AR-MST

[owlsplace]

At least you don't have to deal with pots!

Interesting to see the crossover boards attached with screws.

Roger

[ar_pro]

What's going on with the solder lug indicated by the red arrow?

Had a wire been previously connected at that point?

Also - that's a ton of glue on a hand-labeled board, attached, as Roger noted, by wood screws.

Could this have been a prototype, or some sort of one-off?

[ra.ra]

Good eye spotting that lug, but despite its odd orientation, it still connects only the two leads from the black wire and the 2uF cap, so it is functioning similar to the other speaker. About the glue - - it never fails to astound me how sloppy these crossovers are sometimes assembled, but AR's have never been lauded for their beauty "under the hood".

Your mention of a possible prototype or "one-off" occurred to me as well, but since the MST is such an oddball (and unsuccessful) product model that was introduced during a period of significant company transition, the corporate paper trail may simply be insufficient to document and confirm this particular iteration. The speckle-paint on the cabinet backside is something I always associate with Euro AR's, but the orphan MST cabinet I found last year in Boston has the same finish (?).

Indeed a mystery.

[iso]

About the glue - - it never fails to astound me how sloppy these crossovers are sometimes assembled, but AR's have never been lauded for their beauty "under the hood".

Probably same team made 1976 Dodge Coronet I used to have in the 80´s... there was enough seam sealer in the trunk for assembling two full size cars.

Best Regards

Kimmo

[owlsplace]

I have a vague memory of TomT mentioning AR using the Euro market as a sounding board. They seem to have some nice teak AR-7's over there

This MST set definitely looks unusual. I didn't think the original four tweeter version was released in Europe though.

Roger

[djcheung]

One of my friends ( another AR enthusiast ) who has a couple of the AR7 woofers.

I am just waiting and hoping the price is right and he is willing to part with them.

[ra.ra]

Those woofers look like perfect candidates - - good luck with the negotiations.

[djcheung]

My friend has decided to keep the woofers.

So, a long wait for some to turn up.

I have missed a couple of AR7X but I didn't want to pull the woofers out from a pair of fully functioning speakers.

Now, for a quick test, I connected the seas woofers in and they sound ok but very bright.

Overall the bass response is a bit thin, not too sure whether it is because of the refoam, woofers or/and the gaskets.

Not really know what to expect from them.

Any glues to what to look for in terms of that 4 tweeters interference ?

[djcheung]

Well, disaster struck.

5 minutes into the listening, one of the woofers started to rattle.

I was pretty sure that the refoam was done properly and the VC wasn't rubbing.

Took the woofer out and the rattle is there when I shake the woofer.

An then the whole VC started to rub quite badly.

I quickly found another pair of non-AR woofer and replaced them.

At the same time I removed the not so perfect gasket and replaced it with foam strips.

Will post some pictures tomorrow.

In my last message on the last line, it should say 'Any Clues' and not 'Any GLUES'

[tysontom]

Probably same team made 1976 Dodge Coronet I used to have in the 80´s... there was enough seam sealer in the trunk for assembling two full size cars.

Best Regards

Kimmo

Kimmo,

Ha, ha, you '76 Coronet story brought visions of our '76 Dodge. We had a 1976 Dodge Aspen station wagon (upscale model we ordered with a special-option 360 cid engine), and it was a really great, quick and comfortable car. The body was poorly assembled, however, and I learned later that Chrysler products of that era were prone to lower-panel corrosion. It didn't happen to our car, fortunately, and it ran faultlessly for several years with one exception: it never idled smoothly, and the dealership tried in vain several times to correct the problem. Finally, I went to the dealership owner (the car had over 60k miles on it at this time and was well out of warranty), and we had a serious talk about the long-standing problem. He called Chrysler Corporation, and they sent a regional rep in to the dealership, determined that the camshaft and intake manifold were out of spec, and they completely rebuilt the engine -- free of charge.

The Dodge story doesn't do much for the woofer problem in the MST! Those MSTs will have to have the standard 8-inch AR woofer to work properly. Any substitute won't cut it, although a woofer out of the Allison Model Four might work okay, as it has a similarly low resonance and long excursion. Yet, to get the system to match in terms of sensitivity, smoothness and so forth, the woofer designed for it is the one that is needed, pure and simple. The AR-7 woofer has a slightly higher resonance (in its early iteration), and it had a smaller diameter skiver (surround), but later ones used the universal 8-inch version. This is the woofer you should try to find for the MST.

The speckled back panel is definitely a Euro model; none of the US versions were sold this way, but a lot of the European-built (Britain or Holland) versions have made their way to the US.

