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ra.ra

Smaller Advent woofer

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ra.ra    0

I am slowly working on the restoration of two pairs of Smaller Advents - -  one 1972 set with green tweeter and a second 1975 set with the red/orange tweeter. All drivers are good except for this one woofer from the later pair, which was procured via the CSP thread attached. I've never seen a woofer with this sort of damage, but the spider and the voice coil have clearly suffered from an excess of heat build-up, and the fried twisted tinsel wires to the terminals had already frayed to almost complete detachment. Its matching speaker is all fine, but it sounds as if the problem occurred when these speakers were connected to an amp incapable of safely driving 4-ohm speakers. 

This driver still measured at 3.7 ohms before the brittle tinsel wires became completely detached as I inspected and photographed the situation. The cone and dust cap are good; the basket is good; the magnet is strong. The voice coil former has begun to become loose from the cone. The fourth image is looking into the voice coil former and you can see that there is a hidden dust cap inside the famous spitwad outer dust cap, and the tinsel wires seem to penetrate the cone in between the two dust caps.

My question is to solicit suggestions: repair or replace the woofer? Clearly, I could always be on the lookout to buy a replacement driver, but does this appear to be a reasonable candidate for repair? If so, should this only be left in the hands of an experienced professional, or can a reasonably competent DIY-er handle this repair with a few new parts?        

 

woofer 5,6.jpg

woofer 3,4.jpg

woofer 1,2.jpg

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dxho    0

Assuming voice coil/cone kits are available for this driver, you should be able to repair
it/them. I just reconed some HPM 900s. They have a notoriously fragile graphite cone
enclosed by notorious dissolving surrounds. It was not a difficult job- it's just a lot of fiddly
steps. (Replacement factory parts are unavailable, and used ones are pretty rare and pricey).

The question in my mind would be cost of parts and labor vs finding used OEM drivers.
Additionally, new parts may not match original sound. That's true for the AR 12" woofer, for
instance. 

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ra.ra    0

Thanks, dxho, but I've not been able to locate any appropriate repair kits, so....

Bump - - - any other thoughts on whether (and if so, how...) this driver can be salvaged? Thanks. 

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Pete B    0

That is what happens when an amp fails with DC on the output, don't ask how I know!

I had the infamous old Tiger amp fail on an OLA and the spider did ignite and smoke

for a while but went out on its own.  There was A LOT of smoke.

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ra.ra    0

Very unexpectedly, I stumbled upon an orphan Smaller Advent yesterday, so I now have a good donor woofer (c.1976, 3.5 ohms) to cobble together the injured speaker mentioned in previous posts. This "new" one also has an excellent cabinet, grille, badge, and orange tweeter (and has the 4uF and 8uF cap crossover). I even dragged the bleepin' box home on the subway!

I am already in possession of foams that I got from MSound a couple years back, and I'll probably re-foam all four woofers at the same time, but first a question. I know that the inner foam lip sits underneath the cone which makes gluing a bit more difficult, but since it is generally inadvisable (please confirm!) to slice up this unique dust cap to allow the use of shims, is there any recommended method to be able to position the cone height in order to ensure proper foam-to-cone and foam-to-basket glue attachments?   

smaller advent red (C).jpg

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Bamark    0

Ra.ra, you might try emailing your pics and questions to Dave Miller.  He owns Speakerworks here in Tulsa and he repaired the voicecoil on my Advent.  He also removed the spitwad dust cover to repair it, but he is good at what he does.  Those surrounds are an odd size, and there is a guy on eBay that sells them. They fit perfectly, but they have to be installed inverted.  

IMG_0145.JPG

You don't want to buy surrounds that have to "cut to fit".  I've seen that done, and I don't think that is the correct way.

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ra.ra    0

Hi Bamark, and thanks for your input. It's funny that you mention a Speakerworks in Tulsa because just yesterday a Speakerworks in Eugene, Oregon was discussed in a thread about re-foaming AR-7 woofers. Your Advent woofers look just like mine, and yes, I do have appropriate foams and would never consider any "cut-to-fit" solutions.

I'll admit I'm slightly perplexed about the best orientation of the foam - - yours do appear to have the roll positioned to be concave, or "inverted", as viewed from the front. Even though it may not have any noticeable effect on performance, I am sure that this is not the original orientation, as I have always removed original rotted foams that had convex positioning, with the roll bulging forward, and also as seen in this original product brochure (attached). After you mentioned the inverted installation, however, I looked at this with a dry fit comparison (see pic) and, with inner foam lips under the cones, I was surprised to find that the "inverted" profile resulted in a more comfortable dry fit when the cones were in their neutral position relying only on spider suspension. It may be difficult to detect in the pics, but in the convex dry fit, the foam outer lip is kicking up at an angle that seems to make an appropriate glue attachment more challenging.

