What is the difference 4 ohm&8 ohm speakers?

Raymond White · Post by **Raymond White** » 29 May 2008 4:47 am

could some one explain the difference in the 4 ohm and the 8 ohm speaker,please,Thanks ,Ray White Byron Ga.E Mail me at (steelmanplayer@yahoo.com).....

Jack Stoner · Post by **Jack Stoner** » 29 May 2008 6:45 am

The difference, electronically is 4 ohms. One speaker has an Impedence (AC Resistance) of 4 ohms and the other obviously 8 ohms. As far as a speaker's response, power handling, etc the resistance does not play much of a part. e.g. the Peavey 1203 speaker (used in the old Peavey Nashville 112E Steel Guitar speakers) is available in both 4 and 8 ohm versions. Looking at the frequency response curves for both speakers they are almost identical.

The reason for different impedences can be because an amplifier requires a certain impedence or to get the rated output of an amplifier it requires a certain impedence. Another issue is multiple speakers in an amp (or enclosure) and for example if the power amplifier you are using requires 4 ohms for full power output and you have two speakers in parallel you would need two 8 ohm speakers to get the 4 ohms Impedence load.

I can go on, but this is enough. If you want more, post on the Electronics section, not this For Sale section (your question may get moved to the Electronics section anyway).

Post by **Dave Mudgett** » 29 May 2008 6:55 am

Physically, the higher the impedance, the larger the resistance to current flow through the speaker coil's windings. This could be, in principle, due to different numbers of windings in the speaker coil, use of a thinner speaker coil wire, different magnetic properties in the speaker magnet, and I suppose other things too.

The main issue with speaker impedance is how it matches with the amplifier. A tube amplifier wants to see a specific impedance - if its output circuit is set for 4 ohms, it wants to see 4 ohms for maximum power transfer. There can be problems seriously mismatching a tube amp.

On the other hand, most (not all) solid-state amps have a minimum load impedance they can tolerate, and get maximum power at that impedance. So, for example on a typical Peavey steel amp like a Nashville 400, "210 W 4 OHMS" is written on the back. If you look at the technical specs for a Nashville 400, it will also show that one gets only 130 Watts at 8 ohms. I interpret all this to mean that I should never run the amp below 4 ohms, for a max rated power of 210 Watts, and if I run a higher impedance load, the power output will be smaller.

Curt Langston · Post by **Curt Langston** » 29 May 2008 7:44 am

Physically, the higher the impedance, the larger the resistance to current flow through the speaker coil's windings. This could be, in principle, due to different numbers of windings in the speaker coil, use of a thinner speaker coil wire, different magnetic properties in the speaker magnet, and I suppose other things too.

The main issue with speaker impedance is how it matches with the amplifier. A tube amplifier wants to see a specific impedance - if its output circuit is set for 4 ohms, it wants to see 4 ohms for maximum power transfer. There can be problems seriously mismatching a tube amp.

On the other hand, most (not all) solid-state amps have a minimum load impedance they can tolerate, and get maximum power at that impedance. So, for example on a typical Peavey steel amp like a Nashville 400, "210 W 4 OHMS" is written on the back. If you look at the technical specs for a Nashville 400, it will also show that one gets only 130 Watts at 8 ohms. I interpret all this to mean that I should never run the amp below 4 ohms, for a max rated power of 210 Watts, and if I run a higher impedance load, the power output will be smaller.

This is of the utmost importance!

Basically it is broken down to this:

An 8 ohm resistance, the amp draws less resistance {or power}(from the amplifier) than a 4 ohm load does. (speaker).

As you increase the load, (get lower in ohms), the resistance increases,(ohms decrease), and it draws more from the amp! (puts a strain on)

Don Discher · Post by **Don Discher** » 29 May 2008 9:34 am

I thought the answer was "4", oh well, it's been a slow day !

Post by **Dave Mudgett** » 29 May 2008 11:46 am

On a solid-state amp, the problem with going below the the rated load (speaker) impedance is that the speaker can draw too much current and exceed the current capacity of the output transistors - blam, they're gone. That's the Ohm's law thing - I = E/Z where E, I, and Z are the complex voltage, current, and impedance. Although that type of calculation is a bit more complex than regular real number arithmetic (no pun intended), you can see that if one assumes the applied voltage E is the same, the current I goes up as the impedance Z goes down.

