Monday, 28 December 2015

Alpair 12P MLTLs - Part 4

Day 4 - 4 hours

Goodness, it's over 7 months since my last blog, and over 10 months since I last had chance to play with the speakers. It's fair to say audio has been on a back burner for much of this year, but today I made a little progress with the MLTL speakers :-). But first let's have a look at temperature-watch.

Parts of the country are experiencing terrible flooding, no doubt made worse by the unseasonably mild weather which is probably retaining a lot of moisture. 12 degrees C, mild for the end of December.

So first job was to have a quick tidy, then remember where I'd got to. I'd made a start on routing the first hole for the 12P at the end of the last session, but I was rushing and hadn't noticed that the template had slipped slightly and was no longer centred. Fortunately I noticed in time before serious damage was done. So I marked out the circles with a compass to be sure, then carefully reset the template and clamped well.

More haste less speed. Lesson learnt - measure twice cut once.

The first hole needed three phases. The first was to rout the inner hole for the driver to pass through, 170mm diameter. The plunge cutter only reaches part of the way through the baffle though, so needs cutting from the other side too - the third phase.

The second phase is to rebate the driver, 203mm diameter and 11mm deep. This was a bit of a laborious process as there was a lot of wood to cut away. Here's the finished hole. Note the misalignment from cutting from the front and then the back. This was largely due to the initial cut that had slipped. It shouldn't be a problem though, as long as the driver passes through and the driver makes an air tight seal.

Next was the hole for the Monacor pseudo ribbon I'm going to use to fill the treble out over 12k Hz. I started to cut away the all the wood so the unit sits within a cavity...

...but then decided that I was probably going over the top so then cut full depth before turning over and finishing the cut. Ideally I guess I would have preferred to isolate the driver from the main chamber and the air pressures within, but hopefully it shouldn't make too much difference. I might even add a plate to the back just to seal it.

And here's the two holes viewed from the rear.

Next the 3" port, which requires a 79mm diameter hole. This is perhaps just a little slack, but probably better than being too tight and struggling to insert the port. I can always use a bit of glue or silicon to secure them.

From the rear

And here's the first baffle with the initial holes made. It needs a good clean up and a rear 45 degrees chamfer cutting on the rear of the hole for the 12P. And a check to make sure everything fits of course.

For the second baffle I fully marked out all three holes both front and back first, now I had a little more confidence with what I was doing.

And started with the largest hole for the 12P. Here's the first 170mm diameter hole cut and the start of the wider 203mm rebate.

The finished hole from the rear.

And from the front.

And that was the end of the today's audio fun.

No comments:

Post a Comment