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Chris A

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

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5 hours ago, Supersteff said:

I´m worried to have the off-axis-ports located over the surround of the woofers, as can be seen on several Danley Synergy-speakers. It might not be an issue in PA, but is it an issue in HiFi? Is it a source of distortion, that can be eliminated? Mark100 writes, that he made experiments with the location of the ports relative to the woofers, stating that it sounded best when the ports where located centrally over the dust-cab of the woofer!? 

I had that worry several years ago--that the woofer cone would be excited into a rocking mode instead of a straight pistonic mode. 

 

Then I thought about what effects would be going out the ports.  It turns out that most of what occurs behind the ports in an MEH stays there and is not passed through the horn (harmonic and modulation distortion aside). In other words, the higher order modes that may be excited behind the horn's woofer port are not passed through the port (unless you're at something like 2-4 kHz).  So that issue isn't real. 

 

If you want to help yourself feel better about the situation, you could design and insert a "frustum of a cone" (inverse shape of the woofer cone) to take out the added volume of the air between the horn's rear surface and the cone to reduce the compressed volume of air.  It won't be audible in the frequency bands below about 1-2 kHz, but you'll feel better. :smile:

 

5 hours ago, Supersteff said:

So when the off-axis-ports move apart from each other, say 10-12" , as they move away from the throat (as you have mentioned in your other thread on the AXI2050 in a K402) it could make sense to replace one 15" woofer with two 12" woofers side by side!?

From the first discussion that I present in this post, you might see that the real issue is port-to-port interactions on the front side of the horn, not the driver-to-port interactions on the rear side.  It's actually pretty cool that the higher order dynamics (HOMs) don't propagate through the ports. It's really an application of the Huygens-Fresnel principle, and it is another reason why horn loading is actually a superior way to design loudspeakers (given that the problems of horn geometry, etc. are worked out properly).

 

Chris

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18 hours ago, Chris A said:

I had that worry several years ago--that the woofer cone would be excited into a rocking mode instead of a straight pistonic mode.

Well that was actually my worry too. It seems you have debunked that issue too 🙂 .

 

18 hours ago, Chris A said:

If you want to help yourself feel better about the situation, you could design and insert a "frustum of a cone" (inverse shape of the woofer cone) to take out the added volume of the air between the horn's rear surface and the cone to reduce the compressed volume of air.  It won't be audible in the frequency bands below about 1-2 kHz, but you'll feel better. :smile:

Hmm, it won´t make me feel better to do unnecessary things! And it could even be counterproductive in regard to attenuating woofer-sideband effekts! I would imagine, that the volume of compressed air should be just right to support output up to the notch-frequency!? 

 

I think a lot of my confusions and imagined problems stem from years of reading about issues on off-axis-ports on DiyAudio. Maybe those concerns are relevant to midrange-off-axis-ports, but not to woofer-off-axis-ports! It is very instructional for me to discuss these tings here, and sort out what really matters! You have stated it before: It is not that difficult to build a MEH!

 

Regards

 

Steffen

 

 

 

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On 4/1/2021 at 12:46 PM, Supersteff said:

Maybe those concerns are relevant to midrange-off-axis-ports, but not to woofer-off-axis-ports...

 

Yes. 

 

But in the MEH world, all midrange drivers that aren't part of a coaxial single compression driver (i.e., BMS, B&C, etc. dual diaphragm compression drivers), the term "midrange", if applied to a separate driver than the apex-mounted tweeter driver, will have a maximum crossover frequency of less than 2 kHz because of the physical inability to bring the tweeter and midrange drivers to within 1/4 wavelength at the crossover frequency.  This is a pretty important observation that most people miss.

_____________________________________________________________________

 

This same issue is true for non-MEH designs.  If you are crossing over between a midrange driver and a tweeter, and that frequency is above 2 kHz, there's no way you're going to avoid polar lobing and directivity issues, because the two drivers' horn centerlines are more than 1/4 wavelength apart at the crossover frequency band. 

