Preserving iMac G3 speakers with flexible adhesive?

[Schmoburger]

I was just pondering solutions tonight to the recurring issue i have of blowing the deteriorated surrounds out of G3 iMac speakers... My Snow has gone through 4 complete sets now and the opnes on the graphite blew within half a CD worth of music playback with the volume not even close to full. It seems as tho time just isnt a friend of these speakers, shamefully so as they were quite pleasant to listen to for the time.

Among the ides that came to mind was the idea of coating the surround in some kind of thin plastic or rubber polymer, possibly an adhesive, that remains flexible after curing, that will keep the fibrous speaker surround intact... What are the chances of it working, and even if they are slim, can anybody suggest an easily obtainable compound that would possibly do the job? I figure im just going to keep blowing old speakers anyway til i have none left, so i have nothing to lose in trying to prolong the life of a pair in this way before they blow out and are unsalvagable.

 

[MacJunky]

I have never had a set of iMac speakers fall apart and need refoaming. The best advice I have is to stop using them for music and get a nice set of cans.

In no specific order:

http://www.shure.com/

http://www.sennheiser.com/

http://www.audio-technica.com/

http://www.akg.com/

etc (I know I missed some)

And remember to stay away from anything Dr.Dre branded.

Gooing up the speakers may hold them together but you would have to be careful about what you use because that can affect the sound. If you still have your old wrecked sets then you might experiment with them.

Also, can you not use some nice quality external speakers?

 

[Schmoburger]

Yeh I've got a couple of nice sets of Altecs and also a line into my stereo component system amp heheh... I just really liked the sound of the stock HK's back in the day... and for the sake of originality want a semi-functional pair.

I figured if I gooed up only the surrounds with a thin layer of something nice and sticky, at worst it'd limit the excursion of the speakers a little and take some volume out of em. Most of the depth actually comes from the enclosures i found anyway... but yeh ive got a couple of semi-intact but clearly deteriorating ones that i might try on first and see how I go

 

[RickNel]

Funny how when you ask how to fix something, people suggest you get a new one! I'm too stubborn for that. I'm only on this forum because a lot of old Macs are worth the challenge to fix them (at least to me).

You wouldn't want any kind of glue like a rubber solution that retained a sticky surface, because it would collect dust ferociously.

You could try the kind of spray-on bandage you get in pharmacies - it dries to a flexible membrane. I'd first check what kind of solvents might be in it, and avoid anything that could melt the existing membrane, which I'm guessing might be neoprene. But since it's presumably harmless to human skin, it's most likely an alchohol. DISCLAIMER - just speculating.

Have you looked at audio or vintage-audio forums for tips?

Rick

 

[Schmoburger]

Yeh an audio forum was my next port of call for this one... ive heard of regluing seperated surrounds to cones on large speakers with a flexible speaker glue, which i did to a JVC subwoofer with a butyl surround, however in that case the surround was intact, but never heard much about repairs being done with speakers that have deteriorating or punctured fibrous surounds... tho at a guess it's probably possible. Just not sure how possible on something as small as an iMac speaker... :?:

I'd never actually known about spray-bandages before, but youre right, it'd presumably be a fairly mild cocktail of chemicals if it's intended for use on human skin... might check it out next time im near a chemist. At worst if I put it on a damaged set of speakers and it disolves the surround, i havent really lost anything but a few minutes of my time as the speakers were otherwise junk.

But yeh I used to just be of the R+R school of thought myself back in the days before electronics recycling was a big dollar business, when for a lot of items it was easier just cheaper and easier to replace whole items or subassemblies with good ones that were readily available either secondhand or new. The problem is tho, there is a finite and dwindling supply of servicable parts out there for many pieces of equipment, and many of them are deteriorating themselves with age and/or use (a good example being iMac speakers and compact anny boards), so repair and restoration on a component-level rather than just assembly-level old-for-old replacement to me seems far more favourable. I actually started to think this way when I realised that my 2000cc VW Type 4 engine from my '76 Kombi were actually getting to the stage where it was more financially viable to spend the money on items to rebuld it than it was to source a secondhand replacement that may or may not remain in servicable condition. Same with my original busted gearbox out of it... it'd cost me 600 bux for a servicable replacement of unguaranteed life-expectancy vs about 1300 for a full rebuild of the old broken one to as-new condition. And now it's really the same with old computer parts....

 

[Trash80toHP_Mini]

I've been reading about these speakers for what seems like forever, but don't recall seeing pictures offhand. Google pics didn't help and I'm assuming that the exploded diagram in the service source shows only the complete assembly, not the component(s) in question.

I'd love to see shots of the failing parts sans electronics and housing. I'm wondering about possibilities like replicating these membranes with the likes of tool dip materials.

