8 Ohm versus 4 Ohm

[SonicSeeker 101]

What is the difference between an 8 Ohm speaker and a 4 Ohm.

Does it require more power or less to drive them?

Are they more, or less efficient.

I am ignorant on this subject but with your help here I wont be.

Thanks.

[wvu80 5935]

I'm surprised nobody has jumped on this yet, and I don't feel qualified to give you an authoritative answer.

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I have a corollary question, what does it do to mix an 8 ohm with 4 ohm, as in an AVR that runs L/R at 8 Ohm and a 4 Ohm center?

+++

 

I don't know if these guys know what they're talking about, but they suggest always running the AVR in 8 Ohm mode.

 

https://www.youtube.com/watch?v=Ou5bO8P2Drw#t=21

Edited May 3, 2016 by wvu80

[mustang guy 2226]

What is the difference between an 8 Ohm speaker and a 4 Ohm.

Does it require more power or less to drive them?

Are they more, or less efficient.

I am ignorant on this subject but with your help here I wont be.

Thanks.

This should answer all of both of your questions.

 

http://www.prestonelectronics.com/audio/Impedance.htm

 

Impedance is to AC what resistance is to DC. Wiring multiple speakers so the impedance is lower (parallel) will make them louder, and make the amp hotter. Conversely, wiring them so as to increase the impedance (series) will make them less loud and the amp cooler.

[2point1 124]

4 ohm , your going to need a really good amp.

Even a 6 ohm speaker can cause an amp to run really warm

compared to a 8 ohm speaker.

 

 

I'm sure someone can give you a better explanation.

Edited May 3, 2016 by 2point1

[Matthews 1631]

Very simply, lets refer to my Digital Designs automobile amplifier.  If I run a single, 8 ohm woofer, it puts out 300 watts RMS.  When I step down to a 4 ohm woofer the power output doubles to 600 watts.  I currently run it at 2 ohms putting out 1200 watts of power into one channel.  This amp is capable and stable at 1 ohm but my charging system just can't handle it with out major upgrades - BOOOOO !!!

 

Matt ♪ ♫ ♪

Edited May 3, 2016 by Matthews

[mustang guy 2226]

Some amps output doesn't change with impedance. 

 

 

4 ohm , your going to need a really good amp.

Even a 6 ohm speaker can cause an amp to run really warm

compared to a 8 ohm speaker.

 

 

I'm sure someone can give you a better explanation.

 

You are right. The amp needs the load. I watched the video above, and those guys were talking like it didn't matter. If you have an amp that can do 8 ohm, you should either put that kind of speaker or figure a way to increase the load like wiring another speaker in series or adding a light bulb.  

 

edit: Of course you could also add a fan and never actually turn it up all that loud.

Edited May 3, 2016 by mustang guy

[mustang guy 2226]

Very simply, lets refer to my Digital Designs automobile amplifier.  If I run a single, 8 ohm woofer, it puts out 300 watts RMS.  When I step down to a 4 ohm woofer the power output doubles to 600 watts.  I currently run it at 2 ohms putting out 1200 watts of power into one channel.  This amp is capable and stable at 1 ohm but my charging system just can't handle it with out major upgrades - BOOOOO !!!

 

Matt ♪ ♫ ♪

In the pro world, they wire speakers in and subs in parallel. Kinda the same thing you are talking about.  I assume you are running a pair of 4 ohm sub drivers in parallel from the single 2 ohm channel, right? 

[Matthews 1631]

Actually running a pair of 2 ohm woofers. I was running a pair of 4 ohm DVC wired down to 1 ohm at the amp and that is where I ran into problems with the charging system. It was either upgrade my power cables and add a battery or change the woofers out.

[tigerwoodKhorns 747]

I'll give you a very easy way to understand. 

 

Think of drinking through a straw. 

