Why Recap Speakers and When?

[gkimeng]

Most old electrolytic crossover caps I test have ranged from 0.5 to over 1 ohm ESR. That's higher than they should be and, most likely were when new. That drifting gently softens the tweeter's output over time so it's hardly noticed, if at all.
However, when new caps with ESR'rs near or at 0 ohms are installed and the speaker fired up, the owner immediately notices a change, because it is a step change rather than a gradual one.
The question arises, at what point in the gradually escalating ESR curve is it time to replace old NPE caps? I don't think there is any hard and fast rule. My choice is >= 0.5 ohms. YMMV

Ultimately, I think the bottom line is that if they're your speakers and you're planning on keeping them you can do what you want, and if you think changing out anything improves the sound the only opinion that matters is your own. Of the dozen or so pairs of speakers I've been inside of over the years, only two pairs belonged to me, and I'm quite happy with the way they sound with all of their original electronics.

But if you're working on someone else's speakers, or restoring something of value with the intent of resale, owners or prospective buyers may not be very enthusiastic about you changing things they don't perceive as broken unless you're a pro with an established reputation for successful repairs/restorations/mods. Coincidentally, here is something recently said to me by someone who I think would be reasonably well-known to readers of this forum (not named here because it's a quote from a private email and I haven't checked to make sure it's ok to use it with attribution):

"I could tell you about a customer that sent a pair of AR 90 for us to completely rebuild the crossovers after some hobbyist thought he knew more than AR or the customer that paid $1000 for a pair of AR-LST and then paid us $500 to make them right."

 

[lorne]

But if you're working on someone else's speakers, or restoring something of value with the intent of resale, owners or prospective buyers may not be very enthusiastic about you changing things they don't perceive as broken unless you're a pro with an established reputation for successful repairs/restorations/mods.

You definitely have a point, and we can assume that most seasoned hobbyists have faced this dialemma even as they KNOW that modifications — or better still, UPDATES — can produce a better instrument.

 

[gkimeng]

You definitely have a point, and we can assume that most seasoned hobbyists have faced this dialemma even as they KNOW that modifications — or better still, UPDATES — can produce a better instrument.

When I buy things I plan on keeping them forever, so there's never a hobbyist dilemma for me (my wife is another story). If I'm working with something that belongs to someone else, that's also easy, let them decide and do what they want. If I were ever to buy something with the intent to resell it, I would go the "preservation and restoration" route, and mod nothing unless it was something with an established pedigree. For example, I don't think any AR turntable owner ever went wrong with a George Merrill mod.

 

[totem]

Rather complicated crossover?

Its been a learning experience reading the comments and suggestions in this
sticky
As far as the cap,s and the various options, I now have an understanding of what options are available.
I have a rather "busy" looking crossover out of a 3 way EV Sentry series,
of witch I neglected to photo prior to assembling so I have a link to DaWoofers
posted pic.
http://www.audiokarma.org/forums/attachment.php?attachmentid=56782&d=1186440854

There are 3 np 30uf 70 volt caps that I intend to change due to their age.
The rest of the crossover Is what I need a little help on.

Are there additional "while I am in there" things that anyone can ID in the pic
that I may want to look at upgrading.

There seems to be a harshness in the upper mids, lower treble area that I want to deal with.

I am not looking to do a total rebuild or redesign at this stage, but an
upgrade.

 

[spkrdtr]

Its been a learning experience reading the comments and suggestions in this
sticky
As far as the cap,s and the various options, I now have an understanding of what options are available.
I have a rather "busy" looking crossover out of a 3 way EV Sentry series,
of witch I neglected to photo prior to assembling so I have a link to DaWoofers
posted pic.
http://www.audiokarma.org/forums/attachment.php?attachmentid=56782&d=1186440854

There are 3 np 30uf 70 volt caps that I intend to change due to their age.
The rest of the crossover Is what I need a little help on.

Are there additional "while I am in there" things that anyone can ID in the pic
that I may want to look at upgrading.

There seems to be a harshness in the upper mids, lower treble area that I want to deal with.

I am not looking to do a total rebuild or redesign at this stage, but an
upgrade.

If you have a good LCR meter you should look at replacing those mylar caps also, measure those adjustable/fixed resistors and replace with like values in non-inductive, audio grade types and measure the inductance and DC resistance of those coils and replace with like values in air core types. This will run you some money though.
Your best bet is to draw a schematic and attack those components in series with the tweeter and mids first. re-assemble and listen for awhile before deciding if more compents need changing.
Good luck.

 

[lorne]

Cool. My 2 cents worth: I'd change out the old electros for some appropriate film caps and leave it alone ... see what they sound like. The new caps *may* restore some balance in the audible spectrum that has been lost. The freshened sound may have a more pleasing effect. If the harshness is an inherent part of the drivers, film caps will surely not improve anything. They may even reveal more of the same. Of course you also have the option of putting some nice modern NP electrolytic types in too.

It looks like there is a gain or roll off switch with two or three positions ...?? If so, get into that carefully with some switch cleaner and a Q-tip. Some people like to rewire or bypass in order to get a flat setting. But I'd just be sure the switch is in top condition and see what it sounds like in different settings. Such switches allow you to adjust the speaker voicing to different rooms. Sometimes I wish I had left some of my switch circuits in place ... or rather just substituted a new and better switch.

EDITED LATER: I just reviewed Carl's message. I think I'd go with his advice for sure.

