Live from Munich : High End 2015 - The Speakers

Hi!

The speakers of out demo system at the high End are the Swing made by Wolf von Langa.

The Swing is Wolf's ultimate field coil speaker implementation.

With their high sensitivity of 99db they work nicely with the 5W from the single ended 300B amp we are using.

The open baffle construction gives a very detailed and open sound.

Due to the open baffle construction, the crossovers are in separate housings:

And the field coil power supplies come in similar chassis:

The wooden side panels give the speaker a unique look.

Visit us in room F231c to listen to the Swing.

Besides the Swing, Wolf also brought another, smaller model called SON:

The SON combines a field coil woofer with a air motion transducer.

The SON is used by Axiss Europe with Air Tight amplifiers:

Visit Stand T17 in Hall one to listen to the SON.

Best regards

Thomas

Making of a Field Coil Speaker, Part 4: LV FC PSU

Hi!

Finally I found some time to continue with the work on the speaker system. Up to now the woofer field coils were powered form an ordinary lab power supply. This got replaced now by something more appropriate.

A dedicated power supply for the woofers in a similar style as the high voltage field coil supply  of the horn drivers. The woofers are running at 7-9V / 3A. So no tube rectification. The PSU provides two independant voltages for the left and right woofers. Schottky diodes are used for the rectification. The filter is choke input using Lundahl LL2733 filament chokes.

As power transformers two of my 5A filament transformers are used for each side. Since each transformer only delivers up to 10V when all secondaries are wired in series, two of them needed to be cascaded to reach the desired output voltage range.

The supply is configurable with switches to adjust output voltage. The filter can be selected between pure choke input, or cap input with two different capacitance values:

Some pics of the assembly process, power transformers and some caps mounted:

Some wiring:

The completed supply before the bottom lid is attached:

The chokes provide a well filtered low noise output voltage. Smoother and more delicate sound compared to the ordinary lab supply!

Both the high voltage horn driver supply and the  new one besides each other:

The voltage indicators are still missing on the new one, these will be added later.

Next the system will get a crossover in the same style as the one I built for Twogoodear's Gotorama system. Stay tuned!

Best regards

Thomas

Silbatone at the High End fair in Munich

Hi!

In 2010 Silbatone started the tradition of bringing glorious vintage Western Electric sound to the High End fair in Munich. Each year they are bringing a more exciting, more exotic and more vintage set up and repeat to amaze and dazzle the visitors and stirr up the scene.

This year they brought a set up with the WE15A horns.

The horns were driven with WE555 field coil drivers.

Supported by a field coil tweeter, coupled with a cap which is just hanging at the cable:

Some views from different angles:

As in the previous years, this set up drew a lot of people into the room.

Also on demo were two speakers from GIP.

 

The set up was driven by Silbatone amplification:

Note the Kraftwerk LP on the left. This was played a lot. A long with all kinds of music from classical to Black Sabbath which caused a lot of grey haired guys to show their head banging skills.

One of the sources was this uniquely designed turntable from Thomas Schick:

A huge sub with EV30 and Altec 515Bs, designed by JC Morrison supported the horns in the low frequency department:

Joe Roberts (right), Holger Barske (middle) and Thomas Schick (left)

After the show we ended the day with a get together in one of the most beautiful beer gardens in Munich.

Thanks to the Silbatone crowd for bringing this set up and for sharing their passion for such vintage gear.

Best regards

Thomas

Making of a Field Coil Speaker, Part 3: Crossover

Hi!

Finally found some time to continue with the field coil speaker. Since the high voltage field coil supply for the horn driver is finished, the only thing missing to play the horn and woofers together is a crossover.

For a first trial a quick lash up of a crossover was built. Since the speaker is meant to be driven actively with separate amps for bass and mid/treble, the crossover will be placed between preamp and power amps. The crossover is based on the same concept as the one which I already presented here. Low impedance LCR type high and low pass filters.

The coils are some Lundahl LCR RIAA coils wired for 180mH. This network splits the signal from the preamp into the lows which are routed to the bass amp. For the first set up I chose a single ended 6CB5A amp. Slage 1dB/step attenuators are added at the high pass output for adjustment of the horn level to the bass. See close up on the left. The horn driver is driven by a 45 amp. How does it sound? I immediately liked what I heard. Some rough adjustement of the levels and I played record after record. These field coil drivers are capable of an incredible tone. Very realistic and immediate presentation. The 45 amp with 10Y driver really shines at the A2000s with beryllium membrane. Deep bass is a bit lacking still, but that's no surprise with the enclosure which is basically an open baffle. Definitely need to work on that and maybe another woofer for sub bass support.

The Field Coil supply for the horn drivers works beautifully. It induces no noise of it's own which was expected with the three chokes used along with the oil caps for smoothing.

Next up are some measurements of the set up and adjustments to the crossover. Once the crossover is final it will be built into a nice chassis in the style of the modular preamp as presented in resent posts.

But for I mess around with the set up, I will enjoy that tone for a while and oh those sweet voices....

Best regards

Thomas

Making of a Field Coil Speaker, Part 2: FC PSU

Hi!

Part 1 of this series about the development and building of a field coil speaker system showed the first trial for a bass cabinet and the selection of drivers and horns. The Kilimanjaro Series woofers will initially be fed from a lab supply. Later this will be replaced by my own PSU. Today I will show the building of the field coil supply for the A2000 horn drivers which are equipped with high voltage field coils.

