Part 4: The Whole Elephant

songeraudio

Manufacturer Handmade Field Coil Speakers
Aug 3, 2022
80
236
40
54
Portland, OR
www.songeraudio.com
The excitement around the driver grew. It felt like everyone who experienced them was immediately captivated, and soon after the first pairs were finished I committed to do a speaking engagement, to share my process and the work.

It'd be nice to say that the next thing that happened in this long chronicle was that I brought the same patience, discipline and confidence that went into the driver into the cabinetry as well, and greatness was the inevitable outcome. But what really happened was quite different.

A few of the design concerns that needed to be addressed in the cabinetry were these:
  1. Heat could pose a problem if the owner, accidentally or otherwise, left the power supplies running indefinitely
  2. Each driver weighed 30lbs, and needed to be very securely supported
  3. In securing the driver, the means could not afford to deform the frame by even fractions of a millimeter, thereby misaligning the voice coil.
  4. The driver needed to be accessible for iteration in development and in the event that it ever needed service. Knowing that the motor would likely be bolted to an internal support of some kind, it could not be simply taken in and out of a conventional cabinet by way of a handful of screws in the flange.
  5. The design must not be so difficult, time-consuming, or costly to execute as to be impractical
There were many more. So much can go wrong in the design, engineering and delivery of a complete loudspeaker. With a field coil loudspeaker there are especially many, and even in the best of cases any one of them may result in a round-trip flight to the customers home, with a pair of replacement drivers in hand. But what if the problem arises from a fundamental issue with the engineering and construction of the cabinetry itself? Too unpleasant to dwell upon. And what about shipping? What would happen when this loudspeaker of mine was subjected to transport in the back of a tractor trailer, careening and jolting down the highway for thousands of miles? And, a minor detail, how do I even begin to price something like this? Do I need to consult with a lawyer? The sheer weight of what I was attempting was finally dawning upon me.

Whatever you do, I thought, don't look at the whole elephant. Just keep your head down, and continue to eat. One little forkful at a time.

A ported design was to be my first, and any outcome that required a subwoofer would be judged a failure. This was full-range, or bust. Right from the outset however, modeling the cabinet made clear that regardless of architecture, bass performance was going to be a challenge. In a ported enclosure that's of course dependent upon box volume and tuning frequency. However, the Thiele Small parameters of the driver are also critically important. A few key values are Fs (the resonant frequency of the driver in free-air), Qts (derived from the electrical and mechanical quality of the driver), and Vas (the volume of air in a cubic meter with equivalent compliance as the driver suspension).

Unsurprisingly, modeling showed that large volumes tuned properly played deep. However, beyond a certain scale enclosures became edifices, too unappealing and imposing. I decided that 120 liters would be my limit, and anything further would need to be achieved by way of "apparent" internal volume.

Low Qts predicted a smooth roll-off, but well above my target in the mid to low 30's. High Qts played significantly deeper, but left a +3dB boost in output just before roll-off, for which impractically lower tuning seemed the only remedy. The otherwise wonderful ultra-soft driver suspension came with ultra-high Vas, which unfortunately predicted a more pronounced hump, and an earlier, steeper roll-off. Every choice it seemed, was a maddening trade-off. The trick was clearly in performing a balancing act between them all.

I wanted to showcase the beauty of the field coil, even if it was confined to a cabinet. A thick channel of glass down the middle looked striking, to my eye. Minus a planned-for black granite base, here was that design:

cabinet_front.png
cabinet_ortho.png

I had the glass waterjet-cut by a local shop, but soon after I'd finished the CAD work I shelved this idea. There were so many unknowns around the basic construction and assembly of it. And, it was a clear violation of my guidelines: it was much too expensive and difficult for a first pass. I still have the CAD files, the toolpaths, and the glass for it in my shop, though. Maybe someday.

