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'78 New Large Advents - One only sounds good on Extended, why?


Mr. Papercuts

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I just bought two 1978 New Large Advents and replaced the foam surrounds. When I hooked them up, with both of the High Frequency Control switches set to Normal, one of the speakers sounded a little muddy. When I switched that speaker to Extended, it sounds like the other speaker, which is still set to Normal.

So my speakers sound great, but one is on Extended and one is on Normal. What could this signify?

Thank you for your help!

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It suggests that one or both of the attenuation resistors has gone open circuit.

Extended shorts both of them out.

This page might help, I am the author, see section 3.1:

http://baselaudiolab.com/ADVENT_LA_XO.html

I strongly suggest that you recap them while you are in there.

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Possibly one of the bat switches has become rotated. Does the speaker that is at Normal become more or less bright when you set it to Extended?

It becomes brighter, but not by much. On the other speaker it is a drastic change.

It suggests that one or both of the attenuation resistors has gone open circuit.

Extended shorts both of them out.

This page might help, I am the author, see section 3.1:

http://baselaudiolab.com/ADVENT_LA_XO.html

I suspected this might be the case. Thank you for the link. Is a repair necessary if I am happy with the sound the speaker makes on Extended? In other words, if I leave it alone am I inviting further damage?

I strongly suggest that you recap them while you are in there.

Why?

Thanks again.

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Hey Mr. P

Pete can certainly answer for himself and he knows much more about the NLA and speakers in general than I, but....... The answer is pretty simple. Your NLA crossovers consist of a switch, an inductor (coil), resistors, and a capacitor. Inductors last forever (well, almost). Switches and resistors usually last a very long time, but Pete suggested there may be problems with your resistors. Electrolytic capacitors tend to drift or leak over time. They're good for 15 or 20 years, maybe longer, but they do have a finite lifespan. The non-polar electrolytics in your Advents are at least 33 years old.

There is a schematic for the NLA on Pete's site. It shows one 13uF cap. Replace that with a film cap. It shows 2 resistors: a 1 ohm and a 1.5 ohm. Assuming that you replace the resistors it makes absolutely no sense to retain the ancient caps (even though the ones Pete tested 5 yrs ago were pretty good). With new film caps and new resistors you can hand the speakers down to your grandchildren.

13uF is a bit of an oddball value. No problem—just get 2 caps that add up to 13, like a 10 and a 3, or a 12 and a 1. Doesn’t really matter. Many people like Dayton or Solen caps from Parts Express. PE has the resistors you need, too. Get a 1 ohm and a 1.5 ohm 10 or 12 watt resistor (for each speaker). I like the Mills resistors but you can also use the Dayton “non-inductive” resistors or the regular 10 watt wirewound.

If you shop Madisound instead, you can get inexpensive Carli caps. They also have Solens and others. If you want to go super inexpensive, get their 10uF “surplus caps” for 60 cents each, plus a surplus Panasonic or Richey 2.7 (close enough) for 30 cents, or a Carli 3.3 (also close enough) for a buck five. If you shop Madisound, you can get Mundorf resistors in 1 and 1.5 ohm values, or 15 watt wirewound.

Gee—if you use surplus caps and wirewound resistors the total cost for TWO speakers would be $3.60. Unfortunately, the shipping is probably more than that :(

Kent

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Thank you, those are very excellent and clear instructions! I have more questions, just for my personal education.

Pete suggested there may be problems with your resistors. Electrolytic capacitors tend to drift or leak over time. They're good for 15 or 20 years, maybe longer, but they do have a finite lifespan. The non-polar electrolytics in your Advents are at least 33 years old.

What do you mean by "drift"? Does drifting effect the sound if I'm bypassing them with the Frequency switch? By leak, do you mean they would leak a battery-acid-like substance, or a substance that could damage the other components?

There is a schematic for the NLA on Pete's site. It shows one 13uF cap. Replace that with a film cap. It shows 2 resistors: a 1 ohm and a 1.5 ohm. Assuming that you replace the resistors it makes absolutely no sense to retain the ancient caps (even though the ones Pete tested 5 yrs ago were pretty good). With new film caps and new resistors you can hand the speakers down to your grandchildren.

Should I replace these parts if I like the way they sound as they are? Right now, with the switches on Extended, they sound incredible. Definitely the best speakers I've owned, and I'm sure my stereo doesn't do them justice. Is replacing the resistors and capacitors going to improve the quality of the sound? Even if I don't have a high-level stereo?

When you say caps, you mean capacitors, not the dust caps, correct?

In order to replace the parts, wouldn't I need a soldering iron to do some soldering, and some of that amber adhesive shown in the diagrams, as well?

