4 ohm versus 8 ohm speakers

[bradandbree]

When buying speakers like the Axiom M80s which are 4 ohm speakers, how does this influence the requirements for amplification? I see power ratings for amps and receivers that show different wpc for different ohm loads, so I suspect any good amp/receiver can drive 4 ohm speakers. Is that true?

Thanks.

 

[OttoMatic]

Hi there,

If an amp is spec'd to drive 4 ohms, then I would suspect that it will be able to handle that load. Many good amps can drive the 4 ohm load; some cannot. Many, many receivers will not like a 4 ohm load. Check the documentation before buying, just to be sure.

The problem is that with a decreased impedance (4 ohms vs 8 ohms), the speaker demands twice the power from the amplifier. If the amplifier cannot provide it, problems can ensue. I've run many, many receivers with a 4 ohm load when they don't necessarily want it. At lower volumes, I've never had a problem. At higher volumes, the unit may get hot, run out of gas early, and go into protect mode. Worst case, it will fail prematurely, but I think that unlikely with a well-protected and engineered amp or receiver.

Find a nice amp, and you'll be fine.

 

[cfrizz]

The vast majority of receivers do not like 4ohm loads. Most say 6-8ohms. The receivers that will accept them are very expensive. B & K, Sunfire come to mind.

You would be better off either getting separate components prepro & amplifier, or getting a less expensive receiver that has preamp outputs & also purchase a separate amplifier of at least 200wpc.

An amplifier with this much power will run ANY speakers you hook up to it whether the are 8 or 4 ohms.

Either way, it's going to cost more to get the right equipment to play your speakers to thier full potential.

 

[bradandbree]

Otto and cfrizz,
Thanks for your input and advice. Much appreciated.

 

[bradandbree]

By the way, if a 4 ohm speaker demands twice the power of an 8 ohm speaker, which in turn can potentially cause those problems you mentioned, what are the technological and/or auditory advantages to making a 4 ohm speaker? (I took physics in college, but that was over 15 years ago, so please don't get too technical.)

 

[Haoleb]

At higher volumes, the unit may get hot, run out of gas early, and go into protect mode. Worst case, it will fail prematurely, but I think that unlikely with a well-protected and engineered amp or receiver.

Not to mention you can damage your speaker drivers, as one owner just found out over on the Axiom forums.

 

[cfrizz]

Your guess is as good as mine Brad!

I didn't know about the different level of speakers until I joined the Polk board and started thinking of getting thier 4ohm LSI speakers.

That was when I found out that my Denon receiver couldn't handle them! So that in turn sent me on getting an amplifier that could handle them. Which is when I got a 205wpc Parasound 2 channel amp.

It made such a huge improvement in how my 17 yr old 8ohm Polk RTA-8T's sound that I pretty much have shelved the idea of getting new speakers.

Instead I went on a quest to amp all of my speakers, which I did with the amp that is in my signature.

A lot of so called audiophiles don't like it when I recommend getting a minimum of 200wpc amplifier for all kinds of reasons. But I don't care, I know from experience that it works for easy & hard to drive speakers. I know that all of my speakers are operating to thier full potential. Which is what I think we all want out of our speakers.

Knowing that, I don't really care whether the speakers are 8 or 4ohms I simply will listen to different speakers until I find some that will make me as happy as my RTA-8T's have done for the last 17 years.

By the way, if a 4 ohm speaker demands twice the power of an 8 ohm speaker, which in turn can potentially cause those problems you mentioned, what are the technological and/or auditory advantages to making a 4 ohm speaker? (I took physics in college, but that was over 15 years ago, so please don't get too technical.)

 

[the grunt]

In the thread mentioned by Haoleb above Alan Lofft, “Axiom Resident Expert”, said this:

As I've explained in previous posts, the AV receiver brands that Axiom has found able to drive the 4-ohm M80s without severe current limiting or shut-down are: Sherwood Newcastle (which we have bench-tested and which Axiom sells on-line); Denon, Harman/Kardon, B&K, Rotel, NAD, and McIntosh.

The AV receiver brands to avoid if you want to get the 4-ohm M80s are: Sony, Kenwood, Onkyo, JVC, and Yamaha (except for one or two models).

p.s. to my previous post: In my list of recommended AV receiver brands that will drive the M80s, I forgot to include Outlaw Audio.

You might want to post in the Axiom forum for some specific recommendations. My only experience with the M80s is using a Denon 2807 but I don’t play them very loud most of the time.

 

[MDS]

By the way, if a 4 ohm speaker demands twice the power of an 8 ohm speaker, which in turn can potentially cause those problems you mentioned, what are the technological and/or auditory advantages to making a 4 ohm speaker? (I took physics in college, but that was over 15 years ago, so please don't get too technical.)

Voltage, Current, and Impedance are all related via Ohm's Law. The voltage capability of a receiver or amp is fixed at a certain level (the 'rail voltage'). Lower impedance causes the Current requirement to go up. Receivers often don't have adequate power supplies to supply the required current when they are pushed near their limits; ie high volume.

When the current goes up so does the Power but that does not mean that a 4 ohm speaker will play louder than an 8 ohm speaker as there are many other factors.

There is no advantage or disadavantage to designing a 4 ohm speaker. It is what it is. The designer designs it to sound the way they want and to have a certain frequency response and the nominal impedance is a byproduct of that. The short story is if you pick a speaker with a 4 ohm nominal or lower impedance you will need beefy amplification to deal with it at higher volumes. That is why it's usually best to pick your speakers first and then decide on what receiver/amplifier to drive them.