OLA refurb

[ShawnS]

I bought a pair of OLAs and Advent/2s from an estate sale here in Houston.  I knew the folks and I knew he took care of his A/V equipment.  Both pairs are in great condition on the exterior.  It seems that he had the woofers replaced on the /2s, so they're working fine.  I'll be ordering a foam kit for the woofers on the OLAs, but read somewhere to replace the caps on them while I'm in there.  Any details on these?  Do I need them if I plan to keep them on normal?

Also, I would like to know when the OLAs were made.  They are serial# 12710 and 12715.

Any other ideas while I'm working on them?

Thanks!

Shawn

[Doug G.]

The "large" Advents are pretty early ones without the grille on the tweeter and the additional Velcro block under the tweeter to keep the speaker grille frame away from the tweeter, in one of the efforts to avoid the tweeter domes getting pushed in.

They look like they are in beautiful condition. The capacitors are very likely to be two 16uF in each one and they should at least be tested to see if they are still in spec as they are over 40 years old. If they are out of spec., replace them with modern equivalents. Install the surrounds exactly like the originals were. Those serial numbers indicate sometime in 1970 or maybe 1971. I lean toward 1970.

Doug

[JKent]

http://baselaudiolab.com/ADVENT_LA_XO.html
 

[ShawnS]

Thanks for the info Doug and JKent!  I ordered the re-foam kits from Simply Speakers and watched their video on the process.  Looks simple enough.

[Alkaloid]

Shawn make sure you shim the voice coils to make sure they are centered and not scraping. I will try to post a few pics. Also there is some fantastic rope caulking for the gasket when you put the woofers back in the cabinet. B2WT Mortite weather strip and caulking cord. Comes in a roll and 2 strips wide applied to the edge of the woofer is perfect. My pics are too large to attach. You can get this a Home Depot or Lowes, very cheap.

Here is a link to a video on Youtube all about capacitors. Shows you how to measure them to see if you need to replace yours.

https://www.youtube.com/watch?v=X4EUwTwZ110

I refurbished a pair of OLAs that like yours were in awesome shape cosmetically. I sent the woofers out to Rich So who is of ADS fame. He did the surrounds in butyl rubber.

They will be good to go now for another 50 years without rot. My pair had all the paper work intact on the backside along with the original warranty cards. I did the grill cover cloth as well. Good luck with your pair and enjoy!!🔊

 

[ShawnS]

Those look spectacular!  Thanks for the extra advice and links, I'll definitely use them.  I really like the original warranty and instruction sheets on mine too.  I just can't wait to get them hooked up and listen to them.  My Advent/2 pair are great, but they're definitely bookshelf speakers.

Thanks again!

[blanddawg625]

On 10/30/2021 at 4:05 PM, Alkaloid said:

Shawn make sure you shim the voice coils to make sure they are centered and not scraping. I will try to post a few pics. Also there is some fantastic rope caulking for the gasket when you put the woofers back in the cabinet. B2WT Mortite weather strip and caulking cord. Comes in a roll and 2 strips wide applied to the edge of the woofer is perfect. My pics are too large to attach. You can get this a Home Depot or Lowes, very cheap.

Here is a link to a video on Youtube all about capacitors. Shows you how to measure them to see if you need to replace yours.

https://www.youtube.com/watch?v=X4EUwTwZ110

I refurbished a pair of OLAs that like yours were in awesome shape cosmetically. I sent the woofers out to Rich So who is of ADS fame. He did the surrounds in butyl rubber.

They will be good to go now for another 50 years without rot. My pair had all the paper work intact on the backside along with the original warranty cards. I did the grill cover cloth as well. Good luck with your pair and enjoy!!🔊

 

Please don't shim the woofers. Rick Cobb sells surrounds with a test tone CD for centering. And changing the surround material will affect the sound.

[JKent]

4 hours ago, blanddawg625 said:

Please don't shim the woofers. Rick Cobb sells surrounds with a test tone CD for centering. And changing the surround material will affect the sound.

