dynaco A25's

[craig]

Have two pairs of A25's recently had one rehabbed with mixed results, they seem a little too bright for me now, wondering if anyone on here is from chicago and rehabs dynaco A25's thanks

[kirk57]

I'm in the Chicago area, but can't help if we don't know the specifics

[craig]

Ok, This is what happened, i have 2 pairs one is in cosmetically better condition then the other pair one pair souded slightly better then then other pair then one day the better sounding pair lost bass on one side. I took them in for repair ( turned out to be a human hair) , the salesman talked me into rehabbing the crossovers, i think that was my mistake, don't change something that sounds right to begin with. It seems like the sound is a little tighter and cleaner as he says but when you turn it up loud the highs almost seem piercing, cleaner yet not as warm, the bass seems tighter but weaker, the over all sound at low volumes sounds more effortless but little weaker yet tighter in bass. I'm not sure what to make of it, the other pair wich used to be the duller pair now seem the best. As for the details, I think he replaced the cap was leaking at about 7uf with a bigger clarity brand cap of 5 uf, he also replaced with tweeter wire with some weird thing cotton dialect wire, and he said he doubled the negative on the return or drain. They don't sound bad they just don't have the warm gain they used too. I miss the way the used to sound. Not sure weather returning them the way the used to be is the best solution maybe i should add another cap? My pre amp is the weak part of my system maybe the rehab is bringing out imperfections of my pre amp at louder volumes ?

[Horswispr]

Dynaco crossovers are really simple, and re-capping them is something you can do yourself. If there was a 7 mfd capacitor in a Dynaco A-25, then I'd think someone had replaced the original somewhere along the way. The original caps were always either 4.7 or 5.1 mfd (in my experience). In theory, going from 7 mfd to 5.1 mfd should make the tweeter work LESS hard at the bottom of its range. It should also make the speaker sound a little less bright, as you're starting the tweeter's roll-off (at the bottom of its range) at a higher frequency. If the old tweeters were becoming "resistant," then new caps would brighten things up a bit. But I don't think capacitor "break in" is audio voodoo. I find that new caps sound bright when I first put them in, then mellow out after a few hours/days of listening. There should be NO effect on the bass, as the Dynacos' woofers are fun "wide open" with no coil or other "stuff" before them. Have you given the "brighter" Dynacos a chance to "break in" with their new capacitors?

[craig]

not really but he told me i should do that i read on the web people are divided on weather break in on a cap is real i have no idea, but right now they are back in his shop, i did a ton of tests using same channel and one of them still sounds distorted compared to the other one. i called him today he told me 3 days he should have them done. i hope its not the voice coil or something he cant fix knowing i already took them back after rehab once because some hot glue got on something and caused the pot control for tweeter not to work, he fixed that i took them home, this distortion on one side is kinda slight and hard to detect but when i played rubber soul then used only one channel from amp switched out speaker and heard it on same side same song , then i noticed a big difference both sides are pushing more but one side handles it giving this great tight low end while the other one does all of that but in a more distorted way. It ruins the bass imaging as well as the overall sound enough so i took them back a second time . hope he doesn't think i'm crazy but i left him the cd i used as a test and i think he will notice it

[Horswispr]

If the problem is with the woofer, then it probably means the woofer itself is blown. The voice coil Is probably rubbing. I've had Dynaco woofers that distorted some of the time but not all of the time. I simply replaced them. You can find Dynaco A-25 woofers on eBay for about $25. Replacing capacitors would make NO difference in the sound of the woofer, as the capacitors are on the way to the tweeter only. But I'd think your repair guy would have tested the woofer before doing all the other stuff. Replacing a Dynaco woofer takes about 15 mins.

[craig]

The woofer doesn't seem blown, it just seems a little fuzzy all the way around compared to the other channel witch seems pretty nice. The bass works and does not give the sound a blown woofer would normally give it just seems the roll off is more fuzzy then the other channel, but i guess it's possible the woofer is blown, ( i hope not ) but it does not pop way out or anything and it still gives bass and looks mint . I guess i will find out in a few days what it is , the guy doing the work is van speakerworks chicago some people on here told me he's pretty good though he did more then i asked for on them. the one channel seems pretty nice though and it took me a while to even realize they were not performing the same, it was not obvious until i tested the same side of amp on the song yellow submarine i know that sounds goofy but the bass intro on the left side of that song has a very distinct bass roll over so from channel 1 on the amp i tested one speaker played song then tested other on same side of amp and it became more obvious one had a cleaner roll off from the bass then the other side, and seemed a tad more effortless very slight on the effortless difference. but enough to ruin them for me if they cant be fixed

[Horswispr]

I'm not sure what "clean roll off" means, but if something sounds fuzzy, then something's not right. I've had Dynaco woofers here that looked great and didn't "rub" when I gently pushed them in, but still distorted slightly on some notes. There were something like 600,000 Dynaco A-25s made in their day, and the surrounds don't deteriorate, so there are plenty of orphaned functional Dynaco woofers to be had if that IS the problem.