 

[Schmoburger]

I'm actually pulling the 5th? trashed set out of my Snow at the moment, so I shall get some pics up for you ASAP.

There's actually very little to them inside the enclosure, as most of it's bulk is purely for acoustic considerations.

Theyre theoretically supposed to be a sealed unit, and presumably as far as Apple is concerned, a non- servicable component like the Yoyo adaptors, however the two halves of the shell are actually just glued together in the factory with a non-hardening silicone-like compound and a single screw down the middle... Remove the screw and with some careful prying it is relatively easy to get it apart, revealing what from memory is quite a basic loudspeaker assembly.

I actually had a set I had dismantled already but cant remember where I put them.

 

[Trash80toHP_Mini]

Now that you mention it, plaster casting clear silicone caulk might be a winner! [}] ]'>

 

[Schmoburger]

So, here is the complete RH speaker assembly... for most purposes we'll say it's intact.

This one has simply had the complete intact membrane and motor unit break away from the outside of the basket...

This is a severely rotted one that has had the entire surround membrane disintegrate during operation...

This is one of the other speakers that i replaced in the past after it began to fail... there is a lengthy split in the membrane on the side adjacent to the sound port...

This is the screw that must be undone and silicone bead that must be parted to facilitate disassembly... this particular one was easy, didnt need to pry it apart at all, just pulled apart in my hands with minimal fuss, and no need to remove the sealant at all...

And here it is apart. The speaker is simply glued to the lower portion of the enclosure and can be carefully pried off with a screwdriver... note the presence of spade connectors. I've tried disconnecting them as an experiment but it seems the force required to get them off would destroy the speaker as theyre on quite tightly...

And here's the fairly basic innards of the speaker. Interestingly the motor unit is suspended over an internal magnet by the front membrane and voice coil leads alone, with no spiders. As an asde, I have also just realised the entire motor unit and membrane actually lift off the magnet... this could be handy. Note that the coil leads are particularly fragile and break easily off the coil...

So... there we have some food for thought. With some careful precision and ingenuity it could be possible to actually replace the surrounds, but more importantly it seems to be a piece of cake to disassemble the actual speaker to a point where a semi-decent surround could be easily repaired.

 

[Schmoburger]

So... I set about undertaking some exhaustive digging last night for a suitably sized and reasonable quality replacement for the original HK speakers, and after plenty of frustrating dead ends, I came across what with any luck should be able to be fitted as a direct replacement into the HK enclosures (which are an important factor in getting so much sound out of so small a driver) with minimal modification if ive done my math right... and best of all, when fitted they would visually be indistinguishable from the stock speaker, as they have a metallic parabolic cone like the HK's. I tracked down a relatively local supplier so I intend to order one to experiment with and see how I go... will keep y'all posted.

 

[Trash80toHP_Mini]

So the membrane is circular, that's a relief. I thought it was a teardrop kinda deal with a large surface area.

Is it something simple enough that a female mold for the face and sides could be turned on a wood lathe?

I'm thinking along the lines of:

squirting silicone caulk into the mold with excess built up . . .

. . . letting it dry . . .

. . . cutting the excess off the flat(?) backside . . . erm . . . flat

. . . peeling the finished part out of the mold?

Is the original part cast around the solenoid, using it as the core of the mold?

Can it be? That might make it even easier to make replacements. :?:

Just spitballin' here, never saw or touched one IRL, obviously.

 

[RickNel]

Wow! Those rotted rings make me wonder what kind of solvents were floating around the atmosphere where those particular iMacs lived. I'm imagining lots of chlorine, maybe hydrocarbons?

AFAIK those rings don't have any critical audio characteristics, they just have to support the diaphragm through the full distance of it's potential stroke, maintain the seal to the rear chamber, and return to neutral. However, they could be pretty hard to get right if trying to build one from a mould.

Very similar speaker units have become quite common in portable iPod extension speakers, often surprisingly cheap. Sadly, replacement might turn out more feasible than repair, at least where the rings are significantly rotted.

Rick

 

[Schmoburger]

Mmmm a lot of my units came from the public school system so dunno if its anything to do with something used in and around those environs... that said, I've even had a couple I got from other sources that were similarly deteriorated, tho admittedly the school ones were the worst. I'm interested to know if the similar 1 inch drivers used in the early Harman Kardon Soundsticks have suffered from the same kinda deterioration with time and use.

