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Advice on New Large Advent

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I previously rebuilt my New Large Advents about 25 years ago and I want to update the crossovers with better capacitors. I recall that they had one or two sheets of foam inside. What be the best material to fill them with? Leave the foam, replace the foam with poly fill, etc? Also my recollection is that the inductor is an air core. Assuming that, I suppose that it makes no sense to replace it. I notice that Parts Express has an air core inductor that has identical in  L and R. Thanks.

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The OLA had fiberglass filling the cabinet. Sometime during the NLA era Advent went to open cell foam. I prefer fiberglass, as do many others. I would leave the foam instead of using polyfill.

For the definitive source of Advent crossover information, check out Pete B's page at http://baselaudiolab.com/ADVENT_LA_XO.html The page does not specifically say that the inductor is an iron core, but the pictures shows it could be. I recently got rid of my NLA, so I cannot look. If you can get an equivalent inductor and you want to spend the money, do it. 

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RTally is right.  Pete B is the man for Advents and has many posts here and at Audiokarma in addition to the link in RTally's post.  The inductor is steel core.  Summary of things I learned from reading Pete's posts:  The original inductor is ok but if you have the cash go for the air core particularly if it's part of you main system;  if you go to metalized film caps to upgrade add a .4 ohm resistor rated at 10 watts in series to account for the lower ESR of the metal caps.  If you put new surrounds on find suggestions here or on Audiokarma for the best ones available.  My personal experience is the metal caps give a slightly nicer sound and my preference is replacing the foam with fiberglass.  Just trying to save you a little time searching the forums.  It can take a while to get through all the stuff out there.

Edited by Guido57
correction

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9 hours ago, RTally said:

The OLA had fiberglass filling the cabinet.

Not all. Mine had foam. I restored them following Pete's guidance, using film caps and new, heavier, air core inductors.

Replaced the foam blocks with fiberglass. Sorry I don't have a record of how much fiberglass.

-Kent

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The change from fiberglass to foam happened in the latter days of original Advent production, in about 1975. I have some of each and they sound the same. I doubt, in spite of possibly a production cost reduction, Advent would have made the change if there were a audible difference between the two versions.

Doug

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An alternative to going air core if you're cost sensitive are p-core inductors, which have significantly less distortion than iron core inductors and lower DCR and cost at a given wire gauge than air core inductors.

I unwound four of these down to 1.6mH for my main two sets, and will likely be adding two more:  https://www.parts-express.com/jantzen-5280-22mh-20-awg-p-core-inductor--255-130

This is also a lower-than-stock DCR, which I ~think~ has added to the damping of the woofer, to my ear.  All-around improvement.

Fiberglass insulation or poly fill for cabinet fill, don't be too stingy on the amount.

Pick some poly caps on-spec.

Replace the resistors with non-inductive ones, if you feel so inclined, but these are likely the least important.

If you have the super-thin-wired tweeter inductors and plan on pushing them loud, it would be worthwhile to replace these with lower-gauge (thicker) inductors.

Edit - mine are Original Large Advents / OLAs, so there would be some component value differences between ours and yours, the NLAs, I don't think had dinky tweeter inductors.

Edited by ajfink
Correcting terminology, fixing model.

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The NLA's inductor is only a .3mH, so they're not too pricey even for air-core: http://www.erseaudio.com/Products/XQCoils14Gauge/EAV73-14-300#recommendations plus others available through Parts-express;  though the large inductor for the OLA at 1.6mH is much more expensive for the air core.  I will probably use ajfink's advice on my pair of OLA's.  By the way,  how are people securing new grill cloths to their Advents?  I know I can get the 1/8" staples online in quantities of 10,000, but I don't have THAT many Advents.

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On 3/3/2019 at 10:29 AM, Guido57 said:

The NLA's inductor is only a .3mH, so they're not too pricey even for air-core: http://www.erseaudio.com/Products/XQCoils14Gauge/EAV73-14-300#recommendations plus others available through Parts-express;  though the large inductor for the OLA at 1.6mH is much more expensive for the air core.  I will probably use ajfink's advice on my pair of OLA's.  By the way,  how are people securing new grill cloths to their Advents?  I know I can get the 1/8" staples online in quantities of 10,000, but I don't have THAT many Advents.

Is that the smallest quantity you can find?  Lowe's/Home Depot/your local hardware store might be able to hook you up.

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Thanks to everyone for your comments. I'm certain the inductor is air core at this point, but I think what I'm going to do is make a new crossover. I'm going to get a new plate for the terminals using banana jacks. Since the only switch position I use is "Normal",  I only need an inductor, two caps in parallel to get 13uf, and a 1.5 ohm resistor ( 1.0 plus .5 to allow for the lower ESR of the polypropylene capacitor). I have four speakers so I'll still have a stock pair, although I recapped the crossovers in the early 1990s with mylar caps ( the best I could find at that time).  I bought these in 1978 and they are nicer than new since I finished the wood with low gloss Formbys.

I always thought of the "Extended" position as a sort of a "showroom"  position to make them sound as loud and bright as possible. I can hear the harshness of the upper end of the woofer since the inductor is shorted out. Way too bright and harsh in the lower treble.

Again, thanks.

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Correct me if I'm wrong:  you have a set of OLAs and a set of NLAs?

If so, the "extended" position of the OLAs is akin to the "normal" position of the NLAs and you'd want to match them in that way when playing together, I'd think (but of course you don't have to).

If both sets are the same model...nevermind.

New binding posts is a definite step up.

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2 hours ago, rwh said:

. I'm certain the inductor is air core at this point

 

None of the Large Advents, or pictures or pictures of the crossovers I've seen, has had an air core inductor as standard.  Did you replace the original on your first rebuild?

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Guido57, I got curious and took the woofer out of one. It is an air core and that is what I seemed to remember. It looks like a magnetic core inductor at first glance, but the center is hollow. The wire seems to be about 20 gauge. I have four New Large Advents I purchased new in 1978. I replaced the capacitors in them in the early 1990s when I took the woofers out to be refoamed. If you look at Pete Basel's photos in his article on the crossovers, you will see that the inductor in his picture looks like mine. I took a couple of pics with a screwdriver through the center of the bobbin and will attach them. At this point, I'm using the original inductor when I rebuild them.

Well, I can't attach the the pics. I get an error message " There was a problem processing the uploaded file. -200 ". Whatever that means.

 

 

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RickB, Thanks!  That worked. Anyway, here is my  NLA crossover, original except mylar caps replace original NPE.

IMG_1866new.jpg

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I wouldn't muck with them, then, unless you'd like to move to a lower DCR for further damping/cutting bass "boominess."

 

Edit - I would remove the screwdriver, first.  😋

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My bad.  They didn't look like the air cores I see in the catalogs so I ASSumed they weren't.  Never thought to stick something trough them.

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