Aluminum Wire

[charger3834]

I noticed that AR tended to use aluminum wire in their early speaker designs. They used it in the crossovers and in early tweeter and mid voicecoils. Why was aluminum selected ? Are there any issues with aluminum wire in speakers ?

[tysontom]

>I noticed that AR tended to use aluminum wire in their early

>speaker designs. They used it in the crossovers and in early

>tweeter and mid voicecoils. Why was aluminum selected ? Are

>there any issues with aluminum wire in speakers ?

I am not aware of aluminum used in the crossover itself, but the AR-3 midrange and super tweeter, and the AR-2a-series super tweeter used aluminum voice coils. The aluminum coil was free-standing, without a former. Aluminum was chosen because of its light weight, primarily. All these drivers were overkill design, using the magnets from the AR-1 woofer (for the 2-inch midrange) and the AR-2 woofer (for the 1-3/8-inch super tweeter). The domes were rigid phenolic-linen diaphrams, and the aluminum coils were bonded to the domes directly. The end result was a low-mass, low-distortion, heavily damped design that had virtually no ringing at any frequency, contributing to the almost ruler-flat frequency response of each individual driver measured anechoically.

--Tom Tyson

[Guest Nigel]

Aluminum wire in voice coils makes sense when the coil mass is a significant proportion of the total moving mass. In voice coil motor (VCM) design, you trade of resistance, turns, and mass to provide the required performance (dynamic response, temperature rise, ...). The assumption is nominal supply voltage.

It is left to the student to do the calculations. You will need to know the conductivity and density; of aluminum and copper. Have fun

Nigel

[ninohernes]

>>All these drivers

>were overkill design, using the magnets from the AR-1 woofer

(for the 2-inch midrange) and the AR-2 woofer (for the

>1-3/8-inch super tweeter). The domes were rigid

>phenolic-linen diaphrams, and the aluminum coils were bonded

>to the domes directly. The end result was a low-mass,

>low-distortion, heavily damped design that had virtually no

>ringing at any frequency, contributing to the almost

>ruler-flat frequency response of each individual driver

>measured anechoically.

>

>

>--Tom Tyson

What was the reason for redesign of the tweeters and midrange in the AR-3a?

[tysontom]

>I noticed that AR tended to use aluminum wire in their early

>speaker designs. They used it in the crossovers and in early

>tweeter and mid voicecoils. Why was aluminum selected ? Are

>there any issues with aluminum wire in speakers ?

There are three specific issues with aluminum wire: (1) it is brittle and under high power can develope a fatigue break or fracture (not uncommon failure in the AR-3 midrange and tweeter), (2) it fails sooner than copper because of its lower melting point and (3) it is difficult to solder (must use aluminum solder). Apparently the advantages of low mass were overshadowed by these considerations. Later versions of the AR-3 had copper pigtails soldered at the factory to the voice-coil leads, and this made it much easier to deal with the terminal strip.

--Tom Tyson

[charger3834]

Thanks Tom.

Am I correct in assuming that if one does not use aluminum solder on aluminum wire, one could get a cold solder joint ?

[soundminded]

I don't think that there is any doubt that AR struggled with midrange and tweeter performance throughout most of its history. While the original AR woofer design was merely refined over the decades, the midrange/tweeter concepts seemed to change again and again by evolution as well but also by radically changing and improving drivers and/or by using them in multiples such as in the LST and MST. The overall tonal balance of the earlier designs in real rooms was not completely satisfactory to many users even though the on axis frequency response measured flat. This fact shows that on axis frequency response is only part of the story as different speakers which measured more or less the same sounded quite different. IMO, the general trend in the market has been towards brigher sounding speakers to the point where many of today's so called audiophile designs are so shrill that when combined with solid state amplifiers and cd players (both having improved high frequency response over prior technologies IMO) they are not merely inaccurate but unbearable to listen to. And of course there are no tweeter or midrange controls or tone controls on amplifiers and "audiophiles" wouldn't dream of using an equalizer. Under current circumstances, the older flatter response of AR loudspeakers really show their worth more than ever.

[tysontom]

>I don't think that there is any doubt that AR struggled with

>midrange and tweeter performance throughout most of its

>history.

