Wattage calculations

[akis]

I just thought about clipping : when my amp clips, on a 7.5 Ohm dummy load, the sinusoidal becomes square. A simple calculation shows that whilst the amp cannot deliver more than +/- 34 Volts into the 7.5 Ohm load, in the sinusoidal region, just when it is about to clip this translates to 77 Watts RMS. But when it goes into clipping land the shape becomes a square and the power output then becomes 154 Watts RMS.

Does this mean to say that I must choose speakers with RMS rating of 150 Watts or more?

Am I missing something?

[tinitus]

Originally Posted by akis

Does this mean to say that I must choose speakers with RMS rating of 150 Watts or more?

Am I missing something?

Maybe better look at speaker sensitivity

[nigelwright7557]

I always run my systems with speakers way in excess of what the amp can put out.
This means the speakers will run reliably over long periods and high powers.

I run a 300WRMS amp into 1000WRMS of speakers.
I probably never get above 200WRMS anyway even at the biggest venue so nothing is being stretched.

[Bob Brines]

Are these posts intended for this forum? It IS the full-range forum, isn't it?

The full-rangers generally used here rarely have RMS rating in excess of 30w. There are a lot of folks that have amps rated at less that 10w/ch. Obviously, they are not going to exceed the driver's power rating. On the other hand, any number of folks (like me!) run with at least 100w/ch. No problem, just be careful about turning the knob. Probably not a good idea for a college dorm room, but if you have control over the volume knob, dynamic headroom is always a good idea.

Here's the deal about full-rangers: Most full-rangers will run out of excursion at the bottom end long before the thermal power limit is reached. They will distort like mad and go into dynamic compression. But remember that with a 95dB/w/m driver, 1 watt of input is LOUD!

You will not be exceeding 77w/ch with any reasonable full-ranger. Don;t worry about it.

Bob

[akis]

Originally Posted by Bob Brines

Are these posts intended for this forum? It IS the full-range forum, isn't it?

Could not find "speakers - general" AND there are no crossovers involved, so this forum fitted best.

Musical instrument amplifiers are generally used for gigs and they do not follow ordinary living-room-listening-rules. I was looking for second-hand units (on ebay) and was wondering what abuse could they potentially have been subjected to and then I remembered about clipping and how it would be possible to drive an amp to clip and therefore exceed the RMS of the speakers, if my calculations and assumptions are correct of course.