--Tom

[djcheung]

They used staples, yes staples, to hold the gasket down.

[iso]

Kimmo,

Ha, ha, you '76 Coronet story brought visions of our '76 Dodge. We had a 1976 Dodge Aspen station wagon (upscale model we ordered with a special-option 360 cid engine), and it was a really great, quick and comfortable car.

--Tom

Tom,

I agree, Aspen was nice car, but these were not too great years for Pentastar. When I bought my Coronet with 360 cid small block engine I got wet feet as foam like seam sealer was rotting cowl area badly. It was 10 year old car as my funds were not too great these days. Car with HD suspension handled well... after I had readjusted steering gear, camber, caster and toe in for more spirited driving habits and replaced every suspension ball joint and rubber bush. Brakes faded easily as they were same as for slant six Aspen. On the other hand there were some strong points too... rubber hoses of emission gear lasted forever, distributor was work of art. If you look at centrifugal advance mechanism, it should last forever if you remember lubricate it sometimes. And I like Chrysler slogan "rear end suspension like in big cars" in Aspen advertising material. It was miracle how Chrysler engineers were able to tweak performance out of this crude rear end suspension. Truly nice ride on smooth surface... but I do prefer Jaguar on rougher roads.

But anyway... I was trying to wake your interest earlier when I asked "I hope that someone does have some inside information why side firing tweeters seems to have different crossover slopes compared to direct firing tweeters". Was general idea to match HF directivity to directivity of 8" woofer or was there some other reason for this arrangement?

Best Regards

Kimmo

[djcheung]

I have ordered some Solen caps and that will be the first task if they arrive this weekend.

Does anybody know how the cabinet should be stuffed (loose or sheet of wadding) and what is the weight of the wadding?

There is only one very thin piece of wadding packed loosely in there.

David.

[djcheung]

I was curious about what is causing the noise in the Seas woofer.

So out with some tools and 10 minutes later.

[owlsplace]

OK, was it glue fail or was it damaged from bottoming out? There are guys out there that wind there own vc's but doubt it is worth the effort in this case.

[djcheung]

There were bits and pieces of metal fragments left in the gap.

It looks like the bottom of the voice coil disintegrated.

I don't think I have done that. Didn't turn it up too loud.

Even with the working one, they don't have much bass response.One for the bin.

Opened it up just to practice shimming as I haven't the need to shim any of the speaker refoam so far.

Found an old pair of AR18EJ in my collection and the woofer just so happen to be 200001-1.

I think they are the right woofers.

And they sound much better than the Seas.

Now I am left with a pair of AR18 without woofers.

First listen located away from the back walls are very clean.

Bass response may not be as low as say AR14 or AR6 but the tweeters are quite good (caps not arrived).

I am not too sure how to identify the interference with the 4 tweeters version. I am not hearing anything odd at the moment.

Any pointers?

I will get some pics when I get a chance,

David.

[owlsplace]

There were bits and pieces of metal fragments left in the gap.

It looks like the bottom of the voice coil disintegrated.

I don't think I have done that. Didn't turn it up too loud.

Even with the working one, they don't have much bass response.One for the bin.

Opened it up just to practice shimming as I haven't the need to shim any of the speaker refoam so far.

Found an old pair of AR18EJ in my collection and the woofer just so happen to be 200001-1.

I think they are the right woofers.

And they sound much better than the Seas.

Now I am left with a pair of AR18 without woofers.

First listen located away from the back walls are very clean.

Bass response may not be as low as say AR14 or AR6 but the tweeters are quite good (caps not arrived).

I am not too sure how to identify the interference with the 4 tweeters version. I am not hearing anything odd at the moment.

Any pointers?

I will get some pics when I get a chance,

David.

You may be able to get some additional bass by adjusting the stuffing. The tweeter interference problem was in the original crossover I believe. Yours have the second version crossover plus an additional tweeter which makes them somewhat unique.

There is a pair on the auction site currently but I don't have the spare change or I would join in the fun.

Roger

[djcheung]

Now I have found and replaced the woofers.

The next task will be tackling the grille cloth.

Some people just do not have any clue to what they are doing.

They should bot be allowed to touch them !

Roger,

What do you mean by 'adjusting the stuffing' ?

The existing stuffing is very thin and is loosely lay over the XO.

What weight should it have?

David.

[owlsplace]

....

Roger,

What do you mean by 'adjusting the stuffing' ?

The existing stuffing is very thin and is loosely lay over the XO.

What weight should it have?

