• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Driving 4 ohm speakers...

cwall99

cwall99

AK Subscriber
Subscriber
My technical knowledge is a bit thin. Okay, very thin.

Anyhow, what's the deal with driving 4 ohm speakers instead of 8 ohm speakers?

What sort of considerations do I need to make when connecting them to an amp or a receiver?

What about (and this is really for you home theater guys out there) integrating 4 ohm left and right main speakers with an 8 ohm center channel?

A friend of mine is considering picking up some used 4 ohm speakers, and he's just too danged shy to post here. (Me, I have no qualms about putting my ignorance on display).

Thanks.
 
Register to hide this ad
The amp or receiver will be rated to go down to a certain load (usually 4 ohms, but sometimes 8, sometimes 2). A lot situations where you have two pairs of speakers running at once will change the impedance (two pairs of 8 ohm speakers = 4 ohms per channel, etc), but that depends on the unit too. Best to find the owner's manual for the receiver in question. If not, maybe you can find info in the specs online, or maybe it's printed on the back panel.

I'm not a home theater guy, but the impedance difference probably isn't an issue. You would just need to check to make sure the receiver can handle 4 ohms / channel, and then it's the effective sensitivity difference that will matter (which could happen with any impedance combination). It's just a matter of getting the relative volume levels correct. I assume all but the cheapest surround receivers provide adjustments for that, though I don't really know.
 
If it is a discrete center channl then it will not have any affect running 4s for L-R and an 8 for the center. The issue is A+B main in parallel.
 
Check to make sure you receiver can handle a 4 ohm load. Many receivers can't or are not supposed to, even high end receivers. Find the specs or owners manual and see if it can handle them.
 
Like folks said, check the owners manual or manufacturer's website. Typically Yamaha and Harman Kardon HT/Stereo recievers have no problems with 4 ohms, but double check. My HK and Yamaha gear runs 4 ohm speakers just fine. My Marantz gear will not.
 
the other thing to consider is that speakers rated at 4 Ohms can sometimes fluctuate quite a bit from that nominal value. if they drop down much below that in the bass range (the worst offenders being Infinity Kappa 9's, Apogee Scintillas, and a few others), you can have instant bad news. if the load dips no lower than 4 Ohms or so, the truth is you can often get away with living dangerously and running an amp that isn't rated that low, but you need to be somewhat judicious with the volume and keep an eye on the unit. the main problem with lower-impedance loads is the extra heat generated so you should always do your best to keep the receiver or amp pretty well ventilated, even if it is rated to handle pretty tough loads.

PS: here is a good thread that's pretty eye-opening, though being a fan of 4-Ohm speakers i tend to ignore some of the issues more than i probably should:

http://www.audiokarma.org/forums/showthread.php?t=60386
 
cdfac said:
the other thing to consider is that speakers rated at 4 Ohms can sometimes fluctuate quite a bit from that nominal value.
Click to expand...

I've never really understood how this happens, resistance is constant right? I can see it if your driving the hell out of some cheap speakers and your super heating the voice coils with a high powered amp which would lower there resistance but I don't see how well engineered speakers would have large fluctuations in the impedance.
 
Last edited:
Vintage_Hi-F said:
I've never really understood how this happens, resistance is constant right? I can see it if your driving the hell out of some cheap speakers and your super heating the voice coils with a high powered amp which would lower there resistance but I don't see how well engineered speakers would have large fluctuations in the impedance.
Click to expand...

IIRC impedance of a coil is not constant, it is dependant on the current. True resisrance such as a resistor is constant, it always reduces the same amount of current.
 
dan-c said:
IIRC impedance of a coil is not constant, it is dependant on the current. True resisrance such as a resistor is constant, it always reduces the same amount of current.
Click to expand...

Thanks. Though I will say if you have a quality amp it should be fine with 4 ohm load. I mean when you buy a $600-1000 Sansui/Marantz/Onkyo/Pioneer/whatever it should have no problem with a pair of high end 4 ohm speakers, it just wouldn't make any sense. It would be like buying a 100k+ sports car but you can't drive it over 65 because the transmission can't take that punishment.
 
Vintage_Hi-F said:
I've never really understood how this happens, resistance is constant right? I can see it if your driving the hell out of some cheap speakers and your super heating the voice coils with a high powered amp which would lower there resistance but I don't see how well engineered speakers would have large fluctuations in the impedance.
Click to expand...

dan-c said:
IIRC impedance of a coil is not constant, it is dependant on the current. True resisrance such as a resistor is constant, it always reduces the same amount of current.
Click to expand...

Afaik, the variance is mostly dependent on the frequency of the signal and the (inductive) reactance of the voice coil. Of course, other crossover components may influence this as well by trying to smooth it out with Zobel network.

Znom3.png
 
Last edited:
Another thing to consider, is how your're running your system. If you just play it casually and the amp carries a 4 ohm rating, then sould be fine. If running the system hard a lot with 4 ohm load's, then best to use an amp with at least some kind of listed 2 ohm rating, as most modern speaker's dip well below their nominally rated impeadnace's in the bass range. Also, as for mention of equipment with A/B speaker switching, most modern reciever's run the connected speaker's in series when in the A+B mode to keep impeadance's up. Easy to check for series, as the main speaker's will go dead, if no B pair connected when switched A+B
 
You must log in or register to reply here.
Back
Top Bottom