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Matching speakers with AVR or AMP power

post #1 of 10
2/15/13 at 4:25pm
Thread Starter 
Hi,

I have been lurking this formun for a good year now. I have been doing some research because im interested in building my own HT when the time is right.

I have read so many threads on forums, online magazine articles and blogs to become even more confused about a very simple but important subject.

How to match speaker power with amp power??

I understand about matching the ohms but some webpages say that your amp power should be 10 to 50 % higher than the specs of the speaker so that the amp is not overworked, others say that doing that will fry the speakers so the speakers rated wattage should be 50% higher than the amp output. Those to statements are the complete opposite.

Im not looking to become an expert, just to know some basic rules of thumbs to help me make a decision.

Thanks for your help
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post #2 of 10
2/15/13 at 6:03pm
Speakers are damaged by not having enough power. The amount of power required depends upon the load the load the speakers present (e.g. 2 ohms, 4 ohms, 6, ohms, 8 ohms, etc. which is variable) and the efficiency of the speakers (e.g. 86 db, 89db, 92db, etc.). Also, generally speaking it requires more power to drive a floorstanding speaker with many large drivers than a bookshelf with a small driver, even though the latter is usually rated at a higher efficiency. Purchase your speakers first and match you amp or AVR to them.
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post #3 of 10
2/15/13 at 8:45pm
Thread Starter 
Thanks for your reply but it still not clear for me. Is there a formula to determine what you are saying?

Say i have LCR speakers with this specs:

8 ohm load
sensitivity 93/90dB (room/anehoic)
Maximum imput power 140 watts

This are the specs of a floorstanding Paradigm SE 3 speaker.


What would be the correct power amp to use in this case?

The spec sheet also says Suitable amplifier Power Range 15-200 watts

But why?

Why 15 to 200? it is a very big diference. Does it has something to do with the desired SPL db at the listening distance? or something like that?

Thanks again
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post #4 of 10
2/15/13 at 9:45pm
Quote:
Originally Posted by justindo View Post

Speakers are damaged by not having enough power.

True - in a manner of speaking. I'm sure you meant that driving speakers hard with an underpowered amp is what will kill the speakers.

Quote:
Originally Posted by Completenewby View Post

Thanks for your reply but it still not clear for me. Is there a formula to determine what you are saying?

Say i have LCR speakers with this specs:

8 ohm load
sensitivity 93/90dB (room/anehoic)
Maximum imput power 140 watts

This are the specs of a floorstanding Paradigm SE 3 speaker.


What would be the correct power amp to use in this case?

The spec sheet also says Suitable amplifier Power Range 15-200 watts

But why?

Why 15 to 200? it is a very big diference. Does it has something to do with the desired SPL db at the listening distance? or something like that?

Thanks again

If I were going to use those speakers near field like computer speakers I sure wouldn't need 200wpc to drive them. Conversely putting those speakers in a very large room and sitting back 20' I would need more than the minimum wattage the speaker manufacturer recommends.

The difference between an amp/receiver that delivers 10wpc vs 100wpc or 15wpc vs 200wpc isn't the wide gulf it might look like on paper. Check out this link on Crown Audio's site. Play around with that calculator. It'll give you specifics on how much power you need for those speakers. Note that as the db level goes up the power levels climb fast. Faster than the sound levels.

I plugged in your speakers' specs into that calculator at 85db and 3 meters sitting distance with 6db headroom for the amp. It takes 6 watts to play them at 85db - AKA - reference level. Up the db level to 100db to account for very loud and fast transient sounds and 6db of headroom and now you need 100 watts. Speakers with 90db efficiency would need 358 watts to satisfy the 100db SPL while maintaining 6db of headroom. Drop the headroom requirement to 3db and now you only need 180 watts. While most AVRs can accommodate that transient sound it probably won't do it without clipping. They just don't have the capacitance.

Having said that a few questions - how large is your listening space? Ceiling height? How loud do you play music or movies? The answers will give you a ballpark figure for your power needs. Unless you listen at very high levels you might be surprised by how few watts you really need. No need to match the amp to the speakers other than impedance requirements. Mainly a worry with 4ohm speakers and low-mid range priced AVRs.
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post #5 of 10
2/16/13 at 10:24am
Thread Starter 
Quote:
Originally Posted by Knucklehead90 View Post

True - in a manner of speaking. I'm sure you meant that driving speakers hard with an underpowered amp is what will kill the speakers.
If I were going to use those speakers near field like computer speakers I sure wouldn't need 200wpc to drive them. Conversely putting those speakers in a very large room and sitting back 20' I would need more than the minimum wattage the speaker manufacturer recommends.

The difference between an amp/receiver that delivers 10wpc vs 100wpc or 15wpc vs 200wpc isn't the wide gulf it might look like on paper. Check out this link on Crown Audio's site. Play around with that calculator. It'll give you specifics on how much power you need for those speakers. Note that as the db level goes up the power levels climb fast. Faster than the sound levels.

I plugged in your speakers' specs into that calculator at 85db and 3 meters sitting distance with 6db headroom for the amp. It takes 6 watts to play them at 85db - AKA - reference level. Up the db level to 100db to account for very loud and fast transient sounds and 6db of headroom and now you need 100 watts. Speakers with 90db efficiency would need 358 watts to satisfy the 100db SPL while maintaining 6db of headroom. Drop the headroom requirement to 3db and now you only need 180 watts. While most AVRs can accommodate that transient sound it probably won't do it without clipping. They just don't have the capacitance.

