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The issue of 'Average' (ACP) power and 'Peak' (PP) power is significant.

Average power is limited by how much heat the amp can dissipate. Peak power is limited by how much current the power supply can provide. The difference is called 'Headroom'.

3dB of headroom at the bare minimum, means 9 Watts ACP becomes 18 Watts PP.
6dB of headroom means 9 Watts ACP becomes 36 Watts PP.
A jazz or rock concert using 24dB headroom means 9 Watts ACP becomes 2261 Watts PP.

Incidentally, touring company stadium style rock concerts can use 80,000 to 400,000 Watts to handle the 24dB peaks.

That sounds like a lot, but that 80,000 Watts is only 40dB above 9 Watts. A standard CD can produce up to a 96dB dynamic range.

Thanks

One of the new things in our google world is going on forums to get answers; the problem is, if you don’t know something, a person looking for answers, many times, can attribute to incorrect answers the same consideration they give to correct ones.

It's true what you wrote. Over here ----- we just get used to saying 'handle' ---- as in to deal with, without getting issues. I mentioned that it had to be based on assumptions - as we don't know the specs of the amplifier. I support your assumptions.


I should have just written 10W rated power for each speaker ---- based on the OP's information.

We know that the sound system designs typically take into account the speaker's power rating - so that nothing bad (undesirable) happens when the end-user slides/turns the volume control to maximum ---- for cases where the speaker power rating is significantly smaller than the amplifier's maximum deliverable amount of power.

Assuming power is not a limitation for a particular amplifier ------ over-driving a speaker can be a problem when we want linear operation. Assuming that the speaker isn't driven to the point of destruction.

But - on the other hand - if an amplifier is designed to have a particular maximum output power, and we decide to add speakers that have much higher power rating than the maximum designed power output of the amplifier ----- and assuming that we don't exceed that maximum output power from the amplifier ........ then we probably won't get our money's worth from the speakers (performance-wise).

It's true, if you buy a speaker capable of handling 50 watts to use with a 5 watt amplifier (or whatever), you're probably not getting your money's worth out of the speaker. But you won't damage anything.

The most efficient speaker that I've ever seen, bar none, is the Altec A7. They are long discontinued but if you find one you can hook up a small transistor radio (ipod, whatever) directly to it and fill a large room with excellent sound.

They aren't what you'd call pretty, they're heavy and take up a lot of room, but they are a truly amazing speaker.

Totally agree with you scott. And the 5W amplifier might not be able to drive the speaker too well --- as in getting much decent volume or performance out of it. At least won't damage anything --- true!

As others have mentioned before - that's a dangerous overgeneralization.

The speaker's resistance ratings (Ohm) influences on how it interacts with the amplifier. If the keyboard in question was designed for and built with 8 Ohm speakers and you replace them with 4 Ohm or even 2 Ohm speakers, they could very well lead to overheating other otherwise damaging the integrated amp because while using the same driving voltage, the speaker will draw a much higher current.

Like I said, "All else being equal, putting in the 50 watt speaker is not risky to the speaker, which, if it can take 50 watts, can certainly take 9. nor is it risky to the amplifier." That means, I was talking in the context of using a speaker of the same impedance. I've already posted about the importance of making sure you don't go down in impedance unless you're certain the amp is designed for it. I can't repeat every point in every post!

To add yet one more layer of complexity:

The word 'speaker' and the word 'driver' have distinct meanings in the audio world.

A speaker is a complete structure that houses the drivers and crossover networks, if any.

A driver's efficiency is measured in an anechoic chamber, not in the DP's cabinet.
A DP's in situ speaker output efficiency could be measured in the same way, but the results will not likely be the same.

Correction. I keep saying 'efficiency' when I mean 'sensitivity'. Huge difference.

Thank you guys all for weighing in on my query.. !!!

From the original post we have 9W power consumption of the piano which equates to 'roughly' around 9W at the speaker/driver.

Being stereo, then that will be 4.5W output per channel (9W/2 channels) at an impedance load of 6 ohms. At this point I realized the amp cannot generate any more watts than that.

So each speaker should be able to take maximum input of 4.5W

*for the sake of discussion, let impedance=resistance

Going back to the power formula

P=VI where V= IR

then

P= (I^2)R

We know that the Power Output is constant. So when we lower the impedance, the will be more current flowing under the same watts or power

I = square root of (P/R)

This translates to more heat on the system.. and it is not an option...
Hence changing the built-in speakers won't work.

Yes, a lot of details have been left out to drive the discussion towards the amp/impedance of the piano/speakers. And a lot of those details have been provided relevant to it. Thanks for all your responses...even the long ones, i've read all of them.
Btw, I've also always maintained that i have no budget/out of budget for a powered monitors or for an active speaker or for a PA.

The space is two car lengths, and can only fit two cars and perhaps two motorcycles parked parallel to the bumpers.
With people talking and milling about I guess I'll have to make do with the PA system on the venue. The one that sucks because of a persistent echo.

