Ken Songer, Rich from Treehaus and others are such awesome people, freely giving their experience to help others and making beautiful music making machines that you could buy as a turnkey solution.

LPG

 

[Lautreamont]

Dear everyone.

First and foremost I apologies for not liking your posts. I did not know it was valuable to you, but of course it seems like a polite way to appreciate that you take your time to answer my (many) questions. It's not that I actively thought of "not liking", rather I simply just overlooked it.

Hi Lautreamont,

I just read through this thread and your other seeking a high efficiency full-range speaker, and just wanted to share a few thoughts - I hope they may be helpful.

There are two key advantages to field coils over permanent magnets. The first is that they are adjustable, as I think you may be referring to in your most recent post. If you have a variable power supply, you can simply adjust the voltage and that in turn changes the efficiency and other performance characteristics of the speaker. It's just a nice way to fine-tune the sound of the speaker to your taste, assuming the efficiency remains high enough for your amplification.

More importantly however, field coils have much greater permeability than permanent magnets and are therefore far more accurate. When permeability is low (as it is with neodymium, for example), regardless of strength the magnetic field behaves like a trampoline. As the magnet interacts with an AC signal and oscillates the cones, it overshoots the points in space it should for accurate sound reproduction. Why do many audiophiles prefer alnico drivers over neodymium? I believe it's because alnico has significantly higher material permeability. Field coils on the other hand have a permeability (or, self-damping) limited only by the saturation of the metal. That figure is hundreds and often thousands of times higher than any permanent magnet drivers are capable of, and results in an uncannily lifelike reproduction of music.

I agree with LPG's comments regarding open baffles. While distance from the wall minimizes unwanted room effects, it's also key to bass performance. If the distance from the front wall is a quarter-wavelength of the frequency being considered, the reflected back wave will arrive at the speaker with the correct phase to reinforce the original front wave, effectively doubling the bass output at that frequency. As a rule of thumb, a spacing of 1/3 of the length of the room will be ideal. With that, the effective frequency response of the Rullit drivers, and your preferences in mind, it may be wise to opt for something in an enclosure.

Rich Pinto and Radu Tarta are brilliant, wonderful people. Considering your high-efficiency low-wattage goals, you can hardly hope for better than a Treehaus 300B option. You can take my word on that - we ourselves collaborated with Rich and Radu to create the A3, our integrated amplifier that debuted in Chicago last month.

We don't currently have distribution in Europe, which may be too much to consider - but, if it isn't I think the S1 (or, the S1x) would be a great option for you. In a space the size of your listening room you can expect full, articulate bass response to 30Hz or better. The S1 is likewise a point source, phase coherent throughout the audible range and free of multiway interaction and time-alignment issues. And, we routinely work with wood species and finishes for cabinetry that matches our clients furniture and tastes. If you'd like to read a little about the speaker, you can find a link to a full review from Enjoy the Music here, along with awards and further impressions from the press:

press | Songer Audio

Songer Audio is a maker of finely crafted field coil loudspeakers and amplifiers, 100% hand-made in the USA.

songeraudio.com

I hope some of this is helpful, Lautreamont, and thank you @LanschePlasmaGuy and @dcathro for the kind recommendation! Best wishes and good luck as you make decisions about your system.

Best,

Ken

Hello Ken.

Thank you very much for the thorough introduction to the field coil. I have taken your post and saved it on my computer for later use. A follow up question: If the field coil is more flexible in terms of efficiency, wouldn't that open up for a lot more choices in terms of enclosure?

Thank you for both the recommendation of Treehaus and your own enterprise. I have actually been looking at your gorgeous production and have been quite amazed. Feel free to contact me again if you were to find a european distributor. I would like to learn more about your products.

There are no doubt that Treehaus makes astonishing products and I will consider to investigate their production further.

For everyone
Thank you very much once again. I could not have wished for better replies than those I have received. I tried to explain my gratitude many times and I will also remember to "like" posts in the future.

 

[songeraudio]

Dear everyone.

First and foremost I apologies for not liking your posts. I did not know it was valuable to you, but of course it seems like a polite way to appreciate that you take your time to answer my (many) questions. It's not that I actively thought of "not liking", rather I simply just overlooked it.


Hello Ken.

Thank you very much for the thorough introduction to the field coil. I have taken your post and saved it on my computer for later use. A follow up question: If the field coil is more flexible in terms of efficiency, wouldn't that open up for a lot more choices in terms of enclosure?

Thank you for both the recommendation of Treehaus and your own enterprise. I have actually been looking at your gorgeous production and have been quite amazed. Feel free to contact me again if you were to find a european distributor. I would like to learn more about your products.

There are no doubt that Treehaus makes astonishing products and I will consider to investigate their production further.

For everyone
Thank you very much once again. I could not have wished for better replies than those I have received. I tried to explain my gratitude many times and I will also remember to "like" posts in the future.

My pleasure, Lautreamont!

Yes, you're correct. The Qts parameter of the driver changes value with voltage, which may allow for use in different applications. Low voltage results in high Qts, which can work for a sealed enclosure, or open baffle design. Conversely, high voltage lowers Qts, which may work well for a ported enclosure. Of course, there are always trade-offs. Lowering voltage for a high Qts comes at the cost of sensitivity.