Crossover Question: 12.5 uf vs. 13uf?

[John Pearlman]

Got a crossover question for you guys. I have to redo the AA networks in my La Scalas and I have decided to go with the standard GE motor run caps as suggested by Bob Crites. My question is this: The Grainger book lists 12.5uf caps and I need a 13uf. I can do a 3uf and a 10uf in series but a single cap would look cleaner. Could I get away with .5uf difference or would it really effect the sound? I suppose to properly rebuild them I should do the two in series, but what are your thoughts?

Thanks for your time

John

[Jay L]

12.5 will be ok. its within 5% tolerance

[Deang]

You would do a 10 and 3 in parallel -- not in series. Paralleling lowers ESR, but the ESR on those caps is so low already there isn't much to be gained by doing it.

12.5 is only within 5% if it actually measures 12.5 to begin with. At any rate, with a first order network the rolloff is so shallow and drawn out that it's very unlikely you would hear an audible difference unless you were approaching 15%.

[John Pearlman]

Ok, sounds like a plan. I figured it wouldn't matter because it is so close and the caps Klipsch used probably didn't measure exactly 13 to begin with. It would be a much cleaner layout to boot.

Thanks

John

[BEC]

John,

Just one point. The GE 12.5 uF is physically much larger than the lower value caps. Look at the dimensions.

Bob Crites

[John Pearlman]

Hi Bob

Thanks for pointing that out. As long as the value won't affect the performance I don't mind because I will be building a new crossover board anyway.

Thanks

John

[BEC]

John,

I keep the caps and mounting brackets for mounting them horizontally in stock if you are interested in getting those. The brackets are a bit hard to find. In fact, I had to have them manufactured.

Bob Crites

bobcrites@centurytel.net

[John Pearlman]

Hi Bob

I think I'm going to machine some PVC or Delrin brackets for the caps or perhaps even some wooden ones. How much do your brackets cost? I am also interrested in your use of spade lugs for connections to the caps; why not solder them directly? I would assume this is a better connection.

Thanks

John

[BEC]

John,

Soldering is good and crimping lugs is good. I do some of both. There are arguments for both ways. My most recent background is nuclear power. Way back in the last century, those folks decided that signal wires are better crimped. The arguments for and against soldering and crimping are almost beyond the comprehension of humans. I think that most of the arguments in the nuclear power industry revloved around how to prove a connection was good. You can observe and test a crimp connection. You cannot know what is inside a solder connection. Quality of a solder connection could only be verified by observation while the joint is being made. If you do crimp, you need a good ratcheting crimp tool.

The brackets I have are 50 cents each.

Bob

[3dzapper]

Here is a deal on GE12.5uF caps. 5 for $12:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7526255520&rd=1&sspagename=STRK%3AMEWA%3AIT&rd=1

Rick

[Deang]

If you hook a multimeter to a solder joint and wiggle the wire(s), it will tell you if the joint is good or bad. I still see it as the best way to get a gasless connection. It's a moot point in some ways. For example, what is the point in worrying about which method is used when we use disconnects or a piece of buss wire under the screws on the barrier strip for all the connections back to common? I've recently chosen to use disconnects on the autoformer, and I've certainly built my share of networks using the wire around the screws approach -- in fact my personal networks are built that way. I worry about it less on a network that sits outside of the speaker and isn't being subjected to mechanical vibration. I do stress a bit over the network's exposure to dust/dirt and changes in temp and humidity over time. I guess the most important thing is that the connection points are clean and you get as much positive contact as possible.

If one enjoys soldering like I do, there isn't any better experience to rob the joy like trying to solder on those GE lugs. I like to get in and out as fast as possible but those things won't let you unless you go straight for the 140 watter. The problem here is that there isn't any practical way to heat sink the things, and you have to worry about damaging the film. Maybe that oil is good thing under those conditions -- I hadn't thought of that before.

[JJkizak]

The old telephone company (ATT< Bell Labs Western Electric) went to the wrap crimp type connection because it was fast and it put about 6 really tight forcefull wraps per connection. The connector pins had 4 sharp edges which literally penetrated the wrapped wire, so your connection would have approximately 24 penetrations on one connection to ensure proper connection without solder.

The old crossovers I had from Klipsch (1965) had all of the measured values of the caps hand printed on each cap. For instance: a 2.0 mfd cap would have 1.76 mfd written on it.

JJK

[ricktate]

Why not buy the caps from Bob he has them and you will get the brackets ready to go...he is very helpfull to... plus you would help a forum member ....just a thought...what has Granger done for you for free? Rick

[John Pearlman]

I really would buy the caps from Bob but I kind of have my heart set on one 12.5 cap instead of a 10 and a 3. I also do really appreciate the help Bob, I'm glad that there are people on these boards willing to give up their time to help. As for Grainger, I've done a lot of business with them and I'll be getting the caps on sale well below cost.

Thanks

John