DIY Crossover Upgrades

[Deang]

I've been getting more and more email on this -- so here's how to do it (at least, how I do it). There will be at least a half dozen posts, with plenty of pictures and text, so it would be great if you held off on roasting me until I'm done.

This is being done to a pair of KLF-30 networks I just received. These are similiar to the Forte II, Chorus II, and some of the KG's. I don't know if the original Forte and Chorus are on PCB or breadboards with point-to-point, or maybe even a PCB simply screwed to inside of the speaker. Still, these instructions should work well enough for all of them -- just let common sense prevail.

1) Start by removing the the tweeter horn/driver and disconnect the leads. Use a piece of tape to mark the positive side of the driver (the side you remove the colored wire from). Sit the horn and screws down in a safe place. That bit of tape can save some aggravation if you can't find or see the factory mark showing where positive is.

2) Go the rear of the speaker and remove the screws to the terminal cup. Once removed, you'll see the network attached to the back of terminal cup. Reach in the hole and disconnect the wires from the midrange driver (again, note which side is positive, and put a piece of tape on the positve side). Next, disconnect the woofer (tape again). Remove the whole network assembly with the terminal cups and wiring.

3) Put a pad of some sort under the network to stop the faceplate from getting scratched up, and remove the screws holding the board to the terminal cup. Pull the board gently forward, and then remove the screws to the autotransformer.

4) Roll up and tie strap the wiring to keep the wiring out of your way while you work.

[Deang]

5) Time to cover the tools.

You'll need a 25 or 35 watt soldering iron for the majority of the work. If you are going to replace the wiring, you'll also need a 75 watt soldering gun as well. Not enough heat is almost worse than too much heat. Things should heat up quickly so you can get in and get out. IF you don't know how to solder, make use of the online tutorials on the net, and practice. I buy just about everything from www.partsexpress.com.

Soldering tool kit

WBT solder

Desoldering braid (Prowick)

Small wire cutters

Small needle nosed pliers

Hot melt gun and glue (at least two sticks)

#6, 3/4" pan head sheet metal screws

Spacers (I use 3/4 M faucet washers

6) Time to flip the board. You will need to turn the board with the leads attached autotransformer at the same time. Work slowly and deliberately. You can also disconnect the leads from the binding posts if you want. I prefer just to leave it attached.

7) The board and autotransformer will be flipped back and forth several times while you're working. So, once I get the board turned over, I bolt the autotransformer to the board. I use an old set of DQ-10 binding posts, in case you were wondering what you were looking at.

So, here it is. Lovely. I think dried up flux looks nasty. It's non-corrosive, doesn't hurt anything, and some even claim it's best to leave it -- but I prefer to remove it all.

[Deang]

8) Desoldering braid. I love this stuff. It's not always easy to work with, but it's the only way I know of to get all of the old solder off. Again, a little practice helps. What works best for me is to lay about 1/2 of the width of the braid on the joint, and put the iron on the exposed part of the solder. When the solder begins to melt, slide the tip of the iron onto the braid, and slowly pull the braid across the joint from underneath the iron (slowly pull and drag). Put some pressure on the tip and work it. This not the only way to remove solder -- it's just the way I prefer to do it.

9) There is always a little bit of solder left holding the lead to the board. Retrieve the tool from your kit with the flat surface, go back, reheat the lead, and separate the lead from the board.

[Deang]

10) Turn the board back over. Whenever you do this, do it slowly. Take the needle nosed pliers, position them where the lead makes contact with the board, grab, and slowly twist. If the lead is still attached by some solder, the lead won't slip right out of the hole. Turn the board back over, reheat, and wiggle the lead with the pliers -- go back and pull it out.

Again. There are different ways of doing this. If you're coordinated, you can start step #8 by turning the whole assembly on it's side, putting the pliers on the lead on one side, heating the joint on the other, and then twisting the lead out. Do all of the leads, and then go back with the braid and suck all of the solder off. The main reason I don't do it this way is because once the solder is heated to pull the leads out, it takes longer to reheat and melt the solder with the braid (this is one of the natures of solder). Early on, I had some foil lift off the board because of the excessive heat I had to use to get the solder off. So, I just avoid this potential problem by doing it the hard way.

[Deang]

Another pic. Notice the 6uF cap has already been "removed". Actually, it fell off the board when I pulled the leads out. I see a lot of this, where the glue is no longer doing it's job, and the part is just held on by the leads.

[popbumper]

Dean:

If I may add here:

1) Save yourself some burned fingers and non-reuseable braid; buy yourself a solder sucker. Radio Shack makes a good one; it is basically a hollow tube with a spring and plunger; you depress the plunger, put the tip on the heated solder joint, hit the release button, and the sucker pulls the melted solder out of the solder joint. This is an absolute necessity for electronics rework. If anyone needs one of these, let me know. Dean, I will send you one if you are interested.

2) To address Dean's question - the Forte crossover is on a PCB which is attached behind the binding post cup.

3) The "universal crossover" is going to be designed for application in MOST speakers, since there is a lot of linearity in the filter construction. As Dean said, the hardest work is the UP FRONT work, trying to figure out how everything fits.

As Klipsch generally "formatted" their speakers so that the crossover was attached in a specific area (Academy - cabinet bottom, Forte - behind cup, Cornwall - cabinet side), this new crossover will most likely be designed "generic", in that it can be placed anywhere in the cabinet. I would LIKE to design "speaker specific" applications, but then the "universality" of the crossover would be challenged.