I'm not familiar with electrician work, and while I'm sure I could handle it, I'm cautious about opening them up and making a mistake during the repair, when they already sound better than any speakers I've ever owned. I'm quite satisfied with the way they sound now, I wouldn't derive any satisfaction from knowing they have newer parts if it doesn't improve the sound quality. If they don't "sound broke", should I be fixing them? I'm tentative because money is a huge factor in my life right now, and if I damage these speakers trying to fix a problem that I don't even notice, I won't be able to replace them. This is the first time I've owned nice speakers in my life and I'm loving every second of them.

I'm not rejecting your suggestions, I'm just curious. Thank you both for your expertise! I'm learning a lot.

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Short answer: Leave them alone and enjoy! :)

As to the specifics:

  • by drift I meant "change in value over time
  • Leak: Yes, they do contain some acid, but so little I doubt it would cause damage to other parts, but the caps would go bad
  • caps = capacitors
  • there are a few things you would need: Soldering iron, solder, solder-sucker, not adhesive.

Most of us here are not only fans of classic New England speakers but also hobbyists, and we love fixing things. But as you said; "if it ain't broke don't fix it."

Now, having said that, there is one thing you SHOULD take care of right away. These speakers have foam surrounds: That's the foam rubber ring that attaches the paper cone of the big speaker (woofer) to the metal frame. The foam deteriorates over time. When it is shot the speakers will probably sound awful BUT you may not notice it at first and you "could" damage the speaker itself. I suggest removing the front grilles and inspecting the surrounds. Even if they look OK, you may find that if you touch the surround with your finger it will crumble. These MUST then be replaced.

You can DIY--it's not hard and you can get a very complete kit for 2 speakers for about $25. Otherwise, you will have to remove the woofers and send them to a pro for refoaming.

Let s know what you find.

Kent

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Short answer: Leave them alone and enjoy! :)

Thanks!

Most of us here are not only fans of classic New England speakers but also hobbyists, and we love fixing things. But as you said; "if it ain't broke don't fix it."

Actually, I'm in the same boat, I bought these to learn from them, just not right now. I moved out to the New Mexico desert last week, and right now, money is tight. When I have some wiggle room I'd certainly enjoy opening these puppies up again.

Now, having said that, there is one thing you SHOULD take care of right away. These speakers have foam surrounds: That's the foam rubber ring that attaches the paper cone of the big speaker (woofer) to the metal frame. The foam deteriorates over time. When it is shot the speakers will probably sound awful BUT you may not notice it at first and you "could" damage the speaker itself. I suggest removing the front grilles and inspecting the surrounds. Even if they look OK, you may find that if you touch the surround with your finger it will crumble. These MUST then be replaced.

Yup, that was the first thing I did! I could only afford these speakers because the foams were completely gone. I didn't find out about my little Frequency switch oddity until I had already replaced the foam surrounds.

Thank you so much for your help! I'll be lurking these forums and reading about speakers, and I'll be sure to post again when I'm ready to do some more work on them, or if I get ahold of any other vintage gear. Once I get an income stream nailed down, I think my next obvious step is to buy a better stereo that will really bring out the quality of these NLAs. That will be a whole new thread!

Till then.

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Yup, that was the first thing I did! I could only afford these speakers because the foams were completely gone. I didn't find out about my little Frequency switch oddity until I had already replaced the foam surrounds.

OH! So you're a pro. Sorry for wording my response in such simplistic terms "("the big speaker [woofer])"

Enjoy!

Kent

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Congratulations on your New Advents! Enjoy them!

Hehe. I had to replace the surrounds on all 10 of my original Advent big speakers (woofers). :D

Some because they were bad and some because the previous owner had used thick and stiff ones with little rolls on them.

Doug

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I'm not familiar with electrician work, and while I'm sure I could handle it, I'm cautious about opening them up and making a mistake during the repair, when they already sound better than any speakers I've ever owned. I'm quite satisfied with the way they sound now, I wouldn't derive any satisfaction from knowing they have newer parts if it doesn't improve the sound quality. If they don't "sound broke", should I be fixing them? I'm tentative because money is a huge factor in my life right now, and if I damage these speakers trying to fix a problem that I don't even notice, I won't be able to replace them. This is the first time I've owned nice speakers in my life and I'm loving every second of them.

I'm not rejecting your suggestions, I'm just curious. Thank you both for your expertise! I'm learning a lot.

There is a very good reason to replace the caps, they are electrolytics and they do not age well, usually good for 10 to 20 years. If they fail and leak DC current or low frequencies then you could blow a tweeter and that will be an expensive repair. So, I suggest that you go easy on them and do not play them real loud, then when you have the time and money change the caps and any bad resistors while you are in there. I can suggest some very low cost caps that will work just fine. I do also understand if you are not comfortable working on them.

This cap:

https://www.madisound.com/store/product_info.php?products_id=960

in parallel with this one:

https://www.madisound.com/store/product_info.php?products_id=1463

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