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View Full Version : why are home theater subs at a higher impendence



vosschs
11-24-2005, 02:10 PM
ok my question is why home theater subs run at a higher impendence than say car audio subs, most of the time i see ht subs run at 8 ohms, from what i understand there is less resistance at a lower ohms, so wouldnt it be almost ideal to run them at 1 2 or maybe even 4 ohms...... why use 8 at all...... i have no idea about all of this really just curious



EDIT, i guess i coulda put this in HT, but it deals with things in general.... hehe

Pyro_By_Nature
11-24-2005, 02:45 PM
Most home amps are meant to run at higher impedences...............

Not everyone wants 1,000 watts at 1ohm with 20% thd

azbass
11-24-2005, 02:48 PM
mines at 4ohm

thch
11-24-2005, 02:49 PM
in short:
1.) wire length. wire is resistive. in home audio you might have a 50ft run of wire. if you want this to be 24g or 18g, well, the speaker needs to be more resistive so power isn't lost in the wire.

2.) there are design issues with high current output amplifiers. there are also issues for high voltage output amps. low impedance speakers need lots of current, high impedance need lots of voltage. thus there is a happy medium.

vosschs
11-24-2005, 02:49 PM
Most home amps are meant to run at higher impedences...............

Not everyone wants 1,000 watts at 1ohm with 20% thd
ok why would they want to be ran at higher ohms, isnt it easier to let them run at a lower ohm....... also i dont relaly know what thd is and how it accects it

SUB_URBAN
11-24-2005, 06:25 PM
ok why would they want to be ran at higher ohms, isnt it easier to let them run at a lower ohm....... also i dont relaly know what thd is and how it accects it
Thd is basically distortion. The more you have the crappier your speakers will sound. That is why Class AB amps are used for componets so that you have a nice clear sound. They have a lower thd % while being less efficient. Class D amps are only used on subs because their efficiency is much better but sacrifices thd.



edit- spelled sacrifice wrong for some reason.

squeak9798
11-24-2005, 07:57 PM
That is why Class AB amps are used for componets so that you have a nice clear sound.

Many full range Class D amps, moreso in home audio but there are some car audio full range Class D amps aswell (Xtant, Eclipse, Infinity IIRC, etc). Class T is essentially a full range class D with a Tri-path chip, which many companies have produced in both car and home audio.

You'd be hard pressed to hear any difference between them. In fact, Richard Clark has $10k on the line that you won't ;)


Class D amps are only used on subs because their efficiency is much better but sacrifices thd.

See above.

joetama
11-27-2005, 04:57 AM
**** thch you nailed that one on the head....

PV Audio
11-28-2005, 11:23 PM
in short:
1.) wire length. wire is resistive. in home audio you might have a 50ft run of wire. if you want this to be 24g or 18g, well, the speaker needs to be more resistive so power isn't lost in the wire.

instead of modeling the speaker differently, why not use a lower gauge wire?