The high voltage field coil version was chosen so that the PSU can work with tube rectifiers. The coils can work from about 90-120VDC and need around 300mA each. Quite doable with TV damper tubes as rectifiers.

The 4 photos on the left show the assembly process. Everything starts with the top plate. The first photo shows the plate with switches, connectors and tube sockets mounted. Then the plate is fixed into a rig which eases further assembly. In the second and third photo, capacitors and the power transfromer are mounted and wired. 6CG3 TV dampers are used due to their high current capability. The transformer is the largest from my own mains transformer series. Since two separate power supplies for the drivers would require two separate PSUs, it was decided to feed the two A2000s in series. Doubling the voltage in a tube power supply is almost no additional effort, if the power transformer can deliver the voltage. Doubling the current would require two separate supplies since 600mA is beyond the capability of the 6CG3 and would require big chokes for filtering. The configuration is a full wave bridge with 4 TV dampers feeding a LCLCLC choke input supply. The chokes are Lundahl LL1638/4Hy which can handle 400mA DC. The last capacitor is split into two separate ones for decoupling of the voltage of each driver.  The transformer has various taps to allow secondary voltage increments in 25V steps. In addition the primary has taps for 220, 230 and 240V. These taps have been used to provide adjustment in 7 individual 5% steps. With two more switches the filter chain can be switched between choke input or cap input. Two different sizes are selectable for the input capacitor: 1uF and 4uF. The 4th photo shows the finished PSU with the chokes added and wired. Everything is placed in the wooden frame. Two vintage panel meters are inserted in the front to monitor voltage and current. The voltage meter measures the entire voltage across both coils. The capacitors and mains transformer are hidden unter covers which are painted with a white metallic effect varnish.

The switch matrix for fine adjustment:

The backside with switches and connectors. Two different connectors are wired in parallel for the field coil voltage. 2 sets of banana jacks and an amphenol screw type terminal which provides connection for both drivers:

The two handles are convenient for moving the PSU around since it is quite heavy.

The power supply in operation:

Voltage is set for 90V per driver, 180V total. 300mA current.

The power supply operates nicely and stable. Voltage adjustment can be done while the supply is on. No need to power down for switching between the taps. This is easier on the TV dampers since one of the main factors determining liefetime is cycling of the heaters. Not that it would be a big issue since these rectifiers are very cheap.

The 6CG3 seems to be the perfect choice for such a supply. I'm using it since quite a while in the power supply of 211 monoblocks and it works flawless there in a voltage doubler circuit which is quite demanding. I expect them to last many years in the field coil PSU. No special precautions were necessary with regard to heater-cathode voltage. The heaters are simply referenced to ground. Since the 6CG3 draws a bit of heater current (2.1A) two heater windings are used. Two tubes share one winding. The photo on the right shows a nice close up of a 6CG3 in operation. There are other TV dampers who could be used for this purpose as well. For example 6CJ3 or EY500. The latter is probably easier to be found with heaters for series string operation. That is the PY500. The american designations for the these tubes are 6EC4 and 42EC4.

Before listening can start, the speaker needs a crossover. This will be a active set up with a passive crossover placed between the line stage and the separate power amplifiers for horn drivers and woofers. The next part will show the initial version of this crossover. Stay tuned!

Best regards

Thomas

Making of a Field Coil Speaker, Part 1: First Trials

Hi!

This weekend I finally had some time to start experiments with my Kilimanjaro Series field coil drivers. For these I prepared a new listening room which I will use to demo my gear. Of course this room needs an adequate speaker.

I have various horns in my collection. One of them is an Iwata horn made of die casted aluminum. This is one pair of a few which got custom made by a group of people in Berlin. One of the members of the Munich Triode Mafia bought a pair years ago. I found them in his attic and we set up a deal. Unfortunately the horns were poorly painted in a horrible blue. So I brought them to a car paint shop where they got sandblasted and repainted in a special color which is used by Mercedes. the color is called 'designo graphite green'.

I used these horns a long time in my speaker installation in Munich, which is now dismatled:

In this system the Iwatas replaced TAD4001 horns which I had before. First I used them with TAD4001 drivers. After I tried Wolf von Langa's A288 field coil drivers, the TADs went out and I was bitten by the field coil virus. The horns were used with various combinations of Altec drivers for the lower mids and bass: 414As, 515Bs and 416As. During the time of the High End fair 2010 Wolf and myself set up a demo at my place for which we replaced some of the Altec woofers against his A515 field coils. After that session it was clear to me that one day I need to have a full field coil speaker system.

Initially I planned to have two woofers per side, A416s and A515. For the first trial I got simple open baffles made from multiplex wood for just a single woofer. Since my new listening room is fairly small I will initially go with with one per side. If the A515 needs some sub bass support, I will add the A416, kicking in at low frequency.

A close up of the horn driver mounted to the Iwata horn:

The horn drivers have a high voltage field coil. They will get a tube rectified and choke filtered power supply which still needs to be built. The speaker will be set up as an active system with separate amps for bass and horn driver and later also for a tweeter if needed. Frequencies will be divided passively between linestage and power amps. The system will get a LCR type crossover.

For a first listening the woofer had to be operated full range with the field coil powered from a lab PSU since crossover and high voltage field coil PSU still need to be built. Of course this is no meaningful listening test but it already gave an hint of the incredible tone these field coil woofers are capable of.

I also consider to give Wolf's enclosures a try if they fit into the room. Once the final enclosure is decided upon it will be made in some nicer wood.

Stay tuned for updates as the speaker development progresses.

Best regards

Thomas