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Hi there;

An interesting pair of MST's for sale on ebay #120061808720 in Great Britain.

They have, "Improved", stamped across their labels.

One photo has a round patch over the pre-cut hole on the right face to cover the deleted tweeter.

Not too often something is deleted to improve an item.

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These would be the early batch of AR-MST1 speakers while AR still had the original AR-MST cabinets with four tweeter holes routed out and the brass AR-MST logos left over in stock. AR had found technical issues in the original 4 tweeters AR-MST design and corrected it with the 3 tweeters AR-MST1. It was nice to see AR agreed to produce them in mirror imaged pair for the AR-MST1. In America, we just didn't know better or didn't care for mirror imaged drivers arrangement until 40 years later when the AR-303/AR-302 came out!!!

Minh Luong



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As I said in a post from September 2002,

"The MST was introduced in March 1975 along with the 11 and 10Pi as part of AR's new ADD (Advanced Development Division). The cabinet was shaped like a smaller version of the LST, with three radiating cabinet panels--one forward facing, and two angled away to the left and right of the front panel.

It used an 8" woofer and three 1 1/4" cone tweeters (similar to the tweeter in the AR-6 and -7), not the 3/4" dome. The speakers were mirror-imaged, with two of the tweeters side by side above the woofer on the front panel, and the third tweeter on the side panel. One side panel was blank. AR's instructions were to orient the speakers with the tweeters on the inner panels for a more tighly-focused stereo image, and to place the speakers with the tweeters facing out for a more diffuse, spacious effect.

The forward-facing tweeters crossed over from the woofer at 1600Hz; the outer tweeter handled frequencies above 5000Hz.

There apparently were some response irregularities in early-production MST's due to measurement inconsistencies between AR's different testing facillities, but this was straightened out in due course.

It was actually quite a nice sounding speaker, but the relatively high price ($159 ea. in 1976) for a speaker with a 3dB down point no better than an AR-6 and the difficult-to-place LST-type cabinet limited its commercial success.

Victor Campos, who was involved with the MST's design, said on "Shop Talk" (a Boston-area hi-fi radio talk show in the '70's) that the the MST's woofer design optimized all the theoretical magnetic and mechanical parameters for an 8" woofer in that sized enclosure. He said of the MST, "It could put out bass like nobody's business for an 8" woofer."

The MST/1 was always a mirror-imaged speaker in the US market. AR's 1976 literature (available in the Library) even described the different audible effect of placing the tweeter panel angled inward or outward.

I agree, however, that it was somewhat inconsistent that the 5, 3a, 11, 10Pi and LST-2 were not mirror-imaged, and all of those speakers had market lives that overlapped the MST/1.

Steve F.

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