Originally Posted by bigguyca
You have based your posts on the an estimate of the output of the internal preamp stage, likely the output of the volume control. A typical output at 0 dBFS would be 1V to 2V RMS. The only RCA output on your AVR are for the subwoofer so an assumption can be made that you are connecting your speakers to the power amplifier outputs on the back of the unit, not to the internal preamp stage.
A typical AVR power amplifier has a gain of about 28x, that is, about 29 dB. If the output of the preamp stage is 1V RMS at 0 dBFS, then the output of the amplifier section, to which you have connected your speakers, can be estimated at 1 x 28 = 28V RMS.
The are a lot of approximations in your last post, but using the 111 dB number, something like 111 - 29 = 82 dB is more in the ballpark, but that could vary a lot, depending on the validity of you other a assumptions. Grossly, 82 dB SPL gives a power efficiency of something like .1%. 90dB SPL would be around .6%. Typical home loudspeakers have a low power efficiency.
Originally Posted by Optimus_Fine
Yeah, I've kind of gone too much far off with those calculations.
So, assuming my AVR outputs 28.28 V RMS at 0 dB MV/0 dB channels trims/0 dB input trim, it should go like the following:
-29 dB MV = 1 V RMS at 0 dBFS RMS
-20 dB MV = 2.828 V RMS at 0 dBFS RMS
-9 dB MV = 1 V RMS at -20 dBFS RMS
0 dB MV = 2.828 V RMS at -20 dBFS RMS
Here's what I can't wrap my head around with the data above: each of my speakers at 1 m measures 85 dBC at -15 MV with Dolby + DialNorm -31 and at -11 dB MV with DTS + DialNorm -31.
Even with the worst case scenario of -11 dB MV, if I add 85 dB and the 20 dB of signal headroom, I end up with 116 dB SPL of sensitivity including room gain.
Even if I take off 18 dB of 6 boundaries gain, which is a worst case scenario in on itself, the net result is still a whopping 98 dB SPL of free field sensitivity.
But with an enclosure of 13 liters, 5.25" + 1" drivers and a rated 4 Ohms impedance, is that even physically possible?
There is no reason to believe you have 20dB of headroom. Calibration programs don't check to see if the amplifier/speaker combination is capable of the implied output. For example, many people run say Audyssey, which runs at 75dB SPL per channel and adjusts to 85dB SPL with 20dB of implied headroom to 105dB maximum at the listening position, and believe they are getting all that. This Audyssey calibration in no way means that the AVR or amplifier in use can cleanly drive the loudspeaker to 105dB SPL or that their speaker can perform at the level. Audyssey didn't measure for that, it didn't even measure to 85dB. The calibration program did its room calibration, but really didn't find out if the system can perform at any specific SPL or acceptably at a specific SPL. Few systems can do 105dB SPL per speaker at the listening position, without compression or horrible distortion and overloads, or can do it at all. One of the reasons many people listen at -10dB or lower levels IMNVHO, is that the system is unpleasant, due to being overloaded, above that level.
In the -11dB case above, adding 11dB of gain evidently gets you to 0 dBFS which in the calculations above (for ease of calculations, 28V RMS say into 8 ohms, your AVR doesn't seem to be rated into 4 ohms) gets you to the limit of your AVR of about 100 watts per channel. (Assuming I've understood your post, which at this point is becoming less likely!) That puts you at 85 + 11 = 96 dB SPL. How linear one of your speakers at that level at your listening position - unknown.
And no, your speakers as you have briefly described them, likely can't each do a clean 105dB SPL at your listening position.