Spherical Ambisonic Beamformers (IKO, 393 and the likes)

pacocreative · April 8, 2025, 9:57am

Hi there,

I recently developed an obsession about spherical ambisonic speakers.
These wonderful, elusive inventions that originated in 1980’s Ircam’s research, later developed by IEM Graz and made into production with Sonible’s IKO.

They are capable of projecting precise sound beams out of a single unit including directional low frequency beams. Fascinating! OK, it’s IRCAM forum, so y’all probably know that… Or maybe not.

I love several things about them…

the experience is very unlike listening to a speaker (or an ambisonic dome)
they are single and central, which is interesting in terms of logistics and the symbolics!
that they play with architecture - much more interesting artistically than perfect transparent systems out there. Which is exactly why I got interested in them in the first place, as I envisioned Echotronica - the festival for sound frontiers and spatial sound.
still not very much explored artistically

I spent the last couple of months learning everything I could, and came up with a small library to organize my learnings.

A few weeks back, I did a trip to Berlin and had pleasure of listening to the original IKO at Spaes in Funkhaus, thanks to Gerriet Sharma’s generosity. And I got even more hooked.

Dozens of papers later, I’m slowly building understanding of these… and building my own.

The original IKO is fantastic, but requires a deep pocket or institutional funding. AFAIK, there’s just a couple of artists who own one. What if you can’t afford one?

Based on IEM’s Franz Zotter and Riedel’s work it’s possible to build a much smaller and more affordable version - called 3-9-3, for speakers layout. Several other downscales have been made, including 1-7-0 and 1-7-1.

My path is a bit different… I plan to build something that’s based on the learnings of post-iko mixed-order beamformers, like the 3-9-3, but comparable in size and power to the IKO. So far so good…

So, here’s my progress:

Along the way, I met so many interesting people, that openly and wholeheartedly shared their know-how and experience. Thank you!

I mentioned the festival - we’re turning this amazing decaying temple where I shot two short films (The Chapel and Rebirth) years ago, into a spatial sound instrument, and the idea is to merge sound frontiers, and spatial sound with improvisational spirit.

OK, what’s the deal?
I’m posting here to see if there are any other folks out here either playing with these, composing for it, building their own…

Also, I’m interested in developing relationships for future performances including these beamformers, which could go either way - i.e. I may want to invite you to Echotronica and I’d love to participate in your events/installations.

Holler at me, I’d love to meet you and chat.

Here’s how you can follow my path:

Patrick
P.S. I’m not sure if SPAT is the bet category, but out of 400 forum categories here it looked closest.

pacocreative · April 8, 2025, 11:23pm

Explored various approaches to sizing, layout and speakers choice.

tcarpent · April 9, 2025, 9:23am

Hi Patrick,
Thanks for sharing the info and your enthusiasm !
I’ve forwarded your post to a number of artists in the field.

Best,
T.

pacocreative · April 9, 2025, 9:55am

Thanks T, that’s very kind of you. Let’s see where this path takes us

pacocreative · April 29, 2025, 3:31pm

Following my previous post, a few interesting people have reached out to me, which I really appreciate.
A couple of folks also expressed in acquiring these beamformers — that’s actually quite cool.
While the progress is solid, there’s still a lot to do. So here’s an update.

Big picture:

IKO and IEM/Sonible work is the Rolls-Royce class, but not everyone can afford it
Goal 1: come up with a practical approach to build affordable and performant SBAs (for myself, and potentially other artists), somewhere between the IKO and 393s
Goal 2: Push the category and research forward, both in terms of tech and artistry

Progress

Built a 393 - not quite an achievement, but a good starter
Explored, simulated and designed possible scale-ups and other layouts (more below)
Thoroughly researched the market for drivers, amps, and enclosure manufacturing
Got a pretty good understanding of the entire filter design thing, revived and incremented upon IEM’s repository for simulating and filter design of SBAs.

Findings

Amps

Amps are still a challenge. I’ve scavenged nearly entire market for multichannels, and for now I do have a compact, affordable and sufficient solution for 16-24ch, likely better than what I am aware has been used on the lower-end side. But I don’t consider it a full victory - there’s a room for upgrade for me, and there’s a gap on the market for sure (which I am potentially looking into filling at some point).

Drivers

393s and similar scale downs use fairly small drivers, therefore it’s easy to find a full-ranger.
The original IKO uses much larger drivers, and these are state-of-the-art, full-rangers. They are great, except for… their price.
My main challenge was to find an alternative for large and medium size drivers. With eyes bleeding from comparing countless options, I settled for a few choices, ordered, tested, measured and even accidentally made a pair of decent HI-FI speakers along the way So far so good, at least this chapter closed.

Never underestimate the power of prototyping.

2. Speaker Designs and mixed order control
Building on 2019+ Zotter/Riedel work, I calculated and evaluated nearly all reasonable speaker layouts and mixed-order control schemes for configurations between 15 and 24 speakers.

I have to admit that the established approach is hard to beat - layouts used for 393 (4th order) and IKO (4th order) hit a sweet spot in terms of combined 2D+3D spatial resolution

Several options I explored seem to push horizontal resolution even further, which is actually promising!
Layouts like 6666 and 5775 (both 24 speakers) seem to beat IKO’s theoretical resolution, which is understandable, given 24 speakers instead of 20.

The increment over IEM’s repo scripts is extending the simulation across a range of speculative beams and integrating results over them. This provides way less misleading picture of tested layouts, especially that resolution plots can vary a lot beam-to-beam.

Control scheme
I’ve been exploring various control schemes, primarily combining IEM plugin suite and dedicated MIMO FIR filter sets. These subjects still raise many questions for further research, but it seems that reliance on ambisonics-only workflow for compositional work could be a bottle neck - my crude observations have been that the footprint of a single beam as soon as it’s encoded in ambisonics, is large. Therefore for my artistic practice I plan on using the ‘ambisonic bed’ and combine it with discrete channel control for high-precision spatial accents.

This is still pretty much an open chapter.

Enclosure manufacturing
Encouraged with the 393 ease of print, I definitely did bet on going 3D print vs plywood for the larger watermelons.

That was a cold shower! Apparently, the challenges of 3D printing enclosures grow exponentially with size and weight of the drivers, and so do costs. Anyways, It seems that I’m still on a path to 3D print those, at approx 45-52cm diameter.

Ambisonic dome anyone?
As a side effect, it seems I’ve come across a really inexpensive way build of an ambisonic array, including high-end single-cone full-range drivers, custom 3D printed enclosures, and off-the-shelf amps to drive these. Someone mentioned to me Ottosonics, and this is could be seen as taking a similar path. Silghtly pricier, but but should be easier avoiding DIY-ing the amps and with a bit higher-end drivers.

It seems now I’ll take that route for the Echotronica festival, instead of building an ambisonic system using off-the-shelf studio monitors.

And one more thing
If you’ve read until here, you’re probably quite interested. Thanks for that. I just shared a deeper writeup on the genesis of my obsession with the watermelons, and a summary of my 3D audio trip to Berlin last month.

Finally, a well due credit goes to the team over at IEM, particularly Franz Zotter, who’s been supporting me and my silly questions thoroughly along the way. It would have been much much harder without it.

Please do get in touch - I love meeting ppl interested in everything 3D sound, and making these tools sing, and the connections I made so far are totally awesome.

Best,
P