better tweeters for Dynaco a25s?

[nyazzip]

so i have put a lot of time into prepping my a25s to look nice...they are yet to be finished but i did re-grill them. i realized(tonight) that treble seems maybe a bit supressed. without goung nuts, does anyone suggest replacing the stock tweeters? it is highly possible my ears are going too; i know my left one is screwed
just wondering if there are any reasonably priced replacements that might be a bit brighter. i wouldn't pump much money into these, but, i do really enjoy them
they give my $600+ Klipsch rf-52s a run for the money, especially with "airy" jazz and '50s-'60s muzaky stuff(and yes i do enjoy that!)

[Geek]

These sound phenomenal for the price:
http://creativesound.ca/details.php?model=ERT26

(US customers get them shipped from a US address - no hassles)

Cheers!

[battradio]

They look similar to these ,

http://www.parts-express.com/pe/showdet ... r=264-1028

Only you would have to change the crossover cap for this one and not for the one Geek sugested .

I bought 8 of the Vifa 6 ohm version when M&k went belly up for a dollar each ,

Nice tweeters

[Geek]

They look similar to these....

I can proudly say beyond reasonable doubt, they were designed by CSS from scratch
(the link I posted)

Cheers!

[Quad]

The normally suggested replacements for the tweeter are the
Seas Sonotex fabric dome, the 27TFFC (H881)
or the Morel MDT20.
MST-20.5 in the link below is apparently the same as a MDT-20

http://www.renaudio.com/rawdrivers/tweeters.htm

I found this mod below on another forum. Haven't tried it myself.

Remove the grille and remove the metal screen that covers the tweeter. Buy some rubber weather stripping, 1/2" wide, and glue it in a circle around the outside of the tweeter dome. This prevents diffractions from the cabinet, (not to mention the original screen) and improves the imaging.

It would be good to replace the old Jensen bipolar 'lytic
in the crossover with a newer film cap.

A couple of suitable choices -

Parts Express part number 027-554 - Solen 5.1uF

http://www.parts-express.com/pe/showdet ... er=027-554

I have the Dayton 5.1uf in my A25s and am very satisfied
with them.

http://www.parts-express.com/pe/showdet ... er=027-423

[nyazzip]

i did try removing the tweeter screens awhile back, and i didn't notice anything. i put them back because my spidey-sense told me the tweeters were gonna get damaged if left exposed...
i used vintage-marshall "salt-n-pepper" style fabric on the grill frames, which is probably not the most acoustically transparent stuff to use. i inserted neodymium magnets in the grill frames, which will align with black screws i sunk into the cabinet faces, for easy on-off access.
the crossover caps i updated last year, solens i think.
i rounded off the cab corners with a router, and this week i am sanding/priming/painting the cabs black(1st time in over a year that that we have a stretch of weather acceptable for painting). so they should kinda resemble little marshall cabinets. i'll get some pics up when finished.
good to see there are some drop-in replacement tweeters at good prices; i guess with the new grills i can wait a bit to replace them...thanks for the info

[nyazzip]

i ended up removing the tweeter screens, and turning up the treble knob in back 1 click greater than "normal". for some reason i had totally forgotten about that feature
word to the wise: those screws that fasten down the screen ALSO have another very important function, that is, they fix the voice coil/cone assembly to the motor/magnet assembly! i learned the hard way when i heard a loud thud after putting everything together
luckily nothing seemed damaged
currently listening to "mambo hits" from the '50s and early '60s, some good cubano playing on this record, but more importantly, impeccible recording

[elbinster]

nyazzip: we have common problems it seems. My A25s are hanging from my ceiling, and I've totally forgotten about the knob in back... Also, shortly after I got them, I decided to clean up the looks of the front, removed the tweeter screens to get some crud out from behind them. Just then I noticed the voice coil hanging there (I also noticed my stress level rising) No problems though A25 + ST35 is a good combo.

[meshuggeneh]

so i have put a lot of time into prepping my a25s to look nice...they are yet to be finished but i did re-grill them. i realized(tonight) that treble seems maybe a bit supressed. without goung nuts, does anyone suggest replacing the stock tweeters? it is highly possible my ears are going too; i know my left one is screwed
just wondering if there are any reasonably priced replacements that might be a bit brighter. i wouldn't pump much money into these, but, i do really enjoy them
they give my $600+ Klipsch rf-52s a run for the money, especially with "airy" jazz and '50s-'60s muzaky stuff(and yes i do enjoy that!)