I wouldn't call it "struggled." As SteveF mentioned somewhere previously, AR was very advanced for its time, and the company was constantly researching and developing improved technology for its drivers. There were improvements in materials, manufacturing methods, etc. A good example of this was the use of a cloth surround for the 1-1/2-inch midrange on the AR-3a. This was an evolutionary improvement over the AR-3's complicated, and difficult-to-produce 2-inch dome with the urethane-foam suspension and butyl-rubber around the gap, etc. The new midrange was much easier to produce, showed greater consistency in manufacturing, as it was much more automated than the largely hand-built AR-3 drivers.

>balance of the earlier designs in real rooms was not

>completely satisfactory to many users even though the on axis

>frequency response measured flat. This fact shows that on

>axis frequency response is only part of the story as different

>speakers which measured more or less the same sounded quite

>different.

Well, the on-axis response of each individual driver in AR speakers was typically very flat and uniform, and the off-axis response was equally impressive -- better than anyone else in the industry at the time. The on-axis response of the "system," i.e., the speaker itself, is not perfectly flat from the lowest to the highest frequencies. The on-axis system respononse rolls off a bit in the highest frequencies relative to the midrange and bass, but since these speakers did have such outstanding dispersion (e.g., the AR-3 or AR-3a), the power response is very extended and smooth. Another way to look at this: if a speaker has excellent on-axis system response, but mediocre or poor off-axis dispersion, that speaker's power response will be very rolled off in the listening environment, and that speaker will actually sound dull, or sometimes harsh, unless you are directly on axis with that speaker.

--Tom Tyson

[tysontom]

>Thanks Tom.

>

>Am I correct in assuming that if one does not use aluminum

>solder on aluminum wire, one could get a cold solder joint ?

Brad,

You're damned if you do and damned if you don't. It's very difficult to solder with aluminum solder (Alu-Sol, made in England by Multicore Solders, Ltd.), but it's the best way to do it. Lead solder melts much better, but does not bond or melt onto aluminum properly. Aluminum solder contains a lot of flux, which helps, but it is still difficult to use.

I'll confess that I have cheated once or twice and used lead solder on aluminum, and it has worked, but I think I am lucky not to have had cold-solder joints. If I were rebuilding an AR-3, I would force myself to used Alu-Sol and do it right.

--Tom Tyson

[charger3834]

Working with Aluminum does not sound like a lot of fun. It's hard to believe they used to wire houses with the stuff.

[Guest Bret]

>It's hard to believe they used to wire houses with the stuff.<

It's hard to believe I bought a house knowing it had aluminum wire. I had an electrician come into the place and replace every switch, every outlet, re-connect every light fixture we kept, and put GFP protectors of one sort or another in every circuit.

They had to buy parts listed as approved for aluminum wire and painted the bear aluminum wire with something before making the connections. ( don't know what)

Within weeks I was cleaning breaker connections to stop arcing in the box.

There's nothing inherently wrong with aluminum as a conductor except it evidently expands and contracts and eventually connections made with screws and wire-nuts like to start arcing.

Bret

[Guest archoi]

hi ...

big magnet ....red cone ....aluminum wire

very powerfull..sounds great too

and four point cone mount access..

62.txt

[tysontom]

>hi ...

>big magnet ....red cone ....aluminum wire

>very powerfull..sounds great too

>and four point cone mount access..

Welcome ARCHOI! Incidentally, you have an impressive AR collection there in Korea!

The image that is shown in the second attachment (the two domes inverted on a table) are of the 2-inch AR-3 midrange dome and the 1-3/8-inch super tweeter. From that image you can see the free-standing aluminum voice coil (no voice-coil bobbin or "former") and the phenolic-dome material. The domes here don't show the fiberglass pad that is inserted inside the dome underneath for damping the cavity resonance. Later, fiberglass was also put *outside* the dome, under the screen, to improve damping further and to put an equal pressure on the outside to compensate for the inside pressure of the fiberglass pad -- originally causing some domes to "pop" out of the gap under certain circumstances. These first AR dome tweeters were the result of dozens of trial-and-error attempts by creator Edgar Villchur at making the foam suspension work. The first ones didn't work at all, but finally everything came together and these domes became the first commercially available, direct-radiator dome tweeters ever produced.

--Tom Tyson