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.

Altec Aluminum Diaphragms

Altec 20275
Aluminum voice coil
DCR = 9 ohms

The 16 ohm Altec 20275 is the original diaphragm fitted to my cherished green hammertone 802D. This is the Altec diaphragm I am most familiar with and to my ears its tonal balance favors the midrange more than the later 34852, which is known for better high frequency extension.

I speculate that late 40s to 50s wrinkle charcoal gray/brown and late 50s to 60s hammertone green 802s, 804As and 806As command premium prices IF they are fitted with original and intact 20275s, which are now unobtainium. By early to late 70s, black 802s and 806s were fitted with either the 16 ohm 34852 or the 8 ohm 34647.

Altec 34852
Copper Clad Aluminum Wire voice coil
DCR = 12.5 ohms

My Altec 605B Duplex should have been originally equipped with a 20275 but by the time I acquired it, this 34852 was already fitted. Maybe that's why I still got it cheap ;)

As previously noted in my 605B experiments, I hear a significant sonic difference between a 34852 and a 20275, so much so that I cannot recommend their use as a stereo pair. Jeff Markwart has more 20275 vs. 34852 info if you scroll down to the bottom of this page. 

GPA 34852
Copper voice coil
DCR = 11.5 ohms

AFAIK, Great Plains Audio is the only source for Altec diaphragms made to original Altec specifications. Even if they have a website, they prefer to do business the old fashioned way. I always call Bill Hanuschak to place an order and never had problems.

I haven't had a chance to compare this GPA 34852 to the Altec 34852 because the 605B Duplex was left behind in the attic;( But there's no doubt that this GPA is the real thing - very dynamic, with clean and clear harmonic overtones up the wazoo!

Altec Clone

Chinese Aluminum Diaphragm Clone
Copper voice coil
DCR = 11.9 ohms

For kicks, I made an offer to one of the Chinese vendors on eBay and got this pair of 16 ohm diaphragms for about $24/pair, shipped. These clones will tide you over in a pinch. However, even a casual comparison to an Altec original or GPA diaphragm revealed smeared harmonic overtones and compressed dynamics.

Spot the fake

Left picture (clockwise from left) - older version Altec diaphragms used screw terminals on a raised platform, later Altecs and GPAs have tabs, Chinese clones do not have a raised platform for the screw terminals. 

Right picture - The raised platform in the Altec uses tapped machine screws whereas in the Chinese copy the screws are self-tapping.

Altec Symbiotik

I recently acquired a couple of unloved 70s era 802 and 808 drivers, some fitted with Symbiotiks. 

Two abused Altec diaphragms:
Symbiotik on the left and aluminum on the right

The Symbiotik was Altec's initial response to the 60s demand for a higher power handling diaphragm. As pictured above, due to the rigidity of the aluminum suspension, it can shatter when overdriven. I can only surmise that the Symbiotik  diaphragm, which uses a polyimide/mylar type suspension, evolved from a research and development project at LTV by John Hilliard and Jonas Renkus.

Early + Later Symbiotik diaphragms

In early Symbiotiks, the abrupt 90 degree angle voice coil termination (left) also caused failures in the field due to metal fatigue. I repaired this early Symbiotik by carefully flowing solder between the broken ends with a low temperature soldering iron. This issue was rectified in later production Symbiotiks (right). 

Uncovered: Altec > Emilar

Top = early Emilar with brown mylar suspension
Bottom left = later Emilar with gray mylar suspension
Bottom right = Altec Symbiotik

I have written favorably about Emilar and Renkus-Heinz compression drivers, and noted that their extreme top end was a bit reticent compared to Altec drivers with aluminum diaphragms. Let's see how the earlier Symbiotik technology stacks up.

Top = later Altec Symbiotik with tabs and
improved termination
DCR = 6.7 ohms
Bottom = early Altec Symbiotik with
screw terminals
DCR = 7.5 ohms

In retrospect, Altec aficionados may have been hasty and/or unkind in their initial reception of the Symbiotik. Even if the Symbiotik rolls off earlier than its aluminum brethren, it still reproduces proper harmonic overtones. It sounds very sweet, airy and open, with none of the smearing and compression I hear from the Asian clones. A Symbiotik equipped 802/808 sounds more organic than its descendants from Emilar and Renkus-Heinz. To my ears, the Symbiotic diaphragm has a niche in Hi-Fi and may well be the antidote to those who find the aluminum diaphragm a bit aggressive. 

Unfortunately, there are no modern replacements for Symbiotik diaphragms. You'll have to find original units that did not suffer catastrophic meltdowns. Although it's just a hunch, the Radian replacement diaphragm for Altecs should have Symbiotik DNA because of the Emilar/Plus One connection.

Octave RTA by Onyx

Since affordable audio measurement apps have become available, I got this $5 app for my iPhone as suggested by my buddy J-Rob.

Test set-up

The Altec 414A housed in a 3.5 cu. ft. repurposed Madrid (861) bass-reflex cabinet is driven full-range, J-Rob style, while the Altec 32A metal horn + driver combo is protected by the crossover + EQ below.

Crossover + EQ

I was quite surprised to see pretty decent RTA results since I've been building/tweaking crossovers for over 20 years without a computer simulation program or an RTA.

