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A K-402-Based Full-Range Multiple-Entry Horn


Chris A

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8 hours ago, Chris A said:

It looks as if you're trying to justify the SEOS-30.  Good luck.

 

Being the OP (and the originator of the K-402-MEH), I don't really want to deal with "small syns" in this thread, i.e., those MEHs requiring separate bass bins.  Would it be too much to ask you to move to a new thread that discusses that particular subject (small MEHs requiring separate bass bins)?  This is the only thread on the web that I'm aware of that is discussing full-range MEHs, and your subject isn't a full-range MEH.

 

No, I'm just looking for an alternative to the K-402 given its high cost and unavailabilty in Europe. But if you're not interested in any such discussion that's fine and I shall oblige.

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I think it's reasonable to ask that you start a new thread on smaller MEHs.  I can do that for you if it's an issue for you in creating one.  I think that subject of DIY MEHs probably needs to be expanded to at least two threads--with one thread focused more on the smaller MEHs--which have also been popular on diyAudio.  I believe that you're going to get more constructive comments in a new thread focused on that subject than you will here.  I think that path is a much better alternative than adding to the length of this current thread--which is already fairly long (IMO). 

 

This thread was started five years ago to document my experiences with the K-402-based MEH.  I would like to see the comments in this thread stay focused on the K-402-MEH for those that are building them--and we have a few people doing that right now.

 

EDIT: I will start a new thread to facilitate this under Technical/Modifications section of the forum (the same section as this thread).  If that thread becomes focused on SEOS-30 horn use, I can easily rename it as such at a later time.

 

That new thread can be found here:

 

 

Chris

 

 

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Posted (edited)
On 3/31/2021 at 9:33 AM, Chris A said:

The problem that arises in placing the (off-axis) woofer ports across the middle of the horn walls is that it degrades the most important loudspeaker capability: consistent polar directivity/coverage.  The reason why Danley places these ports in the creases or corners of the rectangular or square horn is that their placement degrades the polar directivity at the frequencies associated with the crossover region (otherwise called "sound power smoothness" in the pie chart below which is condensed down from Sean Olive's linear decision model for loudspeaker preferences--US 8311232)--which is the most important determinant of loudspeaker preference (i.e., more important than flat on-axis SPL).  Placing the woofer port in the middle of a horn wall is absolutely the worst place you can put them, IMHO:

 

Sean Olive Loudspeaker Preference Factors.gif

 

Apparently the guys over on diyAudio don't let little things like that bother them... :wink:  My woofer ports take after Danley's Synergy and Unity horns, both in their placement and their size. 

 

So the area placement and magnitude of the off-axis (woofer) ports is a tradeoff variable.  This is one reason why I set the 10:1 "compression ratio" of woofer cone area to woofer port area, which is high n terms of horn compression ratios.  The reason for keeping this compression ratio under 10:1 is the preserve the efficiency of the low frequency portion of the horn, which is directly affected by the compression ratio used (i.e., inverse relationship between compression ratio and efficiency). 

 

 

 

Chris

 

 

The new thread "Nearly Full-Range MEHs"  inspired me to check out the last few pages of this thread, and i saw this reply in regard to my placement of woofer ports in the center of the horn, rather than in the horn corners (off-axis ports ).

 

I have not found ports in the center to degrade consistent polar directivity/coverage.  Surprisingly not, given the nearly universal opinion that they would.

 

In the first year of building MEH prototypes, i kept ports in the corners like seen in all of Danley's Synergies.  I called the prototypes Syn1, Syn 2, etc.

They developed into Syn5,  which was my first "built to keep"  MEH.  All along the prototype process, I measured the polar response of the horns without any ports in them to be able to see the effect the ports would have on polars, once the ports were in place.

I should stop and say, all my MEH builds have been with a CD that can go low enough to crossover straight to a pair of 12"s , without any additional smaller mids.  And all cross to a sub at 100Hz.    (Before beginning any prototyping, I had the opportunity and pleasure to discuss my plans with Tom D at a trade show a couple of years ago, and ask him questions . What a nice helpful guy !!!)

