Setting up the speakers in active mode

Having (almost) got myself an active speaker setup (need to check out the effectiveness of my DPDT switch for passive/active switching, suspect inductance still across woofer :-( ), now it's time to set the whole thing up.

I'm using the approach suggested by this blog post, which is basically

• Measure the chassis speakers separately in the box
• Easy to do this now, since I can easily turn one or the other off
• For each speaker
• Adjust response using speaker-specific equalisation, noting carefully the off-axis response and keeping this as smoothly degrading as possible
• Set up the crossover, and measure both together
• Some additional effort is required to ensure they are integrated properly
• Make timing adjustments to ensure the impulse response is the same on both units

Here's my first pass at a setting for the tweeter - I started with this because the tweeter is definitely not affected by any remaining passive crossover components. I shall move the testing outside to reduce reflections, and probably re-do it, but it's illustrative and good practice (as is "I need to practise doing this").

REW plots for tweeter response before/after

You can see that there is a pretty stonking (5dB!) rise from 6k to 10k, which I've EQ'd out. I've also flattened out the bottom end a bit - the blogger mentioned above reckons you need to be pretty flat to 2 octaves above/below crossover frequency, but this tweeter isn't going to do that! Hey, take what you can...

Tweeter on and off-axis response after EQ

Looking at the off-axis response, it looks ok to me. It's quite surprising how the top end holds up.

EQ settings

I've been using AULab to do this, because it's simple (hah!! relatively...) and has graphical interfaces. I tried several EQ tools - High Shelf filter, Parametric, but Graphic EQ provided the most flexibility. I can't believe how easy it is to tweak it and re-test - just imagine how horrible it would be with any kind of passive arrangement! Bleuch.

However, the last measurement I made produced extremely distorted sound, so I saved the AULab document, presumably with all in/out and plug-in settings, and restarted it. However, on reloading the document, I discover that AULab is insisting on Soundflower or Saffire in/out, rather than Soundflower in/Saffire out - to get that I would have to create a new document, which means recreating all the Graphic EQ settings. Sigh. Oh for a text config file and some CLI! The AULab config file is actually XML, but it's pretty impenetrable, and of course, it presumably reflects the same in/out arrangement. Maybe I should raise a bug with Apple?

Right, time to move outside, do some more measurement.