Altec 802-8D + GPA 34852

Altec 808-8A + Chinese 16 ohm diaphragm

Altec 808-8A + Symbiotic

Emilar EA175-16 (alnico)

Emilar EC175-8 (ferrite)

These graphs pretty much represent how these driver/diaphragm combinations perform except the Chinese clone which looked good but sounded rolled off, compressed and smeared as mentioned above. Unlike human ears, an RTA will measure sound waves but will not discern unmusical harmonic overtones. Even my wife thought the Chinese diaphragm sounded muffled. Although she argues that if I can afford only a $12 diaphragm, I better be happy with it ;(

It goes to show that it is much easier to satisfy audio measuring equipment than human ears. 

Update

Check out HifiTown's Altec 808-8A video! 

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. 

Edcor GXSE15-16-3.5K
Weight = 2.75 lbs

Primary Z = 3.5K

Secondary = fixed @ 16 ohm

Frequency Response = 40Hz - 18kHz, <1dBu 

Maximum DC current = 190 ma.

Core Material = M6, 29 ga. grain oriented steel

I ordered this Edcor OPT to get a feel on what's available to a cash-strapped US-based DIYer. It took over 3 weeks to be delivered to my doorstep at a total cost of $58.67. The nice square waves indicate quality manufacturing. Bass performance was at par with the Noguchis. But from the midrange to higher frequencies it was not quite as open and transparent. Maybe the Japanese manufacturers use higher quality laminations than the M6 steel used in this Edcor? Since the Hammond 125ESE now sells for about $60 before shipping, the GXSE15-16-3.5K would have been much better value for the money if it were offered with at least two secondary taps.  

Colors in Kanji

Noguchi PMF10WS
Weight = 3.2 lbs

Price = JPY 9,070
Approx. US$80

These two pairs of Noguchi transformers were Akihabara souvenirs from our 2015 Tokyo trip. In spite of the significant difference in price, the PMF10WS and PMF15WS are physically the same in size and weight. Based on specs, the PMF15WS has greater bandwidth and more flexibility for use with various output tubes.

Both OPTs tested well on the bench. Even if the 10khz square wave test does confirm better top end response from the PMF15WS, I could not detect its sonic superiority over the other.  Sonically, the PMF10WS is just as good if you don't need the extensive multi-tap flexibility from its more expensive sibling. In terms of tonal balance, I prefer the warmer presentation of either of the Noguchis over the leaner and more analytical Tango U808.

Noguchi PMF15WS
Weight = 3.2 lbs

Price = JPY12,560
Approx. US$112

I'm not sure if Noguchi accepts international orders. But if you're visiting Tokyo, their basement shop (closed Mondays) at Tokyo Radio Department Store is a must see!

!!UPDATE!!

The entire line of Noguchi is now represented by General Transformer in the same location at Tokyo Radio Department Store in Akihabra and they accept international orders.

Noguchi Finemet

Just a preview ;)

Dr. Jose P. Rizal

Rizal portrait
by
Juan Luna

In commemoration of our national hero's martyrdom on December 30, 1896, let's reflect upon a few words of wisdom he left behind. They are very relevant today as they were over a hundred years ago.

On Education:

"My countrymen, I have given proofs that I am one most anxious for liberties for our country, and I am still desirous of them. But I place as a prior condition the education of the people, that by means of instruction and industry our country may have an individuality of its own and make itself worthy of these liberties."

What Rizal stood for:

"I do not write for this generation. I am writing for other ages. If this could read me, they would burn my books, the work of my whole life. On the other hand, the generation which interprets these writings will be an educated generation; they will understand me and say: 'Not all were asleep in the night time of our grandparents.'"

Dr. Rizal's Noli Me Tangere and El Filibusterismo have been required reading for high school students since the 1950s and the essence of these novels is still very pertinent in our present day society. But why have we allowed the oppressors to develop from within?

November 2016 Hifi Show Report

Sierra Audio

Back in the late 90s, I frequented a west coast based website, Sierra-Brooks, that featured beautiful hand crafted wooden horns. Half of that partnership was Victor Sierra, a Filipino from Cebu City. In the interim, Victor had been busy managing their family business. The local audio community warmly welcomed their premiere participation in this event!

Their demo featured 3-way horn loaded speakers.

Driven by a stereo SE45 designed and crafted by one of his collaborators (below, left) using locally wound transformers by Edrel Sison

Congratulations Victor (right). Good job!

Friends in Audio 

This group of audio enthusiasts featured a 2-way horn system + super tweeter using my favorite Altec 414 woofer and a handmade wooden horn driven by an Altec 806A + EV T-35 super tweeter. At the front end was a Garrard 301 with a locally crafted linear tracking tonearm. A custom tube preamp and amp completed the system. 

Harana/Setup/Tono

Garrard 401 with a Dynavector DV507 tonearm fitted with either a Denon DL103 or Ortofon SPU-GME and a laptop/DAC combo digital source fed through a pair of Western Electric WE111C repeat coils

JE Labs stereo preamp dressed in Harana Audio hand crafted wooden case, loktal 7F7 tubes for the phono stage + 6F8Gs for line level

Harana Audio dual mono SE300B amps - Jensen input transformer > WE417A > Tango NC20 > WE300B > Tango NY15-3.5S output transformer

Harana Audio 2-way horn speakers - 15" Beyma woofers in V-Vent II enclosures, JBL 375 compression drivers behind carved horns + JBL super tweeters

For more pictures and information, please visit the November Hifi Show FB page.