Matching Wattage?

[Taxman]

Hey Audioholics,

I am trying to figure out how to match wattage from receivers to speakers. What I have heard is you want the max watt from your speakers to be equal to or greater from the watts per channel on your receiver, is this correct?

Second question is db (I think this means decibels) when looking at the specifications of a speaker the same thing as the wattage which I am trying to match up?

Third question is kind of an example question, lets say I have 95 watts per channel on my receiver, what do I want my wattage or decibels to be on the speaker for that channel?

Thanks so much everyone!

 

[Haoleb]

DB does mean decibels. On a speaker there are numerous specifications with the db in them, But the two most important are sensitivity which is a measure of how loud a speaker will play when measured at 1 meter with one watt of power. The higher the number the more sensitive the speaker is and the less power it will take to produce high levels of sound. This number does not mean a speaker is better than another because it has a higher or lower sensitivity.

The second big one is frequency response This will usually look something like 32hz-20khz+/- 3db which means that the speaker will play from 32hz to 20khz with a deviation of within plus or minus 3 decibels

Basically, You want as much power as you can afford. So long as it is quality power. It is better to have a speaker rated for 100 watts max and have a 300 watt per channel amplifier hooked up to it for example because it is easier to damage speakers when underpowered and pushed too hard. If you had a speaker that is hard to drive and a very small amplifier you would probably be clipping the amplifier which is sort of like hitting the rev limiter on an engine, this does damage speakers in many cases. There is really no need to match up anything. In the price range your likely shopping in basically anything will work with anything. One thing to keep in mind however is the nominal impedance of a speaker which for our purposes be either 8,6 or 4 ohms. If you do buy a speaker that is 4 ohms you'll need to match that up with your amplifier because many mass market recievers are not designed to properly power a 4 ohm speaker. 8 or 6 ohm speakers should be no problem though.

 

[Taxman]

I am confused about the damaging speakers portion of your reply. Is it easier to damage a 100 watt speaker with a receiver with 300 watts per channel or a receiver with 50 watts per channel.

Also many places I look at speakers don't give the wattage rating only decibel ratings, is there a way to calculate wattage from decibel rating?

Thanks

 

[Haoleb]

Its easier to damage a speaker with an under powered amplifier because of amplifier clipping. When an amp is overdriven it clips which sends a signal to the speakers much like if you were to hook them to a DC power source which damages the voice coils. Mainly in the tweeters because they are the most fragile. With an amplifier with more power than the speaker is rated you run almost no chance of clipping the amplifier and damaging the speaker that way. You can still push the speaker so hard that you'll fry something but most times its at such a volume you would never get to that point with normal use.

I dont know for sure if there is a way to calculate the maximum wattage of a speaker as from what I imagine it all depends on the drivers and how they are wired. But the wattage specification really is not all that important and I would not buy or not buy a speaker based on that specification.

 

[Taxman]

Let's say you have 95 watts per channel on your receiver, what specifications for speakers would you buy to match the receiver? What should I be looking for?

 

[EYEdROP0]

Just make sure your speakers have equal or less wattage rating than you amplifier. Say If your speakers are 700 watt rated and you hook it up to a 100 watt amp, your amplifier will not have enough juice to properly power the speaker, so the amp will start distorting. Distortion is very bad for the speaker because it will heat up the voicecoil much faster than clean sound will. If you had a 700 watt amp with a 100 watt speaker, then the amp wont have any problem powering the speaker. The only way the speaker/amp would blow is if you turn it up to the point that the speaker cant vibrate any harder and it would physically tear. As far as the frequency response, get a speaker that is as close to 20hz-20000KHz -+0 as possible. The higher the sensitiviy rating, the louder it will be for the amount of watts your pushing.

 

[Haoleb]

Let's say you have 95 watts per channel on your receiver, what specifications for speakers would you buy to match the receiver? What should I be looking for?

Like I said you really dont need to be looking at any wattage specification on speakers to "match" it up. Just be sure that the speakers are either 8 or 6 ohm impedance and somewhere around 89db sensitivity or more as a basic guideline.

 

[Haoleb]

Just make sure your speakers have equal or less wattage rating than you amplifier. Say If your speakers are 700 watt rated and you hook it up to a 100 watt amp, your amplifier will not have enough juice to properly power the speaker, so the amp will start distorting.

This is not really true because even though a speaker CAN handle lots of power and play very loudly doesnt mean you need to do that. For example the speakers I have are rated at 400 watts max amplifier power. I know for a fact that they can handle much more than that due to the manufacturers testing, But I have been able to drive them to quite loud levels with as much as only 50 watts. AND they are 4 ohm speakers which means that generally they are harder to drive as they require the amplifier to work harder. The minimum power the manufacturer reccomends for this speaker is 10 watts per channel.

I think your just getting stuck on the wattage ratings a bit too much. If your concerned about matching speakers and amps let us know what your looking at in particular and we can tell you if its a good match or not.

 

[mtrycrafts]

Let's say you have 95 watts per channel on your receiver, what specifications for speakers would you buy to match the receiver? What should I be looking for?

Don't forget, speakers usually come with minimum and max power recommendations. Don't get too bogged down with this. Get a good amp/receiver and don't drive it to the max.

 

[EYEdROP0]

I understand that the important thing is to get good, clean watts out of the amplifier and you should be able to do power a higher watt rated speaker with a good sensitivity just fine. All I was saying is its generally a good rule of thumb to match the watt rating just to be sure its safe to crank it for parties and such (not that I do that, let alone suggest it.)