There is an updated tweeter recommended by the original manufacturer of the dynaco A-25, SEAS. It is the SEAS Prestige 27TDFC (H1189) Textile Dome Tweeter. I know, cloth domes are out of fashion these days, but the best speakers from that era used tweeters whose diaphragms were fashioned from either from some sort of pulp formulation (paper, if you will) or some type of textile material (a.k.a. cloth). The sound of modern tweeters made from metal, plastic or composite materials just doesn't blend well with woofers, midranges and crossovers from that era. The beauty of the new SEAS replacement is that it doesn't really change the character of the A-25 speaker system, but it does offer improved horizontal dispersion of the high frequencies, improving imaging and adding just a touch of extra "airiness" to the upper range without changing the octave-to-octave musical balance (or "voicing," as the late, great Henry Kloss used to say) of the A-25, which - in MY opinion at least - was pretty much spot-on from the start and to this day does not need "improvement." It also offers better power handling (not really an issue IMO; I often drove my original 1969 A-25's to "eviction earning" levels without damage - with my 200 w/ch dynaco Stereo 400 - a real boat anchor of an amp, packing Hoover Dam for a power supply. As long as it's clean, undistorted power, the A-25's could always take as much as you could feed them. In 40 years I've seen few blown dynacos and they were blown by cheap 20-watt receivers.). Better yet, the new tweeters are a perfect drop-in fit, matching screw hole to screw hole. Best of all, they are cheap for a decent quality tweeter, at $42.40 each. Get them at Madisound at the following URL:


http://www.madisoundspeakerstore.com/in ... ile%20Dome


[No, I do not work at nor do I own any financial stake in Madisound. Nor do any of my relatives work at or own any financial stake in Madisound. I just think they are a great "go to" place for the DIY loudspeaker hobbyist; well-informed staff, good service and the deepest reservoir of parts, supplies and help for the DIY speaker builder I have found anywhere. My only stake is that it is damned convenient for me that Madisound is located in Middleton, WI, a suburb of my home city, Madison, WI USA.]



Contemporary reviewers of the original A-25 - back when Nixon was president and dinosaurs still roamed the earth - often commented about how "neutral" the A-25 sounded. In other words, it lacked colorations or undue emphasis of some parts of the musical spectrum over others. It sounds to me like you don't like "neutrality" in a speaker. You want "brightness." That is easy to achieve, but then you won't have a dynaco A-25 any more... at least it won't sound like one. You'll have something that sounds completely different.

If "something different" is really what you want, I suggest putting those A-25's up on eBay or Craigslist and selling them for a good price, which you should be able to get if you have refinished them as nicely as you say. Then, I would take the money and buy something that sounds brighter in the highs. From the same vintage, I might recommend an EPI (a.k.a. Epicure) 90 or 100. These were an excellent bookshelf speaker, sounding exceptionally good with jazz... amazingly detailed highs, especially complementary to cymbals, high hats, brushes, etc. Another one is the JBL L-26 Decade. These sounded a little too forward in the upper midrange for my taste, but jazz musicians I knew at the time snapped these babies up, because they offered much of the same sonic character of the famed JBL L-100 Century for just a little more than half the price. If you love horns and vocals, you'll probably like the L26. And they are very efficient, too... lots of shout for the watt. These are not as common in the marketplace though, so you may have to cough up a bit extra for nice ones.

Also note that neither of these alternatives can match either the low-end extension or the low-end accuracy of the A-25. But isn't that always how it is? Unless you are willing to sell your yacht to get the money for your stereo gear, there are always trade-offs one has to make. The dynaco A-25 is overall the most accurate among these three, but the other two alternatives are still excellent in their own right and deserve consideration if the dynacos just don't quite do it for you.