 

An 8 ohm load is like drinking through an small cocktail straw.  It does not take much effort to get liquid through, but you are not going to move a large amount of liquid.  (easy load for an amp)

 

a 4 ohm load is like a large straw.  You can move quite a bit of liquid, but you need the ability to suck really hard on the straw (tough load). 

 

Now, high current does not equal high sound output, but many higher end speakers have a lower impedance for reasons that are above my knowledge. 

[JohnA 807]

What is the difference between an 8 Ohm speaker and a 4 Ohm.

Does it require more power or less to drive them?

Are they more, or less efficient.

I am ignorant on this subject but with your help here I wont be.

Thanks.

 

Impedance is the resistance/restriction to the flow of electric current.  Four ohms is less and thus will draw more current for a given voltage applied to the speaker.  Some amps cannot deliver the extra current without overheating near max output. 

 

There is no other inherent impact to any speaker's other characteristics, like efficiency. 

[derrickdj1 8228]

This is a nice topic and that was a good read mustang guy.  When talking about amps, I always heard of the the high current(SS) vs the high voltage amps(tube).  A lot of people would say that a low watt tube amp delivered more power to the speaker than a SS amp.  Getting an understaning of speaker impedance goes a long way when selecting an amp.

[MetropolisLakeOutfitters 2622]

What will really bake your noodle is that some 8 ohm speakers are actually fairly hard to drive due to huge impedance dips and swings, while some 4 ohm speakers such as Magnepans are easy to drive due to the impedance being pretty steady throughout most frequencies.

Actually, if you're asking the initial question, it will probably bake your noodle just to figure out that the impedance of speakers is frequency dependent and the nominal impedance that it is labeled as is somewhat subjective. In reality, a typical 8 ohm speaker is going to be all over the charts.

[Matthews 1631]

What will really bake your noodle

LOL - as well will dual 12" subs running at one-half ohm with 2400 watts pumping them.  Bake your noodle and alter your vision all in one

[MetropolisLakeOutfitters 2622]

There is no other inherent impact to any speaker's other characteristics, like efficiency.

At least based on my limited understanding of this, it also changes the damping factor of the system, which is the ratio of the output impedance of the amp to the impedance of the speakers. An 8 ohm woofer will have twice the damping factor of a 4 ohm woofer. When the bass hits, a woofer will generate back EMF that controls the motion of the cone, which is what makes bass sound tight. An amplifier with a high output impedance going into a low impedance speaker load will be much more sloppy than the other way around.

Edited May 5, 2016 by MetropolisLakeOutfitters

[MetropolisLakeOutfitters 2622]

The other interesting thing about raw drivers rather than assembled speakers is that if you're reading spec sheets, you might find yourself noticing that the motor strength of an 8 ohm woofer is much stronger than its otherwise identical 4 ohm equivalent. If you do the math based on actual motor strength plus the current coming in, it actually works out to being pretty much equal, only thing that really changed is the load that the amp sees. Refer to Acoustic Elegance TD series for an example.

With this in mind, a lower impedance load isn't necessarily superior. If you get the same output due to a higher motor strength as well as higher damping, that 8 ohm might be what you need.

Edited May 5, 2016 by MetropolisLakeOutfitters

[djk 437]

"you might find yourself noticing that the motor strength of an 8 ohm woofer is much stronger than its otherwise identical 4 ohm equivalent."

 

Bl?

 

10, 14, 20, which is the best?

 

4Ω, 8Ω, 16Ω,

 

The force factor (Bl) is the same for all three of the drivers, after you take the impedance into consideration.

[richieb 5570]

I know that on my Wright 2a3 monoblocks at 3.5 watts and are equipped with 4, 8 and 16 taps, the KHorns had more body and bass response on the 4 ohms.

[pzannucci 652]

I know that on my Wright 2a3 monoblocks at 3.5 watts and are equipped with 4, 8 and 16 taps, the KHorns had more body and bass response on the 4 ohms.

Interaction of the impedance of the output transformer (and other components) to the speaker impedance.