 

[MDS]

This topic comes up frequently.

It's simple, too much power can blow your speakers and too little power can blow your speakers. A 50 watt amp driven to its limits such that it clips and produces square waves can blow you speakers even if they are rated for 100 wpc. By the same token, a 200 wpc amp driven to its limits so it is actually producing 200 watts can blow the same speakers.

The key is driven to its limits. Speakers can generally handle far more power than they are rated for but the rating wasn't pulled out of thin air. For most receiver/speaker combinations there isn't much to worry about - if the receiver is rated 100 wpc but the speakers are rated 75 wpc it will probably be fine for most cases, unless you insist on running the receiver full out. If you do, then you need a more powerful amp. The receiver will be working overtime to produce its full power whereas a higher power amp will just be cruising along.

It takes surprisingly few watts to achieve very high SPL with a moderately sensitive speaker (say 89 dB or above). It is the peaks that require more power.

 

[fmw]

The purpose of the power rating on the speaker is to tell you the level at which you may be doing damage to the equipment. However, despite, what others say, it is REALLY rare for a home audio user to actually use enough power to damage a well designed speaker. It is possible but not very likely.

It is true that a clipping amplifier can do damage to a voice coil but, again, clipping amplifiers in home audio applications are very rare because most amplifiers are way more powerful than what is actually needed to do the sound reproduction.

As an example, I keep a watt meter attached to one of the main speakers on my A/V system as a monitor. On very loud peaks like explosions in movies, I've seen the watt meter register a little over 20 watts. With dialogue it measures less than one watt. Most speakers have a power rating well beyond that as do most home audio amplifiers.

All these things you read about are really more important in pro audio where it takes massive power to fill large venues with sound. Filling a typical home family room with sound is pretty trivial. My powered mixer puts out 190 watts per channel into 8 ohms and is more than adequate to handle a church or a large hotel meeting room or even something the size of a high school auditorium. I might want to use up to 4 speakers for a high school auditorium but the mixer will handle that with no problem. I wouldn't use home audio speakers with that unit. They aren't tough enough. I use speakers that are designed to handle high power. For larger venues than that, I would need to haul out some seriously powerful amplification and lots of speakers.

I guess all I'm saying is that the power ratings on home audio speakers isn't important as long as you are using them in a home audio application. It might be fair to say that they are there so that some audio jockey doesn't try to fill an auditorium with sound using a pair of home audio book shelf speakers.

The sensitivity rating simply says that the speakers will deliver a test tone of the rated decibel level at a one meter listening distance with a 1 watt input signal. In other words, if I applied a 1000 hz test tone to a speaker rated at 95 db sensitivity with 1 watt of amplifier power, I would hear a 95 db signal at a one meter listening distance. 95 db is pretty loud, by the way. You can see why my A/V system measures well under a 1 watt for dialogue.

I hope this helps put things into perspective.

 

[annunaki]

It's time again ...

OK let's get some of the myths out of the way:

Clipping in and of itself does not blow speakers.

If you play a 25 watt fully clipped signal on a 100 watt rms speaker, it willl sound horrible, but NEVER blow.

Distortion in and of itself does not make voice coild run hotter nor does it cause speaker failure.

The increased power output from clipping induced distortion will increase overall voice coil temperature though.

Too little power cannot blow speakers.

If this were true, every time one turned down the volume the speakers would blow.

Speakers fail for a couple main reasons. Too much power over time (heat), and mechanical failure*.

*99% of the time mechanical failure is cause by too much power, the other 1% is usually a manufacturing defect.


We also need to look at another fact. Amplifiers, when completely clipped DOUBLE their rated output from their .1% thd ratings.

Clipping also introduces odd order peaks of voltage and non-linear frquency response. If the clipped power level is high enough and you have those peaks and such they can/will cause mechanical failure.

As long as the fully clipped signal lies within the speakers "true continuous" power handling capabilities, it will not/should not fail.

Tweeters will fail first when thermal limits are reached/exceeded over too much time. The biggest reason is that they do not travel very far in order to produce enough airflow for cooling like a woofer can. That is why one typically sees ferrofluid or other things used for tweeeter cooling. Thus, their peak power ratings are usually much less than that of a woofer as are their continuous limits.
________________________________________________________________
A big problem is that not all manufacturers have the same idea of what "continuous power handling" should mean.

Some (such as JL Audio) feel that continuous means the rated power for 8 hours straight or more without or prior to thermal failure.

Others feel that it is 1 hour before thermal failure.

Peak power is much worse, because some feel that it should be 3x or 4x continuous handling for 1 mili-second or less. Others feel that it would be 2x the continuous power handling for 1 minute.


As you can see, there are many variables that are introduced.



All that being said, I would match up the power from the amplifier fairly close to the rms/continuous power handling of the speaker for 95% of the users out there. Don't forget that sensitivity & room size/acoustics play in very heavily as well.

 

[yettitheman]

Too little power cannot blow speakers.

If this were true, every time one turned down the volume the speakers would blow.

Shouldn't that be can???

 

[annunaki]

No it should NOT read can.

 

[annunaki]

Shouldn't that be can???

Why do you feel it should read can???

The explanation was underneath. I also explained the effects of clipping in my first post.

I will clarify for you if needed.