DCM Timeframe

I horsetraded for a pair of TF 600s. They actually sound good when you locate them right. The problem I have is with the x-overs in them. I would like to substitute some good components for the crap that's there, but DCM won't tell me what the values are. Does anybody have any info on these, or any idea how I can test for the values. Thanks
 

kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
What kind of equipment do you have?

I 'll do a search later for you to locate programs to measure inductance, resistance and capacitance.

Meanwhile, you will need a precison audio generator. Here is a nice one off the net for free. You can either go up or down to preselected frequencies, or highlight the frequency box and write in your own frequency of choice. I save mine to Program Files so I can have it any time I want. Don't forget to set the selector to sine wave for testing-you have your choice of several waveforms.

http://www.nch.com.au/action/index.html#TONE

This tone generator, a hookup from your sound card to your stereo, a resistor and a cheap voltmeter will probably be all you need to measure the components of your crossover. I'll search for a free program so you might not even need the voltmeter.
 

kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
AudioFreak:

The issue of DC resistance in the inductor is something that might affect things. On the one hand, all other things being equal, a higher quality inductor will have less DC resistance than a cheaper one.

On the other hand, air core inductors are likely to be superior to iron core ones. However, at lower crossovers, air core inductors are going to have higher DC resistance.

In instances where his new inductors have less DC resistance than his stock ones, he can always add resistance in series to make up for it. If he switches to air cores inductors with slightly higher DC resistance, there is not much he can do if it affects the sound for the worse except to put the stock unit back in.

We don't really know that DCM has programmed in the DC values of it's components when making the crossovers either.

One thing is for sure-if he can replace an electrolytic capacitor with a poly capacitor, there is no way he can go wrong!

About the only thing I can suggest is that if he gets his crossover components from a high quality supplier such as Madisound, www.madisound.com , then he should go for the air cores if it is within his budget. Madisound is unlikely to stock something that they have reason to believe will make the crossover sound worse. Iron cores do introduce distortion, but they are cheaper per henry than air cores.

Incidentally, although I have had experience designing crossovers from scratch, I have not replaced the crossovers of existing units before. I am just applying some "rules of thumb" to the issue here. Anyone who has done modifications of this type, feel free to jump right in.
 

kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
Well, I wish I had either a freeware program or a spreadsheet to measure these values. But the two methods here are not too bad.

What I like about the inductance measuring method is that it takes the DC resistance for the inductor into account. And the formula is not difficult. You can put your Windows calculator on "scientific mode" if you don't have a hand held job.

For measuring capacitance, DC resistance is not a factor, so we ignore it. Use your signal generator instead of the wall outlet for a signal source. Use a low frequency-say 50 or 60 Hz for capacitance measurements.

Here are the links to the information on how to measure inductance and capacitance:

http://et.nmsu.edu/~etti/fall96/electronics/induct/induct.html for inductance.

http://www.pupman.com/listarchives/1998/April/msg00625.html for capacitance.
I suggest using either method (5) or (6). Use the signal generator at 60 Hz or so instead of the wall outlet.
 

kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
PassFan:

Actually, I have recommended Audua to others for finding the Thiele Small parameters of individual speakers. I did not know it did individual components.

The reason I did not know this is that for some reason I cannot get this program running right on my computer, even though I have heard it praised to the skies by other members on this forum.

Now that I have yet another testimonial, perhaps I will delete it and download it afresh, to give it another try.