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Refoaming New Advent Woofers - Edge Height - Details


Pete B

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I mentioned in this thread below that the New Advent woofers (professionally refoamed) seem to have the rest position of the cone about 1/16" back:

http://www.classicspeakerpages.net/dc/dcbo...1356&page=#1356

These woofers seem to bottom much more easily than a pair of older Masonite types that were properly refoamed.

I have another pair of New Advent woofers that seem to be original and never previously refoamed. I've glued new RSSOUND foam to the cone only and the new edge seems to "find" the correct position on the frame by just falling into place. However, laying a flat edge against the spider I notice that this driver also seems to have the center of the spider about 1/16" in toward the magnet. Considering this further I notice that the foam, while looking wider than the typical .5" wide type, does not look as wide as in this picture:

http://www.snappymgr.com/images/items/1413.../14131773-5.jpg

The roll in the picture looks more like a C shape rather than a perfect half circle. I find that if I push down on the center of the not yet fully glued edge to flatten it more like a C shape, the glue edge moves up higher on the frame. It seems that perhaps the edge should be glued about 1/16" higher up on the frame than how it naturally falls. One has to wonder what sort of jigs, if any were used at Advent to do this job.

Any thoughts or suggestions before I finish refoaming this woofer?

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Pete,

Could it be that that old surround in the picture has just distorted from age and that it was originally normally rounded?

I think I would just glue the surround to the frame where it naturally comes to rest.

Doug

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Guest One-Shot Scot

>I mentioned in this thread below that the New Advent woofers

>(professionally refoamed) seem to have the rest position of

>the cone about 1/16" back:

>

>http://www.classicspeakerpages.net/dc/dcbo...1356&page=#1356

>

>These woofers seem to bottom much more easily than a pair of

>older Masonite types that were properly refoamed.

>

>I have another pair of New Advent woofers that seem to be

>original and never previously refoamed. I've glued new

>RSSOUND foam to the cone only and the new edge seems to

>"find" the correct position on the frame by just

>falling into place. However, laying a flat edge against the

>spider I notice that this driver also seems to have the center

>of the spider about 1/16" in toward the magnet.

>Considering this further I notice that the foam, while looking

>wider than the typical .5" wide type, does not look as

>wide as in this picture:

>The roll in the picture looks more like a C shape rather than

>a perfect half circle. I find that if I push down on the

>center of the not yet fully glued edge to flatten it more like

>a C shape, the glue edge moves up higher on the frame. It

>seems that perhaps the edge should be glued about 1/16"

>higher up on the frame than how it naturally falls. One has

>to wonder what sort of jigs, if any were used at Advent to do

>this job.

>

>Any thoughts or suggestions before I finish refoaming this

>woofer?

Now this is something that I had never considered. It never occurred to me that the surround material might be forced from its natural shape into an expanded version which could be employed to restrict the movement of the woofer cone. I too have some original Advent woofers, but I'm wondering if matching their surround material attachment locations would necessarily make for an accurate repair.

I once paid way too much to have a pair of Advent Steel Frame woofers "professionally" re-foamed with surrounds that were too thick and whose dimensions did not match those of the originals. After that bad experience, I figured that I couldn't do any worse if I did the job myself.

After looking all over the Internet, I finally decided that Woofer Repair was the most knowledgeable and most likely to have the correct surround material. Unlike most other sites, Woofer Repair said that it was necessary to shim the voice coil to ensure it is centered. A voice coil that is not centered can rub either the center pole or the magnet. This site also provides a DVD (or downloadable movie) containing complete woofer repair instructions.

Anyway, I shimmed the voice coil, glued the center of the surround to the woofer cone and dropped the glued, outer edge of the surround down until it just touched the basket. The shims held the woofer cone in place, so I patted the glued edge down and let it dry. The repaired woofers sound terrific, especially more so when compared to the "professionally" repaired pair.

I didn't realize that I could have jockeyed the woofer cone height down a little, causing the surround to spread out. It would be good to hear if anyone else has thoughts on this matter.

http://www.wooferrepair.com/advent.html

The kits sold by Woofer Repair look a lot like the ones sold by Parts Express:

http://www.partsexpress.com/pe/showdetl.cf...number=260-953"

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Hi Doug,

I'm fairly sure that's how it looked and referring to my measurements the linear one way Xmax is only 1/8", being off 1/16" is half of that already small value. I didn't remove the old foam completely from the other woofer and measuring seems to support this theory that it needs to be shifted up about 1/16".

>Pete,

>

>Could it be that that old surround in the picture has just

>distorted from age and that it was originally normally

>rounded?

>

>I think I would just glue the surround to the frame where it

>naturally comes to rest.

>

>Doug

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  • 2 months later...

I confirmed here that the LA woofer linear Xmax is 1/8" by measuring and using a spread sheet for calculations:

http://www.classicspeakerpages.net/dc/dcbo...1356&page=#1373

Here's a picture of the 5/8" long voice coil:

http://members.aol.com/basconsultants/ADV_VC1.jpg

It can be seen that a 1/16" offset is half of the linear throw and is obviously significant.

