Need advice on identifying these Large Advents and path forward

[Mr. Weather]

I picked up these Large Advents for $60 locally as a project.  First, I need help in idenfying them as being OLA or NLA or a combination of the two. Some key points:

• They are the older style (non-bullnose) cabinets
• Newer frame woofers (no masonite).
• One has what looks a serial number inside: A 50766.  If that is a serial number, at least this unit would appear to be an Original Large Advent if my research is right.
• These look to be a mismatched pair with sightly different colored masonite grill frames and different insulation inside (one is pink, one is yellow)
• One has a replacemt vintage Radio Shack tweeter that is wired right off the woofer's positive lead which means it probably never performed as intended.
• The remaining red fried egg tweeter's date is just about impossible to read, AND its grill is slightly pushed in, possibly touching the cone. Not sure if this is visible in the photo.  I will pull it back out slightly.

Second, what are the best potential paths forward?

• Clearly the woofers need new surrounds.
• At least I  need to get a used red fried edd tweeter, but maybe the better play is to replace both tweeters with a newer model from a NLA or similar?
• I assume the fiberglass insulation is Ok to leave there? No need to replace with polyfill?
• Assume the capacitors should be replaced.  My capacitor meter has been flakey so I don't trust it to give me an accurate reading.
• Try to remove and gently wash the grill cloth, or just replace it. 
• The cabinets are in great shape overall, and can probably be carefully cleaned and then polished with one of the usual 'natural'  wax and oil-based products.
• Add replacement badges

Your thoughts are welcome.

I have to keep these photos small in resolution to avoid blowing my storage quota, so I apologize for the small resolution of these.

[Doug G.]

They are original "The Advent Loudspeaker"'s from the early seventies and the original Masonite woofers have been replaced by Jensen-era round magnet woofers, which is OK unless you want them to be authentically original. Both colors of fiberglass are correct with the yellow being slightly earlier.

The fried egg tweeter is probably original with the black tape going all the way across the Masonite square which indicates pre 1975. The Realistic tweeter should be replaced by one just like the other and wired in the same, to the crossover. Wiring a tweeter directly to the woofer is a good way to ruin it by it receiving the full-frequency signal from the amplifier. EDIT: Looking again I see there is a capacitor, presumably in line with the tweeter ,so it will block lower frequencies from the tweeter but it should still be replaced with an original because it won't sound the same. Don't use a "New Advent" tweeter as they are not the same. Using any tweeter other than an original will require a crossover change.

You can try to clean the grille cloth with upholstery cleaner but cloth very close to the original is available if you can't get them satisfactorily clean.

Doug

[RTally]

"Assume the capacitors should be replaced.  My capacitor meter has been flakey so I don't trust it to give me an accurate reading."

Those Temple caps have a reputation of failing, sometimes catastrophically. I would replace them with modern film caps.

[Mr. Weather]

8 hours ago, Doug G. said:

They are original "The Advent Loudspeaker"'s from the early seventies and the original Masonite woofers have been replaced by Jensen-era round magnet woofers, which is OK unless you want them to be authentically original. Both colors of fiberglass are correct with the yellow being slightly earlier.

The fried egg tweeter is probably original with the black tape going all the way across the Masonite square which indicates pre 1975.

Great information. Thanks very much. 

I will remove the grille cloth staples and try to gently clean the cloth.  If it doesn't work, or falls apart, I'll have to go with new.

4 hours ago, RTally said:

"Assume the capacitors should be replaced.  My capacitor meter has been flakey so I don't trust it to give me an accurate reading."

Those Temple caps have a reputation of failing, sometimes catastrophically. I would replace them with modern film caps.

Yep, not surprised to year that. Will replace for sure.

Starting off small, I mixed up some Murphy's Oil Soap and water and scrubbed the cainbets.  The resulting soap-water turned a very dark brown-grey.  It was so dirty I mixed a second clean batch for the second speaker.  I did not notice a huge difference while cleaning them, but the two cabinets do now have a much more identical look when sitting together.  That and the resulting nasty colored water seem to indicate that the work was successful.