 

Ok, continuing on...    Syn5 with its off-axis ports was (still is) a huge success for me.   Great sound, with nice polars. 

But it was very heavy, with the woofers mounted on the horns sides, enclosed in cabinetry to form a big box.  By the time I added secondary flares, the speaker became unmovable without some disassembly. Since much of my listening and testing is outdoors, the big guy became a bit of a PIA to move in and out.

 

So i started scratching my head on how to save weight, and the idea hit me that if the woofers went on the top and bottom of the horn, a natural way to seal them up existed without having to build a box around them. Like in this pict.. (which is using an 8" woofer) (The ports way out in the horn are reflex ports.)

1057552560_syn8top.thumb.jpg.1c95797e228609282f766ffcae3b9c84.jpg

 

 

But as you can see, this precludes putting the ports deeply into the horn's corners. 

 

So i decided to stop and do some feasibility testing with regard to port sizes and placements. I first made a simple test box, like a normal speaker, where i put a plate with the port in it over the driver to measure response.  A single center port easily and always, had the smoother response as well as higher extension, than  ports moved out towards or even partially under the surround.  I kept total port area a constant 1/10th Sd wherever located, and however shaped.

 

I then know if i can, i want a center port.  But will it mess up polars? 

I build another horn without ports, measure its polars, then put the round center ports in the horn and measure again.

Heck yes!!   I find  i can get polars nearly as nice as when using off-axis ports! 

 

My current belief is that the reason DSL puts ports in the corners is about minimizing  their small mids' port distance to the CD to get their response to reach up to the CD.

And probably just as big a reason, is actually getting 4 of the dang things to fit in the box along with woofers. 

 

Maybe the small ports closer to the CD throat have a truly disruptive effect on pattern, i dunno at all. 

But i do know bigger woofer ports, with centers at 5"+ from CD don't seem to mess up pattern more so than corner ports.

Mouth termination, secondary flares, etc...appears to matter a great deal more to straight-sided conical horn polars.

 

(The pict eventually became Syn8.  So far my favorite is Syn7, the same style box, that uses a pair of 10"s.)

Edited by gnarly
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1 hour ago, gnarly said:

I find  i can get polars nearly as nice as when using off-axis ports! 

"In God we trust...everyone else bring data."

 

Do you have some polar sonograms of the differences?  I would be extremely interested in seeing that data.  That's a lot of work that can be shared or perhaps leveraged with others tackling the same MEH design problems.

 

Some of the above leads me to believe that there is a fair amount of guesswork still occurring without a full study of the effects of where to put the woofer/midrange ports  and how big/their shape should be.  (I.e., if what you say is true, then Danley isn't putting the ports in the corners of the horn for polar consistency purposes--which I do find both interesting and hard to believe.)

 

There is quite a lot going on in terms of frequency-dependent reflections (like optics) and less-than-half-wavelength volume and area support of the developing waves going (like horns operating near their axial 1/4 wavelength frequency or operating loudspeakers below the transition frequency of a room), with a seamless transition between the two right around these extra (non-throat) ports.

 

I suppose you have found that crossing the lower frequency drivers to the higher frequency ones actually require a bit of overlap (or at least a "zero lap" on the 1/4 wavelength from the throat entrance plane (i.e., not the acoustic center of the attached driver).  I believe that each MEH DIYer is rolling their own, and not really discussing the tradeoffs of where to cross.  I've found that crossing the higher frequency driver right at or just below (in frequency) to the natural bounce frequency of the lower frequency drivers smooths out the phase and SPL response, and the polar response (to some degree). 

 

Chris

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Posted (edited)
1 hour ago, Chris A said:

"In God we trust...everyone else bring data". 

 

Do you have some polar sonograms of the differences?  I would be extremely interested in seeing that data.  That's a lot of work that can be shared or perhaps leveraged with others tackling the same MEH design problems.

