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Underpowering speakers?

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dawnsica

New Member
Hey, bit of a noob here. I'm wondering about the importance/relevace of speaker vs amp wattage.
I have a pioneer sx-440, and am looking for some suitable speakers. I believe the SX-440 has 12 watts/channel at 8 ohms.
I've been offered a pair of Polk audio monitor 5s, and some online research I've done has told me that the recommended amplification for these is 20 – 125 watts per channel.

Is this a good pairing of speakers to my amp? what are the disadvantages of underpowering these speakers, and how much does it matter?

Any help greatly appreciated, thanks!
 
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It's not so much underpowering your speakers that can be bad, what's bad is when you overdrive your amplifier into clipping.

The power-rating on the speaker is really rather irrelevant. What's more important is how sensitive the speaker is. If it's in the neighborhood of 90db@ 1w/1m you'll probably be okay. That means the at one meter away from the speakers they'll produce 90db of noise with only 1 watt. Find out how sensitive the Polks are and that's a better guideline then 'recommended wattage'.
 
The Polk 5 are nice little speakers. They should be fine if you do not crank up the amp too far. If I recall correctly the 5's have a fuse to protect the tweeters. Welcome to AK.
 
Thanks for the replies. The guy with the speakers said they're "Frequency response: 30hz – 25khz -3db limits and 43 hz – 23 khz". Is this the sensitivity?

Can anyone point me to a good resource for understanding things like ohms, watts, speaker sensitivity etc?
 
dawnsica said:
Thanks for the replies. The guy with the speakers said they're "Frequency response: 30hz – 25khz -3db limits and 43 hz – 23 khz". Is this the sensitivity?

Can anyone point me to a good resource for understanding things like ohms, watts, speaker sensitivity etc?
Click to expand...
If they do not state sensitivity of 90DB or more, I would leave them.
Why not look for a speaker of the same period as your amp ie I've just done up
a pair of Wharedale Dentons. They are rated 25 watts max. 92db 1 watt/1metre and are a good match for your SX44O.
Naturally there are many others out there that would also work well.
 
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Those look like very good speakers by the way. A good combination in fact to moderatly loud levels.

The minimum recomended power requirements for most speakers is an arbitrary number chosen by the Company for the brand and is based on a SPL that they consider would satisfy their customers.

Those polks are 90 db/w I believe. Suffice to say that the 12 wpc from your amp should drive them fairly loud. Also the 6 ohm Impeadance makes them an easy load for your reciever. Not to alarm you, but like any amp just keep it out of clipping and you should be safe. Sometimes about 12 O'clock or just past on the volume with low powered reciever's like my 10 wpc Realistic STA-7 is close to clipping with the louder CD's for example. My more powerfull vintage 45 wpc reciever went to about 1:30 on the volume knob as do most of my other gear.

If the Loudness is on, or tone controlls are used to increase bass or treble you must back off the volume controll some. I suspect the problems with underpowered amps people talk about are more related to someone turning up the bass 6 db or leaving the loudness on and cranking the volume to 2:00 O'clock...expect problems if you do that with any Amplifier.
 
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You will go into unsavory amplifier clipping.

The output stage clipping often isn't clearly audible however you will most likely hear a grainy quality,that dreaded "solid state" sound which is really the protection circuit current limiting to prevent damage to the output transistors.
 
so am I understanding correctly that amp clipping will happen because the speakers will draw a bit more than the amp likes? As a general rule, is it best to have the speaker and amp impedence matching, ie for this sx440 amp i should use some 8ohm speakers?

thanks for the help, and sorry if these are some frustratingly simple questions. That link scott594 provided is great - exactly what i needed to read.
 
Are the Polks ideal for that receiver? No.
Will the combo make good music - Almost certainly, as long as you don't turn it up to where it starts to sound crappy. What point on the volume that is depends in large part on your room.

If you were buying new speakers I don't think these would be them. But if you're getting a deal from a friend I think you'll be happy, at least for a while.
 
so what kind of speaker specs WOULD be ideal for this receiver? something built at a similar time?

Are you able to let me know if my assumptions above are correct, or am I heading down the wrong tracking in trying to understand this stuff?
 
All it takes is a little discretion in your use of volume and tone controls, and that will be true of any amp/speaker pairing. Don't push that amp too hard, and at louder playing volumes you should leave the tone controls set flat and loudness control off. And if you turn your volume control up to 12:00 - straight up - then you should only turn past that with a great deal of caution. That is really all the understanding that you need in order not to damage either speakers or amp.

Of course, these are all "rule of thumb" recommendations, to which there are always exceptions. For instance some sources may send a higher or lower level signal to your amp, eg, a TV's audio output is often lower than a CD player's output, in which case you may be able to turn the volume control higher for the TV than for the CD, in order to get the very same volume level from the speakers. This simply means that you need to listen and turn down the volume when the sound starts to get a bit harsh, which is usually first noticeable in the highs - the tweeters.

Those speakers should do really well as long as you use a little common sense. Trying to match to a speaker with a lower power rating may just make it that much more likely for you to damage the speakers.
 
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Try to see if you can get some Klipsch Synergy or Reference series bookshelf or towers used....I am listening to some SF-1 s now...high efficiency Klipsch will be good match for your receiver.
 
icenine said:
Try to see if you can get some Klipsch Synergy or Reference series bookshelf or towers used....I am listening to some SF-1 s now...high efficiency Klipsch will be good match for your receiver.
Click to expand...

It is true that more sensitive speakers may allow you to play louder, but not to turn the volume control further. Those rules of thumb still apply. I have a pair of Klipsch that are more sensitive than the Polks, but at a rated 4-ohm impedence may not be as good a match for your receiver as the Polks.

Regardless of all that, many of us will at least occasionally push the envelope a bit at times, no matter the sensitivity of our speakers or the power of our amps. There is no free pass from discretion; drive your amp into clipping and you can damage any speaker. Or fry your amp. Or both.
 
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