Friday, May 20, 2022

Kutztown Radio Show Spring 2022

It's hamfest and radio show season!๐Ÿ‘

 

On Friday, May 13th, I drove through the back roads northwest of Philly towards Kutztown with Ding, who attended this event for the first time.


The weather wasn't very cooperative. Soon after we got there, this vendor had to move to the pavilion due to a heavy downpour.


There weren't as many vacuum tubes compared to the past years, but Ding found enough 5U4Gs to replenish is stash.


A pair of Utah Celeste 12" co-axials driven by a DIY 6CK4 SE amps in para-feed mode provided nice tunes.


A clean Rek O Kut belt drive turntable + Grado tonearm


A well worn ROK B12 Rondine with a Borg "death cube" motor


I've never been a JBL fan, but here's a pair of 4311B monitors + a Harman Kardon receiver.


Green Altec 802D + 806A!๐Ÿ‘ 
Unfortunately, the diaphragms were fried.๐Ÿ˜ฅ


Fisher mono receiver + a Scott stereo integrated


Art Deco and Noveau speakers


Hifi guys


A nice monophonic hifi system could be built around this University 6201 co-ax housed in a nice mid-century modern cabinet!


A pair of Heathkit W-7 PP EL34 monoblocks + a DIY tube amp


When stuff I used to see at Circuit City, Crazy Eddie, J&R Music World, The Wiz, etc. are considered vintage, we can only guess what that means.๐Ÿ˜†


Stereo Lab of Columbus Ohio demo'ing brand new Wharfedale speakers driven by a Leak integrated amp fed by a Leak CD player.


Visit the Delaware Valley Historic Radio Club website for more info.


Before leaving, I spotted this '56 Chevy Bel-Air.


My paternal grandparents had one, albeit, black and white, 235 cid "blue flame" straight six + three on the tree. It was in service until 1981. 


See you in September!

Friday, May 6, 2022

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?

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!




Friday, April 22, 2022

MC step up transformer redux + Hashimoto HM-7

When I ordered this pair of MC step up transformers from Mr. Isao Asakura of tube-amps.net (highly recommended๐Ÿ‘) for my cousin's system, he suggested the use of high-quality 24-gauge stranded copper wire. I also took note of his MC step up page, in which he discussed his chassis mounting experiments.

Taking the cue from my buddy Nate aka Redboy at HifiHaven.com, who’s a prolific audio DIYer and MC step up builder, I ordered a cast aluminum project box + 24-gauge stranded tinned copper wire from Amazon.

Hashimoto HM-7 - specs

Upon inserting the freshly mounted and wired HM-7 into my hifi set up, my Tamura TKS83 and Altec 4722 sounded comparatively hard and mechanical...๐Ÿค”

I had to retrace my steps.

Tamura TKS83

Those who are familiar with my Homebrewer article in Sound Practices #17 will remember that the TKS83 was mounted on an aluminum plate + wooden base while the Altec 4722 + others were on plastic project boxes. These were also wired using 99.999% 19-gauge solid-core silver wire + Teflon sleeving, Kimber TCSS or a combination of both. 

In hindsight, whether commercial or DIY, all the Japanese MC step up transformers I've seen in the metal or in MJ Radio Experiment and Stereo Sound Tube Kingdom magazines, were always housed in all metal enclosures or chassis.

Altec/Peerless 15095A + 4722

Before doing further listening comparisons, I remounted all my MC step up transformers on cast aluminum chassis and used 24-gauge tinned stranded copper for wiring. Since we're dealing with very delicate signals at tenths of a millivolt, very fine strands of high purity copper wire + maximum shielding make a lot of sense!

Hashimoto HM-7

After the playing field had been leveled, the Hashimoto HM-7 no longer outclassed my beloved MC step up devices. However, I'm pleased to say that the HM-7 sound falls somewhere in between the organically detailed and dynamic TKS83 and the rich and spacious airiness of the classic 4722!


Alas, these cast aluminum boxes weren't available when I started experimenting with microphone transformers as MC step up devices in the late 90s. Otherwise, I would've used them since I love the industrial vibe of unfinished aluminum!