There is something else you might try... On the back of the speaker cabinet you'll notice the tweeter level control. It is just a 3-position variable resistor placed between the high-pass filter (just a single capacitor in series) and the tweeter. Just run a jumper with alligator clips across this variable resistor to bypass it. MAKE SURE you don't bypass that high-pass filter capacitor though! And make sure you don't SHORT CIRCUIT the two wires going to the tweeter! When you are done, the filter capacitor should still be in series between the speaker binding posts and the tweeter, but the variable resistor is bypassed by a series jumper that effectively takes it out of the circuit. The speaker will sound slightly brighter - about 3 dB - without this resistor in the tweeter circuit. To the average ear, 3 dB is a noticeable but not a huge change. Enough for your taste? No way to know except by trying it and finding out. If you like it this way, solder the jumper wire into place. The beauty of this solution is, if and when you decide to sell the speakers, you can easily restore them to their factory stock configuration by just clipping out each jumper and that variable resistor is back!... for the next owner to bypass if he or she wants to. Another tip: If you end up replacing those tweeters, keep the original ones handy; the next owner may want those factory originals and not having them would lower the speakers' resale value, could even be a deal-breaker for many prospective buyers.

Lastly, you said you "re-grilled" them? With what? Different fabrics are either more or less acoustically transparent. The beige cloth you bought from the neighborhood fabric store may look OK, but it may be muffling your speakers' high end. How to tell if that is a problem? Simple... Just play something you know that has significant high end content. Then pull off the grilles entirely and play the passage again. You should hear NO DIFFERENCE! If you do, you need to rethink your choice of grill cloth. Perhaps your parents' old beige drapes from their living room - while period accurate - was nevertheless not the best possible choice. ('(lol)')

I hope I have helped.

Cheers,
(':$')

[cheap-Jack]

Hi

so i have put a lot of time into prepping my a25s to look nice...they are yet to be finished but i did re-grill them. i realized(tonight) that treble seems maybe a bit supressed. without goung nuts, does anyone suggest replacing the stock tweeters?
.......just wondering if there are any reasonably priced replacements that might be a bit brighter.

Nope, I don't think you NEED to replace the nice sounding SEAS H87 tweeter, 1 1/2" SOFT fabric dome, a sonic jewel dated back 1970s. It helped make the then very popular Dynaco A25 one of the most neutral/natural & accurate sounding loudspeaker systems back then.

I say so because I am still using this SEAS SOFT fabric dome tweeter in my vintage KEF 2-way loudspeakers (cir 1968), replacing its stock T15 dome tweeter made of Melinex polyester film, which rang like hell to my ears. Aweful! I am so happy I have replaced it with the SEAS tweeter (same one used in A25) some 30 years back. It makes my KEF sound so much smoother & more musical. It has brought me endless music enjoyment till todate.

If you find yr ear may have failed you in finding yr A25 lack of treble.
Then just follow the nice advice given by Meshuggeneh above to do some
miner modification in the X'over network board of the A25 to lift up the treble a bit.

Take my advice do NOT try to replace this excellent sounding soft fabric dome tweeter or you will be opening up a huge can of worms.

I love classical vocals like crazy, & collected many LPs of vocal maters like
Pavarotti, Domingo, Maryln Horne, Joan Sutherland, etc etc. This SEAS dome tweeter does its job properly to bring back those masters back to the stage in front of me.

c-J

[snitch56]

It would be good to replace the old Jensen bipolar 'lytic
in the crossover with a newer film cap.

Will replacing the electrolytic capacitor with film alter the sound any from the original design?

[cheap-Jack]

Hi.

...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.

If you got the chance to open up a loudspeaker box of whatever brandname, don't be surprised to find the most compromized part of inside the box can be the X-over network board, in most situation.

IMO, the most sonic important part of a loudspeaker should be the X-over network but it is concealed insdie the cabinet. So by buildig the X'over network cheap, which the consumers will not see, will help save the cost of building the loudspeaker system as the cabinet, for example, is the most costly part of it.

It happened to my KEF 2-way bookshelvers (cir 1970s). I shaked my head when I opened it up & found its X-over network was built so cheap using small non-polar 'lytic caps on a tiny PCB soldered onto skinny copper traces. Those traces were petty fine that I don't believe it was good enough to handle large voice coil current flows. Maybe that was the standard good enough back in 1960s when the amps were not so hi-definition like todays.

So I replaced ALL the crappie caps with over-rated large metallized polypropylene (PP) film caps of the same values, BUT retained its orginal inductors. I know in order to maintain its orginal sonic signature, the stock inductors must be retained. Bear in mind this is to restore the loudspeaker not to rebuild the loudspeaker to deliver different sonic signatures.

