Driver efficiency vs. overall speaker efficiency

Sorry , I meant 87.5db. It was a typo. I was looking at various Vifa and Scan Speak mid-range drivers and almost all of them has an efficiency rating of 87db or less. So I was wondering how one can build a speaker using those driver but can achieve an efficiency rating of 90db or larger.

If you connect two drivers in an MTM configuration,the impedence will be halved,drawing twice the current, but about 6 dbs will be added. So,it is possible to wire two 88db,8 ohm speakers so that the final result is 94db sensitive into 4 ohms.

Pragmatist, if more current is drawn to achieve a higher sound level, the efficiency hasn't increased. Or am I making a mistake here? A higher efficiency means more output with teh same cuurent.

Satch...Efficiency is stated as dB per VOLT (not current). Of course the current will be more with a 4 ohm load, but that's the power amp's problem.

Satch:

I'm not an expert,so allow me to quote my source:

http://www.northcreekmusic.com

If you link through to the page that describes their rhythm speaker,in the fine print,it talks about an mtm set-up and its effects.(It's the paragraph labeled "Sensitivity and Impedance".)