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I'm no expert, but I have soldered Kimber hook-up to Cardas copper posts recently. The one thing is, it takes a bit of time to get the post hot enough to melt the silver solder. Put the tip on the post and the wire and leave it there. I keep touching the solder to the post and the wire cause that helps to conduct the heat to the post. Once I see that the solder will melt on the post only, I go for it. I don't know what that sideways hole is for. I wanted the wires to come straight out of the post, so I didn't use it. One other thing....Cardas and some other wire, I assume, has a coating on it that must be removed before solder will stick to it. Otherwise the big thing is getting the post hot enough. If cardas solder is like Wunder solder, the flux is in it.
For those of you who may not know yet, brass is a relatively poor conductor. (Btw, do not use the brass jumpers if you are not bi-wiring, instead pull off the binding post cup and solder the wires to a single pair of BPs per speaker.) Spring for solid copper BPs with Rhodium or gold plating (not fake copper ones from Ebay) and make sure your spades are plated solid copper too. Rhodium is more durable, so I went with those because I figured I would be using these the rest of my life when switching between speakers over the years, keep the original hardware. (The same reason I sprung for the Furutech FP-201 spades in rhodium for my speaker cables)
I have 10 pairs of Cardas BPs and I originally had inserted the hookup wire into the BP’s cavity and filled it up with solder using a 60 watt iron. (Took lots of solder!) Sound was improved and I thought that it was the highest possible fidelity from my system. However, as time went by and I upgraded my system time and time again, I realized that solder is bad for sound because it is a poor conductor, excepting the silver, and there really is not all that much silver in the solder.
So I clipped off the hookup wires, got a Weller professional 300 watt gun, drilled holes in two pieces of oak scrap to clamp the BP in while I hit it with the Weller. The "old" solder poured out onto the tile floor.
I spoke to Cardas and this is how they told me to do it:
Using that same high wattage gun it was time to do this the right way:
Use some flux in the front portion of the BP’s hollow "tube" where there is more of a trough.
Tin the hookup wire and lay it in the trough.
Heat the assembly, then feed Cardas solder up through the little hole at the bottom of the trough. Use just enough solder to secure the hookup wire. Hold the hookup wire perfectly still. I
High watt solder gun heated the BPs so quickly that it was amazing how I could finish a solder even before the other end of the BP became all that hot.
Sound improvement was far beyond what I had expected!
"Solder should never be used to glue things together. The connection should be made physically sound first."
How do I make a solid connection to a Cardas binding post without using solder as the glue. It cannot be done because there are no set screws on a Cardas binding post.
This is why I do not like to post online because someone always comes along and thinks that I did it wrong. Do you think you know more than Sonic Craft and Cardas?
I have a high wattage iron I use mainly for Cardas binding posts. I think it is 80 watts but don't recall exactly. After the iron is fully heated up, I place the tip firmly against the outside of the post while the wire I intend to attach to it is resting in the opening of the post. (The wire is tinned in advance.). After 5 seconds or so, the interior of the post is hot enough that I can apply Cardas solder to the interior of the opening and it flows quickly and smoothly over the wire and along its sides where it is touching the post. I only use enough solder to coat the wire and have it join smoothly to the post. Then I quickly place the flat tip of a screwdriver on the wire and press it firmly against the wire and post while the solder cools. To be on the safe side, I leave the screwdriver there for 10 or 15 seconds until I am sure the joint is secure. The keys are to make sure there is a good mechanical connection, use enough heat, make sure the joint is fully heated up before solder is applied, and don't let anything move before the solder cools. Works every time.
"Use PLENTY of HEAT - we use TWO 35W soldering irons when soldering binding posts - and +1 to the comment above - there should first be a very solid electrical connection then apply solder to make it stick."
As I mentioned in my initial post per Cardas, I now use a 300 watt soldering iron with some flux paste in the binding post where the wire will lay. I can assure you that it is a night and day difference in both how the solder acts and it also results in a higher fidelity sound. I believe that this is why readers should not jump to a conclusion right away that results in them simply parroting what they have read before in other posts.