There is some disagreement on this subject but shimming is the only way to ensure the VC is centered. AND it has the added benefit of allowing you to position the cone up or down as you work on the surrounds. My advice: Always shim.

Edited April 4, 2023 by JKent
Incorrect information

[Aadams]

On 10/30/2021 at 4:05 PM, Alkaloid said:

I sent the woofers out to Rich So who is of ADS fame. He did the surrounds in butyl rubber.

From a 2021 post above.

[JKent]

1 hour ago, Aadams said:

From a 2021 post above.

Ah. Missed that. I was looking at the OP’s info. 
Yeah—changing the surrounds from foam to rubber will very probably affect the sound. 
I just edited my previous post to remove the erroneous assumption. Thanks for pointing that out. 

[Doug G.]

Over many refoams, I have never shimmed the VC. Recones, yes, you have to but refoams, no.

Doug

[RoyC]

On 4/8/2023 at 5:12 PM, Doug G. said:

Over many refoams, I have never shimmed the VC. Recones, yes, you have to but refoams, no.

Doug

I use shims whenever possible. An added benefit is the ability to manipulate the height of the cone using the friction they provide.

I've repaired more than a few woofers with rubbing voice coils due to botched foam replacements.

Roy

[Doug G.]

Well, as I have written quite a few times before, the VC is already centered at the spider in the typical driver unless there is a problem with the spider which is rare. The only thing that needs to be done is to ensure the VC stays parallel to the magnet/pole piece, all along its length, during the refoam and this is easily accomplished by pushing down along the perimeter of the cone all the way around as the glue sets. This guarantees the cone is parallel to the pole piece because pushing on the perimeter, all the way around, slightly biases the VC into a "slanted" position and it would rub on the pole piece if not parallel/centered.

I have done it this way during my whole long-time experience with refoaming drivers and have  never had a failure.  The procedure doesn't have to way more complex than it need be. The tone thing is even unnecessary.

 

Doug

 

 

 

 

[RoyC]

14 hours ago, Doug G. said:

Well, as I have written quite a few times before, the VC is already centered at the spider in the typical driver unless there is a problem with the spider which is rare. The only thing that needs to be done is to ensure the VC stays parallel to the magnet/pole piece, all along its length, during the refoam and this is easily accomplished by pushing down along the perimeter of the cone all the way around as the glue sets. This guarantees the cone is parallel to the pole piece because pushing on the perimeter, all the way around, slightly biases the VC into a "slanted" position and it would rub on the pole piece if not parallel/centered.

I have done it this way during my whole long-time experience with refoaming drivers and have  never had a failure.  The procedure doesn't have to way more complex than it need be. The tone thing is even unnecessary.

Hi Doug,

Some voice coil gaps are large and forgiving (such as Advent), but others are small and much less so. I have repaired more than a few unsuccessful re-foam jobs due to the difficulty of navigating these gaps.

I have been at this for decades professionally, and have had this discussion with some very respected pros such as Bill LeGall of Millersound...who uses shims whenever possible. In our work, along with the small gaps mentioned above, a problem with spider orientation is not as rare as you may think. In this case, using shims will greatly assist in the optimization of the voice coil's clearance to the walls of the magnet. Some spiders are very soft and/or worn which can somewhat increase the degree of difficulty as well. Shims are also helpful when the cone edge is not level with the basket, as in the case of some iterations of AR woofers, when friction allows the cone to be manipulated and centered at the same time.

With that said, a practiced hand will likely have a high degree of success with Advent woofers using your method. I also agree regarding the "test tone" method. Might as well just use a battery (though it still won't correct for the issues mentioned above).

Roy

 

[Doug G.]

Hi Roy,

When I reread some of my posts, I realize they come off as maybe being disparaging to other methods which is not my intention. I'm just relating my experiences. I agree that if there IS doubt, it is better to shim. I just have a tendency to want to maintain originality when possible.

