Designing a tractrix shape for horn speaker base. - diyAudio
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Old 4th November 2010, 10:47 PM   #1
Join is offline Join  Norway
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Default Designing a tractrix shape for horn speaker base.

Hi!

I have been looking at Lowther's "The Delphic" speaker a while, but I'll never be able to purchase a pair. Found here: www.lowtherloudspeakers.com I own a pair of The Fidelio's now (PM6A's -->going DX3 now), and love them, but can it get better?

The drawings of the Bel Canto and Delphic are not available, but I got permission to change the design of the Fidelio to make the horn exit facing the floor and design my own base. I might choose the Academy for a base start, because the horn look better suited to run to the floor.

The idea is that the base follow a tractrix curve and extend the horn, and even use the floor as a part of the horn. This base is possible to raise or lower to adjust the horn path lenght and the sound after your liking.


Do anyone have a idea of size and tractrix shape it should have? Also, how much clearance from floor to horn mouth? Max/min?

I can see several challenges here:

Reverse-engineer the bass horn-part of the Academy speaker.

Load the data into Hornresp.(or other suiteable application)

Model a round Tractrix shape for the base

Get a promising result.

Create.

Fabricating is less of a problem when all measurements are available. If I got the profile of the base, it's easily machined at work. On the cabinet itself I want to keep the original design just alter the horn exit to work with the base.


Do anyone want to approach the "base-design" and horn exit? If so, I got the drawings and will provide measurements if asked. This is my new 1-3year project to build. I'll possibly do it in this thread later.


Thanks,

Last edited by Join; 4th November 2010 at 10:49 PM.
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Old 8th November 2010, 06:41 PM   #2
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So, got the permission from Lowther to share the drawings with the purpose in mind to reverse-engineer the bass horn. Also alter the cabinet design to fit the base.

Academy overview:
Click the image to open in full size.
What I want to do, is alter the horn so that it exit down to the ground. Then add a Tractrix curved base to adjust horn lenght and mouth, with a design that will work best with the base and floor.
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Old 8th November 2010, 07:00 PM   #3
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The reason I choose the Academy is, I've been told that the reinforcement in the sound are really good over the Fidelio.

Okay, time to find all the S's.

Academy Internals
Click the image to open in full size.

Do anyone got skills in autocad or similar program? I need help analyzing it

All internal panels are 244mm wide and 18mm thick.
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Old 8th November 2010, 08:24 PM   #4
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I just located a picture of a speaker that should be the Delphic.

Click the image to open in full size.

Side-by side with the Academy it look alot like it.

Would love to just use the plans and just move the exit.

Each cabinet will use 2x Lowther DX3 drivers, 15Ohm model in parallel. Hope I get the thiele small parametres for the driver tomorrow.

Last edited by Join; 8th November 2010 at 08:54 PM.
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Old 9th November 2010, 01:05 AM   #5
CLS is offline CLS  Taiwan
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Quote:
Originally Posted by Join View Post
...

Reverse-engineer the bass horn-part of the Academy speaker.

Load the data into Hornresp.(or other suiteable application)

Model a round Tractrix shape for the base


...
Have you done the above?

If yes, you'd have found that interesting yet 'inconvinient' truth about bass horn.

For a start, you don't need very precise dimensions everywhere in the horn.

Overall path length (or sectioned to your liking) and mouth size are 2 essential factors. (Also, the overall size of the complete horn is mostly determined by them.) With these 2, you may start seeing how it works.

And then all others parameters can be tuned by the sims. Hornresp is a wonderful and free tool, and would guide you through the sims.

BTW, for bass, tractrix contour is not a good choice. Try hyperbolic or exponetial
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Old 9th November 2010, 02:18 AM   #6
tinitus is offline tinitus  Europe
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maybe think about whether its made smaller to look nicer ?
if your goal is a better horn, there ought to be better options
appears to be a lot of complications with little gain

should I build a backloaded today, I would consider something like this
but may be less fun, I know
Attached Images
File Type: jpg HORN big mouth.JPG (12.8 KB, 604 views)
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Old 9th November 2010, 02:58 AM   #7
CLS is offline CLS  Taiwan
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That's what I mean 'inconvinient truth' about those commercial designs. I think we shoudn't even call them horns, sort of resonant pipes instead. Bass horn can not be slim and small. That's simply against the physics. (In the photo in #4 post, it seems some kind of mass-load at the 'port'... )

I once back-engineered the Acousta and didn't like what I saw on the sim, so I started over from scratch. That project turned out pretty good, and very big. Full story here: Dilemmas, as always -- BLH vs BVR

If the tolerable size is restricted by practical reasons, then you'd better give up horn and consider BVR or MLTL instead.
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Old 9th November 2010, 03:33 AM   #8
TerryO is offline TerryO  United States
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Lew Hardy used a modified Academy cabinet for his "Vavaldi" speakers. IIRC, he used Lowther 55 drivers with custom phase plugs, a VAPS circuit (an EQ/whatever, designed by Dan Wiggins) and a Visiton super tweeter.
It was probably one of the best speakers that I've heard and was capable of excellent bass. We challeged Lew to play a Drum solo disc and it did shake the room. BTW: it was at least 12 feet away from the nearest wall. I have never heard any Lowther based speaker that could do what Lew was able to get out of his design.

[Edit: He was using Bottlehead 2A3 SET monoblock amps, aproximately 3.5 watts]

Best Regards,
TerryO
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Last edited by TerryO; 9th November 2010 at 03:38 AM. Reason: additional info
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Old 9th November 2010, 04:57 AM   #9
CLS is offline CLS  Taiwan
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This?
6moons audio reviews: Vivaldi Audio Academy

It uses EX3. (US$9k/pr, wow!)

Or another model?
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Old 9th November 2010, 06:06 PM   #10
TerryO is offline TerryO  United States
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Quote:
Originally Posted by CLS View Post
This?
6moons audio reviews: Vivaldi Audio Academy

It uses EX3. (US$9k/pr, wow!)

Or another model?

EX3? Evidently I got that wrong, but what I wrote was off the top of my head (so that probably explains it, "Old Timer's Disease").


Just the same it, the Vavaldi was just an excellent sounding and beautifically finished speaker. If I only had the money..............

Best Regards,
TerryO
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