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Altec 902-8T measuring question

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Posted on January 10, 2021 at 10:05:08
Rico_111
Audiophile

Posts: 3
Joined: January 10, 2021



Hi,
I've got two Altec 902-8T drivers but I'm a bit worried about the DC measurements.
One driver measures 7.6 Ohm and the other one 8.7
I measured it on the terminals in the clamps.
I'm a bit worried about the large difference and also I feel the values are quite high. Can someone advice on this perhaps. Many thanks!

 

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RE: Altec 902-8T measuring question, posted on January 10, 2021 at 10:14:22
Bill Fitzmaurice
Industry Professional

Posts: 5071
Location: New England
Joined: October 20, 2002
Those values are high for a woofer, but not for a compression driver. Impedance matters more than DCR, that's what I'd be measuring with Dayton Audio DATS.

 

RE: Altec 902-8T measuring question, posted on January 10, 2021 at 11:33:23
Rico_111
Audiophile

Posts: 3
Joined: January 10, 2021
Thanks for your reply Bill.
Should I worry about the difference measured at all? I saw other Altec compression drivers online that had lower DCR measurements hence my worry.

 

RE: Altec 902-8T measuring question, posted on January 10, 2021 at 11:45:49
Bill Fitzmaurice
Industry Professional

Posts: 5071
Location: New England
Joined: October 20, 2002
The difference in DCR is probably due to the drivers being from different production batches perhaps years apart, or one or both could have replacement voice coils/diaphragms. Their sensitivity won't be exactly the same, but it's not like you'd be mixing 8 ohm and 16 ohm drivers. Other factors that will have much more effect, like Fs and Le, you can only see on am impedance sweep.

 

RE: Altec 902-8T measuring question, posted on February 5, 2021 at 10:08:16
Volker
Audiophile

Posts: 21
Joined: May 23, 2001
Check for corrosion of the cable connector screw contacts and the push on connectors at the diaphragm, i have seen the same dissimilarity on a pair. After cleaning, dc resistance got similiar.

 

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