3dB louder sounds like this
 

A lot of questions come up about the difference in volume between 4 and 8 ohm cabs, or about doubling amplifier power.

A 3dB change sounds like this:

Yup!
 

Or doubling the loudspeaker count, remember those days when that was thought to be an option.
Does your 3dB test include the likely losses from speaker compression, if its all about an increase in power.:bassist:

No speaker compression allowed for, so it's simply a demonstration of the best you can hope for. If speaker compression or amp clipping get in the way then obviously there's even less to gain.

Not worth the extra trip to the car. :D

Exactly. And in the real world, no amp will double its power into a 4 ohm load compared to 8 ohms, so this is a theoretical best case example.

+1 Many amps hover around about a 1.5X power increase from 8 to 4 ohms, which is only about a 2 dB increase in actual volume.

...or the bank!:D

No amp will double its maximum clean power.
For those of us who don't push our amps to the limit, adding a second (identical) speaker cabinet will double both the "power" and SPL at the same control settings.

Err!
 

If ones roadies where to make that extra trip to the vehicle you would have a near 6 dB increase in level.
Unless the trip to the vehicle was to obtain another similar loudspeaker cabinet but of half the nominal impedance, in exchange for the one you
have just instructed to be returned to said vehicle.
So you should have demonstrated 6dB if you want to show what halving the impedance by adding a similar cabinet would do.
All that assumes that one is operating an amplifier that is not properly equipped with output tubes and output matching transformer.
An unfortunate situation that can only be logically explained by a combination of abject fuel poverty, physical impairment and the minimum wage.:D
:bassist:

Well yes, it's obviously the max we're talking about. If you operate your amp well (at least 3dB) below clipping, life is much easier. If you want to double output power, simply turn up the volume. No trips to the car, no extra expenditure.

Again, theoretically but not in the real world.

The point in posting the clip was simply to show how little there is to be gained by doubling output power by whatever means.

I didn't want to do that but it's probably worthwhile. So here's a 6dB change:

And I thank you for that. It's something that many people need to hear for themselves before they'll believe it.

Umm!
 

It's a far more accurate estimation of what most people actually do to half the impedance shown to a Solid State amplifier they already own.
The other 3dB demo would only be relevant to someone buying an amplifier that is twice as powerful, or selecting a cabinet of similar SPL but of half the impedance of the experiments control cabinet, or someone adding another similar cabinet to a tube amp.:bassist:

Then pump this into a loud PA and hear how much difference it makes.
Day and night pretty much, since what counts is power on peaks.

I see a lot of posts from people wondering whether to get a 4 or 8 ohm cabinet and that's what I had in mind when I posted the 3dB example.

It was really just a way of postponing housework :(

My money is on a 6dB difference :)

The perception of 6dB vastly differ depending on volume levels. Just play your clip loudly to understand it.

Dincz, you did a good job in showing how much louder doubling of amp power is. A lot of people still think twice the power is twice as loud.... but that's indeed not the case. Good thread.

True, it also depends a lot on the frequency range.

When I design speakers(especially for hifi) I want the range from 400hz to 6khz as flat as possible, your ear will detect even small variations in this area.

Always misleading when you look at this without context.

Think about 3db as adding a second fridge to an SVT rig:smug:

And, again, for those who have played cabs side by side that are 8 and 4ohm versions, you will realize that the impact of going from 4 ohms to 8ohms ranges from 'doesn't matter' (i.e., if you start with massive wattage at 8ohms, or you are using a small or cheap cab that can't make use of the extra volume), to 'massive' (with massive meaning a bit more volume, and a MUCH more open low end with less compression) if you are using a relatively low powered amp into a moderately efficient cab that can use the extra volume.

There would be VERY little reason to choose an 8ohm cab with a moderate powered solid state head IF the cab can use the extra power and if you are one that never plans to add an extra cab.

These threads make me crazy. IT DEPENDS:smug: