I just literally stumbled on a pair of Quantum 3s (QLS-3) sitting on the curb this morning (trash day here, a neighbor threw them away). They are in pretty good shape; no grills, foam surrounds shot on woofers, but otherwise mostly okay. I find many sites that sell those kits if there is nothing serious to watch for?

Secondly, the Dome Midrange speakers (#902-0206) are different looking between the two cabinets, so I presume one has been changed out. The one I believe to be original does not work. The non-functional one has two wires going into the dust cap; well, one wire really, one broken, which is why I presume it does not work. I am very much a neophyte and am not sure about the repair on this one...? Hints? Cut the cap, re-solder, re-cap?

pdf diagrams (http://www.anello.de/download/Quantum_3_technical_sheet.pdf
)

I appreciate any pointers or advice...

Thanks,
Bill

Hey there Quantum 3. I like that moniker :thmbsp:

Welcome to AK, and that is quite a curbside find. Sounds like some challenges ahead to get these working, but you should find some help here.

Have you used the search function yet? You should be able to find quite a bit posted here on the Quantum line of speakers. Try QLS, Q1,Q2, etc. Quantum, Infinity as key words. Search out my name, Charivari, Sicman and you'll find posts on these Quantums. After absorbing everything here, come on back with specifics to get the discussions going.

The Woofer foam. Flat mounting style is a must. Measure the existing cone for the inside diameter of the flat flange on the outside of the cone. Depending on your location, I found an excellent source in Northern Canada where I got a perfect fitting set of foams. Let me know if you are interested. I'll repost with the dimensions I used to get the foams.

There are a a few (two that I know of) guys here who have repaired the broken tinsel leads on the mids. Your search should reveal the perpetrators :D

Look forward to following your progress on the Q3's.

ANY PICS ??????

Quantum 3,

I've measured the cone dia to be 9"at the break away to the flat
mounting flange. So the foam ID needs to be maximum 9" . The roll ID
is about 9-3/8" to 9-7/16. The foams I used had 1/4" inside flange so ID to the roll was 9-1/2", and the overall ID was 9".

You'll want new cardboard gaskets. Cutting the dust cap off and shimming is up to you. Depends on your mechanical feel and abilities, and experience. I don't do this cause I like to keep the original dustcaps if possible, and have been successful so far. I use the slower drying white glue provided in the kits, and work the cone up and down to set the foam and check for any VC rub.

:lurk: I have 4 of them and am in the process of refurbing now. I got a refoam kit off of Eprey and it worked rather well. I may try the fix for the Mid range domes or get a tech at work to give me a steady hand. Good luck. These are awsome sounding speakers when they work. I had bought my first set of them in 1978 brand new and still have those. :music:

Welcome to AK, Quantum 3! Like Kencat said, great name and I suspect from your post that you'll enjoy this place.

The mismatched midrange domes is most likely due to the other having broken its tinsel leads (the wires going into the dome you noticed) before the foams went. This is a very common issue and used to be considered an impossible fix. Good replacement domes do show up on eBay quite regularly, but that's only an option if you like to spend money. I've seen a pair sell for $270+ and the occasional single go for a mere $45. The price is highly variable, but I'd go the DIY route myself. A while back, I typed up a post on how I repaired the three midrange domes on my Quantum 2s with broken tinsels. You can read it here (http://audiokarma.org/forums/showpost.php?p=407666&postcount=13) and if you've specific questions, then feel free to ask. AK member Rstsgs has also accomplished the feat, so while many have said it's impossible, it is very possible.

For the Watkins woofer foam, follow the other's suggestions and you'll be fine. If you're particularly worried about doing it yourself, though, you can have the original designer do it for you --Watkins Stereo (http://www.watkinsstereo.com/pages/1/index.htm).

There are other issues aside from the above to watch for. The EMIT tweeters are very prone to blowing from a too low of power amp clipping. (The Watkins woofer is extremely power hungry on these, so figure a good 200 watts per channel to be safe.) You'll want to use a multi meter to measure the resistance across the terminals on these tweeters to be sure they aren't open (infinite resistance). The other is that the adjustment pots on the back are very prone to corrosion, so those will need to be disassembled and cleaned up as per these instructions (http://audiokarma.org/forums/showpost.php?p=545795&postcount=4).

