Giant Custom Horn Systems - How they sound and issues with sonics

I definitely dream of one day building the ultimate system and room. I see what some of these crazy guys do with truly giant custom horn installations and they make me drool, but (like most of us) I've never had an opportunity to hear one of these crazy systems (see pics).

But I'm guessing at least a few of you have and others probably possess some theoretical engineering knowledge around the issues these giant horn systems might create, but I've never seen a thread that discusses the sonic pro's and con's of these systems.

Would love to hear some thoughts (even if it is just some pontificating on theory) regarding these types of installations. Let's discuss.
What drivers do you use in yours?
I use today's drivers.
Neodym 15" driver for the bass horn, a 7" midrange in the large white horn (120Hz-4KHz) and a 1" driver in the small round horn for the treble.
It is a quasi coaxial system.
Also some subwoofers, based on 8 15" drivers in infinite baffle and one 18" driver in a 2.5m tall tapped horn.
The crossover is passive and the 3-way coax horn is driven by a Totaldac Amp-1 amplifier.
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Jeffrey, apparently anyone having disagreement with your thoughts is that correct?? Like I said, if you like horns..well good for you, but others are not so enamored. Personally, I cannot stand the fact that all the horns I have heard image poorly, are shouty, are almost impossible to sound of a piece if utilized with any kind of dynamic subwoofer, and are completely unrealistic as to tone and timbre. Dynamic, yes they are indeed that...but music isn't just comprised of dynamics....musicality has to have some factor. All of the above IMHO. YMMV.
BTW, what value are you adding to this thread...???? Except to try and rationalize your love of horn speakers, LOL.

I'm just a casual observer in this thread, but if ur a dynamic driver kinda guy - how do you explain that Magicos top speaker is horn loaded - everything else infinite baffled boxes?

I've only heard horns at shows save when I heard some at length at a dealers home and found them to be very good in taking you to the live event particularly in terms of image (it might be because they were front firing and used a single driver)

I recall speaking to these two 'old guys' (trust me they seem to be younger now) and being told the the ultimate system they heard, which has never been matched was a horn that passed underneath the floor to the seated position.

My own question is who designs them - with something being made part of the architecture how are they calculated - you'd be up a creek without a paddle without the correct crossover etc
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I had a couple of listens to the CESSARO VOICE OF THEATRE II HORN SPEAKERS. Too get the best imaging you had to be in the sweet spot..

One woofer VOT, like Altec A5, with probably active bass at the bottom below 100, with that closed two woofer box. Putting the tweeter in the middle affects dispersion as tweeter must be kept behind but other horn will be in front. Unless of course you raise the mid horn, which they seem to have done, but that will affect point source. Fine for a theater if you are sitting very far away. That said this design without the box drivers at the bottom probably evolved to the Zeta.
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My current set-up. Will return with a rundown on the specific components used.

Blasphemous perhaps, but in a few days will swap out (periodically, as an outset, and not with the necessary intention of selling..) my all-horn Simon Mears Audio Uccello main speakers with a pair of horn-hybrid pro cinema speakers from Electro-Voice, the TS940D LX ('LX:' meant for active config.). They house twin DL15W bass drivers and the DH1A compression driver fitted to a 90x40 coverage constant directivity horn, the HP940:

(partially incorrect data sheet)


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I'm just a casual observer in this thread, but if ur a dynamic driver kinda guy - how do you explain that Magicos top speaker is horn loaded - everything else infinite baffled boxes?...

As an equally casual observer, i do think there is real merit in these SOTA horns...the challenge (for me anyway) is that these SOTA horns seem so HUGE. I have never truly investigated, but the ones I read about...Western Electric, Biohorns, Vox Olympian (which really requires the matching sub otherwise i think you are paying 300K for a speaker that goes down to 70hz or something), the Magico Ultimate, Aries Cerat Symphonia, not to mention the big Cessaro Beethoven or others...

...i think cones are very space-efficient. And there are clearly those who would take horns over cones for reasons of their appreciation of horn qualities (which i respect). However, for me the choice of wanting scale, power, deep subterranean well as mids, highs, etc...means that to get that in horn-world is a commitment of square footage I am not prepared to make. Whereas there are a number of amazing cone speakers (for me) that have a footprint of less than 1.5 feet by 2+ feet (Wilson XVX) or even 2 feet by 3 feet (Arrakis) that present gargantuan scale, effortlessness, detail, etc, etc.
The pair of Electro-Voice TS940D LX speakers arrived today from Germany. Should fire them up tomorrow.

