AR9LS Refoam question

[cd0nc]

I've recently purchased a set of AR9LS speakers.

I've noticed after taking out the 8" drivers the spiders sit flat against the basket rather than raised up like in previous AR speakers I have worked on (9, 90, 91, 92, 94, 18 etc).

There is also a hole in the middle rear of the driver which I have no idea what it's for. The outer dustcap is a screen mesh and I'm not going to remove the dust cap for a change as I'm not sure what's underneath on these speaker or if they need to be airtight like all the previous drivers I have worked on.

I want to try either a tone generator or a battery method to keep the VC centered while I glue the surround.

What's the correct position to have the cone in when gluing the outer foam surround to the basket on these? Are the surrounds different to others in the series? I've been buying lots of different 8" foams which have the dimensions used by AR foam sellers on eBay and they seem to have a bit too much inner roll when placed around these 8" cones.

[AR55]

The AR 9Ls 8in midrange spider does lay flat; the plugged hole in the rear plate is normal; the screen mesh dust cap is standard and the inside flange of the foam surround attaches to the back of the cone.  See attached photos.

[ra.ra]

On 4/16/2018 at 8:00 AM, cd0nc said:

There is also a hole in the middle rear of the driver which I have no idea what it's for.

Not quite sure what you mean by this statement, but everything else that you and AR55 have noted suggests this is AR part number 200050, which was also used as the woofer in the AR-28b, as shown in my pics here. And yep, the spider is installed flush with the rear flat portion of the metal basket. You can see in this pic that the stiff paper cone has a seam opposite from the wire leads; and when I re-foamed, I hinge cut the original dust cap in order to shim the VC, and then carefully glued it back in place. This procedure is a little bit delicate, but not particularly difficult, and I found it very helpful to be able to shim and hold the cone in the "up" position when gluing the inner foam under the cone.

[cd0nc]

So I've got four of the 200045-0 drivers, two have come out of AR98LS speakers (pictured). The ones from the 98LS were pretty rusty and corroded.

I've cleaned the top and insides of these and dyed them a nicer shade of black.I won't be doing this with the AR9LS ones as they are in much better shape. The 11" ones are up for debate as to if I need to dye them the same color.

The next part is coating the metal with a protective coating.

After that it will be re-foam time. From the suggestions I should shim them but I'd rather try and use a battery or test tone to bring the cone up and glue them in that position as I think they are dual dust caps and I find the fabric ones a total nightmare to detach without replacing them. Once they are re-foamed I'll clean the undersides and give them a protective spray too.

I think there was a coating of glue on the 8" cones which gave them a slightly shiny appearance. Since they were dirty I cleaned them with isopropyl alcohol as I figured it out dry quicker. This seems to have taken off the coating, there actually went a shade of cream before I dyed them. Is it worth trying to re-create the coating?

[ra.ra]

Thx for sharing the great pics. I looked up the drawing for the 045 driver (lower midrange), and by every appearance it is fully identical to the 050 driver (woofer) in my pics. However, the critical moving parts (spider/coil and cone/surround) have different designations, so clearly these components were tweaked to complement their respective cabinet enclosures. The two drawings show the same date (April '82), and the 045 was used only in the two models you have mentioned.

No idea what the hole in the magnet is about. The section drawing for the 045 driver (attached) does not show any void at this location.

Re: dust cap and shimming, I did not like having to cut and re-glue this cap but it was the method I chose and it worked for me. It's entirely possible you will have equal success with another method. And while it is true that some 8" AR drivers have a dual cap, this particularly woofer/mid has only a single dust cap, even though the drawings list this item as "dust cap, appearance".

I've never seen so much corrosion on a metal basket as your 12" drivers have, and it would be my assumption that that indicates improper long-term storage and/or prolonged exposure to a harsh atmospheric environment. The clean-up of your 8" basket looks terrific, but they really should not require a protective spray coating. If you choose to do so, I'd recommend not coating the basket rim where the outer foam perimeter gets glued to metal.

[Analogman]

Use a 30 Hz test tone while re-edging and forgo the need to cut off dust caps on these fragile old drivers

Works well

The hole is (may be) for cooling, à la JBL - shine a bright light into them while observing the front of the cone (dust cap)

If you can see any sign of light then that's definitely what they are - spares the VC and former as well as helps up the power handling of the driver

Not a bad idea to glue a bit of screen mesh over them after you're done with your repair and before you put them back in the cabinets

If they are cooling ports for the VC, trash can migrate into the gap - that's why you see a screen over that hole on JBL drivers 

Craig

[RoyC]

1 hour ago, Analogman said:

Use a 30 Hz test tone while re-edging and forgo the need to cut off dust caps on these fragile old drivers

Works well

Craig

Not always, Craig. I just re-foamed two AR 10 inch woofers for a person who unsuccessfully used this method. The primary issue is not having the ability to adjust the height of the cone during the process. Friction provided by shims allows for this adjustment. Older woofers with soft suspensions, and lower cone heights (relative to the basket) should be shimmed, imo.

As I've mentioned before, the DIY "test tone" method has been good for Larry/Vintage_AR's repair business.

Roy

[Analogman]

15 minutes ago, RoyC said:

Not always, Craig. I just re-foamed two AR 10 inch woofers for a person who unsuccessfully used this method. The primary issue is not having the ability to adjust the height of the cone during the process. Friction provided by shims allows for this adjustment. Older woofers with soft suspensions, and lower cone heights (relative to the basket) should be shimmed, imo.

As I've mentioned before, the test tone method has been good for Larry/Vintage_AR's repair business.

