Yet another DIY AMT

[solhaga]

Just got some 4x4 mm and 5x5 mm iron bars , so the tweaking begins!

 

[solhaga]

5x5 rods

First tests with 16 5x5 iron bars:

With a wave guide for 800 Hz I get:

Ideal to XO at 800 Hz @ 24 dB/octave. Only one EQ -6 dB at 10 kHz and Q=1,24. That is acceptable in my opinion.

I also tested with 12 and 8 bars but only got lower SPL (-2 and -4 dB lower)
In fact, I also tested without any bars at all and got even lower SPL (another -6 dB) plus a distortion level at -50 dB.
Unusable for sound reproduction of course, but it opens up an easy way to tweak the membrane and its fastening to the structure and then make comparative measurements.

 

[Greebster]

Good idea with etching away some aluminium after the trace cutting.
If the etchant (Natriumperoxidisulfate) is stired during etching it should be even.
It is also important that the temperature doesn´t rise.
Perhaps one can measure the resistance during etching and just stop (pull out and rinse) when desired resistance is reached?

It should be easy to test with a leftover membrane.

I would not recommend etching the al thinner. It wont be even and will find any weakness in the metal eat through that point first. Even if measures ok it may sound good at 0.5w but at 3 a dead duck.

 

[solhaga]

Thanks for your caveat.
It is still worth a try on a leftover membrane or why not on a single aluminium strip.

 

[Greebster]

Thanks for your caveat.
It is still worth a try on a leftover membrane or why not on a single aluminium strip.

For an experiment sure, by all means please do test

My experience with plating and etching span some >35 years. Regardless of irrigation, fluid flow, temperature etc have never seen metals removed evenly, especially along the edges where the metal is undercut.

 

[solhaga]

Yes, such a test will most probably fail.
However, this is not my top priority right now. Perhaps I´ll test it some rainy day.
Actually, as seen from post #262, the HF looks really good with only some EQ.

 

[Greebster]

You're getting very good results thus far and looks well designed/made

I'll build another, one of these days for sure. Would have about 6 months ago but the total cost of the current project (going from nothing to all at once) left little for R&D

 

[SEdwards]

Hey guys,

As far as etching goes, I did an experiment last week and eventually the etchant did find a weak spot. Stil, though, that took a reasonably long time. I will experiment with it further when I have a chance.

Another idea - how about electroplating more Al on BoPET film? Could this be done relatively evenly?

 

[solhaga]

Another idea - how about electroplating more Al on BoPET film?

This is maybe a start.

 

[Greebster]

https://en.wikipedia.org/wiki/Anodizing

It is non conductive and too brittle at the thickness we would require

 

[solhaga]

Of course, how silly of me to suggest it.

 

[angeloitacare]

Here is the patent of Jack R. Smiley, which is the inventor of the air motion transformer sold through Paul Squillo :

What?s New | Paul Squillo Music Systems

Loudspeaker apparatus - Smiley, Jack R.

 

[solhaga]

In the frequency response curves, the distortion looks a little bit high.
Or am I misinterpreting the curves?

 

[angeloitacare]

hi Solhaga

yes, it seems so. Wondering how that would effect sound.

 

[Greebster]

Here is the patent of Jack R. Smiley, which is the inventor of the air motion transformer sold through Paul Squillo :

What?s New | Paul Squillo Music Systems

Loudspeaker apparatus - Smiley, Jack R.

A dipole AMT with a tuned rear cavity and (poor) horn loading, yawn, did I miss anything?

 

[solhaga]

Newmotor, new waveguide, new setup.

Still have to do new membranes to the new motor as it is somewhat wider and double the height of the old one.
I plan to have two membranes in series for each motor.

 

[båndsei]

Wow
Those are big
Even the 15" speakers looks small.
It is a good idea to make 2 diaphragms .
How many pleats? Width,depth and hight?
Do you need 7my alu/paper? I got some.I have 10my alu/paper too.

Bernt

 

[solhaga]

The waveguides are "tuned" to 500 Hz.

Alu/space ratio is 5/3 mm and fold ratio 6,5/1,5 mm, pattern is attached.

Since the trip to Copenhagen this summer I have all the 10 um alu/paper I need, thank you for the tip on where to find it

.

 

[Rullknufs]

Is that the AE TD15M?

 

[solhaga]

It is the AE TD15H with Apollo upgrade.
I'm currently XO at 500 Hz @ 24 dB/octave.