EDIT /update: they came to life today for sure, and based on first impressions with a very basic XO-setting from my Xilica unit the sonic outcome is very promising. Lot's of tweaking and tuning with delay, filter slopes, individual driver gain etc. now awaits. Extremely dynamic, big presentation, (a)live and rather coherent. Love the sonic sphere and strong phantom center image these create, even at this very early juncture.


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Hans Bristell * asked me to convey his long experience of big horn constructions

Part One Enjoy!

”The covid-19 is changing our lives and giving us a lot of spare time to reflect back on personal loudspeaker project. As an introduction to the horn history, Jean-Michel Le Cléac’h ( jmmic in DIY Audio) has provided a excellent summary.

The pioneer horn loudspeaker period was in the beginning of the 1900 century that was dominated by the film industry. The second horn period started after WW2, the main interest at that time was HIFI audio reproduction in the home. The DIY horn friends living in my part of Sweden began to learn and share ideas on bass horn. The inner DIY group was Bo Hansson, Audio Products, a consumer audio company and OPUS 3 a record production based on acoustic recording spaces and Blumlein technology that uses few microphones; David Shuttric an English mathematician and horn entusiast and Hans Bristell a loudspeaker and studio designer.
This local DIY group was influenced by the German Siemens/Klangfilm and the English horn industry, focused on Voight and Tractrix horn.
Bo Hansson and I was competing for fun to build the best subwoofer in home environment.
The famous sub bass horn was built in Bo Hansson's home as a bass horn under the living room floor. bo hansson basement horn.jpg bo hansson basement plan.jpg bo hansson horn.jpg bristell klangfilm.jpg bristell bl.jpg bristell concete horn throat.jpg bristell concrete horn mouth.jpg The horn was built in the basement and ended in the wall/ floor of the living room. It was a opening hidden behind the sofa. The stereo loudspeaker was placed in the living room.
The customer to Audio products was demonstrated the stereo loudspeaker without telling about the hidden subwoofer. The fun part was when the listener experienced subsonic frequencies from these two loudspeakers of made in Polycrete, a mixture of concrete and polymer beads.
This was pioneer design by Bo. The subwoofer horn in the picture (below), was built with this material. The benefit was low mechanical vibration in the horn.
The basement has a limited ceiling height of 8 feet, this required the horn should be folded in two parts.
The loudspeaker throat was located close to the ceiling in the basement folded twice at the floor, and the mouth ended in a long narrow opening in the living room with a dimension of 7x4x2,4 m. The transducer was a 15 inch klangfilm Tesla AOR 9415 alnico (VAC magnet).
My hand-made sketch of the horn is made after my memory and the pictures explains the construction in the basement. The horn was extended down to the 20 Hz region. The common impression from the listener was that the horn has low distortion and the tone character was dynamic, comfortable and pleasant. My emotions created by the low frequencies of the horn were strong, especially for Swedish and French built organs - they sounded fantastic. This sub bass horn put Bo in the forefront in our personal competition. This leaves me no peace. I started working on new sub bass horn prototypes in a basement recreation room.

My next sub bass horn was built with dry material to test different constructions.
A couple of folded prototypes in two sections was built. I was inspired by a Western Electric type horn using a Voight 7“ transducer. The pictures below show two horns folded once and merged in a integrated common horn mouth. I have used 15 inch JBL D130 in some of my prototypes with good results.
I ended up using a Voight transducer with B=2Tesla. I looked at a possible alternative, which was a Voxative Field coil transducer. I have read about the experiment with a variable B that Voight used in his design of The early field coil transducers. Voight showed that the transient response was a function of B Tesla force. With more B force, a better transient response was achieved!
This bass horn was built in a room with the dimension of 6x4x2.4m. The two horns merged in the front wall. The benefit of this design is that the horn mouth was dubble in size. This increased the frequency range and evened out the listening room variation of pressure at the listening position.
There are other important factors to consider when a horn mouth terminates in a rectangular room. The transition frequency of a room that defines the wave acoustics is by Schroeder frequency, under 200Hz in most rooms. The standing waves in the listening room create a variation of horn mouth acoustic impedance. This variation of mouth impedance will generate a back wave into the sub bass horn. This can generate standing waves between the mouth and the throat, creating a ringing in the pulse response, which creates horn distorsion.
In my next post I will show a differentiator solution to reduce this problem.”

