"How many watts"?

[ihasmario]

I'm trying to decide how many watts I need in a power amplifier.

The information I know;
Speaker is 8 ohms
Maximum input for speaker is ~535 watts
~535 watts produces 122dB.


Basically, as is my understanding, I can get away with much less than 535 watts, as half of that will produce 119?


How do you personally guage how many watts you need? Do you try have enough headroom to exhaust the speaker, or just to get to a level you like?

[dingostolemyipod]

I think i know what you need this amp for .

When talking spl, when used in a human hearing context, spl is weighted with an A weighting, where low frequencies are heavily attenuated (20dB down at 100Hz, 40dB down at 20Hz). This is due to the fact our hearing is incredibly insensitive at low frequencies compared to midrange. http://en.wikipedia.org/wiki/A-weighting
However, if you're trying to produce low frequencies from an amp/speaker, well that's all "unweighted" spl you're trying to produce, so trying to get 100dB of perceivable bass (a weighted) needs 120dB or more of raw spl. I might be wording this in a funny way, but i hope you pick up on what i'm trying to say. It's also why you can find a 10 or 20W guitar rig can keep up with a 400W bass rig.

Generally, it's better to over-rate amps compared to speakers than use under-rated ones, as clipped peaks from an under-rated amp do more damage to speakers than a peak above their rated power. But if you're not driving the amps or speakers at, or near max, then no need to worry here.

So in other words for your purposes, don't stinge on the amp.
But given every time you double/halve output power is only +/- 3dB in headroom due to the logarithmic nature of our hearing, there's not really that much difference between a 300W and 600W amp, so you probably could get away with a 300W amp, but i wouldn't go lower.

[ihasmario]

You've got it. Thank you for the info.

I think I've settled on this
http://www.ebay.com/itm/CARVIN-DCM1540L ... 2a18522114

- It's got a reasonable amount of power (475W for 1 channel, 450W for 2) for unbridged
- It's got lots of power for bridged (~1500)
- AB design means it will have lower THD the less I push the amp (I think) - which means the huge overshoot in watts is a good idea (I think)
- Good enough SNR for me to consider using it for studio monitor applications at a later date.

Maybe a bit overkill, but we are posting on a forum that basically caters for audiophiles so... oh well

[kelvinyap9]

Watt you are asking is beyond my knowledge.

Sorry, I had to. I'll leave now.