 

This is why dual diaphragm drivers are such a big deal, and why everyone that thinks that three-way loudspeakers are better than two-ways (they aren't, but that's a moot point nowadays in that everyone can buy dual diaphragm compression drivers to replace their separate tweeter and midrange horn/driver combinations) will find that two ways are in fact better designs because of the resulting polar lobing issues with separate horns/drivers of three-way designs.

 

Another observation: a lot of people think that 1" compression drivers are less expensive than 1.4", 1.5" or 2" throat compression drivers (again, non-MEH designs).  This is actually false economy (IMHE) because by the time you integrate that higher quality 1" compression driver into a loudspeaker with a midrange and bass bin and have dealt with the resulting polar lobing issues because of the limited bandwidth of the "full range" 1 inch throat drivers, the costs have risen beyond the cost differential of using a good 1.4-->2" dual-diaphragm compression driver and associated horn to avoid adding that third "way" to the loudspeaker.

 

So in my experience, 1" compression drivers are not worth the trouble because the loss of fidelity in trying to go that way isn't worth the perceived avoidance of cost.  One inch compression drivers are more trouble than they're worth.

 

Chris

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Posted (edited)

I have been thinking a bit about this comment of yours:

 

 

On 3/31/2021 at 3:33 PM, Chris A said:

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.

 

 

I have chosen to delete some of which I hade written here before, to prevent any misunderstandings or controversy. I hope the remaining writings still make sense.

 

 

Maybe you were referring to all those "small" synergy´s on diyaudio? 

 

As I see it, the big-synergy-horn-approach is the best technology to reduce the negative effects off the room on the sound. And in many ways I see your MEH-approach as going to the extremes/limits of the technology! You aim to fully utilize boundery-effekts and directivity down to under the Schroeder-frequency, and that makes perfect sense to me. But it seems that the size needed for that is not often accepted by most people! I think you have also stated before, that people don´t know what they miss!! But it is the only logical approach in my view.

 

Any way, I try to view the various constructions in their context, take what ever I can learn from them and leave the rest. I´m not in this to safe money, but to avoid common compromises.

 

 

I am still not finished with all my house-projects, one of them being clearing a basement-room to become my synergy-workshop! So for the moment I have to do as good old Albert Einstein: Stick to thought-experiments! 😉

 

I have been looking at the SH96 that you posted pictures of, and wondered what the difference in horizontal dispersion would be, if the woofers are mounted on the Horizontal horn-walls (like in the SH96, but without reflex-ports!). Would the artifacts of the off-axis-ports move from the horizontal to the vertical plane (ceiling and floor), and make for a more clean horizontal dispersion? I guess one way to find out would be, to build a 60x60 synergy (without reflex-ports) and measure horizontal and vertical coverage?

 

That was todays question to the professor 🙂 

 

Steffen

 

 

 

Edited by Supersteff
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This probably isn't the appropriate place to discuss my assessments of individuals that post on audio forums frequently, and certainly not for those on another forum.  Please PM me for any questions that you might have.  Nothing that I said above has changed since your last post.

______________________________________________________________

 

2 hours ago, Supersteff said:

And in many ways I see your MEH-approach as going to the extremes/limits of the technology!

I don't know if that's a compliment or critique.  I think it's important that everyone feels free to express their (informed) feelings on the designs presented here, but note that this is a "two-handed game", and I don't always know what you are actually thinking about the subject(s) at hand.

 

I'm an engineer and I don't like to use yesterday's technology and designs when I've found something better. (I think I'm not alone, especially in the engineering world.)  Nostalgia is something I leave to others...but good engineering observations are something that I consider to be timeless, and therefore of the utmost importance for me to understand and incorporate into my designs.

 

2 hours ago, Supersteff said:

Anyway, I try to view the various constructions in their context, take what ever I can learn from them, and leave the rest. I´m not in this to save money, but to avoid common compromises.

