Silbatone Box Adventures

from Western Electric Oscillator July 1947

Whether it's an open baffle as conceived by G.A. Briggs or an enclosed box like the Western Electric utility boxes above, I've always been an advocate for a wide baffle design. The wide frontal area serves as an acoustic reflector that helps propagate sound toward the listener instead of escaping to the sides and back. Somehow the wide baffle, whether open or closed, always makes reproduced music sound more alive to my ears!

A notable exception is the narrow front baffle Silbatone box designed by Dr. Stefano Bae for the Western Electric/Altec 755A. Since I uploaded the cabinet project under the auspices of Joe Roberts, it has garnered a following amongst DIYers who've reported successful results mounting other 8' drivers like the Altec 755C, 755E and the Lafayette SK98/Pioneer PIM8L. 

I finally got a chance to mount and listen to my 755Cs and PIM8Ls + other 8" wide band drivers. Hopefully, this article will encourage readers to DIY this mini-monitor sized box because it really offers a lot of musical pleasure per cubic inch!

To recap, let's start with the...

Home Brewer: Silbatone 755 Cabinet DIYers Club

Left = JE Labs clone (by John Piro)
Right = J-Rob's Silbatone original 

"The cabinets were designed by genius Silbatone engineer Dr. Stefano Bae as a group project for the Silbatone-sponsored DIY/Western Electric forum in South Korea. 100 pairs were quickly sold out, immediately driving up the world price for 755As. The original uses Silbatone's custom silver litz wire, which is said to be an essential ingredient of the original recipe, and top shelf WBT connectors.

Over the years Silbatone designed and made literally dozens of experimental boxes, including back horns for up to four (755A) drivers per side. This was probably the most successful, although rather modest.

My analysis of this untuned little cabinet is that it falls under the 'small box with a hole in it' design paradigm."

Joe Roberts 

May 17, 2019

After I uploaded the Silbatone cabinet DIY info, I've received numerous inquiries about what drivers to use on this cabinet. Since it's impossible for me to try all the 8" drivers ever made, I thought it was best to let my readers chime in with their creations.

Altec 755As in Manila

Tango MCT999 MC transformer,
JE Labs 5691 passive EQ RIAA phono + 76 > Tango NP216N line stage, 
JE Labs SE2A3 with Magnequest TFA204 OPTs (on the floor)

Nonong is the only high school classmate and friend I remained in contact with after leaving Manila many moons ago. He coined SETUP (Single Ended Triode Users of the Philippines) back in the '90s and was one of the three pioneers listening to idler driven turntables, high mass tonearms, SPU cartridges + transformers, DIY preamps and SET amps driving high efficiency speakers.

Garrard 301 + Ikeda IT407 + SPU Meister Silver
JE Labs SE300B deluxe mono blocks with Tamura F7002s 
on copper chassis

His cherished pair of Altec 755As have been mounted on open baffles since the mid '90s. But as soon as he saw the Silbatone cabinet plan, he had the cabinets built in no time.

Altec 755As in the USA

Nate Grindheim aka Redboy in Audiokarma and HiFi Haven is an avid DIYer. You'll find his meticulously crafted MC step up transformers and amps in those aforementioned audio forums as well as in his Flickr stream.

Nate says:

"My buddy Gary (aka ejfud) built the cabinets for me. He knew I had the drivers and got tired of waiting around for me to build something for them, so he took the initiative to knock a pair together for me. He's a good friend to have around.

These things are really wonderful. They have that amazing Tone (with a capital "T"!) that I'm after, and the sound... it's just right, and good. They make music.

I am excited to get some proper amplification for them. There's a pair of 6L6 IPC amps here with Peerless iron that I think will be a great match, but I still need to overhaul them."

Altec 755C in Manila

Ben C recently retired from banking so he can focus his energy on his DIY audio passion. He's been stuck in Toronto since the Covid 19 lockdown and is itching to return home to finish his other audio projects.

Garrard 401 + RMG309 + FR64S + SPU Aniversary,
DIY preamp and SET amps

 I'm hoping that he'll drop by before he heads back to Manila when this is all over.

Altec 755E + JBL 075 in Manila

This bespoke cabinet is Joey's interpretation of the Silbatone executed in the Harana Audio Workshop. 

Harana Audio is also the official representative of Shinichi Suzuki and his Western Electric inspired G.I.P. Laboratory field coil drivers in the Philippines.

Lafayette SK98/Pioneer PIM8L in the USA

I've featured this driver and cabinet in a full-length profile of John Piro's creations. But it's worth reiterating a non Altec 755 driver successfully used in the Silbatone cabinet.

If you want your DIY Silbatone cabinet project added to this exclusive club 😉, please leave a comment with your email address. I will reply to you directly.

A visit to J-Rob's and the Silbatone 755A box by Dr. Stefano Bae

OB/755A

Despite the fact that Joe Roberts and I both revere the 755A, he never thought highly of my open baffle set-up. To this day, I'm still baffled as to why he featured my home-brewer article in Sound Practices. 😉 I enjoy the engulfing planar-like airiness of the 755A/OB combo which Joe finds lifeless, boring and lacking in snap. 

