Sunday, 15 January 2017

Horn Loudspeaker Exporations

Horn augmentation of sound is a natural occurrence. Ears and vocal chords use them for the perception and creation of auditory elements. This is but the first of what could be a long list of horns found in nature. It is not much of a stretch then to assume the use of horns is helpful in the reproduction of music. In the public address and large venue application they have been used with great success from the begginig of sound reproduction until today. In the home or small venue it has also been used but with less success. This is because what was developed for the large venue was also used in the small. Many horns and related technologies were designed to disperse limited amplifier energy into large volumes of space to accommodate crowds of persons. They employed techniques to provide limited bandwidth to large volumes and to punch dialogue through heavy cinema screens. If you moved from the balcony of a theatre or concert to just in front of a loudspeaker you might expect it to be overpowering. As obvious as this might be this is exactly what has led to the audiophile perception of what horns sound like - harsh and generally without refinement. The majority of horns and drivers available have been developed for PA use.



Some horn devices have been developed for home or small venue application but have been lost or misunderstood as time passed and public awareness went toward less sensitive devices. The Voit/Lowther is one of these. Originally it was a horn driver - not for direct radiation and coupled with a rear horn as it is often used as today. It is no wonder that it developed a reputation as "shouty". Altec theatre horns suffer much the same misapplication in the home. They were designed for large venues. Western Electric collectors fair better as the tricks to get different dispersions were not yet employed on these earlier designed horns. Where does this leave the common person who desires fine music in the home? It seems it leaves them without the most natural of all sound augmentation devices - the horn and so higher distortion devices have traditionally been employed. Paul Klipsch declared that lack of sensitivity equals distortion - it is an axiom which is unavoidable.




This oversight can remedied although there are always concessions. Size and frequency are inevitably related. Researching the quest of horn systems which were designed for small venues revealed often repeated errors, innovations and rediscoveries of lost technologies. Predictably, knowledge was lost as other speaker technology displaced horns. As home application was never the main body of commercial knowledge - these two elements marginalised the development of home horn systems. One of the great exceptions and greatly overlooked horns is the Western Electric 32 horn which was patented in 1935. Not only are the Western Electric 753, which uses this horn, one of the most costly and rare of collectable speakers but musicians and recording engineers used the same horn for near field monitors until it went out of production in 1984 making it perhaps the horn in longest production - ever. This then was a natural starting point when seeking a small horn for average sized listening rooms. The more that came to light about this unusual and well developed horn the more interesting things became and this is primarily because it sounds particularly good.




D.G. Blattner of Bell Laboratories was granted US Patent #1,996,743 for this type horn in 1935. It first became known as the Western Electric 32A and later, when WE was broken up by anti trust legislation, it was licensed to Altec which changed it slightly into the 32B/C, casting it in plastic, shortening it, and adding external braces to make it more rugged for stage touring and roadie handling. Listening comparisons between the two reveal a similar character with the earlier model being dryer and the later being a bit richer. The earlier version was originally used with a phenolic diaphragm known for less extension but more natural vocal range. The plastic horn appears to be an adjustment for the later AL diaphragm which has greater high frequency extension but less rich vocal range. In any case there is no question this little horn has a remarkably natural presentation in the near field and is a pleasure to have in the home. It brings many of the virtues of the horn - nuance and dynamics -  without the harshness and distortions many horns have.

Ladies and Gentlemen  - the 32 horn:





One the more unique horns in Altec's inventory and one of the longest in production. The design originated with Western Electric and was available to Altec as part of the 1938 consent decree that established the firm. 


Western Electric used it with 713 driver in the the 753 Loudspeaker.










Altec used it in systems with the 802 and other 800 series compression drivers. 

The most famous such system was the A8 Voice of the Theatre speaker which was widely used in movie theatres. 



 


It was also used in 9849 studio monitor





The late 70's saw its incorporation in the Model 15 home speaker system. 





A variety of Pro Audio stage monitors used the horn such as thePro R&R Stage Monitor N482 which had a cult following among stage musicians.



