4x woofers - need advice on repairing cone AND surround

[Kip]

Hi, I am restoring¹ a pair of 4x's and was hoping for some advice.  One woofer cone has a radial tear near it's outer edge that actually continues right into the surround material for about 1/4". The cone-part of the tear is about 1-1/4" long.

In my research so far, I've found quite a bit of info about replacing woofer surrounds and entire cones, but not much about repairing tears in original cones.  So here are my questions

1. What are the recommended materials/methods for repairing tears in paper cones, if any?  I've found everything from using pieces of coffee filter paper and scrapbooking glue to using pieces of paper towel applied with ordinary Elmer's wood glue (really?).  Or perhaps there is no recommended approach because the choice of materials to use is not that critical (within reason)?
2. The woofer surrounds aren't like anything I've encountered before - they seem to be made of some sort of fabric that's been coated with a sticky rubber-like compound - they are a (dirty) yellow color and have a lot of minute debris stuck to them.  They also appear to have uneven wrinkles in them at different spots around the cone.  Are these original?  Should I not touch them?  There is no noticeable voice coil rubbing and this woofer sounds fine except for occasionally fuzz being produced by the tear.
3. Is it reasonable to try to fix this tear at all, given that it spans the paper cone and the surround material?

Sorry for initially having no pictures...I can upload later if that would help.

 

Thanks very much,

-Kip

 

¹ And enjoying the heck out of doing so.

[dxho]

I don't see much of a down side to repair. It's pretty easy to pick up a
used one if it doesn't work.

Yeah, coffee filter material is usable for the cone. Pick your favorite glue;
it doesn't seem to be critical.

I think I'd start with a little of the same glue on the surround. Yes, they are
original. There's a simple test to see if they need more sealer, but the cone/s
need to be whole.

[owlsplace]

4 hours ago, Kip said:

What are the recommended materials/methods for repairing tears in paper cone

Welcome, Kip,

I've used cigarette rolling paper and watered-down Aleene's for cone patching on the early CTS AR-4 cones and I am sure mine was a lot worse than yours.

Would have to see the surrounds to comment on that. The cloth was not serviceable on the one I did and was replaced with foam. PVA based glues are not a good choice for cloth surrounds in general.

Roger

[ra.ra]

Your woofers as described do sound original, but uploading a pic or two will confirm all of this, and the pics will also show us the extent of your particular concern. Yellow (rather than black) cloth surrounds are slightly unusual with 4x's, and this suggests to me that you might have a pair which employed the earlier AR-4 woofer with the non-circular basket frame. The only comment you make thusfar which concerns me is the remark about the tear extending into the surround area.

I pretty much agree with dxho regarding advocating an attempt at repair, but with two caveats. Applying any type of glue on a cloth surround is most likely counterproductive with regard to maintaining flexibility, and the type of glue used for cone repair does matter. For cone repair, a simple water-based white hobby glue is very adequate, whereas a yellow wood glue or solvent-based adhesive will provide no additional benefit and may also be more difficult to apply. A splotch of coffee filter or good-quality paper towel is very effective - - what you want is a piece of lightweight paper with strong omni-directional fibers to span across and beyond the tear in the cone. Use the white glue full strength but thinly applied - - you do not want to add water which may have the unintended effect of warping the cone as it dries. Best applied from the backside if you can, in order to try to preserve the original appearance of the woofer cone as much as possible.

In the pic attached, you see an AR-4 woofer with an unfortunate small tear in the cloth surround, which has since been very satisfactorily repaired after a thin smear of silicon sealant on the underside to mend the fabric. This successful tip was originated via the generous courtesy of RoyC.

[JKent]

Welcome Kip!

ra.ra's advice is spot on. The paper part (cone) can be patched. Coffee filter material is good. I have used the strong thin paper used for cleaning glasses or camera lenses. As he said, you want strong omni-directional fibers.

