Friday, 12 January 2018

The Western Electric KS12024 horn in more detail.



This post is to explore why the KS12024 horn stands out as one of the best sounding of all small horns. What is different from other horns? How do these differences influence its sound and can we understand them? It is important to remember that if we observe a difference and cannot explain it this lack of explanation does not mean there is no difference.  It only means we have not yet been able to catalogue and attribute it but still the difference remains. Some electrical engineers have disagreed with this and argued that if it cannot be measured and explained then it does not exist. This is a banal error (so lacking in originality as to be obvious and boring) and can cripple eventual understanding. Science is a tool, and a very useful one, but if you let it run the show it will still be a tool. When science can reproduce a Stradivarius, or better still have created one in the first place, let us speak of this again.



Let us begin with the observation - the KS12024 horn sound. I shall use other observations than my own - a conversation from a Japanese publication:

"Atarashi: The first listening of the KS - 12024 horn is pretty good and very impressive. Colourful expression but very soft and right tone.


Shinoda: Good compatibility with the WE555 – very balanced.
Doi: KS12024 horn is the core of Westrex sound systems.
Atarashi: You understand when you hear ‘’Casal’’ with such a good quality. The fact to clearly hear both the sound of the ringing and the sound of the string body, both being organically overlapped, gives the firm presence impression of the cello. Emotion is well transmitted, as if to express the music with the help of like Casals Bach. It is an emotionally rich sound.
Shinoda: I am not focusing on scratches on the SP record; I can concentrate myself on music. I feel a sense of depth and it sounds quite well.
Doi: More noteworthy, it is no fun listening to music. No likes and dislikes of music genres.
Atarashi: Yes. "Casal" as well as "Sonny Rollins" or "Kay Starr", all are lively and enjoyable performances.
Shinoda: I think this system tends to give a HiFi tone, I’ve felt the energy impression and the thickness of the sound together. For example, "Sonny Rollins" in front of the stage, plays saxophone lively first, joined by strong sidemen from behind with Max Roach, you can hear the music even more impressive. That’s because there is a bodily sensation, you can feel the thickness part of the sound, performance is close to the human perception without being disordered.
Doi: There is an energy impression in sound, at the same time also the tone is beautiful. However, it is wide range, as if it was a full range system. This is a very valuable horn, which gives the best quality of the WE555 driver, according to me.
Atarashi: When you heard the sound of this combination, you think that extension of WE555 is not difficult to obtain (laughs!).
Shinoda: I agree. The WE555 is splendid, and this sound is difficult to obtain with many horns."













Quotations taken from this publication.


There it is - on the ground, laying in the grass, a perfectly good gauntlet. Let us pick it up.



On initial examination the horn incorporates:

1) Simultaneous and varying exponential and linear expansions.

2) Multicell seperations which begin about 70mm from origin of throat - before the bend and change in opening angle.


They look like this at their beginning.


Profile x-ray view shows where these begin - before the introduction of the curve and increase in linear profile.


3) A 45° bend 90mm from throat origin where the linear opening angle increases from 30° to 50°.



This poses the question of a possible correlation of the bend and increase of linear opening angle. 




4) Throat size is WECO standard 0.7" or about 18mm

5) Cast aluminium has roughed surface perhaps performing boundary layer excitation (BLE) - the intentional creation of small modes which prevent larger ones from developing. Earlier in wooden horn building I was surprised that the horns sounded better before they were sanded and finished. The better they looked the worse they sounded. This is perhaps why. Of course we stopped finishing them...


A simular texture is used in reproduction for this reason.



6) Exponential expansion begins after 180mm from throat origin alongside the linear which continues and determines the output pattern. The linear propagates in the lateral expansion - the exponential the top and bottom. You might want to call this a radial horn however it is purely linear for the first 180mm, then becomes the hybrid which is termed radial - but with multicellular separations.


In conclusion the expansion is 30° opening angle linear for 70mm then this is divided into 4 asymmetric linear cells which approximate exponential expansions. These increase to 50° linear   in total at 90mm and go for an additional 90mm. At this point another exponential expansion begins on the top and bottom (going into radial) further increasing the expansion accordingly. It is a thus compound horn: linear 30°linear/multi cell 50°, then radial multi-cell.


Further interior examination shows there are two different countours of the four cells. 



These are grouped as the two internal cells and the two external cells. Each being slightly different to each other. These individual linear expansions appear to approximate exponential.


They are different even if we consider the spherical wave expansion as can be seen in another x-ray view.


This is probably enough to get us started as there is enough here to separate the 12024 horn from any other other horn we may know. I can only wonder how this horn was developed.

The Horn material makes a difference in the sound - as sound waves inevitably travel through solids with increased speed and the material alters them like a filter - accentuating some frequencies while attenuating others. These waves then leave the material ahead of the sound waves traveling only in the air inside the horn. The original aluminium lends a ringing character (or glare) when compared to plastic, wood or bronze as can be expected. Plastic improves on aluminium in reduction of glare and is noticeable when directly comparing the two materials side by side. AL was probably selected for it's ease of fabrication or/and ruggedness in a commercial environment rather than for epicurean reasons. Bronze takes on a quieter, clearer and more present aspect. It also lends a sweetness or naturalness something like nickel does in transformer cores. Wood has its own and lighter form of natural sound. Combining these works very well.




In summary, all of these elements combine in a horn which is singular in its natural presentation. It can go lower than other horns with similar mouth areas because there is less distortion near the mouth cut-off frequency. Most horns need a margin of an octave, or half and octave at best, above the mouth cut-off frequency to avoid noticeable distortions. The KS-12024 does not seem to require as much margin resulting in a smaller form factor for the frequencies it can propagate well. It is one of the best of all small horns in doing what it does.





