Can someone explain exactly how ohms function?

[yodaeatsfishstx]

I have a TR, 85 watts into 4 ohms, two speakers at 8 ohms. If I wanted to run say, 1 speaker, would I want 4 ohms, 8 or 16? Also, if I wanted to down the road add the 2nd speaker, would I need to replace the first?

:dunno

[mojo2001]

One speaker = 4 ohms

If you want two speakers, put the original 8 ohm speakers back in parallel = 4 ohms again.

When you parallel speakers it divides the ohm rating in half.

[yodaeatsfishstx]

What happens if I run a 4 ohm amp into a single 8 ohm speaker?

[pics2050]

You may notice a minor drop in volume. I understand most tube amps can take +-100% speaker impedance mismatch...ie hooking a 4 or 16 ohm speaker (cab) to an 8ohm output should be safe for example.

[yodaeatsfishstx]

My goal for this is to be able to run one speaker to save some weight, but still be able to add the 2nd down the road. Has anyone done this with a Twin?

[mbratch]

If you want to have just one speaker but be able to add another (leaving the original one in there) then I'd go with one 8 ohm speaker. The second, if you add it, should also be 8 ohm and wired in parallel.

[phsyconoodler]

The best way to save weight in a Twin is to use neodium magnet speakers,like the Jensen neo's.
They are waaaaaay lighter and sound great.Two are lighter than one stock speaker.

[strat a various]

You're only saving about nine lbs. with stock speaker. Go ahead, won't hurt anything. Twins run into 8 ohms no problem. Just be careful you don't blow the single speaker.
It's a real possibility.

[JJman]

Pull one speaker and (the proper) two tubes for harmonic convergence.

[yodaeatsfishstx]

Another reason behind it is that I'd rather spend the dough on one speaker now, get a significant tonal upgrade, then when I have some more scrounged up, to get the 2nd.

Anyone have some experience on any neodium speakers?

[yodaeatsfishstx]

So I've decided to go with KST 60 or 70 for my twin. They're both rated at 80 watts, so I should be safe with just 1, right?

[strat a various]

Since an 85 watt (RMS) amp can develop peak wattage approaching 150 watts, I wouldn't be too comfortable with one 80 watt speaker. In other words, don't crank it too high for too long.

[dolt45]

Just "piggy-backing" on this thread ...

As I understand it (note: I'm no expert on speaker impedance) A combo amp that puts out 120 watts @ 4 ohm could work w/ a single speaker rated at 60 watts @ 8 ohms - correct?

There'd be loss of volume, but the amp & speaker would operate safely.

Is that correct?

Adding an extension speaker, say another 60 watt @ 8 ohms, would bring things back to 120 watts @ 4 ohms ... yes?

Thanks for any insights on the topic.

[strat a various]

Just "piggy-backing" on this thread ...

As I understand it (note: I'm no expert on speaker impedance) A combo amp that puts out 120 watts @ 4 ohm could work w/ a single speaker rated at 60 watts @ 8 ohms - correct?

There'd be loss of volume, but the amp & speaker would operate safely.

Is that correct?

Nope, an 85 watt tube amp is an 85 watt tube amp. Double the impedance and it'll sound a little different, you may risk some damage to the output tranny, but you'll still have aprox. 85 watts output.

You're thinking of solid state amps. Not the same thing.

[davemccarthy707]

pull the two outside tubes (on either end) and pull one speaker. Bingo bango bob's your uncle

[dolt45]

Nope, an 85 watt tube amp is an 85 watt tube amp. Double the impedance and it'll sound a little different, you may risk some damage to the output tranny, but you'll still have aprox. 85 watts output.

You're thinking of solid state amps. Not the same thing.

So in the case of a Solid State 1x12 combo ... would my earlier post be correct? Would the speaker & amp itself operate "safely"?

Why would a tube amp be different from a SS in this situation?

[strat a various]

SS, increasing impedance decreases output wattage.
Tube amp has an Output Transformer, sends the same wattage, approx., to the soeakers no matter what the impedance.
You don't want to go too high or low with a SS amp, but most SS guitar amps will tolerate 4, 8, or 16 ohm loads, with corresponding decrease in output wattage.
Tube amps should be matched, in terms of impedance, with speaker loads. Older Fender tube amps usually tolerate a mismatch up or down of one step. For instance, a Bassman wants to see 4 ohms. It will likely survive an 8 ohm load and probably a 2 ohm cab. It's not optimal, it doesn't usually sound as good, and it stresses the amp quite a bit.
This is the nature of the circuits involved. Transistors vs. Tubes. There are a few amp techs around here that can give you the science of AC, DC, Solid State circuits, output trannies, blah blah. Page the local electricians, see if you understand the grim details, it's scientific tech jargon that I don't need to delve into for my day job as a full time player. The techs I work with say this: for tube amps, try to match the impedance amp to speaker.