 

Some of the above leads me to believe that there is a fair amount of guesswork still occurring without a full study of the effects of where to put the woofer/midrange ports  and how big/their shape should be.  (I.e., if what you say is true, then Danley isn't putting the ports in the corners of the horn for polar consistency purposes--which I do find both interesting and hard to believe.)

 

There is quite a lot going on in terms of frequency-dependent reflections (like optics) and less-than-half-wavelength volume and area support of the developing waves going (like horns operating near their axial 1/4 wavelength frequency or operating loudspeakers below the transition frequency of a room), with a seamless transition between the two right around these extra (non-throat) ports.

 

I suppose you have found that crossing the lower frequency drivers to the higher frequency ones actually require a bit of overlap (or at least a "zero lap" on the 1/4 wavelength from the throat entrance plane (i.e., not the acoustic center of the attached driver).  I believe that each MEH DIYer is rolling their own, and not really discussing the tradeoffs of where to cross.  I've found that crossing the higher frequency driver right at or just below (in frequency) to the natural bounce frequency of the lower frequency drivers smooths out the phase and SPL response, and the polar response (to some degree). 

 

Chris

Here's some horiz polars  that uses two 10" woofers with centered ports as shown in previous pict.  It's a 90x60, 48"x29", build.

10 deg increments.  Black is on-axis. Downward sloping response  is intentional.

 

For polars of builds with off-axis ports, i'd like to refer folks to https://www.diyaudio.com/forums/multi-way/340480-100hz-synergy-project.html

It was the thread i started that has the early MEH protos, all with corner ports.  Polars are scattered in the thread.  I found some on page 5 & 8.

I'd post some here, but would have to dig through an old balking laptop.

 

I completely agree as to the amount of guesswork floating around.  I have a number of things in mind to try still, about stuff i plain don't understand like how the big mids consistently measure further away than the CD.

It's clear to me you understand the physics of what's going on much better than i.  But i keep learning...

 

I've found i can cross about anywhere in between the intersection of how low will the CD go, and how high will the big mids go.

So that typically means anywhere between 450 to 700Hz.  I let polars do most the decision making.

It's a real beauty of steep linear phase xovers imo, being able to move xover freq  easily leaving frequency and phase response unaffected on-axis. After moving xover, i just see how well it holds up off-axis.

That said, I do want to more thoroughly check out polars with shallower slope xovers .

 

 

syn7b polars.JPG

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1 hour ago, gnarly said:

It's clear to me you understand the physics of what's going on much better than i.  But i keep learning...

I was describing the changes in acoustic behavior as the frequencies decrease (i.e., the wavelengths are increasing) to where the distance from the throat to the beginning edge or lip of the off-axis ports is several wavelengths, then eventually it's at one wavelength (i.e., an acoustic impedance bounce--generally attenuating, and eventually the wavelengths correspond to a half wavelength to the horn throat (generally a resonance frequency), and then finally a quarter wavelength (where there is strong attenuation/ cancellation). 

 

At shorter wavelengths, the side walls behave more like canted outward mirrors as in optics.  At the one wavelength, half wavelength, and quarter wavelength points, the idea is that the horn volume behaves more like a resonant chamber and the volume geometries become important, not just the side wall area presented.  Remember that a horn is first and foremost an acoustic impedance transformer, then it can be viewed as a acoustic wave director--creating directivity in the emitted acoustic energy field.

 

At the first notch frequency of the woofers, you're seeing 1/4 wave volume resonance effects (very distantly reminiscent of a Helmholtz resonator).  But what the behavior actually changes to is a function of the exact geometry of the throat-end section of the horn bounded on the outboard side by the lip of the off-axis ports.  If those port edges or lips happen to be located at a pressure (or perhaps velocity) maximum for the resonant waves going by, then more disruption and attenuation occurs.  So the idea is that the pressure waves (or perhaps velocity waves) are maximal at the middle of the horn walls (but perhaps not, depending on wavelength).  For the geometries of the horn used, perhaps the local pressure or velocity max  regions shift toward the creases or internal edges of the horn.  So it isn't really clear what the dynamics of the acoustic waves are actually doing around the off-axis ports--it's probably complex. 