Or maybe 3 pairs of these will do? at 3W each,

It's hard to say what the 9W is at the moment, especially if the manual really is putting this value under the 'speakers' section (referring to the original post that is).

The original post indicates 10W for each speaker ..... so each amplifier section is expected to deliver at most 10W average power to one speaker.

So ---- just hypothetically (and ideally) --- if each of the amplifier sections (left and right channel) each happen to be outputting 10W ----- then the digital piano power consumption would be 20 watt, plus whatever other amount of power it consumes when there is no sound coming out from the speakers.

What brand/model instrument have you got there? Maybe mentioned before already - I'll check to see if it has been mentioned, after flicking through the thread a bit more.

I am afraid that is not how it works.

Your formulae are correct, but P does not generate (I^2)R, P is the result of (V^2)/R, so changing R must change P. Power is not constant.

If I halve my speaker impedance, they will absorb twice as much power from the amplifier.

If the amplifier can accept the load, all is well. If it cannot, one of the things I mentioned at the beginning of this thread will occur.

Solid state amplifiers have a very low (0.1 Ohm or less) output impedance. They are simply current sinks. The power output is determined by the speaker impedance. Lower impedance speakers means more power output.

The result is one of several things:

The power supply can't sink the amount of current requested by the speakers and the voltage sags, the current drops, and the amp distorts.

The power supply can't sink the amount of current requested and blows a fuse.

The amplifier happily sinks the desired current and the sound is louder.

The amplifier unhappily sinks the requested current and melts.

I wouldn't assume that. For one thing, as alluded to earlier, even a piano with no speakers has some power consumption, so 9w is not merely the power consumption of the amplifier that is driving the speakers. But more than that, as described in the article I linked to, power consumption is rated different ways. And so the piano's 9 watt power consumption figure does not necessarily correspond to its maximum power consumption, nor does its power consumption directly tell you what an amp is capable of sending to attached speakers. It's certainly possible that the speakers are getting more than 4.5 watts. But presumably under 10, since that's the most that the speaker is rated for, and a manufacturer wouldn't want to include an amp that could too easily blow the speakers.

The amount of watts an amp can generate at a given impedance is fixed, of course. At a given impedance, the only way to get "more watts" is to replace the amplifier, not the speaker (though you still have to be sure you're not sending the speaker more watts than it can handle... then you'd have to replace the amplifier AND the speaker). But that doesn't mean it's impossible to get more volume through a speaker change. At the same impedance, a more efficient speaker will give you more volume from the same watts. Getting back to my earlier comment, if you were going to do this, that is the way to do it. Forget watts. Just try the most efficient speaker you can find that will fit into the same enclosure.

It also is sometimes possible to "get more watts" out of an amp by using a lower impedance speakers, but that won't necessarily give you any more volume, because again, it depend on the efficiency of the particular speakers, but also, as you said Right. if you're not sure the amp can handle the lower impedance, you wouldn't want to try it, the amp can overheat and fail.

PAs don't have echo unless someone intentionally adds it as an effect. If it's not an intentional effect, then it's not that the PA has an echo, it's that the room does.

Adding any external speakers is a safer, more predictable approach than changing the internal speakers, and easier to just pack up and return if they're not satisfying! What is your budget for something external? I know, you say you have no budget, but nobody was giving you replacement internal speakers for free, were they? There is SOME amount you can spend here, minimal as it may be. Maybe you'll find something suitable in an external. Don't focus on watts! See if there's an SPL spec, that's much more meaningful, when you're talking about self-contained powered speakers.

No. Like I said in #Post3200669 My amp cannot generate more power. So Power is constant here.
So changing R will change I.

[quote=prout]but P does not generate (I^2)R,[quote]" this is your interpretation, i never said or implied such. you can read again my full statement in context in #Post3200669

oh, no. the persistent echo is confirmed on the PA not the room.

Thanks for the input.

No. Like I said in #Post3200669 My amp cannot generate more power. So Power is constant here.
So changing R will change I.

Josh, your amp may not be able to supply more power. I agree completely with you and this is what I have been implying all along. What I am trying to say is that your amplifier does not sit there and generate a constant power output which has to go somewhere. It only supplies what your load asks for.

I don't interpret electronics formulae. They are mathematical constructs that are either correct or incorrect. In the examples I have given above, they are correct. I design and build this stuff from scratch. Give me a break. You don't know what you are talking about.

If you are not interested in the physics of speakers, just say so, and I will bow out. I thought, given the constant stream of misinformation about basic electronics on PW, I might be able to clear some things up. Obviously not. Sorry to bother you.

Using an RMS voltage multimeter could most likely help provide some indication about how much power is delivered by each channel of the amplifier module ---- such as by measuring the RMS voltage across the speaker terminals ---- such as when the 'C' key is played. Sure - the C sound will drop away after a while. But maybe enough time to get some idea. And maybe could then estimate the power under max conditions. This is to see if the maximum amplifier power for 1 channel is 4.5 W ..... or if it is 10 W.