efficiency- hope i spelt that wright.


after my last thread, I started thinking about speaker efficiency, my speakers are rated at 87 db's which i think are pretty inefficent,so I am thinking I need a bigger amp to drive them, is this true? now lets say i enjoyed klipsch (which I do not) they are very efficient so would a low wattage amp perform better for this speaker vs. a high waggage amp? Is a guy wasting his money buying inefficient speakers? my thought are the lower the wattage the cheaper the amp so if you could match them up with really efficient speakers you could have a gem, any thoughts on this question are something i will truly enjoy reading. thanks

mike
magnus89

Showing 1 response by athipaul

There are a few things you must do on paper when it comes to Amp/Speaker combinations.

1. Find out the lowest impedence of your speaker. If lowest impedence is 4 Ohms you should be fine, anything lower than 3 Ohms, you need to make sure your amp can handle this otherwise it will clip i.e run out of power.
2. Find out the minimum power required by the speaker based on its nominal impedence. If the specs say 30-250W @ 8 Ohms, you need a 30W amp and above e.g 60W would be fine. Can you use a 10W amp? Yes but you risk damage if the speaker demands the extra power and the amp clips trying to deliver and in some cases blow the tweeters as well. If no minumum is specified you have even use a 3W SET.
3. Efficiency is only a factor if you have a large room e.g 16x20 and/or you want to listen loud. SPL drops 6dB with each doubling of distance. So if your speaker is 87dB@1M and you are sitting say 3M (10 ft away) and your amp was using its first watt your SPL would be around 78dB. So what is loud? 85db is loud and safe. 90db is very loud only safe up to 8 hours per day before hearing damage occurs.
4. How much power then? Each doubling of power produces and increase of 3dB. So as per example above, you would need 78dB(1W),81dB(2W),84dB(4W),87dB(8W).

After all this homework, you should now listen to that amp/speaker combination.

BTW, my own speakers are rated at 87dB/M but specify needing an amp between 100-400W @ 4 Ohms, I am using a an capable of 500W @ 4 Ohms. On paper this amp will never cough up anything more than 6W at the volumes I listen to and only on demanding material would the amp ever have to call on its reserves.