I had a similar problem and I think what this means is the following - if I am wrong I am sure one of the experts here will correct me: B&O gave efficiency in watts meaning the number of watts needed to produce 96 dB SPL (I assume at 1m). So 2.5 watts efficiency should be around 92dB in the usual sense. 

I had a similar problem and I think what this means is the following - if I am wrong I am sure one of the experts here will correct me: B&O gave efficiency in watts meaning the number of watts needed to produce 96 dB SPL (I assume at 1m). So 2.5 watts efficiency should be around 92dB in the usual sense. 

Ok, here is a page from the CX100 manual that states explicitly: "Power at 96 db SPL -- 5 watts". In this case sensitivity is also stated in the usual way as 89db, and both figures, of course, agree. 

The part about 96db SPL is not stated explicitly for the older models, but this is a good indication that this is how B&O measured it. Also, it corresponds to the performance one could expect from the various models, e.g. S50 are 4 watts, meaning 90db, but the MS150 are 2.5 meaning 92db as being TOTL.

Login to view image

Thank you all. I think, from the various responses, that the efficiency is 92db, if expressed in the more usual way. I ask as I am connecting them to non B&O amplifiers. 

If anyone uses a pair, if be very interested in hearing your opinions on them.

Thank you all. I think, from the various responses, that the efficiency is 92db, if expressed in the more usual way. I ask as I am connecting them to non B&O amplifiers. 

If anyone uses a pair, if be very interested in hearing your opinions on them.