Thursday, 8 January 2015

FRANKENKEILIDHS - Zombie Speakers Rise Up: PART 4

PART 1 here
PART 2 here
PART 3 here

I only have reasonably basic tools available, so no fancy routing of baffles or anything like that.

Let's start at the back of the cabinets.  Normally, Keilidhs have 6 terminals on the back panel to facilitate connecting up to 3 pairs of cables from 3 amps.  They're an integral part of the crossover circuit board and, once the external collars are screwed onto the posts, hold the crossover into the cabinet:

Original Keilidh Crossover (from www.costrruirehifi.net)
So, no crossover also means no binding posts to connect speaker cables to.

I also decided that I wanted to make conversion of Frankenkeilidhs from passive to active and back again as easily as possible, as I have a vague idea that I'd like to play with some low cost DSP crossovers at some point.  So the approach is just to fit a set of terminals into the existing holes in the back panel of the Keilidhs and connect them directly to each of the speaker drivers, thus avoiding the need to house a crossover inside the cabinet, and facilitate active conversion without opening the boxes up again.

ebay again and some nice looking binding posts were sourced at £1.95 a pair.  They claim to be gold plated and look the part.  I guess we'll know in a year or two's time how true that is.  Anyway, they're long, substantial and provide the option of bare wire or 4mm banana plug connections.


One binding post stripped down to its parts, ready to fit

For speaker cables, I'm using some high purity 42 strand copper cable from Maplin - its left over from a 50m drum that was bought when putting the garden speakers in place.  Do I cost it in or not?


Tining up the speaker cables ready for soldering to the binding posts
The sequence for building up the posts, cables and cabinet need to go in the right order to avoid re-work by doing silly things like soldering up and having no nuts to tighten the posts in place. Fortunately, and unusually for me, I got the sequence right on all 12 posts.
At this level of quality, it probably doesn't matter at all, but I did as many of the little things as right as I could, as you might as well, if you're going to put the time in and it doesn't make a material difference to the costs.  So each of the 3 internal cables and across both pairs are identical lengths. Just in case it makes the tiniest of differences.

This is from inside the cabinet.  Thread the nuts onto the cable, then thread the cable through to the outside of the cabinet.  Note there are no plastic washers on this side as they're only need for identification or to isolate the post from the cabinet.  MDF is insulator enough.

Threaded through to the outside


Fit the plastic red or black washer first (for easier identification of + and - terminals), then the clear washer

I soldered the binding posts after threading the washers onto the cable (picture above), but before installing the binding posts into the cabinet.  This allows soldering of wires to posts outside the cabinet, making the job much easier than doing that job inside the cabinet

Then push the binding posts into place and tighten the nuts from the inside of the cabinet

Here all 6 posts are completed on the inside of the cabinet

And from the outside - looking very professional, even if I do say so myself!




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