Golden ratio bass horn

[GM]

GM, if you can point out what dimensions you need i will measure that. Horn is 2 small straight sections and 3 circlular sections.

dave

Can your program tell if it's expo, etc.? Regardless, every 3" like shown is plenty good enough and for this horn, maybe every 4" in the last, larger expansion. Once these are known it can be broken down into flat panels to 'trip up' its excessive HF.

GM

 

[planet10]

I can only generate dimensions. 3” apart (at at least 1 end anyway) except where shown. The horn is primamrily formed by 3 circular sections shown in blue, red, purple.

dave

 

[GM]

OK, can you factor in the width to make each 'slice' an area dimension? Also, too little info [for me] to figure the area expansion for the circles. We need somebody with AutoCad......

GM

 

[planet10]

I’m pretty sure my CAD software can do anything AutoCAD can… operator thou is not up to expert level.

dave

 

[globalplayer]

So it is a pi horn and not phi.

 

[GM]

I’m pretty sure my CAD software can do anything AutoCAD can… operator thou is not up to expert level.

dave

Know that problem well, tried to learn AutoCAD in the '90s with zero help and before I got on-line and finally gave up as way too tedious plus the manual apparently assumed I'd taken a course in school.

GM

 

[xrk971]

There’s a parametric curve genrator function. In Solidworks, you can place an image in your sketch plane (from a math plotting program or photo) as a visual guide and use several splines to fit any complex curve you like without entering an equation.

 

[GM]

Thanks!

Hmm, couldn't find a price, so assume only DIYers with 'deep pockets' can afford it.

GM

 

[planet10]

I believe SolidWorks is in the thousands of dollars/seat. The sw i use is just over $1000.

dave

 

[GM]

Thanks! ...like I said....... Oh well, if you can give me enough 'pie slice' areas, I can try empirically finding a 'close enough' flare frequency, factor if it is indeed near enough expo.

GM

 

[planet10]

GM,

If you remind me of how you plot the length around a corner i can develop a map of the points shown into a straight approximation.

dave

 

[GM]

Sweet! Soho's way is the current one [71.4 cm]: http://www.avsforum.com/forum/155-d...-advanced-centerline-method.html#post23714966

GM

 

[planet10]

1st detail translates to the 2nd with length in mm/in and area in cm²

dave

 

[freddi]

with the offset driver - hornresp could use another section to put the driver where it belongs - can't quite fudge it with the last part having length but essentially no expansion. Is there a good fudge with hornresp?

this may be off in expansion - have to look closer at P10's CAD sketch

has anyone simmed this yet?

 

[foreveryoung]

Phase plugs for the drivers, basket damping — and/or more radical mods.

dave

Thanks for the tip!

I've seen a guy modded this plug as well. Does it make any audible difference? Why the speaker driver manufacturer does not use this plug in their products?

 

[planet10]

The plugs make a positive difference IMO. And hundreds of diyers have installed the plugs in their FE20x and i have only gotten positive comments back. Many were “i don’t know why these don’t come factory installed".

I can only guess on that — cost and momentum perhaps — i have not seen any Fostex drivers with phase plugs. Drivers with whizzers seem to universally benefit from phase plugs. But the driver thou that seems to benefit most is the Visaton B200.

dave

 

[Walloffound]

What effect does the phase plug have on the sound? Is there one available for the Visaton bg20?

 

[planet10]

I have my theories. From my web-page:

The phase plugs work primarily 2 fronts. 1st they fill the hole left when the dust cap removed. The air trapped in the cylinder inside the voice coil and above the pole piece causes what is called an "oil-can resonance". This invariably causes some midrange distress. Removal of the dustcap and filling the hole pretty much eliminates this source of coloration. The 2nd thing the phase plug does is to effectively halve the diameter of the cone. Any side-to-side standing waves, reflections, etc are pushed up about an octave. Related to this is an improvement in high frequency dispersion, widening the sweet-spot, and reducing the laser-like hot spot some full-range drivers suffer from. The smaller effective cone diameter means that the point at which beaming starts is pushed up and due to the shaped nature & the hardness of the plugs some HF energy is redirected.

Visaton BG20

Same specification of voice coil as B200 so B200 plugs likely will fit, but you need to remove dustcaps and measure. The FE16x plug is slightly less diameter (and shorter). If the available plug is a bit too large they can be sanded down (which i had to do to use FE10x plugs in the Coral holey basket version of the FE103A).

dave

 

[foreveryoung]

Thanks man, must try then, have a pair of Visaton collecting dust

 

[Walloffound]

1st detail translates to the 2nd with length in mm/in and area in cm²

dave

what exactly does the above drawing and measurement tell you?

i have been listening to these for the past year in my studio and I have really grown to love the sound. I cant quite explain what it is about the sound that is different but it sounds more alive and real especially with acoustic, vocal, jazz etc. i have a tube amp im looking forward to trying it with, a fisher x-202. im considering bringing them home to the livingroom