With the foam issue out of the way, it's time to wrap this up!
If I never allowed myself to be conned by the Junkyard Jukebox guy to subscribe to his Sound Practices audio rag in the early 90s, I may have soldiered on tweaking my classic push-pull EL84 and EL34 amps and upgrading my LS3/5As (or adding) to this pair of Snell Type JIIIs (or maybe even Type Es) in my listening room.
But things didn't turn out that way...
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| Altec 755C + Open Baffle + Simple 45 amp |
I succumbed to the temptation of single ended triodes + Altecs!
The Snell Types E, J, and K have developed a reputation as single ended triode (SET) amp-friendly speakers. Arguably, my pair of Type JIIIs can be a good stop gap but I'll try to explain in the simplest terms as to why, in the final analysis, they don't meet my criteria for flea power amplifiers designed with "it's the first watt that counts" ideology.
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| Snell Type JIII specs |
Since I couldn't find a late 80s to early 90s Vifa catalog, I based all the specs from the above information provided by Snell. The low(ish) nominal impedance (Z) of 6 ohms is an advantage when driven by current source devices such as solid-state amplifiers, which can typically supply more power to a lower Z load. OTOH, vacuum tubes are inherently high impedance/voltage source devices, thus requiring output transformers to drive lower Z loads. However, any well-designed tube amp with an 8 ohm tap from the secondary of the output transformer shouldn't have problems driving the Type JIII.
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| Snell Type JIII |
While the man cave is hardly anechoic, this RTA trace is smoother compared to anything I've taken from any of my Altecs. It pretty much tracks the manufacturer's specs.
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| Altec 753C |
In spite of the fact that the Altec 753C's RTA isn't quite as smooth, it has a half octave greater extension in the low end. The top end also starts to roll off earlier, at around 13kHz. But as further discussed below, the performance of the Altec 802D compression driver + Altec 32C belies its 40s Western Electric roots.
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| Altec 414A vs. Vifa M21 |
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| Altec 414A in wide range mode |
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| Altec 414A specs |
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| Reverse engineered Snell JIII crossover |
Case in point, BBC engineers' extensive use of EQ in the LS3/5A crossover made it notoriously inefficient. But to their credit, whether it was the earlier 15 ohm or later 11 ohm version, it was a friendly load, especially to tube amplifiers.
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| Altec 753C crossover |
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| Left: Altec 802D + 20275 Right: Snell/Vifa D26 |
For the higher frequencies, Snell chose the Vifa D26 1.25" soft dome fabric diaphragm that has a radiating area of 1.23 square inches vs. the Altec's 2.25" diameter aluminum diaphragm with an equivalent 4 square inches of radiating area.
Snell employed a sharper 12dB/octave slope high pass filter for the dome tweeter to cut in @ 2700Hz while I blended the 802D compression driver/32C horn combo at a gentler 6dB/octave slope @ 3500Hz in the Altec 753C just where the 414A top end response starts to taper off.
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| Altec 802 + 32C horn |
I'm not set up to plot a reactance chart for the Altec 753C and Snell Type JIII but after using them with various amps in my collection, I guesstimate that both proffer a benign resistive load. However, the 16 ohm nominal impedance, simpler crossover of the Altec 753C and its greater efficiency are a godsend to low damping factor single ended directly heated triode amps.
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| Vifa M21WN-07-04 + Altec 755C |
During the era of Western Electric and Altec, engineers used their ears, guided by cutting edge technology test equipment. This can be gleaned from contemporary ads and press releases. I can't help but wonder if the Vifa woofer was designed merely to satisfy test instrument requirements and laboratory standards without any ear testing involved. If that is the case, is that what we consider progress?
I chose the Altec 755C over the near mythical Altec 755A for this feature because IMHO, it is a worthy benchmark for an 8" wide range driver that is still quite accessible and affordable in the real world. Based on the above specs, by the time Altec introduced the 755C in the late 50s (or early 60s?), they had conceded to the spec wars triggered by the commercialization of stereophonic equipment. I've listened to the 755C loaded in an OB, 2cf box or the Silbatone cabinet but never heard a solid 40Hz low end, merely well defined harmonics of that fundamental.
Granted the 755C can go a bit lower, subjectively, its low frequency extension isn't significantly greater than the 755A. I'm glad though that Altec was able to retain much of that captivating midrange + dynamics even if it's not quite as realistic as its older Western Electric-designed 755A sibling.
