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Old 13th June 2010, 12:39 AM   #1
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Default AR-1 woofer - new enclosure?

My good fortune: nobody even bid the starting eBay price of $100 on my beat-up AR-1, Kloss and Vilchur design, earliest model, letter from Roy Alison, original manual, had it 45 years.

Even today, one of the great woofers of the universe... and I have been comparing it to my Klipschorn bass past few days (mixed bass, electronic crossover around 110 Hz).

So I've been thinking. If you had that particular 12 inch woofer with a strong-as-Masonite cone, reputed to have a 12 Hz free-air resonance (measures today about 39 Hz in the 1.2 cubic foot, "acoustic suspension," very very solid box), what would you do with it?

Please, no Karlson or tapped-horn designs. Almost for sure, needs a sealed box, eh. There seems to be no voice coil rubbing when mounted in any orientation.

Ummm, wouldn't it be yummy in a 3 cu ft box? Pity I have no access to those enclosure design programs, know the driver's T-S parameters, understand how to use them, let alone have much faith in their predictions (Patrick Bateman are you there?).

I'm crying at the prospect of cannibalizing a classic speaker but the market hath spoken. And where else can you find a 12 Hz woofer?

Thanks.
Ben

Footnote: yup, my ancient unused potted Partridge output transformer sold for a few nickels (OK... a few ten-thousand nickels).
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Last edited by bentoronto; 13th June 2010 at 12:54 AM.
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Old 13th June 2010, 02:44 AM   #2
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Well, the pioneers of audio claimed that the optimum vented alignment was one tuned to Fs and the cab's Vb whatever it was in a sealed cab that raised its Fs 1.56x, so since you have no faith in T/S et al, do it their way and you get most of the ~sealed alignment's perks with an extra half octave of gain BW.

GM
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Old 13th June 2010, 03:17 AM   #3
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Sorry if I seemed to be dismissing T-S. I have no doubt their analysis gives correct answers in engineering terms. It is just might not be as satisfactory in perceptual terms and hence might not deserve the uncritical adherence it gets in some places.

Indeed, the "pioneer" rules of thumb were an effort to create satisfactory perceptual experience in the absence of anything better than Olsen's textbook. For example, tuned boxes were shifted slightly off from the driver resonance (I forget which way but maybe up to give more oomph to the upper boom).
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Old 31st May 2011, 08:24 PM   #4
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Originally Posted by bentoronto View Post
My good fortune: nobody even bid the starting eBay price of $100 on my beat-up AR-1, Kloss and Vilchur design, earliest model, letter from Roy Alison, original manual, had it 45 years.

Even today, one of the great woofers of the universe... and I have been comparing it to my Klipschorn bass past few days (mixed bass, electronic crossover around 110 Hz).

So I've been thinking. If you had that particular 12 inch woofer with a strong-as-Masonite cone, reputed to have a 12 Hz free-air resonance (measures today about 39 Hz in the 1.2 cubic foot, "acoustic suspension," very very solid box), what would you do with it?

Please, no Karlson or tapped-horn designs. Almost for sure, needs a sealed box, eh. There seems to be no voice coil rubbing when mounted in any orientation.

Ummm, wouldn't it be yummy in a 3 cu ft box? Pity I have no access to those enclosure design programs, know the driver's T-S parameters, understand how to use them, let alone have much faith in their predictions (Patrick Bateman are you there?).

I'm crying at the prospect of cannibalizing a classic speaker but the market hath spoken. And where else can you find a 12 Hz woofer?

Thanks.
Ben
Ben,

I also have a pair of what may be AR-1 (prototypes ?) I found on the side of the road, all components working.

I may use the cones for tapped horns. Sorry, not what you want but a TH should give a six dB sensitivity advantage and may extend the FR down to the FS. A larger ported cabinet could also

From the web research I have done so far, found one reference saying the AR-1 bass cone FS is around 14-18 Hz.

The cones are the cloth surround with an deep Alnico magnet, I was amazed to find they are older than me!
The HF is a pair of 5" cones with felt dust caps in a "V" configuration, made of plastic with back chambers for the two cones.

I was looking for T.S. parameters for the woofer yesterday, but found none, and also found no reference to the 5" cones as tweeters.

Do you remember any AR- configurations using 5" cones for HF ?

Anybody know the TS parameters for the old AR-1 12" ?

Art
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Old 31st May 2011, 09:20 PM   #5
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Weltersys -

Take care, you may have something interesting there. Check these:

1. instead of two binding posts, has a whole bunch on back?