But yeh some of these units ive got are probably way too far gone to be a viable repair option... the ones with the surround blown clean out like the one i dismantled for the photos, in all honesty i personally wouldnt be inclined to attempt a repair on. However I cant help but think there could be a sporting chance of stabilising and preserving the integrity of old but intact units, or repairing units that have started to split or have completely seperated leaving the whole ring intact... I guess for what its worth trial and error is the only way to find out. For what its worth i have plenty of duds to work with

The more I look at it tho, the more I am thinking replacement could indeed be the most viable long-term option, providing I can get replacements of an adequate quality in a size that will fit. I've actually thought about using the ones from the little cheap ipod docks with the alloy or chromed plastic cones, tho tbh I havent been entirely satisfied with the sound quality of most of them, and more importantly, they are generally about half an inch to large in diameter, so it'd be difficult to modify the enclosures to fit them in a neat fashion and still maintain the acoustic qualities that HK so carefully designed into them.

The ones I'm looking at as possibly being the most suitable and viable long-term replacement are, funnily enough, a high-bass metallic full-range driver designed for use in model railroad audio systems... took a long time to actually come up with anything that was remotely suitable but these seem to fit the bill almost perfectly on paper, and are a similar (tho at the same time completely different) design to the factory iMac speakers, such that when installed (assuming I can get em to fit), they would visually be near-indistinguishable from the factory speaker drivers. The supplier I called up about em (one of only two in Australia) is retailing them at just under 20 bucks apiece.

 

[uniserver]

i think its the techno is whats killing them

my buddy used to repair subwoffers.

When the voice coil would start to rip or bust through the paper cone in the center.

I know how he did it... i jus don't know how he did it if you catch my drift... i guess it was his love for music?

He would use construction RTV, he tried the blue kind but ended up using the black kind because it was more rigid when it was fully set up

for suspension he found that a ploy/cotton carhart work shirt had the best material. he used the sleeves because he cut off the sleeves any ways.

Anyways he would cut the fabric into strips and coat the fabric with that black rtv on both sides, he would apply it over lapping onto the cone and the neighboring suspension, if it was just repair, then kind of form the fabric with his finger So it looked and took the same form as the neighboring suspension, then he would let it sit over night.

Because it was just BASS, you really couldn't tell, other then it sounded way better then it did before he fixed it.

I do know the spots with the RTV were less flexible when he switched to black from blue. but the black held together.

mind you this was 18 years ago... DAMMM wow... head hurts.. realization i am getting old... :-(

 

[RickNel]

I believe you about techno! School computerlabs->techno->ripped cones.

I also love DIY hardware hacks, but there's orders of magnitude between subwoofers and G3 Harmon-Kardon speaker pods.

Schmo has been looking at replacements. There is a cheap "Hamburger" mono iPod extension speaker that turns up in discount catalogues at very low prices (~$5 on ebay) - the speaker unit is very similar size and construction to the G3 H-K, IIRC. That's what I would look at first because it is a reasonable full-range unit. The H-K gets a performance boost from being in that spherical sealed pod, and the hamburger should also sound pretty good in that mini-enclosure with the inertial mass of the G3 chassis.

Rick

 

[Trash80toHP_Mini]

mind you this was 18 years ago... DAMMM wow... head hurts.. realization i am getting old... :-(

HEH! : Whipper snapper! I remember watching Lawrence Welk on B&W TV, not to mention changing out the tubes (no, not the CRT [] ]'> ) from the test station/display rack with my daddy at the dime store!

My rug rat turned 28 yesterday . . . so I told him he was closing in on half my age. } :lol:

 

[uniserver]

I'd like to own something with all vacuum tubes one day.

Maybe a radio.

or maybe a:

____VOICE - CONTROL

BATMOBILE RELAY - CIRCUIT

 

[Schmoburger]

Hmmm hadn't come across those hamburger jobbies ye in my travels, but they sound like what i have been looking for... may have to see about sourcing some for testing purposes iif nothing else... perhaps hack them to fit one iMac, and try the other ones in the other iMac to draw a comparison.... ah the joys of having multiple iMacs

And yeh for what it's worth I guess if these factory H-K's had a finite life-expextancy anyway then the high school computer lab environment of the early 2000's would make for some of the most brutal failures... I remember in 8th grade computer studies back in 2001 in... the intrinsic novelty value of shiney new Macs with awsome speakers resulted in just about every lesson having "Kill You", "Purple Pills", "The Next Episode", "Sandstorm" and all that hectic bass-heavy music bellowing over the top of it the moment teach left the room. That kinda thing certainly couldnt have been kind to em.... In saying this however, the ones from the primary school next door to my house (my SNow being one of them) were all in the same state as well, and I cant imagine that they would have played too much Eminem, Dr Dre or DaRude throught them in their time. Well at least I hope not or my faith in the public school system may have just waned a little more. :lol:

 

[Schmoburger]

I have a couple of tube radiograms and had a Kelvinator portable AM tube radio set actually until my sisters moron friends knockecked it of a shelf and smashed the bakelite case in a drunken spate of debauchery one night > .... My dad used to be a technician with AWA for many years so i grew up exposed to all that kinda old-school tech from a young age and there's a bit of it to be found round out parts.