Watts up?

  

I have never been able to grasp the concept of amp wattage and speaker wattage even though I've had it explained to me several times with the "garden hose" comparison.

 
Ok. Let's forget garden hoses and look at practical matters.

Let's say my amp puts out 100 watts per channel. 

 
 
OK. Valve or solid state amp?
 

If I connect a 50 watt speaker to one of the channels of the amp then I risk blowing the speaker.

 
 
It's possible to blow a 100watt speaker using a 50watt amp as well :-)
 
If you crank an amp hard enough to make the signal clip badly it's quite capable of burning out speakers that are theoretically more than powerful enough. Clipping produces compressed square waves, and tweeters in particular don't like big, powerful square waves.
 
Guitar amps and speakers are a different matter - they have their own peculiarities. The amps are generally designed to distort, and good guitar speakers are designed to take it.
 
In the PA and hi-fi worlds it's quite common to use amps that are rated at up to twice the power handling of the speakers. The idea is that the setup provides ample volume without the amp ever even approaching flat out - which leads to a cleaner signal from the amp with less compression and distortion going on.

If I connect a 150 watt speaker to one of the channels of the amp then I risk blowing the amp.

 
 
No. Not unless the impedance of the attached speakers is outside the range the amp can handle. Valve amps are paticularly sensitive in this way. What can kill amps are "open" circuits (no speaker connected) with valve amps, and short circuited speaker leads can kill transistor amps in under a second. 
 

What happens if I "daisy chain" two 50 watt speakers to one of the channels of the 100 watts per channel amp? Would this be the equivilant to connecting one 100 watt speaker?

 
 
Kind of, yes. What happens at the amp end depends on whether you connect the speakers in (electrical) parallel or series.
 
Let's say you have two 50 watt cabs rated at 8ohms each, and a simple 100 watt mono amp with one set of speaker connections. Connected in parallel, that will give 100 watts at a loading of 4 ohms. Which will mean the amp actually now produces something more like 140-160watts.
 
Conected in series, the loading will become 16 ohms, which means the amp's power output will drop some.
  
If the amp has different outputs for different speaker loads, in which case just hook the 4ohm load to the 4ohm output or the 16ohm to the 16ohm output and you'll generally get the rated power.

Hope someone can help me with this.

 
It's a big subject that can be very simple or very complicated depending on what you're trying to achieve :-)
 
It doesn't help matters that the power figures given by manufacturers, especially in the "consumer sector" are often pretty meaningless. "RMS watts at x% distortion" has meaning. Things like "Maximum Music Power" or "Peak Power" generally mean the advertising department has been looking for a way to put as big a number as possible before the word "watts"....

 
So. What exactly are you thinking of doing?

It's not only going to be a difference with speakers, tho Pete.  Home theater amps are heavily processed.  most of them the processing can be adjusted, EQ, compression/expansion, aural exiters, etc are often even part of the default sound of the amp and they can usually be tweaked from there.

check your amp on your motif and see what settings you have on it.

Pete you got some good advice from tlw. 

On speakers, generally the larger the voice coil and the heavier the magnet, the more abuse a speaker can take without "blowing" .

Several things can happen to "blow" a speaker. The common things are the power applied exceeds the ability of the speaker to cool the voice coil, and the voice coil either warps or the wire in the coli actually burns in two. A warped coil will rub causing a scratching noise, after it rubs long enough it will eventually fail due to an open, and the speaker will cease to function. The burnt wire does the same thing instantly. 

A cone can be ripped or cracked by the vibration and that will also cause a failure. 

The easy way (rule of thumb) to figure combined speaker impedance is: if the wiring is in series, simply add the impedance of all the speakers wired in series.... for example, 2  eight oms in series is 16 ohms load. 
Those same 2 speakers wired parallel would be half the load...or 8 ohms divided by 2 speakers (of the same load) equals 4 ohms.  If you had 4 speaks of 8 ohms each... 8 ohms divided by 4 speakers in parallel would be a 2 ohm load. 

