Snell Type JIII Finale - Sensitive Enough?

With the foam issue out of the way, it's time to wrap this up!

Snell Type JIII Part 2: $25 foam vs $40 Euro foam

Re-foaming the 8" woofer found in various incarnations of the Type E, J and K Snell speakers is a very contentious issue exacerbated by their cult-like status amongst audiophile admirers. 

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!

WARNING!

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.

RTA Traces

$25 foam vs. $40 Euro foam

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?

Snell JIII with Simply Speakers $25 foam

This trace pretty much tracks the original specs at hifiengine.com. 

Snell JIII with Simply Speakers $40 Euro foam

If we split hairs, this $40 Euro foam trace looks just a touch more ragged. 

Euro foam serial number

FWIW, unlike the $25 foam, the Euro foam has a serial number. Does that give it more credibility?

Listening to Foam 

$25 foam vs. $40 Euro foam

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! 

Listening to Billie, Ella, Julie, Frank, Tony and Johnny H, it was relatively easy to discern better midrange presence from the unit fitted with the Euro foam. When I pulled out my Ray Brown, Curtis Counce, Charlie Haden and Mingus CDs and LPs, I heard more tuneful and articulate bass lines from the Euro foamed woofer. The woofer with the $25 foam had a tendency to sound boomy while the midrange was just a touch veiled. 

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?

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!

Go to Part 3 or back to Part 1

Snell Type JIII Part 1 - Deconstructed > Re-Foam

 In the late 80s, I could have gotten a Snell Type E or J after unloading my Magnepan SMGas. But I loved the sound of EMI and Decca recordings, for which I give credit to BBC-trained sound engineers, so I invested in a pair of Quad ESL57s and Rogers LS3/5As instead. I was such an Anglophile that I even became a partner in a company that imported Art Audio Amplifiers and Spendor Speakers to the Philippines. Unfortunately, we didn't make money...but that's another story.🤣

 

During a moment of nostalgia, I chanced upon this pair of Snell JIIIs online. I messaged the seller expressing interest. After two weeks of silence, I made a polite follow-up and was surprised to receive a reply that they were still available. According to the seller, he's had several offers from tire-kicking flippers but he chose to sell to me because I sounded like an enthusiast who'd give them a good home.😄

Typical of speakers from this era, the foam surrounds have disintegrated. Other than that, this is a very clean pair with consecutive serial numbers just like when they were sold in high-end audio salons in the late 80s to early 90s.

While waiting for the replacement foam surrounds, I thoroughly cleaned all vestiges of old foam from the cone and speaker frame. This was the most tedious and time consuming step in the re-foaming process but essential for a successful result!

 Meanwhile, I also took advantage of the down time to analyze what makes this speaker system tick. 

Deconstruction

Peter Snell was a very gifted speaker designer. Due to his untimely demise at age 38 in 1984, speaker models that were manufactured during his lifetime have developed a following. Peter Qvortrop of Audio Note UK was a big fan of the 2-way Type E, J and K models and continues their legacy in the Audio Note E, J and K using custom drivers and boutique parts.

The Snell E and J had front mounted reflex ports while the K was a sealed box/acoustic suspension design, which employed a different woofer. A rear firing 3/4" dome tweeter was added to the EII model, while the reflex port was moved to the back of the cabinet in both the EII and JII.

Vifa D26TG-05-006

The EIII, JIII and KII designation denotes the switch from a Tonegen 1" doped silk dome tweeter to the Vifa D26TG-05-006 6 ohm 1" dome pictured above. A tweeter level control was also added on all models. 

According to the Snell Type JIII brochure, the Vifa D26 tweeter handles an octave of upper midrange frequencies from 2.7kHz + another two octaves of harmonic overtones.

Even if the JIII was manufactured posthumously, it retains the cabinet dimensions and proportions of the original model. After many years of experimenting with open baffles, Altec 614 and 618 and  cabinets, I'm a firm believer in the acoustic superiority of Rubenesque front baffles over Victoria's Secret slim waifs.😆 

Was the use of plywood (top, bottom and sides) + chipboard (front baffle and back panel) chosen for acoustic reasons? Regardless, the cabinet is of pretty high quality construction with particular attention placed on rigidity - see the brace from the front baffle to the back panel in the picture below.

Good quality air core inductors, electrolytic and film capacitors or a combination of both + an L-pad for tweeter level adjustment were used in the crossover network.

The high-pass is a straightforward 12 dB/octave 2nd order slope hinged at 2.7kHz, as previously mentioned. On the other unit, there was an additional electrolytic cap in the high-pass section with a higher total capacitance reading. This confirms Snell's claim of matching their units to within +/- 0.2dB based on a reference model in their factory. 

Likewise, the low-pass section is also a 2nd order slope + an EQ/contour network for the Vifa woofer (see the LCR combo highlighted in red above). Explaining how this EQ works is beyond my technical ability. My empirical mind just knows that it "shapes" the woofer's frequency response. A similar, albeit more complex, crossover + EQ can be found in the BBC LS3/5A. 

Since all the capacitors measured close to their indicated values, there was no rationale to change or upgrade. Besides, I want to hear these speakers as close to how they were originally designed.

Vifa 8" M21WN-07-04

AFAIK, the Vifa 8" M21WN-07-04 was the only woofer used in the J, JII and JIII. Based on the 49Hz-20kHz +/- frequency response specified in the JIII brochure, and cross-referenced to my Musical Instrument Frequency Chart, this drive unit/cabinet combo was tasked to cover six and a half octaves of musical information starting from the bass frequencies up to midrange fundamentals. 

Re-Foam

After judiciously sifting through audio sites on the net, I chose the $25/pr. foam surrounds from Simply Speakers because they were recommended by audio hobbyists who exhibited good ears and common sense. Check their re-foaming video for a straightforward and confidence-inspiring tutorial.

 The Vifa M21 voice coil is essentially self-centering. So don't even consider cutting or removing the dust-cap to shim the voice coil. It'll be ruined because the cone + dust cap is one whole piece. 

 

Not bad for a first attempt in replacing foam surrounds, huh? 😉

Since time immemorial, I've been evaluating drivers bare naked (or mounted in a simple baffle) to hear their potential. After 25 years of enjoying Altecs, these drivers sound very different...🤔  

Snell JIII in room RTA (Onyx iPhone app) 
Snell JIII specs

I have to live with this speaker system for a while and play lots of tunes 🎻♫🎶♬🎺and will report back in Part 2!😊

See Part 2 and Part 3