 

I'm no different.  Note however that good engineering is not really a (soft) liberal arts subject.  Truth is truth--like laws of physics (i.e., psychoacoustics is really not a subject of opinion and taste, but rather based on immutable truths).  Please don't confuse engineering based on those kind of truths with "flavor of the month" approaches to loudspeaker design.  There are tradeoffs everywhere, but the truths underlying the tradeoffs are not really subject to opinion--only realization. 

 

PWK was a master of talking about those truths, I believe, and did not yield to "design by committee" approaches to loudspeaker design.  That's my approach, too. I value what other good loudspeaker design engineers said highly, and only choose to go other directions from their observations only after I've done fairly careful "due diligence". 

 

I think relativism in loudspeaker design is actually a plague--that I believe is transmitted more frequently as others try to "harmonize design approaches" into a "flavor of the month".  I think it's much wiser to follow basic truths, and to be careful about changing one's opinions, so that they are based on first-hand experiences and testing.  PWK was one such individual, Tom Danley is apparently another. Others on diyAudio--not so much in my experience.

 

2 hours ago, Supersteff said:

So for the moment I have to do as good old Albert Einstein: Stick to thought experiments! 😉

 

I did that very same thing for several years before creating the K-402-MEH (and other designs not yet disclosed here).  I find that thinking more before cutting material and buying drivers works much better...at least for me.  Others I think get trapped by little rabbit trails of "doing" rather than thinking about it first--carefully--and fail to reach really useful results.

 

2 hours ago, Supersteff said:

I have been looking at the SH96 that you posted pictures of, and wondered what the difference in horizontal dispersion would be, if the woofers are mounted on the Horizontal horn-walls (like in the SH96, but without reflex-ports!).

That's a tradeoff that can be assessed or bounded via thought experiment.  How much of the horn side wall area is compromised by the woofer ports (as a percentage)?  How does that translate to dB loss off-axis at the crossover frequency band?  And remember that the human hearing system and the way humans listen to loudspeakers makes the horizontal coverage consistency much more important than vertical coverage consistency (i.e., you can compromise more in the vertical direction, I find).  It's simply a tradeoff if the size and shape of the box becomes more important than the acoustics of the loudspeaker.

 

2 hours ago, Supersteff said:

That was today's question to the professor 🙂 

My graduate students from time to time had a habit of calling me by that name.  I told them that my name is Chris (or much more formally--Mr. Askew--if the age differential was too great for them to accept comfortably).  It keeps social distance to a minimum, I find it facilitates the learning process.

 

Chris

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12 hours ago, Chris A said:

I'm no different.  Note however that good engineering is not really a liberal arts subject.  Truth is truth--like laws of physics (i.e., psychoacoustics is really not a subject of opinion and taste, but rather based on immutable truths).  Please don't confuse engineering based on those kind of truths with "flavor of the month" approaches to loudspeaker design.  There are tradeoffs everywhere, but the truths underlying the tradeoffs are not really subject to opinion--only realization. 

 

PWK was a master of talking about those truths, I believe, and did not yield to "design by committee" approaches to loudspeaker design.  That's my approach, too. I value what other good loudspeaker design engineers said highly, and only choose to go other directions from their observations only after I've done fairly careful "due diligence". 

 

I think relativism in loudspeaker design is actually a plague--that I believe is transmitted more frequently as others try to "harmonize design approaches" into a "flavor of the month".  I think it's much wiser to follow basic truths, and to be careful about changing one's opinions, so that they are based on first-hand experiences and testing.  PWK was one such individual, Tom Danley is apparently another. Others on diyAudio--not so much in my experience.

I agree wholeheartedly with these comments, especially about PWK and, especially, Tom Danley, who wins the prize for being such a PROLIFIC speaker designer, top to bottom, for the last 30 years.