I should mention that there is a flat ledge where the foam is attached so the front to back position is fairly fixed. What I did find in finishing this refoam is that there is some give as to the position of the foam on that ledge, and I found it better to go toward the outside of the lip. I measured the distance from the edge of the frame to the edge of the foam in an original driver and used that distance as a guide. Obviously, the foam used has to match the original for this to work and the RSSOUND foam seems correct.

The foam in the final job measures 11/16" wide, 1/16" over 5/8", and it looks more like that photo in the first post.

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This thread brings up an issue that's been bothering me for several years now when seeing requests for refoaming advice & now that I own a pair of Smaller Advents in need of refoaming it *really* has me concerned:

Most of the refoaming kits I see being sold as replacements for woofers designed for acoustic-suspension enclosures do not even start to resemble the woofer's original surround. The replacements are almost always too narrow and as mentioned here, do not have the same shape: most original surrounds in cross-section that I have seen (Advents made in 1984 and newer) have a sort of asymmetrical & flattened "wave" shape but the replacements are just simple half-circles.

And this especially worries me: are the replacements as COMPLIANT as the originals? Or to use a non-technical term :^) is the new surround as mushy? Acoustic-suspension woofers almost always have very compliant surrounds compared to woofers intended for bass-reflex enclosures......and the latter design seriously outnumbers acoustic-suspension models in the market place. I would think the manufacturers of replacement surrounds would design their products to fit the majority of woofers, not the "niche" models.

All this implies to me is that the replacement surrounds will not allow the woofer to move properly and in turn the rebuilt woofer won't produce as much bass as the original.

Thoughts?

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  • 3 weeks later...

>This thread brings up an issue that's been bothering me for

>several years now when seeing requests for refoaming advice

>& now that I own a pair of Smaller Advents in need of

>refoaming it *really* has me concerned:

>

>Most of the refoaming kits I see being sold as replacements

>for woofers designed for acoustic-suspension enclosures do not

>even start to resemble the woofer's original surround. The

>replacements are almost always too narrow and as mentioned

>here, do not have the same shape: most original surrounds in

>cross-section that I have seen (Advents made in 1984 and

>newer) have a sort of asymmetrical & flattened

>"wave" shape but the replacements are just simple

>half-circles.

>

>And this especially worries me: are the replacements as

>COMPLIANT as the originals? Or to use a non-technical term :^)

>is the new surround as mushy? Acoustic-suspension woofers

>almost always have very compliant surrounds compared to

>woofers intended for bass-reflex enclosures......and the

>latter design seriously outnumbers acoustic-suspension models

>in the market place. I would think the manufacturers of

>replacement surrounds would design their products to fit the

>majority of woofers, not the "niche" models.

>

>All this implies to me is that the replacement surrounds will

>not allow the woofer to move properly and in turn the rebuilt

>woofer won't produce as much bass as the original.

>

>Thoughts?

Hi, Yes I understand your concerns, and I've measured several drivers that I've refoamed. I've found the foam from RSSOUND to be highly compliant and I like it for this reason. The Advent and AR 11/12 foam is a perfect fit, and I obtained very low Fs for the drivers after refoaming. Measured and found different thicknesses in the foam from different suppliers.

Also refoamed several drivers using kits that friends had, and wanted me to use. These generally had slightly higher Fs than spec, however because the air spring dominates in an Acoustic Suspension system, the system resonance was still within spec. I would have preferred the better foam, but the results were acceptable.

I agree that if Advent used a larger edge it was part of the excellent design and it should be retained whenever possible.

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Guest Celereno

I placed an order from RSSOUND back in December, never heard back from them. Tried emailing and calling. Does anybody know if they are still in business?

Thanks

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Guest Robert M

One thing I noticed on the LA woofers (in particular the masonite ring type), was that there was spider sag. As a result, the edge of the cone was not even with the basket lip where one attaches (underneath for the masonite, on top for the stamped basket). What I did for these, was put an L-pad I salvaged from some Criterion A100 speakers (garbage) in series with a D or C battery. What this allowed me to do was raise the lip of the cone up to the proper location and hold it there. I then glued the outer lip to where it was needed.

I no longer want to deal with www.rssound.com and I suggest others skip them altogether. I filled out the form in October for some LA foams. After not receiving them by December, I emailed several times, with no response. This seems typical with them. They never did charge my card, but did waste my time. If you want LA foams, I suggest looneytune2001 on eBay, based on some discussions with him and the photo, they are the same as rssounds.

As far as this foam (either rssound or looney) being correct and whether it is EXACTLY the same, all I can say is that I have scraps of the original and the width as well as the thickness were perfect matches. Is it absolutely correct? Who knows. But it does appear to be the best thing out there to refoam these. They certainly work much better than having no foam at all :P.

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Concerning spider sag, remember that the cone is faily heavy so if you examine the woofer face up, the cone will be offset in due to the cone weight. I usually find that if I flip the woofer over, it sags about the same amount the other way.

There was some delay in the first order I made with RSSOUND, the second went smoothly, both were filled in the end and I'm willing to wait to get the right foam.

I've heard problems with many other sources also, it's difficult and I am interested in another reliable source.

I've read good things also about looneytune2001 on ebay, but I've not tried their foam. I like the fact that I'm able to just buy what I need from RSSOUND and not a full kit everytime.

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