Aleene's Tacky Glue is favored by many for speaker repairs but you could also use plain old Elmer's Glue. If you have a scrapbooker in the family or a crafter who uses Modge Podge those glues will work too.

The tear in the cloth surround is unfortunate. RoyC is an expert at speaker repair and if he says to put a thin smear of silicone sealant on the back you can take that to the bank. But keep the smear small--don't be tempted to "seal" the whole surround with silicone--it will ruin the sound.

As dxho wrote, you can always get a replacement used on ebay. Another option, if you don't want to DIY, would be to send the woofer to Bill LeGall at Millersound.

Let us know how you make out.

-Kent

[Kip]

Wow, thanks for all the quick responses!  My wife is heavy into scrapbooking - I'll see if I can scrounge some glue from her.

As to the torn surround...I am wondering:  Has anyone ever tried thinning down any sort of rubber-like cement for something like this?   I have a can of "plasti-dip", which is a thick rubber-like liquid that you dip your tool handles into (e.g. pliers) and cures to a rubber cushion (well, it's not really rubber, but somewhere between rubber and plastic).  I was thinking if that could be thinned down with an appropriate solvent so that it was brush-able...then paint a few layers over the crack (both sides).  Or even rubber cement.

Apologies for not posting pictures...I will do so asap.

Thank you everyone!

[stupidhead]

Hi Kip and welcome.

The above cloth surround fix explained by ra.ra indicates silicone, not rubber cement. My suspicion is that silicone will remain more flexible than a cement of any kind would, and you will quickly come to understand, as Kent indicated, if this is Roy's approach it is the proper approach. Also on the cone fix use the smallest "patch" possible, and the least amount of glue that achieves the desired adhesion. I have used the coffee filter material with success, but the idea of the eyeglass fabric is interesting and may lead to less mass. You basically don't want to alter the mass of the cone any more than necessary. Conceptually this applies to the surround fix as well.

Your description of the surrounds does certainly sound like the cloth surround woofer in this model, and don't be concerned with the wrinkles. When it is making a full excursion you will see no wrinkles.

Geoff

pics will be helpful in determining what approach is best

[Kip]

dTear, front view (secondary tear running towards my finger not through cone

Full front view of wooferTear as seen from bottom through frameNumbering on back of magnet

[ra.ra]

Hey Kip, just a few thoughts here. That "plasti-dip" stuff is a nice product, but as you've already stated, it is meant for developing a bit of an improved cushioned and tactile grip on the otherwise slippery handles of hand tools. It works well for that purpose, but eventually it hardens, and it should never be employed for use in attempting to resuscitate cloth speaker surrounds. You'll kill the poor woofers with that stuff.

The 4x woofer employs a dustcap which allows air to pass through, so complete air-tightness is not quite as critical here as with other AR 'classic' models. Don't concern yourself with this issue for now - -  instead, focus on the structural repair of the cone and surround.

Final point - - mea culpa here - - no sooner had I stated that yellow cloth surrounds were "unusual" for 4x speakers when I remembered that in fact I owned a fine pair which disproved my own point.  Pic attached shows 4x's atop two pairs of 4's - - all three pair have the "yellow"cloth surrounds. Forgive me for experiencing an encroaching senior moment.     

[ra.ra]

Looks like you and I were posting at same time, but indeed your pics are most helpful. As suspected, you do have the earlier AR-4 woofer (non-circular basket frame), and this unique version of the 4x incorporates a rather untypical crossover - - you should find two capacitors and a "265" coil - see schematic attached. I have a very similar pair - - the stamps on my woofers are nearly identical, except instead of 526, mine are stamped 532, which suggests that mine were fabricated six weeks later than yours in calendar year 1965. I would suspect that your serial numbers are in the 36000 or 37000 range.