Doug Childress · Post by **Doug Childress** » 29 May 2008 12:51 pm

You need to match your speaker ohms to your amplifier ohm rating. Most amps will have the ohm rating stamped on the back. A 4 ohm head will match with a 4 ohm speaker. Putting an 8 ohm speaker with a 4 ohm head (or vice versa) is not the best match.

Kevin Hatton · Post by **Kevin Hatton** » 29 May 2008 3:04 pm

The difference betwee a 4 ohm and an 8 ohm speaker is 4 ohms. At least that is what Jethro Bodeen told me.

Tony Glassman · Post by **Tony Glassman** » 29 May 2008 5:57 pm

The way I understand resistance.....

As R (resistance) decreases (say, from 8 ohms to 4 ohms) at a given voltage:

1]current (I) increases......(I=V/R)
2]power (P) increases........(P=V2/R)

V2= V squared

Dave's right........running at a lower resistance than recommended can damage your amp.

James Harrison · Post by **James Harrison** » 29 May 2008 10:13 pm

I agree with what Dave Mudgett said. Impedance Matters.
James

Jim Sliff · Post by **Jim Sliff** » 30 May 2008 5:50 am

I think Doug Childress gave the answer that was probably the response to the actual question. Not that the other answers were not good, but it sounded like a simple "why are there different speaker impedances?" question - the answer being "because there are different amp designs, and the speaker impedance needs to match what the amp requires".

That's how I read it, anyway. I know sometimes I get too technical...this was one of those times I was tempted and then thought about what was REALLY asked.

Roger Francis · Post by **Roger Francis** » 30 May 2008 12:42 pm

Is there a tonal diff between the 2?

Tom Mossburg · Post by **Tom Mossburg** » 31 May 2008 9:37 pm

There probably would be a slight difference if used on the same amp. The reason being is impedance unlike resistance is frequency dependent and is denoted as Z not R. Since the amp is designed to see a certain load it would react differntly into another load. You can get real nitpicky with this subject. As the frequency changes the impedance of the speaker actually changes with it and its peaks and valleys of response will vary. As far as delivering power part of the power is turned into sound energy and part of it is reflected back into the amp which can cause damage if there is a mismatch. Its kind of like looking through a glass window and seeing a reflection. Thats what happens to an amp when the impedance is a mismatch. If you've got two pendulums side by side in sync they go on there merry way just pendulumizing. But if one is out of sync there is bound to be collisions and sooner or later there will be damage.

So the answer is yes but all other things equal there won't be that much difference in sound. Is this confusing enough?

Olli Haavisto · Post by **Olli Haavisto** » 1 Jun 2008 1:59 am

There are amps that are rated 4 ohms but the manufacturer says that they perform "more musically" with a 8 ohm load. I think I`ve read that about the MosValve and the Evans(both SS).
Any opinions? I have both the Evans and a couple MVs and I don`t hear a drastic difference between 4 or 8 ohm loads, except,of course, that the amps are a bit louder with a 4 ohm load.

Tony Prior · Post by **Tony Prior** » 1 Jun 2008 2:15 am

Kevin Hatton wrote:The difference betwee a 4 ohm and an 8 ohm speaker is 4 ohms. At least that is what Jethro Bodeen told me.

uhmm..Jethro told me it was 3 ohms difference..

Now I'm confused (short trip)

Additionally, do not overlook that amplifier output stages are designed to the output impedance criteria, so you cannot just swap speakers around or you can certainly cause damage to the amp ouput stage.

Jethro did NOT tell me that...

Shannon Boatman · Post by **Shannon Boatman** » 1 Jun 2008 3:55 am

Jethro told me that modern medical science has come a long way dealing with impedance.

Tom Mossburg · Post by **Tom Mossburg** » 1 Jun 2008 8:51 am

Back when Jethro was at his peak, he wanted to be a fry cook or brain surgeon. He really didn't mess with music that much except for one show where Jed convinced him to give it up. Jethro himself had a serious impedance mismatch. You could think of Jethro as the load and the world around him the amp. Bang! Where on the other hand Ellie Mae was a perfect match for most all circumstsnces. Now I know this makes sense to most everybody.

The Steel Guitar Forum

What is the difference 4 ohm&8 ohm speakers?

What is the difference 4 ohm&8 ohm speakers?

Indeed!

ohmm