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EricWww

Questions on OLA (stacking and fried tweeter change)

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Hello, I have two questions about the LAs:

1) For the OLA (originally my dad's, I blew up the tweets as a kid 20+ years ago and now decided to restore them), I replaced some '73 tweeters with "later" versions- I read about how the tape does not go all the way across on the "newer" versions as seen in the pic below. But I also notice the positive terminal is now reversed. Was this an actual change in production?

The right pic is one from Audio Karma, looks like a "newer" tweeter with the partial tape and brown glue- and it looks as though the polarity marker was scratched out, which makes me wonder if someone screwed up the polarity markings on my new tweeters. 

I plan to check the true polarity by playing some polarity pulses and then visually watching the wave form using a computer based RTA/analyzer program. 

5a973b49aac5c_tweetercomparison.JPG.db6d9f1181ee19509a984d6716334491.JPG5a973ed2dd90f_audiokarmatweet.jpg.6d23dd87c33b952041ff5987412b82e5.jpg

2) I've read quite a bit on the Advent stack, including the Absolute Sound article. My question  is- what is it about the Advents that make them stack "so well", besides the physical sizes? I haven't tried the stack yet but seems to me another pair put upside down over one pair without any sort of crossover or tweeter adjustment will result in some serious lobing, kind of a fake D'Appolito design with an extra tweeter and midranges too far apart. Does it have to do with the relatively low frequencies the tweeters play? Has anyone done any frequency response analysis on such a set up? 

In my search for a second set- I wound up buying a pair of NLAs but haven't fully directly compared the NLAs with the OLAs yet (waiting for another woofer to come in on the OLA, and new caps). I have not tried the stack just yet - as I have not come across another local pair of OLAs or NLAs. 

 

Thanks,

Eric

 

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The markings on the tweeters are factory. I have seen crossed out ones too and, as a matter of fact, I believe at least one of mine is like that. Anyway, the "X" marks the positive terminal although doing your method of checking would be interesting.

I believe the inconsistency of which terminal is positive is probably from the windings being so small and the assembler probably running the wrong end of the winding to a given terminal. Go by the mark or, if your testing contradicts the mark, by that.

The gray glue tweeter is a fairly early one. The brown glue was later and went to the end of production of the original Advent in 1977 or 1978.

I don't have my stacks as per convention on forums. I run both speakers right-side-up. I thought there seemed to be more interference between the two tweeters when they were close together. With them farther apart, there seems to be more "air" or spaciousness. I know some will say that's actually a symptom of comb effects but I think it sounds better.

Doug

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Hi Eric,

From my memory the sound ‘signature’ of the OLA and NLA is so similar I would consider them the same. Given that, as soon as both pairs are working, stack ‘em! 

Other’s would have to comment on the theory, but I can relate that I said ‘wow’ when I first stacked mine. I use a stack as the R & L for home theater/rock and roll system. 

 

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Back in 2008 I had a vintage stacked double New Large Advent system with a Harman Kardon Citation 11 preamp and two Phase Linear 400 power amps (one 200 watt channel for each speaker). The New Large Advent had a different tweeter/woofer configuration as well as different tweeters and woofers. With Pete's BSC circuit and staying in the sweet spot they were impeccable. But it was all a bit massive and I got rid of it all for a modern system of Emotiva gear and Magnestand modified Magnepan MMG speakers.

 

formerly jackfish, can't remember my password

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Jackfish,

Great to hear from you again. As I recall, the Magnestands ticked off pretty much everything for you except the big slam (dynamics) and the low end which you filled in with a sub. It must be quite the satisfying system if you've kept it this long. Or you just got tired of the audio merry-go-round.

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