Altec 756B + 32C + 806 + 23744 = mini 757

The WE756A is the middle child in the Western Electric series of wide range drivers introduced in the late 40s.

I've seen and heard a couple of WE/Altec 728Bs + a dozen or so pairs of 755As, but I've never heard a WE756A and have only seen one in the metal at a radio show many years ago. Although still quite scarce, its Altec 756B brother isn't quite as elusive.

Back: Blonde + Mahogany Altec Melodist 700A
Front L-R : WE728B, Altec 755A/pr. + Altec 756B

The few Altec 756Bs I've encountered all came out of the Altec Melodist 700A. It's a compact bass reflex speaker system loaded with the 756B, supplemented on top by a 3000A horn tweeter via an N3000B crossover. The 700A belonged to the Melodist monaural hifi system line, which Altec targeted at apartment dwellers in big cities of midcentury America.

 Subsequently, the 756B was replaced by an 8" Altec 401A and was re-designated as the Melodist 700B. With the introduction of stereo for the mainstream market in 1958, the Altec Melodist line quietly faded into oblivion.

 If found in good condition, the Altec Melodist 700A is a fine looking midcentury modern artifact! Unfortunately, the < 1.5 cf ported box doesn't allow the 756B to shine sonically, IMHO. Since it shares similar proportions to its more successful contemporaries like the Acoustic Research AR-1 and the Jensen Duette, the cabinet design may have been dictated by market positioning rather than sound engineering.

My once-in-a-lifetime lucky find 700A above has lived a hard life. The lower front edge of the cabinet was missing while the sweet and airy but very fragile 3000A horn tweeter element had been replaced by a tiny ferrite magnet dome tweeter.😏 A "mod" that has been circulating in the internet, so watch out.  

 

Fortunately, the 756B is very well preserved. If memory serves me right, the WE756A frame is more substantial than the Altec 756B. That’s probably the reason why the back handles were omitted in the Altec. The 756B has an 8 ohm voice coil, while the WE756A is 4 ohms.

J-Rob's Altec 756B at 
Capital Audio Fest 2016

Joe Roberts has already done a great job of describing the sonic qualities and proper implementation of the Altec 756B in his (Geekstar) "My big ten inch --Altec 756B" post at the Altec User's Board. He also gave insight on the shifting Asian market for vintage Western Electric and Altec gear. A guaranteed fun and informative read!

Since I don't have Joe's networking skills, I resigned myself to the reality that my Altec 756B will be the main speaker of my monophonic hi-fi set up, just as Altec intended.

Click for a videoclip

Meanwhile, I repurposed (sealed) a Heathkit AS10 (almost 2 cf) cabinet to familiarize myself with the 756B. I listened to it as a wide range driver with and without top end assistance from either a 32A/802/34852 + an XO based on this schematic or 3000H with an L-Pad + 0.5 uf - 1 uf paper in oil cap. The simplest XO I used was a 0.22uf paper in oil cap in series with the + terminal of the 3000H, no L-pad needed. That also sounded good, albeit, with slightly less sparkle.   

JE Labs mini 757
inspired by the Western Electric 757A

After extensive listening in wide range mode, I determined that a mono hifi set up will benefit from a wider baffle + the dispersion pattern of the Western Electric-derived 32 horn. So I sketched a slant front ~ 2.5 cf infinite baffle that has a provision for an Altec 32C horn + 802 driver and sent it to John Piro of Hommage Audio.

728B vs. 756B

As expected, the 756B is more extended at the top end than the 728B with almost, but not quite, equal bass extension. However, music through the 728B held my attention appreciably longer without my reaching for a clip-lead to fill in the top octaves with the 32/802 horn/driver for more harmonic overtones above 5 kHz. 

