HalAir Aeralis - Fullrange Line Array (Vifa TC9-18-08)

[Halair]

Many small steps equal...
18awg silver plated copper wire used

 

[Halair]

While I am waiting for the epoxy to arrive I fiddle my thumbs...
Last nite I spent a little time with my mk1´s and enjoying them, couldnt pass by the chance to set mk1 and mk2 side-by-side.

Less is more, unless you stand next to one with more - then less just look stupid

BTW - the epoxy should arrive some time mid-week so I hope I manage a pour before I leave for the weekend

 

[wesayso]

Each time I look at that room I do wonder how it would be to have lines do the ambient thing .

 

[Halair]

I only need to order some more drivers to populate them both

 

[Halair]

BTW - the lack of epoxy provide time to investigate how to arrange a vibration table.

I think this will do it, an universal motor taken from a washing machine, converted to DC operation:

 

[Halair]

Epoxy is in, hope to start casting tonite - next chance is monday or next friday due to travel....

 

[Halair]

First cabinet is cast, it took 45kg of EG (Sand and 12% epoxy) and 6hrs in total. My rig for vibration wasnt powerful enough to make the EG mix "liquify" so I had to manually compact the mix. A 12% EG mix appear quite dry, like moist sand.
Weight of one cabinet is now 70kg. Weight / moving mass ratio is already past 1200:1

So now I hope it all cures good, the oval piping will be removed on Monday if it does. If it doesnt.....

 

[wesayso]

I hope it does cure as planned! My first layer of epoxy did not cure as fast as I thought it would. Making me second guess my mix... It turned out to be just a temperature issue, even though I was heating the place. It just took a bit longer than expected.

 

[Halair]

From yesterday to this morning the mix has firmed up a fair bit so its curing along - so it should be alright. Curing is stated to need 24-72hrs depending on temperature and extent of exothermal reaction. But with sand in the mix there wont be much help from the exotermal reaction (heat build-up during curing).

I am travelling away for the weekend so the cabinet is left alone, with heater on, untill Sunday and should be rock hard by then.
Obvously I did a "knock-test" on it, its like knocking a rock (with wood exteriour)

With epoxy, as long as the epoxy and hardener is good and mixed to right proportions (by weight) and stirred apropriately, curing will be fine - eventually

 

[Halair]

Started to extract the liners, a tedious job due to lack of proper tooling but its coming along

 

[wesayso]

Looking good! Did it turn out like you planned?

 

[Halair]

Yeah, its pretty decent - there are a few holes in thin internal thin walls of the EG, areas where I didnt manage to compact it good enough (or too much too fast) but those are easy to seal.

Here is an informal "tap test" between mk1 and mk2, mk1 is all sealed up and stuffed, mk2 is open on both ends.

You can hear the "tap" is higher in pitch and not as loud.
Video: Mk1 and Mk2 tap test

 

[Halair]

Just minor progress over the weekend, I have filled the interal wall holes that were present due to insufficient packing of the EG-matrix.

Plans for the coming week:

1. Cast the chamber rear wall - aka an "EG-puck" for each chamber
2. In this puck there will be a straw where the speaker wires can pass through
3. Prepare the felt and start lining the chamber walls

 

[Halair]

Small job but a prerequisite for the next one, closing up the chambers. Scheduled for tomorrow
Will need approx 5kg for of EG to seal this deal (..pun intended..)

 

[wesayso]

Only now do I understand what you posted one post up...

 

[Halair]

"A single image is worth a 1000 words..."

The stages I am currently at dont give much visual update, it just looks like the cabinet thats been done for a while now (just heavier,much heavier..)
Hence not much imagery posted...

So plans for today is to make the final cast of EG on the first cabinet, sealing of the rear wall. Then I will quickly start lining the chambers and install all the wiring
If all goes well this first speaker might produce sound this weekend...

Then I can start lining up and casting the 2nd cabinet

 

[Halair]

All those minor steps...

Speaker wire glued in, felt is prepared to be installed over the next few days
Then the drivers will be installed and the stuffing will be sorted out while I resume work on the 2nd cabinet

 

[Halair]

I have a group of 3-4 chambers that sound "hollow" when I tap their back wall (EG puck). It appear that the plate used to line the rear openings, have bent away a few mm for some reason, allowing more of the EG-mass to flow out/up against the side walls. This leave less EG-mass for thickness and apparently didnt seat it fully.

For the time being I will not do anything about this but will see on the impedance sweeps if further action is required. The fix should be straight forward, simply hammer the weak ones out and re-cast. Will investigate.

All chambers are now lined with felt and filled with 10g each with stuffing.
So next job is to temporarely mount the drivers and hook it the first line up

 

[TNT]

I think you are on to something with these cabinets. But maybe you should have made them with a roundover - at least on the front. Diffraction is a bi**h.

This way is definitely inspiration for my next build. Think I will try the new SB 3". Maybe skip the glue and go all in fiber concrete...

//

 

[Halair]

But maybe you should have made them with a roundover - at least on the front. Diffraction is a bi**h.

You mean like this? (see pic, front baffle top with bevelled and rounded edges)

Thank you for the kind words, I hope my project will be worth it i

One note against concrete - it never stop to cure and it will shrink during this process. Fiber reinforcement or aggregate will reduce this.
Its said that concrete shrink about 12mm over a 9m span and it dont take much to split/release from a weak surface.