Help with crossover capacitors


I am re-capping some Altec Lansing 890C Bolero speakers.  They have 6uf/50volt and 3uf/25 volt caps.  What will change if I use 5.6uf and 3.2 caps?  I can't find the exact 6uf and 3uf values.  Should I go a little bit higher on those values or lower?  Any suggestions?  I'm looking at Dayton, Mundorf or Jantzen caps but I'm open to suggestions.

dannybad
The value of the cap changes the frequency response of the circuit. Such slight changes will be very hard to hear. Essentially all that will happen is one driver output will be a fraction of a dB higher or lower. But because the values are so close this will only affect a very tiny frequency range. In other words very, very hard to hear any difference- from this aspect of the cap swap.

Each different cap however will have its own individual sonic signature, and this by contrast will be across its whole range and so very easy to hear. Bearing that in mind I would not worry too much about the values. 

In other words, you will know instantly that you changed the caps. But the difference you hear will be due to the brand of caps and not their values.
Thank you for a clear explanation!  Is there a reasonably priced cap that you recommend?  
I would stick with the original values. Easy to do. Don’t accept 7-10% variance! Order your caps matched within 1% for right and left speaker. Don’t buy Dayton. If you don’t want to spend much, then get Clarity CSA 250v. They have a 3uf. For the 6uf just combine a 5.6uf with a .33uf 630v.

If you are ok with spending more look at the Jupiter VT line. Best to stick as close to the original values as possible.

Also, replace those sand cast resistors with Mills MRA12. Much better sounding!
By combining capacitors would you just solder them end on end?  Big one first?  I have a ton of soldering experience but I don't know the science very much.  And what don't you like about the Dayton stuff?  Have you done an A/B comparison?  Is that different?  I have well trained ears but I also don't need the most amazing system. I was given these speakers so I don't know how much difference it will actually make between the Dayton and something like the Clarity caps.  I'm not going to spend any more than $50 a speaker to re-cap them.
Go with the Clarity. Yes they sound better in every way compared to the Dayton caps. No contest. When combining caps to achieve the value you want you simply parallel them. Stack them with the small one on top and simply solder the leads on each end together. 
Be careful dannybad, a lot of people around here are eager to advise on things they have no actual experience with. Differences between caps are easy to hear. I'm talking electrically same value caps. Back when I didn't know this the designer of my speakers sold me a tweeter upgrade that called for a different crossover. He gave me the circuit which when built sounded nothing like what I had heard in his lab. It sounded like crap! After asking a bunch of questions and being assured I used all the correct value caps and resistors and point to point soldering he finally asked which caps? Well, Radio Shack. A week later with a Hovland MusicCap and Holco resistor and wow, magic! Bye-bye grain and etch, hello lovely liquid music!

Bear in mind this was going from Radio Shack caps sold five to a pack for a buck fifty, to Hovland MusiCap sold one for about $35. How much difference you hear will depend on what you're comparing. In any case, as long as your values are as close as you're saying then virtually all of what you hear will be due to the caps themselves and their quality and NOT have anything to do with the values being slightly different.

If your crossovers are working then I'm not even sure why you would want to replace the caps, as there's a lot easier/better places to put your money. That said, if the caps in there now are as cheap as they probably are then you should be able to easily hear improvement in smoothness and detail when upgrading to some quality caps.
I appreciate everybody's perspective on this as I'm sure there are different approaches and I will have to sort through it and figure it out myself and allocate my budget accordingly.
Millercarbon, I can definitely get with the idea that there will be a difference in Radio Shack caps and other more expensive brands.  I will look for a medium priced brand.  I am re-capping these speakers because they are 50 years old and I would like a fun project to do and when I re-capped a 35 year old mixing console (Soundworkshop 1600) I immediately heard a significant difference.  So, I'm just having some fun. 
Goodness Miller look at my feedback and the fact that I build and modify gear and cables for a living now. Been at this for years. Strange comment. Anyway, what I gave for advice is very straight forward, reasonable and smart.

Also, replacing those sand cast resistors with Mills MRA12 will also pay off nicely sonically. They cost $4 each. I would be willing to help you plan this out etc.... Done this for many A-goners.

I have upgraded so many speaker crossovers over the years that I lost count. I have vast experience with cap and resistor brands and have done the critical listening tests over and over. It is my particular passion and joy. See my virtual systems for some of my speaker and amp upgrades as well as tube amp builds 

Have fun.

Bill
Bill/Grannyring- I was just looking at those resistors and it's definitely worth giving it a shot at replacing.  I will include those when I do the work.  I am currently looking at either Clarity CSA caps or Mundorf Evo oil caps.  Each one will cost me about $150 total to re-cap at the same values.  I think I've got the idea, I just have to go back and check the resistors on those speakers and make sure I get the correct ratings.  I appreciate everybody's comments and ideas.  It is very helpful and is making this all fun.
HCouple of things to consider. The Evo caps have a sound signature that is more hot in the presence area. They sound a tad tipped up in the highs and upper mids and not as full bodied as the Clarity. The Clarity CSAs are more even handed in the highs and upper mids and sound more natural based on my experience. If you are looking for more sizzle and energy in the upper mids and highs the Evo would be a good choice.