RTA = Altec 756B in a ~ 2.5 cf infinite baffle 

I confirmed this during one of my shop talks with J-Rob, who also found it more rewarding to listen to 728Bs in wide range mode than to his 756Bs. It makes me wonder if the 756B and its WE756A brother were designed with a middle-child syndrome gene in their sonic DNA.🤔

After many years of collecting Altec 1" compression drivers, I've only landed a single Altec 23744 "light" aluminum diaphragm, which was fitted to an 806 motor that was used in the Altec 9849 monitor speaker.

Things started to crystalize when my friend Dave V. aka Salectric,🙏 sent me his spare .085 mH choke. It was a proprietary part found in the EQ circuit of the Altec 9849 crossover, which is an 8 ohm speaker system. This EQ circuit shapes and boosts the response of the 32/806 horn/driver combo. Incidentally, Dave's "Last PAS" articles written for The Audio Amateur contributed to my 80s Dynaco hacking activities.

RTA = Altec 32C + 806 + 23744

 The 4 uf paper in oil capacitor serves as a first order high pass filter hinged around 5 kHz with a gentle 6dB/octave slope, while the variable 8 ohm L-pad shapes and controls upper frequency overtones to taste. 

inside the mini 757

John P did a great job of building a very rigid cabinet, which saved me the time and trouble of having to experiment with damping. I just lined the interior panels with Kimpak and I was ready to listen.

RTA = JE Labs mini 757

This project transpired as an opportune moment to assemble all the singleton Altecs from my collection - 756B + 32C + 806 + 23744 - into a formidable monaural hifi speaker system.😊

JE Labs mini 757

My ears hear close to half an octave of bass extension from the mini 757 compared to the 755A in a Silbatone or 618 cabinet. Due to its greater efficiency, it plays louder while dynamics at micro and macro levels are less compressed. The larger cone area of the 756B + wide baffle + 90° horizontal x 60° vertical dispersion of the 32C horn, portray a bigger sense of scale. All of these were achieved without compromising the midrange realism I enjoy from my beloved 755A. 

However, the Altec 753C is perceptibly more efficient, offers at least an octave lower of extension with more authority. It also produces higher SPLs. 

Alas, we can't defy the physics of sound...

JE Labs monophonic hifi

...so I focused on the aesthetics by spicing it up with a touch of Charles Eames and Dieter Rams! 😉

Hi-Fi for the Deck: Rpi3B >TDA1543x4 DAC > Simple Triode SE6V6 amp > EV Sonocaster

Spring and Fall are the best seasons to enjoy food and drinks on our deck. To complement the beautiful atmosphere, I assembled an e-z to set up and dismantle hifi system!

Music Source

This stack consists of a Raspberry Pi 3B loaded with Volumio music player/streamer tethered to a Signstek USB to SPDiF converter which connects to a Muse TDA1543x4 Non-OverSampling DAC.

Volumio offers a wide choice of radio stations streaming MP3 files up to 320 Kbps. The Radio Paradise channel has even started broadcasting FLAC files. 👍

Amplifier

In the late 80s, I built my first amplifier from scratch using transformers from a cosmetically challenged Dyna SCA35. I used this paraphase circuit from the Dynaco Transformer Catalog with a 6SL7 driving a pair of push-pull 6V6s. Musically, I preferred this amp to my then highly modified Dyna ST70 and pair of MKIVs.

with 6F6Gs courtesy of John Piro

Since I always had reservations about the 1626 triode's musical abilities, I converted the JEL Darling Style amp to use triode connected 6V6s. Wow!👍

!!!WARNING!!! 

The voltages in this circuit are potentially lethal! Build at your own risk!

Input sensitivity = 0.3V, no need for a preamp
This amp also does a good job of driving my collection of orthodynamic headphones via adapter.