The next design was meant to correct for the overwhelming complexity and expense of the first design, and went much too far in that regard:

cabinet_planar_quarter.png
cabinet_planar_three_quarter.png

It didn't even look good... but unfortunately, I was fixated with some of it's features. The wires could be easily concealed with channels and conduits. The motor protruding from the back was all at once good for motor cooling, support, and easy driver removal from the front when necessary. The wood was a beautiful, dense Santos Mahogany, and the sheet glass was much more affordable than the bespoke shapes of the previous design. Drunk on the driver's success, I pushed ahead:

fronts_oiled.jpg
glass_cabinets.png

As previously mentioned, wood likes to flex and contract with changes in temperature and humidity. When it is bound by the strongest, stiffest glue one can possibly find to a completely inflexible stratum, the outcome is quite enlightening.

The glass cabinets were about a week from completion.

As I wandered around the house with my first cup of coffee one morning, I turned to hear a very strange screeching noise coming from them. Over the course of the past week or so, the relentlessly flexing wood had finally worn its opponent down. And that terrible sound I was hearing? It was the glass, inevitably surrendering. It happened to both cabinets, on all sides more or less at once, and literally all within an hour's time. This was the picture I texted my wife after a minute or two of helplessly watching the spectacle as it began:

glass_cracking.png

Sad though it was at the time, this setback was a necessary turning point.

I had allowed myself to doubt, and in doing so lost sight of my vision; of why I was pursuing any of this at all. The passion and effort I'd invested so far was about trying to do something for a living that I love. It was not about fear of returning to something that I don't. It was about building the greatest possible loudspeaker that I could make. It was not about trying to build one that I thought I could sell, or that I worried may be imperfect in some all but unforeseeable way, down the road.

It also taught me to prototype iteratively in cheap materials, which of course I should have been doing all along. It brought real discipline back to my process. It woke me up to what an abomination the design actually was, and why. For starters it was insanely top-heavy and one day small, curious children would have been crushed under its falling weight. The motor cooling was superfluous, the port didn't have adequate interior room for it to function well, the sound was thin, the cabinet resonated excessively, and reflections bled through the cone. The parallel surfaces were a masterpiece in standing waves. It lacked baffle diffraction compensation, and there was no way to attractively address cabinet resonances, or to increase apparent volume. What's more, stripped of the flashy glass or simply viewed from any angle other than precisely side-on, well... it wasn't at all beautiful to look at.

Chapfallen, I removed the ruined glass, and finished out the cabinets with darkly stained mahogany:

prototype_cabinet.png

I took steps to raise the total Q at the expense of a little sensitivity, and the "giant iPhones" as they later came to be known measured in OmniMic software thusly:

prod_cabinet_6Ohm_resist_fr.png

Very little record of these speakers remains, which leads me to the pro tip for this chapter: exhaustively measure each of your failures, no matter how bad they are. The successes feel wonderful, but it's the failures that are priceless. I have learned more than I can reasonably document here from the analysis of my worst efforts, and next to nothing from my best.

The colossal iPhones were too clever by half. Nonetheless, I took them along with a carload of mid-fi gear and my best subwoofer to that local event the following month, and delivered a lengthy presentation to a packed house that evening about my work, to applause. After the talk, the crowd migrated to an adjacent room, where the speakers played for several hours.

And, much to my surprise, everyone who listened to them loved the way they sounded.

Everyone, that is, except me.
 
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Ken, having met you and your wife this past weekend at THE Show and hearing your S2 yesterday and the S1 the day before, I have said that your room was in my top 3. What I heard with your speakers and the Takatsuki 300B amp was nothing short of sensational. I was gobsmacked hearing you describe how you make and assemble every part in each of your speakers, Your field coil driver is simply beautiful and to hear that it takes you a month to produce one set of speakers tells me that there is a lot of love going into the speakers. Congratulations on such a wonderful product plus the explanations you have provided here gives the readers a chance to understand field coils and then to understand your philosophy in the design.
 