We was have incorporated this horn into the Hadron Loudspeaker for the home because of its natural sound field and refined response.

Azzolina Audio Hadron Loudspeaker



Happy Listening



Sunday, 20 November 2016

European Triode Festival 2016

Wave 1


This was my first year at the ETF and so, as is inevitable to initiation in any tribe, wore a name tag with an imaginary "newby" highlighted over the actual name. This is as it should be and it was mesmerising to see the differences in this event to any other show or meet - it is unique. The wide variety of approaches, real time building and modifications and non-commercial sharing of information was WAY too much fun. It could not all be taken in, too much going by too fast so the best thing to do was just ride the wave you happen to have caught at the moment. In the spirit of that here is a first batch of pictures.

 Super Sexy and Rare RCA speaker. Check out the (tweeter?) petals.


Vintage city.




Reel to Reel madness - Telefunken no less.


What is it? 

A microphone umbrella! To give the mics a shadow from the room bounce.
Made from unwashed, lanolin laden fresh wool.


All preparations for the shootout which was the taping and playback of a live musical event.











More on this later...


Modified (recreated?) compression driver.


Norwegian Wallflower of Sound.


Made especially for the event.


Amazingly life like and rich. From Joni Mitchell to Deep Purple. 
Hats off gentlemen!

More to follow... on the next wave.


- Photos curtesy of Camila Barcha, Copyright© all rights reserved.

Friday, 11 November 2016


Visit to Elrog Tube Factory!

European Triode Festival 2016


It is a three day drive from our home in France to the ETF in Denmark. The car was filled to the brim with speakers, amplifiers and other gear. We decided to limit driving to eight hours a day in order to have some energy left once at the show. Thomas Mayer of VinylSavor and recently the new proprietor of Elrog tubes invited us to visit the tube production factory on the way. What better way to get ready for a triode festival than to visit a triode factory and see how they are made. Like the making of transformers the art and science of making tubes is one of the great mysteries of audio reproduction. It was a treat to be invited to see it in person, especially one who's roots are woven into the history and lore of Telefunken, one of the mighty institutions of tube development and manufacture.



There were plenty of adventures before we got there though. Lots of snow and resulting accidents made the drive long and tiring. However the snow made the small town of Hagenow, where the Elrog factory resides, look like a Christmas Fairy tale. The old buildings beautifully kept and covered in snow was like stepping back in time. The walk to the factory from the hotel was filled with snowfall and people shovelling the sidewalks. They smiled and nodded to us - perfect strangers - in a small town. Nice.


At the factory Thomas greeted us and we sat in his office catching up. It was hard not to look at the tubes and start tube talk right away. On the shelf amount the current production tubes was a monster transmitting tube I did not recognise. He saw me looking at it and told me what it was and said they will be putting it into production. Nothing is sexier than a monster transmitting triode. My mind scanned ahead to see these glowing in the listening room. Soon we were on tour in the assembly room where the grids and heaters are welded onto supports in small and precise three dimensional sculptures. The care and skill was impressive to see. The many different kinds of wires and materials, winding machines and precision welders were fascinating. My mind raced unsuccessfully to see how it all worked while trying to be polite and keep conversation and introductions present and attentive.




We walked past the the science fiction machines of the vacuum extractors. They were large and impressive - harking back more years than could be imagined - recently improved to raise the vacuum level to increase performance and reliability. This is part of Thomas's production history showing, front end loading quality into the production not only for a better product but also greater sustainability in achieving the bottom line. Quality improves sales and reliability equals lower cost to both customer and manufacture long term.







Next was the testing and burn in room. Tubes were everywhere - in heavy racks, in boxes, in the test stands. So many tubes were hard to see without wanting to take some home. I had to remind myself that I don't have an amp for them - yet. We were introduced to the tube Guru at the centre of production, Matias. He was in the middle of testing when we walked in, the 300B tube under test was glowing nicely, the thorated tungsten filament is easy on the eyes, warm and bright - quite attractive. After introductions Matias began explaining what he was doing in running the tube   
through its test points and documenting its characteristics. I was keen to hear this 300B which is unique in 300Bs by having this type of filament. My experience is that this filament is often clearer and more pure in tone than the more typical 300B oxide type filament.