Please, keep up us informed as to your progress getting these going again.
- JP

Hi everyone,

Wow, thanks for all the great advice! I have posted some pics (link below) of the Quantum 3s that I found in the street yesterday. I am now curious if I own the right power to use these speakers once I get them back up and running?

In a nutshell, it's an Adcom GFA-545 100w amp and GTP-500 (tuner/pre-amp) which I bought ages ago with my Klipsch KG4s. I also have an older Sansui Z3000 too, but doubt that is up to the job, so to speak...

Link to the Quantum pics (http://home.comcast.net/~bh80231/)

I just took a look at your pictures and that replacement midrange dome has caught my curiosity. It doesn't look like one of those that is occasionally recommended as a possible replacement. Also, the screw pattern indicates to me that the magnet may be smaller than on the original Infinity. Any chance you can remove it and take some pictures of the back? If you find any numbers on or near the magnet, then someone might be able to identify who made it.

As to the power issue and what I said earlier, the Watkins woofer is very power hungry and offers up low impedances down low. The larger iterations are known as amp killers, however, your smaller Q3s force the system resonance much higher than the driver resonance (18 Hz). That means that with the sacrifice of bass extension, quantity, and quality you should be able to avoid the worst of it. Wrt your amp, if your room isn't particularly large and you don't have the tendency to crank the volume high (~90+db) and you don't listen to music with a lot of deep bass musical content (Massive Attack, Telarc CDs, etc), then you may be satisfied with the result. I ran my Quantum 2s for a while with a Pioneer SX-838 (~40 wpc) with fair success, though bass heavy passages did strain the unit forcing the protection circuit to engage on rare occasion.

- JP

Quantum 3,

I've measured the cone dia to be 9"at the break away to the flat
mounting flange. So the foam ID needs to be maximum 9" . The roll ID
is about 9-3/8" to 9-7/16. The foams I used had 1/4" inside flange so ID to the roll was 9-1/2", and the overall ID was 9".

You'll want new cardboard gaskets. Cutting the dust cap off and shimming is up to you. Depends on your mechanical feel and abilities, and experience. I don't do this cause I like to keep the original dustcaps if possible, and have been successful so far. I use the slower drying white glue provided in the kits, and work the cone up and down to set the foam and check for any VC rub.

Ken,

Thanks so much (sorry for the delay in reply, was out of town)!
May I impose a bit more and ask if this kit would be a good choice, or if you would suggest another source?

12" standard flat woofer repair kit (http://www.wooferrepair.com/12kit.html)

This would appear to me to be a fit.

Thank you again, I can't wait to get these going!

-bill

I just took a look at your pictures and that replacement midrange dome has caught my curiosity. It doesn't look like one of those that is occasionally recommended as a possible replacement. Also, the screw pattern indicates to me that the magnet may be smaller than on the original Infinity. Any chance you can remove it and take some pictures of the back? If you find any numbers on or near the magnet, then someone might be able to identify who made it.

As to the power issue and what I said earlier, the Watkins woofer is very power hungry and offers up low impedances down low. The larger iterations are known as amp killers, however, your smaller Q3s force the system resonance much higher than the driver resonance (18 Hz). That means that with the sacrifice of bass extension, quantity, and quality you should be able to avoid the worst of it. Wrt your amp, if your room isn't particularly large and you don't have the tendency to crank the volume high (~90+db) and you don't listen to music with a lot of deep bass musical content (Massive Attack, Telarc CDs, etc), then you may be satisfied with the result. I ran my Quantum 2s for a while with a Pioneer SX-838 (~40 wpc) with fair success, though bass heavy passages did strain the unit forcing the protection circuit to engage on rare occasion.

- JP
Hi JP,

Thanks for the help! I removed the foreign mid, and it appears to be an Audax HD13D37 if my googling skills are worth a darn. The lone sticker on the back reads:
HD13D37
8*
120673S
30003

Again, thanks all for the guidance, hints, advice, etc...

Best regards,
-bill

I have 2 sets of Quantum 3s.Finest speaker I have ever heard.The more wattage you throw at them the better they sound.I drive mine with a pair of Bryston mono blocks 500 watts ea into 8 ohms.i have had success with repairing the mids.Sometimes it does not look pretty but they work great afterwards.Do you have the grills also?Get them going and definetly get a stout amp .Imho 150-200 watts per channel is the minimum if you do not listen very loud.250 watts + per channel and they come alive. Just plain excellent speakers and a great find for you.

