AR3a Front Wired Drivers

[Guest matty g]

I have a pair of AR3a's date stamped July 1972 and the mids / tweeters are front wired. I recently saw a pair on ebay that didn't have front wired drivers. When did AR change this, or are the ebay units modified? I thought 1972 was close to the last year of production for the 3a.

Thanks

Matt

[RoyC]

The AR-3a was discontinued in 1976. The back-wired mids and tweeters appear to have been gradually introduced sometime in 1974.

Roy

[Steve F]

>The AR-3a was discontinued in 1976. The back-wired mids and

>tweeters appear to have been gradually introduced sometime in

>1974.

>

>Roy

I'd agree with this time estimate. In the blue-and black colored foldout lit that AR had in 1974 (the lit that intro'd the 4xa), the 3a is shown with back-wired drivers. This is also the lit that has the lowered x-o points for the 3a and 5.

In an August 1975 letter that I'd written to AR asking about their decision to market both the 11 and 3a at the same price of $295 ea, AR answered me back that their reasoning was partly determined by the cost of materials, which in the case of the 3a and 11 was very similar--hence the same retail price.

So if AR was still talking to me in August 1975 about the retail price and marketing strategy of the 3a, then 1976 seems to be a very reasonable assumption as to the date of the 3a's discontinuance.

Steve F.

[onplane]

>I'd agree with this time estimate. In the blue-and black

>colored foldout lit that AR had in 1974 (the lit that intro'd

>the 4xa), the 3a is shown with back-wired drivers. This is

>also the lit that has the lowered x-o points for the 3a and

>5.

>

>Steve F.

Steve, what "lowered" xover points? I never heard that AR changed the xover frequencies for the 3a (but then again I was just starting a family back then and HiFi was NOT may main interest).

Further, how did they do it? Did they change the coil or caps??

Steve, do you know what were they attempting to accomplish with this change?

Regards,

Jerry

[Steve F]

In 1974, the 3a's published w-m x-o changed from 575 Hz to 525 Hz, and the 5's changed from 650 Hz to 550 Hz.

Here is the whole story and my best "guess" as to what was going on, from a post of mine back in April of 2005:

"There has been a lot of interesting discussion on the Forum about the change in the 3a’s (and 5’s) crossover specification from 575 to 525Hz (in the 5, from 650 to 550Hz). These changes were first published in 1974, and according to a letter I received from AR (though not from Roy Allison, who had departed at the end of 1972), the new specs reflected, as they put it, "changes that had been made some time ago."

Tom Tyson has reported that Roy Allison doesn’t think the 3a’s x-o ever changed (although the 3a did continue in production for another three years after Allison left AR).

There is a very plausible explanation for the 3a’s and 5’s change in specs--an explanation that would be consistent with both Roy’s contention that the crossover never changed AND the accuracy of the newer specs.

Consider this:

As we all know, there is a difference between the electrical crossover and the acoustic crossover of a speaker system. If you run the voltage curves through the crossover network, they'll show a very definite characteristic whereby the "crossover" frequencies of the low-, mid-, and high-frequency sections are readily apparent, with no ambiguity whatsoever.

However, drivers do not behave as precisely and predictably in actuality as do electrical circuits. Even though the crossover may be "telling" the woofer to roll off by 3dB at, say, 600Hz, the woofer may in fact continue to respond acoustically until 650 or 700Hz. Drivers are imperfect devices: they have resonances, inertia, variable compliance, stored energy, etc. that makes them not "start and stop" exactly where the electrical "crossover frequency" would indicate.

Therefore, the result is that the driver’s acoustic curves overlap and "crossover" at different points than the electrical circuit of the crossover network. When Engineering finishes a speaker, they go to Marketing and show them the curves and other data. Marketing then interprets the data and decides how to rate the published specs for the product’s frequency response, x-o frequency, impedance, everything. The x-o voltage curves would say one thing, and the actual acoustic output of the drivers and where they overlapped would say something else. They were similar, but not identical by any means. Usually, the engineers would say to the head marketing person, "OK wise guy, where do you want to say it crosses over?" It was never clear-cut. It was always open to interpretation. I know this first-hand from over 25 years’ experience.

Therefore, I have the feeling that the re-specing of the x-o frequencies from 575 to 525 (3a), and 650 to 550 (5) were just a rethinking of how to characterize the existing—unchanged—data. This strikes me as even more likely to be true if the actual schematics and layout of the two crossovers never changed, as Roy indicated they never did.

Anyway, that's my take. It certainly seems plausible, especially since marketing people like lower crossover frequencies and this would have been an easy way for AR to appear to have made a small improvement in the speakers at a time (1974) when the company was under tremendous competitive pressure from Advent, EPI, JBL and others, and AR was failing quite badly in the marketplace."

Steve F

[onplane]

Great story, Steve!!

Thanks ever so much for the explanation.

My experience is similar with the marketing folks. They will do just about anything that “appears” to give their product an advantage. They’ll even concoct an entirely new vocabulary to confuse the public.

Regards,

Jerry

[dynaco_dan]

In the blue-and black colored foldout lit that AR had in 1974 (the lit that intro'd the 4xa), the 3a is shown with back-wired drivers.

>Steve F.

Hi Steve;

I still remember when AR was publishing their small promo catalog.

For several years after they had changed the woofers in the AR-3A from the cloth to foam surround, etc they still showed the earlier woofer's photo without the grille cloth on.

If I remember correctly it was to allow dealers to sell off their older inventory.

Once a new product is announced I don't think there is too many buyers who would want the older versions, with some exceptions in hindsight.