However, I also found the comments shown here made by folks with substantial experience with this speaker model, and the idea of propping up the cone to make the outer glue attachment sounds like it may alleviate my concern. I may end up trying this method, but I won't get around to this for a few weeks so I'll probably fiddle around some more with dry fit scenarios to see what feels best. Meanwhile, the big question still lingers:

To shim, or not to shim, that is the question:
Whether 'tis nobler in the mind to suffer
The slings and arrows of cutting spitwads,
Or to take Arms against a Sea of 30 Hz tone,

brochure p1.jpg

smaller advent repair tips.jpg

sm. advent foam?.jpg

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Bamark    0

Ra.ra, yea I understand.  Installing surrounds in a concave method runs counter to the norm.  I read and re-read Rick Cobbs (alias "looneytune2001) instructions before installing his surrounds.  He mentions two types of woofers, one with the fiberboard attached to the basket, and one without.  I think that extra thickness is the reason he instructs the surround should be installed "inverted".  Without the fiberboard ring, the inside lip of the surround would fit flush the convex way.  I do know that with the original surrounds on mine, the inside lip of the surround was attached to the underside of the cone.  I know where these speakers came from, so I know they had never been changed.  

In any case, go with what you feel is best for your situation.  If you're satisfied, that's all that matters.  On another note, my noobiness has caused me to re-think the electrolytic caps I installed in my crossovers.  I've read and read, but can't find anyone who has re-capped these particular speakers with a specific metallized/film/foil cap.  I'm open to suggestions with regard to how you intend to recap yours. 

Thanks,

Mark

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Bamark    0

Ra.ra, yea I understand.  Installing surrounds in a concave method runs counter to the norm.  I read and re-read Rick Cobbs (alias  "looneytune2001) instructions before installing his surrounds.  He mentions two types of woofers, one with the fiberboard attached to the basket, and one without.  I think that extra thickness is the reason he instructs the surround should be installed "inverted".  Without the fiberboard ring, the inside lip of the surround would fit flush the convex way.  I do know that with the original surrounds on mine, the inside lip of the surround was attached to the underside of the cone.  I know where these speakers came from, so I know they had never been changed.  

In any case, go with what you feel is best for your situation.  If you're satisfied, that's all that matters.  On another note, my noobiness has caused me to re-think the electrolytic caps I installed in my crossovers.  I've read and read, but can't find anyone who has re-capped these particular speakers with a specific metallized/film/foil cap.  I'm open to suggestions with regard to how you intend to recap yours. 

Thanks,

Mark

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ra.ra    0

Thanks, Bamark, I don't think I was aware that there were two types of woofers regarding the fiberboard, so that rationale from Rick Cobb just might make good sense. Both of my pairs have the fiberboard which, I suspect, is the cause of my minor dilemma.

With the different versions I have (1972 greet tweeter, 1975 red tweeter), they have similar, but different, crossovers. The red uses a 4uF and 8uF cap; the green uses a 8uF and 16uF. Nonetheless, I will not make myself crazy over the cap replacement, and I certainly will not overspend. Is there a particular reason you are re-considering your decision to use NPE caps? I would have to think your new electrolytics are much improved over the cheap caps that Advent originally used.

Not sure exactly how I will proceed, but just off the top of my head, I will probably give consideration to using Carli polyester caps available from Madisound or maybe electrolytic Mundorf-E (Raw) caps available from Parts Connexion. My experience with Erse (poly) caps has shown they are also a very good value, but some highly respected sources have suggested that their electrolytic caps are poorly made and show inconsistent measurements.  

 

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Doug G.    0

Rick Cobb's comments regarding Masonite and all-metal woofers apply to original Advents, not Smaller Advents. Smaller Advent woofers were all the same with the roll poking out, not inverted.

Also, the magnet size on the tweeters is what determines which crossover values were used, not necessarily the cone color. I bet your green tweeter  has a smaller magnet (2.5" square) and your orange tweeter has the larger magnet (3" square).

Although I'm not a believer in different caps having drastically different "sounds", I see no reason to not use N.P. electrolytics as originally used by Advent. In fact, if there is any difference, they will get the speakers to sound as close to original more than other types.

Doug

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ra.ra    0

Thanks Doug, helpful reply, all good comments. Your statements about the various Advent woofers are consistent with what I've seen, but we all know there are sometimes outlier specimens in the Henry Kloss world. And your remarks about the tweeters are also accurate regarding magnet size - - - I generally refer to them by cone color, but your note suggests that perhaps this relationship between cone color and magnet size is not always a consistent one. Good to know.