I suppose it really depends upon one's definition of low-level to moderate listening levels. When I say this, I'm thinking of average SPLs measured in the upper 70s to a max peak of ~86dB. For this, 40 watts was more than enough except for bass heavy music/movies and I was even able to use a Sonic Impact T-amp -- a 5-7wpc wonder -- at tolerable levels. If the amp is a good one, and Adcoms are good amps (not Brystons, but still good) that meet or exceed their specs, then it will work great in a smaller room (under 16'x15') at low to moderate listening levels (<86dB).

That said, with vintage Infinities, more power is always a great idea, so long as its good, solid power and not cheap watts (amps that claim high wattage but have no current).

Oh, rstsgsas, Quantum 3 stated in his first post that these did not have the grills. Is there any chance you could possibly snag some measurements of your grills and post them so he can possibly copy them for his pair?

- JP

Edit: Oh, and that Audax is supposed to be a decent driver for what it is ($10 used market price), but I doubt it's near the quality of the original Infinity domes.

Ken,

Thanks so much (sorry for the delay in reply, was out of town)!
May I impose a bit more and ask if this kit would be a good choice, or if you would suggest another source?

12" standard flat woofer repair kit (http://www.wooferrepair.com/12kit.html)

This would appear to me to be a fit.

Thank you again, I can't wait to get these going!

-bill

Bill,

This one looks perfect. KIT# 12F9.5. pretty much the same dims as mine.

Can you get some cardboard gaskets? I had to trim the ones I got to make them fit to the foam, but it still looks nicer than without them.

Dust cap would be the 4.5" one.

Have fun :thmbsp:

16 x 30 1/2 inches with a crossbar 12.5 in up from the bottom.Just a fram and the crossbars.They are attached on standouts 1.5 inches from front of speaker.

A friend of mine has some Quantum Jr. that had fried mid domes. I was able to repair them through products from this place:

http://www.simplyspeakers.com/

Thanks all! The woofers are repaired! I got a set of original badges for my to-be-built- grills, but the midrange dome tinsel problem persists (it is more missing than broken).

I hesitate to repair it since I have only one; the other is the Audax replacement speaker. I think I would be ahead to have a matched set of something?

The folks at Simplyspeakers.com said Audax was one of the OEMs for the original?

Does anyone have advice or suggestions on a good readily-available replacement pair of 1.5" dome midranges?

I'm itching to hear these speakers!

\bh

Hmmm,

That is probably a tough question. We'll have to keep this thread alive with idle chit-chat so someone sees it that may have some answers. (my contribution here :D )

Are you following ebay daily to see if any originals show up?

There's been quite a few pairs of the original midrange domes passing through eBay as of late. No fewer than three pairs of QLS-1s have been parted out as of late (including a set within driving distance of my home!!) for the sake of greed on the 'Bay. That's a lot of drivers and most have yet to sell. Have a little patience in you should be able to snag a pair within the month and likely within a week or two.

- JP

Hey, thanks guys. Yes, I have a search built on ebay to try and locate an original, such as the guy who parted out the QLS-1 pair a few weeks ago. I missed those auctions. I'll keep looking, that's supposed to be half the fun, right?

\bh

Yes, these are fantastic sounding speakers!! I have a pair of Quantum 2's and 3's. The Watkins woofers rival the performance of any 12" woofers I have ever heard. Most modern 12" or 15" "subwoofers" don't equal their extension into the 20 HZ range.

The EMIT tweeters and midrange domes, also are hard to beat for startingly real sound reproduction. Wait 'til you hear the wide dispersion of the highs with these speakers. I don't know why dispersion is are so good--coming from a flat panel tweeter.

Watch ebay for correct midrange domes. The later Infinity domes (from Kappa series) can be had for a reasonable amount, but originals would be nice. Exact replacements for the square-framed originals are more expensive, but sound great. The cause of failure is usually not from use, but from someone trying to dust off the dome or kids probing where they shouldn't be.

If there is any of the original wire showing on the moveable part (on the dome), tack soldering a piece of #32 or similar solid copper wire is not difficult. The stationary end can be glued to the black plastic and soldered onto the stranded lead to be used for connection. Even if you have only one original, it would be wise to do this as you may want it for a spare.

I got a set of original badges for my to-be-built- grills,


Hi Q3

Do you have a source for badges? Or did you snag a pair off the bay?

