Good advice to home-constructors:

Putting a crossover together - like a slightly complicated one used for the Acapella - takes utmost care. Please read here before you finalise any speaker construction. Thanks to NN for the response. Before I take my speakers from the workshop to the livingroom, I usually check by measurements to see if everything performs as intended. Once in the livingroom I check once more with a test CD (Sound Check by Alan Parson and Stephen Court, highly recommended) to check phase performance for bass, lower mid, upper mid and treble.

Hi, Troels.

I don’t know if you remember my previous emails, 3-6months ago commenting that on my LWJs I found them a little veiled and the imaging not particularly precise and solid. I’d used the SE cabs (42L) for my LWJ so I had put about 5-6L of sand bags in the cabs to reduce the volume as I thought maybe the larger cab may have affected the transient response. It did help but didn’t eliminate the problem entirely. So, I decreased the mid + tweeter attenuation to give it a bit more “life”. Again it sounded better to my ears but I was never totally happy with them. I also put acoustic padding on the open back panel, little difference.

I was rewiring the mid + tweeter internal cabling for the LWJs last week and I must have made a mistake because the imaging became indistinct and skewed to one side. I couldn’t figure out where the problem was so I had to look through the entire crossover network to figure out what the problem was. In the end I realized I had wired the mid + tweeter out of phase with the bass in one speaker and I had incorrectly bypass the attenuation of tweeter in the other speaker. But during the troubleshooting, I had discovered after all this time (at least 12 months) I had incorrectly wired the bass crossover. I was both devastated that I had been listening to an incorrectly wired speaker for so long, and delighted at the same time, that I had finally found the source of my problems. I had basically put the 1ohm resistor in the bass circuit in series instead of in parallel. The thing is, I couldn’t believe what a huge difference it made. The bass is now tight and upper + mids are unclouded. The LWJs are definitely now all that I’d expected them to be. They now sound bright where as once upon a time they sounded dull. I guess I'm going to have to bring the tweeter/mid attenuation back to normal.

So if anyone has any gripes about your designs in future, get them to check the crossover.

Now with a couple of new “high-end” design (Ekta and Sahara), do you still consider the Acapellas the best speaker you’ve built? They are definitely the best I’ve heard (including recently $A17K Dynaudio C2 Confidence with $20K Chord CD player (Blue + DAC64) + $A40K of Chord pre/power amp - very, very detailed but a bit lean, even bright and harsh at times for me. Surprisingly disappointing for a $A77K system.) 

(The Acapella SE is still my #1 speaker. Troels G.)

The 1 ohm resistor in the Acapella LWJ bass crossover section has to be in series with the capacitor and connected to ground.