K-402 in wood!

[Arash]

I'm almost disappointed from getting a pair of K402 from US or finding it's plan to build one myself. I'm gonna try to build my own conical-tractrix horn so see how it sounds on-axis/off-axis. designing a horn with conical beginning and tractrix ending is not something very routine. if you have any idea or tip about this it would be great to share it here.

[Chris A]

1 hour ago, Arash said:

...designing a horn with conical beginning and tractrix ending is not something very routine. if you have any idea or tip about this it would be great to share it here.

 

Pay particular attention to the throat geometries first.  It isn't "oblate spheroid" because OS really doesn't work (and not a lot of people understand why this is true).  Look closely at the throat geometry of the K-402 and the K-510 horns. Think about what is really going on there.  If you get this part wrong, the horn will never perform properly in terms of constant wide-band coverage angles.

 

Understand about higher order harmonics (HOMs) propagating out the horn mouth only above the half-wavelength diameter of the throat, and that those HOMs are minimized by smooth, disruption-free horn walls with no acoustic impedance bounces.  And those HOMs really don't propagate at less than 1/4 wavelength from the acoustic center.  This is key.  Read Danley's Unity horn and Synergy horn patents about the effects of HOMs and other non-linear effects behind the mouth of the horn that get filtered out.

 

Other than that, just remember that the construction of a tractrix horn always begins at the mouth, not the throat.  The transition to straight-sided, i.e., NOT conical...a strict "x^2" expansion, is based on the geometries of the desired wide-band coverage angles--vertical and horizontal--which also determines the length of the horn.  Think about how that is constructed. 

 

Think about the length of a conventional tractrix vs. a modified tractrix (of the type of the K-402 and K-510, that is).  There's a big disparity there that most people are not recognizing.  It's the horn mouth size that is controlling, not the horn path length.  Bigger horn mouths (relative to the length of the horn) perform much better in terms of their wide-band controlled coverage performance than conventionally designed horns.

 

Chris

[Marvel]

On 07/14/2017 at 2:18 PM, Chris A said:

Bruce,

 

You would need finished part form precision to about that level to handle the required throat geometries (i.e., rule of thumb is 1/10 wavelength at 10-20 kHz) in order to have HF directivity control to compare with a real K-402.  That's a pretty tough tolerance to attain on the finished part, even if the measurement device has that level of accuracy.  Measurement accuracy is only half the solution...at best.  Fabrication is another issue.

 

Chris

 

I absolutely understand this. 

The manufacturing is probably harder to accomplish, and maintain consistency. Especially on something as large as a k-402. I certainly won't be building any. Regardless the difficulties, it's a design of Roy's.

 

Bruce

[Chris A]

51 minutes ago, Marvel said:

Regardless the difficulties, it's a design of Roy's.

Every horn design is a design of someone. 

 

That doesn't mean that DIY horns are legally precluded--only if the design is protected by a current patent (i.e., not in this case).  I actually applaud those that want to learn more and try it out for themselves via DIY--especially when they can't buy it due to company policy.  Nothing here, including the IP, is under U.S. export control--a subject for which I know a little something about.

 

Chris

[Marvel]

Oh, I'm still thinking of a flatpack of some sort. I think the precision is possible, and I have mulled over different means of construction.

 

B.

[Arash]

On 7/15/2017 at 7:07 PM, Marvel said:

Oh, I'm still thinking of a flatpack of some sort. I think the precision is possible, and I have mulled over different means of construction.

 

B.

We recently acquired a big metal milling machine. this machines are super accurate. far more accurate than wood CNC routers. If I had the drawing of K402 I could build it using slices of BB plywood. it would look generous with plywood. something like Eliptrac but with least sanding needed at last assembly stage.

[DrWho]

11 hours ago, Arash said:

We recently acquired a big metal milling machine. this machines are super accurate. far more accurate than wood CNC routers. If I had the drawing of K402 I could build it using slices of BB plywood. it would look generous with plywood. something like Eliptrac but with least sanding needed at last assembly stage.

