A question on v coil resistance (NOT impedance) - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 28th August 2002, 02:41 AM   #1
Fossil is offline Fossil  Singapore
diyAudio Member
 
Join Date: Sep 2001
Location: SG
Default A question on v coil resistance (NOT impedance)

For a voice coil with a DC resistance of 8 ohms, if I were to have a input of 1A (AC), is the 8W generated purely heat energy?
  Reply With Quote
Old 28th August 2002, 03:21 AM   #2
f4ier is offline f4ier  Australia
diyAudio Member
 
f4ier's Avatar
 
Join Date: Sep 2001
Location: Sydney
No, when we're dealing with AC signals, we will always need to consider the impedance, not just the real (resistive) part alone. In this case, there will be real power and reactive power. The real power can be calculated from voltage*current*Cos x, where x is the phase difference between the voltage and current input.

hth
__________________
Crossover/Subwoofer Simulator
  Reply With Quote
Old 29th August 2002, 12:14 AM   #3
diyAudio Member
 
Join Date: Sep 2001
f4ier, I think you missed the exact statement that Fossil made. He said for an input of 1A (ac). Therefore the reactive part, which is in series with the voice coil resistance, does not influnce the amount of heat generated in the voice coil. This is I^2*R, and so is 8W. Of course, there are other sources of dissipation, such as in the mechanical losses of the supension and cabinet, and in the air load resistance, but these are tiny compared to the voice coil.

Andrew
  Reply With Quote
Old 29th August 2002, 04:27 AM   #4
Ron E is online now Ron E  United States
diyAudio Member
 
Ron E's Avatar
 
Join Date: Jun 2002
Location: USA, MN
efficiency of a speaker is Sound power out/electrical power in, which reduces to:

no=9.614*10^-10*Fs^3*Vas/Qes

100*(1-no) is the percentage of power that goes to heat, assuming the speaker to be a resistor. Since the speaker is not a resistor, the efficiency actually varies with frequency. The true efficiency curve roughly follows the impedance curve, but there is generally no need for you to know that - unless your barroom conversations involve large bets about arcane audio topics.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Op amps: output impedance and load resistance mudihan Chip Amps 36 28th October 2012 03:15 PM
MIT Terminator Speaker Cables - Impedance and Resistance tone2222 Multi-Way 4 18th November 2006 09:01 PM
Impedance and Resistance newbie1 Parts 4 15th January 2004 09:43 PM
Temperature effect on voice coil resistance AudioFreak Multi-Way 5 2nd January 2002 01:14 AM


New To Site? Need Help?

All times are GMT. The time now is 10:11 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2