After years of using vacuum tubes, looking at them and wondering how they worked and were built, imagining electrons boiling off heaters, floating in clouds while the grid releases them in waves to wash over the plate it was a strange realisation to be in a place where they came into existence. The chemistry, physics and skill required were obvious. The history of practice and profound understanding required left a lasting impression. Building a device which runs to such extremes, which defies the atmosphere and burns like a little sun, is not an ordinary enterprise. After all they are taking music, turning it into fire and light, and then turning it back into music again. It was hard to fall asleep that night thinking of all the machines, processes, purity of elements, magical RF induction making metal glow red, swarming around in images with the eyes closed.


Our thanks to Thomas who not only was kind enough to invite us to see a little of these mysteries but also for sustaining the production of such a rare device, a modern thoroughbred of current production classical audio tubes.





My first Elrog tube!




- Photos curtesy of Camila Barcha, Copyright© all rights reserved.


Friday, 4 November 2016

Horn Loud Speaker (European Triode Festival 2016 preload)


Ah, the horn loud speaker - so much has been discussed over the years and strong opinions of them are common. Opinions run strong because the performance is pronounced in either a pleasant or unpleasant way. When implemented well they are quite astonishing and like any powerful tool they are not easy to implement and can be hard on the ears. It is but one of many tools a loudspeaker designer can use. Certainly it has its place in sound reproduction since the very beginning, that is not an opinion - that is a fact.





Loudspeaker elements include the cabinet, driver, crossover and sometimes a horn. Theses combine to create one of the most complex interactive/reactive environments of the sound reproduction chain. Science is but a girl's phone number, you still have not called her, gotten a date and certainly numbers have not made you the beneficiary of her first kiss as Sakuma san so aptly pointed out. As virtuous as the Nerd in us can be he can only provide the phone number and then his job is done. Wazniac did not get the kiss -  Jobs got the kiss.  The ocean's ways are mysterious and its limits unfathomable. The intrepid must navigate not only with science, but also intuition and courage. The vibrational and AC analysis of a loudspeaker in action while reproducing music would look like more like a storm at sea than any other analogy that can be thought of.

Having designed a series of horn and more conventional speakers over the years and coinciding with the European Triode Festival, ETF 2016, we decided to create a horn loudspeaker for production that was not only well behaved in high performance but could also fit into a normal domestic space.


A fine early example of this was the Western Electric 753c which is known for its reasonable size, unsurpassed midrange and magical blending of horn and conventional woofer.



753s are rare and unapproachable to obtain, however, the elements and lessons it provides are not. 

Japanese Audiophiles had discovered a variety of good sounding horns, including the one in the 753c, all of which which combined well with the early Jensen/Magnivox 15 inch drivers. Thus it seemed that this horn and a similar driver to the Jensen/Magnivox would be appropriate to explore.


Horn Tastings


Since there is no current production of the Jensen or Magnavox woofer a ProSound manufacturer was commissioned to design and produce a proprietary driver using the Jensen elements combined with the modern horsepower of an overbuilt motor and chassis. The result is a 15" driver which can process 450 watts of continuous musical power while providing 97db/1 watt/1 meter of sensitivity. Obviously it is not the the 123db sound pressure level which can be generated that is of interest but the detail, nuance and power which can be expressed before the first watt of power is utilised - though it is fun to turn the high end room into a dance hall on occasion. The motor was researched in detail and it became clear that resources were best spent on performance factors other than magnet type. As much as I have been a proponent of the differences in magnet kind it became abundantly clear that the size and type of voice coil has an equally great or greater influence on sound - much as a circuit type has a higher tier in hierarchy over an output tube - the motor circuit has more elements than the magnet. Large, high quality voice coils have considerable significance by providing more area in interfacing with the magnetic field and the quality of the electromagnetic field it generates is of equal importance to that of the magnet. This new woofer carries the largest and highest quality voice coil that could be made on current tooling. There is no alnico or field coil tooling that could be found to provide the magnet required for it and this then presented a dilemma - the choice of two ways. A hard decision was made to buck the vintage trend and make a commitment to performance over marketing. 