Triode connected 6V6s mimic directly heated triodes much better! 🎻🎸

Speakers

This pair of Electro-Voice Sonocasters came from the flea market. I guesstimate the sensitivity to be in the mid 90s dB @ 1W @ 1M. Driven by 1.4 triode watts per channel from the SE6V6 amp, I sure won't be annoying the neighbors. 🤣

The 8" drivers are unmarked but look very much like MC-8s - not quite an Altec 755C or Pioneer PIM8L in terms of refinement or realism, but not too shabby either + a lot more rugged!

Happy Listening!🍻

Marcel Breuer Designed House + Altec 604C + Infinite Baffle

  

This beautiful mid century modern home aka the Snower residence was designed by Bauhaus architect Marcel Breuer and posted by midcenturyhome, whose finely curated photostream I follow on Instagram.

Aside from my interest in mid century modern architecture, the Altec 604C mounted prominently in the living room caught my eye.😄

I've also seen a Fisher 50C preamp (bottom) at FLW's Fallingwater. Unfortunately, interior photography was prohibited there when I last visited. 😞 

The Snower house + hifi installation was already brought to my attention in the comment section of architects, music and hifi  by a blog visitor many years ago. Thank you!

from Dwell.com

More Infinite Baffle Installations

I blogged about this installation before, but this picture offers another perspective of the 2-way horn speaker system installed in Case Study House #9 designed for John Entenza by Charles and Ray Eames and Eero Saarinen.

Scans from How to Build Speaker Enclosures

An office stereo hifi

John Hilliard's home hifi system

Hi-Fi system details

I'm pretty sure all these wall mounted speaker systems were formidable music reproducers! However, ever since soundstaging and imaging took precedence over sound quality, infinite baffle loading fell out of favor. 😔

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.

JP's Western Electric WE757A Remake

 

Those were the words of the late Walt Bender in Part II of his Olden Golden Components article in Issue 51 of The Absolute Sound (TAS) in the Winter of 1988. This was my first exposure to Western Electric audio equipment. I eagerly awaited TAS's promised feature of Walt's Western Electric-based audio system but that never materialized. I let my TAS subscription lapse and replaced it with Glass Audio, Sound Practices and Vacuum Tube Valley. 

My only encounter with an original WE757A was a single unit being tested on the tailgate of a Honda Civic hatchback at a ham fest in the early 90s. Keep in mind that this speaker system predates the stereo era by at least 10 years, thus, they were never available in stereo pairs.

In this day and age, the only way a mere mortal can experience a Western Electric WE757A speaker system is to build one using as many of the original parts as one can gather.

This is exactly what John Piro did. He combined a WE/Altec 728B driver with a slightly dented dust cap + the botched up KS12027 he expertly repaired to properly mount an Altec 802D compression driver. 

Then he painstakingly cloned and crafted a WE757A cabinet to house these components. Soon after the speaker system was completed, we met at the Kutztown Fall 2019 Radio Show and he entrusted the evaluation of this speaker system to me.

In keeping with JE Labs methods, I started by evaluating the drivers individually and then compared the JP WE757A to my Altec 753C. I was fortunate to have had lots of time to dissect and enjoy the JP WE757A. Thanks, JP!

WE/Altec 728B

When I visited J-Rob in the summer of 2018, I spent quality time listening to his pair of WE728Bs while talking shop. The very rich harmonic overtones they produce captured my attention just like a fine violin does.

The smaller Altec decal is pasted over the larger Western Electric original. 
JP surmises that this unit started life as a WE728B which got damaged early on 
and was re-coned by Altec using an original WE re-cone kit. 

Technically speaking, the WE/Altec 728B is neither a woofer nor a full-range. It's a wide-range speaker. The RTA trace shows a seven octave range, which pretty much mirrors the original 60-10,000 kHz specification. 

WE/Altec 728B

The 728B tonal balance is very much like its smaller brother, the 755A, with an additional octave of extension in the bass and about an octave less extension in the highs. This and the Altec 414A are the only 12"-15" drivers that I've heard (so far) which don't break up in the 1-2kHz range resulting in shouty female vocals, amongst other nasties.