Here is the crucial part of the retoration: -
I redesigned the entire PCB copper traces of the new firbreglass PCB by using the virtually entire copper surface as the conductive routes for the drivers voice coil current flows with tinny gaps etched out to provide the inter conductor-trace insulation. Loudspeaker signal is of very low levels (a few volts), so tinny gap will provide the adequate insulation. Bear in mind the copper trace thickness is only 0.035mm standard. Large copper surface area is needed to offset the thinness of the copper trace - for large voice current flows !!!!!!!!

It works for my vintage KEFs, so it should work for yours.

c-J

[Quad]

The original Dynaco crossover is really simple. No inductors.
Dynaco got away with that because of the well
behaved SEAS 25 TV-EW bass/mid-range driver.

I don't see any downside to replacing the capacitor,
and it is probably a required replacement considering
the bipolar 'lytic is more than a few decades old.

World Designs did a A25 inspired design, with an "improved"
crossover.

http://wduk.worldomain.net/acatalog/wd25ahfw1b.html
http://www.world-designs.co.uk/acatalog/wd25ahfw3a.html

[cheap-Jack]

Hi.

The original Dynaco crossover is really simple. No inductors.
Dynaco got away with that because of the well
behaved SEAS 25 TV-EW bass/mid-range driver.

I don't see any downside to replacing the capacitor,
and it is probably a required replacement considering
the bipolar 'lytic is more than a few decades old.

World Designs did a A25 inspired design, with an "improved"
crossover?

Is it a historic beauty - being so down-to-earth simple??? I like it being so ultra simple yet so good sounding. If you still like the sound of yr stock A25, just replace the cap & see how it sounds before you make another move.

My philosophy in audio is always - simpler the better sounding. A25 is a testimonial of simplicity dated back decades!

Don't get the impression that added electroncs will get better sound. In so many cases per my decades' audio experience, more electronic may make it sound worse.

Judge with yr ears & NOT with whatever graphs you read.

c-J

[meshuggeneh]

It would be good to replace the old Jensen bipolar 'lytic
in the crossover with a newer film cap.

Will replacing the electrolytic capacitor with film alter the sound any from the original design?

The short answer is, "Almost certainly yes."

That said... There is a "But..." Several of them, actually...

Contrary to a lot of commonly believed voodoo and hokum, there is nothing inherently evil about electrolytic caps. But the dynaco A-25's, good as they were, were built to a price. Like nearly all manufacturers of anything, SEAS' or Scan-Speak's (Most A-25's were built by SEAS, but some were built by Scan-Speak) bean counters demanded the use of the very cheapest capacitors that their engineers and product guys would consent to using (and still be able to live with themselves). That meant electrolytics that were not "total crap," but not the best, either.

The dynaco A-25 crossover employed electrolytics with a somewhat higher ESR, or "Effective Series Resistance" compared to the modern, high-quality replacement film caps most people these days look to for replacements. Without going into the detailed and arcane technical jibber-jabber, this basically means that with the replacement poly caps of the same value, the tweeter is going to sound louder, altering the octave-to-octave balance - the "voicing" - of the speaker system vis-?-vis the A-25's as they left the factory in Denmark some 4 decades ago. The difference is not huge, but is enough to alter to sonic character of the system as a whole, which is either a good thing or a bad thing, depending on how one felt about the original A-25's when they were new.

But unless you are old - like me (age 60) - you have never heard a factory-fresh dynaco A-25. If you own clean, well-maintained and unmolested ones, the drivers will still be OK, but the voicing of the speakers will have subtly shifted over the past 40+ years. This is because the aforementioned ESR of the crossovers' original capacitors has shifted ever upward over time, lowering the levels of the tweeters.

So, when you replace the aged old caps with sweet new polypropylene caps of the same value, the perceived sonic difference will be even greater, because you are in effect taking a speaker with a duller midrange and top end than intended by its engineers, and turning it into a speaker with a hotter midrange and top end than intended by its original engineers.

If you really want A-25's that could stand up to scrutiny as museum accurate "period pieces," the obvious approach is to replace the leaky old electrolytics with brand new electrolytics with the same electrical characteristics. This might be hard - or even impossible - to do. So you may have to resort to some trial and error experimentation. The aim would be to duplicate not only the capacitance values of the original devices, but the Effective Series Resistance, impedance and mechanical resonance (microphony) properties, too. You might have to resort to playing around with values, including adding some resistance in the form of series resistors in order to duplicate that "neutral" sonic balance that dynaco A-25's were famous - and valued - for in their day.