I am feeling optimistic about this repair, even if you do need to proceed cautiously. The two tears in your paper cone can be repaired with the advice already offered. The tear extending into the cloth surround does present a minor difficulty, but I do think it can be revived with a delicate finger swipe of silicon sealant - - maybe on the backside first, and then if necessary, also on the front. Use a light touch applying anything on the cloth surround.   

[Kip]

(Warning: somewhat lengthy, possibly boring nostalgia in this post [but I do think it's relevant])

Thanks for that schematic!

My own plot thickens, however.  I'm going to be guilty of pushing this thread slightly off-topic.  And if the rest of this post qualifies as TMI, my apologies!

When I first began looking at these speakers, my intent was to simply repair what damage they had.  Then I found this site and got it into my head to try to restore them to original condition (as best as I could).

However, after looking at the myriad of 4X photos here and on other sites, I realized that the tweeters in these boxes are not the originals.  In fact they are not even close.  I think these tweeters are called "inverted dome" types? (pictures included)  In an effort to try to determine exactly what they are, I searched on Google and found nothing even close (which surprised me a bit).  It then occurred to me to check the place where I (likely) obtained these speakers in the first place.

Please skip this next paragraph if you don't want to hear an old f*rt being nostalgic...

During my college years one of my multiple part-time jobs was working as a service technician at New England Music (now New England Hi Fi) in Maine.  Back in the 70's, that store was where almost everyone in the area went to buy high fidelity products.  We sold many brands: Harmon-Kardon, Sansui, Marantz, B&O, Pioneer, Yamaha, McIntosh, etc.  And Advent speakers.  A LOT of Advent speakers.  I can't tell you how many blown Advent tweeters we replaced during my stint there.  There were days during which we did nothing else - I still remember the queue of Advents along one wall, all waiting for new tweeters.  If I remember correctly, the typical case was a pair of Large Advents hooked up to an underpowered receiver, then a party where someone inevitably "cranked up the stereo", causing it to clip like crazy, and all the high-frequency energy generated by the clipping passing through the crossover and cooking the tweeters.  Given the sheer number of speakers we encountered in the service department with blown tweeters, woofers, etc., along with the fact that it was very common for a customer to upgrade instead of repair, we ended up with a veritable pile of used drivers of all types, and it was common for us to throw together combinations for use as bench speakers, etc.  I believe that's how I got these 4X's.

I guess that's enough nostalgia - back to my tweeters.  I went to NE HiFi's site and began reading their history which jarred my aged memory,¹ and I remembered that for a short while we sold Genesis speakers.  That company apparently experienced cash flow/debt problems and went bankrupt many years ago.  But one of the original employees has kept the line going (humanspeakers.com).  Perusing their site gallery I had a look at the vintage "6" model - and there were my tweeters!

Now I am torn (along with my woofer cone) between trying to find original (or close) tweeters for these 4X's or just running them with the Genesis tweeters.

Given the impressive expertise here, I thought I'd solicit opinions.  THANKS!

 

¹ The classic joke: They say your memory is the second thing to go...I don't remember what the first thing is.

[stupidhead]

a conundrum for sure. Can we verify both speakers have had the same modification?

I have no real knowledge of the Genesis driver you have but it is a safe bet it does not have the characteristics of the AR proper driver. The AR drivers do come up for sale occasionally, or possibly someone here has a set they would part with. If restoration is your goal then you have some hurtles for sure. The cutout that was made for the Genesis has certainly compromised the baffle and if you try to install OEM you would need to do some fancy woodworking to be able to properly mount (and seal) the OEMs.

Has the crossover been modified as well?

We all have speakers that we have gotten a vision of restoring and end up putting more into them than they are worth in the market place, but at the end of the day when you have poured your heart, soul, money and time into a set of these classics you now own their soul. (biggles reference) It also is very gratifying to achieve the end result. It's a funny "hobby".

If it were me the condition of the cabinets and finish variety would play a major role in if I were to proceed or just cut bait.

