A few comments, questions (and equations) about dB output, speaker efficiency, amp power, noise and that grungy noise floor...

For the purpose generating further discussion I submit the following:
As SoundHound has very aptly described, he has incredibly efficient speakers and as a result can use a less powerful amplifier to achieve reference level dB SPL's (volume). As opposed to more typical audio systems using less sensitive speakers, SoundHound also points out that efficient speakers produce the wide dynamic range for music and movies with a far smaller range of amplifier power (in direct terms). I believe it is also true, however, that no matter how efficient the speaker, there is a proportional relationship between power and sound level (dB's), which has some very important implications.

As we are concerned about amplifiers operating in the extreme lowest and highest power ranges where distortion becomes problematic, the goal of matching the amplifier design and the speaker is critically important. Furthermore, as the sensitivity of the speakers increase, it appears that the total system becomes more susceptible to noise generated by the other components, signal interference and the like. For those who can not customize the amplifier to these high sensitivity speakers, it seem like a very delicate and potentially expensive road.

Signal Level (dB @ 1m) as defined in my text as:
dBm = 10 x log (Amp Power in watts x (10 to the exponent (Speaker Sensitivity /10) ) )

Thus, speakers with a sensitivity of 106dB/watt, at one watt amplifier power, will produce a signal level of 106dB. Because of the high sensitivity, it would take only 0.000795 watts to produce a signal level of 75 dB. I am confident that SoundHound has the right amp for the job, but WOW, these are some really small amp power numbers. A signal level of 65 dB would require only 0.00008 watts of amp power... and so on... So, I am curious; where is the grunge floor on the tube amp that can make this system sound great when the music gets soft, and movie is at a whisper?

I have B&W N803 mains, with a sensitivity of 90dB/watt. These are bi-amped with two channels of a OA Model 770 dedicated to each main speaker. . According to the formula, it takes 0.032 watts to produce a signal level of 75 dB. Although this seems low, it is 40 times more power than SoundHounds speakers require for the same 75dB signal level. I have no idea where my grunge floor is, as I do not have the diagnostic equipment, or the expertise to find it on my own. All I know is that I love what I hear; when the music is as delicate as a Chopin nocturne, or when Jimmy Page tears up the Stairway to Heaven.

Speaker preferences are what they are, and all of us can enjoy our own, but I am very interested in how the gunslingers view the interrelationship between Speaker Sensitivity, Amp Power, Amp Type, Noise and the Grunge.




[This message has been edited by AGAssarsson (edited January 26, 2003).]