Ok - filters.
Lets start with the disclaimers. This is the measurements of this pair. I make no assertions that this is how every pair will measure. I will say though that both drivers match pretty closely and that the filters seem to be paired pretty well also. This indicates to me that I have a pair which has no errors (if it did then its more likely that one channel or the other would be different).
The graphs below are generated using the Vibro Veritas coupler and ARTA software. Ken Ball (ALO/Campfire) graciously provided me with measurement data which I have used to recalibrate my Veritas so that it mimics an IEC 711 measurement standard (Ken uses two separate BK ear simulators, we measured the same set of IEMs, and I built my calibration curve from shared data). I do not claim that this data is 100% accurate, but it is very consistent, and is as close as I can get to the IEC 711 standard on my budget.
So first up - channel matching. To minimise possibility of having the filters influence the channels I removed the back filters altogether. here's the left and right channels with grey front filter.
The channel matching is very good - well done LZ!
So lets address the back filters first. Audibly I couldn't really notice a lot of difference between the black red and no filter - but the blue obviously had a lot of difference. So lets see how they measure.
Yes - as suspected, red, black and no filter are practically identical. Between red and black there is maybe 1-2 dB difference, but they are essentially the same. Good sub-bass, well extended. The blue rear filter has early roll off and it is noticeably lighter in impact. But there is still some sub-bass there (just not much below 40 Hz). But its a good filter for those looking for a less bass dominated signature. The pity is that one of the others should have been something between the two (ie flatter, softer mid-bass hump, and a little more extension than the blue). Bit of an opportunity lost.
So lets look at the front filters - first with the black rear filter:
The frequency response pretty much corresponds to colour (with purple being black). So basically what you see is the blue and green having big peaks (too much IMO) and black to pink being far more manageable. For anyone wondering, my preference has changed slightly - I really liked black/grey (still do), but find back/red give just a little more lower treble emphasis which I find pretty good.
So what about with the blue rear filter? lets take a look:
Similar results with blue and green front filters - just a little too coloured for my tastes. But pair the blue with the pink filter, and you get a pretty balanced overall signature. Might be a bit peaky for some - but I really like it for female vocals.
Anyway - hope this helps people to explore the filter options a little more.
Like I said - my picks would be black/red or blue/pink - depending on my mood at the time.