 

The first bet, however (i.e., Occam's Razor) is that the mid-walls are where the influence from the side walls is minimal, and therefore where you don't want to put a penetration through the horn wall.  That's the reason for avoiding placing the ports at the midpoint between the walls. 

 

However...

 

Chris

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I have been wondering for some time, weather it makes a difference, where the off-axis-ports are located, i.e. on the sides or top/bottom? How does it affect the horizontal dispersion?

 

In other words, would it be a good idea to place the woofers top/bottom, so that the off-axis-ports disturbances are moved from the horizontal to the vertical plane?

 

Suggestion for an experiment:

 

Someone builds a 60x60 horn of reasonable full-range MEH size, mount a CD and woofers on two opposing sides and then measure polar response vertical, horizontal (and maybe even diagonally?) with and without off-axis-ports drilled (like Gnarly did). There are of course at least two options for the placement of the off-axis-ports, Danley-style and Gnarly-style. I´d prefer to see the results for Danley-stile off-axis-ports. That experiment could potentially be very educational if carefully designed.

 

Maybe there could be some group-funding per PayPal to pay for some sheets of plywood?

 

I am not in a position to execute that experiment.

 

Steffen

 

 

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On 5/4/2021 at 10:11 AM, Supersteff said:

I have been wondering for some time, weather it makes a difference, where the off-axis-ports are located, i.e. on the sides or top/bottom? How does it affect the horizontal dispersion?  In other words, would it be a good idea to place the woofers top/bottom, so that the off-axis-ports disturbances are moved from the horizontal to the vertical plane?

The off-axis ports apparently affect both axes of polar coverage by similar amounts...according to my measurements.

 

Chris

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OK, thank you.

 

Then the advantage of top/bottom woofers is mostly, that it is easier to build a "triangular" cabinet for the horn, making it fit the room-corner better and maybe picking the boundaries up better? Like the SH50 but 90x60.

 

 

Steffen

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5 hours ago, Supersteff said:

OK, thank you.

 

Then the advantage of top/bottom woofers is mostly, that it is easier to build a "triangular" cabinet for the horn, making it fit the room-corner better and maybe picking the boundaries up better? Like the SH50 but 90x60.

and why not go with 4 woofers while you are at it -

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and why not go with 4 woofers while you are at it -

You would have to stagger the woofers wouldn't you...which would throw off the position of the woofers behind the port, wouldn't it? I have also thought of this, but I do not know how staggering the woofers would effect the sound.

 

Sent from my SM-T830 using Tapatalk

 

 

 

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36 minutes ago, NBPK402 said:

You would have to stagger the woofers wouldn't you...which would throw off the position of the woofers behind the port, wouldn't it? I have also thought of this, but I do not know how staggering the woofers would effect the sound.

 

Sent from my SM-T830 using Tapatalk

 

 

 

-the SH96 uses 4 --15 inch woofers , in this  case , you could use much smaller woofers -

https://www.danleysoundlabs.com/wp-content/uploads/2020/04/SH-96-spec-sheet.pdf

 

450bcd29_vbattach207516.jpeg

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Well the SH96 has a square cabinet, that does not fit in the corner!

 

But the SH96 is an inspiration. I have been contemplating 4 woofers (16 ohms all in parallel) too, to be able to place the woofer centered over the off-axis ports.

 

Steffen

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here are the internals of the SH50-------triangular cabinet ----and the SH96  rectangular cabinet - -I guess a square cabinet is possible as well  ,  if the woofers are placed closer-

4881a9e6_post-50-1237717453.jpeg450bcd29_vbattach207516.jpeg

 

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On 5/3/2021 at 2:50 PM, Chris A said:

I was describing the changes in acoustic behavior as the frequencies decrease (i.e., the wavelengths are increasing) to where the distance from the throat to the beginning edge or lip of the off-axis ports is several wavelengths, then eventually it's at one wavelength (i.e., an acoustic impedance bounce--generally attenuating, and eventually the wavelengths correspond to a half wavelength to the horn throat (generally a resonance frequency), and then finally a quarter wavelength (where there is strong attenuation/ cancellation). 

