Originally Posted by bscool
Marc measured the F18 at his GTG but I think his below 20hz # are a little low. Using Data-bass the Epik is similar in output(little less from 40-60hz and more output above that) compared to the Submersive and you can see the UM18 against it. So another take on how they compare.
The response shape, behavior beyond CEA limits, and distortion characteristics make the F18 and Empire extremely different performers which would sound drastically different and subjectively have very different maximum capabilities.
I know Marc A and Mark S have said the F18 has more output than the UM18 but looking at the Data-bass numbers I don't see it when compared to Marcs measurements. Maybe I am missing something. I know Ricci used a much more powerful amp than the F18 uses.
The amplifier in the F18 delivers more than the 89V RMS used in the long term compression sweeps. Unfortunately environmental conditions mean most any of these measurements will have 1-2dB of variation either way simply testing on different days and especially depending on temperature and how long a black box has been baking in the sun. I am thinking it would make sense to spray test units white to make thing easier for who ever is running the test. While measurements taken at one location and the same time can often be very useful for direct comparison, holding tight enough tolerance to compare to other testers across the country requires a much higher level of precision and calibration in gear.
Based on the testing I have done, we get a smidge more in some ranges, and a bit less in others as I don't allow the driver to go into harsh overload, and above 40Hz we aren't dumping 200-450V into the driver, which you can't easily do in real use anyway. One data point which correlates very well with my own measurements is the very low distortion above 30-35Hz as see in the Data-Bass Total Harmonic Distortion measurements. If you look at the chart listing out CEA maximums, the drivers we use will not run into the mechanical noise limit Josh noted on the 31.5Hz & 40Hz burst testing. A soft limit there vs a hard, offensive one makes for quite the subjective difference in listening.
So if you want to compare how the F18 compares to other subs on Data-bass I would use the Um18 but take off some up in the higher FR for the higher amplifier power Rikki used. Like compare the UM18 to the Cap 2 on Databass and add 6dB for 2 F18 against the Cap2 to make it equal. Not perfect but gives you a rough estimate and a visual to make it easier to see and compare.
Generally agree here if you're looking primarily at CEA maximums.
I know this summer Josh has had limited time to test subs, and I have been talking with one industry acquaintance who might be up for performing such testing as an independent lab for hire. Since acoustic measurement and design is his livelihood it can't be free or such low cost testing as Data-Bass has done, but he might have a longer test window through the year than Josh's latitude dictates and could possibly get to products much more quickly.