Thanx again for this post as it is a fabulous example of resurrecting a worthy classic and your enjoyable last post is anything but off topic!

[Kip]

Well, I'm happy at least one person didn't fall asleep reading my last reply.

Firstly, yes, both speakers have these Genesis tweeters in them.  And the crossover components appear to be unmodified (I'm assuming that the sealed block, which looks like it contains 4 cans, is the original...it has no markings on it whatsoever.  Also none of the solder joints look like they've been touched since manufacture.)

I think the tweeter openings were only modified enough to accommodate the square magnets on these Genesis tweeters.  So it may be wishful thinking but I think that enough of the original, round countersink surfaces remain such that I can probably go back to round-frame tweeters without any major woodworking.  The cabinets themselves IMO could be reasonably refinished (no major bashes anywhere).  One grill front is missing - the other looks pretty poor, so I'd probably do both.

I can't help but wonder if someone, years ago, decided that these 4X's sounded "better" with the Genesis tweeters, and that may be why they went through the bother of opening up the tweeter holes to accommodate them.  Or, it could have been a case of "... here's (an abandoned) pair of 4X's with blown tweeters...let's slap these Genesis tweeters in there to get working speakers...")  In either case they either didn't know enough or couldn't be bothered to consider any mods to the crossover circuit.  Interesting that according to the site I referenced earlier, the Genesis 6 speakers used the simplest crossover imaginable: a single cap in series with the tweeter (some added an inductor shunted across the tweeter).  Yet they supposedly were great-sounding speakers (NE Music would not have sold them otherwise - that's just the way the owner was.)

I'm not planning on trying to sell these after restoration, so as you say this will be for my own gratification.  My wife will tell you I'm a fix-a-holic¹.

Thank you for sharing your thoughts.  Cheers!

¹ Wanted to share this: I once saw a fellow wearing his company tee shirt with their motto: "We repair the stuff your husband fixes."

 

[ra.ra]

Hmmm ....... that tweeter complicates things a bit. Though I have never heard any Genesis speakers, I believe your tweeter is basically an updated version of the original EPI inverted dome, which I think is a really great tweeter. Normally, those tweeters are wired in series with a 10uf cap, whereas the AR-4x tweeter employs a 20uf cap. Your guess about the Genesis tweeter just might be accurate, and these tweeters generally have a brighter voice than the AR tweeter, but only you can determine how well it mates with the AR woofer. It is probably a very good tweeter, but I suspect it is not currently wired for optimal performance.    

I'd be curious to see inside your speaker(s) or at least to know if they look identical to this AR-4x crossover. The big gauze-wrapped wax block contains two unmarked caps (20uf tweet and 24uf woof), and the metal strap holding it down is actually part of the electrical circuit. 

BTW, I think you might be the first member to use footnotes in your posts! 

[owlsplace]

4 hours ago, Kip said:

Wanted to share this: I once saw a fellow wearing his company tee shirt with their motto: "We repair the stuff your husband fixes."

Ha, ha, ha, that's a good one. I'm assuming you don't have a big investment in these so whether you leave them modded or go for a full restore is a matter of personal taste. There seem to be plenty of modded 4x's out there and AR made over 400,000 of these if IIRC. However, the early CTS woofers versions are somewhat rare (serial numbers prior to about 38,000 I believe) and had the so-called Zobel crossover using a cap/resistor combo across the woofer terminals. They seem to go on the auction site for $300-400 in original condition as opposed to $150-250 for the run-of-the-mill which is something to keep in mind if you are thinking of selling these at a later date.

The paper cones on these CTS woofers are also extremely fragile as you can see the fracture next to the tear in your photo. The cloth surrounds are also known to become overly stiff on these.

I have a 4x that was modded with an Advent tweeter which sounds a lot brighter than the stock 4x tweeter. The later AR 2-ways are brighter sounding also I believe.  Depends on your personal taste -- perhaps the Genesis tweets will sound better than the stock tweets to you.