A buddy of mine and I are working on exactly the same thing....once we can get our schedules aligned.

 

We won't be doing a K402 though - we'll start with something more K510'ish, but with my own horn recipe, a 1" throat and 900Hz xover target. Once we get the recipe figured out, then we'll try to tackle something larger than a K402 with 2" throat and a multiple entry design like what Chris did with his K402's. This would probably end up flown in the sanctuary at my church. The smaller K510 inspired version is for my 15" 2-ways at home.

 

I've also considered going an alternate route like the EAW Anya system - where they do a vertical line array with horizontal only "horns". This solves the vertical center-to-center spacing problem, and is by far the best sounding PA I've ever heard. In a home setting, it would allow one to completely address all vertical reflections and create a true planar wave through the room. Go with identical rear speakers for a surround setup, add some signal processing, and you can completely null all room modes in all seating locations. You can't get there with the single point source'ish type speakers, but it's also a different type of sound.

[Chief bonehead]

On 7/15/2017 at 9:13 AM, Chris A said:

Every horn design is a design of someone. 

 

That doesn't mean that DIY horns are legally precluded--only if the design is protected by a current patent (i.e., not in this case).  I actually applaud those that want to learn more and try it out for themselves via DIY--especially when they can't buy it due to company policy.  Nothing here, including the IP, is under U.S. export control--a subject for which I know a little something about.

 

Chris

so do your own.....

[Chief bonehead]

23 hours ago, DrWho said:

A buddy of mine and I are working on exactly the same thing....once we can get our schedules aligned.

 

We won't be doing a K402 though - we'll start with something more K510'ish, but with my own horn recipe, a 1" throat and 900Hz xover target. Once we get the recipe figured out, then we'll try to tackle something larger than a K402 with 2" throat and a multiple entry design like what Chris did with his K402's. This would probably end up flown in the sanctuary at my church. The smaller K510 inspired version is for my 15" 2-ways at home.

 

I've also considered going an alternate route like the EAW Anya system - where they do a vertical line array with horizontal only "horns". This solves the vertical center-to-center spacing problem, and is by far the best sounding PA I've ever heard. In a home setting, it would allow one to completely address all vertical reflections and create a true planar wave through the room. Go with identical rear speakers for a surround setup, add some signal processing, and you can completely null all room modes in all seating locations. You can't get there with the single point source'ish type speakers, but it's also a different type of sound.

you know doc, it is truly very difficult to get a "true plane wave".  your sources would have to get smaller and smaller until you reach a large, continuous diap.  that is my problem with so called line arrays,  because of the large compromises in trying to emulate a large diap, the response at different distances, is not consistent because it does not fall off at -3 db at all freqs.....

[Chris A]

3 minutes ago, Chief bonehead said:

so do your own.....

Thanks for permission...and remember that you gave it, too...

 

 

[Chief bonehead]

On 7/14/2017 at 3:54 PM, Chris A said:

 

Pay particular attention to the throat geometries first.  It isn't "oblate spheroid" because OS really doesn't work (and not a lot of people understand why this is true).  Look closely at the throat geometry of the K-402 and the K-510 horns. Think about what is really going on there.  If you get this part wrong, the horn will never perform properly in terms of constant wide-band coverage angles.

 

Understand about higher order harmonics (HOMs) propagating out the horn mouth only above the half-wavelength diameter of the throat, and that those HOMs are minimized by smooth, disruption-free horn walls with no acoustic impedance bounces.  And those HOMs really don't propagate at less than 1/4 wavelength from the acoustic center.  This is key.  Read Danley's Unity horn and Synergy horn patents about the effects of HOMs and other non-linear effects behind the mouth of the horn that get filtered out.

