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Hello, I'm an old estimator AR sound and I own a pair of AR 6 and a pair of AR MST 4 Tweeter . My question ... according to an authoritative your opinion would make sense to convert the MST in a three tweeter system? I would get a significant improvement ? As obvious would change the crossover. Thanks for your attention. Regards

Alessandro

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Hi Alessandro, and welcome to the board.

you might find this thread useful;

there's quite a lot to read, but it does give some interesting information further down on the difference between the two systems. Once you've had a look at that, any specific questions might get picked up by ra.ra, who seems to be our resident expert on MSTs. They didn't go down big in America, for reasons that are explained in other threads on this board. (There are only about four MST threads on the whole board, so it doesn't take long to find them!)  So they don't excite a huge amount of interest....but they have their fans!.

I'm interested in them because they are the last of the 'Classic' series with the white linen grille.

after that.......pfft.....

regards/Tim

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Hello Alessandro. I do not have enough experience with the MST model to respond with much authority, but I first think you might offer some personal assessments about how you like the performance of your speakers in their current 4-tweet configuration. My limited understanding is that the original four tweeter version, with all tweeters responding to the same frequency range, was found to create some unpleasant interference between the front-facing and angled-facing tweeters, and this troubled the engineers enough to warrant a revision to become the later three-tweet model.     

The pair of MST's highlighted in the thread cited by TTonga seems to have been a hybrid of sorts, using four tweeters but also the revised crossover concept of the later three tweeter MST-1, which delivers only the highest frequencies to the tweets on the angled face(s). To me, this would seem like the best of both worlds, and if you think your MST's require any modifications, perhaps this would be the idea to pursue since you already have four tweeters in each cabinet. A simple crossover change might be all that is required, but who knows?.....maybe you've already got the two capacitor hybrid x-o utilizing all four tweeters.  

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10 hours ago, TimmyTonga said:

There are only about four MST threads on the whole board ...

Perhaps a few more than four ... here is one from a while back with quite a bit of detail including schematics if you scroll down ... they seem to be rare birds or the people who have them don't part with them.

Roger

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OK, boys...here's a hypothetical:

What would you pay for a factory-sealed carton of two AR MST-1 speakers?

And what type of deterioration might one expect after 4 decades in a sealed box? Can we safely assume woofer rot, at the very least? Would the fabric grille be prone to discoloration, or might there be some unfortunate interaction between the walnut finish and the speakers' packing material?

 

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Even though these do not come available very often (particularly factory sealed), I'm gonna pass on the value estimate - - IMO, that is solely between the individual buyer and seller. Regarding deterioration, I'd hazard a guess that both the cabinets and the grilles could very well be in "like new" condition if they have been stored with some care. All brand new AR speakers I have ever seen (exactly one pair :unsure:) were wrapped in heavy clear poly bags with taped closure before insertion into shipping carton, and the MST's (like the AR-7) were packaged two per box. If anything, the foams might be shot, but even those might have survived the decades due to having been mummified in their plastic wrap and sealed box.

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2 hours ago, ar_pro said:

OK, boys...here's a hypothetical:

What would you pay for a factory-sealed carton of two AR MST-1 speakers?

And what type of deterioration might one expect after 4 decades in a sealed box? Can we safely assume woofer rot, at the very least? Would the fabric grille be prone to discoloration, or might there be some unfortunate interaction between the walnut finish and the speakers' packing material?

 

Ok, I would hazard they would sell for $750-1000 just because of the rarity ... now if they were AR-3's look out ;)

Roger

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Hey, thanks Roger, that's a rather unusual listing. Cabinet and grille are a bit ratty, but all drivers appear in surprisingly excellent condition despite questionable re-foam. The cabinet finish is just like the very odd veneer on my orphan, so perhaps these siblings were separated at birth. My favorite part is that deft application of spray paint on rear panel. Pic of mine "as found" is attached.

Alessandro, keep us updated once you peek inside your MST's, and post some pics.

MST front as-is.jpg

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On 5 agosto 2016 at 3:42 PM, ra.ra said:

Hey, thanks Roger, that's a rather unusual listing. Cabinet and grille are a bit ratty, but all drivers appear in surprisingly excellent condition despite questionable re-foam. The cabinet finish is just like the very odd veneer on my orphan, so perhaps these siblings were separated at birth. My favorite part is that deft application of spray paint on rear panel. Pic of mine "as found" is attached.

