Can someone explain to me how to match amps and loudspeakers?

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whattaguy

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I know that you would want the power amp and the speakers to somewhat match in impedance and wattage (erring on the side of more for the speakers), but what happens when you bridge an amp, or run speakers in parallel?

For example, I have a speaker with these specs:

Frequency range: 52Hz - 20k Hz
Frequency response: 65Hz - 20k Hz
Sensitivity: 98dB SPL
Nominal impedance: 8 ohms
Power capacity: 400 W / 800 W / 1600 W
Rated maximum SPL: 124 dB SPL continuous (130 dB SPL peak)

How would I read that and choose the correct power amp?

What if I wanted to go 2 speakers on each side, how would I choose my power amps?

Thanks.
 
Generally speaking, I would reccomend 2 to 3 times the power in an amp then the speakers program rating. In this case you would be looking at a 1600 to 2400 watt amp. Especailly if you are looking at lower end (i.e. cheaper amps). If you get into a more efficient and/or higher quality amp you can play around with those numbers a lot more. Better amps will handle peaks and clips better and won't DC on you nearly as easily and will offer your speakers much better protection. If you want a good compromise between price, output power, perceived output, and durability, feel free to shoot me a PM concerning the FACE audio amplifiers. I have racks of them that have been heavily abused and they all still kick ass. They never even get warm, even when running near clip for hours on end in the direct sunlight. They come in a little under a grand. The drawback? Heavy as all get out....
 
xstatic said:
Generally speaking, I would reccomend 2 to 3 times the power in an amp then the speakers program rating. In this case you would be looking at a 1600 to 2400 watt amp. Especailly if you are looking at lower end (i.e. cheaper amps). If you get into a more efficient and/or higher quality amp you can play around with those numbers a lot more. Better amps will handle peaks and clips better and won't DC on you nearly as easily and will offer your speakers much better protection. If you want a good compromise between price, output power, perceived output, and durability, feel free to shoot me a PM concerning the FACE audio amplifiers. I have racks of them that have been heavily abused and they all still kick ass. They never even get warm, even when running near clip for hours on end in the direct sunlight. They come in a little under a grand. The drawback? Heavy as all get out....
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Thanks...I know this discussion has gone on before. But I've read in the Yamaha Sound Reinforcement book that you would ideally want the amp to be about 1/2 that of the speakers' peak wattage because of clipping. The guide said that when an amp clips, it puts out about twice the amount of power to your speakers. This sounds opposite to what you are saying.

Also, what happens when I daisy chain monitors? Is that a series or parallel connection? Thanks.
 
First off, daisy chaining speakers is parallel. As a result, if you plug one 8 ohm monitor into another 8 ohm monitor, you get a 4 ohm load. As for the amp, something sounds screwy there. Any chance you misread it? What you said is the opposite of what i did, but your explanation backs my suggestion up as opposed to what the handbook says.

By having an amp half the power of a speakers peak wattage what you are actually doing is INCREASING your chance of cliiping the amp and sending DC, square wave, or just flat out bad signal that tends to wreak havoc on a speaker. After re-reading I now see what the argument they are making in the yamaha handbook is. However, it seems like really bad advice to me. Clipping an amp is one of the best ways to blow a speaker. Having too small of an amp is a great way to push the user towards clipping them amp. Having too large of one generally gives you audible warnings of problems to come. Personally, I feel that the yamaha suggestion is not only wrong, but quite possibly bad advice. What I am speaking from is 10 years experience running a live production company and working for a few others. This is how we do our amps and it is fairly rare that we blow drivers. Generally if and when we do, there is a reason that directly relates to some sort of user error. I have no doubt that if we were to cut all our amps down to 25% of their current power ratings like the yamah book describes that we would have a great number of issues.
 
xstatic said:
First off, daisy chaining speakers is parallel. As a result, if you plug one 8 ohm monitor into another 8 ohm monitor, you get a 4 ohm load. As for the amp, something sounds screwy there. Any chance you misread it? What you said is the opposite of what i did, but your explanation backs my suggestion up as opposed to what the handbook says.

By having an amp half the power of a speakers peak wattage what you are actually doing is INCREASING your chance of cliiping the amp and sending DC, square wave, or just flat out bad signal that tends to wreak havoc on a speaker. After re-reading I now see what the argument they are making in the yamaha handbook is. However, it seems like really bad advice to me. Clipping an amp is one of the best ways to blow a speaker. Having too small of an amp is a great way to push the user towards clipping them amp. Having too large of one generally gives you audible warnings of problems to come. Personally, I feel that the yamaha suggestion is not only wrong, but quite possibly bad advice. What I am speaking from is 10 years experience running a live production company and working for a few others. This is how we do our amps and it is fairly rare that we blow drivers. Generally if and when we do, there is a reason that directly relates to some sort of user error. I have no doubt that if we were to cut all our amps down to 25% of their current power ratings like the yamah book describes that we would have a great number of issues.
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Thanks xstatic! In most cases, I will go by real-world application. I'm just giving a small seminar to some youth on live sound tomorrow, but I must confess that my theory on amps and speakers is not too great. The system I mix on is already set-up and I had no say in it. Thanks a bunch!
 
man not to rag on you but if you dont understand this you should be taking the seminar not giving it...
 
dementedchord said:
man not to rag on you but if you dont understand this you should be taking the seminar not giving it...
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That's fine. Thanks for your honesty, but it seems like there are two sides to this issue. Some say "Yamaha" that the amp's wattage should be half that of the speaker max output, and some say the exact opposite in real world situations.