Roy

I hear what you are saying and agree 100%, and of course there is nothing in this world (involving machines) that is ever the answer 100% of the time

Speakers with worn out spiders get a re-cone (with new spider) rather a re-edge on my bench (if it is a job I have to stand behind)

The 30 Hz method works beautifully on otherwise healthy drivers only in need of a new outer suspension - I thought that would go without saying

Excursion, and outer cone lip at rest height in relationship to the basket flange is easily adjusted on a case by case basis and is perfectly compatible with the test tone alignment protocol - I would have thought that too would have gone without saying

Regardless, no matter the method used, if the spider is sagging it's still going to sag whether you used shims or not and the end results is still a patch job - may last a week, may last another 20 years

Aside from the fact that the outer suspension's job isn't (should not be relied upon) to establish and maintain the former's relationship to the back plate at rest because as you well know, that's not going to last for long (those DIY re-foamed woofers that "knock" or "tick" when you play them loud! : - )

I don't like having to revisit work anymore than the next guy - I have done many dozens of drivers with the 30 Hz tone technique and to my knowledge not one has yet to fail or suffer any problems (knock on wood : - ) and most definitely none of my personal drivers have

I also agree with you that more than a few do-it-yourselfers have hacked up their woofers

Craig

[RoyC]

11 minutes ago, Analogman said:

Excursion, and outer cone lip height in relationship to the basket flange is easily adjusted on a case by case basis and is perfectly compatible with the test tone alignment protocol - I would have thought that too would have gone without saying

Craig

Really...so how do you accomplish that?

My primary point is shims make it easier to manipulate the cone while gluing, not that the final cone height is somehow more accurate...and that an inexperienced person is more likely to be successful using shims. I've also had this conversation with Bill LeGall of Millersound, another shim guy.

Roy

[Analogman]

9 minutes ago, RoyC said:

Really...so how do you accomplish that?

My primary point is shims make it easier to manipulate the cone while gluing, not that the final cone height is somehow more accurate...and that an inexperienced person is more likely to be successful using shims. I've also had this conversation with Bill LeGall of Millersound, another shim guy.

Roy

A straight edge

And I understood your point; was not saying there was anything wrong or invalid with using shims, and I do, on re-cone jobs

But like I said, I don't (just) re-edge drivers with worn out spiders, at least not for others

I have been guilty of "patching" a few for myself

Craig

[Stimpy]

7 hours ago, cd0nc said:

So I've got four of the 200045-0 drivers, two have come out of AR98LS speakers (pictured). The ones from the 98LS were pretty rusty and corroded.

I've cleaned the top and insides of these and dyed them a nicer shade of black.I won't be doing this with the AR9LS ones as they are in much better shape. The 11" ones are up for debate as to if I need to dye them the same color.

The next part is coating the metal with a protective coating.

 

 

 

You did a beautiful job with the cosmetic improvement of this LMR.  If possible, could you go into detail, describing the dye used, and the application method?

Thanks.

[cd0nc]

15 minutes ago, Stimpy said:

You did a beautiful job with the cosmetic improvement of this LMR.  If possible, could you go into detail, describing the dye used, and the application method?

Thanks.

I accidentally removed the coating when trying to clean them with alcohol, so this step is optional  

The finish after doing that was without dye on the cone and possibly lacking a clear coat on the top. I'm unsure if they used a protective coating or the yellow stain I took off was cigarette tar - pretty sure these were used for live music somewhere.

After that I tried two different types of dye. Originally I bought some with salt in as it was being sold off cheaply - this was a mistake. The salt sits on the surface of them and makes them look patchy. In the end I bought the hand wash version of the same brand - Dylon, I think it was intense or velvet black.

I mixed a table spoon of this with ~125ml water, at about about 60deg C, with about another 25ml of white vinegar. After stirring I did very thin layers about a few hours apart. I would avoid using the dye mixture after about 24 hours later and make a fresh batch if needed to avoid crystals forming.

I did try doing some other AR94 drivers with grey Rit dye, this came out patchy but I figure I didn't use enough and might give them another go at the weekend as they are at my parents house. Drivers on both my girlfriend's and parents dining room table at the moment so need to get a move on.

The 11" drivers are looking a lot better now sans rust. The 98 LS cabinets are in a right mess, I think they were kept in a barn. A lot of the speakers I buy here in the UK have been stored in less than ideal conditions since space indoors is at such a premium here.

 

[cd0nc]

54 minutes ago, RoyC said:

Really...so how do you accomplish that?

My primary point is shims make it easier to manipulate the cone while gluing, not that the final cone height is somehow more accurate...and that an inexperienced person is more likely to be successful using shims. I've also had this conversation with Bill LeGall of Millersound, another shim guy.

Roy

I've got some of his 10" surrounds to try on some AR90s at home. I shimmed the midranges on those. Unfortunately one of the coils is dead on them - I didn't check before starting the repair so wasted on the 8" surrounds I bought to do those. Luckily I have a spare set of LMR drivers from some AR94s so I have a matching pair to replace them still. I want to try some of Rick Cobbs on the AR9 LS, just need to save up some more to import those. The 98 LS are going to get whichever turn out to be the best of the china / Australian bunch I have incoming.

52 minutes ago, Analogman said:

A straight edge

And I understood your point; was not saying there was anything wrong or invalid with using shims, and I do, on re-cone jobs

But like I said, I don't (just) re-edge drivers with worn out spiders, at least not for others

I have been guilty of "patching" a few for myself

Craig

Craig, I have a 10" and now an 8" dead AR driver both due to VC issues. I think if I can cut them apart I can savage the cone and just replace the VC and spider.

I have no idea how to measure for replacements. Am I trying to find spiders with the same dimensions and voice coils with the same impedance and size as the originals? Seems a waste to get rid of them if I can repair them. Do you recone as a pair or is it a fairly good match to not have to?