I'm in need myself for a rebuilt project.

I don't have a source per se', but scored a pair on ebay for $10. I'm looking at another batch of infinity stuff tonight that has some badges in it, I'll see what they are and let you know (since those are not why I am looking at the hodge-podge of parts)...

\bh

Thanks all! The woofers are repaired! \bh

Bill, how did the refoam go? Did you shim the VC or ???? Would be neat to hear how you did it and whether you thought they were easy to do etc.

I got a set of original badges for my to-be-built- grills, but the midrange dome tinsel problem persists (it is more missing than broken).

I hesitate to repair it since I have only one; the other is the Audax replacement speaker. I think I would be ahead to have a matched set of something?

The folks at Simplyspeakers.com said Audax was one of the OEMs for the original?

Does anyone have advice or suggestions on a good readily-available replacement pair of 1.5" dome midranges?\bh

Definitely the ultimate would be to have a set of the originals. Have you been keeping an eye on the auction site(s) and even here on AK? (nevermind, looking at your later posts...you are watching for sure....any luck though?)

I saw somewhere where it was said that the dome mids were Peerless :dunno: A very similar dome can be seen on some of the older ADS speakers.

I'm itching to hear these speakers!

\bh

While you are looking for the originals, getting an interim pair would be cool to get the speakers up and running. You'll want to make sure you are matching the impedance of the original mids. I haven't had any of mine out of the cab to measure DCR individually, but the two of them together measure about 4 Ohms, so if they are in parallel each could be 8 Ohm. I'ld wait for a positive reponse on this though before buying. You could test the replacement one you have to see what it measures, but whether that is per original could be suspect as well.

Bill, you may be the leader on this replacement project. I'm sure as time takes it's toll on the tinsel leads of these old Quantum speakers, others will be looking for a sonically equivalent dome replacement as well. Keep us all posted on your progress/experimentation.

Hi Ken,

The re-foam went pretty good, messy and it drying time was slower than I figured, but all in all I think it is a success. I did shim the vc per the instructions and DVD they sent. It seemed like a logical thing to do, and was really easy.

I've been watching the ebay auctions, missing out so far... a few more up there now, so I am hopeful! I did find out I can buy them new for $135 each! But I'm hoping for a more modest purchase price. We'll see...

Thanks for the interest, advice, and encouragement! I'll keep updating as progress occurs!

Best,

\bh

Hi Ken,

I did find out I can buy them new for $135 each! But I'm hoping for a more modest purchase price. We'll see...


\bh

What,what pardon? You can buy the mids new? Exact same PN ?

How? Where? I know 135$ is very steep but....these are a very delicate driver. I would probably have trouble dropping that kind of change right now too, but given the circumstances it might be worth it. Also, the info might help another reader who has the money to burn. On the plus side, it may help save a Quantum from the Partingout disease.

Yep... from Harman directly. This is sort of my litmus test for price I'll pay on auction; knowing that for about $300 I can get a NOS pair of midrange domes and get these beasts running.

That being said, a perfectly functional pair (of Quantum 3s with all speakers working that is - but needing refoam on the woofers) sold last night on ebay for $250!

So, I hesitate, not really knowing the value of my curbside find should I ever want out of them, so to speak... right now I only have about $40 in them (badges and re-foam kit), and expect I'll pay at least another $150 for mids if I am lucky, more like $300 (with shipping) if not so lucky and buy the NOS from Harman, and still want to build some grills.

I just don't want to end up being upsidedown on them, if you catch my meaning... but if they sound as good as I hope, it's an investment in keepers, and a moot point!

\bh

email from Harman:

Hello,

Thank you for your inquiry about the availability of one of our parts.
The part is available:
The part is called: Mid Range
The Part # is: 902-0206
The price is $131.64 each, plus shipping and handling.
Please add tax if you live in New York, California, Florida, Arizona, New Jersey or North Carolina.

but if they sound as good as I hope, it's an investment in keepers, and a moot point!

\bh



Very,very well put. I like that.

Hi Q3,
Could I have your contact for the mid speakers from H K if you don't mind? I have 4 Q3's and 2 Q5's, 4 of the mids are bad and am slowly replacing/fixing them. These speakers really sound great when they are working fully. :thmbsp: I bought my first pair in 1978 and still have them. :yes:
Are these actually new replacements? same speakers?