Wonderful post. Sharing the process you experienced as you progressed through the daunting challenge of creating a successful product in such a competitive world gives me a much greater appreciation of you, your product and even myself. I am fond of low powered SETs and the high efficiency field coil drivers that often partner with them. Can't wait to hear your speakers
 
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Ken, having met you and your wife this past weekend at THE Show and hearing your S2 yesterday and the S1 the day before, I have said that your room was in my top 3. What I heard with your speakers and the Takatsuki 300B amp was nothing short of sensational. I was gobsmacked hearing you describe how you make and assemble every part in each of your speakers, Your field coil driver is simply beautiful and to hear that it takes you a month to produce one set of speakers tells me that there is a lot of love going into the speakers. Congratulations on such a wonderful product plus the explanations you have provided here gives the readers a chance to understand field coils and then to understand your philosophy in the design.
Steve, thank you so much for sharing these thoughts. I can't overstate how highly I regard your critical evaluation, and to have left this powerful of an impression with my work is a highlight of the entire show for us. What's more, it was wonderful for Kimberly and I to have the pleasure of your company. I'll be looking forward to more listening and talking next year, when we return.

The attention and feedback we received from both press and attendees was tremendous. I can't wait to share these speakers again later this month, in Seattle. It should be something special.
 
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Wonderful post. Sharing the process you experienced as you progressed through the daunting challenge of creating a successful product in such a competitive world gives me a much greater appreciation of you, your product and even myself. I am fond of low powered SETs and the high efficiency field coil drivers that often partner with them. Can't wait to hear your speakers
Thank you, Billy, I'm so glad it speaks to you. I'm looking forward to writing the next chapter in the story, there's still so much to tell...
 
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Enjoyed this installment, and looking forward to the next one. Also glad to see that T.H.E. Show went well for you. Hope that the PAF will be the same.

Question regarding the S1s, have you sucessfully run them with any solid state amps? I believe I’ve seen a video with the Whammerdyne Circuit Salad? In his review, Bob Grossman said this:

“The S1 relies on high-quality tube amplification to perform at its peak, because as a single driver design it operates across its entire impedance curve in the audible range. That matters to amplification choice because the output stages of vacuum tube and solid-state amplifiers behave differently. In a solid-state amplifier, decreased power is output as the impedance of any given driver in a loudspeaker increases. That makes solid-state a great match for multi-way loudspeakers, in which each discrete driver needs to only operate within the ideal range of its output impedance. Further, solid-state amplifiers are highly self-damping and field coil drivers are also highly self-damping, the combination of which can lead to the driver becoming over-damped. In listening, this can often be experienced as a reduction in bass performance.”

The reason I ask is, although I am a SET guy (currently running 2A3s), I have recently been intrigued by the Class D GaNFET amps from AGD Designs, and am wondering how they might pair with the S1s?
 
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Enjoyed this installment, and looking forward to the next one. Also glad to see that T.H.E. Show went well for you. Hope that the PAF will be the same.

Question regarding the S1s, have you sucessfully run them with any solid state amps? I believe I’ve seen a video with the Whammerdyne Circuit Salad? In his review, Bob Grossman said this:

“The S1 relies on high-quality tube amplification to perform at its peak, because as a single driver design it operates across its entire impedance curve in the audible range. That matters to amplification choice because the output stages of vacuum tube and solid-state amplifiers behave differently. In a solid-state amplifier, decreased power is output as the impedance of any given driver in a loudspeaker increases. That makes solid-state a great match for multi-way loudspeakers, in which each discrete driver needs to only operate within the ideal range of its output impedance. Further, solid-state amplifiers are highly self-damping and field coil drivers are also highly self-damping, the combination of which can lead to the driver becoming over-damped. In listening, this can often be experienced as a reduction in bass performance.”

The reason I ask is, although I am a SET guy (currently running 2A3s), I have recently been intrigued by the Class D GaNFET amps from AGD Designs, and am wondering how they might pair with the S1s?
I'm so glad you're enjoying the story.