This isn't a high-tech seminar with a bunch of know-how's, but a basic seminar for church youth students who mostly have systems already purchased. I'm not going to lie to them saying that I'm a pro...in fact I'm far from it.

Thanks for your constructive criticism, though. Really.
 
well consider this.... years ago manufacturers were engaged in a power/$ war... and aloyta the lower end guys needed a way to elevate the perception of their offerings... that's when we started to see all manor of rateings... ie.peak power... music power... whaile working in the car stereo biz i wuth some freinds proffered the ISL rateing for those boomer car systems... it stood for "if struck by lightening" yes it might actually do 1killowatts for that breif second... through all of this though there was already in place a system that worked... RMS... root mean squared... kinda confusing even to some studied individuals but there it is... so i offer two suggestions...

1) if the spec sheet doesnt show the rms #'s atleast suspect and possibly avoid that companies wares...

2) the ideal for amp power should be @ 2X's the speakers rateing (again in rms)


now does that mean ya cant use a lesser amp??? no of course you can... however it does mean that the likelyhood of toasting the speakers (and in some cases the amp) goes way up... my rule of thumb was always if ya need to open the amp up beyond 75% to achieve desired levels you've got the wrong amp the other 25% is whats refered to as headroom...
 
Last night I was compiling a bunch of manuals and spec sheets for a 10 day festival gig I am doing in January. For fun I took a look at the L-Acoustic specs as I was downloading them. On the dV-Dosc specs they list reccomended amplifier power as double the RMS of each driver. I can't think of a more reputable speaker company out there so if they say 2x, then thats definately what I would go with :)
 
xstatic said:
Last night I was compiling a bunch of manuals and spec sheets for a 10 day festival gig I am doing in January. For fun I took a look at the L-Acoustic specs as I was downloading them. On the dV-Dosc specs they list reccomended amplifier power as double the RMS of each driver. I can't think of a more reputable speaker company out there so if they say 2x, then thats definately what I would go with :)
Click to expand...

Thanks for all your help!
 
What exactly happens when an amp clips?
Is it too much in or too much out or both?
 
when an amp clips you are literally running up against the power supply rails... the signal flattens out and it sounds like shit as well as running the chance of toasting the speakers... there are two ways of thinking of this... one side says it's the full excursion added to the bits of movement caused by constantly going over/under the rails that burns them... the other says that it's the lack of movement as it hits it's extremem that doesn't allow the driver to cool... which is right??? i suspect it's the second but who cares??? either way your fuked...
 
It seems there's already a consensus here (correctly so), but I just thought I'd add this little ditty. Years ago a friend and I were goofing around in my electronics shop with some 6X9 car speakers that were laying around. We hooked up one side of a pro amp rated at 400W/Channel at 8 ohms to a speaker. The speaker ran fine with the amp wide open for at least 10 minutes. We could not blow it up and not for lack of trying. We then swapped out the amp with one rated at near the speaker's rating (around 100W). The speaker lasted about 2 minutes 'till smoke at a lower volume. It was surprising how much power the speaker would take as long as the output was clean and not clipped.
 
MONTE said:
It was surprising how much power the speaker would take as long as the output was clean and not clipped.
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For years I've been poking 250 watts into a pair of 50 watt wedges with no problems.

And a friend of mine has been driving a pair of 100 watt EVs with an Aussie Monitor 1600 Watt amp.
 
Keep in mind not to just look at the power of an amp, but the power per channel at the impedence you will be using it at. I see musicians and stuff constantly not paying attention tho this. For example they go into a store and they buy a 1200 watt amp to drive a pair of speakers. What they don't take into account is that when they were told that the amp was 1200 watts that the 1200 watts was the max power output at 4 ohms bridged. If they were running two speakers off of that same amp on seperate channels assuming a lod of 8 ohms per speaker, the real ouput of that amp may actually only 250 watts or so per channel.
 
To calculate the resistance in OHM's for two speakers wired in parallel, it is Speaker A x Speaker B/Speaker A + Speaker B. IE: 8x8=64/8+8=16 64/16=4

For series wiring, you simply add the impedance values together.

Clipping (distortion) will kill a speaker MUCH faster than over powering will. This commonly happens when a speaker is driven with to small of an amp.
 
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