John

I have located one replacement midrange dome, it is installed and sounds awesome! Now I really notice how bad the non-original midrange sounds by comparison! So, I'm thinking of trying the microscopic tinsel repair on the other, but mine is broken almost flush at the dust cover... There is nothing visible to tack to. I guess I can try and hope the flux/silver seeps in and make contact?

Another question though, could I not remove the dust cap and replace both tinsel leads and install a new cap? Or are the caps rare too? Seems I could prime the two leads on that end, reinstall the cap, then fix the leads into the channel? Is my logic flawed?

Last, is there a reason this tinsel must be used, rather than a more sturdy stock or gauge of wire? I am guessing the answer will be yes, but not sure why?

Thanks folks!

\bh



Welcome to AK, Quantum 3! Like Kencat said, great name and I suspect from your post that you'll enjoy this place.

The mismatched midrange domes is most likely due to the other having broken its tinsel leads (the wires going into the dome you noticed) before the foams went. This is a very common issue and used to be considered an impossible fix. Good replacement domes do show up on eBay quite regularly, but that's only an option if you like to spend money. I've seen a pair sell for $270+ and the occasional single go for a mere $45. The price is highly variable, but I'd go the DIY route myself. A while back, I typed up a post on how I repaired the three midrange domes on my Quantum 2s with broken tinsels. You can read it here (http://audiokarma.org/forums/showpost.php?p=407666&postcount=13) and if you've specific questions, then feel free to ask. AK member Rstsgs has also accomplished the feat, so while many have said it's impossible, it is very possible.

For the Watkins woofer foam, follow the other's suggestions and you'll be fine. If you're particularly worried about doing it yourself, though, you can have the original designer do it for you --Watkins Stereo (http://www.watkinsstereo.com/pages/1/index.htm).

There are other issues aside from the above to watch for. The EMIT tweeters are very prone to blowing from a too low of power amp clipping. (The Watkins woofer is extremely power hungry on these, so figure a good 200 watts per channel to be safe.) You'll want to use a multi meter to measure the resistance across the terminals on these tweeters to be sure they aren't open (infinite resistance). The other is that the adjustment pots on the back are very prone to corrosion, so those will need to be disassembled and cleaned up as per these instructions (http://audiokarma.org/forums/showpost.php?p=545795&postcount=4).

Please, keep up us informed as to your progress getting these going again.
- JP

So, I'm thinking of trying the microscopic tinsel repair on the other, but mine is broken almost flush at the dust cover... There is nothing visible to tack to. I guess I can try and hope the flux/silver seeps in and make contact?
Unfortunately, that’s not possible. You must have a goodly sliver of exposed wire to solder to and do so very carefully and quickly without overheating the tinsel and its coating. For, if you hope to let the solder flow or are too slow, that blasted orange-brown resin melts just enough to cover the wire over again and prevent it from sticking. Yes, it can be very frustrating. However, I’ve developed a new trick that’s just a hair easier when dealing with tinsels broken off right at the dome that I’ll discuss below.

Another question though, could I not remove the dust cap and replace both tinsel leads and install a new cap? Or are the caps rare too?
No to the first and yes to the second. The dome of the midrange is not a dustcap, but the whole of the driver. What you speak of is the dome driver equivalent of a reconing. You see, this dome is shaped fabric of which the surround is a continuation of the same material. The edges are then glued to the face plate with a flat metal ‘washer’ glued over that edge to provide greater hold and a firm surface to butt against the magnet. At the fold that visually divides the two is glued the aluminum former about which the magnet wire (standard very fine gauge copper with an enamel coating) is wound. To attempt to remove the dome would mean the removal of the voice coil of which a replacement would need to be an exact match. Thus, to do as you suggest would need a special kit that a professional might utilize for such a replacement. The kits are not available for these drivers, as I learned when I walked the same path early on in my quest to find a means to repair these drivers with the broken tinsels.

Seems I could prime the two leads on that end, reinstall the cap, then fix the leads into the channel? Is my logic flawed?
Not at all, I did a variant to repair one completely missing tinsel on one of the midrange domes in my Dahlquist DQ-10s that was successful (no audible difference betwixt the original and repaired drivers). Just a few minutes ago, I accomplished the same feat with two missing tinsels on the shot midrange dome that came with my new Quantum 2 cabinet during my mirror-imaging project to test the validity of the process on this driver so I could tell you if it would work or not. It wasn’t wholly selfless, a few days back a visiting friend walked into one of my Quantum 2s breaking anew the tinsel on one of my repaired domes. Amazingly, it wasn’t the patched section, but the original intact tinsel section that broke. Anyways, I needed to repair one to get these back up to par and your post just gave me the excuse.

