Building field coil speakers Rullit Aero

[jlsemrad]

I've heard Rullit several times, but I liked them best on the horn.
At ebay you find such tractrix horns for 8"and 10" fieldcoils
View attachment 151532

Those don't look very much like tractrix horns. This is a tractrix:

 

[LanschePlasmaGuy]

Those don't look very much like tractrix horns. This is a tractrix:

I love the look of the Semrad horns (and the choice of gear and music in the Youtube clips i've seen). I've got quite a few of the French SAM records Jazz vinyl's and love them.

Did you try any other front horn profiles for the Rullit Super Aero's you are using and what was the benefit in sound of the tractrix profile you used?

How did the rollover you're using effect the sound (it must have been significant or you wouldn't have used it because the horn could be much smaller in dimensions with the rollover or you could have made the tractrix profile extend to the current dimensions, extending the low end allowing the helper woofer to crossover lower).

Did you have a preference for the Rullit Super Aero 8, 9 or 10 inch in your front loaded horn experiments? (In an open baffle hearing them at a range of different places and systems my strong preference is for the Super Aero 9).

I would love to hear your speakers in Australia!! Do you have a distributor here?

LPG

 

[jlsemrad]

I love the look of the Semrad horns (and the choice of gear and music in the Youtube clips i've seen). I've got quite a few of the French SAM records Jazz vinyl's and love them.

Did you try any other front horn profiles for the Rullit Super Aero's you are using and what was the benefit in sound of the tractrix profile you used?

How did the rollover you're using effect the sound (it must have been significant or you wouldn't have used it because the horn could be much smaller in dimensions with the rollover or you could have made the tractrix profile extend to the current dimensions, extending the low end allowing the helper woofer to crossover lower).

Did you have a preference for the Rullit Super Aero 8, 9 or 10 inch in your front loaded horn experiments? (In an open baffle hearing them at a range of different places and systems my strong preference is for the Super Aero 9).

I would love to hear your speakers in Australia!! Do you have a distributor here?

LPG

The picture that I attached was a horn that I built about fifteen years ago for a prototype 12" Rullit driver that belonged to a good friend of mine. I believe that it was the first Rullit driver to make it stateside. It has a tractrix (or possibly a kugelwellen, knowing Oleg) profile, drawings of which were provided by Rullit.

The horns that I currently build for the audiophile market have a Le Cléac'h flare which allows for full horn loading with a slightly shorter depth. I prefer the Super Aero 9 to all other Rullit drivers that I have listened to, and we use them exclusively for our horns. Although it is nominally a 9" driver, the horn throat is only 6" in diameter to get the optimum impedance for best efficiency. The crossover frequency is just slightly higher than the horn cut-off. We finally settled on a Linkwitz-Riley second order crossover.

You are correct in stating that the Rullits are finicky until they have a goodly number of hours on them. I've had a couple of embarrassing moments at shows when they decided that they needed to do something differently after we thought the room was well set up.

John

 

[Lautreamont]

The picture that I attached was a horn that I built about fifteen years ago for a prototype 12" Rullit driver that belonged to a good friend of mine. I believe that it was the first Rullit driver to make it stateside. It has a tractrix (or possibly a kugelwellen, knowing Oleg) profile, drawings of which were provided by Rullit.

The horns that I currently build for the commercial market have a Le Cléac'h flare which allows for full horn loading with a slightly shorter depth. I prefer the Super Aero 9 to all other Rullit drivers that I have listened to, and we use them exclusively for our horns. Although it is nominally a 9" driver, the horn throat is only 6" in diameter to get the optimum impedance for best efficiency. The crossover frequency is just slightly higher than the horn cut-off. We finally settled on a Linkwitz-Riley second order crossover.

You are correct in stating that the Rullits are finicky until they have a goodly number of hours on them. I've had a couple of embarrassing moments at shows when they decided that they needed to do something differently after we thought the room was well set up.

John

Thank you very much for the great insights.

Are there any plans on front loaded horn designs anywhere and what type of wood does people recommend?