2. are those the famous Altec "Pancake" speakers that had a compliance ring about half-way out from the dust cap so that the cone could kind of change size depending on the frequency? It is very shallow. I say "famous" because it derives from the Bell Labs (West Street) lineage like a lot of Altec units.

The oldest ones had a smooth-surface woofer cone made from heavy and very very stiff cardboard with an accordion surround. I thought the resonance was around 12 Hz in free air but they may have varied over the years.

Later on, AR became committed to dome mid-range and tweeters in the AR-2 and -3 and -3a and these were pretty great speakers.
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Last edited by bentoronto; 31st May 2011 at 09:23 PM.
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Old 31st May 2011, 10:07 PM   #6
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Originally Posted by bentoronto View Post
Weltersys -

Take care, you may have something interesting there. Check these:

1. instead of two binding posts, has a whole bunch on back?

2. are those the famous Altec "Pancake" speakers that had a compliance ring about half-way out from the dust cap so that the cone could kind of change size depending on the frequency? It is very shallow. I say "famous" because it derives from the Bell Labs (West Street) lineage like a lot of Altec units.

The oldest ones had a smooth-surface woofer cone made from heavy and very very stiff cardboard with an accordion surround. I thought the resonance was around 12 Hz in free air but they may have varied over the years.
I think there may have been a full range input, and separate binding posts for the woofer and tweeter originally, (four or six separate binding posts) but I removed the crossover, tweeter pack and the extra binding posts after finding the "tweeters" rolled off around 10K.

The woofer has just a half round cloth surround, and a felt dust cover IIRC.
I don't recall it being super stiff material, just "normal" pulp cardboard.

They later went to a foam surround (probably 99 % of those rotted out) and ceramic magnets, so these are probably mid 1950s.

Art
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Old 31st May 2011, 10:41 PM   #7
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I really can't claim good knowledge, but the previous comments are my picture of the oldest ARs, till an expert replies. Cones is smooth, not really pulpy. Don't know about the half-round surround - the old ones are rather plain impregnated cloth with corrugations, as in olden days.

Could these have been re-coned?
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Old 1st June 2011, 05:14 PM   #8
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Originally Posted by bentoronto View Post
I really can't claim good knowledge, but the previous comments are my picture of the oldest ARs, till an expert replies. Cones is smooth, not really pulpy. Don't know about the half-round surround - the old ones are rather plain impregnated cloth with corrugations, as in olden days.

Could these have been re-coned?
Ben,

After some more research, it appears my speakers may be a prototype of the AR-2a, which was available from 1960-69.
I have no idea why a late 1950's prototype from Boston ended up discarded on the side of Hiway 14 in Madrid, New Mexico.

The AR-2a was a three way using the same cones with a (much needed) tweeter.

The AR-2a woofer was nominally listed as a 10, though the diameter is 11 1/8th, and the cone diameter inside the surround only 7.5.
It appears to be original, though what was a foam or felt ring is gone, just some glue or foam residue remaining. I painted over the cone, it looked like the AR-2a prior to the paint.

Ill try to Frankenstein some unused cabinets into a tapped horn today and post the before and after frequency response of the cabinets.

The speakers have about 17% second harmonic distortion with only 15 V at 40 Hz, so I'm not expecting "big" results...
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Old 1st June 2011, 05:25 PM   #9
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Thanks for info. I was trying to remember what an AR-2 looked like last night.

Testing at "15 V" sounds like a pretty big input, with the other gremlins in the testing chain on top of that.

Even today, I'd put an AR-1 or AR-3 (with a resonance around 38-40) among the greatest sounding woofers as far as making impressive bass in home music rooms goes. AR-2 was a junior size, if I recall. Cosmically LF output is a treat but on so few music recordings, hardly worth fussing over if it means other compromises (which it does).
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Old 1st June 2011, 05:42 PM   #10
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Originally Posted by bentoronto View Post
Thanks for info. I was trying to remember what an AR-2 looked like last night.

Testing at "15 V" sounds like a pretty big input, with the other gremlins in the testing chain on top of that.

Even today, I'd put an AR-1 or AR-3 (with a resonance around 38-40) among the greatest sounding woofers as far as making impressive bass in home music rooms goes. AR-2 was a junior size, if I recall. Cosmically LF output is a treat but on so few music recordings, hardly worth fussing over if it means other compromises (which it does).
15V is only about 28 watts, not very big in SPL level (with this speaker about 100 dB at one meter) or power.
The AR-2 and AR-2A (and whatever my speakers actually are) are 24 x 11.5 x 13.5, still fairly large by today's standards, but small compared to anything in the 1950's that had 40 Hz response.

Last edited by weltersys; 1st June 2011 at 05:45 PM.
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