And I'm pretty much in the same boat as you regarding cap choice. Nothing exotic, keep it simple and inexpensive.

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Doug G.    0

As far as I reckon, there are green tweeters with small and large magnets, depending on vintage. The early ones will have small magnets and later ones, during sometime in 1975, will have large magnets. Orange tweeters will always have large magnets as they are from sometime in 1975 and later.

Good luck.

Doug

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Bamark    0
8 hours ago, Doug G. said:

Rick Cobb's comments regarding Masonite and all-metal woofers apply to original Advents, not Smaller Advents. Smaller Advent woofers were all the same with the roll poking out, not inverted.

Also, the magnet size on the tweeters is what determines which crossover values were used, not necessarily the cone color. I bet your green tweeter  has a smaller magnet (2.5" square) and your orange tweeter has the larger magnet (3" square).

Although I'm not a believer in different caps having drastically different "sounds", I see no reason to not use N.P. electrolytics as originally used by Advent. In fact, if there is any difference, they will get the speakers to sound as close to original more than other types.

Doug

Well Doug, I've pulled out Ricks instruction sheet one more time.🙄  I think this is the part I'm confused on:

"3A. Masonite Fiberboard Insert Type Woofer:

Roll the outer attachment lip of the inverted foam surround so that it is lying on top of the fiberboard.  This will give you easy access to the narrow outer lip for applying adhesive.  Apply the adhesive to the lip and let it tack up for a few minutes. Use a clean swab or your finger and push the entire outer surround lip with wet adhesive on it under the fiberboard."

Is it possible to go under the fiberboard?

"With the entire surround lip now under the fiberboard, gently press the outer lip to the back of the fiberboard from the rear of the woofer through the holes in the frame. If needed, turn the woofer upside down on a smooth flat surface to gain access to the back of the cone."

This part makes no sense, because if I remember the fiberboard on mine are glued on with no room to insert the surround.

When he mentions "older Advent woofers" is that what you refer to as Original Advent woofers?

Not debating, just trying to learn and do it right the first time.  That said, aside from looking odd, is there  any harm in the surrounds being inverted?

Finally, thanks for the opinion on the caps.  On other forums, there are quite a few arguments in favor of never using non-polar electrolytic caps.  I certainly don't mind spending a few $ if it will make an audible difference, but the prices can climb rapidly to the point of diminishing returns on a speaker that did not cost that much originally.  I'm more in favor of spending less and still knowing that at least I updated crossovers.  

Bottomline - it's still about the music. 😉

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Doug G.    0

Gosh, I'm sorry I didn't reply to this yet.

Anyway, I am confused about Rick's instructions too because, on the Smaller Advent woofer, the surround outer flange is placed in the kind of cutout ledge on the upper surface of the fiber board (or I think some may have just been on top of the fiber ring). It sounds like he's talking about the original Advent woofer with the Masonite ring where the outer flange IS under the ring.

Also, the only Advent speaker with the woofer surrounds mounted inverted (concave roll) were the original Masonite woofers. All the rest were convex. It really doesn't make any difference sound-wise but on the original woofers, it would be possible for the surround to rub on the Masonite ring inner edge if the surround were mounted convex.

On the Smaller Advent woofer, I can't see any detriment with mounting the surround concave as long as there are no structures underneath for it to hit. It's just that Advent mounted them convex.

If I were to refoam a Smaller Advent again, I would use the method I use on the all-metal woofer used on the New Advent full-sized speaker. It's a lot easier on any woofer where you have to attach the surround inner flange to the back of the cone.

I attach the outer flange to the frame first which would be in that kind of ledge on the Smaller Advent woofer. The all-metal woofer has a similar ledge for the outer flange. Once that is set up/dry and with the inner flange above the cone edge, run a bead of glue on the upper surface of the inner flange. Then push the cone all the way up and work the inner flange under the cone edge. Done correctly, you won't get glue all over the roll. Then work around the joint two or three times pressing the edges together and, at the same time, pushing on the cone to make sure there's no rubbing of the VC.

There's always a big debate on how to center the cone while refoaming a woofer but the cone is already centered at the spider and the cone will pretty much find its own center during the procedure. I have never had a failure just replacing and checking by pushing around the outside edges of the cone to make sure there's no VC rubbing. Just let the cone find its own place to sit and don't force it in any direction.

The only time you actually have to center the whole cone/VC assembly with shims at the VC is when you recone a driver as opposed to just replacing the surround.

I hope this helps and apologize for this being so late. Family issues have not allowed me to participate in the several forums I am in lately.