 

At shorter wavelengths, the side walls behave more like canted outward mirrors as in optics.  At the one wavelength, half wavelength, and quarter wavelength points, the idea is that the horn volume behaves more like a resonant chamber and the volume geometries become important, not just the side wall area presented.  Remember that a horn is first and foremost an acoustic impedance transformer, then it can be viewed as a acoustic wave director--creating directivity in the emitted acoustic energy field.

 

At the first notch frequency of the woofers, you're seeing 1/4 wave volume resonance effects (very distantly reminiscent of a Helmholtz resonator).  But what the behavior actually changes to is a function of the exact geometry of the throat-end section of the horn bounded on the outboard side by the lip of the off-axis ports.  If those port edges or lips happen to be located at a pressure (or perhaps velocity) maximum for the resonant waves going by, then more disruption and attenuation occurs.  So the idea is that the pressure waves (or perhaps velocity waves) are maximal at the middle of the horn walls (but perhaps not, depending on wavelength).  For the geometries of the horn used, perhaps the local pressure or velocity max  regions shift toward the creases or internal edges of the horn.  So it isn't really clear what the dynamics of the acoustic waves are actually doing around the off-axis ports--it's probably complex. 

 

The first bet, however (i.e., Occam's Razor) is that the mid-walls are where the influence from the side walls is minimal, and therefore where you don't want to put a penetration through the horn wall.  That's the reason for avoiding placing the ports at the midpoint between the walls. 

 

However...

 

Chris

I'm happy to say i understood most of all of what you said. Thanks.

 

I've poured through the patents and many various Synergy/MEH forum discussions, and questions seem to come down to how well do the theory pieces match the results.

I don't doubt any of the the known physics in play, it's just how the pieces actually play together seems more complicated than describing how a MEH works piece by piece.

 

It's like the drivers see each other, as well as the horn, and their combinations of interplay form new "virtual" acoustic drivers and centers.

 

I've learned how important it is to short out the drivers not being measured. For instance, not shorting even the CD when measuring the mids, will put significant ripple in the mids' measurement.

 

The  mids i've used to reach to the CD have been either a pair of 8, 10, or 12" drivers. The ports centers, off-axis for the 12"s, and centered for the 8 and 10"s, have all been in the vicinity of 5" from the throat. I've tried to keep 1/4 WL notch at least above 600Hz.

 

Funny thing is, the time-of-flight (ToF delay) to acoustic centers of the mids, has always been greater than the ToF to the CD.

Funny because, even the mids'  voice  coils have less  physical distance to the mic, than the CD does. Mid ports have obvious less distance still than to the CD .    Dunno.....

 

A technique I've begun using to explore the interplays and timings, is using one driver as a microphone, and another as speaker.

And then measure via normal dual-channel or pulsing a wavelet (a recently learned method that has high timing precision on a frequency selected  basis.) 

Idea is to measure the time seen between the drivers and compare those "inter driver" flight times, to the difference in regular microphone at listening distance ToF's..

So for example, I've used the CD as a mic, and stimulate the mids.  Then reverse that.  Then do one mid as mic, one as speaker, .....etc... 

We'll see...could be a waste of time, but we'll see....

 

 

 

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22 hours ago, Supersteff said:

I have been wondering for some time, weather it makes a difference, where the off-axis-ports are located, i.e. on the sides or top/bottom? How does it affect the horizontal dispersion?

 

In other words, would it be a good idea to place the woofers top/bottom, so that the off-axis-ports disturbances are moved from the horizontal to the vertical plane?