Hans Bristell

* 40 years experience Acoustic design of studios and control rooms.
Project engineer for OB units.
Broadcasting live television program and post production of recorded program. Lived in US since 20 years
One of the few who has a certified LEDE room on his resume
Hans Bristell Post Two
Entering in the 80’s changed my priorities. I attended Syn-Aud-Con hosted by Don Davis during a golden age of studio design technology. LEDE was the next development after Tom Hidley and the Westlake period, with 800+ studios built around the world. Synergetic-Audio-Concept opened new doors by meeting with the world class studio engineers and acoustic designers. This experience and meeting creative people, changed the attendees' view as we shared our knowledge, forming a new world class of studio engineers. Don Davis was the hub in Syn-Aud-Con classes. Around 1979 Chips and Don Davis introduced a new studio design concept, LEDE (Live End Dead End). The list of talented people that was teaching the classes was impressive.
Richard Heiser, a NASA scientist and inventor of TEF (Time Energy Frequency), introduced a revolution in our understanding of studio acoustics by waterfall graphic presentation. Peter D’Antonio was a diffusion expert at Syn-Aud-Con classes. His mentor was Manfred Schroeder at Bell Laboratories. Peter commercialized the Schroeder diffusor in his company RPG diffusor. Doug Jones was a spokesperson for the deceased Paddy Rodgers, on her PhD thesis of the pinna effect / HRTF (Head Related Transfer Function).
The inventor of RFZ (Reflexion Free Zone), Charles Billelo, introduced his most famous RFZ design Master Sound Astoria. The hands-on of studio design was taught by Russell Berger of Joiner Rose Group, a studio designer company. This is just a fraction of the shared knowledge.
This opened a new world for most attendees and increased my understanding of the studio and acoustic technology. This new knowledge effected my studio design in a profound way. I was assigned at Swedish Television to build the first certified LEDE control room in northern Europe in the 80’s, followed by the first 5:1 surround sound mix room in Scandinavia. After establishing my own company I built a state of the art mobile control room, followed by a multi-studio complex for Walt Disney's Swedish productions. In the late 80’s I was involved in a opera studio in the country owned by Håkan Hagegård, a Swedish opera singer.
This lead to the project I would like to share, about my infrasonic bass horn control-room. It was a novel control room where I used all my knowledge learned at Syn-Aud-Con classes. It was based on LEDE by Don Davis and combined with RFZ by the deceased Charles Billelo. The control room was divided into two frequency ranges, the geometric acoustics and the wave acoustics - both are divided by the transition frequency (Schroeder frequency) of the room.
Wave acoustics was reproduced by a infrasonic horn. The horn was divided in three parts. The first tractrix horn part was hidden under the floor, and the second part was folded in the front of the control room. The third part was the extension of the horn forming the control room conical extension. (See below sketch). The calculation of the horn was done by David Shuttric, a mathematician and horn designer from England.
This was a demanding project. You have to combine the LEDE and RFZ geometric design with a infrasonic horn integrated in the control room.
It was a challenging construction, but well rewarded with an outstanding result.
I supposed it was the first infrasonic control room designed as a sub-bass horn.
The benefit of this design is to integrate the horn and the room to one acoustic transformer. The connection of a sub-bass horn into a regular room has been investigated in one AES paper by Björn Kolbrek. It was presented at the 146th Convention from 20-23 March, 2019 in Dublin, Ireland. The subject was Large Horns and small room - Do They Play Nicely Together?.
This is an independent view of my design to connect and integrate the horn in the room. This paper shows how the standing waves in the room create a variation on the room impedance connected to the mouth of the horn. The room should have as smooth distribution of standing waves as possible, to present a low impedance to the horn mouth. This reduces the back wave into the horn that reduces the standing wave inside the horn.
This results in a smoother frequency response from the horn. The connection of the horn mouth at the rear of the room was to a room with a volume of 4000m3. This volume presents an reasonable acoustic impedance to the horn mouth that was the rear end of the control room. This was not a free-field condition, but very close. The drawing and the hi-res pictures were unfortunately stolen.
I have made sketches of the room, from my memory of the drawings. I have saved some pictures that are low resolution that I can share with you. It is the construction of the first part of the tractrix horn, and the folding part of the front of the room and when the carpenter finished the floor on top of the first part of the horn. The room was designed as a conical expansion of the rear of the room.
The back of the room was acoustically open to the 4000m3 open space simulating a free field with standing waves down in the 10Hz range. The horn used some resistance to attenuate the possible standing waves inside the acoustic transformer. This was an invention by Gedlee used in their NS15 mid-horn design. The transducer in the throat end is a custom 15-inch woofer designed for infrasonic horn. It has a magnetic force of 2 Tesla, the same as in my horn in Post 1!. The ratio between the area of the throat, 315cm2 and the Mouth area, 25m2 (25000cm2) is a acoustic ratio of 25000/315 = 80:1. This is a good match of the acoustic transformer. I don’t know the metrics for this design. The floor plan is 35m2 and the dimension is 7x6x4 meters. This is a model of a full-size control room built in dry material.
The Brivox full size control room is twice the volume and the length of the horn is 25m. The shell and the horn are built in acoustacret, a proprietary material by Brivox. This material is working as a viscoelastic material with controlled weight, reducing structure born sound and improving the soundproofing of the studio. When building to a full-size scale of 70m2 of the Brivox Infrasonic room and using infrasonic horn, this should be built in acoustacret.
To compare to BOP, a studio built by Tom hidley in South Africa, the studio outer walls are built in concrete and a inner shell of dry material. The control rooms are infrasonic rooms with direct-radiating subwoofers 4x18 inch transducers in one box. The rooms are heavily dampened in the Wave acoustic range. The room size is about 70m2 and a unique future is there is an under the floor space with wave acoustic trap. The acoustics in the geometric range are non-environment acoustics mimicking a free field situation. The broadband RT curve has a very low value (close to free field). See below drawings of BOP Studio.
Concerning the infrasonic wave acoustics in the Brivox control room, I have no metrics to show more than a broadband RT curve close to 0.3 seconds. But I can tell you how my body reacts. First reaction was that my body was resonating around 7Hz and the SPL level was extremely high (130dB SPL). When your body begins to vibrate your inner organs are vibrating as well. It is a very uncomfortable experience.
The lungs are vibrating around 7Hz; when you talk the voice is frequency modulated in a way that is hard to understand what you are saying. Your eye globes vibrate, which causes double- vision, very scary. You begin to feel nauseous because your brain and inner ear are vibrating. If the SPL is increased, it can result in heart failure. This is the limiting factors listening to a infrasonic horn of this magnitude. If you ask me if the SPL and frequency range is good enough, I can give you the same answer that a customer to a Rolls Royce car was asking, "how many horsepower does the engine has”, and the answer was "more than enough.” I can give the same answer concerning the SPL and frequency range of this infrasonic control room, then it is 'more than needed.

