better tweeters for Dynaco a25s?

the weakest link we love so much

"more dynamic, transparent & more detail" is N

Postby meshuggeneh » Tue Nov 01, 2011 11:31 am

cheap-Jack wrote:Hi.
snitch56 wrote:...Will replacing the electrolytic capacitor with film alter the sound any from the original design?


Good question!
Yes, it will sound better - more dynamic, transparent & more detail. The tonal signatures of the loudspeaker will be not "alter" PROVIDED you do NOT replace the stock inductors there.


'(n)'

You are making statements backed by hearsay, conjecture and folklore - not by hard evidence! You CAN'T POSSIBLY know that his results will be "better - more dynamic, transparent & more detail"! Unless you were - like me - born in the early 50's or before, it is highly unlikely you have ever heard dynacos as new-out-of-the-box products, performing as their designers intended. If you are 40 or younger, the first dynaco A-25's you heard were already "vintage" speakers, with all that implies.

Secondly, your advice to "NOT replace the stock inductors there" betrays that you have never seen the inside of a dynaco A-25. If you had, you would know that the crossover in an A-25 consists solely of a single cap... NO inductors are present whatsoever.

Thirdly, your statement "The tonal signatures of the loudspeaker will be not "alter" (sic) PROVIDED you do NOT replace the stock inductors there" is again, based on flimsy and erroneous assumptions! Every cap exhibits non-capacitive characteristics. Some more so than others. One such characteristic is ESR, or "Effective Series Resistance." Replace the tired old A-25 electrolytics (which when new exhibited their own ESR which, as they aged, increased) with nice shiny new polys, which generally exhibit less ESR than electrolytics, the end result will nearly for certain be a hotter upper midrange and treble, because the tweeter will be louder than before, due to less tweeter attenuation from capacitor ESR. The octave-to-octave musical balance - or the "tonal signature" as you put it - WILL be altered. Depending on the degree of deterioration present in the old caps, as well as your choice of new caps, the difference will be anywhere from "subtle" to "not much" to "quite significant." The end result will certainly be a hotter top end than the current box. And possibly - even likely - a hotter top end than that A-25 had when it first left the factory in Denmark some 40 years ago.

Fourthly, you characterize "more dynamic, transparent & more detail" as "better." Your choice of adjectives are just vague code words for hotter upper midrange and/or top end. People may LIKE speakers that are "more dynamic, transparent" and exhibit "more detail," but that doesn't make them "better." Almost always, these characteristics are COLORATION! Extra "detail" can almost always be traced to a rising characteristic starting somewhere about 12 kHz. People can decide for themselves if they "like" this, but it represents a departure from accuracy in reproduction. And coloration is NOT what the dynaco A-25 was about. Read the reviews from the period as well as dyna's sales literature from the period and you will catch my meaning.

If I listen to a recording of a symphony orchestra (I use acoustic instruments for my illustration. With digitally produced and manipulated sonics on Pop, Hip-Hop and R&B releases these days, all bets are off.) and it is "more dynamic, transparent" and exhibits "more detail," I get to decide whether I "like" it or not - that is a matter of opinion - MY opinion. But whether it sounds more or less like a symphony orchestra is NOT a matter of opinion - mine or anyone else's! MOST of the time, it means that it sounds LESS like a real symphony orchestra in a real concert hall. And in my book, that does not make it "better." It makes it "different" and in my opinion, by definition WORSE!

Re-capping always gets you a "different" loudspeaker, but don't be fooled into thinking it always gets you a "better" one.

':/'
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Postby wiredbecker » Tue Nov 01, 2011 12:49 pm

Howdy fellas,

I did some work with my late friend Zilch back in April of 2008 where we compared the frequency response of the A25 to the later, supposedly more improved A25XL. Here is what we found:

http://www.audiokarma.org/forums/showth ... p?t=162000

After measurement I sold my A25XL's and kept my A25's which I continue to listen to regularly.

Zilch and I had been planning to break out the Sawzall and install waveguides and compression drivers as an upgrade for the A25 in an attempt to iron out some of the +/- 5db valleys but what we found was that the A25 was very acceptable in its stock form! The A25 ended up on Zilch's short list of excellent vintage bookshelf speakers.

I'm not saying that we shouldn't keep looking for an upgrade path for these speakers... I'm just saying one could be very happy if this is the only speaker they have for their modest music needs. If I were you I'd pursue the creation of a mirror imaged pair to facilitate on axis listening from both left and right channels within the sweet spot. ;)

RIP Zilch!
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Postby Quad » Tue Nov 08, 2011 5:36 am

Dynaco logo/badges - Kevin of DynakitParts has them -
cheapest source I could find.

http://www.dynakitparts.com/store/product.aspx?id=322
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