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Original Large Advent upgrades (recap, binding posts, etc)

S

Starquest

Super Member
I found a pair of vinyl OLA in very good condition for a good price. They're an early build, October 1972. They'd been refoamed and some point, and someone did a good job on that.

Varxw6w.jpg


What they need:

- new fabric (one is stained)
- I'd like to replace the binding posts
- I'd like to discuss recapping them
- someday: replace the vinyl veneer?

This all assumes that I'll be keeping them.

Last weekend I compared them to my pair of Advent/1, which also have not been recapped. I was somewhat surprised at the results -- the /1s are better. They don't have as much bass (to be expected), but the highs are much better. They're also smaller, which is kind of a plus. I found the highs on the OLAs to be underwhelming and not what I want or like in a speaker. (The switch is in the Extended position.)

First topic: capacitors. Today I opened up one of the OLAs, and it's got two 16 uF Temple caps. Replacements of that value are not common, which is kind of baffling to me, since that value is used in so many vintage speakers. I found this on another thread and wonder if it's good advice for these speakers:

Film caps are superior in transparency and reliability, but they have lower ESR (effective series resistance). Translation: if you use same value film for electrolytic, the result will be excessive brightness.

You'll need to add about 0.5 ohm resistance or use a hybrid approach as I did. With my New Advents, I replaced the 13 uF electrolytic with a 12 uf 'lytic and a 1 uF film. Improved transparency without changing the tonal balance.
Click to expand...

mOynVIZ.jpg


I could do a 15 uF NPE and a 1 uF film. Can't easily determine the options for this right now, since parts-xpress's site is having issues.

Sorry for the rambling. TLDR: Is recapping these worth it? If I can't get them sounding how I want, I may as well move them along. Do early OLAs improve dramatically with a recap?
 
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Without getting into too many details (there are lots of threads on OLAs), I'd offer these first-off suggestions:

- Make sure you are getting output from the tweeters (empty paper towel tube between your ear and the tweeter is very helpful)
- I found replacing those caps to be significant. You can go with a 15µF NPE or an economical 15µF film (e.g., Audyn Q4). 15µF is within spec of 16µF±3.2µF. You can add a 1µF cap if you feel you need to (I didn't). I did not worry about the resistance issue.
- If you want to proceed slowly, just replace C1, and don't use "extended", as the latter is the only setting that has C2 in circuit
- Check your R1 resistor. If it is 4Ω instead of 3Ω, you might consider replacing it with 3Ω or paralleling it with a 12Ω (this will get you closer to a "Rev 2" crossover as sorted out by PeteB).
- You've probably seen that the switch/terminal plate also holds the crossover parts, so replacing the screw connectors is more involved than in many other designs.
- Check the air sealing of the cabinet. This mostly affects the bass, but that Mortite used as a gasket material on the woofer can lose some flexibility when aged (more is available at your favorite hardware store).

They look pretty nice. Good luck.
 
It does look like someone was in there based on the two colors of
fiberglass and it is usually just in there in layers. Odd that they didn't
recap them, those look like original caps.

Recap them and try them on normal, not extended, check the resistors
and slip on terminals for corrosion. I agree that 15 uF is fine for the main
cap, and I would reduce the extended cap to 8 uF or less.

How many Watts are you driving them with?

I would not strip the vinyl, instead look for a pair in real wood veneer
and sell what you have unless you really want a woodworking project.
 
As @northpaw says, there are many posts on the Large Advents here and on Classic Speaker Pages, some of the best are by none other than Pete B. Erse audio has 16 uF caps in case you're interested, though many aren't that picky about a 1uF difference some of us are. Just noting, my OLA came with wire nuts on the internal wiring.
 
Pete B said:
It does look like someone was in there based on the two colors of
fiberglass and it is usually just in there in layers. Odd that they didn't
recap them, those look like original caps.

Recap them and try them on normal, not extended, check the resistors
and slip on terminals for corrosion. I agree that 15 uF is fine for the main
cap, and I would reduce the extended cap to 8 uF or less.

How many Watts are you driving them with?

I would not strip the vinyl, instead look for a pair in real wood veneer
and sell what you have unless you really want a woodworking project.
Click to expand...

Thanks Pete. What's an easy way to tell which is the main and extended cap? In the photo, up is up, so is the top or bottom cap the main?

Do I need to do anything else to the crossover if I'm changing the value of the extended cap by that much? Looks like there's a 6.8 uF Audyn cap available. Guessing that would be OK.
 
Are you able to read a schematic, that is the best way to find the caps.

Advents are bright speakers IMO, the extended setting with the 16 uF simply
makes them worse. It is hard for me to say what is right for you, with respect
if you are older with hearing loss for whatever reason then perhaps the 16 uF
cap is right for you. 16 uF or lower does not require any changes.

If you play them loudly with over 100W you should consider changing the tweeter
inductor to 18 ga air core with the value of the Rev 2 design. The tiny inductors in
Rev 1 were a known failure point.

No need to change them if you run with low power and do not blast them.
 
Pete B said:
Are you able to read a schematic, that is the best way to find the caps.

Advents are bright speakers IMO, the extended setting with the 16 uF simply
makes them worse. It is hard for me to say what is right for you, with respect
if you are older with hearing loss for whatever reason then perhaps the 16 uF
cap is right for you. 16 uF or lower does not require any changes.

If you play them loudly with over 100W you should consider changing the tweeter
inductor to 18 ga air core with the value of the Rev 2 design. The tiny inductors in
Rev 1 were a known failure point.

No need to change them if you run with low power and do not blast them.
Click to expand...

I'm not older with any hearing loss. I want better highs from these speakers -- I would not characterize this pair as bright. With that in mind, do I still want a lower-value cap for the extended setting, or just 16 uF for both?

I did have a look at your schematic. Looks like C1 is the extended cap.

The first test was on a 38 wpc amp. I have a 65 wpc amp too, but I won't be driving them with anything near 100.
 
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If you decide to put in new binding posts while you're in there plan carefully to make sure everything fits. I put five way posts on mine and had to flip it upside down to fit without touching the woofer frame and did not want to rebuild the whole thing at that time. (my soldering skills were are still evolving) I'm pretty sure many here would tell you to not bother with the binding posts but I put them on for consistency with my other speakers.
 
Guido57 said:
If you decide to put in new binding posts while you're in there plan carefully to make sure everything fits. I put five way posts on mine and had to flip it upside down to fit without touching the woofer frame and did not want to rebuild the whole thing at that time. (my soldering skills were are still evolving) I'm pretty sure many here would tell you to not bother with the binding posts but I put them on for consistency with my other speakers.
Click to expand...

Hmm, which posts did you use? The depth of the woofer is only about half of the cabinet, so you must have used some rather large parts. I was thinking of using these:

https://www.amazon.com/Eightnoo-Connector-Binding-Amplifier-Terminal/dp/B01N6MCK0E
 
My bad, it wasn't the woofer. I had to flip the three pole switch over on the board because the back end of the new binding posts were in the way. I used the type where they are set in a plastic yoke such as
51yDYixCbvL._SX522_.jpg

Essentially I planned my layout poorly, so my normal and extended are now reversed.
 
Since there are two 16 uF caps in this thing, the software engineer in me wonders why they couldn't have wired it more efficiently and just used one cap.
 
The main cap forms a 2nd order high pass with the inductor to ground.
The second one forms a shelving filter filter with the pad resistor.
The second one is only in the circuit with the extended setting.
No way to simplify.
 
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