Dad

My mentor and best friend

I am forever grateful!

February 22, 1927 - May 23, 2017

Electro-Voice EV 209-8A - 8" wide-range

During a visit to Sakuma's Direct Heating website, I encountered a cool SE 801 amp schematic designed for either a Lowther PM6 or an Electro-Voice 209-8A. I googled the EV 209-8A and nothing came up in Audio/DIY centric English language websites. But there were a lot of US dealers stocking the driver from as low as $18 each.

basic specs

After downloading and studying the detailed specifications at the EV website, I chose the cheapest internet seller and phoned-in an order for a pair. 

It cost $40/pair from Full Compass delivered within a couple of days to my doorstep. In spite of their great customer service, their packing left a lot to be desired - see the slightly wrinkled whizzer in the above right picture - the drivers were free floating in the box, not even tied down face to face ;( 

Due to lack of resources to build the recommended 1.8 cubic foot sealed cabinet, I loaded the EV 209-8A in a Heathkit 1.2 cubic foot ported cabinet, which used to house a Jensen P8RL + RP103. 

Heathkit 1.2cf + EV209-8A

Sharp fall off below ~ 90hz, otherwise the in-room RTA result was satisfactory. The tonal balance reminded me of a good mini-monitor speaker with no upper midrange nasties. It was also quite extended in the high frequency and at no time did I crave for a super tweeter.

Further internet research yielded this Japanese website which did an in-depth study of the EV 209-8A. Based on Chrome browser translation, transmission line loading was used to get around the bass deficiency.

Regardless of Qts values ;) and in keeping with JE Labs tradition, a trial in an open baffle is de rigueur. Since my original pair of OBs are currently in storage, I improvised a 55" wide x 32" high flat baffle using a 24" x 24" x 1/2' thick pine plywood baffle from my experiments in the 90s as the core, supplemented by cardboard extension wings.

OB + EV209-8A

Despite the even sharper fall off in mid bass response as shown in the RTA, subjectively, the bass extension was similar to the EV209-8a/Heathkit box combo. But the scale of the sound field produced by the EV209-8A/OB combo was a lot larger than when it was loaded in the Heathkit cabinet.

Since I discovered that my very first high efficiency speaker (a green KS 14703/Altec 755C) was carefully stashed in a box in the basement, I installed it in the OB to take a trip down memory lane. 

OB + Altec 755C

I've covered the Altec 755C in the Sound Practices No. 17 Homebrewer feature many moons ago, so I will spare adjectives to describe the subjective performance of the KS14703/755C. Suffice to say that the above RTA graph shows it all. It is just in a different class sonically and affordability! Perhaps not a very fair comparison for the EV209-8A because this driver with an intact cone and voice coil is worth about 20 times more when they come up for sale.

So even if I couldn't coax Altec 755C performance from the EV209-8A, its street price, efficiency, relatively flat impedance curve and midrange to upper frequency performance quality impressed me enough to bring it to the attention of the Audio/DIY world. 

hi-mu triodes: 75, 7B4, 7B6 + 7F7

Alternative hi-mu triodes in place of my favorite octals

The type 75 is the grandaddy of all hi-mu audio triodes culminating with the ECC83/12AX7.

Grid-capped 75s in the JE Labs Simple 45/2A3 with Noguchi PMF10WS OPTs.

loctal base + socket

Loctal or Loktal (as trademarked by Sylvannia) tubes were developed concurrently with octal based tubes in the 1930s. But loctal tubes were aimed at the then emerging car and portable radio market - hence, the need for a locking-ability in the tube socket, which required a metal base that gave the additional benefit of better shielding.

The 7B6 is a loctal version of the 75

I originally built the je2A3 mono integrated amp with 7B6s in the phono stage. Right now I am running 7B4s.

The 7B4 has slightly lower Rp than the 7B6. NOS samples are still very affordable so try them both ;)

I built this stereo preamp for the November Hi-Fi Show 2016. It uses 2 x 7F7s for the phono section which are direct loctal equivalents of the 6SL7. The line stage sports 2 x grid-capped 6F8Gs.