I have heard a lot of people recommending the 9 inch driver from the 8 and 10 inch so I want to proceed with the 9 inch since it seems that it accommodate my musical preference as well. Is there some things that are “good to know” when dealing with 9 inch drivers?

I have heard a great deal about resonance cabinets or cabinets with an empty back (like open baffle but still closed designs) perhaps they could promote the best qualities of the driver whilst still not requiring so much space.

 

[Lautreamont]

Atelier Rullit Hornlautsprecher

www.cjm-audio.de

Perhaps one can guide me to a place where I can find DIY plans similar to the latter model?

 

[Lautreamont]

Hello again everyone.

I have made a few minor corrections to my listening room and I think I can (will) proceed with an open baffle design.

Does anyone have cabinet plans or help to how I get measurements, dimensions right?

 

[dcathro]

Hello again everyone.

I have made a few minor corrections to my listening room and I think I can (will) proceed with an open baffle design.

Does anyone have cabinet plans or help to how I get measurements, dimensions right?

If you download Tolvan Edge, you can simulate baffle size and driver position.

 

[Lautreamont]

"

If you download Tolvan Edge, you can simulate baffle size and driver position."

Thanks! I do not have the technical data of the Rullit though. They are a kept secret for the manufactor and I will respect Mr. Oleg disposition in this matter.

 

[dcathro]

"

If you download Tolvan Edge, you can simulate baffle size and driver position."

Thanks! I do not have the technical data of the Rullit though. They are a kept secret for the manufactor and I will respect Mr. Oleg disposition in this matter.

You don't need any data, the software assumes a perfect driver. You model the effect of baffle size, shape and position of the driver.

 

[Lautreamont]

Hello everyone.

Just a minor upgrade on the project.

I have contemplated for some time and corresponded with people who own (or have owned) Rullit drivers and experimented with cabinets. After all of this I'm left with an unresolved, ambivalent mind.

On one hand the mysterious magic of the handmade drivers are luring and on the other hand, this project is perhaps too risky for me at this moment. I'm not saying it's not a great driver, but perhaps I have been a bit spellbound with the idea. The field coil drivers are not cheap (7.000€ for the nine inch and that's without a dedicated power supply) and therefore it can be too risky to invest in such a project not knowing beforehand, that I will get great results. I like the concept of a full range system because it can promote realistic sound, however the compromise can be significant. It would be a shame to install the system and be left with "I lack bass" or "I'm not satisfied with the higher frequencies".

I will do some more investigation whilst still thinking about other options. I have another thread where I ask for speaker recommendations and I'm happy for all of your suggestions. Right now I'm thinking about the Tonapparate Model 55 (field coil) whilst also considering the recommendations you've given in this thread (Treehaus, Songer - I appreciate your dedication and thank you very much for reaching out to me personally in this thread).

 

[LanschePlasmaGuy]

Hello everyone.

Just a minor upgrade on the project.

I have contemplated for some time and corresponded with people who own (or have owned) Rullit drivers and experimented with cabinets. After all of this I'm left with an unresolved, ambivalent mind.

On one hand the mysterious magic of the handmade drivers are luring and on the other hand, this project is perhaps too risky for me at this moment. I'm not saying it's not a great driver, but perhaps I have been a bit spellbound with the idea. The field coil drivers are not cheap (7.000€ for the nine inch and that's without a dedicated power supply) and therefore it can be too risky to invest in such a project not knowing beforehand, that I will get great results. I like the concept of a full range system because it can promote realistic sound, however the compromise can be significant. It would be a shame to install the system and be left with "I lack bass" or "I'm not satisfied with the higher frequencies".

I will do some more investigation whilst still thinking about other options. I have another thread where I ask for speaker recommendations and I'm happy for all of your suggestions. Right now I'm thinking about the Tonapparate Model 55 (field coil) whilst also considering the recommendations you've given in this thread (Treehaus, Songer - I appreciate your dedication and thank you very much for reaching out to me personally in this thread).

Hi Lautreamont.

We have all been responding to your many questions. Good luck with your quest.

If you bought a Treehaus Audiolab speaker, Songer or Semrad you would have I think a game over, slam dunk, top of the mountain, everest quality speaker system. If you pay the money you will get the results.