[craig]

interesting thanks for the advice, it seems to all the way around to be the woofer, i think its the voice coil but i could be wrong, in any case the guy working on it is pretty good i'v had him do other great work for me, so i will hope for the best and let you know next week what happens .

[Martin]

After extensive listening (maybe I should say "abusive listening" as I was 16 at the time), to my first-ever pair of A-25s, I had the same woofer problem. I called Dynaco in PA & described the problem. They sent a new woofer immediately, I made my first speaker repair and it corrected the problem completely. In 40+ more years of enthusiastic listening, I've never had the problem again: All my Dynacos have been properly fused since then.

[craig]

Wow !!! i need to call them ! I just got them back from rehab shop and the guy told me he cant fix them after rehabbing them ! He went on to tell me nothing in his crossover rehab would be to blame , but admits the driver on one side is short 3db's of lower mids / upper bass . I went on to tell him i wish i had known cuz i might not have spent the money to have them rehabbed and he said he didn't know and assumed they were mint when he did the rehab going on to say its subtle and in the driver itself not the crossover. Anyway i didn't complain much else about it he has done other excellent work for me and i was glad he didn't beat around the bush or lie about the problem but i'm left with a pair of A25s that are 3db short on one channel for the upper bass and lower mids. Do you have the number ? does dynaco carry vintage A25 drivers ?

[Horswispr]

There is no Dynaco to call any more. Hasn't been for years. Just look for a decent Dynaco woofer on eBay. Or advertise asking for one on Craigslist if you live in an urban area. Might cost anywhere from $19 to $35. Don't pay too much.

[ironlake]

I had something similar happen in 1966 when I got my ar 2axs new. At a certain frequency there was a buzz in the midrange of one speaker. I finally took it back to the dealer before warranty went off. I did a frequency sweep on the speaker and at some frequency in the 3000 hz area it would buzz. They put in a new mid range and no more problem. Must have been something in the voice coil as what else would cause that.

[billyboy]

I'm sorry, but you guys seem so 'ignorant' about what causes speaker failures, I thought I must respond. I have been in the commercial sound business for over forty years now, and have worked on thousands of speaker systems in that time.

Any speaker, whether woofer, tweeter, midrange, whatever......has a coil of copper 'wire' forming the voice coil. This 'wire' is covered with a coating of varnish, to provide insulation between the windings. May be old time varnish, or some new synthetic. No difference, really. If you pump a lot of power into the speaker, too much power, it has no way to dissipate the heat developed in these coils. The varnish boils, and produces, first, bubbles in the insulation. If you continue from this point, the wire will melt, and you will loose continuity. The speaker will, literally, be blown. No more sound......EVER! If you stop before this point comes, the varnish will cool, and re-solidify into whatever shape seems right, at the time. No telling what shape this is. It is never the original uniform shape, though. Forever after this event, the speaker coil may rub against the magnet at certain points. This is what causes the 'fuzziness' of sound. It may happen at only certain frequencies and certain sound levels, but , IT WILL HAPPEN! Your only solution, then, is a new, or better driver. As someone has said here, they are still around, to be had, at a reasonable price. The only thing is, you never know if they have been abused, until you listen to them, in their original environment. Be very careful. There is no other way to tell what they sound like without listening to them.

I'm listening to a pair of A35 speakers right now, which I purchased in 1972. They still sound great. I have avoided over stressing them all these years. I did blow a single A25 once, by letting my stupid guitar friends use it as a vocal speaker for their band. The A25 is really only good for about 25 watts rms. They were running it off of a 250 watt amp. Need I say more? Anyway, back then, I was a Dynaco distributer, and they sent a new woofer at no cost to me. No one would do this now. Times have changed...............

So........As far as I am concerned, the A25/A35 are the best sounding speakers of their size ever. No doubt. As with any bookshelf sized speaker they are not for GodAwful blistering listening levels. For that, you really need more size. But, in the correct environment, they can't be beat. (AR guys, eat your heart out. I have seen many blown AR speakers, and many with bad speaker suspensions. I am not that impressed.)