7F7 vs 6SL7

JEL preamp at the November Hi-Fi Show 2016 dressed in Harana Audio woodwork.

Radio Shack

In February of 2015, Radio Shack filed for Chapter 11.

So I was delighted to see this Radio Shack store announcing a comeback in midtown Manhattan during a visit in the summer of 2016.

When I was a student in NYC in the 80s, a neighborhood Radio Shack store was just around the block if I needed a resistor or capacitor for a project on a Sunday afternoon. By 2008, I was in the suburbs and Radio Shack was in a strip mall just a mile and a half away. Now I have to drive 35 miles to the next town ;(

In the early 90s, many SE amp DIYers started their foray into efficient speakers inspired by this book by David B. Weems. The speaker projects used various raw drivers from the Radio Shack catalog.

40-1354A

Radio Shack no longer had 2A3 triode tubes on their shelves when Sound Practices started publishing in 1992,  but one could still buy this 5 1/4" full range driver listing for less than $10, IIRC. This speaker was efficient enough to be driven by an SE2A3 amp to satisfying levels.

I used this driver in a compact bass reflex box...

from David B. Weems book

...as well as in a Tapered Quarter Wave Tube (TQWT)

Not quite in the same league of sophistication and refinement as the Altec 2-way, but lots of fun since they can boogie on a couple of triode watts ;)

Time Warp

During a recent "let's see where the wheel takes us" expedition, my wife and I spotted this in Pennsylvania. 

40-1310

As I browsed around the store, a pair of 40-1310 super tweeters bearing their original sticker price immediately caught my eye. I told my wife about them and she insisted that I get this pair of NOS Chinese-made plastic version for $60 + tax, so I can time travel.

These drivers developed quite a following in the 90s because the original all-aluminum units embossed Realistic were allegedly OEM'd in Japan by Fostex. The graphs above and below should corroborate this speculation. Later versions with a plastic pod and horn were subcontracted in South Korea and then China.

Fostex FT17H

I didn't join that 90s bandwagon. Instead, I bought a pair of the equivalent Fostex FT17Hs sans pod from Madisound for $70. I used them as super tweeters for Altec 755Cs and 755Es until they were superseded by a pair of superior Altec 3000Hs.

 Brand new Fostex FT17Hs are now made in China and can be had for a little less than $100/pair. I still believe they are excellent value for the money. Perhaps the early Japanese all-aluminum 40-1310s can command a slight premium, but beware of unscrupulous eBay flippers asking ridiculous amounts for the plastic version.

Subtlety

Before inserting the 40-1310 into the Altec 2-way, I bypassed the built-in electrolytic cap/choke crossover components. For the past 20 years, I've been using smooth and natural sounding paper in oil caps in the signal path of my preamp, amp and crossover, nothing else.

Altec 2-way + 40-1310

Altec 2-way sans 40-1310

In this application, the 40-1310's positive terminal is protected by a 1uf PIO cap and then connected to the high-pass section of the crossover. The effect of the super tweeter is subtle...just a touch more air.

As I was about to sit back to reminisce the 90s with the 40-1310, an internet friend informed me that Radio Shack just filed for another bankruptcy claim ;(

This prompted me to visit my favorite branch...

...fingers crossed. ;(

Altec small format diaphragms: Aluminum vs. Symbiotik

I've been playing around with Altec drivers for almost 20 years and have only listened to aluminum diaphragms until now.

Vostok Bezel Mods

From NATO'ed to Bezel mods

Vostok Amphibia 110640 + Bandukh Bezel

Murphy 1050 bezel + Seiko 'Pepsi' insert
=

Vostok "mod" Amphibia 420432

Budget SE OPTs - Edcor and Noguchi

All output transformers were tested in the je2a3 amp using the same procedure as I did in the Hammond 125ESE many moons ago. Listening sessions were done through the same amp driving a single Altec 2-way speaker system.