Original Large Advent—I think. Questions.

[patrickw]

I picked up this pair of Original Large Advent. Or at least I think they are. I do not know my Advents that well. 

I have not opened these up yet. Obviously they need new surrounds and I was also going to replace the caps while I was at it. And I had plans on lightly sanding and oiling the cabinets to make them sparkle again. 

They have identical intact tags that say Advent Loudspeaker on back with serial #s M 01535 and M 3057. As you can see from the photos, they look identical with the grilles on, but off one has the Masonite woofer and the cage over the tweeter. The person I got them from (part of a larger deal) said he bought them from the original owner and never got around to updating them,  now he was moving houses and decided to sell rather than fix them up. 

My question is, could one of these been refurbished and thus had drivers updated? Does it matter that the drivers are different? I would not think the different drivers were a manufacturing change when they are only 1500 apart in serial numbers. I assume with such close numbers they would have the same drivers. My thought was to get the correct surrounds and just replace the foams. My understating is that both of these woofers, despite the difference in rings, take the same replacement foam. 

Secondly, with the different drivers, would the crossover be different?

Lastly, should I just replace the drivers in the one speaker with a masonite woofer and tweeter with the cage?  Certainly I can find replacement woofers and tweeters on eBay. The cabinets look close enough that replacing the drivers would create a visually identical set. But would they sound identical?

These photos are from the seller. I can post more photos if needed. 

Thanks in advance of any insights!

—Patrick

 

 

[Doug G.]

Hi Patrick,

Those are early Advents with those serial numbers and before Advent standardized the "A" suffix. They would have come with Masonite woofers and tweeters like the one on the left speaker, without and grille/cage on the front. The left tweeter and right woofer are probably original and the left woofer and right tweeter, replacements.

As to what to do with them, if you want to be absolutely original, you would want to get a tweeter without the grille for the right speaker and Masonite woofer for the left speaker. Soundwise, it doesn't matter as the drivers were always made to sound the same, regardless of iteration.

I have a pair of very early ones also and they both have Masonite woofers but the woofers are not original. I have the original woofers but the previous owner had replaced the original cones with plastic cones so I am waiting to find original type cones to rebuild the original woofers. Whether I ever actually do it is a separate issue. I have the original "cageless" tweeters, too, but one of them has a broken lead right where it goes into the  voice coil by the edge of the dome. So, they both currently have later tweeters with grilles/cages. I don't let it bother me too much. More important to have them operational.

So, as far as how they sound, as long as you have real Advent drivers in them, they'll be OK.

As far as the crossovers are concerned, the only way to tell is to see them and test the capacitors and verify that the resistors and inductors are OK. I am of the opinion that even capacitors don't automatically need to be replaced if they check out OK. Others replace them just because of age. That's your decision. If you do replace them, I would just use modern equivalent non-polarized electrolytics.

Good luck.

Doug

[patrickw]

Hi Doug,

Thanks for the informative reply! I do appreciate it. So it would seem like my hunch that some drivers have been replaced and updated was correct. 

Interesting that the cage free tweeters are the original. All the ones I looked at recently had cages so I assumed that was the original. I agree with you, the most important thing is to get them operational. 

Do you know if the crossover changed with these original drivers?  I saw the Human Speakers page — https://www.humanspeakers.com/o/advent-large.htm — and it made it seem like the crossover evolves as the drivers evolve. Like you suggest, my instinct was to replace old caps with like values of new poly caps. 

I am going to do some testing of these (I have not plugged them in yet due to the gone surrounds) and see exactly what I have in terms of functioning speakers. I will keep folks updated. 

Thanks!!

 

[Doug G.]

The tweeters originally had virtually no protection from being pushed in. In the first attempt to alleviate the field issues, Advent placed a window screen type grille directly into the tweeter opening in the Masonite grille frame. Then, they mounted an extra block with Velcro right under the tweeter to keep the grille, itself, from being pushed in. Finally, they put the cage type grille right on the Masonite frame of the tweeter. This proved to be effective although Advents still show up with the cage type grille pushed into the tweeter dome.

This all happened in a relatively short period of time and by the end of 1971 or early 1972, they had the cage type grille on the tweeters. Advent even offered the grilles, free of charge, to owners of earlier speakers, to mount them themselves if they wanted.

The crossover was changed, more as an effort to ease the tweeter from having to reproduce the lowest frequencies of its range as there were problems with owners blowing them in the field, too.  Also, it was to make the integration of the woofer and tweeter smoother at the crossover point. A 16uF-16uF combination was first used for the two electrolytic capacitors and that was changed to a 16uF - 8uf combination in 1975. The resistor was changed and the inductors beefed up, too.

The best place to see the differences is Pete Basel's site, here:

http://baselaudiolabs.googlepages.com/ADVENT_LA_XO.html

 

Doug

 

 

[patrickw]

Hello Doug,

Thank you for all your insights! This is really helpful. And thank you for sharing Pete Basel's site, I certainly learned a lot from that resource.

I am back to finally to these speakers. I opened them up for the first time tonight and found another interesting thing. They both have the same crossover, however the one with the metal frame woofer and original tweeter had a 16uF cap connected to the common terminal, but the caps connected to the brightness switch (or tweeter switch, whatever it should be called) were two 8uf caps. The one speaker with the original woofer had two 16uf caps. All of the caps were the black with red end non polarized type, all 50v. So interesting that Advent also used different cap values. I wonder if when the woofer was replaced they replaced the one 16uf cap to two 8uf caps. 

I am ordering up some new caps and I am going to go with just 16uf to keep it simple. 

I am also thinking of buying one masonite woofer off eBay, just to have the woofers the same. Am I wrong, or do the two different types of woofers have a different configuration for the foam. I know the masonite woofers have inverted foam. But from what I can tell the steel frame woofer has outward facing foam.  That discrepancy makes me think I should just go with two original woofers. 

Thanks again!

Patrick

[Doug G.]

If the two 8uF caps are connected together, each end to each end (in parallel), that equals 16uF so either Advent did that or whoever did work on them later, most likely the latter.

The only real reason to get another Masonite woofer  and another "cageless" tweeter is for originality and so the two speakers are the same. Soundwise, it won't matter. That being said, it would bug me they aren't the same. In fact, it bugged me on one of my pairs that, when they were refoamed, in the past, whoever did it put different diameters of dust caps on the woofers so I had to match them up. It still bugs me a little bit that they are too large a diameter for original Advent woofers but I had to cover up the old glue line. Of course that they are porous caps results in no change to the sound.

The Masonite woofers had the surrounds installed inverted (roll poking away from you) to avoid any possible interference between the roll and inner edge of the Masonite ring when the cone moves in and out. The all-metal woofer doesn't have that possibility, of course. Again, soundwise, it makes no difference.

Doug