Can you recommend a wattage for an all purpose soldering iron?

i cant really answer your question. but this is what i use. its a 25w iron. seems to work fine

http://www.amazon.com/gp/product/B000B63BTU/ref=oh_details_o08_s01_i01

I use a 75w gun. Lower wattages take longer to heat the joint, and that can cause component damage. A higher wattage gun doesn't heat the joint any hotter, it just does it faster, minimizing long term heat build up within the component.

Personally, I like higher wattage irons. Quality joints can be made more quickly without "soaking" component leads. Longer application lets heat creep further up the leads, melting plastic etc.


Edit: Bill beat me to it....

If you're going to use a Ratshack iron, then get the highest wattage and use that tip tinner/cleaner compound stuff:
http://www.radioshack.com/product/index.jsp?productId=2062721

The tips on those irons wear out extremely fast, but the tinner will help scrape off the corrosion that builds up and tins the tip well enough to do soldering work.

Have you ever considered a wireless solder iron?

Heat output is adjustable based on flame setting. I use this one but probably picked it up at Radio Shack many years ago. Never looked back. I have a can of butane around and just add some when I start a new project.

http://www.amazon.com/Iso-Tip-7971-SolderPro-Butane-Soldering/dp/B001RIDT84/ref=sr_1_16?ie=UTF8&qid=1356136869&sr=8-16&keywords=butane+soldering+kit

I've used 30w pens and 100/150w guns. The big gun is great if you have to solder multiple 12ga wires coming together on components. For <16ga and crossover components, the 30w treats me fine. Alligator clips or other small metal clips can help wick heat away from leads prior to reaching the component.

I bought and used this one on the 4Pi's crossover. It did the trick and got surprisingly hot for a cheap iron.

http://dx.com/p/30w-electronics-diy-soldering-iron-110v-ac-22264

Then bought these tips and switched to the flat "half-circle" type end. It works much better at transferring heat then a regular pen type end. (more surface area)

http://dx.com/p/30w-lead-free-soldering-iron-tips-4-tip-set-23445

Solder

http://dx.com/p/1mm-1-meter-rosin-core-solder-3-pack-1692

For those unfamiliar with Deal Extreme. It's a cheap website from Hong Kong that sells supplies and random things for literally everything you can think of. Shipping is free anywhere in the world, for everything on the website.
Be warned shipping may take a 2-8 weeks if do use the free shipping (expedited is also available), and some of the stuff is notoriously crappy.
It's great for picking up those nick-nacks you aren't in a rush to get, especially for us DIY guys.

But to answer your question OP, 30w would be fine, and like Sibuna posted, the 25w Weller iron will work good as well, seeing as they are a great brand.
I wouldn't dip below 30w though, no point in using a weaker iron for crossovers, they aren't very complicated to solder.
Edited by Thatsnasty - 12/22/12 at 12:46am

If you want clean reliable solder joints you need to get a quality iron at some point. If it is just for one project than the radio shack iron will probably work, but if you find your self using it more than once you will want a good iron that provides stable high heat for quality joints.

I have used quite a few irons over the years and this is by far my favorite for the price, if you want a recommendation.

http://www.amazon.com/Hakko-FX888-FX-888-Soldering-Station/dp/B004M3U0VU/ref=sr_1_1?ie=UTF8&qid=1359160665&sr=8-1&keywords=hakko\

hakkos work thats what i use for every thing for years.

I have the Radio Shack one with digital, adjustable temp and readout, I think it was the best one they had at the time I bought it. I was hesistant/skeptical as the quality of RS stuff can be dubious but it has acutally been a rreally good unit. And it's easy to adjust to just the right temp, such as if you are using lead free solder and need a bit hotter. Also the tiip senses the temp and gives it more juice when needed.

Note: I was curious to see if they still offered this and they offer two different ones now fitting the description, mine is the black one.

Circuit Specialists sells decent irons at reasonable prices. They're pretty well known in DIY circles; you can google to find out more.

They're a good compromise between a cheap iron and a Hakko.

Tim