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| Altec 755C in the Silbatone box |
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| Snell JIII = 1.6 cf vs. Silbatone 755C = 1 cf |
Whether driven by my SET amps, Dynakit ST35 or Nobsound/JLH 1969 clone, the Snell Type JIII sounded veiled and anemic compared to the Altec 753C and Silbatone 755C. With the Snells, I have to turn up the volume a couple of notches to be engaged musically but with the Altec 753C or Silbatone 755C driven by my weakest 750mW per channel SE71A amp, I already hear subtle details even at background sound pressure levels (SPLs). Understandably, the JIII could not compete with the Altec 753C at the loudest end of the spectrum since it doesn't have the physical size to move as much air. But considering Snell's reputation, I expected better resolution and nuances at low to medium SPLs.
The most convincing full range sound I got from the Snells was when they were driven by the Music Reference RM9 amp, a push-pull parallel/triode connected EL34 stereo amplifier producing 35 watts per channel with the negative feedback set at minimum. Alas, with this combination, the irresistible charm of the single ended directly heated triode amp is lost...I can't have my cake and eat it, too.😔
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| Altec 755C in Silbatone cabinet + 3000H super tweeter Truth be told, lately, I find the use of a super tweeter redundant |
Through the years, I’ve tested a few vintage and contemporary 8” wide range speakers but haven't found any which could closely approximate the 755C’s sound quality. The design isn’t rocket science and if Great Plains Audio still has the original tooling, I don’t see any reason why the humble 755C PA speaker can’t be reproduced at a reasonable price. That would be a great boon to single ended directly heated triode amp aficionados, especially those who have limited space in their listening room.😊
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| Altec 753C + Snell Type JIII |
Contrary to current trends in speaker cabinet design, the wider front baffle area of the Altec 753C cabinet (and to a lesser extent, even the Snell Type JIII), enhances projection by acting as an acoustic soundboard. Western Electric and Altec speaker systems were usually fitted with wings in theater installations, which is the main reason I've been an advocate of the wide open baffle. In principle, this is practically no different to the fully open lid of a grand piano during a performance in a concert hall.
The Snell Type JIIIs can give a glimpse of what directly heated single ended triode amplifiers can do. But these are definitely not end game speaker systems for those who want to indulge in the delights of flea powered single ended directly heated triode amps. As competent as the Snells are and given their already above average sensitivity (compared to typical high end audio speakers), they could never spook me into believing musicians come alive in my man cave the way my Altecs can at times. For some organic reason, I can also listen to my Altecs for extended periods without listening fatigue creeping in. Keep in mind though that the empirical and subjective observations embodied in this article only reflect my musical aesthetics and priorities. YMMV.
I hope I was able to illustrate that there's no myth or magic to a fine sounding and efficient speaker system. All it takes is a basic understanding of the physics of sound and learning how to compromise.
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| Me, Devon, and Joey |
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| Vifa M21WN-07-04 woofer Left = $25/pr. foam (yellowish tint), Right = $40/pr. Euro foam |
In this day and age of marketing hype, spending $100 or so to import a pair of alleged original foam from European sources is, IMHO, not justifiable. How does one determine which retailer is being truthful?
Given that I wanted to give this project my best shot, when I noticed that Simply Speakers* added a Euro version to their website for $40 a pair/shipped, I placed an order. This is just one of the many reasons why this installment has been delayed.
*No affiliation, just a satisfied customer!
In Part 1, I re-foamed my pair of Vifa M21WN-07-04 woofers using the $25 foam kit. I specifically mentioned that the dust cap and cone are just one piece.
I've seen discussions in audio forums suggesting the removal of the dust cap to center the voice coil. I have to reiterate that the removal of the dust cap = a DESTROYED woofer!
After using both these foam kits, I can confirm that the voice coil on this particular Vifa woofer is self-centering. If you encounter voice coil problems, it's either the foam you used is suspect or you seriously deviated from the instructions.
Only one Vifa M21WN-07-04 was fitted with the Euro foam so I could compare them.
Die-hard Snell aficionados and "specialist" retailers contend that "generic foam" will kill the bass response of the Vifa M21 woofer. Given the RTA traces below, which foam is generic?
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| Snell JIII with Simply Speakers $25 foam |
This trace pretty much tracks the original specs at hifiengine.com.
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| Snell JIII with Simply Speakers $40 Euro foam |
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| Euro foam serial number |
FWIW, unlike the $25 foam, the Euro foam has a serial number. Does that give it more credibility?
Evaluations were conducted in full dimensional mono!
The sonic dissimilarity was very subtle. It only became obvious in A/B comparisons in which I was consciously listening for a difference. Also, as usual in audio, better metrics don't necessarily = better sound because audio tests (in this case, pink noise) are static while music is very dynamic!