Last, is there a reason this tinsel must be used, rather than a more sturdy stock or gauge of wire? I am guessing the answer will be yes, but not sure why?
Answer will be yes? Well, only sorta. It would seem that the tinsels encased in their heavy adamantine coating of that infamous orange-brown resin would add mass and stiffness to the compliance of the dome. I suspect this much the case, but in preliminary listening, I haven’t heard a different between the originals and my repairs. Power handling is likely lower with a repaired driver, though. I’m currently looking for some replacement substance to coat my new tinsels with to simulate the originals more accurately. When I find something, I’ll let you know.

As to how to do the tinsel replacement, not repair, much of the story is the same as my other post on patching these drivers. However, in many ways tinsel replacement is easier, which is good considering its necessity when the tinsel is broken right at the dome.

The tools you’ll need are as follows: a low wattage iron with a fine point tip – I use a cheap 15 watt Radio Shack special with the fine point that I’ve filed to be finer and cut a small groove in like a fountain pen to hold a solder drop where
I want it, a good pair of sharp, fine dikes/side cutters/ or whatever you call them, a pair of locking hemostats (sometimes called clamps or roach clips if you’re a child of the ‘60s/’70s), a magnifier lamp on a swing arm (its hard to make do with just a regular swing arm lamp and uncorrected vision as I do), and a sharp knife with a good handle and a short blade – keep a decent whetstone on hand as its easier if you keep sharpening the tip as it dulls in use during the repair. For materials, I use regular magnet wire that’s ~36 gauge I believe, 240 grit sandpaper to sand the enamel off the ends of the wire before soldering, solder tip cleaner (just makes it easier to keep the solder drop on the tip where you need it), flux and silver solder.

For preparation of the driver for repair, remove the four screws holding the face plate to the magnet and gently pull the dome straight out to keep from buggering the voice coil. Leave the foam plug in the hole in the center of the magnet and put the whole thing in a new sandwich bag and seal to keep from accidentally getting filings into the VC gap. Put the screws and washers someplace where you won’t lose them and watch out for the silver washers, they’ll want to stay in place at first, but may fall out during repairs and roll off the face of the Earth. Fortunately, the VC on these midranges are shorter than the plastic ring on the back of the face plate that helps align the magnet during assembly (I think). So, if you’ll bed the connection tabs back, you can set the whole front plate right on your workbench without messing up the VC (big, big pita with the Dahlquist driver for though similar, the VC was longer requiring me to tape a roll of masking tape onto the back to hold it up off the surface and relatively secure – you’ll need something like this for when you work on the back, though).

Now that you have the face plate with the dome before you, swing your lamp down for good light, sharpen your knife, and dig in. The channel where the wire leads from where it’s soldered to the connector tabs (the round depression on the front) is square bottomed and should have the resin dug out of for future replacement by something. Typically, the tinsel wire is wedged into one of these corners and just for the heck of it I like to remove it with all the rest of the old resin (mostly hard and will come up in shavings, but in the round depression is typically a little rubbery for some reason). Be careful to pull the knife tip out from the dome rather than push lest you slip and slice the dome in half. Where the channel ends, the resin is typically piled up a little bit to support where the tinsel goes out into free air to meet the dome. You can use the side cutters to cut this down relatively flat to easier tackle with the knife. Sharpen the tip as needed, for it dulls quickly (at least with my cheap Swiss Army knife, but not as fast as the scalpel dulled that I used initially) and sharper makes it easier.

When done, get the knife tip back ¼” as sharp as you can. Pick up the top plate and place your finger tip inside the dome supporting the fabric where the tinsel enters – try not to press too hard lest you deform the VC nearby or break it’s lead underneath. Very carefully bring the blade tip up along the fabric and pry/cut the resin off while approaching from several angles. This isn’t difficult or time consuming, but you do want a steady hand lest you slide the dome (fairly resilient and the resin will go before the fabric, but just in case …). I’ve considered using some solvent to make better work of this, but nothing seems to work. I’ve found that tetrahydrofuran (read the warnings and be careful) softens it up enough to be scraped away easily, unlike all the other solvents I’ve tried, but not to the degree to allow dabbing removal with a cotton swab. When that’s all cleaned up, take a sewing needle or a pin and prick a small hole in the dome near where the old tinsel entered. The needle is easier as you can roll it in your finger tips to drill a hole through the coating that stiffens the fabric without risking deforming the dome by pushing too hard.