If you google "ohms law for speaker loads" I'm sure you can find the sites that explain the math behind the numbers.  Math will make it very clear what is happening. 

The solid state amps are more susceptible to damage from low loads than tube amps, but always try to run any amp at it's nameplate rated load.

The power (that's what a watt is, a measure of power) that gets transferred to the load is the most efficient at the rated load.  

As far as home surround sound systems, and how they sound..... yeah, they are made to sound a certain way. So when you buy one model, it will sound different from a similar model from a different manufacturer. The circuitry is intentionally made to sound a certain way....more bass, more highs, it's their signature sound in many cases. 

So, back to speakers for a minute. Most monitor amps and surround sound amps are solid state. So you need to look at the nameplate and if it says 8 ohms, and nothing else, be sure the load is 8 ohms. That way, you can crank the volume up as loud as you can stand it and the amp is seeing the 8 ohm load. The 8 ohms will only allow a certain level of current to flow through the coil. A lower load offers LESS resistance and as a result, MORE current flows, and more current means more heat is generated in the coil which has a limited ability to dissipate the heat, and damage can occur to the speaker. IN addition, the heat sinked output transistors are also rated to a certain level of current and heat. Heat will destroy the output transistors if the heat created there can not be dissipated quickly. So you have possible destruction happening on both ends of the chain.... whichever one is the weaker will blow first. 

Having said that.... you can run a 2 ohm load on an 8 ohm solid state amp...BUT with extreme caution. Since the current and heat are a direct result of the overall volume level, it would be critical to keep the volume low, and only do this for a short period of time where YOU are the only one with hands on the knobs. This is not something I would recommend at all for general use. In a band, we have had to do this a time or two when one amp in the PA blew out, and we needed to double up on the bass bins, effectively halving the load and running the amps into the danger zone as far as the load. We placed fans on the amp (the big box fans) and played the gig with our fingers crossed.   Many of the big power amps are built to handle the low, heavy loads because the manufacturers know what happens in the clubs.   I heard of one band who blew their entire power amp rack by plugging it in to 240v by mistake. They ran the entire PA on one Crown, hung between 2 chairs with rope, covers off, and 2 fans blowing on it... the amp held all night long. The guitarist said he could have lit a cigarette off the cooling fins (not literally) because it was as hot as a firecracker. 

hope this helps..... stick to the nameplate loads, understand the ohms law on speakers and you'll be OK. 



EDIT: running a 100w amp into a 50w speaker is safer (generally ) than the opposite. If a low power amp is clipping it's signal.... during that time of clipping, you are running pure DC current through the voice coil. It becomes essentially a heating coil.  So a lower wattage amp can and will burn out a higher rated speaker in that manner through it's inability to drive the speaker efficiently.

I have played (guitar) into an amp that was over rated for the speaker.. 100w into a 50w speaker ...and never blew it out.  I have also replaced several speakers in a 50w amp that had a speaker rated at 70w.  (that was a kickin little Carvin I used to have. after the last replacement, I stopped using the internal speaker on stage)

We also had some 12" Electro-Voice speakers with 17 pound magnets..... yeah the speaker magnets were almost bigger than the speakers.... In our bass bin cabinets.... I think they were 100w rated to 200w peak..... we ran 200w RMS at the rated load (400w peak) from the power amps. So we were running twice the rated power into the speakers all night long, at bass frequencies. We never blew any of those 4 speakers during the entire time we had them. Standing in front of the cabs during a show, with the kick drum, you could make a flame dance on a lighter. Note: we also had a limiter/compressor on our entire system. 

NO! that will result in a load of 2.6 ohms. That is well below the amp output rating of 8 ohms.

this statement: The amp's channel is only capable of 8 ohms and therefore the 24 ohm demand from the 3 speakers might damage the amp.
 
would only apply if the speakers were in series.... but is also wrong.... the amps channel is CAPABLE of delivering 130 watts IF the load is 8 ohms. The amp heat sink and transistors are only capable of handling THAT load scenario.

