DIY Back Loaded Horn - Dallas III for Fostex 206E

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Hi,

Just want to share my DIY Horn speakers based on the Dallas III and Fostex FE206E. You can read it here. Tell me what you think....

Jason:D
 

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is the thickness of the side walls enough ??

Based on the spacing of the internal supports, yes. However more bracing would be better.( Texas sayin " if more is better then too much is enough)

I ran the side loading sims on a structural loading program that was modified from a building enclosure program
that was altered for internal pressure fluctuations. (blow into a square box and measure the deflection of the sides)

What does the 1-4ohm resistance do?
It will bring up the LF response by raising the Qes which in turn raises the Qts. With the efficency of the 206/Dallas you will be hard pressed to notice any difference in efficency.

Again, tune to your personal desires.

ron
 
I just noticed in your pics the wires hanging out from the driver flange.
ANY leaks in the flange to baffle surface will affect LF performance. The driver flange should be totally sealed with something on the order of silicone sealant.

ron

(the hardest thing you can do is to make something simple)

Now I am not sure if the Dallas III was actually designed by Ron himself

Yep!
 
1. I will try the 1-4ohm resistors and report back as to what works for me.

2. The speakers are all sealed up so there is no way for me to add additional support/bracing unless I cut it open.

3. Yes the pictures do show that the wires are stickin' out and there is no proper seal. That said I very satisfied with Well, I have not installed the binding posts and I have also been asked to try the Coral 8A-40 in these cabinets. Once I have done all this, I shall seal up the cabinets.

4. I guessed that Ron did not design the Dallas III, but after cross referencing the measurements with the Dallas II, all measurements seem to line up. What I am not sure about is if the radiused corners will change the parameters and this the sound all that much....

Jason:D
 
I guessed that Ron did not design the Dallas III, but after cross referencing the measurements with the Dallas II, all measurements seem to line up.

I believe i did, unless it was a drug induced flashback (happens sometimes). My mind is still strong, however as i get older its more analytical and i spend much more time doing the actual math/physics and less dreaming, Maybe there is a downside to getting older, you lose imagination.

ron

I have also been asked to try the Coral 8A-40 in these cabinets.

I designed these cabs specifically for the 206, i cannot garrentee the results with any other driver.
 
Dallas

Ronc, sorry for misunderstanding. Thank you again for the very functional design of the Dallas III horns, I love em to bits. I do understand that the cabs are designed for the 206, but since the corals are such versatile speakers, I'd just like to listen to them in this setup. Plus I am geting the Corals on loan for free... so no harm in trying.

The Dallas III is indeed a beautiful design. I am not so hot for the Dallas and Dallas II though. Here is the side profile fo the Dallas III showing the internal structure...
 

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and the Dallas III... much more attractive, but does the radiused corners affect the parameters and so the sound.... negatively?

Nope! just a gain in efficency because there is less turbulance in the wavefront as it traveles. Down side is a slight increase in mids coming thru the mouth. However the actual horn action begins a slow roll off at 247 hz and ends at around 400 hz. From there the baffle action takes over (overlaps with the horn roll off) and as the frequency increases finally hands off to the driver. The absolute lowest frequencies are a TL action which blend into the lowest horn action at around 120 hz. The higher frequency TL ripples are then blended with the horn action. This results in a smoother mid bass.

However if the drivers are not totally air tight and sealed to the CC then there will be a definate loss in LF response.

ron
 
@ronc, thanks for the expalnation. I breathe a little easier with the knowledge that the decision I made on looks first did not have a negative outcome in terms of the sound.

Roger that on the air tight seal required for good LF response. I will do that as soon as I have the Corals tested in the cabs.

Question: During the build, I tried my best to follow all measurements as closely as possible. But for an amateur like me, it isn't always easy to get everything accurately down to the last milimeter. WHat is the allowed tollerances with regards to the various measurements in the DallasIII? Since I do not have a frame of reference for the Dallas III/Fostex 206, I cannot tell if the speaker sounds as you would have "intended".

Jason:D
 
building me a copy, dallas III

greetings from the netherlands.
i have decided to build a pair of dallas III to match a soon to be mine 2A3 pair of monoblocks.
http://www.dhtrob.com/projecten/magique_1_en.htm
i think this could be a good combination and enter into the realms of the singledriver experience.
dhtrob who build this one plays these amp's using Phy drivers from france.
this, if is the ultimate in his opinion in an open baffle.
for me this would be an option but for the wifey not!!
so my friend who is an excellent carpenter will help me to build your dallas III design.
first i wanted to build the frugal horns, but my livingroom is a rather L-shaped room and from what i read i get more bass with the dallas's and also the wifey likes the optics dallas better, so do i for that matter
i am no expert on electronics so i will stick to your plan on how to build and try refrain from any diversions.
i couldn't find the plans for the dallas III on the frugalhorn site, they look very similar to the dallas II but with all corner excess taken off, is this true?
i like the look of the fostex 208 es but i read they need an extra tweeter, is that so?
so i will try and get my hands on dave's 206 EN

greetings
~joris

--
coffee over soup anyday
 
frugal-phile™
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Re: building me a copy, dallas III

hartgas said:
i couldn't find the plans for the dallas III on the frugalhorn site, they look very similar to the dallas II but with all corner excess taken off, is this true?

No plans for the Dallas III were ever released. It is a "smoothed" version of the Dallas II that Ron & Tony (layertone) worked on. Ron's plans were eaten by Windows. Tony may have them still.

dave
 
Re: Re: building me a copy, dallas III

planet10 said:


........ Ron's plans were eaten by Windows......

dave

I know that feeling well.
I've had a bad day. That comment helped me laugh about it.
Your timing is almost psychic.

There is some information on it here:
http://fullrangedriver.com/gallery/search.php
type in Dallas.

there is a sketch there that could be printed to scale.
 
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