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Bit of help with OLA crossovers and stuffing


kehern15

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Hello all!

I am a new member here, restoring some OLA. I have already refoamed the woofers, and am now going to replace the capacitor and resistors, as well as the foam with fiberglass. I have two questions though:

1. How exactly do I remove the old capacitors, and wire in the new ones? It seems easiest to clip the old capacitor out, and solder the new ones in to the old leads, as the old leads are soldering in two or three different junctions. Is that the best way, or should I solder speaker wire to the old connections, and then solder the capacitors to them a bit further away?

2. When I was removing the old foam, I noticed burn marks on the foam from where the crossover had heated up and charred the foam. I am guessing this isn't good both for safety, or the performance of the crossover. When I restuff the cabinet with fiberglass, should I cut out a hole for the crossover to have air? Or will fiberglass be ok laying directly on top of the crossover?

Thank you!

-Keher

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Hello k-15, and welcome to CSP here with your first post. As I'm sure you well know, the earliest Advent models are considered to be very fine simply constructed loudspeakers that offered a big bang for the buck when originally marketed, and to this day are still very solid performers and deliver a terrific value in their 40 year-old state after re-conditioning.

Not the OLA model, but I have two pairs of Smaller Advents: 1972 version with green tweeters and fiberglass stuffing; and a 1975 pair with red tweeters and foam insulation. Mine have not shown any signs of burn marks from overheating, but it is probably a good idea to heed this observation and take precautions when re-building. By no means should you cut any extraneous hole in the cabinets to allow air to pass - - the speaker performance is fully dependent on having a nearly air-tight cabinet.

Regarding soldering, there are several methods to accomplish these connections, but you will almost always get far better responses by posting pictures of your particular situation, which can then be addressed explicitly. Experienced voices will chime in on most anything shown, including but not limited to, the items you have already mentioned.

The composition of this particular type of foam stuffing is a mystery to me, but nonetheless, visible burn marks are never a good sign. Fiberglass is typically a fully fire-resistive material, and if you decide to replace the foam with FG, you should first determine the weight of fiberglass originally stuffed into the cabinets of the OLA.

I am sure you will get more advice fairly soon, and again, welcome.

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Yes, I read much about the OLAs before purchasing, they seemed to be perfect for me, and I do quite love them!

I should have clarified; I meant a hole in the fiberglass, so that the crossover isn't covered by the fiberglass. I fully understand the importance of a sealed cabinet, as these are acoustic suspension speakers, I used mortite around the woofer when I refoamed the woofers, to reseal them. As far as I know, the foam blocks are the factory stuffing. Attached is a picture of the few pieces that have burn marks on it. From what I understand, I need aprox 2lbs of fiberglass in each speaker, I intent to purchase it soon!

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Attached is also a picture of the crossover, sorry for the crappy second photo, but they are made the same. I was just wondering how people generally replace the capacitors and resistors; simply clip the old one out near the body of the item, leaving the soldered leads in tact, and solder the new ones in? Or do they complete desolder the crossover and resolder in the new components following the leads of the old parts? (this seems much more complicated, as one has to solder the new parts 2-3 times at various junctions)

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post-174223-0-29875900-1416884587_thumb.

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Either way works for replacing caps. I've done both ways, and it just depends on how microscopic I want to get. The perceived results are always better, the more effort involved :-) The actual results, assuming tight connections, of course, are pretty much equivalent.

I don't see any harm in opening up some space around the crossover. I'd be worried, actually, on finding melted *anything* inside a speaker. It's not that common, but it does happen, often capacitor-related.

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Yeah, I was really surprised to see such burn marks on the foam, especially as it is from the factory, from what I've read. Made me worried that either I or the previous owener(s) pushed the speakers, heating the crossover etc. Hell it could have caught fire or something! (Well depending on if the foam is fire retardant) Was mainly wondering if anybody else has seen something similar?

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Yes, those foam blocks are factory original, but it's a little hard to evaluate the burn marks, and they certainly do not look extreme - - the dark marks almost look to me like the result of oxidizing metal rather than an overheated electrical component. From what I can tell, your first crossover pic is pretty clear and shows no visual signs of obvious failure.

Still, it's not a bad idea to replace these original caps at this point. Early Advent crossover components often varied from batch to batch, and at least yours do not have the black/red caps that have been known to explode. Looks like your x-o has a switch, two inductors, two caps and one resistor? It might be worth checking the wattage on the resistor, and maybe boosting that if it concerns you.

The idea of creating a void in the fiberglass around the x-o is not necessary, IMO, for two reasons: 1.) the material is already non-combustible, and 2.) the insulation is likely to settle over time, thereby coming into contact again, unless you create a shield of some sort. Why not just lay a small swatch of FG over the x-o, and then replace the original foam blocks over that?

