General Electric A1-400 Speaker

It was past lunch, so I took one last sweep at the Kutztown Spring 2021 radio meet before heading home. That's when I noticed this cabinet with a familiar looking metal-grilled driver partially hidden behind a huge pile of equipment. Without haggling, I handed a couple of ATM bills to the seller and we shook hands.

As soon as I got home I went through my Japanese audio magazine shelf and pulled this Stereo Sound Special Issue about Vintage Speaker Units, published in 2002.

Not exactly the General Electric A1-401 featured in the magazine but the slightly earlier A1-400. Pretty good memory for someone pushing 60, huh? 😉

GE A1-400 specs

As stated in the spec sheet, the perforated metal grill functions as a mechanical roll off filter for the 12" driver and the non-polarized wax and paper capacitor filters frequencies below 1800 Hz from reaching the 2 3/4" cone tweeter.

I also recognized this period correct DIY tuned pipe enclosure designed for corner placement. It was built based on an article published in the May 1955 issue of Audio (go to page 18), authored by Norman H. Bates. 

BTW, AFAIK, he's not related to the lead character in Hitchcock's thriller. 🤣

Vocals are nicely rendered! The transition between the low and high frequency drivers is very coherent, as to be expected between two paper coned transducers. If I were forced to split hairs, I hear a tinge of nasal coloration in the lower region of male vocals, which I never notice with any of my Altec speakers. 

Musical instruments and percussion are also well reproduced! Bass extension and definition of the A1-400 in the tuned pipe corner cabinet is at par with the Altec 756B in a 2.5 cf box, if not a couple of Hz more extended. Top end overtones are silky smooth and airy. Even if this cone tweeter lacks the ultimate transient speed and shimmer of a fine horn/compression driver combination, it's probably the finest I've ever heard!

I guesstimate its sensitivity to be in the high 90s/W/M because it'll boogie, driven by the 1250 mW SE triode connected 46 or 1500 mW SE10 amp. Although I can also listen to my Altec mini 757 with those aforementioned amps at respectable SPLs, it needs at least an SE2A3 for full dimensional monaural listening pleasure. 

Kudos to Mr. Bates' corner loaded tuned pipe cabinet for the aforementioned impressive bass performance and my perceived easy-to-drive/high sensitivity nature of this speaker system. Kids, this enclosure was designed during the slide rule era!👍

Now I'm inspired to pursue my 285mW SE112A mono amp project.😊

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I really enjoy this speaker with a GE RPX or VRII phono cartridge tracing Atomic/Space Age/Exotica Lounge/Bachelor Pad mono LPs from the 50s by the likes of Martin Denny, Arthur Lyman, Walter Wanderley, etc. 

After 21 years of hunting, I finally got a satisfying taste of the GE co-ax. I've seen this on eBay between $150-175, which I believe is a fair price for a unit with intact cones and no voice coil rubbing. A couple of my Instagram contacts even expressed fondness and admiration for this speaker when they saw a glimpse of it in my posts!

I now regret leaving my RCA 501-S1 in the attic 😔 because it would have made for a very interesting shootout. If I can trust my sonic memory though, the RCA didn't have the nasal coloration in the lower midrange I noted earlier. OTOH, the top end of the RCA could be deemed more reticent or refined depending on the listener's taste. 

I debated whether to refinish the cabinet
but the patina grew on me.😊

In the context of my monaural hi-fi system, it shall remain second only to the Altec mini 757 because when I played a young Sinatra LP for my buddy Ding, he initially thought it was Bing Crosby.😄 Sinatra only sounds like Sinatra LIVE or on an ALTEC!👍😎

Let's see what the gentlemen at Stereo Sound thought of its younger A1-401 brother two decades ago...

The scan below is from Stereo Sound Vintage Analog 2, 2014

I can drink to all that!🍻

Warming up the Denon DL102

Ever since I acquired a Denon DL102 for my first dedicated mono hifi set up, I found it sounding rather distant and a bit frosty compared to the GE RPX and VRII. 

Since Denon recommends a 1000 ohm load for flattest response, I tried soldering a 1k ohm resistor in parallel with the 47k input (47,000 x 1000/47000 + 1000  = 980 ohms) of my variable EQ phono preamp. Unfortunately, the sound became even more glacial.

I could have been basking in warmth by now (without losing stereo LP compatibility) if I saved up for an Ortofon SPU mono but the DL102 body fits a Gray Research or clone tonearm slide perfectly. Besides, I would rather add more stereo SPUs to my cache.😉

Since I've been using 1:1 line transformers as digital sound processing devices at the output of my CD players for ages, I decided to try the same trick by wiring the Altec 15356 and UTC A20 with a mild step up - 150:600 and 125:500, respectively. Even if both primaries reflected significantly less than Denon's recommended 1000 ohms, what I heard encouraged me to continue to experiment. 

Although I'm not anal retentive about impedance matching, I was curious too see if the sound would improve by using transformers that reflect at least twice the 240 ohm internal impedance of the Denon DL102. I managed to procure the three transformers above: to the left is allegedly a Tamura 600:3k, then I tapped the McMartin MT-4's 10k:60k winding, and at the center is a permalloy 10k:40k, which sells for about $50/shipped from Chinese sellers on AliExpress and eBay. 

 

In the context of my mono hifi set up, the McMartin MT-4 was a bit too warm for my taste. However, even if I upload videos merely for the visual spectacle, the permalloy (above) and Tamura (below) transformers are lush enough for me.😉

But as usual in this hobby, YMMV. 