 

Suggestion for an experiment:

 

Someone builds a 60x60 horn of reasonable full-range MEH size, mount a CD and woofers on two opposing sides and then measure polar response vertical, horizontal (and maybe even diagonally?) with and without off-axis-ports drilled (like Gnarly did). There are of course at least two options for the placement of the off-axis-ports, Danley-style and Gnarly-style. I´d prefer to see the results for Danley-stile off-axis-ports. That experiment could potentially be very educational if carefully designed.

 

Maybe there could be some group-funding per PayPal to pay for some sheets of plywood?

 

I am not in a position to execute that experiment.

 

Steffen

 

 

Hi Steffen, I'd offer to take up the project, but I learned along time ago that a good way to ruin a hobby is take any kind of money for it. 😅

 

With what you proposed, a 60x60....if it has ports in the corners as traditional, i think it's going to be very symmetrical and won't show much, if any, H vs V variation.

 

If the 60x60 used my center port design it might indeed have H vs Variation.  I've never tested center ports on anything other than  90x60 and 75x50 patterns, and to be honest haven't really cared about their Vertical polars.

 

A thing to be aware with the big mid drivers on top or bottom, is that the design requires H to V asymmetry to fit the drivers in between the side walls(like in pict i posted).. 

1.5:1 or higher works for 10" or smaller.  Don't know yet what 12"s would need....it would need to be very big, or have a higher aspect ratio.

 

You are correct about the design fitting in a corner better that side mounted and enclosed...in fact it will fit much better, especially for a 90 H pattern.

I've got a large room i keep toying with the idea of putting one in each corner up high.  If it weren't for the CD, the horn walls could go flush against the room walls!

 

But all that said, maybe the place for this discussion is in the newly formed less-than full range MEH thread ???

I think Chris would like to keep it focused on k-402 builds here...

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Hi Gnarly

 

Well I kind of thought  of you, when I wrote "somebody" 😄. It seems you are pretty skilled in building horns. I hope to become skilled to, but have some issues preventing me from starting up my synergy-projects.

 

Interesting to see what you come up with. I think it is important to think thoroughly about the design of the "experiment" to really know what you are looking for. As said, I´m most interested in Danley-style ports.

 

On the other hand, I have contemplated to build a horn your stile (one woofer top/bottom in between the walls), but with two smaller woofer-ports instead of one, i.e. like a compromise between Danley-style and Gnarly-style. That way the port would not be in the center and the ports would be smaller!? Dunno if that is a good idea?

 

1 hour ago, gnarly said:

Funny thing is, the time-of-flight (ToF delay) to acoustic centers of the mids, has always been greater than the ToF to the CD.

Funny because, even the mids'  voice  coils have less  physical distance to the mic, than the CD does. Mid ports have obvious less distance still than to the CD .    Dunno.....

 

Can this be caused by a phase-shift/delay caused by the acoustic low-pass-filter of the band-pass-enclosure that the woofers are playing through? I think Tom D hinted at something like that once.

 

A lot to learn! I really appreciate this learning environment/forum and the people contributing with knowledge and experience.

 

1 hour ago, gnarly said:

But all that said, maybe the place for this discussion is in the newly formed less-than full range MEH thread ???

I think Chris would like to keep it focused on k-402 builds here...

 

Well this thread has partly developed into some sort of learning/understanding thread for Big MEH´s, so I don´t know where else to put it? Most of the threads started by Chris tend to develop into educational threads going in all sorts of directions, answering all kind of questions in regard to MEH´s! Maybe start a new thread for "Experiments and explorations of the MEH-concept"?

 

I think we are quite some people following this thread, that do not have access to K402-horns for different reasons (me living in Denmark, Europe), but are inspired by the K402 for some kind of DIY-solution like yours.

 

Steffen

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4 hours ago, NBPK402 said:

You would have to stagger the woofers

 

 

4 hours ago, Supersteff said:

I have been contemplating 4 woofers (16 ohms all in parallel) too, to be able to place the woofer centered over the off-axis ports.

fantastic---you have the CAD drawings of the  MEH K402 - in a  rectangular cabinet  , could you simulate what size drivers could fit ? 

