OK Folk's here's some more thorough measurements. I think these are begining to show just what the EP500 can really do!
The SPL meter was mounted on a tripod and placed on the couch in the listening position. The sub was moved to the different positions indicated on the plot for testing. At each position the 50Hz test tone was played first and the volume adjusted to 90dbs for the first graph and either 90db or 100db for the second. Once the 50hz tone was adjusted, measurements were taken. Values again were compensated for the Rat Shack non-linearity given by the SVS site. Note: the Hertz are plotted from 125 to 10 (opposite to the above posted plot)
As can be seen all the positions in the room (original position= position in previous graph above) yield pretty well the same freq response with the exception of the placement in the Middle Front and in the Centre of the Room. The Centre of the room just plane sucks; clearly there's little benefit from boundary reinforcement. Other than an obvious increase in loudness due to boundary reinforcement, placement in either corner yeilded no improvement in Freq Response. The Middle Front seems very impressive to me particularily in the low end. There's one difference with this placement though; I really had to increase the overall volume of the sub (just like for the centre placement) in order to get a 90db reading with the 50Hz test tone prior to testing.
After getting this better curve with placement in the Middle centre I wondered if increasing the actual output from the sub had any influence on the Freq Response (even though the EFFECTIVE volume at the listening position was the same as the other placements)
Consequently, I decided to put the sub back into my "Original Postion" with out adjusting the volume output. This resulted in the initial 50Hz test tone being 100db (instead of 90db). In so doing I managed to maintain the smoother profile even in the different position!??!
Now I'm actually getting higher output down at 12 and 10 Hz than at 100! And the response has smoothed out quite a bit.
Questions:
1) It seems the Freq Response gets flatter when the sub is made to exert more. I figure that this is either due to the sub itself or some phenomena from the room. Does any of this make sense to you Experts? Would this be a characteristic of the sub or the room. Louder gets smoother...? Given the DSP on the EP500 I'd assume the sub should be equally linear at any volume???
2) Now as nice as I think the Freq Response is at this volume the problem is I can't imagine listening to it this loud and placement in the middle front position is not an option for me since the TV and equipment cabinet containing the DVD, and reciever sit just behind there. I actually saw the TV picture shake in this position. So any ideas how I can get around this? (other than ear muffs) ???
3) Any critique of my measurement method that may offer some more insight on how I get this affect. Louder=Smoother???
I very much appreciate all your input.
Cheers, Jag