 

Other than that, just remember that the construction of a tractrix horn always begins at the mouth, not the throat.  The transition to straight-sided, i.e., NOT conical...a strict "x^2" expansion, is based on the geometries of the desired wide-band coverage angles--vertical and horizontal--which also determines the length of the horn.  Think about how that is constructed. 

 

Think about the length of a conventional tractrix vs. a modified tractrix (of the type of the K-402 and K-510, that is).  There's a big disparity there that most people are not recognizing.  It's the horn mouth size that is controlling, not the horn path length.  Bigger horn mouths (relative to the length of the horn) perform much better in terms of their wide-band controlled coverage performance than conventionally designed horns.

 

Chris

paying attention to the 20%....

[Chris A]

7 minutes ago, Chief bonehead said:

paying attention to the 20%....

Looking around, I'm amazed at how little that people really listen to each other and consider their ideas without cognitive bias creeping in to preclude their use elsewhere.  This is particularly true of this domain (horns).  It never ceases to amaze me how others get some things right, but steadfastly refuse to acknowledge other's contributions. 

 

Take the "OS" horn geometry, for instance: the author completely refuses to acknowledge the advantages of higher efficiency and the fact that the harmonics that he takes such pains to "absorb" (via patent) aren't really audible because those harmonics are at too high a frequency to hear the higher-order ones.  The same author published a paper on that subject, then failed to use that information in guiding his own horn designs.  Etc., etc., etc.

 

I don't believe it was always like that.  Horn design and amplifier design in the early days were "borrowed" by other enterprises very rapidly, thus ushering in the renaissance in sound reproduction in the 1930s(ff) that we still are feeding off of today for understanding the physics and engineering of horn-loaded loudspeakers, etc.  Same thing in the 1950s with "small loudspeakers" (Villchur, et al. direct radiators in acoustic suspension enclosures, bass reflex, etc.). 

 

Those basic ideas haven't really changed but the tools of design, test, and implementation (e.g., DSP crossovers, much less expensive amplifier power, better designed low-distortion SS amplifiers, etc.) have as well as the understanding of the additional design requirements that were missed back then, e.g., low HOM distortion (i.e., avoiding slots in horn throats), uniform controlled coverage vs. frequency, the limitations of high frequencies going around the curvature of curved horn walls, avoiding diffraction (line arrays are the poster child for diffraction), recognizing the shape of the developing acoustic wave must conform to the expansion profile, etc. 

 

Those new requirements are the things that seem to change and those changes lead to changes in design.

 

Chris

[DrWho]

On 7/18/2017 at 9:50 AM, Chief bonehead said:

you know doc, it is truly very difficult to get a "true plane wave".  your sources would have to get smaller and smaller until you reach a large, continuous diap.  that is my problem with so called line arrays,  because of the large compromises in trying to emulate a large diap, the response at different distances, is not consistent because it does not fall off at -3 db at all freqs.....

Ya, we are in full agreement here. However, that "smaller and smaller" needs to be considered relative to wavelength.

 

Nobody said each element in the array needs to be reproducing the same frequency content. Nor did we say we need more than one element reproducing the highest frequencies. We also don't need to target a plane wave either (I can think of a lot of reasons why we wouldn't want to anyway).

 

When I think of arrays, I think of them as k factor radiators with a very intentional polar shape (that isn't a plane wave). I think the Anya DSP algorithms are taking a similar approach, but if they're not, then I guess I'm off doing my own thing. My only point is that the classic line array design pushes themselves into a corner that they don't need to be in. They're too obsessed with max SPL. The absence of vertical horn flares in the Anya system lets you have any vertical polar shape that you want. I don't need a hundred drivers reproducing 20kHz - that's way too much k factor. Maybe one is enough. But I definitely want a hundred of those same drivers reproducing 200Hz. It's just how the k factor works out, and unfortunately we can't do anything to change the size of our wavelengths. Thankfully inter-driver spacing matters a lot less at 200Hz.

