[ellisonb]

I'm in the middle of redoing a pair of DCM Time Window xovers. I'm fairly ignorant, but I'm pretty good with a soldering iron and know just enough to be dangerous. I'm replacing the resistors and caps but reusing the inductors. I cut a larger pressboard base to accommodate the larger new parts and am duplicating to original wiring with new terminal strips on the new board.

My question is: when I re-solder the inductor wires to the point on terminal strip where it joins other parts, do I need to sand off the enamel coating on the end of the bare inductor wire? It would seem that soldering an insulated wire would provide no connectivity.

I was never able to see the ends of the inductor wire on the original connection, due to the amount of solder they needed to join the 4 parts together at one point. Thanks in advance!!

[marc513]

I would say yes scrape it or sand off the the end of the inductor.

[S Clark]

Absolutely yes.  Unless you are soldering tiny wire, think tweeter voice coil leads, the varnish won't burn off and you'll get a bad connection. 

[GeorgeAb]

What marc and S said. I usually use a knife to scrape off the insulation from the inductor ends. You are on the right path and it sounds like a worthwhile and fun project.

[ellisonb]

Thanks so much, guys! That's kinda what I figured. The project is a true pain but I am hoping the end result will be worth it. I have loved these for over 40 years and think the replacement parts could make them even better. You can see the inductor locations marked by the paper squares in this old/new shot.

[richidoo]

And if you ever need to repair broken or scraped insulation on magnet wire, the guys at anticable recommended clear nail polish and it worked well.

[kd4ylq]

A teacher of mine once said "there are no stupid questions" and I agree. I just learned about using clear nail polish on magnet wire and I wasn't even thinking about that (thanks!). I gave an old pair of DCM Time Windows to my son a few years ago and am now thinking I should refurbish them (he has become very attached to them). Can you please list the replacement parts w/ vendor & part numbers? or post the schematic or xover parts list? also, do you think you will be replacing the drivers as well? Good luck and keep us posted on your results in this project!

[Early B.]

Replace the inductors. You've gone this far, so why not? 

[FullRangeMan]

Goertz Ribbon air core would be nice, but inductors last a century.

[Tyson]

IMO Jantzen or Mundorf are the top of the line for inductors re: sound quality.  Upgrading inductors makes a surprising amount of difference to the sound.  Splurge a little and get the foil inductors, particularly for the midrange/tweeter spots. 

[ellisonb]

I really never seriously considered replacing the inductors. First, because I'm scared. But mostly because I didn't want to change the character of the Time Windows. I know swapping out caps and resistors will do that to an extent, but I see that as more letting the speaker clear its throat and reach potential. Like I said, I'm fairly ignorant so I could be way off...

[ellisonb]

kd4ylq -- I am attaching the schematic for the Time Window 1 and 1A speakers. I will dig up the parts info and post that too.
A WORD OF CAUTION:  DCM changed internal configurations without immediately changing model numbers. I have a pair of Time Window 1's, but when I opened them up I found they had 1A crossovers. My advice is don't order parts until you get them open and see what you need.

Getting them open may be the hardest part of the job. My drivers were screwed and glued with the infamous black tar. I can give you more on opening them, but there's a great thread on the Polk Audio site with a ton of pictures from a guy who did his.

[Early B.]

I really never seriously considered replacing the inductors. First, because I'm scared. But mostly because I didn't want to change the character of the Time Windows. I know swapping out caps and resistors will do that to an extent, but I see that as more letting the speaker clear its throat and reach potential. Like I said, I'm fairly ignorant so I could be way off...

Nah, you won't change the character. Look at it like this -- you're building the character of the speaker with better crossover parts.

[GeorgeAb]

IMO, those inductors look fine to me. They look like air core just wound around a plastic bin. If they were wound around an iron, I'd consider replacing, but yours look fine. On the schematic he called out the Q (efficiency) and DC resistance of the inductor which is another reason to stick with the inductors you have as there may be a reason he called out those specifications.

[ellisonb]

George - Funny you should mention that. The larger of the three inductors had a metal core that just slipped out of the plastic bin. My original picture shows it with the core out. Here's the large inductor with the core in and secured with electrical silicone. Do you agree with EarlyB that I should consider replacing that one? It's now or never cause I don't want to go back into these speakers again.

[FullRangeMan]

Nah, you won't change the character. Look at it like this -- you're building the character of the speaker with better crossover parts.

With this new xover parts the sound will change.
On the original inductors in that plastic reel they will resonate on the plastic spool, the best inductors are the ribbon air cores, but they are expensives.

[Tyson]

George - Funny you should mention that. The larger of the three inductors had a metal core that just slipped out of the plastic bin. My original picture shows it with the core out. Here's the large inductor with the core in and secured with electrical silicone. Do you agree with EarlyB that I should consider replacing that one? It's now or never cause I don't want to go back into these speakers again.

Yes, without the metal core it's not functioning properly. Inductance will be too low without it.

[Early B.]

... but inductors last a century.

...unless they're low quality.
 

[ellisonb]

OK guys - I've been considering the several recommendations to replace the inductors. Not to get too deep in the woods, I did some initial research and found this on a reputable electronics site: "Application wise, Inductors with a high value of Q factor are used in the RF circuits where a capacitor is used in parallel with it to form a resonant tank circuit. In such a case, the high value of the Q factor of an inductor helps to balance the upper and lower frequency of the resonant circuit operating in a continuous band frequency."

Now my large inductor seems to have a Q value of 1.0, based on the above schematics I was able to find online. All the foil inductors I see are, at best, half that amount and most far less. If the above quote is true, changing to a new foil unit would seem to represent a pretty radical change in the voice of the speaker. Thoughts?

[FullRangeMan]

The best inductors for audio are ribbon air core(no reel-bobbin), the worst are the ones with spool and cores that also are the cheapest.