Confused about amplifier-speaker relation

[revans]

I'm new to this stuff and am trying to understand without asking but something just confused me and a little clarification would be great.

When matching speakers and amplifiers, sites I've found such as this one: http://www.satcure-focus.com/icetech/page2.htm tell you that speakers should have an RMS of slightly more than the amplifier.

However, on Saturnus's boombox The Boominator - another stab at the ultimate party machine (which is very cool) he is using an Amp6-Basic which outputs 2x25W with 4x 100W P.Audio HP10W woofers and 4x MGR CH-100 tweeters.

The reason I've used the boombox as an example is that I'm interested in making something similar and would like to use the same amp (Amp6-Basic) as Saturnus.

I don't get it. Wouldn't the speakers be really underpowered? Even just the woofers are 400W in total and they're being powered by an amplifier which can only do 25W per channel.

Being new to this there's probably something obvious I'm missing and this will look like a kind of stupid question, but thanks for any help.

[Jan Dupont]

It's a good idea if the speakers can handle quite a bit more than the amplifier can output. I always use double up, so my speakers can handle twice my amps output.

One of the reasons is that if you play to the amplifier limit, it will start to "clip" which is quite easy to hear as the sound gets unpleasant and you then know you have to turn the volume down. It's much harder to hear when a speaker reaches it's limit. Many times you don't hear it before it's to late and then the damage is done.

There are also other considerations as to the amount of Watts each driver receives when you pushing the amplifer to clip.....

[janneman]

Also, the speaker limit is usually a thermal limit, beyond which it is damaged. It doesn't mean it can be used for reproducing music distortion free at that limit. In fact, using a speaker at its power limit will sound horrible!

Jan Didden

[revans]

Thanks guys,

I'm looking to use the Amp6-Basic which outputs 2x25W at 4 ohms. I'd like to use one speaker per channel so if I double like ACD says I should would I be right in thinking I should be looking for two 50W 4 ohm speakers (one per channel)?

[Jan Dupont]

On the spot, janneman

revans;
That would work fine.
However do your self the favour not to save a few bucks by purchasing some "no name" speakers with unrealistic specifications

[Mooly]

Efficiency is one of the most important points when considering "how much power and how loud".
Take two speakers, one at 82 db sensitivity (sound pressure level for one watt input) and another at 94 db. The second one will be as loud for 1 watt input as the first is for 16 watts input.
A 3 db increase in sound level which isn't very noticeable to many, requires a doubling of the power supplied by the amp.
As ACD explains, clipping -- when the amp runs out of "voltage" is the killer for speakers, the output levels off to what is effectively a high DC voltage - result burned out speaker.

[Andre Visser]

It is easier to damage speakers with a low power amplifier than with a high power amplifier.

Clipping and distortion damage speakers, so I prefer to use high power amps (sometimes more than the speaker rating) and never had any problems, you can get better sound quality and higher SPL without distortion from the same speakers.

Edit: Sorry Mooly, you posted while I was typing.

[Mooly]

Gotcha Usually happens to me.

[revans]

Thanks to all for your input. I'm going to trawl the web for some speakers myself but meanwhile: can anyone recommend some suitable speakers that aren't too expensive but will work well for my use (2x 4 ohm 50W full-range speakers for an Amp6-Basic)

[revans]

I'm having difficulty finding 50W (or thereabouts) 4 ohm full range loudspeakers. Does anyone please have any suggestions?

So far the only speakers in the 4 ohm department with a near suitable RMS I've found myself are the Dayton RS100-4 (30W RMS) http://www.partsexpress.com/pe/showd...number=295-378
and the Tang Band W4-1757S (35W RMS) http://www.partsexpress.com/pe/pshow...TOKEN=57238633

Is that enough wattage per channel for the Amp6-Basic or do I need to find something closer to 50W?