Stock woofer vs. db840 measurements
I did some measurements comparing the stock woofer to the db840 if anybody is still interested!
My bedroom measures 14 x 12 x 7.5 feet. It has some bass trapping in the corners and some absorption along the front and side walls. The left speaker is 43" from the side wall, the right speaker is 75" from the other side wall, and both speakers are 25.5" from the back wall (as measured from the tweeter). The mic was placed at the point of the equilateral triangle formed by the speakers at tweeter height.
Equipment used was a Behringer ECM-8000 omnidirectional measurement microphone, Behringer Xenyx 802 mic preamp, and Room EQ Wizard v5.01 beta 17 build 2967. The ECM-8000 calibration profile (taken from the Home Theater Shack forum) was loaded. I still haven't figured out why there's a sharp drop in the SPL response for all my measurements after about 8KHz, but it shouldn't really affect the results of this test.
Before I post the measurements, here's some quick results from playing some pink noise and measuring the output:
stock woofer, left speaker: 66.8 dB
db840, left speaker: 66.8 dB
stock woofer, right speaker: 66.0 dB
db840, right speaker: 66.3 dB
stock woofer, both speakers: 72.0 dB
db840, both speakers: 72.2 dB
So there's no real drop in efficiency, it's actually pretty well the same after the swap.
And now for the measurements comparing the stock woofer vs. the db840. Click the images for a bigger size.
20-20 000Hz, 1/3 smoothing
Figure 1. Left speaker, stock woofer in blue, db840 in green
Figure 2. Right speaker, stock woofer in purple, db840 in yellow
Figure 3. Both speakers, stock woofer in blue, db840 in green
20-400Hz, 1/48 smoothing
Figure 4. Left speaker, stock woofer in blue, db840 in green
Figure 5. Right speaker, stock woofer in purple, db840 in yellow
Figure 6. Both speakers, stock woofer in blue, db840 in green
Figure 7. Left speaker, stock woofer
Figure 8. Left speaker, db840
Figure 9. Right speaker, stock woofer
Figure 10. Right speaker, db840
Figure 11. Both speakers, stock woofer
Figure 12. Both speakers, db840
Well, compared with the stock woofer, it seems that the db840 affects the response slightly (i.e. usually less than a dB or so) from about 1kHz downwards, with the most noticeable differences happening between roughly 80Hz and 350Hz. In this latter region, there can be up to a 5.5dB drop in output with the db840.
Interestingly, the db840 doesn't seem to dig any deeper as some have noticed, as the -3dB and -10dB points are pretty much the same for both!
The waterfalls don't really show quicker decay times for the db840.. in some cases (e.g. 43Hz), the decay is actually longer. Note that 43Hz represents the interaction of both the length and width modes of my room.