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A/V amp watts?


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Old 29-10-2004, 00:29
thejabba
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I have currently got some DVD Home Cinema kit with a total RMS of 300watts, however, i plan to get a new seperate A/V amp and seperate new DVD player (with progressive) but plan to keep the same speakers.

If a new A/V system claims for example 400watts and my current speakers have total 300watts, should it be ok unless i reach a certain volume or is this is a case of don't plug them in at all!

Cheers,
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Old 29-10-2004, 04:29
diablo
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Unlikely to be a problem unless you drive the speakers past the point where they start sounding distorted.

If you are buying a separate and presumably 'better' AV amp them it is very unlikely that it won't handle the speakers due to impedance differences - e.g. amp designed to power 8 ohm speakers but given 6 ohms as load.

Even if there were discrepancies in the loading, modern electronics seem very forgiving in this respect. For example, I have connected a big 8 ohm speaker to my little Philips alarm clock to replace the 32 ohm internal speaker - and it's still working after 2 years! (I need the extra volume to wake me up).
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Old 29-10-2004, 07:38
Brush Master
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Originally Posted by diablo
Unlikely to be a problem unless you drive the speakers past the point where they start sounding distorted
That's right. If you really wanted to blow your 300W speakers with a 400W amp, then you must have
[list][*]a serously good amp (one that can actually produce the required amperage at the clamps, not just on the paper)[*]a speaker cable that actually delivers that amperage to the speaker[*]a speaker cable with very low capacity so that you can get the signal edge across[*]a suiteable high quality crossover network[*]an oversized living room and a serious hearing problem.[/list]
The only way in a normal listening environment would be to have a seriously good amp and cable, and an overrated speaker (the speaker would, for example, state 300W (peak) but actually only do 100W RMS). If you then turn the volumne up and listen to serious head-banger stuff, then you might blow it. But then, this would be a relief to your neighbors, too. There's something good in everything.
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Old 29-10-2004, 09:43
chrisjr
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Mind you 300W total in a 5.1 system is "only" 50W per channel. 400W total will only be 66W per channel. So not really putting a very great strain on the wiring.

The biggest danger however is if the power output isn't really 300W RMS but this totally misleading PMPO figure (or whatever nonesense it is ). This gives an inflated impression of how much noise the kit generates and is often many times what the RMS figure would be.

So swapping a 300 PMPO amp for a 400W RMS amp will seriously endanger your speakers as 300W PMPO might only be 100W RMS or even less !

Oh and due to the way the ear percieves loudness don't think a 400W amp is going to sound significantly louder than a 300W one. To get twice the percieved loudness of a 300W amp requires 3000W not 600 as you might have assumed...

In reality however you are very unlikely to run into problems. You would be very surprised to find out just how little energy you are putting into your speakers at normal listening levels. For example I have a 30W per channel amp and I reckon when just watching telly normally it's ticking over at little more than a watt into each speaker and I'm not having to turn the earing aid up
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Old 29-10-2004, 11:03
thejabba
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Lol, ok cheers men, i should be ok. As for my cabling i have the little screw connectors for 3 speakers (Sub, Rear Left, Read Right) as they allow changability since i have cables under the floorboards as i have laminate flooring so i doubt the amp is really ever going to give enough power to the speakers. It sounds alright at the moment, to be honest i'm not after much better sound just a seperate A/V so i can get a seperate newer technology DVD player whilst keeping the dolby/DTS.

Thanks for the help!
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Old 29-10-2004, 13:56
Tim.C
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It's been said, but just to give another voice....

You're more likely to cause damage with a 300W amp and 600W speakers, than a 600W amp and 300W speakers !!!!!!

Why?

The rating for a speaker is because it produces heat. The more power, the more heat, it melts. The peak that a speaker can take for a short time is way more than it can stand continuous.

However, if you push an amp beyond it's limits, you start to get clipping and distortion. This is what will tear your speaker cones to shreds, and is the usual cause of blown speakers.

As fow number of watts - I play Bass in a band, and when I play to 200-300 people, I use a 120W amp only turned up to number 2 !!!!!!!
OK My speakers will be bigger than your TV system, but then again, bass needs much more power.

A fascinating subject all round, and usually totally misunderstood.

Tim.C

ps anyone reading this who's interested in this kind of thing, particularly to do with bass and PA systems, check out this site by the most knowledgable and clearly understood huy I know !!
www.donlisms.com
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