I have been trying a few things with the crossover for these speakers. The original design goal was to make them as simple as possible but they sounded so good I wanted to see what more could be teased out of them!
The original crossover used the natural roll-off of the woofer with a first order filter on the tweeter. As the woofer naturally has a 2nd order roll-off it was not the ideal way to do it and the crossover is not as perfect as it could be; pushing the tweeter harder than is needed.
This new crossover has 1 more component – a 330uH inductor in parallel with the tweeter which makes the tweeters roll-off 2nd order to match better with that of the woofer.
In the original crossover the more gentle slope of the tweeter boosted the upper frequency response higher than 'flat' and so I compensated for this rise by using more baffle step correction than was otherwise needed.
So, this new crossover gives the tweeter an easier ride since it is not asked to reproduce such low frequencies and it also has a more 'ideal' crossover between the woofer and tweeter. Interestingly, when I built the crossover to have a pretty much flat response, as I have done with most other speakers (I use in-room measurements, a few meters away from boundaries) the sound was rather full bodied and lacking presence. In my experience this is not normal for a speaker with a flat response from the lower midrange up.
Here is the woofers response with the BSC to give a flat response.
I found that I had to give the whole response a slight tilt to the high end to get the more open sound that I am used to from a flatter response with most speakers.
I believe this must be because the tweeter is mounted in the woofer cone that acts as a wave-guide thus limiting dispersion. So while the high frequency response in front of the speaker is flat, the amount of energy in the room is still not as much as from a speaker with a wider treble dispersion. So to get a similar amount of total energy in the room (power response) the whole response needs tilting up a little bit.
This is the end response of the whole speaker and new crossover that I found sounded just right.
Here is the final ( I think!) new crossover design. Oh and also please note that the bass goes deeper than 50Hz as the graph seems to think. It might be a room mode suck-out or what I don't know. But I have heard it reproduce stuff down to around 35Hz when positioned near room corners.
Happy listening everybody!