Now, turn the front plate over and figure some way to secure it so that while pressing down or rough handling the dome you won’t smash it in too badly or break the other tinsel. For simplicity’s sake, I electrical taped a roll of masking tape around the dome to provide a firm surface while protecting the rest. Now, on the inside of the dome, you’ll see the tinsel wire glued to the fabric with more of that resin in a little loop before it heads up to the VC wires and joins up with them. Here you’ll prepare a little section of the loop for soldering using the process mentioned in the “Quantum 5 midrange help” thread I linked to earlier. Tin the bare metal and be sure to scrape away enough of the resin that it won’t flow over the tinned spot preventing soldering, but not so much that the wire comes free – it’ll break far, far too easily that way.

Take a ~6” length of magnet wire, long enough you have plenty to compensate for any mistakes, but not so long as to get tangled on everything. Take a little square of your sandpaper, fold it in half, and sand the enamel off 1/16” of the end by pinching the paper over it and pulling off the end, repeat. Add a hair of rosin to the bare copper here and tin it. When ready, take one of the ends and feed it through the needle/pin hole so that the tinned end remains inside the dome. Bend it just slightly so that the end will lay flat against the tinned portion of the dome VC. Use the linked to trick to wave a droplet of solder over the two to solder them wires together without melting the resin and forcing the need to scrape clean the tinned area. If need be, use the hemostats here to hold the wire in place, but do not lock them! If you do, it’s likely you’ll tear the connection apart or break the VC wire while trying to carefully unlock them (sliding teeth catch). Measure from the outside end of your replacement tinsel wire the resistance of the VC to the other tinsel’s connection tab. Make sure you’re measuring around 8 ohms so that you know your solder connection has good continuity and isn’t just pretending to be soldered while trapped in melted resin.

Before moving anything, very carefully apply something over the solder joint and the wire inside the dome so that it’s secured firmly to the fabric. Elsewise the loose wire could very well break when first playing music through your repaired dome or at the very least you’ll hear unpleasant rattling as the wire strikes the inside of the dome. The goop I’ve found to work fairly well is that little vial of clear liquid vinyl that comes with vinyl patch kits (for air mattresses and the like), it’s gooey enough to hold the wire well, but soft enough to flex with the dome. Be sparing, a little goes a long ways, but too much might add too much mass to the dome (you do have a little play room as the new tinsels are less massy than the old).

When the glue is set, flip the face plate back over and remove the tape roll or whatever else you used. Now, arc the magnet wire where it comes out of the dome into a similar shape and size as the original tinsel, lay the rest into the trough out to the solder tab spot to figure length and cut off the excess. Take your hemostats, lock them onto the wire to firmly secure it (to prevent stressing the solder connection inside the dome), and sand ~1/4” of the end of the wire free of enamel. Take your soldering iron and while holding the wire end down into that circular depression where I earlier mentioned the tinsel is secured to the connection tabs and solder it into place. Carefully lay the tinsel into the trough and figure out some way to secure it to prevent rattling. If you can find similar resin, great, pour that in there and coat the rest of the magnet wire to match the original. If not, take a short piece of electrical tape, fold it and press it into the channel securely over the wire using a flat bladed screwdriver of the back of you knife blade.

Carefully place the front plate over the magnet so that the VC goes into the magnet gap without and lateral torsion or scraping while eye-balling the screw holes so that they’re aligned with those in the front plate. When in place, loosely replace the screws and gently press with fingers on the surround roll of the dome nearest where the VC former is glued, press just a little bit in (<1/4”) and listen/feel for rub (slight hashing sound). If everything seems to be alright with no rub and the dome moves freely, tighten the screws, and recheck for rub.

Take your multimeter and in the resistance setting scrape the leads across the connection tabs. If the repairs worked, the driver will make a crackling sound. If it does, reinstall it while observing that the positive side of the driver marked by the orange dot is reconnected to the positive lead that was formerly removed from it, and enjoy the music.