Having said that a few questions - how large is your listening space? Ceiling height? How loud do you play music or movies? The answers will give you a ballpark figure for your power needs. Unless you listen at very high levels you might be surprised by how few watts you really need. No need to match the amp to the speakers other than impedance requirements. Mainly a worry with 4ohm speakers and low-mid range priced AVRs.

Great now suddenly a lot of what i have read makes sense. It is funny how one piece of information can make all the other information fall into place.

Iit is going to be a dedicated HT, most of my music listening is going to be somewhere else with some sweet B&W i have owner for 5 years now.

The room configuration is as follows..

The room is 7.5 mts long by 4 mtrs wide by 3 meters ceiling height. The seting area is at 3.5 mts from the speakers.

The AVR's availiable in my area are Onkyo and Denon. Im inclining towarsd Denon.

Anothero option is a combination of anthem Preamp/amp combination but the price might go to the roof, but i guess that the amps have greater capacitance to avoid clipping, right?
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post #6 of 10
2/16/13 at 11:00am
Thread Starter 
The only i thing i still dont understand is something about the specs of the Speakers.

For example this Paradigm speakers que are talking about say this two things.


Suitable Amplifier Range 15 - 200 watts
Maximu input Power 140 watts ?

How can the maximum input power be lower than the amplifiera range? Wouldn't it mean if i put 200 watts im going over the 140 watts?

Another brand im looking at says.

Power Long/Short term: 150/200 watts.

confused.gif

Thanks again guys.
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post #7 of 10
2/16/13 at 2:05pm
Quote:
Originally Posted by Completenewby View Post

The only i thing i still dont understand is something about the specs of the Speakers.

For example this Paradigm speakers que are talking about say this two things.


Suitable Amplifier Range 15 - 200 watts
Maximu input Power 140 watts ?

How can the maximum input power be lower than the amplifiera range? Wouldn't it mean if i put 200 watts im going over the 140 watts?

Another brand im looking at says.

Power Long/Short term: 150/200 watts.

confused.gif

Thanks again guys.
Maximum power input is the max that the speaker can use on a continual basis - i.e. - LOUD!
Short term power means the ability of the speaker to absorb/use up to that much power on a transient/short term basis. And most speakers can absorb twice their rated max on a short term (transient) basis with no ill effects. That will be a very loud moment!

So your speakers max power would be: Power Long/Short term: 140/200 watts. Don't get caught up too much in the minimum/maximum power requirements. Like I mentioned above you simply need to know how you will be using the speakers and AVR - that calculator will show you the power requirements. I wouldn't shoot for 6db headroom since 3db will more than suffice. One of the big motto's around here is "You can never have too much power". While that is true its you paying for the power - not the one recommending that 1,000wpc amp. Its akin to putting a 600hp motor in a car that will be stuck in stop n go traffic for most of your commute when 120hp will get you home.
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post #8 of 10
2/16/13 at 7:57pm
Thread Starter 
Quote:
Originally Posted by Knucklehead90 View Post

Maximum power input is the max that the speaker can use on a continual basis - i.e. - LOUD!
Short term power means the ability of the speaker to absorb/use up to that much power on a transient/short term basis. And most speakers can absorb twice their rated max on a short term (transient) basis with no ill effects. That will be a very loud moment!

So your speakers max power would be: Power Long/Short term: 140/200 watts. Don't get caught up too much in the minimum/maximum power requirements. Like I mentioned above you simply need to know how you will be using the speakers and AVR - that calculator will show you the power requirements. I wouldn't shoot for 6db headroom since 3db will more than suffice. One of the big motto's around here is "You can never have too much power". While that is true its you paying for the power - not the one recommending that 1,000wpc amp. Its akin to putting a 600hp motor in a car that will be stuck in stop n go traffic for most of your commute when 120hp will get you home.

Great its almost completely clear now.

So now i get it with the amps and sensibility and desired SPL and stuff but lets get back to de ohms.

As i mentioned earlier there is one other speaker line im looking at that has great price and it is supposed to be very good, the Jamo D500. I know Jamo doesent get a lot of love arround here but in europe is highly regarded and i have heard them at a friends HT and really liked them and did i mentioned the great price?


the front LCR are rated at 8 ohms 150/200 watts power and sensitivity of 89 dB
the Surrounds are rated at 4 ohms 120/170 wattas power and sensitivity of 84 dB

The problem is that the amps i can get are only 8 and 6 ohms compatible. So??? does that mean i cant plugg them to this amp? or if the power requiremesnts to obtain the desired SPL is very low because of the distance to the listener position being much closer it means i can be sure that they will get enough current? or the amp just wont put out that kind of amps?

regards
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post #9 of 10
2/16/13 at 10:42pm
I would not be overly concerned with surrounds that are 4ohm rated. Small woofers don't often cause impedance dips to 2ohms - its the large woofers that do this. I'm sure there are lots of Jamo owners driving those surrounds with 6-8ohm rated AVRs that never have a problem. If the front L/R main speakers were 4ohm then you would be wise to be more cautious. Which model of surround speakers are you considering?
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post #10 of 10
2/17/13 at 10:38am
Thread Starter 
if i go with the jamo's i'll get the jamo D500 5.1 kit. if i go with the SE series of paradigm ill get the SE 3 for L/R de SE center and the SE 1 for surrounds.
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