Alessandro, keep us updated once you peek inside your MST's, and post some pics.

Hi

Here attached post some pictures of my AR MST . By photos and crossover connections it can be seen that there is a single capacitor 6MF dedicated to four tweeters and therefore it is the most simple scheme even if equipped with a three-position switch.

Alessandro

 

AR MST 001.JPG

AR MST 002.JPG

AR MST 003.JPG

AR MST 004.JPG

AR MST 005.JPG

AR MST 006.JPG

AR MST 007.JPG

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Alessandro, thanks for the great pics - - - those MST's are about as nice as they come and they look nearly brand new (and with low serial numbers!). The pic of your crossover which shows four black tweeter wires to a common lug helps me to understand the original four-tweeter MST schematic. However, this is the version that was proclaimed to have the interference problems, and only you can decide if you wish to attempt any modifications.

The thread (which was started by member djcheung) cited above by TTonga shows a revised four-tweeter version, with different cap values, which I assume was a response to the problems of the original model. While it is interesting (to me at least) to see two tweeters wired in parallel and two wired in series, you might be interested to make note of the same print stamp inside your cabinets as is found in the revised pair which says, "Fleetwood Electric LTD". If you note that the revised x-o panel is screw attached, this suggests to me that perhaps Euro four-tweeter MST's were retrofitted with new x-o panels and internal wiring as AR's service offer to correct the initial performance problem.

MST x-o 4 tweet djcheung.jpg

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Alessandro's look the same as the pair I unwrapped a few days ago (inside at least)

MST guts.jpg

 

...except he got fibreglass and I got rock-wool.

I also have what appears to be'13e'

MST legend2.jpg

 

ra.ra, your explanation of the screwed-in crossover as a retrofit sounds eminently plausible, except that Alessandro's pair has the Fleetwood stamp, but not the mod.

Those of us with the 4T models will have to decide whether we want to go for the speaker as is, the hybrid version, or the blanked-out tweet. I asked David Cheung how he was getting on with his hybrid version, and I can't say his response was one of unfettered delight.......interestingly he didn't find them bright enough, but he has a pair of woofers dropped in from a pair of 18s, so it may not be a fair test...

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Dear All ,

Thank you for your interesting and kind support that you are offering me . Currently I ordered new capacitors for 10 mF and 2.2 mF so in the next few days I'll try the 4 hybrid tweeter version and either 3 tweeters version ... then I will tell you my impressions of the sound using my AR 6 as reference speakers .

To your knowledge appropriate use an integrated amplifier Sansui AU Alpha 607 DR . Thanks again to you all !

Alessandro

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Thanks, TTonga, for sharing your new find. I doubt that the cabinet stuffing you've uncovered is rock wool, but I suspect it may be this multi-colored insulation often found in Euro AR's - - - the attached pic was from found on this site, but I don't know if it consists of man-made or natural fibers (fibres?). On the number of tweeters and the wiring, however, I think you are correct - - - there seem to be three options for configuring this speaker model, but it appears there is no majority opinion from users regarding performance evaluations.

My remarks about the possibility of the change in crossover panels is pure conjecture - - am just trying to make some sense of it all. The comment about Fleetwood was a guess to suggest that if Fleetwood Electronics assembled the original crossover per AR specs (single cap), perhaps they were also the service center authorized by AR to fabricate and install the revised x-o (dual cap) and wiring at customer's request.

Question to Alessandro and TTonga, since you each have pairs of original four-tweet MST's, is how do you feel about their performance as they are currently assembled? Do you feel a need to modify them?..... and if so, please explain.

AR euro fill.jpg

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Yes, not Rockwool - but the same as the multi-coloured stuffing in my AR Improved.

I take your point about the Fleetwood situation ra.ra. There are no papers on the back of my MSTs, but the woofers are dated 1974. The MST isn't mentioned in the AR models-in-chronological-order document in the library, but 73/74 must be right as it couldn't possibly predate the first LST. It would be interesting to see what serial numbers Alessandro has on his woofers, considering that his paper certificates confirm them as early models.

When the foam arrives for my woofers and they are up and running I will report, especially on any 'interference'.

