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9 and 90 vs 3a


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The 9 and 90 were vertically-aligned, 4-way, dual-woofer floor-standing systems, with a focused soundstage & a more extended low-frequency response, and were capable of significantly greater output than a single 3a.

They clearly sounded like AR speakers, though, with their drivers being evolutionary descendants of those used in the AR-3a.

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Let me give you a little wider perspective.

The original AR ‘Classic’ speakers from 1954-1974 (which includes the 3a) were characterized by their precedent-setting bass response and smooth, ungimmicky mid-treble response.

The AR-3 introduced the industry’s very first dome mid and HF drivers in 1958. These drivers had extraordinary dispersion and smooth, accurate frequency response. The 3a followed the 3 in 1967 with improved mid and HF drivers.

Unfortunately, in order to achieve such wide dispersion, the dome drivers had to be very small in diameter, since dispersion is largely a function of driver size: the smaller the driver, the wider the dispersion. At that point in audio history, ferro-fluid cooling of the voice coil had not yet been invented, so these new small AR domes—especially the little ¾” tweeter with its diminutive ¾” voice coil—could not handle much power.

That left AR with a dilemma: “Hmmmm, we can either have very wide dispersion so that everyone in the normal seating positions in the room can hear the speakers clearly, even well off-axis, or we can have a hotter high end, but it’ll beam like a flashlight and you’ll have to sit in the sweet spot. What to do, what to do…..”

AR chose wide dispersion. As a result, they had to limit the voltage drive through the crossover to the tweeter and ‘pad it down’ somewhat, so the fragile tweeters wouldn’t burn out. That gave the original AR speakers a somewhat reticent, ‘polite’ tonal balance, very smooth to their supporters, dull and lacking in highs to their critics. Their response was smooth and nicely-behaved, free of destructive resonances, very widely-dispersed, but somewhat downward-sloping in the high end. AR’s own system responses showed this: The 2ax’s ¾” tweeter level, as an example, is about 8dB below the midrange level, according to AR’s own data!

But in 1975, AR invented ferro-fluid cooling, which was a method by which a magnetically-sensitive oil solution was suspended in the magnetic gap of the tweeter, surrounding its voice coil. The oil provided a far more efficient heat dissipation path to the nearby large metal mass of the magnet and poleplates for the voice coil to shed its heat than the air gap was on non-ferro-fluid tweeters.

This meant that the new AR ¾” ferro-fluid-cooled tweeters of the AR-11, 10 Pi and 12 could handle an incredibly greater amount of power than the 3a’s tweeter. The new tweeters didn’t need to be “padded down” with a reduced drive level, so the HF response of these new AR speakers was brought up to the same level as the woofer. The days of “dull, polite” AR speakers were over, for good.

But the original AR attributes of great bass, smooth response, wide dispersion, ungimmicky sound, etc. continued on, strong as ever.

The 9 and 90 were two full product families after the 3a, right after the 11, 10 Pi and 12. In the 9/90 family, the 3-way 91 would be considered the 3a’s closest relative.

I hope that puts it in a better context for you.

Steve F.

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How would you compare the sound of the 3a against the 9 and 90. From what I have been reading,, teledyne took a somewhat different approach to design than the original ar company.

Owned 3a's and AR10, (but not 9's). As to actual "sound differences" compaired to 3a:

1. AR10 clearly more transparent/anaylytical and brighter.. very different tonal balance and rather "unforgiving" of poorly made recordings .

2. Have listened to 9's: Similar to10's in tonal balance but much better " lateral imaging" in the "near-field".

3.The 9's deep bass IMO clearly superior to 3a's or 10, especially @ "live" listening levels. If you have 9's; probably don't need a "dedicated sub".

The above assumes you have plenty of "clean" power (300-500 watts/channel into 4 ohms).

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