Admiral Transmission Line Speakers from the 60's

Dan ʕ•ᴥ•ʔ

Peanut Head
Steven Z recently set me a set of old transmission line speakers from the sixties made by Admiral (TV's, stereos, etc.) They needed some freshening up. The cabinets were in remarkable shape given their age. I added binding posts and changed out the 2.2uf (9000 Hz) crossover cap to Nichicon poly-metal ones. They use the famous Foster (Fostex) AlNiCo F-103 with a helper cone tweeter. The sound isn't bad, more boxy and not as open as I am used to. The mid-band gets congested easily with bass heavy music.
But given their age, they are pretty dang good. I have enclosed some pics for you folks to peruse.
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je2a3

Senior Member
That's very cool!

The Akai Jet Stream supposedly uses a similar driver and similar in concept.

EDIT: But the Akai is sealed. I meant, there was no way to show the Akai's transmission line configuration without destroying the cabinet.

I apologize for the confusion this caused.


 
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JimPA

Junior Member
I do not see any damping material inside of the enclosure?
Adding some low density polyurethane foam in the line would be worth trying.
 

Thermionics

Post Whore In Training
So wait, is the Admiral TL + ported (trying to figure out what the mesh bit with the binding posts is)
 
Besides the Admiral... another speaker that used a Linear Transmission line, is the rather rare ESS AMT-1 Tower speaker. I thought this post might prove interesting since I spent some time feeding a tape measure inside these monsters to explore how they got the 6-foot long transmission line in there. If we take the 6-foot length of the transmission line... which was designed as a 1/4 wavelength chamber (1/4 wavelength means it favors a 45-hertz resonate frequency)... we can figure that the ESS Designers were trying to boost the low-frequency response down to ~ 45-Hertz (or a wavelength of 24-feet). I was amazed that the Admiral design seemed so ahead of its time. Low-frequency audio sound waves can be ~56-feet in length in order to reproduce ONE CYCLE of a 20-hertz sound wave (see link at the end). This presents quite a challenge for speaker designers. The Linear Transmission Line was one way of helping a given speaker cabinet to reproduce those lower frequencies. The problems were the given cabinet and respecting folded passage only helped a small bandwidth of these lower frequencies. (Go look at an old cathedral pipe organ sometime and the size of the pipes required as the notes get lower). My last comment is the Driver or Woofer must be of a LONG-THROW design to properly load the Transmission line or the effect is "lost" due to the lack of adequate pressure loading for it to "work". The crossover rebuild on these speakers was interesting as cramming in the replacement 75uF, 51.5uF and a 33uF set of caps was a challenge. The pictures are a bit out of sequence as the main topic is the Linear Transmission Line. The original 10" Alnico woofers (last pictures) are long gone very hard to replace. Currently experimenting with Goldwood 4-ohm and Cerwin Vega 4-ohm drivers
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20200221_095652.jpg20200221_095713.jpgAMT-1 Tower Transmission Line.JPGESS Tower Inside measurements.JPGAMT-1 Tower Transmission Line1.JPG116262434_10217615306124205_5742042119415943710_n.jpg116362309_10217615307884249_1825373804912614844_n.jpg
 

Dan ʕ•ᴥ•ʔ

Peanut Head
Today, I had some free time to work on these things and correct the mistake Admiral made with them. Being line transmisson's they were designed right....port at bottom...insulation lining the shelves....but for some goofy reason, they put a perforated back just above the port, which unloaded the driver and killed it's bandwidth. So today, I cut two pieces of wood, added pad for the back wall and installed the binding posts. The result is a much better speaker, in every way! 100_0456.JPG100_0546.JPG100_0547.JPG
 
Today, I had some free time to work on these things and correct the mistake Admiral made with them. Being line transmisson's they were designed right....port at bottom...insulation lining the shelves....but for some goofy reason, they put a perforated back just above the port, which unloaded the driver and killed it's bandwidth. So today, I cut two pieces of wood, added pad for the back wall and installed the binding posts. The result is a much better speaker, in every way! View attachment 33565View attachment 33566View attachment 33567
nice and thanks for the posts. they are likely efficient, are they good enough to be keepers?
 

Thermionics

Post Whore In Training
I remember hearing a set of TDL Studio 1's back when I was in college (being driven by a Conrad Johnson amp) and being pretty impressed with the sound of transmission line speaker technology.
 
Besides the Admiral... another speaker that used a Linear Transmission line, is the rather rare ESS AMT-1 Tower speaker. I thought this post might prove interesting since I spent some time feeding a tape measure inside these monsters to explore how they got the 6-foot long transmission line in there. If we take the 6-foot length of the transmission line... which was designed as a 1/4 wavelength chamber (1/4 wavelength means it favors a 45-hertz resonate frequency)... we can figure that the ESS Designers were trying to boost the low-frequency response down to ~ 45-Hertz (or a wavelength of 24-feet). I was amazed that the Admiral design seemed so ahead of its time. Low-frequency audio sound waves can be ~56-feet in length in order to reproduce ONE CYCLE of a 20-hertz sound wave (see link at the end). This presents quite a challenge for speaker designers. The Linear Transmission Line was one way of helping a given speaker cabinet to reproduce those lower frequencies. The problems were the given cabinet and respecting folded passage only helped a small bandwidth of these lower frequencies. (Go look at an old cathedral pipe organ sometime and the size of the pipes required as the notes get lower). My last comment is the Driver or Woofer must be of a LONG-THROW design to properly load the Transmission line or the effect is "lost" due to the lack of adequate pressure loading for it to "work". The crossover rebuild on these speakers was interesting as cramming in the replacement 75uF, 51.5uF and a 33uF set of caps was a challenge. The pictures are a bit out of sequence as the main topic is the Linear Transmission Line. The original 10" Alnico woofers (last pictures) are long gone very hard to replace. Currently experimenting with Goldwood 4-ohm and Cerwin Vega 4-ohm drivers
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Liverpool Met! J.W. Walker and sons finest effort imo. It’s being restored by Harrison and Harrison. Here’s to hoping the character is kept and the party horns left untouched.
Ok back to transmission lines...
 
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