Looks like a good start to me for damping 
And good job on the build too!!, however it's too bad it had to be made from mdf If you like what you hear when your ready to fire them up (and I'm sure you will), it would be a great improvement to make another set out of Baltic Birch ply or equivalent, instead of mdf ... Dave
And good job on the build too!!, however it's too bad it had to be made from mdf If you like what you hear when your ready to fire them up (and I'm sure you will), it would be a great improvement to make another set out of Baltic Birch ply or equivalent, instead of mdf ... Dave
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In a post on the old Fullrange forum, the designer stated IIRC.
Put some felt in the bends, and add 1-4 Ohm series resistance to taste.
This is paraphrased, of course, but he did recomend damping the outside of the 2 bends, and adding a small amount of resistance to taste. I believe he also said something about the chamber behind the driver too.
If I can ever get off my A$$, I've got a pair of Dallas II's to finish too.
John
The forum is searchable, and that's how I found the above. I do not remember the search terms I used, sorry. I found the above when researching my build.
Good looking build BTW.
Put some felt in the bends, and add 1-4 Ohm series resistance to taste.
This is paraphrased, of course, but he did recomend damping the outside of the 2 bends, and adding a small amount of resistance to taste. I believe he also said something about the chamber behind the driver too.
If I can ever get off my A$$, I've got a pair of Dallas II's to finish too.
John
The forum is searchable, and that's how I found the above. I do not remember the search terms I used, sorry. I found the above when researching my build.
Good looking build BTW.
What material have you used in the closed triangular cavities, Martin?
Cheers,
Wayne
Hi all - re the above bit about the chamber behind the driver, has anyone got any more detailed advice on what material and exactly where? Many thanks in advance.
Cheers
Wayne
Hi there, I am not using any damping material and was looking for info on its necessity. I even measured my Dallas IIs, and yes, the horn reacts exactly like a horn is supposed to do, with resonances at logarithmically even spaced intervals. I do not notice any of the famed "shout" in my speakers, and they sound good to me, without damping.
BTW, resistance in series, why would it be necessary? I understand that it would reduce the sensitivity, but this can't really improve the sound regardless of the amp powering the speakers, or?
BTW, resistance in series, why would it be necessary? I understand that it would reduce the sensitivity, but this can't really improve the sound regardless of the amp powering the speakers, or?
The series resistance will raise the Q of the driver. Which will enhance the Transmission Line effect of the long horn path. Should bring up the bass too.
I've never tried any resistance on mine. I have tried all manner of damping in the chamber behind the driver, as well as none.
I have a "hollowness" in mine in the lower midrange I can't seem to get rid of.
Love the bass I get out of mine, and as long as not on axis with the drivers they sound very good otherwise.
John
I've never tried any resistance on mine. I have tried all manner of damping in the chamber behind the driver, as well as none.
I have a "hollowness" in mine in the lower midrange I can't seem to get rid of.
Love the bass I get out of mine, and as long as not on axis with the drivers they sound very good otherwise.
John
Strange..
Did you use Baltic Birch plywood, or was it something else?. You could try measuring them with a microphone and compare with the curves I've got on mine..
Mine are BB naval plywood, 18 mm 13 layers, for both the outside and the inside parts. The 4 empty cavities are filled with play sand.
BTW, raising the Q - as long as there is no ringing or overdamping in the speaker (measurable with an oscilloscope and a square signal applied through the amp), I think it's no use to modify the damping. Besides, on a tube amp, the advantage given by the low feedback and damping factors are lost - the bass might sound louder, but the overall quality is probably reduced by this distorsion.
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Dallas 2 cabinets - material behind driver?
Hi - does anyone know what material's been used behind the driver? Just acoustic foam??
Hi - does anyone know what material's been used behind the driver? Just acoustic foam??
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Looks like it. I don't think it's too important, some wool felt might be OK. After reading most of the postings I could find by Ron, in the last few months, he does emphasise his designs need minimal damping even in the back chamber. The shape of the volume there is designed to cancel most midrange modes. He did at one stage discuss making the surfaces of those panels behind the driver 'rippled' to kill any HF modes.
A friend of mine is hoping to make a Dallas II fairly soon so I'm looking forward to hearing what it can do - I'm very interested in how his unique design methods worked out.
A friend of mine is hoping to make a Dallas II fairly soon so I'm looking forward to hearing what it can do - I'm very interested in how his unique design methods worked out.
Hi mate - Did your friend ever build the Dallas II’s? I’ve STILL not finished mine (pneumonia, appendicitis, 3 hernias.....and becoming a Dad.....have kinda set me back a bit! Lol). Any damping tips?
Crikey - sounds like a nightmare !
No, sorry to report no build of Dallas yet. He's been set back for one thing by work overload recently as his company had to prepare for Brexit in March, then backtrack, and now are having to prepare seriously again. He's not had enough time & energy to get the project going.
I'm in the meantime just about to try a build of one of Horst Moeller's double-horns, which we hope can be compared to the Dallas at some stage. I have got the ply and damping fibreboard ...
No, sorry to report no build of Dallas yet. He's been set back for one thing by work overload recently as his company had to prepare for Brexit in March, then backtrack, and now are having to prepare seriously again. He's not had enough time & energy to get the project going.
I'm in the meantime just about to try a build of one of Horst Moeller's double-horns, which we hope can be compared to the Dallas at some stage. I have got the ply and damping fibreboard ...
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