I am certain that once they started using the newer AR-3a photos AR probably received lots of questions about compatibility and sound difference and power handling.

When the cloth to foam surround was changed I wrote to AR and was told there was no audible difference.

If my memory serves me correctly I've seen AR-3A's and LST's on ebay that had probably been built for the front wired drivers but instead they had internal connection drivers.

Where the solder connection pads were was a pad of some sort but no leads on the surface, rather a hole patch.

[RoyC]

AR-3a tinkerers should be aware that the AR-3a woofer inductor was changed from a #7 (1.88mh) to a #9 (2.85mh) about the time that the alnico magnet cloth surround woofer was replaced by the ceramic magnet foam surround woofer (1969/1970).

In January '06, in a thread entitled "The AR-3a Woofer-Coil Mystery --A Solution", Tom Tyson reported that Roy Allison remembered that early change to the crossover.

Roy

[Steve F]

>AR-3a tinkerers should be aware that the AR-3a woofer

>inductor was changed from a #7 (1.88mh) to a #9 (2.85mh) about

>the time that the alnico magnet cloth surround woofer was

>replaced by the ceramic magnet foam surround woofer

>(1969/1970).

>

>In January '06, in a thread entitled "The AR-3a

>Woofer-Coil Mystery --A Solution", Tom Tyson reported

>that Roy Allison remembered that early change to the

>crossover.

>

>Roy

Yes, I remember that thread well. The coil change seems to slightly contradict Roy Allison's earlier statement to Tom Tyson that the 3a's crossover had never changed. No one is trying to "catch" Mr. Allison in a 'gotcha' moment, of course. This information only serves to illustrate that memories of very small details can become a little blurred with the passage of 35-40 years, especially to those people who aren't thinking of it every single day. I do not remember if my 8th-grade Jr. High baseball uniform had blue stripes or black stripes. But I do remember that I pitched for the King Phillip Warriors. An historian who researched all the relevant docs could tell us the color of the stripes, but that doesn't mean that I was being intentionally deceptive or that the bigger memory--that I was 2-1--is inaccurate.

In any event, the 3a's coil change in 1969/70 could still be considered consistent with AR's 1974 statement to me that the revised crossover spec reflected "changes that had been made some time ago."

Steve F.

[RoyC]

I completely agree, Steve. The wording of my post was strictly meant to clarify the fact that there was indeed a crossover change in the AR-3a.

Roy

[Steve F]

Thanks, Roy.

I accurately understood your post and knew you that you meant everything strictly in a positive sense. I was just expanding on it with my own examples.

Steve F.

[johnieo]

We know four things:

--Early AR literature gave a 575 Hz x-o frequency; later literature listed it as 525 Hz.

--experimental observations showed AR-3a with Alnico woofers used AR-#7 coils; with ceramic magnets used #9 coils.

--Documentation from Tom Tyson's AR-archives stated that the coil was changed.

--calculations show that this inductance increase produces said change.

This same question will undoubtedly be asked again in another year as the details are scattered in myriad earlier posts. Reasons-- we can argue about all day long; facts speak for themselves.

[onplane]

I went back and read the original thread and the more I read ... the more Steve’s explanation seems plausible.

This change from the #7 coil to the #9 coil is a little confusing. Clearly that change had no impact whatsoever on the mid driver and usually an xover frequency change would impact both drivers at the boundary.

Further, and we better ask Roy to double check my logic here, it would appear that the insertion of the #9 coil:

1. REDUCES the current (and naturally output) in the woofer over it’s ENTIRE range (higher resistance AND inductance in SERIES with the woofer)

2. due to the higher inductance, this REDUCTION is NOT the same at all frequencies and will be greater at higher frequencies

3. has NO impact on the mid-driver

All of the above, of course, assumes a constant applied voltage.

I think Steve has it right. That is, this was a marketing call.

Regards,

Jerry

PS: Roy, please let me know if I screwed up on my analysis.

[johnieo]

Voltage transfer calculations include coil resistance. The two woofers have different acoustical efficiencies; the mid and tweeter levels are adjustable. Crossover frequencies are not determined by balloting.

[onplane]

>Voltage transfer calculations include coil resistance. The

>two woofers have different acoustical efficiencies; the mid

>and tweeter levels are adjustable. Crossover frequencies are

>not determined by balloting.

Hi, John!

John, maybe I missed something here, but it was my understanding that the coil change occurred well AFTER the woofer change.

If this is the case, then we are dealing with differences that are soley determined by that coil change.

Your point about the adjustments is valid, as one could argue that the pots will change the xover frequency.

Regards,

Jerry

[RoyC]

>it was my

>understanding that the coil change occurred well AFTER the

>woofer change.

Jerry,

It is very unlikely that the coil change occurred after the woofer change.

Based on a fair amount of data compiled by John and myself, with the assistance of other forum members, it is likely that the coil change occurred at the time AR began manufacturing the 3a with the ceramic magnet, foam surround woofer. I have measured and heard small (but consistent) differences between the foam surround and cloth surround woofers that would suggest that AR made the adjustment to the crossover to compensate for the slightly different woofer characteristics. It should also be noted that it appears that the amount of cabinet damping material was reduced about the same time.

It is therefore prudent to try to keep the AR-3a woofers matched to each other, and to the cabinet/crossover era from which they came.

Roy

[onplane]

Thanks, Roy!!

I didn't realize these changes occured at the same time and it certainly does make sense that they would. I guess I was too tired when I was reading the older posts.

Sorry!

Regards,

Jerry