That said, if your Vifa M21s are already fitted with the $25 foam replacement and you're not very DIY savvy, it's nothing to lose sleep over. IMHO, you're still listening to a pair of very decent classic speakers. However, if you're a seasoned DIYer restoring an unmolested pair of Type Js or Es with rotten Vifa foams, go for the $40 Euro foam!
Is the $40 Euro foam the original foam?
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| The Time Tunnel |
I wish I could travel back to the early 90s to find the honest-to-goodness truth.
Instead of worrying about matters beyond my control, I'm going to replace the $25 foam on the other Vifa M21 with Euro foam so I can listen in full dimensional stereo!
With the blessing of Early Bender of Hifitown.com, I uploaded two articles written in the 1980s for The Absolute Sound by his parents, Walt Bender (1944-2008) and Lennice Werth.
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| WE/Altec 755A is in Part I |
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| Berning EA230 is in Part II |
Olden Golden Components Part II
I've owned quite a few of the components discussed and still listen to a couple. This is a reflection of the articles' profound influence on my pursuit of the audio hobby. Since I believe that they are as relevant then as they are now, I added them to the JE Labs Arkiv.
Tube rolling is a fun aspect of the audio hobby. It only gets tedious when audiophiles start splitting hairs about a VT231, 5692, etc. I draw the line when an audiophool claims, "...my line stage preamp resolves the R train rumble under Carnegie Hall better when I use a 6AS7 in place of the original 6SN7..." 🙄
Those two tubes may be pin compatible BUT a power transformer 🔥melt-down🔥is imminent since the 6AS7/6080 draws 2.5 amps @ 6.3V. That's over 4 times more filament current drawn by a 6SN7, which only draws 0.6 amps @ 6.3V.
💣 💣 💣 Rolling tubes is dangerous unless you have a working knowledge of electronics to comprehend tube data/specs. 💣 💣 💣
It's been a while since I listened through Telefunken 12AX7 smooth plates on an RCA phono. Since I used to graft this circuit on a Dyna PAS preamp, I ordered a pair of 12AU7/12AX7 > 6SN7/6SL7 adapters to relive the experience on my RCA octal preamp.
Back in the 90s, Steve @ Angela Instruments had a boatload of Raytheon 5755s and shared a sleeve with me. Since I never found a project requiring these tubes, I got a pair of 5755/WE420 > 12AX7 adapters to listen to them in the Shure M65 clone. Piggy-backed to 12AX7>6SL7 adapters, they also worked nicely with the octal phono preamp.
Despite slight differences in transconductance and plate impedance between the 6SL7/7F7 and their younger 9-pin siblings (ECC83, 12AD7, 5751 and 5755), there was no visible variation in square waves nor frequency response aberration when I bench tested those tubes in both circuits.
Admittedly, loctals don't look as glamorous as their octal cousins with bakelite bases. But I'm very fond of them to the extent that I built and use a full function loctal preamp. I've been adopting unloved loctals at radio shows and hamfests. Essentially the industrial looking 7F7 and 7N7 are rebased 6SL7 and 6SN7, respectively! My only issue with loctals is, the tube pins are prone to corrosion. This is easily remedied by a wire brush + DeoxIT before use.
I purchased these tube adapters from the seller xulingmrs. They are very well made and fairly priced. Shipping cost and transit time from China was also reasonable. Highly recommended!
Way before I knew about SPUs and DL103s, I experimented with an entry level Audio Technica AT31E MC cartridge. Since my NAD 3020 didn't have an MC input, a pair of Sony HA-T10s were recommended at the same discount NYC store. I mounted the cartridge on a Grace G707 which was perched on a "molested" AR-XA. The sound was very different compared to my Grado GTE+1 - quieter background, more detail, deeper and wider soundstage, albeit less midrange presence and warmth.
I moved on to a Grado Signature 8, 8MX, MZ and lost track of my Sony HA-T10s. I probably loaned them to an audio buddy who forgot to return them. During a moment of nostalgia, I hit the BIN button for a pair @ a little over $100, shipped! I've listened to them with all the MC cartridges pictured above and they make pretty nice sounds!
Through the years, eBay sellers have benefitted from my blurb about Altec 755s, 32 horn, 414 woofer, 4722/15095, GE RPX, Gray Research tonearm + clones, Shure M3D and M7D, etc. Now I doubt if any Sony HA-T10 seller will even link to this upload.😆
Let me just say this to Shure microphone transformer sellers - as good as they are, once you break the $100/pair barrier, you've got tons more competition. So if you've got business smarts, be reasonable!😎