Happy Listening!😊

Musicmaster Model 12 (Gray clone) Tip + GE VRII Hack

Canon P + Canon 50mm f1.8 
Foma 100 in Rodinal 1+50

After many decades of collecting and using classic audio equipment and film cameras, I've learned to accept that sometimes I win, sometimes I lose, but most of the time I break even. And the only reason there is that possibility of breaking even is because I learned to DIY.

This tonearm came with a KS Musicmaster Model 25B12GST idler-driven turntable, which I thought I could resuscitate. Alas, the turntable was beyond saving because a lot of important parts were missing. The tonearm had no head shell slide and the cartridge pin contact points + wiring harness were gone. For many years this tonearm was boxed up along with other parts units sitting in storage.

One day I had an epiphany - will the Karmadon head shell slide fit? 

 I'm happy to report that the two types of head shell slides that my buddy, Sergiy, manufactures for his Gray Research tonearm clone work on this Japanese clone as well as on my original Gray Research 108C. Above left is a solid shell and on the right is a shell with a hole to accommodate the triple play feature of the General Electric RPX and VRII mono cartridges. 

Despite the carnage brought upon the Ukrainians by a deranged autocrat, my Karmadon head shells arrived in less than two weeks. We really have to admire and support these people!

I rewired the tonearm and blu-tacked 4 pennies to make up for the lost hardware.

A blob of 600,000 cSt silicone fluid was injected into the uni-pivot bearing cup.

Since the Karmadon head shell slide is lighter than the original, I used all three copper weights Sergiy provided, added 2 x 5 centavo coins + the GE VRII cartridge = 25 grams. 

I misplaced my VRII cartridge pins 😞...but after a bit of head scratching, I hacked two tube pins from a dead octal based tube and soldered them to the signal wires.😊

Voila!👍

For more viscous damped tonearm set up information, please click here!

 Even with my 20+ years of experience using this tonearm, it took me a while to dial-in the proper weight compensation due to the missing hardware + adapted head shell slide. Getting a viscous damped tonearm to function properly isn't for the faint of heart and requires patience. If you don't possess these virtues, I suggest you don't consider using one. But I must say the results are well worth it!😊

Musicmaster Model 12 + GE VRII

Let's listen to a few monaural hifi tunes!

🎶🎻🎹🎷

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! 😉

Begin the Beguine 2022

A well worn 78 rpm shellac disc of a Cole Porter classic recorded in 1938 by Artie Shaw spinning on a Gray Research HF500 turntable + a GE RPX cartridge amplified by my DIY je2a3 mono integrated fitted with a Hashimoto H203S output transformer driving a GE A1-400 speaker in a "vintage DIY" tuned pipe enclosure by Raymond H. Bates from Audio Magazine May 1955.

GE "single stud" RPX + 3 mil sapphire stylus
in a Karmadon slide shell

Cheers to 2022! Hopefully, it will be a much better year for all of us!

 

Gray Research HF500 Turntable + 108C Tonearm

My buddy John Piro has a knack for finding obscure vintage hifi pieces and has built up quite a collection. A couple of summers ago, he offered his spare blonde plinth'ed HF400. I had just acquired my first and only genuine Gray Research 108C viscous damped tonearm and couldn't pass up the opportunity to pair them up. 

Capstan Drive

The Gray Research HF400 turntable employs a unique drive system. Strictly speaking, it is not an idler drive. A round section rubber belt is partially embedded around the outer rim of the platter, which is driven directly by the motor shaft. Capstan drive is probably a more appropriate technical term.

45 + 78 rpm capstans

To change speeds, the corresponding 45 or 78 rpm capstan (or bushing as termed in the manual) is placed over the native 33 rpm motor shaft.

D&R turntable drive system
Courtesy of jamesvanarsdale.com

 AFAIK, the only turntable from this era which also drove the outer periphery of the platter is the equally rare D&R turntable, but as depicted above, it uses a rubber idler wheel. 

Seiko-Epson drive system
Courtesy of audio-heritage.jp

The Gray Research capstan drive may have been the inspiration for Mr. Takeshi Teragaki's three turntable designs for Seiko-Epson - ∑2000, ∑5000 and ∑5000II.

Servicing Tips

Download a pdf file of the Gray Research HF400 Manual for more detailed information.

This iron platter/bearing combination weighs close to 20 lbs. The 1" spindle tapers to 13/16" which turns on a 1/2" thrust sphere at the bottom of the sintered bearing well. 

After experimenting with a couple of belt sizes, a 3/16" (cross section diameter) x 36" polyurethane round belt x from McMaster Carr, catalog #3044K705 gave the steadiest stroboscope readings at all speeds.

Disassembly

Remove the four screws as indicated by the red arrows. 

The plinth lifts from the bottom frame. 

The top plate is a massive 1/4" thick metal resting on rubber pads at each corner. Prior to installation of new rubber pads, motor vibration could be felt at the tonearm finger lift.

 With new rubber pads installed (+ new motor mounts, see below), vibration was practically nil. The material I used looks very similar to replacement rubber soles used by shoemakers. 

Removing the motor 

To release the motor from the mounting bracket, straighten and pull out the cotter pins.

Left = worn out motor mounts
Right = fresh motor mounts

Another source of vibration were perished motor mounts. Brand new replacements are available from Surplus Sales of Nebraska -  Rubber Shock Mount, Part No. RPS - 426-0001.

 

New rubber mounts installed

Before reassembly, I cleaned the motor and re-lubricated the bearings with engine oil.

The sound is very energetic!

I've been enjoying my entire mono LP collection with the HF502! 

View it in action! 😊