UPDATE: Sonic Craft has recently told me that they always loop the hookup wire through the little hole in the tip of the Cardas binding post before soldering. So, I apologize to those whom I disparaged.
However, Sonic Craft still commands that a 250 watt+ soldering iron be used. I can verify that the post heats up so quickly with that wattage iron that within a matter of perhaps 30 seconds the solder literally flows even more quickly than water. Just use enough to hold the connection. Do not fill up the tube with solder as I think it deadens the sound and I know for certain that doing so wastes a ton of solder. Additionally, I would say after having filled up 18 Cardas binding posts with solder (7.2 system with passive subwoofers) while using a 60 watt iron, installing them all to the speakers, then uninstalling them, heating the posts, dumping the solder, and then re-soldering using a 250 watt iron after laying down some extra flux and just enough solder to solidly hold the connection, that the improvement in sound quality is amazing.
Don’t forget to prepare the mating surface of the binding post before soldering by lightly sanding or wire-brushing. This, as well as a modest amount of rosin flux (never use acid flux) will ensure the solder “wets” correctly. This provides as close to a molecular bond as possible. And yes, wrap the wire firmly around the post, or double fold it over if inserting in a tube before soldering. This will give you the required mechanical integrity that is necessary for long term reliability. A good soldering iron or station with the correct (1/8” or larger) tip should be sufficient to heat the post and wire. My preference is the Weller WTCPS or WESD50.
There are so many images of improperly soldered Cardas binding posts on the internet that I decided to change my profile image to that of a somewhat correctly soldered Cardas binding post. I say "somewhat" because when I have the time I am going to redo mine by first looping the wire through the little hole and then soldering. I did not do this initially because I needed to be able to remove the nut, however, now I do not because I switched to Cardas mounting plates that mount over small cutouts in the back of my speaker cabinets.
This solder was done with a Weller 300/200, Cardas solder and extra flux. The solder will flow like water when heated with an iron having the correct wattage. A 60 watt iron ill heat the Cardas binding post sufficiently to melt the solder and make the connection. However, it will be a cold solder and will not sound as good as a wet solder. I know this from experience.
Hi Craig: I see that you’re still trying to improve your workmanship for soldering wire to a binding posts. Your plan to loop the wire into the binding post hole and then solder is a good one.
A couple things. From what I can see from the picture you show, this soldering job would not pass industry standards (IPC). The wetting angle is not correct and there is no strain relief to the solder joint.
The difficulty, as you know, with soldering anything to a binding post is to get it hot enough. Your choice of solders exacerbates the problem. I would use Sn63/Pb37 alloy which melts at 183C instead of something like SAC 305 which melts at 217C. That way, you don’t have to get the binding post so hot. All electronics prior to 2006 (RoHS) where fabricated with Sn/Pb solder. There is no difference in SQ.
As for technique, you should coat the wire and post with rosin flux prior. Then hold your iron up against the outside of the binding post by the hole the wire is looped thru. Feed your solder to the inside of the binding post at the post/ wire interface. When done, the solder joint should have a smooth fillet (proper wetting) and not be a big blob.
The IPC solder standards are not in the public domain but there are some boot legged copies on the web.
The Cardas hole makes it tricky. It does not take much solder and you need to see the strands of wire that have been tinned in a small trough of solder. I've done it 2 ways,take off binding post copper nuts, put drop of solder in front of hole and another small drop across hole towards the cavity. I've done it between 700 and 850 degrees. Soon as solder starts to melt hit the tinned wire for split second then then put it all together fast. Other way is to clip off or cut(Dremel) the hole and your left with cavity with easy access. When you melt solder is more a timed thing than a visual thing. Can't see solder it just disappears and bubble gums. If you can slide washer on wire it can also give access to more metal to heat up, I never did it that way.