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Dear all ,

 

I attach to the installed woofer images in my AR MST and also one of the two and present a label bearing the reference AR 7 .

 

My doubt to change the three tweeters version because I can not find the state a good sound . I try to explain : the sound compared to my AR 6 is more closed and less clear at medium and high frequencies . Basically there is less presence and a symphony orchestra instruments seem blurred and always in the background.

 

Alessandro

 

 

IMG_0669.JPG

IMG_0668.JPG

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The problem I mentioned above may be due to the capacitors that have lost their technical characteristics? I unfortunately do not have suitable equipment for a test and then I'll have to wait until the new capacitors ordered.

 

Alessandro

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It appears that Alessandro's woofers are also dated from 1974 (35th week), so it's quite possible that TTonga's MST's are not that far removed in the production timeline. The factory literature on the MST is rather sparse, but I will share what has been previously been uploaded on the original four-tweet version (by Klaus) and the revised three-tweet MST-1 (by Tom T). I strongly suspect that this "hybrid" version (four tweet, two cap) never merited a company publication since it was most likely a responsive (and possibly embarrassing) corrective measure to an initial performance problem. 

The enclosure volume has been mis-stated in the earlier publication, but corrected in the later version to become consistent with the AR-4xa and AR-6 cabinets volume (18.4 or 18.5L). What has become obvious is that during the early to mid 70's, AR was attempting to hold on to its still significant market share and extend the strong reputation and popular appearance (walnut and linen) of the original "classic' series. At the same time, the engineering and marketing departments seemed to be at odds with each other by manufacturing four different 8" two-way models within a very short time span: AR-4xa (multiple variations); AR-6 (three versions); AR-7; and AR-MST (three versions), which all shared similar parts. 

Alessandro, your description of the unsatisfactory performance sounds like enough reason to try to make improvements. I hope you try both the four and three-tweeter versions with the new 10uF and 2uF caps and report back. And while it is quite possible that the original caps have gone bad, I have recently restored a pair of AR-6's and AR-7's containing the original blue Sprague caps, and because they all tested good after 40+ years, I simply left them alone and the speakers sound great.

MST p.1.jpg

MST p.2.jpg

AR-MST-1 Brochure 03.17.75 p.1.jpg

AR-MST-1 Brochure 03.17.75 p.2.jpg

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6 minutes ago, ra.ra said:

It appears that Alessandro's woofers are also dated from 1974 (35th week), so it's quite possible that TTonga's MST's are not that far removed in the production timeline. The factory literature on the MST is rather sparse, but I will share what has been previously been uploaded on the original four-tweet version (by Klaus) and the revised three-tweet MST-1 (by Tom T). I strongly suspect that this "hybrid" version (four tweet, two cap) never merited a company publication since it was most likely a responsive (and possibly embarrassing) corrective measure to an initial performance problem. 

The enclosure volume has been mis-stated in the earlier publication, but corrected in the later version to become consistent with the AR-4xa and AR-6 cabinets volume (18.4 or 18.5L). What has become obvious is that during the early to mid 70's, AR was attempting to hold on to its still significant market share and extend the strong reputation and popular appearance (walnut and linen) of the original "classic' series. At the same time, the engineering and marketing departments seemed to be at odds with each other by manufacturing four different 8" two-way models within a very short time span: AR-4x (multiple variations); AR-6 (three versions); AR-7; and AR-MST (three versions), which all shared similar parts. 

Alessandro, your description of the unsatisfactory performance sounds like enough reason to try to make improvements. I hope you try both the four and three-tweeter versions with the new 10uF and 2uF caps and report back. And while it is quite possible that the original caps have gone bad, I have recently restored a pair of AR-6's and AR-7's containing the original blue Sprague caps, and because they all tested good after 40+ years, I simply left them alone and the speakers sound great.

MST p.1.jpg

MST p.2.jpg

AR-MST-1 Brochure 03.17.75 p.1.jpg

AR-MST-1 Brochure 03.17.75 p.2.jpg

Hi ra.ra.

Many thanks. I'll inform inform you as soon as possible , after the replacement of the capacitors , about the sound of my AR MST . Unfortunately I can not find the Sprague capacitors , so I ordered the capacitors Audyn MKTA.

Alessandro

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