[Carlspeak]

Yes billyboy, it's that ignorance of vintage speakers succumbing to a beating from modern high power amps that keeps me busy.

[dynaco_dan]

I do not appreciate reading the word, "ignorant" as a comment here on CSP.

Not everyone has your life experiences.

New members bring both silly and great questions to this site and every other site.

That is how we all learn.

Even with my experiences, I still am learning new things and once in a while say something wrong or silly.

[dynaco_dan]

I'm not sure what "clean roll off" means, but if something sounds fuzzy, then something's not right. I've had Dynaco woofers here that looked great and didn't "rub" when I gently pushed them in, but still distorted slightly on some notes. There were something like 600,000 Dynaco A-25s made in their day, and the surrounds don't deteriorate, so there are plenty of orphaned functional Dynaco woofers to be had if that IS the problem.

Hi there

There was over 1,000,000 A-25's produced, meaning a super abundant potential supply of usable OEM Seas/Scan woofers.

A fuzzy sound in my opinion is possibly bubbles formed on the voice coil wire insulation from over-heating thereby rubbing slightly in the gap.

There was numerous cases of actual voice coil separation from the voice coil paper form which Dynaco did cover under warantee.

A caution in testing, be certain each woofer is 8 ohms and not the identical, physically at least, 4 ohm driver.

Using a 4 ohm driver will increase output about 3 db over the original 8 ohm woofer or tweeter causing a sound imbalance.

UPDATED 20120529 6:45PM

I forgot to mention that if a woofer is replaced, the identical woofer does not need to be required.

If a round framed woofer is stock, then a horned woofer will be adequate if the horns cabinet recess is chiselled out, an easy job.

I haven't measured but I believe that the reverse will work as well.

Only the correct model will work though, and watch out for the 4 ohm version used in other brands.

UPDATED 20120607 11:55PM

I change my wording of the previous update.

The identical woofer, "should not" be required.

I meant to include both Scan and Seas 8 ohm OEM woofers, round or without horns,

Unless someone comes forward that there is an audible difference between these different woofers.

[craig]

hey kirk if your in the chicago area i could use some help, i'v had these back a while now and i have a feeling it's the way he redid the wiring but im not sure, there was never a 7uf cap he said the original was leaking to almost a 7uf , he replaced it with a 5 uf cap, the bass seems tighter and the highs seem good but it just lacks synergy like it used to, i think i want to go back to orginal set up for wiring, the bass seems almost too tight and strong for the box then gets to bright when turned up, they didn't used to be like that.

[Horswispr]

Bright bass doesn't make sense. Do you mean the speakers sound bright when they're turned up? What amplifier are you using? Vern's point about checking to make sure the woofers are identical is a good one.

[dynaco_dan]

Bright bass doesn't make sense. Do you mean the speakers sound bright when they're turned up? What amplifier are you using? Vern's point about checking to make sure the woofers are identical is a good one.

Hi there Craig

You've had many changes done to your speakers, which have not been accurately documented.

Some changes sound like snake oil, as I read it, IMHO.

I would trust someone, like Kent, for just one example, someone not in any hifi business, to assess what was originally needed to be done and how to proceed with the repair.

The techie may be very competent and maybe what was told to you was mis-interpreted by you and you wrote what you believed to be correct.

If you lived here in Vancouver, I would have loved looking at them first, not after someone else has done some work on them.

They are a very simple speaker system compared to some others.

The drivers may even be out of phase in one or both of the speakers, for just one example.

The original problem, if any, would have taken less than 15 minutes to diagnose.

We are reading your writings trying to visualize what may have been done by the techie.

It is very difficult to read the continuing story here and try to put the pieces together, at least for me.

I may have serviced over 200 Dynaco A-25's under warantee but I still don't know everything yet.

[Horswispr]

I would get a fully functioning A-25 (not A-25XL) woofer on eBay, install it opposite the one it matches, and go from there. The "double negative" thing (that WAS your speakers, right?) should make NO audible difference. High quality 5 mfd capacitors (already in there) should make A-25s sound as good as they can. Dynaco A-25s do sound best with good amplifiers, and good tube amplifiers in particular. They are very "neutral" (a good thing) and do not hide mediocre source material. As I write, I'm listening to a pair driven by a 1960s Fisher tube amplifier (7868 output tubes) and the sound is wonderful.