I don't like using water on wood, so tried to mimimze the exposure and I dried them with a dry rag while I was scrubbing with the other. Then I let them air dry under a fan just in case.

I will get the capacitors ordered and get the wooder surrounds installed when I have a spare hour or two. I am in the middle of a project to restore a pair of Acoustic Research speakers and that's taking up much of my free time.  I have installed woofer surrounds on two other sets of speakers so hopefully this Advent project will be successful.

Looks like I need to line up a tweeter, although I think I will get the new capacitors installed first so I can listen to this original tweeter and make sure it's not a problem.

 

[Doug G.]

You should try to clean the grilles with the cloth on the frame because if you take the cloth off and get it wet, it will shrink, which is bad.

I cleaned mine by laying them in the bathtub, spraying them with the shower head, gently scrubbing them with detergent and letting them dry. I worked with the frames while they were drying to stop/correct any warping of the Masonite. The thing to do is work fairly quickly to minimize soaking of the frame.

Doug

[Mr. Weather]

18 hours ago, Doug G. said:

You should try to clean the grilles with the cloth on the frame because if you take the cloth off and get it wet, it will shrink, which is bad.

I cleaned mine by laying them in the bathtub, spraying them with the shower head, gently scrubbing them with detergent and letting them dry. I worked with the frames while they were drying to stop/correct any warping of the Masonite. The thing to do is work fairly quickly to minimize soaking of the frame.

Doug

I like that idea but I'm worried that the masonite absorb water and fall apart, bulge, or become distorted.

This may be more work, but I could make temporary frames, transfer the grill cloth to those, wash the fabric on the temp frames, let it all dry, and then re-attach the fabric back to the original frames.

I love the idea to try to clean the original fabric because getting the right fabric is expensive and I'd love to know that these have the original fabric.

[Mr. Weather]

I pulled out the woofers this morning to start re-foaming them.  The first thing I noticed is that one of them had what may be the original gasket between the woofer frame and cabinet, but also had an aftermarket thick foam gasket that had been installed wrong.  The second woofer had the same botched gasket install.  The posiotioning of the new gaskets made it seem like whoever installed them did not know what they were supposed to do or how they needed to be located to make a seal.  Anyhow, those are gone and the original single thin gasket from one woofer is actually intact.

There is also a remnant of an old white-colred sealer or glue around the woofer holes.  PResumably this needs to be sanded off to ensure a better seal.

Finally, one of the screw holes is blown out.   The masonite crumbled in the area.  The only way I know to work around this is to install a T nut with a machine screw in place of the wood screw.  This would ensure a strong bond.  I can't see that the particle board can be repaired well enough to hold the large wood screws that are in this thing.

Finally, I found it intersting that the woofer wires were soldered to the woofer!  I loaded the joints with flux and was able to de-solder the wires fairly easily.

Edited January 24, 2023 by Mr. Weather
spelling

[Mr. Weather]

The woofer surrounds are done.  It's amazing how the old adhesive on these things is diffifult to remove, even with acetone.  I also tried to remove the adhesive from the old failed rear gasket but it was just as stubborn to remove with acetone.  I was able to remove 90% of it.

For the blown out woofer mounting hole, I used a #10-24 T-nut with 2 of the prongs removed.  I put a small amount of epoxy glue to help hold it in place just in case.  The screw is 1.5" too long but works OK.

Once the replacment capacitors are in I'll be able to listen to these things and see where the tweeters are.

[Doug G.]

The thin gasket may not be enough to seal adequately. When the all-metal woofers were installed at the factory, they were fine because the woofer frames were nice and straight and so was the front of the speaker board. After use and the screws being tightened and loosened, the frames and board are not as nice and closely mating and the thin gasket can leak. I have always used Mortite, as was used on the original Advents when resealing any Advent woofer. It assures a tight seal.

After they are back together, push gently in on the woofer cones and they should return to rest fairly slowly. The actual time ,may vary but they shouldn't return immediately. That indicates a large air leak which ruins the frequency response/performance of any acoustic suspension speaker.