You would be better off the use only ONE of those speakers...... unless you have one more 8 ohm speaker for a total of 4 speakers..... you can connect 4 of them so that they are still seen by the amp as ONE 8 ohm load, that will then be able to handle the total power the amp delivers with ease.

Simplified:

The Wattage rating on an amp is the MAXIMUM power it can DELIVER, not the power it always delivers. If you don't turn it up all the way, it'll put out less.

The Wattage rating on a speaker is the maximum it should RECEIVE.

The Impedance rating on an amp is the MINIMUM impedance that should be hooked up. Higher is always OK, but it will not be able to put out as much power and efficiency will go down, but again it's always OK.

The impedance rating on a speaker is fixed, but as explained when you hook up multiple speakers in series or parallel, there are formulas to calculate the result. You should NEVER hook up a speaker system with lower impedance than the MINIMUM your amp is rated for. Higher is always safe.

R

 
Thanks so much to everyone who contributed to this thread.
 
Thanks to each one of your posts I was able to get a slight grasp on what it's all about. It's really quite complex. One of those situations where the high numbers mean less and the low numbers mean more. Kind of like gauging metal thickness where the lower the number the thicker the metal. It's kind of mind blowing.
 
I have been playing with the EQ settings on the amp and it sounds best with a flat frequency setting while in stereo mode although I'm still not happy with the sound of the speakers.
 
The electric piano had speakers in it when I bought it and I think I'll use some of those to replace the least desired speakers that came with the amp.
 
All the speakers in the piano are 8 ohm speakers.
 
There's two 8" woofers rated at 70 watts each.
There's two 1" dome tweeters rated at 100 watts each.
 
These two sets of speakers can be used for 4 of the channels and I'll use the 2 front main speakers that came with the amp for the remaining 2 channels. The subwoofer of course is on a channel by itself. It's a 6.1 system.
 
I think the combination of these speakers will fill out the frequency spectrum quite nicely. The four speakers that came with the piano are already installed into the piano and will be easy to connect to the amp, which means that all I'll have to do is mount 2 speakers that came with the amp into the piano and all speakers will then be concealed within the piano with some facing down at the floor and some facing up toward the ceiling. This should provide a very realistic sound coming from the piano.
 
It really is a very pretty piano that I picked up from craigslist for 100 bucks. It's a Baldwin Pianovelle GPS2500. It's an electric piano with graded hammer keyboard that is set into a beautiful black lacquer baby grand piano body. There's something wrong with the motherboard and the sounds don't work on the piano but it still functions perfectly as a midi controller.
 
I've connected my laptop to the piano and I use Sonar with a GPO plug-in. This plug-in has a very nice sounding Steinwway that I'm using for this keyboard.
 
Not a bad deal for 100 bucks plus the 150 bucks I just paid for the surround sound system.
 
Anyway, thanks to all of you for your input and help. It is much appreciated.
 
Pete
 

 
For those that are interested here's a picture of my new 100 dollar piano. It's extrememly heavy and I nearly broke my back getting into my house even though I had someone helping me. Of course I had to break it down to move it but it's all together again now.
 

That's a cool mod.
Do the pedals work?

Yup, everything works but only as a midi controller. The motherboard inside the piano needs to be replaced in order to get the audio to work. In addition the display screen needs to be replaced so I can't use the onboard sequencer.
 
So basically it's just a midi controller inside the body of a beautiful, full sized baby grand piano, which is fine for me because I just want to use it as a piano anyway. I have a Motif ES8 that I use in my studio. This is just a piano that I want to place in our formal living room that I can play just for fun and I couldn't pass it up for only 100 bucks. The piano still has the original price tag of $8,000.00 still stuck on it.