Noobie: Powering Small Advents

[Guest Wayne]

Hi all,

This seems like the place to find out about vintage Advents so here goes. I picked up a clean and refoamed pair of Small Advents and need to power them. They will be used mostly for low and medium level listening. I play a variety of rock, jazz and classical. No hip-hop.

I've been mostly looking at vintage receivers... silver Pioneers, 1970's Marantz, etc.. I have a couple of questions...

What is a realistic the minimum power that I should have to get the best out of the SA's- would a 2215 or something like that power them sufficiently?

How do the early vs late 70's Marantz and Pioneers compare in terms of sonics? I see quite a few who prefer the early 70's versions of each.

How do these sound compared to newer gear, such as the NAD's from the 80's and 90's?

One final question... is there value to re-capping the SA's?

Thanks for your replies.

[Guest JonM]

Wayne -

I would make sure two things, both intended to protect the tweeters - make sure you have enough power (so you don't clip the amp and damage the tweeters), and make sure you have a fuse in series with the speakers (again to protect the tweeter).

How much power do Smaller Advents need? That depends on two key things - how big is your listening room, and how loud do you listen? A 2215 might actually be enough, if you listen at reasonable levels in a smallish room. More power won't hurt, as long as you follow my second recommendation (fuses).

As for fuses, I use (some will scoff) 1 amp fast blow fuses, and I have for 35 years (with many different speakers, including AR-3a's, stacked Advents, and smaller Advents, too). The *only* time I have blown a fuse was when the lights went out, and came back on again. The turn-on pulse from my preamp was amplified by my power amp and popped the fuses. No damage to my speakers. This was in 1976. I have never blown a fuse playing music.

Of course, what this means is that I don't listen very loud (even in an 800 sq ft room with cathedral ceilings, 1 amp is enough for how I listen!). You may need a bigger fuse, but I wouldn't go over 2 amps (very roughly, P=I^2*R, and the SA's "R" is 4 ohms, so a 2 amp fuse means Power = 2^2*4 = 16 watts continuous, which will go very loud).

And finally, as for recapping, that is also important to protect the tweeters, because the caps keep the large low frequency signals out of the tweeter's fragile voice coil. The original electrolytics in those Advents are probably well out of spec by now - the electrolytic inside has had over 30 years to gradually dry out, and as they dry out, I have read that electrolytic caps tend to increase in value, allowing more low frequency signal to pass through. Putting in new caps addresses this issue. (I am not sure I understand the physics of that - I would have thought caps would deteriorate to become more of an open circuit than a short circuit. Regardless, better safe than sorry.)

I recapped my SA's (15 years ago) with Solens, but there are other brands that are well regarded and less expensive. (I just ordered some Dayton polypropylene capacitors from Parts Express for my larger Advents, after reading various comments on the web about alternatives. Apparently Dayton caps are OEMed by Bennic, who is well regarded, and they are very affordable.) Regardless of brand, I would 1) use a metalized polypropylene cap from a respected manufacturer, and 2) use a cap whose mfd value is as close to what's marked on the original as I can get.

Also, polypropylene caps last virtually forever. You could use a new non-polarized electrolytic (like what Advent used originally), but then in 20 years you'd be replacing it again and who needs that bother :-)

Have fun - the SA is a nice speaker.

JonM

[Guest Wayne]

Jon,

Thanks for your articulate and well considered reply. I am not interested in head banging levels - mostly these will be played for background and moderate level listening. As a result I think I'll pass on the inline fuse. I can't recall ever blowing a speaker in over 30 years of this hobby. However, the recapping is something I will do once I hook them up and decide they are keepers. Who knew that the drifting in their values could lead to damaging the tweeters - this is an interesting bit of information. Thanks for the advice to go with polypropylene caps - I didn't know they would outlast other types. Given the modest investment in these speakers I'm not interested in 'designer grade' caps. No need to cheap out, but a solid upper middle of the road is all they will need. When time permits I'll check the forums to see the cap values that I'll need and have someone who does this sort of thing pop them in... I've never taken a speaker apart before and am not sure if I'm up to the task.

As to power, the general advice I received on AudioKarma was to stick with mid-powered receivers of 1970's vintage... 40 watts or so as a reasonable minimum. Because I really don't push speakers and my wife objects to anything over about 85db I think a little less will be OK for my needs. There are some who say certain speakers need at least X watts to come alive; nobody has said that about these. Only that they will play louder with more juice. With that background, I just landed an NAD 7030 receiver on the bay for a decent price and will see how that goes. I believe it is a first generation NAD product. My original intent was a silver Pioneer or Marantz but the black and gold retro look of the NAD and its great advertised condition won me over. Plus, I know those babies were designed to handle any load whereas the Pioneer's and Marantz's did not even quote a 4 ohm spec until the late 70's. When they did quote a spec it nearly the same as its 8 ohm rating. I hope the NAD holds up over time as few of these appear on the used market.

[Guest JonM]

Wayne -

You should enjoy the NAD. Nice match for the Advent in terms of power level and sound (smooth!). (I had a 3020 many years ago and really liked it.)

Changing the caps is not a big deal if you are comfortable with a soldering iron. If you're not, then by all means have someone who is do it for you.

As for the fuse, your call. Most people live just fine for decades without them. I just know getting replacement tweeters is a pain and an expense, so I prefer to play it safe.

Enjoy!

JonM

[Guest JonM]

Wayne -

I've been doing more reading about how electrolytic capacitors age, and apparently what I said earlier was incorrect (my intuition was right :-)

As electrolytic caps age, their C values tend to decrease, which in high pass circuits, like an Advent crossover, will raise the crossover frequency (not lower it). So replacing an old cap that has drifted with a new one of the original value may raise the level of the midrange around the crossover frequency (because you are lowering the tweeter's crossover frequency back where it was originally).

I recently replaced the caps in my 35 year old large Advents with Dayton polypropylene's and was pleased with how much smoother the midrange seemed. I confess I didn't do any formal blind A/B comparisons, just casual listening before I started the project and after, so it could have been my imagination. But I know those caps won't need to be replaced for the rest of my life. And the sound is quite good, especially considering how much less expensive the Daytons are compared to some brands.

(All that being said, recapping speakers still seems somewhat controversial. I have read that what kills electrolytics is heat - as in a tube amplifier - and even then, many old electrolytics, even in tube amps, are still fine decades after they were new. I don't have a capacitor tester - I would love to have checked the capacitors I pulled out of my Advents to see if any of them had actually changed. I have a pair of AR 10pi's - which I absolutely love - that I plan to recap when the mood strikes me. But I must say, they sound so good with their original caps that I hesitate to plug in my soldering iron :-)

JonM