Diamonds are forever!

So this is an auction that takes another approach to WAF…

Just place diamonds like that on your deck and WAF will be a thing if the past!

And the 16 is one of the secrets behind the audio16.com blog….

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Cable capacitance

A lot of mystery attached to cables and the impact on sound in systems. So some basics to keep the myths going….!

We all (?) know every cable has a capacitance value valued in picofarads per meter. This is the relationship of the dielectric of cable sleeve and conductors. It is like a capacitor in parallel between signal and ground. This capacitance acts as a low pass filter (rolls off tremble notes at 3db slope (3db per octave)). This is easy to calculate as below. The ruling factors are the total capacitance and source impedance. Total capacitance will be higher the longer the cable length. One just takes the specified picofarads per meter and multiply by length of cable used to get total capacitance.

Now…Cable manufactures tend to keep the value secret so as to entertain, I suppose, the mystical side of things. Professional cables are obliged to indicate these as they are providing pro audio users that will run very, very very…, long lengths of cable on set or in studio, meaning 100’s of meters.

Anyway to the basics and if you follow the maths below you get for a source impedance of say 100ohms and 2 meter cable with a very high capacitance (300pf/mtr) a roll-off of treble at…..2 652 582 hertz.

Or source 20ohms and 10 metres of 200pf cable : 3 978 874 hertz

Now 200pf or 300pf is huge! Typical cables will be under 30pf/mtr so in real life the roll off will be at an even higher frequency!…..

With our short lengths at home we should be okay I guess! Although perhaps my speakers and ears are not that good, meaning I cannot hear of feel that roll off at ultra high frequency.

You need some totally lousy cables and very high output impedance to get a roll off within hearing range….

Just as a reminder :

The higher the cable capacitance the lower the low pass frequency
The higher the output impedance the lower the low pass frequency

So you can run your calculations :

fc = Cutoff frequency at (−)3 dB treble loss in Hz
Zout = Output impedance of microphone, source impedance
Cspec = Specific capacitance of the cable in pF per m cable length
d = Cable length of the cable in m C = Cspec × d
1 pF (Picofarad) = 10−12 F (Farad)

Formula for the cutoff frequency fc of the (−)3 dB treble damping:

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Do I miss the we12a or should I?

Well they have gone to a good friends house and over time he will gradually install them correctly and feed with good sources, take care of filters, amplifiers etc…currently he is using on floor with subwoofer to support below. And as horn users know hanging horns is part of the beauty, mystery and sound….http://audio16.wordpress.com/2013/01/18/hanging-your-horns-2/

Looking back at this image made me wonder if I miss them or not? In my case I can make another pair whenever I want so revert to them is, short of time and money, a relatively simple thing.

In some ways yes I do miss them partly because these are unique pieces on the European soil and my 1st attempt at resurrecting these wonderful horns from the past. In quite a few occasions when discussing with western electric users who have extensive experience with them we come the saying at some point “if I had to do it all again I would just use mono”. I know that my good friend M would not disagree with that perspective!

With the we13a playing I am in that world and my whole system is now tuned to mono. It puts one hell of a relief on upstream budget, amplifiers, preamp…the we13a offers so much more in the realm of extension, dynamics and overall ease for listener. The freedom from the more complex xover on the 12a and the sheer length of the horn are the ingredients to this result.

I will be using the we13a in stereo once the second one is completed, been a bit lazy these days….perhaps my wood planes are getting rusty!

So do I miss the we12a? Yes……but the we13a even in mono gives me more of what I need…

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Testing sessions can get messy…

With some friends we set aside a day to test some variations around the we13a using the necessary tools. I say around as the 13a is the dominating factor. Not just physical perspective but also sound wide. The job is to delicately integrate above and below. Not unlike the other big WE horns in that regard. We used here we92a amplifier, the other one is a single end 300b with we171a OPT’s. Tubes from engraved 274a’s to the 300’s in same caliber. We4181’s in “open air” to open baffle.

Fun day….thanks W2 and D

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We13a and we12a a misconception…..

How many people on the planet have played with the 12a and 13a? I know quite a few of them….and so many forum dwellers out here are saying that the 12a and and 13a we’re designed so that the 12a did the highs and the we13a the low. This is a misconception stemming from a misunderstanding of frequency range of that era….these installations were not for THX or dolby nor for soundtracks from Diehard etc…..nope!

Extensive study of the history and available documentation enabled me to have learnt that the 12a and 13a were installed in large theatres as permanent installation and placed to enable the theatre to be used for live representations with orchestra etc..

These large theatres has orchestra level seats and balcony as we know.

The 12a was installed high up at the every top edge of the scene, the 13a in the pit. The 12a was for the balcony seats and the 13a for orchestra level seats. The signal sent to all the horns was the same. Sort of multi channel mono. The frequency response in 1926 was maybe 80hz to 5000hz?….the 12a goes down to 100hz easy as I have seen from Suzuki San’s (GIP laboratory) readings…and my ears! The 13a….ever easier!

If you study (I have) the installation schema for the 12a and 13a you will notice that the 13a had an autoformer to adjust the level. This was to balance the 12a no 13a levels in the theatre. No filters were used at all.

Once you hear the 13a you will realise that it needs no 12a at all.. we did a frequency check with generator and at 45hz it is unbelievably strong and full of “guts” and then goes upto 6000hz with ease (that is the top limit if the we555).

These solid wood babies play better than the plywood we15a or metal 16a (I have both…) as they are so solid and do not vibrate. This enables better control of the lower frequencies and dynamics are not reduced because of materials….

Been asked so many times now who made these horns…..yes it’s me with knowledge, skill, patience and most of all passion…..some have asked if I can make for them….depends…!

All fun….

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