 

 

 

 

 

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2 hours ago, Supersteff said:

Hi Gnarly

 

Well I kind of thought  of you, when I wrote "somebody" 😄. It seems you are pretty skilled in building horns. I hope to become skilled to, but have some issues preventing me from starting up my synergy-projects.

 

Interesting to see what you come up with. I think it is important to think thoroughly about the design of the "experiment" to really know what you are looking for. As said, I´m most interested in Danley-style ports.

 

On the other hand, I have contemplated to build a horn your stile (one woofer top/bottom in between the walls), but with two smaller woofer-ports instead of one, i.e. like a compromise between Danley-style and Gnarly-style. That way the port would not be in the center and the ports would be smaller!? Dunno if that is a good idea?

 

 

Can this be caused by a phase-shift/delay caused by the acoustic low-pass-filter of the band-pass-enclosure that the woofers are playing through? I think Tom D hinted at something like that once.

 

A lot to learn! I really appreciate this learning environment/forum and the people contributing with knowledge and experience.

 

 

Well this thread has partly developed into some sort of learning/understanding thread for Big MEH´s, so I don´t know where else to put it? Most of the threads started by Chris tend to develop into educational threads going in all sorts of directions, answering all kind of questions in regard to MEH´s! Maybe start a new thread for "Experiments and explorations of the MEH-concept"?

 

I think we are quite some people following this thread, that do not have access to K402-horns for different reasons (me living in Denmark, Europe), but are inspired by the K402 for some kind of DIY-solution like yours.

 

Steffen

 

Hi Steffen, yeah I though you might be throwing me a hint haha. 😄

 

I tried putting ports more to the corners/side using the top and bottom style.  It didn't work very out compared to center.  I  also tried a centered frowny face arc, close to the throat, almost under the surround. 

Kept finding improved driver response when centered, withoutout significantly more polar damage .  But I'm sure there's more to be found out here still.

 

I don't see how the delay measurements can be caused by an acoustic phase shift, but  since i don't know what causes the delay anomalies, i can't rule acoustic phase shift out. 

I'm pretty dang certain it isn't electrical xover induced delay. I just ran some quickie measurements to illustrate.

 

First measurement is Syn7's processed 10" mid cones  a meter or so away from mouth..  The timing delay was 178.94ms,

which is the sum of processor latency and time-of-flight. (I did say I use alot of FIR Lol)646393869_midfortiming.thumb.JPG.ccb0f1f81bd46cef4493368925529016.JPG

 

The next measurement is the lower section of the BMS CD being used, the HF,  .  It had a delay of 177.29ms.

And is further away from the mic physically !

1542332628_HFfortiming.JPG.838f92dc65f7220ce9b5ae0eb25dc3fa.JPG

 

Please note the flat, linear-phase, phase traces for each. 

When phase is zero degrees flat like that, the delay needed to time the sections together is simply the difference in measured delays. 

Which in this case is 0.65ms.

 

 

So the last measurement is both sections MID & HF together, with a 0.65ms delay in place for the HF CD section (to match up to the MID's measured delay)

1448511203_midandHFfortiming0.75msdelayonHF.thumb.JPG.63249d75634987a7c0765e907806ad64.JPG

 

 

It's really as simple as that to establish delays when working with true linear phase.  A relative pure joy.

 

The 0.65 ms needed to add to the CD's HF section is what puzzles me...that's nearly 9 inches of delay.

Right now I'm inclined to think the CD's apparent acoustic center is moving out into the horn....but plain dunno...

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2 hours ago, RandyH000 said:
7 hours ago, Supersteff said:

I have been contemplating 4 woofers (16 ohms all in parallel) too, to be able to place the woofer centered over the off-axis ports.

fantastic---you have the CAD drawings of the  MEH K402 - in a  rectangular cabinet  , could you simulate what size drivers could fit ? 

 

Hi RandyH000

 

I think you mistake me for someone else, maybe StabMe, who has an other thread in this forum making a wooden K402-horn? I don´t have any drawings, unfortunately.

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