Doug

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Doug G.    0

Oh, and as far as capacitors, there is just as much BS in the audio world about them as there is about almost any other subject.

Not that I am against using quality components but I really doubt 99.99999% of listeners can tell the difference between regular non-polar electrolytics being in there or "audiophile quality" caps. A lot of people like to sound authoritative.

Doug

 

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ra.ra    0

No offense taken here, that's for sure. I tend to believe that there are differences in cap quality materials and construction, but I also tend to agree with you that a good inexpensive NPE cap is probably sufficient for the majority of hobbyist speaker restorations. Some of the original caps you find in early Advents (and many other brands) were bargain-basement specials, yet still those speakers delivered spectacular performance.

Opinions are always welcome in forums like this one.

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Carlspeak    0
6 hours ago, ra.ra said:

No offense taken here, that's for sure. I tend to believe that there are differences in cap quality materials and construction, but I also tend to agree with you that a good inexpensive NPE cap is probably sufficient for the majority of hobbyist speaker restorations. Some of the original caps you find in early Advents (and many other brands) were bargain-basement specials, yet still those speakers delivered spectacular performance.

Opinions are always welcome in forums like this one.

I fully agree. NPE's have gotten a bad rap, to the point where a huge bias against them now exists among restorers. That' s mostly due to the fact that NPE's are known to have a life of 15-30 years as opposed to permanent life for film caps. A new, good quality audio grade NPE will restore a speakers original voicing. 

 

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ra.ra    0
1 hour ago, Carlspeak said:

I fully agree. NPE's have gotten a bad rap, to the point where a huge bias against them now exists among restorers. That' s mostly due to the fact that NPE's are known to have a life of 15-30 years as opposed to permanent life for film caps. A new, good quality audio grade NPE will restore a speakers original voicing.

I am very pleased to see that Carl confirms this point of view, particularly since he has conducted and shared such extensive research, measurement, and reporting on various capacitor types. Although I tend to buy into this notion of relative cap longevity (NPE vs. film), I doubt if anyone can state with certainty regarding the projected useful lifespan of a more modern NPE cap - - say, for example, the popular Mundorf-E or similar quality - - in comparison with a cheap, 60's era Callins/Temple capacitor that has repeatedly proven to diverge from its original intended value over time. Also, we know that many NPE's found in AR speakers (I'm thinking Sprague Compulytics) continue to measure within acceptable tolerance even after close to 50 years - - hence, quality of materials and construction does matter. Similarly, how do we really know what the lifespan of film caps is or will be? 

On August 31, 2017 at 2:16 AM, Doug G. said:

A lot of people like to sound authoritative.

That never happens on this forum. :lol:

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ra.ra    0

Well, I stand corrected about projected lifespan of Mundorf-E caps - - just read the literature, doofus! The PLAIN version suggests 5000 hours and the RAW is good for 3000 hours.

Moral: too much cynicism will make one stoopid. :wacko:

mundorf-E raw.jpg

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Carlspeak    0

The Mundorf life spans quoted are for some pretty severe conditions. For example: 85 Deg C equates to 185 Deg. F. Not to worry

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Pete B    0

My opinion is that if you are putting the time in to restore these speakers why not spend a 

few bucks so that they do not need more work in 10-15 years?  In fact if the cap fails and takes

out an expensive tweeter or mid then you might have a hard time finding a replacement.

Electrolytic caps are tricky, they need voltage on them to maintain the "form" which does 

not happen in a crossover.  I always replace caps below 20 uF with films, 100uF and up I put

more thought into changing.  Big caps >500uF be careful not to use a much higher ESR cap

in place of a low ESR type.

There are very valid and good reasons to go to films for small values.

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ra.ra    0

Thanks, Pete, great advice, and despite my devil's advocate position that one does not always need to automatically replace NPE's with film capacitors,  I will most likely follow the practice you have outlined: when replacing low uF value  caps, use some variety of film cap. I am surely not enough of an engineer to comprehend or challenge your comment about sustained voltage , but it certainly sounds like  a well-informed conviction based on substantial experience.  

However, I am unprepared to buy into the popular notion that all NPE's have a very limited lifespan - - caps are surely manufactured to higher standards these days, yet many of us have documented 45 year-old Sprague Compulytics that measure and perform just fine, and they also have an obvious robust build quality to enhance this confidence. I have no doubt whatsoever that some electrolytics are showing their age, drifting from spec value, and affecting the speaker performance after little more than a decade of use, but I do tend to recoil a bit in disagreement when blanket statements are blindly stated over and over and......well, you get my point.....which enhance the oversimplified and oft-repeated line which suggests: 'lytics are bad, films are good. 

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