• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

dynaco A25 super bright

D

dagray3

New Member
Hey, I recently picked up some A25s off ebay. I recapped them (5.1uF from Angela.com) and the high end sounds spectacular. The problem I am having is that the bass seems lacking. I feel that it's just not all the way there. If I adjust the crossover, the highs seem to get muddled (which is bad) but, of course, the bass stays weak.

I thought I had read that replacing the screws on the bass drivers could tighten up the bass?? Anyone have any advice on kicking my bass in a little?

I am running a Dynaco PAS3 and an ST70 to drive these speakers. My setup sounds good with other speakers (although the highs are veiled), so I don't feel I need to do any adjustments on the amp/preamp end of things.

I would appreciate any advice anyone has.

Thanks
 
Register to hide this ad
First thing I'd check is the polarity of the woofers. If you swapped them unintentionally when you did the recap, that might explain the bass suck.

What kind of caps did you use?
 
I didn't remove the woofer wires when I did the recap. So, if they were reversed polarity, I didn't change them. I suppose I could check and reverse the polarity and see if that changes it?? Is there a quick and dirty way to check if I have the polarity correct?

I capped with Angela 5.1uF matallized polypropylene caps (630V).
 
Sounds obvious, but maybe you reversed polarity of your speaker cables, then?

One way to test is to put your speakers face to face a couple of inches apart. Hook them up and play some music through them. If your polarity is reversed, they'll be really bass dead. If in doubt, swap the leads on one speaker and listen again. If should be pretty obvious which way is correct at that point.

Other possibilities?
- You are now hearing them for the first time as they were intended to sound... I doubt that, because A25s should have respectable bass, anyway.
- Your caps need to "break in"... I'm not even going to start that conversation! :no:​
 
dagray3 said:
Is there a quick and dirty way to check if I have the polarity correct?
Click to expand...

Using a 1.5v battery (C, D or whatever you have handy), hold the negative (-) speaker cable to the bottom and "tap" the positive (+) speaker cable
to the top. If you see the woofer "push out" and retract, your polarity is correct. If it "sucks in" first, you have polarity reversed. Do not use a 9v or you risk damage. 1.5v is plenty. AA, C, D, etc.
 
I can't remember the bass before I recapped. The highs were so muggy, I couldn't focus on anything else. Also, sinmce I had been reading these forums for a little before purchasing the A25s, I ordered the caps the day I won the ebay auction. So, I recapped without more than a half an hour of listening. But, from what I recall, the bass wasn't all that specatcular to begin with. I feel the sound is a little harsh at a normal volume on most songs. "If you want me to stay" by Sly and the Famliy stone has BEAUTIFUL vocals on these speakers, but Pink Floyd is just lacking in the bass, like the bass player is in the other room. I switched back to my Paradigm Monitors, and the bass thumps up (a little too much) and the upper end gets swallowed in cotton.

I know that too much bass can kill you sound, but I am fairly confident that the bass is just lacking on these. I don't know. If I flip on the loudness, the bass does kick a little more, but the rest of the sound is all screwed to heck. It just sounds weak right now.

I'll check the polarity with the battery and see what the deal is there. But, if my polarity were off, wouldn't the tweeters sound off as well (I guess unless just the subs were reversed?)? I'll also switch the polarity on my cables and see if that changes it.

On a closer inspection, one of the drivers is a little torn right at the center of the cone. I thought that should sound fuzzy, but I can't hear anything. The other driver looks good, but the speakers sound the same.

I'll keep you all posted. Thanks for the quick and multiple replies. I do appreciate it. Keep it coming.
 
You might want to check the XO wiring. I doubt reversed polarity would kill the bass that much. Usually +/- reversal just produces a phase-shift. The cap is supposed to be 5uf 50V. You used 5.1uf 630V? The Basel C2 1uf cap mod looks interesting. I'd probably try that with a bypass switch in case I thought it sucked.

a25oa9.jpg
 
The caps will have no effect on the bass. If the woofer has full excursion there is nothing wrong. reverse the phase playing music with deep bass the louder and bassier position is the correct phase. dynas are not thumpers they have a natural bass response.
 
I'm not quite sure if I've got this right, but the gist of it is true, so bear with me.

Sometimes when caps age they increase in ESR and actually hold back power from reaching the tweeter, so when fresh caps are installed not only is the value corrected back to the original design, but more volume is heard as more power reaches the driver. And sometimes this increase in highs causes an apparent DECREASE in bass due simply to the fact that more highs implies less bass.

So the bass may still be the same; it's just masked a bit by the more abundant highs.
 
I think I might agree with Andyman now. Like grateful says, the cap has no bearing on the bass. So, I am thinking that with the top end opened out so much, I think I am just missing the bass. On top of that, I am switching over from the monitors. I don't know. On some songs everything catches together perfectly, and on some it just doesn't mesh right. I guess I'll give my caps some age time and see if they mellow out a bit.

I got 630V caps just because they were the only ones at Angela that were 5ish uF. But, the extra voltage rating won't hurt anything, definately not the bass. I wanted to test out some of Angela's upper end caps and hear what they sound like. I had already recapped my amp and preamp with orange drops, so I opted for the angela metallized polys in my XO.

I also was playing around with my output impedance on my ST70. I can hook up either 4, 8 or 16 ohms outputs to the speakers. I had been running on 8, but the 16 sounds pretty good I think too, maybe even better than the 8ohm. I will give that a try and see as well.

I'll let you guys know.

Thanks for all the input.
 
How are the speakers set up? Are they on stands or on the floor? You have nice gear on them so I wouldn't see that being any issue. Mine sound best when closer to the wall to couple the bass response and stacked, they are even move impressive. To me, anyway.
 
I can't imagine anyone describing A25s as "super bright" unless something was wrong. The bass they make won't move the Earth, but it's so much more than your eye expects from a box that size they tend to kinda drop your jaw a bit upon first listen.
 
Another thing to remember is that the Dyna is closer to a NE sound, that is, a flat response. It does not design in a hump in the bass as so many speakers do since the beginning of the '80s. I've head number of good speakers with well balanced bass where others listening and more used to newer design philosophy will say the bass is lacking. I've noticed more oft than not when there is a bass hump the bass seems to go lower though in reality it is only more pronounced but loses much of the detail that good bass should have. In the extreme it can sound like what I call a one note thumper. Can not hear the attack or decay what so ever.
 
It seems funny to hear "super bright" and Dynaco A-25 mentioned in the same sentence. My A-25's are the least bright speakers I have ever owned. They lack deep bass, but are not bright at all, and are actually a bit veiled imo. The only thing I can think of is your speaker wire polarity is reversed on one channel, or maybe the fiberglass matting got shuffled around when you recapped and has changed the cabinet tuning. The insulation is basically what tunes these speakers, since they are vented, but don't have a port.
 
zilch, I didn't quite understand your curves. I checked, but I didn't really see what you mean. You mean I need new drivers? Replacement drivers?

My speakers are on stands, probably a tad bit too high, but not by much. They are about 6-8 inches off the wall (sound about right?). I switched the polarity on each speaker, one at a time, and didn't notice any real improvement.

I will doublecheck the insulation and make sure that it's still in place after the recap and moving.

I still think they sound bright. It could be that I am used to a different tune on the speakers, I suppose. Or, it could be that I am hearing differences in the style of the artists? I don't know. Maybe I'll get a couple of audiophile guys over for a listen to see what they think. Maybe it's my taste?

I mean honestly, I haven't screwed around with vintage speakers yet, but can the drivers go weak? Do they either work great or not at all? Or, do they get less responsive after time? The XO shouldn't have anything to do with it. Is it possible that my drivers are just a little tired? MAybe stored improperly or something?
 
Zilch means they roll off in the bass below 60 hz or so. They don't have the hump at 60 hz that many modern speakers do. This hump gives the illusion of deep bass. Speakers like large Advents and big AR systems are good down to 40 hz or so. They don't have the hump and go as deep as many subwoofers. They are the most accurate in the bass range.
 
I suspect your speakers are fine, and your expectations at variance with how they actually perform.

A-25s don't have much in the way of bass to begin with.

It starts rolling off around 100 Hz, and by 40 Hz, there's effectively nobody home down there, even if you have them against the wall.

You'll get a bit more positioning them in corners.

Use the attenuation switch to adjust the highs for the best balance. Even at the highest setting and on axis, they do not measure as overly bright.

Post pics so that others can ascertain whether the drivers are "correct."

Show the cone tear close up so we can see if it's a problem.
 
You must log in or register to reply here.
Back
Top Bottom