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Yes Zd, you missed the OP's speakers, and it appears you're missing even more. I never said you need 10x power for a 3db increase in volume. To achieve a 3db increase in volume, you either double amp power or increase speaker sensitivity by 3db. This is a basic fact.

Now I do agree with you about the difference in amps being able to deliver power into a full bandwidth of frequencies with a varying impedance load of a speaker. Sure that Sony receiver will not deliver the power to a large full range inefficient speaker, but that is not the case here. The OP's amp (140w@8ohms, 280W@4ohms, stable to 2ohms) is definitely capable to fully drive his small 2-way monitor. Going off on tangents about extreme scenarios just confuses the discussion.

This is just speculation because there's many other factors involve here besides what's in your quote.

Yes, I have assumed his power amp is being driven by an adequate signal, but please tell me what factors, and be specific to his setup, not some extreme scenario.

Sorry, not speculation, he can't add more power to the speaker, so the only way to achieve more volume is use a different speaker with a higher sensitivity.

Check out the KEF R300. You will not be disappointed. Good luck

"I never said you need 10x power for a 3db increase in volume. To achieve a 3db increase in volume, you either double amp power or increase speaker sensitivity by 3db."

You're right. The statement was a typo on my part.

"Yes, I have assumed his power amp is being driven by an adequate signal, but please tell me what factors, and be specific to his setup, not some extreme scenario.

My comment was in reference to this quote.

"Using his 140w amp on a 90db speaker would be the same as 350w on his current 86db speaker, and trying to use that much power on the current speaker is not very smart."

Something like that can only be true if all other factors are equal. Things like impedance curve, type of xover used, driver size, ported or non ported bass, room placement, etc will all work the amp differently even though the sensitivity specs are the same. A good example of what I'm talking about is Wilson speakers. Even though they have fairly high sensitivity ratings, they're usually paired with big SS amps to control the bass. You can find many other speakers with the same xdb rating that are an easier load on the amp. And its those differences that will have an effect on volume without altering sensitivity.

Something like that can only be true if all other factors are equal. Things like impedance curve, type of xover used, driver size, ported or non ported bass, room placement, etc will all work the amp differently even though the sensitivity specs are the same.

Zd, there is no need to split hairs. I don't disagree that these can cause minor differences, but since the power/sensitivity is a logarithmic relationship, they will not be significant to the basic calculations. Yes, room placement can increase certain frequencies, but that is a tonal balance issue, not an overall volume issue.

A good example of what I'm talking about is Wilson speakers. Even though they have fairly high sensitivity ratings, they're usually paired with big SS amps to control the bass. You can find many other speakers with the same xdb rating that are an easier load on the amp. And its those differences that will have an effect on volume without altering sensitivity.

Sure there can be perceived differences when using different speakers on the same amp, but that doesn't change the basic science that I have previously stated. Here is an article that confirms my statement that you seem to doubt, and I hope it helps you to understand,

Let’s talk about dBs, loudness, and sensitivity

Also, here is one of many online calculators that you can plug in the numbers and see that my calculations are correct, within a very slight margin of error.

AllegroSound

So again, the only choice the OP has to get an increase in volume is to use a speaker with higher sensitivity since he can't add more power to the current speaker. If you have another solution, I would really like to hear it.

Nyame: Yes, I have heard a lot of good things about KEF R300, very tempted to get a pair coz it fit in price, availability, outlook, and technology. Mind to share how fabulous it sound?