building speakers, i need help with ohms..

Jeff:L

Auditioning
Joined
Jun 28, 2004
Messages
12
I would like to build some bookshelf speakers or maybe floorstanding speakers. I know that my receiver puts out 85 watts at 8ohms. Well one midrange is 8 ohms, and one tweeter is 8 ohms. So I can wire them to get either 4 ohms or 16 ohms right? So how can I get my bookshelf speakers to have the correct ohms? (8ohms)?

Imagine if I wanted two midrange and one tweeter (all 8 ohms).. how would I get 8 ohms out of that? Any help is appreciated... thanks!
 

Dave Poehlman

Senior HTF Member
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Mar 8, 2000
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3,813
Well, I believe the filter circuit (crossover) splits the power so you still wind up with roughly an 8 Ohm loudspeaker with an 8 Ohm tweet and 8 Ohm mid.

Now, if you threw another mid into the equation, those would be wired in parallel and give you an end result of 4 Ohms on the mid side, while the tweeter would still give you 8 Ohms. So, the total would be sort of an average somewhere around 6 for the whole speaker.

Most modern receivers are capable of handling a 4 to 8 Ohm load, so as long as you're within that range, you're fine.

Does that make sense?
 

Rory Buszka

Supporting Actor
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Jun 5, 2002
Messages
784
Since the bass range makes the greatest current demands on the reciever's amplifiers, I would get an amp that can support a 4 ohm nominal load if your midbass or bass section is going ot be nominally 4 ohms. It is not a perfect averaging since the demand on the amplifier in the treble range is less than 20% that of the demand of the bass section.
 

ThomasW

Senior HTF Member
Joined
Nov 6, 1999
Messages
2,282
Regardless of what the crossover does, the impedance of the woofer is the impedance of the system.
 

Dan Wesnor

Second Unit
Joined
Apr 28, 1999
Messages
389
Actually, the crossover can raise the impedence of the system above that of the woofer, but only if the designer knows what he is doing.
 

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