Dented dustcap

From the upper bass to upper midrange, the 728B has the J-Rob  coined "snap," which it shares with its 755A and 756B siblings. IMHO, these permanent magnet drivers are unparalleled to this day for their life-like midrange and ability to convey a three dimensional realism. OK, perhaps the Western Electric and GIP field coil drivers are even better but as I said earlier, this article is for mere mortals.😉

WE754A vs. WE728B

In the midst of my evaluations, I exchanged private messages with another Western Electric aficionado who's had the rare 

opportunity to compare the WE754A and WE728B drivers. He is currently assembling a pair of WE757As.

 

 With his permission, I'm sharing his valuable listening notes. Thanks, Jonas!

Just wanted to let you know what’s going on with my 757 style speakers. I was blessed to find a WE 728B in an old console in pristine condition. I was able to compare the 754A and the 728B and I liked the 728B much more. The 754A has perhaps a bit more lows but a thicker lower midrange, and less detail and dynamics, and not as smooth as 728B. Compared to other speakers they were very smooth, but when I heard the 728B with a complete absence of grain or distortion, the difference was apparent. They sounded great on things like Gerry Mulligans Baritone Sax on Night Lights. The 754A’s are made for that sort of thing and I think those who love thick midrange would really enjoy them. But they also didn’t have quite as much highs, at least to my ears. I ran them full range so it would have been nice to try out different crossovers to see if the 754A would have been better with a lower cut off. Perhaps so. 

Anyway, I sold both 754A speakers to a young gentleman from NYC who's uncle is a big WE collector from Korea and it was very cool to meet such an WE enthusiast. The uncle came by to listen to them. He apparently has original 757 speakers among many others and said he uses PX-25 tube LS in his amp. With that money I found a second 728B in similar shape to my other, and they are now installed in the John Piro cabinets. 

I do wonder about the differences of the 754A and 728B in the intended applications. The 754A came before the 728B. There is some a lot of talk about it (a bit of ad copy hyperbole but very interesting still) in this issue of Oscillator Magazine, which was put out by Western Electric. Amazing that they put that much time and effort into a trade publication, and to think of what went into the design of these. 

It seems they created the 728B as an updated or “improved” version of their 754A. What I’ve heard is that the 754A has a copper wound voice coil while the 728B had aluminum. Also there’s the obvious difference in magnet structure and power handling.

They sure sound very different. The imaging and spatial depth is far better in the 728B, at least in these cabinets. The 754A seemed to beam more. Of course the published specs aren’t much different nor are the dispersion characteristics listed in the WE specs, but the 754A seemed to beam more in my cabinets. It’s almost like the 728B strip out any unnecessary frequencies and things have a nice space and clarity while the thick midrange of the 754A brought certain instruments out front at the expense of this clarity and separation of instruments. At least to my ears.

So, part of me wonders if they had just made the theater speakers earlier, designed using the 754A, if they were just trying to use up stock, or if there was a specific reason to use them instead? The 754A is slightly more efficient by 1db, and it seems to play a bit lower and have more low range frequency happening even if they go to the same rated frequency range according to their literature. (it was hard to be sure if the 754A went lower, but the lows were more filled out).

Perhaps this increase in lows, even at the expense of clarity and spacial clarity between instruments, was the reason they were used in the theater amps.

Regardless. It seems that WE put considerable thought into the new 728B. I prefer the 728B a lot myself. I wish you could compare them and do a write up! I really look forward to your future blog posts. 

Best,

Jonas Baker

WE/Altec 728B vs. Altec 414A

Altec 414A

The 414A has finally met its superior adversary. In direct comparison with the 728B, the sharp roll off around 4kHz makes the 414A sound less snappy and comparatively muffled.