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I'm fairly certain that they are burn marks, as the capacitors show no sign of oxidizing.

I'm replacing the electronics as it is an often recommended thing to do, and I intend to keep these speakers for years to come.

From what I've read (on this forum mainly) fiberglass insulation (which these speakers initially were stuffed with before the change for foam) is a better material, and will help the low end a bit.

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Welcome to CSP.

If you search through the Advent threads there is plenty of discussion about the crossovers and the stuffing. Here's one: http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=6623

Also see Pete Basel's page on the OLA. He advocates completely rebuilding the xo if you plan to keep them. http://baselaudiolab.com/ADVENT_LA_XO.html

Most restorers recommend ditching the foam blocks and stuffing with fiberglass.

-Kent

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Welcome to CSP.

If you search through the Advent threads there is plenty of discussion about the crossovers and the stuffing. Here's one: http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=6623

Also see Pete Basel's page on the OLA. He advocates completely rebuilding the xo if you plan to keep them. http://baselaudiolab.com/ADVENT_LA_XO.html

Most restorers recommend ditching the foam blocks and stuffing with fiberglass.

-Kent

Yes I have read through nearly every thread involving the OLAs on this website haha. My questions were regarding any concern about the foam and burning, as in when I switch to fiberglass, should I be sure to leave the crossover uncovered? And what is the best way to solder the new capacitors/resistor, as I stated previously.

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Yes I have read through nearly every thread involving the OLAs on this website haha. My questions were regarding any concern about the foam and burning, as in when I switch to fiberglass, should I be sure to leave the crossover uncovered? And what is the best way to solder the new capacitors/resistor, as I stated previously.

OK. Stuff them with fg. Don't worry about it touching the xo. Attach the components whatever way works best for you--either desolder the old components or just snip the leads and solder to those. Of course be sure no bare leads touch each other.

-Kent

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Don't worry about the burn marks. They just mean the PO ran the speakers a little too hard. They won't hurt anything now.

There has been debate about whether fiberglass is better than foam but it doesn't really matter. I have both and the speakers sound the same. In fact, some recent opinion is that the foam is actually a little more effective in making the cabinet appear bigger to the woofer.

I would just reuse the foam. It's original.

The easiest way to install new capacitors is to clip the leads right next to the old ones, bend "hooks" into the new leads and the old ones and hook/crimp them together and solder. It's as good as anything else.

The only reason to completely remove the old components and rebuild like original is if you want to maintain original appearance.

Doug

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I would replace the resistors. Resistors turn energy into heat, hence the scorching. The OLAs have 5w resistors which are IMHO inadequate. I've seen burned or cracked 5w resistors in KLH Model Five and Model Twelve systems. I always replace 5w resistors with 10w. Not everyone agrees and I'm not an engineer but 10w wirewound resistors cost about 50 cents each so it's cheap insurance and/or peace of mind.

Also consider bracing. Cheap and easy. It's mentioned in the thread I linked to, and Carl has spoken of the benefits of bracing the OLA.

If you want to go all-out you might want to replace the inductors but that runs into a bit of money. Pete advocated replacing the iron core inductors with air core. You can see the physical differences in the attached photo, with original inductors on the bottom and new air-cores on top.

In my rebuild I replaced everything: Caps, inductors and resistor. Was it worth it? To my ears the OLA still did not sound as good as the AR-2ax. YMMV ;)

Kent

post-101828-0-27541900-1417297350_thumb.

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After looking at the photos of the foam, I really think the "burn marks' are just from reactions of components with the sulpher in the foam. I have seen it many times. Woofers from foam-filled cabinets can be severely oxidized where the metal rests against the foam and wire insulation resting against the foam will lose some of their dye to the foam. Same with the vinyl covering on capacitors.

This doesn't happen in the fiber glass versions. Woofers from them pretty much stay new looking.

Sulpher is very corrosive and typical foam does contain it.

Doug

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Thanks for all the replies guys, it helped a lot.

I have recapped and reresisted (is that a word?) one speaker, picture attached. Used Audyn caps, and just clipped the old capacitor and resistor near the body, twisted the leads together, and soldered them. Was pretty easy. I tested one (before I put the woofer back in) and it seemed alright!

Oddly enough, the resistors were different brands in the speakers, even though the serial numbers are sequential.

Thanks for the info Doug, I was just worried that the crossover wasn't able to dissipate heat well enough, good to know that that wasn't the problem.

When it comes to restuffing the speaker with fiberglass, do I just lay down three bats? I understand that I need 10ft of R13, which seems like a tight fit. Or is it better to first stuff the upper/tweeter half of the speaker with as much as I can, and then leave a bit of room around the woofer? (I will also be putting a layer of cheesecloth between the woofer and fiberglass, to help prevent any fiberglass particles from getting into the woofer cone/spider)

Picture of recapped crossovers! Does it all look alright to you guys? Both drivers on both speakers worked fine, so I'm guessing that all went well.

post-174223-0-31519800-1417466300_thumb.