 

[totem]

Thanks Carl and lorne for your recommendations.
Just to confirm from the pic posted I am on the same page in regards to iding
the various parts.

There are 3 dark caps 30uf 2 on bottom center 1 at the top
2 mylar caps, 1 yellow and 1 blue
6 coils
2 brown rods on the left? note sure on these
1 or 2 resistors on top of the 4th coil?

Give me a piece a veneer and I am much more comfortable!

 

[spkrdtr]

Thanks Carl and lorne for your recommendations.
Just to confirm from the pic posted I am on the same page in regards to iding
the various parts.

There are 3 dark caps 30uf 2 on bottom center 1 at the top
2 mylar caps, 1 yellow and 1 blue
6 coils
2 brown rods on the left? note sure on these
1 or 2 resistors on top of the 4th coil?

Give me a piece a veneer and I am much more comfortable!

Hey, we ought to pair up. I'm more comfortable with a crossover than veneer!
I believe those brown rods you refer to are variable resistors. They look just like the ones Peter Snell used to fine tune his early Snells to match SPL's of components. You can measure what the resistance they are set to and purchase the resistors I mentioned to equal those values.
Again, if you don't have an LCR or know someone who does and are able to draw a schematic, I don't recommend going hog wild with an upgrade. Just do the caps as I and Lorne have suggested.

 

[bowtieman427]

What are opinions on Dayton Precision 1% Metallized Polypropylene Capacitors. I am currently considering using them on my rebuild.
Thanks
Jim

 

[AU20K]

Thanks in advance.

AU

 

[Face]

There's a tiny blub here: http://www.soniccraft.com/sonicap_gen_2.htm
The shorter lead is shield.

 

[BECtoo]

Well, I should be embarrassed to be asking this, but I don't embarras that easily. Can/will anyone tell me; 1, if Sonicaps are polarized? and 2. if they are, wich end is which? I got Forte upgrade from B Crites and i thought I was setting neg in line until I looked at them with a magnifier and saw that the little neg thingie is actually the copyright stamp. Hmmm after 40+ years I realize I don't know S--t from Shinola about some things.

Thanks in advance.

AU

It does not matter at all which way you connect the Sonicaps. After all, all signals in a crossover are AC. Not possible for any capacitor used there to have a polarity since all signals in there alternate between + and -.

Bob Crites

 

[AU20K]

Great, Thank you both for the help.

 

[shacky]

Just recapped and refoamed pair of EPI 201's. They sound wonderful but I can't say exactly how recap changed sound as surrounds were the bigger problem.

Would like to measure old 10 uF caps but do not have equipment.

Anyone willing to have me send old caps to you for measurement - then disposal?

 

[spkrdtr]

Just recapped and refoamed pair of EPI 201's. They sound wonderful but I can't say exactly how recap changed sound as surrounds were the bigger problem.

Would like to measure old 10 uF caps but do not have equipment.

Anyone willing to have me send old caps to you for measurement - then disposal?

I'll volunteer. I have capacitance and ESR testers.
Write me privately for address.

 

[shacky]

Here are results from EPI 201 original caps. Thanks Carl!!!

capacitances: 9.5m 9.7, 9.9, 9.97
dF@ 1 kHz: 6%, 7%, 7.7%, 7.7%
ESR's: 1 ohm, 1 ohm, 0.9 ohm, 1 ohm

 

[spkrdtr]

Here are results from EPI 201 original caps. Thanks Carl!!!

capacitances: 9.5m 9.7, 9.9, 9.97
dF@ 1 kHz: 6%, 7%, 7.7%, 7.7%
ESR's: 1 ohm, 1 ohm, 0.9 ohm, 1 ohm

Shacky: The units on the capacitances should read uF.
BTW, they were labeled as 10 uF caps, so not much drifting on that property. However, ESR is another story.

 

[shacky]

Carl,

Sorry about that. And thanks for listing original cap value of 10 uF. I should have indicated that for those not familiar with EPI.

Can you explain why the ESR is a problem?

Jim

 

[spkrdtr]

Carl,

Sorry about that. And thanks for listing original cap value of 10 uF. I should have indicated that for those not familiar with EPI.

Can you explain why the ESR is a problem?

Jim

ESR means Equivalent Series Resistance. It is a normal property of all caps. Electrolytics are, by their inherent design, prone to have excalating ESR as they age due to changes in the electrolytic paste.
A new cap should have a very low ESR <<< 0.25 ohms. As NPE's age, ESR creeps up and up and in doing so, begins to act like a valve, gradually shutting off the voltage from reaching the tweeter or midrange thus reducing the highs those drivers are capable of. It basically begins to take on a secondary role; that of an added series resistor.
So, it's important to speaker 'health' to maintain a low ESR in order to keep the mid and high frequency performance output the same as when new.
Changing out old NPE's and replacing with FF types is a good way to prevent the problem from recurring.
I have discussed that in previous posts on this thread.

 

[The Reverend]

Hello,

I just bought a pair of Pioneer CS-R700 speakers and I a want to recap them. The crossover network is attached below. What I am wonderig is, if useing all Solen caps, if these are good choices:

35uF = 33uF||2uF (SOLEN-54968, SOLEN-55875)
14uF = 12uF||2uF (SOLEN-51556, SOLEN-55875)
18uF (SOLEN-62370)
1.3uF (SOLEN-62361)

All parts are from partsconnexion. Are there better ways to do this than paralleling for the 35 and 14?