I do want to mention I have been at speaker repair for many years, also. I remember repairing little 4" and 5"X 7" speakers in the sixties when I was a kid when, for one reason or another, the cone warped or tore or whatever. So, I am not writing from a neophyte perspective.

Doug

[RoyC]

2 hours ago, Doug G. said:

So, I am not writing from a neophyte perspective.

Doug

I know you have experience, Doug. (Sorry if I implied you didn't.) I try to gear my posts toward the neophytes reading the forum...and dealing with a botched re-foam job is very difficult due to the tenacity of new adhesive. Been there, done that...

On a completely different subject, I also know you have some experience with the Smaller Advent. I plan on starting another thread on the subject, but after working on a number of SA specimens in recent months, I may be able to shed a bit more light on previous discussions regarding tweeter and crossover differences. I may have missed it along the way, but I never realized there was a 4 ohm and an 8 ohm version of the SA woofer, which could explain some of what we've seen. We can compare notes when I get mine organized.

Roy

[Doug G.]

I thought the woofers are always the same but they changed the tweeter to use the same, larger magnet version and made a crossover change to match the efficiencies of the tweeter and woofer in the Smaller Advents.

Doug

[RoyC]

8 hours ago, Doug G. said:

I thought the woofers are always the same but they changed the tweeter to use the same, larger magnet version and made a crossover change to match the efficiencies of the tweeter and woofer in the Smaller Advents.

Doug

I did to, but it now appears there was more to it. 🙃 I'll post a photo and more information in a new thread.

Roy

[Pete B]

If you found an 8 ohm SA woofer I'd say that it was probably worked on with a VC replacement or

they mixed up some LA woofer voice coils in with the SA ones.  It is in the "engineering" sales 

literature that while they SA maintains the same F3 as the LA they lowered the impedance to 4 ohms

in order to keep the system voltage sensitivity as close to the LA as possible.

However, even the LA is lower than 8 ohms with the DCR usually measuring under 5 ohms.

When I worked on a few SA woofers I was surprised how similar, if not the same the magnet pole

piece, VC were to the LA, probably a parts commonality thing for mass production.

I repair two SA woofers here with some notes:

https://audiokarma.org/forums/index.php?threads/small-advent-woofer-repair-some-measurements.819443/

 

I measured a DCR of 3.3 ohms for the SA woofer.

[Pete B]

I have a pair of LA woofers here that were refoamed by Bill LeGall of Millersound about 6 months

ago and there's no sign of the dust caps being removed.

[RoyC]

6 hours ago, Pete B said:

If you found an 8 ohm SA woofer I'd say that it was probably worked on with a VC replacement or

they mixed up some LA woofer voice coils in with the SA ones.  It is in the "engineering" sales 

literature that while they SA maintains the same F3 as the LA they lowered the impedance to 4 ohms

in order to keep the system voltage sensitivity as close to the LA as possible.

However, even the LA is lower than 8 ohms with the DCR usually measuring under 5 ohms.

When I worked on a few SA woofers I was surprised how similar, if not the same the magnet pole

piece, VC were to the LA, probably a parts commonality thing for mass production.

I repair two SA woofers here with some notes:

https://audiokarma.org/forums/index.php?threads/small-advent-woofer-repair-some-measurements.819443/

 

I measured a DCR of 3.3 ohms for the SA woofer.

Agreed, Pete...until this last batch I worked on. We can put our heads together in a new SA thread. :)

[RoyC]

Please don't shim the woofers.

6 hours ago, Pete B said:

I have a pair of LA woofers here that were refoamed by Bill LeGall of Millersound about 6 months

ago and there's no sign of the dust caps being removed.

I visited with Bill at his place some years ago. At the time he said he uses shims whenever possible. As an aside, he had every part imaginable in that place (including dust caps), and gifted me some nos AR voice coils. Nice guy!

My primary reason for my previous post(s) was in response to the curious advice posted earlier in the thread..."please don't shim the woofers". There are more than a few people doing this for the first time, and that wasn't a particularly helpful recommendation, imo. It's hard to believe some of the re-foam disasters I saw at the shop.