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Your pic is pretty good, but it's difficult to see all of the new connections. Still, the work looks quite good from what I can see. It's not always easy working on these Advent crossovers - - - they are often such a gloppy mess of hot melt shmoo. After looking at my Advents with foam stuffing and seeing similar small dark markings, I remain convinced that yours are not burn marks but nonetheless, I think it is prudent to use the 10 watt resistors as you have done per the suggestions in posts 6 and 12.

On the FG stuffing, I had always thought that this quantity was measured by weight (ounces), rather than by length (feet) or thermal resistance value (R13). Construction grade FG insulation will work just fine, but because there are several variables such as framing depth (2x4 or 2x6) and stud spacing (16" o.c or 24" o.c.) when purchasing these products, it's probably better to just follow the weight parameter which you noted in post 3.

Far be it for me to question a very successful Henry Kloss design, but am I the only one who thinks that the internal wiring in these early Advent speakers seems particularly light weight?

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Thanks, I can post a closer/more clear picture if you and others would like to see it more clearly.

Ah yes, it is aprox 1lb/cubic foot I believe. I bought a roll of R13, 3.5inches thick, and 15inches wide, and in this thread (http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=2895) I believe it was determined to be aprox 10'5" per cabinet, as measured and converted etc. Rereading the thread though, they seem to be for the NLA, though if I remember correctly, they are the same weight, and thus the same amount of fiberglass is needed.

I was also quite surprised by the lightweight wiring...do you think there would be a benefit to upgrade it? I also bought some 16awg acoustic research speaker wire I could use (sticking with Kloss companies heh)

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Sounds to me like you've got a well-considered scheme for the insulation quantity.

Re: internal wire, there are many owners who habitually increase wire gauge and sometimes replace unnecessary x-o components as well; and then there is the other camp which claims that larger gauge wire will make no audible difference and in general, if it ain't broke, don't fix it. My own skills are in no way sufficient to adequately analyze and measure all of these variables, but I am of two minds about the wiring. Realizing that Kloss' main objective with these early Advents was to produce the best-performing speakers at the lowest-possible price points, I have to think that if an enhanced performance had resulted from a few pennies worth of thicker wiring, this decision would have been implemented and we'd be looking at slightly larger gauge wire.

Having said that, relative to similarly sized speakers this wire looks entirely too skimpy, but it's really hard to argue with the finished sound output. The OLA and Smaller Advent continue to impress me with regards to performance, but I have very rarely been impressed with any part of the build quality of these products, and as far as I can surmise, my observations would have met Kloss' original objectives just as he intended.

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  • 2 weeks later...

I would replace the resistors. Resistors turn energy into heat, hence the scorching. The OLAs have 5w resistors which are IMHO inadequate. I've seen burned or cracked 5w resistors in KLH Model Five and Model Twelve systems. I always replace 5w resistors with 10w. Not everyone agrees and I'm not an engineer but 10w wirewound resistors cost about 50 cents each so it's cheap insurance and/or peace of mind.

Also consider bracing. Cheap and easy. It's mentioned in the thread I linked to, and Carl has spoken of the benefits of bracing the OLA.

If you want to go all-out you might want to replace the inductors but that runs into a bit of money. Pete advocated replacing the iron core inductors with air core. You can see the physical differences in the attached photo, with original inductors on the bottom and new air-cores on top.

In my rebuild I replaced everything: Caps, inductors and resistor. Was it worth it? To my ears the OLA still did not sound as good as the AR-2ax. YMMV ;)

Kent

I do not generally advocate replacing the inductors in the Large Advent. I seem to recall

saying that if they are your main system, you want to throw money at them (on boutique

caps for example), and you drive them hard then you'd be better off spending the money

on air core inductors.

I do not usually suggested replacing resistors but if they have been stressed then it is

certainly best to do so.

BSC is the best way to improve the Large Advents.

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BSC is the best way to improve the Large Advents.

Send Pete a PM if you want to try the BSC, He'll probably send you a loaner and if you agree it improves the speakers it's easy to build one. I built one in a little project box and have it in the EPL loop of my system. For most music I don't believe it improves the AR-3a's but for some recordings there is a definite improvement.

-Kent

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Baffle Step Compensator

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=2692

This is an old thread, so the posts are somewhat out of order (due to server changes) and it's long: 142 posts. See post #110 by Gary Wong for a photo of the innerds, #103 for parts list, #135 for schematic, a labeled photo on #140.

Contact Pete. He's very helpful.

-Kent

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