I should have the remainder of my parts in this week; I have autotransformers coming in from Bob Crites, and a few remaining components on the way. Once recieved, the daunting task of developing a physical format takes place.

Hey Dean, many thanks for what you do here in general - it is a great service to the Klipsch community. Hope I can help you in some way.

Popbumper

[Deang]

Hi Chris -- I've tried several "suckers". I can never get it all off with the first try, and with every "try", the more heat it takes to melt the solder again. Maybe the contraptions are just too complicated for me.

O.K., where were we?

11) Remove the old glue. Be VERY careful while you're doing this. Imagine slipping and running your tool into the side of an inductor. Use something as flat and skinny as you can find. I use the tool from the soldering kit shown earlier. I also cheat, and use a heat gun to soften the glue a little while I'm sliding the tool under the glue -- you can use a hair dryer. This is PITA. Take your time.

[Tom Mobley]

Dean, did you get my PM/email?

[Deang]

O.K., finally done with the glue. Get off as much as you can, then go over the areas with Q-tips and denatured alcohol. The alcohol will break up most of the remaining glue.

12) Now you need a power drill and a 1/16" drill bit. The more RPMs you can generate the better. I wouldn't use a cordless unless you have an 18 volt type. You want to expand the holes ever so slightly to accomodate the thicker leads of the Auricaps. Hit the hole with the drill already spinning at high speed -- and let the drill do the work. Do not push hard through the hole. If you don't do this part right, you'll have a nice strip of foil from the bottom of the board wrapped around your drill bit.

EDIT on 28July05: The drill is overkill. Someone suggested a small tipped file -- which I've found works much better.

13) Notice the caps sitting on the sheet of sandpaper. I scuff all surfaces on the caps where they will be "sticking" to the board, and to other caps. Hot melt is great stuff, but doesn't have the best of adhesion properties -- unless you scuff first. Without scuffing, you can pull a cap off the board with your hand. With scuffing, you will need pliers, and the surface of the cap in contact with the board will literally rip apart as you pull it off. Big difference. OTOH, now that I'm practically potting the parts, it's probably not as big of a deal as it used to be.

[Deang]

14) Time to clean. Use denatured alcohol and Q-tips. When you're satisifed with what you've removed -- use a cotton cloth wet with alcohol, and wipe down. Finish by finding a dry part of the cloth and buff. Add this to the PITA list.

[Deang]

Time for a small break to talk about the parts.

By looking at the earlier pictures, you can see the limitations the board puts on you. Thankfully, I've convinced myself that iron core inductors on the woofer section are not an issue from a performance perspective. I would prefer to put a nice air core in there for the midrange -- but where and how? There just isn't any way to do it without major modding (all caps moved to the bottom of the board, long spacers, drilling out the posts and using longer screws, drilling holes into the board for tie straps, etc.). That one part involves a lot of extra work. So, now I'm looking at things from a cost/performance perspective. I charge a little over $200 to do this work, which includes the parts, the labor, and return shipping. Swapping that inductor would almost double the time I spend on a set of boards -- and I just don't want to!! Oh, I would do it if someone really wanted me too, but it ain't going to be for $200.

The picture shows the stock 6uF cap hooked up to my cap meter. The two 6uF Auricaps have already been measured, and I marked each cap with it's actual value. I buy in bulk now, and Al talked me into matching them all up.

[Deang]

The 2uF capacitors.

[popbumper]

Dean:

Do you use a dedicated capacitance meter, or a hybrid?

Popbumper

[Deang]

15) I use WAY more hot melt that I have too. Somehow, I've gotten addicted to the stuff. It's almost like a disease.

You can mount stuff anyway you want, just make sure it doesn't move when you're done. Work out the placement issues before you glue. I use the hot melt in stages. First, just to put the parts in place. After the glue sets (a few minutes), I go back and solder. When initially putting down the glue, don't get carried away. Make sure it doesn't run over the holes you have to push the leads through. You also need to be aware that any glue around the hole will melt and be sucked through by the heat and mix with the solder you're melting. Bad.

[Deang]

Hi Tom -- yes, got the email. I'll pound out a response when I'm done here.

Chris -- I have both. What I really want is a nice LCR meter like what Bob uses. Al has turned me on to some nice ones on eBay, but I'm always broke when I get his emails!

16) O.K. now you solder.

[Deang]

Oops, forgot the pic. See, you guys messed me up.

[Deang]

17) Go back and fill in some of the "empty spaces" with the hot melt -- or go bonzo like I do.

This one qualifies as being damn near fully potted. I build it up in layers. Took about 45 minutes.

The 6uF cap is ready for installation. It's not going "on" the board, so I wrapped it with cold shrink tape for the first layer of damping.

[Deang]

18) This cap is going to be tucked into the space between the terminal cup and the board. So, I solder it this way.

[Deang]

19) I use whatever I have laying around to cushion the cap. It's usually speaker damping material. Hmmm -- a foam peanut or two might work good too. You have to work with it to get the spacing right. You want it snug so it doesn't move, but not so snug that there is undue pressure on top of the cap, or the board above it.

[Deang]

Add finishing up to the PITA list. Situating the cap properly, and getting the spacers and screws in takes some patience. I don't recommend using the original screws. They are too short, and when you try to snug them down they usually strip out the insides of the posts. Use 3/4" #8 panheads, and don't bear down when tightening. Go slow as you turn the screws in, because the posts are kind of fragile. When you get the top of the screws down to the board -- just gently snug them.