Carl or RoyC would be better able to advise on this issue. Robert may also have some info since he has one. I'm guessing somewhere between 10-13 ounces but could be totally wrong.

[ra.ra]

MST cabinet is same internal volume as AR-4x - - - see this thread by Kent where he discusses amount of stuffing in 4x. After you've tweaked it to your satisfaction, please report back with details (and pics?) of process and LF performance.

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=8451

[djcheung]

Just ordered some damping material for the cabinets - Monacor MDM-3 Acoustic Damping 75% Wool/25% Polyester.

Hope they will arrive this weekend so I can do the caps at the same time.

'Finish' on the cabinets.

I have applied some finishing oil on the top of a pair of ARUK1 - similar to AR94.

I quite like the glossy finish.

What do you guys think if I apply it to the MST?

David.

[ra.ra]

More random feedback here.

Woofers - too bad you were unable to obtain the AR-7 woofers, but these 001 'universal' woofers should at least offer a family resemblance, musically speaking.

Grilles - can't quite tell, but I assume you have the hinged three panel grille frames (see pic) underneath that black cloth. Also hard to tell, but the cloth appears to perhaps be a bit dense - - has this material been used successfully for this purpose?

Stuffing - that Monacor material looks pretty good and one package appears to contain (2) blankets (approx. 13" x 24" x 1-1/2"), but it's difficult to know how much will be required. Certainly, you could supplement this new material with the original grey-ish multi-color batting that shows up in post 36, which is a typical component found in many Euro AR's.

Cabinets - my single orphan MST has a very strange veneer on it that is not very attractive - - see close-up image of MST (right) next to walnut AR-6 (left) I am currently working on. On the MST, the grain structure is overly uniform, the texture feels almost artificial, and the color is lifeless - - - it looks nothing like my other walnut AR's. Your speakers appear like they may be more appealing with regards to veneer, and since you are asking for comments, that finish is far too glossy for my own personal tastes. I prefer something closer to a 'satin' sheen, but if you like the high gloss, that is all that matters.

Interference - I had hoped for more knowing minds to contribute to this topic, but it is possible that this previously problematic issue is no longer valid. Your speakers have the crossover design which allows the front and side tweeters to respond differently, and that just may have been enough tweak to cure the earlier performance issues.

[djcheung]

Thanks ra.ra

I think the universal woofers is still far better than the Seas or PCL woofers that I have lying around.

Their bass response is actually very good.

The grille is the hinged ones like the one in your pic but the cloth material is a bit like wrapping material and it does affect the high frequencies when installed.

I will try stuffing more of the damping material and check.

I have used BLO on some of my projects before but have found that it takes a long, long, long time to dry properly.

I didn't take any pics of the top and bottom panels an I can't remember how they look. Will take some this evening.

Once I have replaced the caps and more damping material, I will listen to them more serious and see if there is any odd interference.

I have noticed some funny strange phenomenon.

When I listen to these speakers, I get a far better bass response when I sit in the next room.

They actually sound much bigger than what they are.

David.

[ra.ra]

Yes, having some authentic AR woofers is certainly your best solution, and I suspect the performance of these 001 woofers will be virtually indistinguishable from the AR-7 woofers with flat dust caps that you showed in post 31.

As you know by now, the available documentation on the MST(s) is not as thorough as for many other AR models, but the cabinet stuffing is every bit as important as with the other successful small 8" speakers. In all of the small models (AR-4, 4x, 4xa and 6) of a similar volume, I have only witnessed cabinets that are essentially stuffed full to fill the cabinet void.

Re: linseed oil, there has been a great deal of chatter in some recent threads about this finish. My experience is to always thin it with mineral spirits, turpentine, or japan drier to effectively reduce the drying time, and it is also helpful to lightly rub down the cabinets between application coats.

Re: high frequencies, glad to see you'll be replacing all of the caps, but you may also want to think about finding a better option for the grille cloth. Not only do you want to find a fabric that is more acoustically transparent, but an 'off-white' or 'oatmeal' color will help to achieve that classic AR look that remains timeless and is friendly with many home decor schemes. Hoping to direct you to a thread by RobHolt in the UK, I see you both have already been over this issue at least once.

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=8431&hl=

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=8011

Once you get things re-assembled, please report back on performance and general observations, including the effectiveness of the 3-position tweeter switch.

[owlsplace]

I am left wondering how these would sound hung vertically with one tweeter firing up, one down and two forward -- sounds a bit like some of the new speakers they are coming out with

If you can't figure out how much stuffing to use just pack it full and take a listen. Then take some out from behind the woofer and listen again....

Roger