Parts Connexion is having a 25% off sale and the Clarity caps are included. Perhaps even the Mundorf? You should be able to recap within your budget. The 3uf caps are $6.75 each and the 5.6uf caps are only $8. 
I would prefer to not have anything hyped but realistically it's all going to be a proper upgrade.  I will check the sale.  I thought the CSA's were more expensive than that, but I will order them now if they aren't.
The 5.6uf caps are not available.  Could I just use 2x 3uf caps in parallel to replace the 6uf caps?  Then I just order all caps of the same size.

And another question:  The resistors are 30ohm 15watt and 15ohm 10watt.  Mills makes both of these in 12 watt versions.  Will this work?
Yes on the two 3uf caps.  Now you’re thinking! Yes, the Mills will work fine. 
Just ordered it.  Thanks.
Just one caution: how hard do you drive your speakers? The 300R, 12 watt resistor may get hot when used hard, in place of a 15 watt. Have you considered doubling up in parallel? I would be sure to meet or exceed all voltage and power specs, and match values of resistance or capacitance as closely as possible.

Rather than brand name, consider technology when buying caps. Film and foil is notably better than any metallized product. I like tin foil and styrene film, especially from MIT multi cap - pricey, but worth it in spades. Mills is good unless you have deep pockets.
These speakers are rated at 50 watts at 8ohms.  I'm going to buy the Yamaha s-501 which is 85 watts per channel at 8 ohms.  I will turn them up and listen to them loud sometimes, but "loud" is a relative concept.  How exactly would I double up in parallel?  Would I just use 2 of the same resistor?  
Those are modest figures - I think you should be fine. I would not bother. But if you want to do so, the rule is twice the resistance for two resistors in parallel.
Great.  I think it will be fine as I really don't push them too much. Thanks for commenting.  Everyone on this thread has been so helpful.
And another question:  The resistors are 30ohm 15watt and 15ohm 10watt.  Mills makes both of these in 12 watt versions.  Will this work?
Two 15ohm 12watt resistor in series will give you a 30ohm 24watt.
I get that, but does that actually deliver more wattage to the speaker? Or does it give headroom to the circuit?
Post removed 
The resistor power rating is the maximum amount of power that the resistor can withstand. It won't give your speaker more power, I believe the designer use a 15watt resistor for a reason.

Paralleling caps to make up the correct value sounds better than a single cap as long as they are equally the same quality. Have a look at Dueland you can get those from Hi Fi Collective.
Chaps,
When you parallel caps and resistors, you also change the inductance, which may or may not affect the sound depending on the rest of the circuit.

danybad:
I would remove the shelving control and associated resistors to make the system flat , get a good air or ferrite core inductor, improve layout so the cap is not in the inductor magnetic field and anchor the parts to they don't flap about in the breeze.

Be advised that it is impossible to evaluate a capacitor [-or anything else-]  in isolation. A cap that is a bit zippy with a ringy tweeter may be dulcet with a soft dome.

FWIW, I used Dayton pp to replace mylars on ancient Audax silk dome tweets and they are stellar.
Hi @dannybad ,
You can try to bypass compression driver filter capacitor with Duelund Cu-Sn 0.01uF bypass capacitor.
I did it in my Altec 604E with vintage oil 4uF capacitor and with Duelund RS main 3.9uF capacitors. I like results in both cases.
Even in parallel with already very good Duelund RS capacitor, bypass capacitor my speakers sounded more vivid, organic, with better tone. Only drawback was it made sound a little bit less focused.
In case of  vintage oil capacitor the difference cause by  Duelund Cu-Sn 0.01uF bypass was even more positive.
Regards,
Alex.
Alex is spot on as I use the .01 Duelund tinned copper cap all the time. Only issue is they are out of your total budget unless you splurge 😊. 
It just possible option.
On the first stage to update the crossover with not expensive and good sounding capacitors.
And if you like result go to the next step of upgrade.
There are a number of options there including use good bypass capacitors.
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Just one caution: how hard do you drive your speakers? The 300R, 12 watt resistor may get hot when used hard, in place of a 15 watt. Have you considered doubling up in parallel? I would be sure to meet or exceed all voltage and power specs, and match values of resistance or capacitance as closely as possible.

Rather than brand name, consider technology when buying caps. Film and foil is notably better than any metallized product. I like tin foil and styrene film, especially from MIT multi cap - pricey, but worth it in spades. Mills is good unless you have deep pockets.

This is backwards
Two 15ohm 12watt resistor in series will give you a 30ohm 24watt.
You want to parallel resistors to increase wattage.


rocknss,

this
Just one caution: how hard do you drive your speakers? The 300R, 12 watt resistor may get hot when used hard, in place of a 15 watt. Have you considered doubling up in parallel? I would be sure to meet or exceed all voltage and power specs, and match values of resistance or capacitance as closely as possible.

Rather than brand name, consider technology when buying caps. Film and foil is notably better than any metallized product. I like tin foil and styrene film, especially from MIT multi cap - pricey, but worth it in spades. Mills is good unless you have deep pockets.

This is backwards
Two 15ohm 12watt resistor in series will give you a 30ohm 24watt.
You want to parallel resistors to increase wattage.
You can in series or parallel resistors to increase wattage!

You can parallel two 60ohm 12watt resistors to get the same result.

P= V x I

Two identical resistor in series, each resistor only see half of the voltage.

Two identical resistor in parallel, each resistor only take half of the current.