If you have any further questions about the process, just ask. The whole process should take under 1.5 hours to 2 and only about an hour after you’ve had a little practice.

I wonder if I set a record for the most number of mentions of the word “tinsel” in one post? :scratch2:


Good luck,
- JP

JP,

Wow! What a document! That's a keeper for sure! I'll take a shot at it! I wish you lived in Denver and liked beer, I'd try bribery! ;)

\bh

Good luck, quantum 3. I hope you're successful in your repairs or at least that they'll hold until you can find an intact mid for a reasonable price.

Anyways, I was able to borrow a friend's digital camera for a little bit this weekend and snapped a couple of quick pics of the repaired drivers installed in their Quantum 2. Maybe the visual reference will be a little helpful?

Dual Tinsel Replacement:
http://audiokarma.org/forums/attachment.php?attachmentid=16828&stc=1

Eventually I hope to find the appropriate resin to coat this tinsel and fill the groove as was the case with the originals. Suggestions?

Single Tinsel Patch:
http://i30.photobucket.com/albums/c301/jpvanson/Infinity%20Quantum%202/MidRep2.jpg
Top tinsel is repaired via the old means -- ie, soldered to the tinsel stubs rather than a total replacement using 3 Sound King wire strands vs. magnet wire.

- JP

JP
Great pictures, I think replacing the entire lead looks much cleaner. Just counted the number of domes that I need to repair. Looks like 11 total and the last one is questionable. Except for the wire, I have most of the materials needed to tackle the job. I will probably try to do 2 or 3 per week depending on how long it takes. Haven’t a chance to check the emits. Crossing my fingers that they are in good shape. Also took a quick peek at partsexpress and madissound and it looks like it might be hard to find some of the big electrolytics. I think some place like Mouser or Digikey will also have parts such as those.

Eleven domes? That leaves just one. What happened to these? I thought the seller, Bob, said that they were fully functional. You have a lot of work ahead of you on those, but by the third you should be able to fix a lead in under 20-30 mins and may get faster towards the end. It would take a lot of waiting and a lot of money to find intact originals on eBay, so it's worth the effort.

If the Mylar on the EMITs is not shredded (easily visible through the front of the tweeters), then you should be alright with those as the remaining possible damage is largely repairable. You can find links to posts on how to repair the three main problems with EMITs here (http://audiokarma.org/forums/showpost.php?p=642942&postcount=9).

The midbass driver that you've mentioned being bad should be easy to replace as it was used in many different speakers: the most notable being the Infinity Quantum series, of course, and the Dahlquist DQ-10. If you're impatient, Regnar (http://www.regnar.com/) repairs that driver, but at significant cost.

As to the large electrolytics, yes, you won't find caps of those values at those speaker builder suppliers. However, they are just generic electrolytics that need only be replaced with those of like value. Of course, you could also pick up a batch of smaller value caps and stack them to reach the needed value with no drawbacks. I have three Quantum 2 cabinets with crossovers, the earliest has a stack of the Callins non-polarized computer grade electrolytics, the second just one serial number off has a couple of large caps with smaller bypass caps to fill in the last of the value, and the third much later cab has single large caps of the appropriate value. So, however you can reach the capacitance, so long as the voltage rating is the same or higher, will work for the Watkins.

Good luck on your repairs. Any chance of photos showing your progress?

- JP

JP

The emits look good from the front so I think they might be ok. And yes, we have a nice Digital Cam that I can take some photos with. I will post a few once I have a few of the mids repaired. Oh as for repairing the Mid bass, it is not the original driver so I must locate a pair of those. If you run across any let me know. I will take a photo of the of the cabinets with the grills in place and post it later tonight.

I look forward to seeing the pictures. At the very least they would allow me to enjoy a pair of QLS-1s by proxy. :thmbsp:

Oh as for repairing the Mid bass, it is not the original driver so I must locate a pair of those. If you run across any let me know.
Sure thing. There's a pair that look to be in great shape here (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=9732665852). As I have both a pair of Quantum 2s and Dahlquist DQ-10s, I've been able to compare the drivers directly and they are the same. All the numbers except for the manufacture date match up.

- JP

Sorry, have the pic but can't figure out how to insert it.

Sorry, have the pic but can't figure out how to insert it.


Check this out. A JP tutorial. Excellent.

http://audiokarma.org/forums/showthread.php?t=43025