 

Doug

 

 

[Mr. Weather]

15 hours ago, Doug G. said:

The thin gasket may not be enough to seal adequately.

Yes, good point.  The single original gasket is very thin, less than 1/16".  For the woofer reinstall, I used Parts Express 1/8" speaker gasketing tape thatI've used in the past.  It did make a good seal and the woofer cone does respond slowly after being pushed in.  Of course on the other cabinet in this pair, with the Realistic tweeter, the woofer cone pops right out becauase there is a large air leak around the tweeter as you can see below.

 

 

[Mr. Weather]

My plan on the grill cloth is to staple it to a temporary frame, below.  This will hopefully keep the cloth from shrinking during cleaning.  The frame is cedar becase that was the first board I pulled off the lumber stack.  The joints are crude mortise and tennon with gorilla glue. Should be enough to withstand some soaking in water.  Note the shop cat enjoying the warm afternoon sun.

As far as actually washing the cloth, I asked my wife who is a laundry wiz. She said to soak in cold water with laundry detergent and avoid any stain removing sprays at first as those might cause lighter spots since the cloth is probably several shades darker than it was originally.

I will have to get some really shallow staples before reattaching the cloth back to the original frame.

[Mr. Weather]

I got the replacement capacitors inststalled but the tweeter output on both speakers is very low.  On the speaker with the original tweeter, I can switch the crossover to 'extend' and get louder output, but the tweeter's volume is a fraction of where it should be. The other speaker with the Realstic tweeter performs simialrly. If I connect either tweeter directly to the speaker wire, its output is much louder.

So I'm thinking something on both crossovers is bad.  What's the most likely culprit?

I found these 0.8mH air core indcutors on parts express for under $5 each.   According to this thread, air core inductors should be adequate. I can replace the resistors but those seem unlikely to wear out.

 

[Mr. Weather]

Great news:  I replaced the capacitors, resistors, and the 2 small inductors on both crossovers and this fixed the problem.  The one speaker with an original tweeter sounds great.  I still need to source a replacement tweeter for the other speaker.

[Mr. Weather]

On the original grill cloth project:  I was able to wash the original grill cloth, and oh man the water was dirty, a grey-brown color.  Yuck.  I moved each cloth to the wooden frame where it was washed and dried.  This avoided any shrinking.   However, ultimately the cloth had enough damage from 50 years that I replaced it.  I was unable to remove the large stains on the cloth by soaking in water with detergent, light brushing, and using stain remover.

The one apparent best source for this cloth, Dorr Mill, was out of stock.  So I used a less expensive and lighter colored cloth from a different source.  I used the "Speaker Fabric Grille Cloth for AR Advent KLH Kloss Dynaco Restoration Repair" from this ebay listing and this seller.  I ended up using 1/4" staples with 2 layers of corrugated cardboard on top of the fabric to precent putting the staples through the front of the board.  I did not replace the black backing cloth. The speakers look great with new grills and badges.

Just need one more tweeter.

[Doug G.]

They look great.

 

Doug

[Mr. Weather]

15 minutes ago, Doug G. said:

They look great.

Thanks!  I suppose the lighter fabric color is sacreligious but they do look much better.  I am still trying to find a single original tweeter (or a pair), but man, the single working speaker sounds fantastic.  Looking forward to getting its companion fully functioning.

Now that the project has shown some benefit, I feel lucky to have found these locally on Ebay. I paid $60, and the quality of the cabinets is fantastic.  I originally was outbid on them, but the speakers were re-listed a week later and got them for $10 less than I had bid the first time.  When I met the seller to do the deal, I learned he is a chronic estate sale buyer and buys spefically to sell on Ebay.  So probably these were an estate sale pick.

[Mr. Weather]

Advent may have made 5 million of these (wild guess) but I'm glad to have found these survivors.

[Doug G.]

As far as the lighter grille fabric, Advents were originally quite a bit lighter than the examples we see today which have darkened, some of them badly, depending on the environment. My very early pair I bought from a guy originally from Cambridge whose parents bought them from the factory, had grilles beyond redemption, as badly as I wanted to resurrect them. They were actually yellow.

Doug