At this point I would say check the pots for corrosion and get a patch on the woofer not worrying too much about increasing the mass of the cone and get a patch on the fracture next to the tear as well. If you decide you don't like the sound you can hunt up a used pair of 4x tweeters later on. The wax caps will more than likely need replacing also.

Enjoy,

Roger

[stupidhead]

4 hours ago, Kip said:

 

I can't help but wonder if someone, years ago, decided that these 4X's sounded "better" with the Genesis tweeters, and that may be why they went through the bother of opening up the tweeter holes to accommodate them.  Or, it could have been a case of "... here's (an abandoned) pair of 4X's with blown tweeters...let's slap these Genesis tweeters in there to get working speakers..."

 

Another possibility I suppose is that the pots had corroded to the point of not working, an assumption was drawn that the tweeters were blown (circuit not complete with corroded pots) and down the rabbit hole they went!

Pics of your xover may reveal some clues.

Roger's outlined approach sounds like a good way to get to a baseline and then go (or not) from there!

[Kip]

Yes, the L-pads (if that's what they are) on these speakers are in very bad shape...I think signal gets to the tweeter in only one spot on the first speaker I've opened up.  Those are on my TODO list.

5 hours ago, ra.ra said:

I'd be curious to see inside your speaker(s) or at least to know if they look identical to this AR-4x crossover. The big gauze-wrapped wax block contains two unmarked caps (20uf tweet and 24uf woof), and the metal strap holding it down is actually part of the electrical circuit. 

Yes, my crossover section looks EXACTLY like this, right down to the number on the inductor. (OK, maybe it's not as clean-looking as the one in your picture.)  Re: last crossover diagram you posted (thanks again): hmm...that's not really an L-pad, is it?  More like a wirewound rheostat?

P.S. At the risk of trying to sound younger than I actually am: You guys all rock, BTW.

 

[ra.ra]

Yep, geezers rock! And do you have serial numbers on the rear paper labels?

[frankmarsi]

Yes, and in 1972 I'd blown out one 12inch woofer, 1 mid and 7 tweeters until I bought my Micro-Statics in'74 and nothing mattered anymore. The 3as were now happy, as was I.

By 1978 I blew another 12inch woofer, one mid and both of the tweeters that were already gone from way back in in 1974, but AR didn't notice that and replaced all that was necessary.

In 1989 I blew out another 16 LST tweeters and two 12 inch woofers and no mids. Why? Because old AR mids were better than another manufacturers.  

By 2012, I blew out another three 12inch woofers in the LSTs and nothing else. 

That's how life is with 40+ year old speakers.

 

 

 

[Kip]

Earbuds?

[frankmarsi]

Wow! How fast was that answer?

Shows ya!

That's what I'm talking about but, so what.

Even ancient AR speakers are subject to the new .................................

[owlsplace]

2 hours ago, Kip said:

 More like a wirewound rheostat?

More like a potentiometer ... but serial numbers would provide a clue as Robert mentioned.

Roger

[Kip]

Serial numbers from the rear labels are:  FX 31107 and FX 30440

[Kip]

2 hours ago, frankmarsi said:

Wow! How fast was that answer?

Shows ya!

That's what I'm talking about but, so what.

Even ancient AR speakers are subject to the new .................................

Um, not sure how to interpret this response, but I thought you were joking when you said you'd blown all those drivers, so I replied in kind.

If I've offended, I'm sorry.

[frankmarsi]

11 hours ago, Kip said:

Um, not sure how to interpret this response, but I thought you were joking when you said you'd blown all those drivers, so I replied in kind.

If I've offended, I'm sorry.

No offense of course, I was recounting my failed drivers.

But to your point, with the AR-4ax being plentiful as they were probably the most made besides the AR-2ax, I'd say buy a couple of used ones while you can.

I predict that in less than ten or so years, all of these used drivers will be extremely rare.