Altec 414A

The main asset of the 414A over the 728B is a little more than half an octave of extension in the bass range and a couple of dB more in efficiency. In spite of the 728B's obvious superiority, my admiration for the 414A remains, much like my fondness for the 755C.😉

KS12027 vs. Altec 32C

KS12027 horn

KS12027 + Altec 802D + 20275 diaphragm

Since my capsule review last year, I learned more about the nature of the KS12027 horn. The KS12027 surpasses the 32C and Azzolina KS12024 in presenting distinctive harmonic overtones from lower frequency instruments like cellos, basses and, believe it or not, even from the tympani. Vocals and acoustic instruments are uncannily real and three dimensional, just as they are with the 728B, albeit scaled to small format horn proportions. 

When I compared the Altec 32C to the KS12024,  I noted a distinctive "in your room" presence with the latter. This quality is even more prominent in the KS12027, which is another multi-cell type horn.

 

Altec 32C horn

Altec 32C + 802D + 20275 diaphragm

Comparatively, the Altec 32C sounds more laid back than the KS12027. Vocals and lower frequency instruments like cellos and basses had less of the life-like harmonic overtones rendered by the KS12027. High frequency transient speed is also slightly slower. Thus, brushed cymbals and high hat tend to have a splashy quality instead of lightning fast attack and decay coming out of the KS12027.

Although the 32C has the wispy airiness at the extreme top end which the KS12027 wasn't able to match, the addition of the Altec 3000H was not as successful as my previous experiment with the Azzolina KS12024. I think the 3000H can't quite match the transient speed of the KS12027.

I've said it before and would like to emphasize further that the KS12027 is the most natural and real sounding small format horn I've listened to. 

Simple Crossover

Since I don't have access to the original WE702A crossover schematic of the WE757A, I made a simple high-pass 1st order crossover hinged at 5kHz and ran the 728B unobstructed. Definitely not optimized, but good enough for me to enjoy the speaker system.

Altec 753C vs. JP's WE757A

All my listening was conducted using the je2a3 mono integrated amp with Hashimoto H203S output transformer, fed by the following sources: Gates CB77/Gray 108B/GE RPX and Neat P58H/Calrad SV16/DL102, Magnavox CDB650 transport > Arcam Delta Black Box DAC.

Altec 753C

The Altec 753C is very lush and romantic. It gives a middle of the hall presentation compared to JP's WE757A. Its only advantages over JP's WE757A are: almost an octave more bass extension (albeit with less definition), a couple dB more of efficiency and the wispy airiness in the very extreme top end noted earlier in the 32C/802D pairing.

JP/WE757A

Typically, components with similar qualities don't complement each other because their virtues cancel out. However, in this particular case, the WE/Altec 728B + KS12027/802D was an utterly cohesive and coherent blend.

JP's WE757A sounded neutral and more analytic in a very musical way. Transients come across crystal clear and clean. Dynamic nuances at macro and micro levels are also much better conveyed. Even if the music is presented closer to the stage with greater detail and resolution, I didn't experience long term fatigue. 

In spite of the slightly less bass extension vs. the Altec 753C, definition was better. Due to a tad less efficiency, it can benefit from slightly more power. Perhaps an SE300B amp would've improved bass extension and dynamics further.

The sense of realism from its three dimensional midrange is a result of the life-like harmonic overtones produced by the 728B + KS12027/802D pairing.

The Altec 753C set a very high musical standard but JP's WE757A cabinet remake + Altec 728B + KS12027 horn + Altec 802D is more organic, finer and nobler in stature. It brought me closer to the music! 

Now I'm asking myself, how much better would it be with the original WE713C compression driver and the optimized WE702A crossover?

The WE755A, WE756A, WE754A, WE728B, WE753C, WE757A, etc. came from an era when America was at the height of its industrial might. The amount of R&D that went into these transducers will never be equalled. Sadly, these are more appreciated in Asia and Europe.

To add insult to injury, many American audio hobbyists even sneer at these foreigners who pay top dollar for these American-made classics. This gives credence to the saying, "no one is a prophet in their own land."