How does one do this? Well, if you think you are golden-eared enough to recognize perfect "sonic neutrality" when you hear it, I say, "Not a chance." Double-blinded tests have proven again and again that the claims to possession of super powers made by self-appointed Name-Your-Audio-Society "golden ears" NEVER stand up to rigorous scientific scrutiny. The best way - the ONLY way, in my opinion - is to dig up old test reports from 1968-69, when reviews of the then new A-25's were first hitting the street. These old test reports, from periodicals - some still with us, some since defunct, others unrecognizably mutated - like "The Stereophile," "High Fidelity," (defunct) "Stereo Review" (now a weak and puny shadow of its former self as 'Sound+Vision'), "Audio" (defunct) and "Hi-Fi News & Record Review", contained not just reviews and subjective opinion, but solid and complete technical measurements that could be of great value in duplicating the sonic characteristics of the original A-25's when they were the newest, hottest audiophile bargain-of-the-century. Of course, this would require you to get up off your Barcalounger-calloused butt and do some old-fashioned library research (Google won't cut it if what you want is only available on microfiche!). Also, you will need to buy some goodies like calibrated microphones, real-time analyzers, et al., as well as maybe convert that unused study into an anechoic chamber.

But unless you are a dedicated - and well-heeled - enthusiast, the above approach is impractical. Yet, if you just replace the old caps with the so-called "better" modern polys, you might like the result more when you are done, but the speakers you have created in the upgrade process will NOT sound like A-25's did when they were new. They will - FOR SURE - sound like something else that has never existed before!

As a practical matter, I think a conservative approach is best for most people. Listen... Change devices... Listen some more... Add or subtract values... Listen.... Change device manufacturer.... Listen..... Until you you think you have a pretty good idea about what is "right." Write down what you have arrived at for brand, values, etc. Then... pull it all out and go back to the original "un-improved" version. If there is a big, night-and-day difference between the sound of the original and the sound you arrived at - the sound you "liked," it is time to BE SKEPTICAL! People are often attracted to - seduced by - rising midrange characteristics, a bit extra "ping," "sparkle" or "sizzle" in the top end. These tend to make a speaker sound louder and/or more "efficient." But it is NOT accuracy! This path leads to THE DARK SIDE!! As millions of Bose owners will tell you, it is not against the law or immoral to like crappy speakers. But it's a terrible shame to not recognize coloration for what it is - a departure from neutrality - from fidelity - usually deliberately and cynically engineered into products to appeal to a company's target suckers - uh... customers....

The difference between otherwise good A-25's with capacitors past their prime, and properly restored and carefully "re-capped" ones, is certainly noticeable, but it is not radical. The basic voicing of the speaker should still come through, but with maybe a touch more airiness. But if it now sounds like a JBL studio monitor, YOU'VE DONE SOMETHING WRONG!!! From here, you have three options: Back to Square One and this time DON'T SCREW IT UP! Or... Send them off to someone who is expert at restoring tired-sounding A-25's and PAY HIM to do it right. Or.... Revert the A-25's back to their original "un-improved" state, put them on eBay, and sell them to someone who will love and respect them for what they are. Then, do a search on eBay and apply the money you got from selling your dynacos toward purchasing the JBL studio monitors you really wanted in the first place.

Lastly, there is much about "capacitor voodoo" thrown about that is just that. People buy expensive "upgrade" parts based on recommendations they read or hear, they install them, and then they claim to see the whole Meaning of Life Itself revealed and the Universe laid at their feet! Yet most of the time, instead of real improvements we are dealing with experimenter bias, Hawthorne effect and placebo effect.

For more scientific and objective treatments of "Cap-ology", check out the links below:


http://sound.westhost.com/articles/capacitors.htm#ref

http://www.madisound.com/services/upgrading_speakers.php/#components

http://www.hificritic.com/downloads/APassiveRole.pdf

http://www.faradnet.com/

http://members.cox.net/pjay99/captest.htm

The reading can get a bit dry, and not all them agree, but if you slog through these, you will know how capacitors really work, what differences they actually make in loudspeaker performance and finally, perhaps saner approaches to rejuvenating speakers with tired caps.

Cheers!! '(lol)'