The M15 Shaded Dog driver is the result.




The horn exploration of some years ended after hearing one of the oldest horns in continuous production. It originated with Western Electric and became part of the anti trust consent decree that broke Western Electric into smaller companies and was bestowed upon one of the resulting subsidiaries named Altec. It is an early exponential design with wide dispersion. It does not have the abrupt bends and transitions of other modern, commercial horns and as a result is presentation is more natural and "unhornlike".






The compression driver selected for initial prototyping is a vintage alnico unit known to work well with this horn. Beryllium diaphragm will be tried as will a field coil. A WE555 can be fitted and is proven to work well in this application.


These elements required a vessel to house and support them through the interacting vibrations inherent in their work. Load paths, wave propagation and vibrational dispersion were included in the cabinet design development. Over a year of CAD design work was undertaken with the help of Camila Barcha, who is an architect, to prove and execute the concepts in detail. We had a lot of fun discussing concepts and creating the braces and arches. The concept was architecturally inspired after all while walking under the golden means arch of Khan's Kimbelll Museum and noting the difference in ambient sounds where they became more quiet and even. It took some thought to understand how and why.






Light and rigid construction was indicated for low loss reproduction. This vintage approach can be seen in any many early designs. 


Golden means architecture for harmonically proportioned dispersion and distribution were implemented. 


Semi-Monocoque construction was utilised for lightness and rigidity for which it is also indicated for for boats, aircraft and musical instruments.

After trying to get several cabinet makers over the years to follow the design parameters it became clear the a prototype/model was required to demonstrate the concept and construction techniques of the design execution. I had to build them myself.












Guitarist, teacher and Luthier Eddie Freeman taught me some things about wood working, playing and building musical instruments. I began study at the age of six.



I do not believe a loudspeaker should be built like a musical instrument - they have different jobs to do although there are some similarities. It was not intentional that some details were influenced by this early education. I did not realise until looking back at the construction and remembering... He would always ask: "Catch on?" after showing me something.
My gratitude for his teaching and influence. 




Real world driver measurements were taken in house for cabinet tuning and design validation. It was rewarding to see CAD and real world practice come together.







The design has so far exceeded expectations and continues to improve during advanced voicing and tuning. 






We hope to show the production test mules semi-privately for the first time during the European Triode Festival 2016.






These test mules have interchangeable panels for quick changing ports, drivers and horns. Production units will have a single piece front panel without bolts and will be finished in Walnut, Maple or custom veneer. 

Here is a video of them playing music:



On the future agenda is a cabinet with Ultra-Flex/Onken inspired tuning, the possibility of tooling up for a field coil and transformers designed for individual tubes at specific operating points. 



- Photos curtesy of Camila Barcha, Copyright© all rights reserved.





Notes:


Load Path - A load path can be defined as the assemblage of structural elements that "transfer" a load from its point of application to the point(s) of reaction.

Loads will follow the shortest load path because it is usually also the stiffest. The stiffest load path will also carry the biggest share of the load. Any change in direction of a load path will induce high local stresses due to bending, that is why the elements constituting a load path should be as direct and robust as possible.

Monocoque (/ˈmɒnəˌkɒk-ˌkk/) is a structural approach whereby loads are supported through an object's external skin, similar to an egg shell. The technique may also be called structural skin. The word monocoque is a French term for "single shell" or (of boats) "single hull".[1]


Semi-monocoque refers to a stressed shell structure that is similar to a true monocoque, but which derives at least some of its strength from conventional reinforcement. Semi-monocoque construction is used for, among other things, aircraft fuselages, car bodies, motorcycle frames, and musical instruments.