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Old 17th April 2008, 08:12 PM   #1
trummis is offline trummis  Sweden
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Default Xover Coil R/Ohm Question

I am about to upgrade my Xover for my Scanspeak 9700 and 8545.
The current coil for the tweeter has Rdc=0.32. I want to go all the way, Mundorf CFC 12, with a Rdc=0,07.
Now, am I barking up the wrong tree here? Is this a major concern or a minor problem? If it´s a problem, please enlighten me!

Thank you very much
Roger
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Old 17th April 2008, 08:48 PM   #2
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Looks like the Mundorf has less resistance. Maybe by design it offers less DC resistance, which is good.

Are you checking the inductor value also, that is, the Henries? For example, 1.3 mH or .5 mH or other value from the original coil.

Determining the old coil value may require a meter, if it is not marked.

Vince
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Old 17th April 2008, 09:36 PM   #3
Svante is offline Svante  Sweden
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I would advice to get a coil with the same resistance and inductance as the original coil. Using a lower resistance might actually spoil the response of the speaker.

Then again, I would advice not to change it at all, if it has the same L and R, nothing will change.

... or if I suspected that there is potential for improvement in a given design, I would do some measurements to confirm that, before I did the change. I would not just change components blindly to something "better".
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Old 17th April 2008, 09:51 PM   #4
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You are talking about 0.25 of an ohm. Depending on how the coil is used for the tweeter (parallel notch, impedance compensation etc...) maybe 0.5 ohm or more might affect the response, but I doubt you could audibly tell the difference of 0.2ohms.

You also need to look at tolerance of components esp. around inductance values. your current inductor might be +/- 5% or more so keeping within the tolerance inductance is safe.

David.
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Old 18th April 2008, 01:04 AM   #5
bjorno is offline bjorno  Sweden
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Quote:
I would advice to get a coil with the same resistance and inductance as the original coil. Using a lower resistance might actually spoil the response of the speaker...
Then again, I would advice not to change it at all, if it has the same L and R, nothing will change
... or if I suspected that there is potential for improvement in a given design, I would do some measurements to confirm that, before I did the change. I would not just change components blindly to something "better".
Agree.

Quote:
...You also need to look at tolerance of components esp. around inductance values. your current inductor might be +/- 5% or more so keeping within the tolerance inductance is safe...
Agree again.

See an example: 1(1)

b

1(1)
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Old 18th April 2008, 12:28 PM   #6
sreten is offline sreten  United Kingdom
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Default Re: Xover Coil R/Ohm Question

Quote:
Originally posted by trummis

The current coil for the tweeter has Rdc=0.32.
I want to go all the way, Mundorf CFC 12, with a Rdc=0,07.
Now, am I barking up the wrong tree here?

Roger
Hi,

The short answer is yes you are.

It is fairly pointless "upgrading" a tweeter inductor if there is nothing
wrong with the original. Lower DCR will likely do nothing useful.

/sreten.
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Old 18th April 2008, 02:35 PM   #7
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Please post the xover for that driver (before/after). If you can, post the xover complete with drivers you use for a better understanding of what is at stake here.
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