If you feel you don't have the skills to build your own it sounds like its best to look at other options and ask other peoples opinions.

It's a pity you couldn't work this one out. You could have ended up with an amazing speaker music making system.

LPG

 

[Lautreamont]

Hi Lautreamont.

We have all been responding to your many questions. Good luck with your quest.

If you bought a Treehaus Audiolab speaker, Songer or Semrad you would have I think a game over, slam dunk, top of the mountain, everest quality speaker system. If you pay the money you will get the results.

If you feel you don't have the skills to build your own it sounds like its best to look at other options and ask other peoples opinions.

It's a pity you couldn't work this one out. You could have ended up with an amazing speaker music making system.

LPG

I have tried to show my gratitude in a lot of my posts and I'm still sorry that I didn't know that the "like" button meant so much to people.

Treehaus, Songer and Semrad is definitely on my list as well.

I have heard a lot about people being dissatisfied with the compromise of the full range system and it means I'm a bit nervous about proceeding. I don't find it obvious that I will get the results by paying the money rather it seems that DIY projects appear to take lots of time and effort - which makes sense - before getting the right sound.

If I had a complete plan then I could think about it.

 

[DaveC]

I have tried to show my gratitude in a lot of my posts and I'm still sorry that I didn't know that the "like" button meant so much to people.

Treehaus, Songer and Semrad is definitely on my list as well.

I have heard a lot about people being dissatisfied with the compromise of the full range system and it means I'm a bit nervous about proceeding. I don't find it obvious that I will get the results by paying the money rather it seems that DIY projects appear to take lots of time and effort - which makes sense - before getting the right sound.

If I had a complete plan then I could think about it.

It depends on what you want. Single driver can be as good as it gets for some music, but if you want to play symphonic music at realistic SPLs, you'll certainly be disappointed.

I'd consider looking around for a used or reasonably priced SD speaker to try out. You'd have to check out what's available locally. If you were in the USA I'd suggest just buying an Omega single driver speaker, and still would depending on shipping costs. You're buying direct without the high-end luxury markups.

Omega Speaker Systems

Omega Speaker Systems

omegaloudspeakers.com

If you do decide to DIY, I'd recommend NOT using OB, I've tried it and I dislike it. It's easier than any other design to implement, but that's its only pro and there's lots of cons.

 

[Paul Fairall]

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

I agree with much of what you said, not that I disagree with anything but don’t remember everything in a long post.
I have some experience with Rullit field coils and a long relationship with Oleg
I started with silver lab 8 which are very good especially at the price. I then bought aero 8 which are a step up but not by much, bearing in mind my very small room and the latest are super aero 10, all used in a large quarter wave box that was designed for Lii audio crystal 10 but is so versatile to accommodate all the Rullit field coils that I haven’t felt the need to change them. As my room is so small I don’t have the space for open baffle or the open back box that Oleg gave me the plans for. I did build the open backed boxes and gave them to my friend that designed the power supply so he could test the silver labs and power supply. I use Bakoon amplifiers and my first one is an 11r which is 10w and later bought the 13r which is 25w, my idea was that should I move to a larger room it would have more headroom.

 

[Paul Fairall]

I have tried to show my gratitude in a lot of my posts and I'm still sorry that I didn't know that the "like" button meant so much to people.

Treehaus, Songer and Semrad is definitely on my list as well.

I have heard a lot about people being dissatisfied with the compromise of the full range system and it means I'm a bit nervous about proceeding. I don't find it obvious that I will get the results by paying the money rather it seems that DIY projects appear to take lots of time and effort - which makes sense - before getting the right sound.

If I had a complete plan then I could think about it.

I haven’t read all of your posts on this so it may depend on the kind of music you listen to. I listen to many different genres, rock, country, jazz, classical electronic etc and I find the rullit drivers can reproduce all very well. If you listen to classical and attend live concerts then you may not be content with anything unless you have a huge budget.
I’m sure most people accept a compromise somewhere.
My compromise must be single driver speakers but it’s not much of a compromise for me,