Two audio outputs connected without a mixer?

Now consider a fixed speaker impedance and a fixed power supply (battery). Vary the other parameters/devices.

The amplifier fries. Of course you could replace with bigger amps to get that 4x power, but not the most useful comparison imho.

NT

Oh, good grief!

Yes, that is a good way to put it but I didn't feel like explaing it.

In that worst case scenario, the amp with no drive has to pass the current at full rail voltages.

The bonus question is if that is worse than working into a dead short or not. LOL

** A dead short is worse.

Because even a small input signal drives the amp to produce its full available output current.

OTOH, the first scenario is insidious - cos there is clean sound until the un-driven amp overheats and maybe blows.

... Phil

Ok, here is the extra extra credit question Consider two identical amplifiers that can each drive 4 Ohms. Consider 4 identical speakers each 8 Ohms able to handle whatever power you feed them

Which case delivers a higher SPL to the audience?

Case 1 = the two amps bridged driving one speaker.

Case 2 = no bridging, each amp separetly driving two speakers that are connected in parallel , i.e there are 2 pairs of speakers.

Mark

If each gives say 1w, that gives 2w

again 2w delivered.

In both cases the correct phase relationship is required for max SPL. I'm less likely to assume its so in the first case.

NT

But the larger speaker driven cone area would make the two speaker arrangement deliver more SPL.

I dont see how. The speakers would have to be nonlinear to see any difference

NT

Both cases deliver the same electrical power. Case 2 delivers a higher SPL because the

4 speakers form an array which creates a Directional pattern and a higher SPL in the audience And a lower SPL elsewhere. Mark

e ** In both cases, the amp is delivering its full available power.

Sound pressures add linearly, so four in-phase sources produce 4 times the SPL of one or 12dB more.

Sound pressure is proportional to applied voltage also, the array is being driven with only half the voltage of the single speaker so 6dB less.

The array is 6dB louder, on axis, at any frequency where the speakers are i n phase at the listening/measuring point.

At high input power, the single speaker is even worse off, since its voice coil will heat far more, raising the resistance and lowering current flow. You can lose up to 3dB this way. PLUS the magnet structure tends to demagne tise at high power and this happens instantly, so you lose a few more dBs.

... Phil

The biggest woofer ends up limited by unsprung weight, right?

That is why they can only be up to a certain size. There are no WALL sized woofers that operate with any proper efficiency or sonic linearity. We have already perfected the woofer cone size and shape (all but perfected).

What is the biggest? Like 18" and even that is questionable. The most efficient live cabinets held 12 and 15 inch arrays, no?

So, back to the problem. Is there more sound pressure? Your remark about adding linearly is true, but the transition level for each is less.

The same base power figure pumped into (spread across) four voice coils would also, linearly, make them transit one fourth of the movement of the single coil transducer with the same base power figure.

The four cones would also then travel one fourth the distance.

So, it *should* be the same in the end.

Still, as you state, the larger surface area of four cones travelling one fourth as far may still yield more SPL than a single cone driven to the full throw.

The guy with the "field effect" answer might have had something too.

Placement of the speakers will fool a human listener, but SPL is a transducer measured parameter.

So, did you get it right in review, Phil? Or did I catch something? I think another poster said they would be the same too.

I had a very old juke box speaker from the '50s, I believe. It had a magnet, but also had two voice coils and a third coil around the magnet to boost it with DC apparently.

I never used that part. It was a 15" driver. I wish I still had it, because it would be a valuable antique by now, I am certain.

My dad had it mounted inside his 10 foot bar down in the "family room". Now I know why I like pool and beer and bars and juke boxes. We had an old upright piano in there for a while too. The guy next door played old saloon songs on it. It was pretty wild seeing them. My dad played drums with a pianist gal on Fridays and Saturdays.

I did not like that stuff he played then, but love it now. Weird.

** Nonsense.

The biggest woofers I know of are electrostatic, with diaphragms that weigh SFA.

** Huh? ** Wrong. You need to read my reply again.

** Of course I did.

... Phil

That 3rd winding would be a humbucking coil

NT

snip

My response:

First phrase in Deliverance on the Banjo. (phonetically of course)

Brahh dahh dahh dahh dahh...

** Bollocks.

Electrodynamic speakers were still made in the 1950s and a hum component in the DC current in the energising coil does NOT produce hum from the speaker.

.... Phil

I didnt claim it did.

NT

Sounds like you have a COE problem, to me.