A25 xover / Questions about replacement

[Guest denmarkdrivers]

Hi i own a couple pairs of A25 bookshelf speakers.

I want to replace the caps and im looking for suggestions

Should i use orginal values ?

If i use different vaules can the tweeter and drivers handle them ?

I'm sure you guys know im a fan of the A25s as far as the cone and surround goes, I'm not really sure how good the magnent is behind the driver, could they handle a modded xover ? or should i keep within orginal values?

The caps are very old, Will replacing the caps to orginal values improve the highs ?

What other contacts inside should be cleaned ?

I'm leaning towards using orginal values but im open to ideas.

I'm curious to hear other peoples results with modding or replacing A25 xovers.

thanks for your help craig

[dynaco_dan]

>Hi i own a couple pairs of A25 bookshelf speakers.

>I want to replace the caps and im looking for suggestions

>Should i use orginal values ?

>If i use different vaules can the tweeter and drivers handle

>them ?

>I'm sure you guys know im a fan of the A25s as far as the cone

>and surround goes, I'm not really sure how good the magnent is

>behind the driver, could they handle a modded xover ? or

>should i keep within orginal values?

>The caps are very old, Will replacing the caps to orginal

>values improve the highs ?

>What other contacts inside should be cleaned ?

>I'm leaning towards using orginal values but im open to

>ideas.

>I'm curious to hear other peoples results with modding or

>replacing A25 xovers.

>thanks for your help craig

Hi Craig;

I thought someone else would have answered your question by now.

Oh well, I'm here to offer a wee bit of advice for you.

The woofer has no inductor, so it rolls off at both ends naturally, the tweeter has the cap, so that bass does not load the tweeter down.

Nothing you can do to raise the woofers upper end, the cap controls the bass from damaging the tweeter.

A change to caps of the same value, maybe Solen or other brand should offer you a clearer highend.

The jury is still out as to which cap brand to use, as a rule.

A written report of a modder trying several different brands of caps would make for some interesting reading.

You may need to burn them in for a week or so to hear it's final sound quality.

If you have looked at the Dynaco A-25 crossover you will note that there is 6 resistors and one NP cap with a MBB or shorting 5 position switch.

If you have Cramolin or Deoxit, I would apply a smidge amount to the switch contacts.

I see now that the resistors and cap are stuck to the crossover board with pretty blue/green goop, the same they used to seal the drivers with, and attach the cloth frame to the enclosure.

Please do a report of your results.

Good luck.

[Guest denmarkdrivers]

Thanks you probally did anser it already im spacey sometimes.

I've opened the other pair but im afraid to open this pair, i remember opening the other pair and seeing the cap, not sure if it was a cap or a big giant resistor ( hehe)

I think i ended up replacing the wrong thing on that pair, they still work but i replaced something that said "reverseable" on it .

I remember matching the value to a radioshack resistor, in short i should leave this to the pros.

The other pair i have i got about six months ago at a resale shop for 12 bucks, I havent opened them just took the covers off, they are the pair that dont show glue marks on face.

I like the way they sound im afraid i'll ruin them if i open them.

I remember just getting the drivers off the last time was not easy the black gooo they used as a seal was hard to deal with.

I probally sound like a moron compared to all the electrical engineers on here but i might as well be onest and leave this pair to the pros if i decide to have the caps replaced.

Just wanted to sound like i knew what i was doing i saposse.

If this replacement was done correctly how much would it really help ?

Would it make them actually sound brighter?

Why would the brand of the cap make a difference if its the same vaule ?

My understanding is caps wear down faster then resistors, is this true even during the time the A25s were made ?

even as they sound now they took my B&Ws bragging rights away from this room.

i would love to replace stuff inside i know is worn out but i dont want to change the charactor of the sound too much, i'm a little torn on weather to have it done or not.

I saposse its impossiable that nothing needs to be replaced after all this time huh ?

[dynaco_dan]

> Thanks you probally did anser it already im spacey

>sometimes.

>

> I've opened the other pair but im afraid to open this pair,

>i remember opening the other pair and seeing the cap, not sure

>if it was a cap or a big giant resistor ( hehe)

>

> I think i ended up replacing the wrong thing on that pair,

>they still work but i replaced something that said

>"reverseable" on it .

>

> I remember matching the value to a radioshack resistor, in

>short i should leave this to the pros.

>

> The other pair i have i got about six months ago at a

>resale shop for 12 bucks, I havent opened them just took

>the covers off, they are the pair that dont show glue marks on

>face.

>

> I like the way they sound im afraid i'll ruin them if i

>open them.

>

> I remember just getting the drivers off the last time was

>not easy the black gooo they used as a seal was hard to deal

>with.

>

> I probally sound like a moron compared to all the

>electrical engineers on here but i might as well be onest and

>leave this pair to the pros if i decide to have the caps

>replaced.

>

> Just wanted to sound like i knew what i was doing i

>saposse.

>

> If this replacement was done correctly how much would it

>really help ?

> Would it make them actually sound brighter?

>

> Why would the brand of the cap make a difference if its the

>same vaule ?

>

> My understanding is caps wear down faster then resistors,

>is this true even during the time the A25s were made ?

> even as they sound now they took my B&Ws bragging

>rights away from this room.

>

> i would love to replace stuff inside i know is worn out

>but i dont want to change the charactor of the sound too much,

>i'm a little torn on weather to have it done or not.

>

> I saposse its impossiable that nothing needs to be replaced

>after all this time huh ?

>

Hi again;

You are doing a good job of explaining everything to us.

The, reversible, was probably a Jensen cap from Denmark.

This is a non-polar capacitor not a resistor.

The darker square blocks are the power resistors.

If you decide to replace a cap in a crossover, such as in the Dynaco A-25, you can use a Solen capacitor, as being acceptable by some listeners and more readily available.

To the, "Golden Ears", there is better caps, meaning usually more money, but made by different manufacturing methods and or materials.

The jury is still out, as to which is the very best caps, but the Solens should be better than the OEM stock Jensen's used 25 years ago, today.

I understand that perhaps a week of non-stop music or similar signals applied, or repeat with a cd player, with the speakers face to face and out of phase, will break-in or burn-in the cap.

Meaning it should be operating at it's maximum performance.

The new cap should, in general practice, may be more acccurate than the original cap, and the highs, perhaps clearer, maybe not initially.

If you can lookup any write-ups where someone has replaced speaker caps and wrote their commentary this would be of interest to you.

The cap must be of the same capacitance and perhaps 100 volt rating or more if available, with Solen they are higher rating caps.

Good luck.

[Guest denmarkdrivers]

how much would i expect to pay to have this done for me ?

[dynaco_dan]

>how much would i expect to pay to have this done for me ?

Hi Craig;

My best advice to you, is, if you are not having any problems with the A-25's, don't even remove the grill cloths or drivers to look inside.

Just enjoy them as they were meant to be.

Good luck.