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Topic: 5.6 ohms? |
George McLellan
From:
Duluth, MN USA
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Posted 3 Mar 2011 4:40 pm |
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I have a 15 inch eminance speaker. Nothing I could find on it that would tell me what the ohms are so I put my meter on it and it shows 5.6 ohms.
Is it safe to use this with my amp that calls for an 8 ohm extension speaker?
Thanks,
Geo |
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Len Amaral
From:
Rehoboth,MA 02769
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Posted 3 Mar 2011 5:13 pm
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| Your speaker is probably an 8 ohm speaker as an ohm meter will show less than 8 ohms. A 4 ohm speaker will show 3 point something and a 16 ohm speaker will show less also. |
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Greg Cutshaw
From:
Corry, PA, USA
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Posted 3 Mar 2011 5:49 pm
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Roughly, you can see from the chart below that adding 20% to the ohmmeter reading will yield the rated impedance of the speaker.
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Randy Wade
From:
Batesville, Arkansas, USA
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Posted 3 Mar 2011 8:48 pm
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| The difference is because the ohm meter measures DC resistance but the speaker is rated in ohms of impedance (AC). Audio is AC so speakers must be rated in impedance instead of resistance, but the common ohmmeter just shows DC resistance. |
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George McLellan
From:
Duluth, MN USA
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Posted 4 Mar 2011 2:35 am
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My thanks for all of your input. I connected the speaker to the "exteranl speaker" jac of my Cube 80 and it sounded very good. I will try that set up this weekend.
Geo |
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Dave Grafe
From:
Hudson River Valley NY
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Posted 4 Mar 2011 6:57 pm
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| Nice chart, Greg, where did you find that? |
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Greg Cutshaw
From:
Corry, PA, USA
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Posted 4 Mar 2011 7:30 pm
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Dave,
I have a ton of speaker design books full of rules of thumb, equations and charts and graphs. Mostly interesting but pretty worthless compared to cut and try methods. That one chart however stuck with me as a good summary of speaker characteristics. It's of course missing the phase shift response of the speaker but still conveys the relationship between resistance and impedance magnitudes.
To answer your question, the book is entitled "HI-FI LOUDSPEAKERS AND ENCLOSURES" Revised Second Edition by Abraham B. Cohen published by Hayden Book Company, ISBN 0-9104-0721-3 and it's the best I've ever seen at explaining the interaction of the electrical and physical aspects of speakers while still being an entertaining read.
12 used ones on Amazon.com:
http://www.amazon.com/Hi-Fi-Loudspeakers-Enclosures-Abraham-Cohen/dp/0810407213/ref=sr_1_1?ie=UTF8&qid=1299295811&sr=8-1
You can see it's pretty rare now and the used prices for it start at $15 and go up to $100 in a hurry.
Greg |
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