Rons Austin A126 for the metric freak newbie

[planet10]

Andrew,

I'll get back on the other questions, but i do have DXFs of an iteration of Chad's drawings and have a CAD drawing started -- time for me to finish it.

Our A126 went off to a friend's house for use as "computer" speakers with his new 27" iMac. He has a small room that is particularily synergistic. Performance is staggering.

His are the green drivers with the new underpainting trick i've recently learned (picture doesn't do them justice).

dave

[chrisb]

Originally Posted by jimbro

I am interested in building a pair of A126s too and applaud your ambitions to create a set of definitive plans. I have struggled with some of the same issues you want to address. There is one question that I haven't seen an answer to that may affect your plans. The Fostex 126e has been discontinued and I don't know if the new fe126En will work without modification to the compression chamber. I think I need to hurry and order a set of 126eNs from Planet10 before its too late! I wish I could help but I'm the newest of newbees. Good luck and I'll be watching your progress.

Based on our own and other anecdotal reports, you'd likely be more than happy with which ever version of the FE126E you find in the A126 - but FWIW, I think the polka dots are definitely worthwhile

[andb]

I was just thinking, what about using something like the ikea wooden bowl trick as the SB, for example as posted here: Ikea bowl speaker drivers

[planet10]

Originally Posted by andb

I was just thinking, what about using something like the ikea wooden bowl trick as the SB, for example as posted here

Similar ideas have certainly passed thru my head... just needs to be the right width.

dave

[planet10]

Air Cavity

Compression Chamber is not the correct term. We have found that enlarging it and then adding irregular fill works well.

SupraBaffle

Ron has carefully sized the sB size to flatten response down to meet the output from the horn, you doesn't want to muck with that much.

The best shape is likely a the teardrop shape as exemplified by the midrange pods in the B&W Natilus 800s or the FujitsuTENs.



As to shape, if you look at Page 23 of Olson, you can see that the shape that Ron presents is a really good compromise between best & buildable.

Chrisb rear-mounted the driver in the baffle

Actually in this case the driver is flush mounted to a vestigal baffle and the supraBaffle with built-in waveguide fits over top. This was done a/ so that we could hear the difference with & without sB, and b/ because Chris felt like it

For purely aesthetic reasons, I'm considering adding 3 more layers of wood behind the baffle, to make it look more like a "bubble" then just a baffle.

[/quote] Rounding the bends[/quote]

Ron thot this was a good idea, but it does extend the HF bandwidth of the horn, which in things like the Olson-Nagaoka style horns degrades performance,

Mass loading spaces

You should. Stops cavities from resonating. As in the FH, they can also be opened up to the outside world.

Bracing

I am a big advocate of bracing. Push panel resonances up till they won't get excited.

Front panel across the entire width

No problem

Wiring

Whatever works best for you. We like using single strands of CAT5 (usually cryotreated), for both avoid the wire-wars and maintain frugal-phile(tm) status.

We like to use removable cups so as to maximize future versatility. MPO is that posts should have as little metal in them as possible (ie plastic nuts instead of the big metal ones.

The ones Mark Audio is working on look good (unless, like us, you use double bananas to make comparison swapping easy). Bare wire is the sonically best ternination, the best trick is to use binding posts simply to clamp the bare wire from the drivers to the bare wire from the amp.

Adding a tweeter

I don't feel a tweeter is needed, one on the back can help the power response, but note that with the 4dB padding as in the example you posted the tweeter is 6 dB down on the output of the FE126 so isn't adding very much.

Wood to use

What you suggest is fine.

Making building easier

A dado made by a CNC (one side only) is even easier.

12. Deflector design

Stick to exactly the shape Ron designed. The 2nd version with the deflector inside was i believe still in development, haven't seen any builds of this version.

dave

[acarinanders]

Hi A126 builders. I just wanted to share my experience with this speaker. It is a tricky speaker to build and here are some lessons learnt:

• Doublecheck the ply dimension. 18mm ply is nominal 17.7 mm +0.4, -0,6mm. In my case it was 17.5mm in practice. My ACAD-dwg is based on this dimension. It may seem a little overkill but dimensions and angles must be correct when you build this horn.
• I did the drawing the hard way, first on paper and then in Autocad.
• Once you have the cad drawing, plot the side view in full scale and glue it onto a hardboard. It makes it much easier when you have a master in scale 1:1.
• Cut the parts and verify that they match the template.
• If you want to use my cad-version, all you have to do is to add dimensions and angles in ACAD. I can provide the file and then it is up to you to use it as it is.
• My opinion is that the CC should be 2.2l , the driver itself is 0.26l.
• SB is a great addon, deflector aswell unless you have a subwoofer.
• Ambience tweeter does not kill the fullrange sound. My way of doing it is inspired of The Cyclops 3 Way

Wish you good luck and a pleasant future sounding experience!

//Anders

[Bigun]

Thanks Anders, this is helpful - this design has attracted my attention before. I particularly like your thoughts on the ambience tweeter, I'm thinking it may have application to some of my existing bass-reflex speakers.