Some comments about the geometric acoustics are a differentiator compared to BOP studio NEA (Non Environment Acoustics) after Wilhelm Lassen Jordan. In a Brivox LEDE room, a 10 inch wedge foam was used to control the earlyreflexions in the front of the LEDE room. The wedges have the double function to attenuate the higher order frequencies in the second folding part. At the rear of the room diffusors was used, i.e. golden horn that shattered the discrete reflexes to create a diffused transparent sound field at the back of the room. The side of the room I used what Charles Billelo called RFZ. He used mirrors to steer the discrete reflexes outside the sweet spot. This is the reflexion-free Zone (see below drawings). As an alternative, a Acrylic Wing can be used to diffuse the side wall window reflexions. Wing (nearfield broadband temporal diffusion) is what I refer to as the novel diffusor invented by Matts Odemalm at SMT Sweden. The Wing concept will be used in my ongoing project of Brivox studios.
bristell part 2.jpg brist 2.jpg bristell partt 2.jpg bri 2.jpg bri 2 del.jpg brivox 2.jpg brist 2 del.jpg bristell 2.jpg
I was in a store specialized in horn speakers. I was there to hear an amp. The amp was driving some cone speakers. The cone drivers were right in front of a large horn speaker. I kept telling the owner in could not hear correctly as the horn was amplifying the cone speaker. He didn't believe me. Owe well. I didn't buy anything that day.

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