Resistance and Impedance
09-12-00, 06:45 PM
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Well, impedence is a measurment of a speakers general resistance. Most home speakers are rated between 4-8 ohms, but these are not hard numbers but more of a average operating area as the actual resistance fluctuates greatly in a speaker depending on the frequencies being reprodeuced and the material used.
Most amps today in receivers or separates can handle speakers in the 4-8 ohm range. However, the lower the rated ohms of the speaker the more current needed to drive the speaker. Cheaper receivers may have a problem with 4 ohm speakers, so take that into account during yor purchases.
As for which speakers to get, buy what sounds the best to you then match the speakers to your receiver because there is a very good chance you will upgrade your receiver before your speaker.
J
J
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Most amps today in receivers or separates can handle speakers in the 4-8 ohm range. However, the lower the rated ohms of the speaker the more current needed to drive the speaker. Cheaper receivers may have a problem with 4 ohm speakers, so take that into account during yor purchases.
As for which speakers to get, buy what sounds the best to you then match the speakers to your receiver because there is a very good chance you will upgrade your receiver before your speaker.
J
J
------------------
Don't be a luddy-duddy! Don't be a mooncalf! Don't be a jabbernowl!
09-12-00, 07:29 PM
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Hmm, I know what this means, but I'm not sure I know how to explain it to someone who isn't an EE.
Resistance basically is the measurement of how difficult is it for a steady (DC) electric current to pass through a conductor.
Impedance is the same measurement for changing (AC) currents. The impedance of a conductor changes depending on the frequency of the electrical signal passing through it.
The impedance rating on the speaker is actually more of an average or typical value of the varying impedance of the voice coil, crossover, etc. over the audio frequency range. It's like a person saying, "My pulse is 80." Actually, his/her pulse will cover a broad range, maybe dipping to 58 while relaxing and reading DVDTalk, and going up to 170 when following Billy Blanks through some Tae-Bo.
From the standpoint of a speaker buyer, look for an impedance rating around 8 ohms and you'll be fine with nearly all receivers and amps. Most speakers you are likely to find will fall into this category. If it says 6 ohms, don't worry.
Resistance basically is the measurement of how difficult is it for a steady (DC) electric current to pass through a conductor.
Impedance is the same measurement for changing (AC) currents. The impedance of a conductor changes depending on the frequency of the electrical signal passing through it.
The impedance rating on the speaker is actually more of an average or typical value of the varying impedance of the voice coil, crossover, etc. over the audio frequency range. It's like a person saying, "My pulse is 80." Actually, his/her pulse will cover a broad range, maybe dipping to 58 while relaxing and reading DVDTalk, and going up to 170 when following Billy Blanks through some Tae-Bo.
From the standpoint of a speaker buyer, look for an impedance rating around 8 ohms and you'll be fine with nearly all receivers and amps. Most speakers you are likely to find will fall into this category. If it says 6 ohms, don't worry.
09-13-00, 02:22 AM
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which speaker is more sensitive? the one with higher or lower impedance? And how does sensitivity and efficiency relate? Which one is, well theoretically speaking, better?
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09-13-00, 05:45 AM
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Impedence has no correlation to the efficiency of a speaker, AFAIK. I've seen 4 ohm speakers with 88db ratings, and my 8 ohm Wharfedales are rated at 91db.
Efficiency, measured in decibels, is simply how much power the speaker receives that is actually converted into sound. A more 'efficient' speaker (say 92db) will simply sound louder than a less efficient speaker (say 88db) from the same amount of watt power.
Efficiency and sensitivity are quite often used interchangably when talking about speakers.
Is it better to have speakers that are more efficient? Well, probably, but the only real conclusive test is your own ear.
Do a search on any search engine for 'speaker terminology' and you'll find tons of pages that explain this a lot better than I can.
[This message has been edited by Bollux (edited September 13, 2000).]
Efficiency, measured in decibels, is simply how much power the speaker receives that is actually converted into sound. A more 'efficient' speaker (say 92db) will simply sound louder than a less efficient speaker (say 88db) from the same amount of watt power.
Efficiency and sensitivity are quite often used interchangably when talking about speakers.
Is it better to have speakers that are more efficient? Well, probably, but the only real conclusive test is your own ear.
Do a search on any search engine for 'speaker terminology' and you'll find tons of pages that explain this a lot better than I can.
[This message has been edited by Bollux (edited September 13, 2000).]
09-13-00, 04:36 PM
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Chris, impedance is actually the combined effect of both resistance and something called "reactance". The "reactance" is the part that depends on the frecuency of the signal. It's a phasor sum, because impedance is actually a complex number (Said what???):
Z=R+jX
where R is resistance and X=2x3.14xfxL is the reactance. The magnitud of the impedance (the plain number of ohms) is
Z=square root of R square + X square
There's your free EE class for today, everyone!
borimex
Z=R+jX
where R is resistance and X=2x3.14xfxL is the reactance. The magnitud of the impedance (the plain number of ohms) is
Z=square root of R square + X square
There's your free EE class for today, everyone!
borimex
09-13-00, 06:45 PM
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Then I have the 64,000$ question:
If my speakers are rated "between 4-8 ohms" and my receiver has a selector which can be set at 4 or 8 ohms, which setting would be best to use? And why?
I have Deftech speakers (sub is my only amplified speaker) and a Yammie 795 receiver.....
If my speakers are rated "between 4-8 ohms" and my receiver has a selector which can be set at 4 or 8 ohms, which setting would be best to use? And why?
I have Deftech speakers (sub is my only amplified speaker) and a Yammie 795 receiver.....
09-13-00, 07:04 PM
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quote:<HR>Originally posted by JLB:
Then I have the 64,000$ question:
If my speakers are rated "between 4-8 ohms" and my receiver has a selector which can be set at 4 or 8 ohms, which setting would be best to use? And why?
I have Deftech speakers (sub is my only amplified speaker) and a Yammie 795 receiver.....<HR>
To be safe, select the 4 ohm setting so that the receiver can limit the current output before it clips the music signal to the speakers. Otherwise, your speakers might draw too much current and drive the amp into clipping.
Or set it to 8 ohms, and do nothing until you do drive the amp to clipping.
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09-13-00, 08:05 PM
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I appreciate the effort, Borimax, but I already knew all that.
As in, I am an EE
.
quote:<HR>Hmm, I know what this means, but I'm not sure I know how to explain it to someone who isn't an EE.<HR>
As in, I am an EE
.
09-14-00, 04:01 AM
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I'm just a HT/AV peon, but is the impedance/resistance mentioned here in the context of power = current^2 * resistance? I'm just taking a stab here, but I'm assuming that maybe power refers to the power output. So would a lower impedance speaker thus draw more current to deliver the same power as a higher impedance speaker? Thanks in advance (for putting me in the know).
09-14-00, 11:57 AM
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> I appreciate the effort, Borimax, but I already knew all that.
I'm sure you did, but your answer was a little short. I just wanted to clarify it further. Even though I addressed my note to you at the beginning, I meant to talk to everyone in the forum, most of which are probably not EE's.
borimex (not "borimax")
I'm sure you did, but your answer was a little short. I just wanted to clarify it further. Even though I addressed my note to you at the beginning, I meant to talk to everyone in the forum, most of which are probably not EE's.
borimex (not "borimax")