OB + 755A

Could the dip in this RTA trace be indicating a lack of snap? 😜

Custom-built Altec 618 + 755A

J-Rob custom 618 cabinet

  Back in the mid-90s, I owned a pair of original Altec 618s. Those sounded boxy and colored, perhaps due to their lightweight construction. So I traded them for a pair of early sand casted 811 horns...😧 Oh well, live and learn. 😁

When my friend Chong gave me a pair of well braced vintage DIY 618 boxes (allegedly built by an ex-WE engineer and used to house a pair of WE755As), I understood the snap that ticked the Joe-man.

ex-J-Rob Altec 618 + 755A

This is the nicest and most modern looking RTA trace in this survey! Loaded with Altec 755As, the sound is snappy and dynamic while retaining that warm and realistic sheen in the midrange, which evades most speakers marketed in the past 50 years. Although some listeners may still find that quality a vintage coloration...

A visit to J-Rob's

People don't always have to agree to remain friends

Case in point: Joe seems to prefer the Japanese 755 - Lafayette SK98/Hamlin/Pioneer PIM8L - over the ferrite 755C. However, if push comes to shove, I'd take the 755C over the various permutations of the PIM8/20L even if I played a role in reintroducing its virtues to the world. Maybe it's just my sentimental attachment to the 755Cs since they were my very first high-efficiency drivers?

J-Rob sez, "I shouldn't even be talking to you since you like 755Cs." 😆

When I visited Joe in the summer of 2018, he had a pair of 4 cubic foot WE753A look-alike cabs that house Western Electric WE728Bs driven by a spruced up Dyna SCA35 which was recently replaced by a J-Rob cloned Peerless A100 PP 6A5G amp built during the Sound Practices era. Signal source is a Mac Mini>Tidal>Audirvana>Wavelength Audio Brick DAC.

Despite the natural high frequency roll off of the 12" WE728B, it sounded very full-range because of its rich overtones. That is, overtones as musicians use it to describe musical instruments. A high quality violin, piano, or any musical instrument for that matter, possesses rich overtones and this has nothing to do with high frequency extension. Even FFT analyses have failed to identify why del Gesus and Strads sound harmonically richer and have greater carrying power in a good acoustic space compared to a painstakingly crafted modern violin.

I was looking forward to hearing the Silbatone SE300B amp on the floor but Joe hasn't gotten around to re-wiring it for 120V, and also to LPs, but the Gates CB500 was waiting for a resurfaced idler wheel. Then he showed me his next project - Klangfilm horn repros (center background) + Altec and JBL large format compression drivers.

Finally, I was introduced to the pair of Altec 755As perched on top of the WE753C-like cabs. I was quite impressed with the sounds emanating from the 755As!

This 755A/box combo was featured in the Silbatone exhibit at the Munich High-End 2018 Show. Prior to that, Joe spoke fondly about the box and gave DIY hints in this Audiokarma thread. I was hoping that he'd be inspired to update his Junkyard Jukebox blog for a formal presentation of this cabinet design before he went on a sabbatical from the internet.

Since there's no sign that he'll be back anytime soon, with his permission, I took it upon myself to write about this 755A cabinet breakthrough.

Silbatone/Dr. Bae WE/Altec 755A box plan
Copyright Silbatone Acoustics

I re-drew the box plan based on a quick sketch Joe uploaded in the Audiokarma thread. Please note that this cabinet plan is published solely for the Audio/DIY community as a public service of Silbatone Acoustics. 

Under no circumstances should this be used for commercial purposes! 

Let's see if that works...truth be told, I am well aware that there have been a few enterprising individuals who have benefitted commercially from projects published in this blog. So I'm not holding my breath.

John Piro Clone Build
Interior walls + back lined with two layers of Kimpak

I sent the drawing to my buddy John Piro shortly after my Altec 753C cabinets were delivered.

Can anyone distinguish JP's clone from the original Silbatone box? 

Dr. Bae designed Silbatone box + 755A

J-Rob comments:

"The cabinets were designed by genius Silbatone engineer Dr. Stefano Bae as a group project for the Silbatone-sponsored DIY/Western Electric forum in South Korea. 100 pairs were quickly sold out, immediately driving up the world price for 755As. The original uses Silbatone's custom silver litz wire, which is said to be an essential ingredient of the original recipe, and top shelf WBT connectors.

Over the years Silbatone designed and made literally dozens of experimental boxes, including back horns for up to four (755A) drivers per side. This was probably the most successful, although rather modest.

My analysis of this untuned little cabinet is that it falls under the 'small box with a hole in it' design paradigm."

Unlike before when I felt the need for at least SE300B power to make the OB/755A sing, now I'm enjoying near-field sounds from my JP cloned Silbatone/Dr. Bae boxes + Altec 755As driven by an SE46 amp with tiny Noguchi FM6WS Finemet OPTs.

The SE2A3dx which normally drives the Altec 753Cs in the main listening area had no trouble driving the Altec 755As in Silbatone boxes to moderately high SPL levels.

 Even without the silver litz wire and high tech WBT connectors, I heard all the virtues of the slant 618 box + open baffle combined = detail, snap, macro and micro dynamics from the 618 box + airiness and lack of vintage boxy colorations from the open baffle.

The Dr. Bae/Silbatone cabinet transported the 70 year old 755A design to the 21st century in a monitor-sized package!