A tale of two crossovers

Friday saw the arrival of two boxes of components from Erse. Definitely the place to go; their components are cheaper and have narrower tolerance bands than those I was buying from Madisound. The 4.0mH 14 gauge coil is, in the vernacular, "stonking".

The two crossover designs were both based on the same near-field measurements. The aim was to test the theory that 1st order networks did less harm to the phase than 2nd order network. Both should have fairly flat response curves if the simulation is to be believed.

Measurements in Speaker Workshop suggested that the frequency response wasn't too far from simulation for both. However, phase was another thing altogether; although the 1st order network looked better in theory between 500Hz and 5kHz, empirically there was little to tell the two apart. The 2nd order had a slightly flatter response so for the moment I'm staying with that one. 

The 1st order seemed to have slightly better performance below 50 Hz, and the 2nd order has a 9dB peak at about 250Hz - so on reflection I think I'll fry a 1st order on the Phase Vs (not yet built). The upper panel is the 1st order network the lower panel, the 2nd order.The black lines is the simulated response, red is measured. The dotted lines show the phase.

Another factor favoring first order is that there are fewer parts, particularly coils (copper isn't cheap, particularly when you're talking about 14 gauge). If I can damp the mid and bass driver oddities at the top end of their ranges by stuffing the cabs, then perhaps the slower roll off isn't such a bad thing...

So it looks like I can get fairly close with the measurement setup as it stands. Clearly measuring the driver performance in the cabs they'll be working in and building the crossovers accordingly is (quite obviously) the way to go. So for the phase V's I'll spend more time measuring the raw driver performance in situ and tweaking the physical design before turning to the simulation and the electrical design. 

Sitting here listening to the results, I'm surprised by what one can get out of the two Silver Flutes which were the cheapest cast frame woofers Madisound had.  Had I not already bought the AC 250s I'd be tempted to build the second cab and stop here. Interestingly I spent more on crossover parts (having now built four variants) than on the drivers, although the parts in the final 2nd order network I'm currently listening to came to about $55. Excluding experimentation and waste the total for half a pair was about $260. Since I think they're now at least as good as my DM6s (which I've seen advertised on the web for $1,000 the pair) which I bought second hand in 1979 for about $2,000 in today's money, I'm feeling fairly smug. 

Finally the philosophical question for the evening (post a smallish celebratory Blue Moon beer). Should I do the measurements in the room in which I will be using them (my home office) where there are all sorts of reflections that confuse things? Or, alternatively I could relocate all the measurement stuff (PC, amp, mic and pre-amp) to the shed and do the measurements in the open air - no walls to mess things up...?