In the another post I will talk about different drivers in the KS-12024 as well as compare the LM555, TAD 2001 and our proprietary driver with phenolic diaphragm.

Until then...





Thursday, 14 December 2017

Western Electric TA-7331-A Baffle

Western Electric - what to say and where to begin?

My guitar teacher played violin and piano in silent movie theatres before the talkies came. Their arrival put him out of work and so he moved to the bandstand. They had live music in theatres before sound reproduction - that gives a pause. It is inevitable to inspect what the founders have done. The Far East had a head start as US Occupation forces left a trove (a store of valuable or delightful things) of Western Electric equipment abandoned in a wide variety of venues: theatres, schools, auditoriums etc..

It should be no surprise that the wealth generated by Sound in Cinema attracted performance driven research and development. The emotional response of the crowds directly related to attendance and to money. Not only was performance achieved - knowledge of it was carefully controlled - even destroyed. Ninety four years later there is still a shroud of mystery keeping all but a lucky and dedicated few at bay. It is called the sport of kings for a reason. Collectors have not only preserved artefacts which would have been lost, they have also driven prices beyond scope. It is doubtful that this will change.

There is a plethora of public information and if one lets go the objects of fetish (a form of desire in which gratification is linked in an abnormal degree to a particular object - or - an inanimate object worshipped for its supposed magical powers or because it is considered to be inhabited by a spirit.) then it is still possible to experience some of this excellence in civilised terms with a little care and diligence. 

We started with exploring the Western Electric 32A and KS12024 horns. After having them X-rayed, scanned and relief penetrated with silicone and latex we came to know them better than the collectors - or at least better than what the collectors were sharing. After successfully reproducing them and avoiding some of the common mistakes it was clear these horns we not only as good as modern equivalents but that they were easily more natural sounding. The explanation of which is for another thread. Now is the time to explore what to match them with. We begin with the TA-7331-A Baffle which was chosen because it can fit into a reasonable sized listening room. 

The original documentation is comprehensive and dense.

After sourcing the indicated quality coniferous plywood, and support lumber, construction began.



I was not going to trust a shop to do this one.



The pinewood was a pleasure to work with.



Despite the desire to improve materials and fasten with biscuits the construction method of the documentation was strictly adhered to.



This was to create a baseline for any future refinements to be compared.



I was sceptical of this design as it breaks with some of my expected notions. After assembly and before any finishing it was impossible not to have a quick listen. There were thoughts of the fire pit outside to which the several cabinets have been disposed of after testing, Onken and Ultraflex to name a few. Nothing like a glass of wine and a fire to celebrate the difference between a myth and a legend. It is amazing how large a cabinet this little pit can support while it burns and the Limousine rains clean up most of the mess... if the weather is inclement it can all be watched through six panels of glass door. Chin, chin.



The nearest items at hand were combined for a quick read on if this thing had potential - a 12024 horn/TAD driver, a crossover borrowed from the 515 cabinet,




and an Altec 414. 


Quick and dirty.



My suspicions were confirmed with a decent sound but with boomy and boxy congestion. After two alignment adjustments though we were pleasantly surprised. The elements came into place with speed and focus. It was good enough to be disconcerting - puzzling. Measurements will now follow for proper crossover development and the acoustic design will be studied more carefully. It has been noticed that every image of this baffle that could be found on the internet uses 15" or 18" driver while the documentation clearly indicates a smaller driver - the Western Electric TA-4171 of which there is scant information other than it was a 12-13". However the designated aperture is clearly 11 1/2" and thus an appropriate sized driver was implemented. The 414 12" demonstrates that the documentation might be onto something. There is a line of drivers that will be tried including 12" and 15" field coil units but this is certainly a "return to point" for measurements and listening satisfaction. The emotional connection and life like presentation are quite good.






One of the disconcerting elements is how well these two loudspeaker elements combine - quite seemless.  I look forward to what a crossover tailored for them will do.

Finishing, measuring and driver shoot outs to follow.

Until then...





Saturday, 18 November 2017

Last day and some tube porn

All good things have to come to an end...

Time to pack up.



But First some nice summary shots of the gear.



GM70s in full blaze



Very nice shroud around them.




There is nothing like transmitter tunes with throated tungsten and cherry red plates.




Even little ones look the stuff.



Mercury vapour not only sounds good but has the spooky blue glow.



When combined with the cherry red...



It makes for good company like a fireplace.



You can just look at the glow and relax...



while listening to the music.



Until Next year!




Thursday, 16 November 2017

Prep work for the shoot out

Ahh the shoot out...


The day of measurements and phase alignment with the subwoofer.
The pressboard wall behind is the open baffle of the woofer section.



Sound checks...


Positive results.


Oops - the bargain table with lots of things to temp.




Some little conversations about the fish we have caught...



Live music.



Including JC providing examples during his lecture!



And the test bench so generously setup each year which illuminates and keeps feet on the ground.

Sunday, 12 November 2017

Celestion Axi2050 and some serious horns to go with them.

Here is a very serious horn setup.

Classic curves and straight throat.

A variety of choice front ends from vintage reel to reel, broadcast turntable and pro digital.

In the corners are giant black boxes with bass horns...
A bipolar tweeter horn of inspired design.


Hand made.

Hand made transformer attenuator.

Vintage compresion drivers.


and... the fabled Celestion Axi2050 which goes down to 200hz!


It hopefully will be availible one day but for now this is about as close as any of us are going to get...


Thank you to the Norwegian group for sharing this formidable setup!