 

Anyways, that's way off on a tangent and it's not possible to discuss some of the nuances without a real system. At the rate my ideas materialize it will be several years, but I'm confident in this vision. There's some low hanging fruit that's been ignored....likely because everyone in the audio industry is so focused on individual boxes performing specific functions - and that's about all I'm going to say on this subject until I roll out the entire package. Proof is in the pudding, but I'm still trying to figure out how to get milk from a rock first.

[Chief bonehead]

On July 19, 2017 at 2:04 PM, DrWho said:

Ya, we are in full agreement here. However, that "smaller and smaller" needs to be considered relative to wavelength.

 

Nobody said each element in the array needs to be reproducing the same frequency content. Nor did we say we need more than one element reproducing the highest frequencies. We also don't need to target a plane wave either (I can think of a lot of reasons why we wouldn't want to anyway).

 

When I think of arrays, I think of them as k factor radiators with a very intentional polar shape (that isn't a plane wave). I think the Anya DSP algorithms are taking a similar approach, but if they're not, then I guess I'm off doing my own thing. My only point is that the classic line array design pushes themselves into a corner that they don't need to be in. They're too obsessed with max SPL. The absence of vertical horn flares in the Anya system lets you have any vertical polar shape that you want. I don't need a hundred drivers reproducing 20kHz - that's way too much k factor. Maybe one is enough. But I definitely want a hundred of those same drivers reproducing 200Hz. It's just how the k factor works out, and unfortunately we can't do anything to change the size of our wavelengths. Thankfully inter-driver spacing matters a lot less at 200Hz.

 

Anyways, that's way off on a tangent and it's not possible to discuss some of the nuances without a real system. At the rate my ideas materialize it will be several years, but I'm confident in this vision. There's some low hanging fruit that's been ignored....likely because everyone in the audio industry is so focused on individual boxes performing specific functions - and that's about all I'm going to say on this subject until I roll out the entire package. Proof is in the pudding, but I'm still trying to figure out how to get milk from a rock first.

Kinda sounds like what we did with the kp-600 as far as having different bandwidths reproduced. We did some experiments doing what you are talking about. Yielded some excellent data and obeservations......for future stuff. 

[DrWho]

I think one of the enlightening things about the KP600 is the focus on musical energy/bandwidths.... I think it's mentioned in the crossover literature, but I remember reading it many years ago and a ton of things suddenly clicked into focus. Ideally the system is faithful to all input sources, but the reality is that music isn't an equal distribution of energy across all frequencies.

 

I'd love to see (hear?) the fruits of your experiments some day.

[ARX]

Arash, with regards to horns in general and specifically: tractrix horns and waveguides, I have read other threads in which you share plans and experiments with Faital Pro drivers, the LTH-142 horn as well as the 18Sound XT1464. You have also expressed a preference for the XT1464.

As I am working on a similar Klipsch / Altec inspired 2 way, I would be interested to learn the aspects in favour of XT1464. By the way, I share your preference for phenolic diaphragms over titanium. Therefore, the HF146 is on my driver shortlist.

Edited September 4, 2017 by ARX

[Ljk]

On 7/14/2017 at 2:18 PM, Chris A said:

If you get a template of the 402,s top and one side you could make a press like in the pictures. 

 

[carlthess40]

Who if any one in or near Orlando have a set of the k-402's ? I would live to see and hear them In person. I would love the Challenge of making them out of wood. I've had great luck with steam bending and shaping wood

If someone could PM, email , text me if they would let me check them out. Thanks Carl Hess

carlthess@icloud.com

321-262-9458

 

 

Sent from my iPhone using Tapatalk

 

[Arash]

if finally anyone can provide a 3D scan of K402 I would build it using BB plywood and submit a thread with tenths of pictures for details just like other threads of mine.

[Ljk]

Could someone post a few side and top shots of k 402, full body with camera centered on middle of horn?