Originally Posted by Ricci
Basshead81 I have seen you post the in room charts a couple of times.
Everyone should note that those apply to my room only. They cannot be used as an indicator of what anyone else can expect in a different room even in a ballpark type aspect. Despite what others may say. Distortion is greatly affected by the room and the placement of both the sub and listening position inside of it. The peaks, nulls and relative gain at each frequency have huge effects on distortion harmonics and their relative strength.
Even differences in sub size and placement if the radiator elements on the enclosure can affect how the output is translated to the listening position. The room results are posted in an effort to show one example of how outdoor results can translate in room and also to illustrate just how much the room acoustics can completely change things. They can be compared between 2 subs but there are large differences in how the room affects even fairly similar designs like the vtf15 and XV15. Just don't assume those results indicate anything accurate regarding what to expect in your situation.
Also I wanted to note that the CEA-2010 results that I measured for 1port and 2port modes of the VTF15H were within less than a dB from HSU's posted results for both modes in every band from 16-80Hz except for 2 ports 16Hz which is off enough that it is likely a typo or error. Anyway that shows that HSU's results are correct if anyone had any doubts.
Sorry posting from the phone...
Please read this post by Ricci again. The bolded part was an eye opener for me a couple years ago. For example, say there is a large bump at 60hz at your listening position. It will give you low distortion at that frequency, but even if you EQ it down, that mode will still effect any distortion harmonics of lower frequencies which cannot be EQ'd down. And just the opposite will happen with any nulls. Distortion will rise at the null frequency, but the harmonics will also be attenuated. CEA tests, outdoors or in room, are max output at specific frequencies with limits at different harmonics. While room gain will be similar (not exactly the same) between different subs if placed at the same location, each sub has different distortion profiles and the effects of the room on the distortion of each sub will be different. So outdoor CEA vs in room, could be effected differently for different subs. And again still so much talk about just CEA numbers. Without also seeing the in room FR sweeps, we don't know how much of the burst output shown in the CEA numbers for each sub is usable with a flat frequency response. It feels like this is falling on deaf ears.
In room vs ground plane measurements are great, and can be very informative, if looked at correctly. IMO, some of the more interesting measurements were from Slartibartfast at Avtalk a couple years ago. He posted a comparison of FR sweeps, compression sweeps, THD and group delay measurements of a DD18 outdoors vs in room. Lots of good discussion about those. I don't have all the graphs anymore and they are no longer on avtalk, but here is the FR and THD graphs to illustrate what Ricci was saying. Look where the spikes in THD are and think how that relates to in room CEA numbers.