Yes, I have successfully run the S1 with solid state on many occasions. The listening experience has often been pleasing, but if you're a 2A3 fan I'm not sure a solid state pairing would have you over the moon. The Circuit Salad behaves like a solid state, and the match sounds great. But the Whammerdyne 2A3 monoblocks I run are easily better… amazing.

The Takatsuki TA-S01 is even more refined at commensurate expense - several people this past weekend said that only Gryphon had been better. I'm sure the new Western Electric 91E would also be remarkable. If you have your heart set on the AGD amps you mention, DM me and I'll reach out to them to learn a little more about their designs... cheers.
 
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I look forward to seeing you at PAF.
 
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hello, your S2 speaker (open baffle) looks really nice. are there already dealers in germany or europe where you can hear them. looks a bit like my diy from the design of the baffle. I can't compete with a professional product. I would be happy to receive an answer from you
 
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I could certainly be very happy with 2A3s for the rest of my audiophile days. The thing that intrigues me about the AGD amps is that they seem to have won over some pretty solid tube/SET lovers, like Rick Becker. Here is a link to a very interesting video comparing Feastrex full range field coil drivers, in custom cabinets, being driven by 300B monoblocks and the AGD Audion monoblocks:

 
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hello, your S2 speaker (open baffle) looks really nice. are there already dealers in germany or europe where you can hear them. looks a bit like my diy from the design of the baffle. I can't compete with a professional product. I would be happy to receive an answer from you
Thank you, Stephan! We are direct sales at the moment, but we may well have dealers in Germany at some point in the future. If you like, message me with your contact information and I'll be happy to add you to our subscribers. Should we expand in that direction, you'll be among the first to know.
 
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I could certainly be very happy with 2A3s for the rest of my audiophile days. The thing that intrigues me about the AGD amps is that they seem to have won over some pretty solid tube/SET lovers, like Rick Becker. Here is a link to a very interesting video comparing Feastrex full range field coil drivers, in custom cabinets, being driven by 300B monoblocks and the AGD Audion monoblocks:

Thanks much for this share, @tommylion - that was a compelling demo. The Feastrex shares so much DNA with our driver, I can't imagine that you wouldn't be able to expect similarly great performance. And, I'd really love to have a solid state option to recommend to clients - one that I know will deliver a truly top-tier listening experience. I'll take a moment to email AGD today... again, thanks for posting that.
 
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Friends, I am so proud to be able to share a couple of early write-ups from this past weekend, if you don't mind. I just couldn't be more honored, and it seems especially apropos in the context of this narrative and what an incredible journey it has been.


 
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I could certainly be very happy with 2A3s for the rest of my audiophile days. The thing that intrigues me about the AGD amps is that they seem to have won over some pretty solid tube/SET lovers, like Rick Becker. Here is a link to a very interesting video comparing Feastrex full range field coil drivers, in custom cabinets, being driven by 300B monoblocks and the AGD Audion monoblocks:

Hi @tommylion - I just got off the phone with Alberto in Italy, and he feels that the Tempo di GaN should be a great match for the S1.

Apparently, what I've read regarding the output stage of solid state amps versus tube is for the most part a myth; it's only true when the power supply of the amplifier is poorly designed. I can hardly do better than to be advised by Mr. Guerra, and I'm grateful to have had my understanding corrected. I only wish it had been sooner!

He's shipping me a Tempo di GaN to audition, and I'll share my impressions of the pairing here.
 
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Hi @tommylion - I just got off the phone with Alberto in Italy, and he feels that the Tempo di GaN should be a great match for the S1.

Apparently, what I've read regarding the output stage of solid state amps versus tube is for the most part a myth; it's only true when the power supply of the amplifier is poorly designed. I can hardly do better than to be advised by Mr. Guerra, and I'm grateful to have had my understanding corrected. I only wish it had been sooner!

He's shipping me an Tempo di GaN to audition, and I'll share my impressions of the pairing here.

Excellent, the Tempo is the model I'm interested in. Looking forward to your report!
 
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