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Hi Chris

 

54 minutes ago, Chris A said:
3 hours ago, Supersteff said:

And in many ways I see your MEH-approach as going to the extremes/limits of the technology!

I don't know if that's a compliment or critique.  I think it's important that everyone feels free to express their (informed) feelings on the designs presented here, but note that this is a "two-handed game", and I don't always know what you are actually thinking about the subject(s) at hand.

It was certainly meant as a compliment! I do agree with you on the necessity of big size of a horn, you do what is needed by physics. Form follows function.

 

Steffen

 

 

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11 hours ago, ClaudeJ1 said:

I agree wholeheartedly with these comments, especially about PWK and, especially, Tom Danley, who wins the prize for being such a PROLIFIC speaker designer, top to bottom, for the last 30 years.

Of course we should not ignore all the great contributions to the Art and Science by Roy Delgado.

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Possible inexpensive amp for K402s... $250.



Sent from my SM-T830 using Tapatalk

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First post and not even Klipsch related, but I think reasonably on-topic in this thread: Since over here in Europe K402 are special order through pro install dealers and prohibitively expensive, has anyone here thought about MEH-ing a SEOS-30 or even done so? That's the biggest easily obtainable ready-made horn suited for the job and relatively cheap. The flat conical surfaces should make it easy to work with regarding woofer mounting / porting too.

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On 4/28/2021 at 4:00 AM, Vathek said:

First post and not even Klipsch related, but I think reasonably on-topic in this thread: Since over here in Europe K402 are special order through pro install dealers and prohibitively expensive, has anyone here thought about MEH-ing a SEOS-30 or even done so? That's the biggest easily obtainable ready-made horn suited for the job and relatively cheap. The flat conical surfaces should make it easy to work with regarding woofer mounting / porting too.

 

Looking at a picture of the SEOS-30, I would guess that it could work for you. Let us know if you make it happen.

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On 4/28/2021 at 6:00 AM, Vathek said:

First post and not even Klipsch related, but I think reasonably on-topic in this thread: Since over here in Europe K402 are special order through pro install dealers and prohibitively expensive, has anyone here thought about MEH-ing a SEOS-30 or even done so? That's the biggest easily obtainable ready-made horn suited for the job and relatively cheap. The flat conical surfaces should make it easy to work with regarding woofer mounting / porting too.

You might also try this question over at the DIYaudio forum. There is an active group over there interested in multiple entry horns. Many (but not all of them) of the guys are quite knowledgeable.  

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11 hours ago, Khornukopia said:

 

Looking at a picture of the SEOS-30, I would guess that it could work for you. Let us know if you make it happen.

Is SEOS available in US, or still in business? I had no luck trying to purchase a large Seos horn.

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2 hours ago, VDS said:

Is SEOS available in US, or still in business? I had no luck trying to purchase a large Seos horn.

 

I examined an illustration of that horn on a website to answer Vathek's question. It appeared that those are available by special order (driver mounting flange type) in Europe. 

 

The K-402 is better.

 

 

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On 4/28/2021 at 5:00 AM, Vathek said:

has anyone here thought about MEH-ing a SEOS-30 or even done so?

I think you'll wind up with a loudspeaker that requires a separate woofer--like virtually all the other "hybrid MEHs" that you'll see over at diyAudio.  Only if you place the SEOS30 horns fully in room corners will you have a chance of avoiding a separate direct-radiating bass. 

 

Here is a quote from another thread on the Celestion Axi2050 2" compression driver on a K-402 horn that should be carefully considered:

 

On 3/5/2021 at 7:15 PM, Chris A said:

I have seen no other horns that can fully take advantage of this driver's [i.e., a Celestion Axi2050] very broad-band performance than the K-402 horn.  Even the largest SEOS 30 horn isn't big enough to take advantage of the extended low end of this new Celestion Axi2050 driver.

 

What this is saying is that, if using the Celestion Axi2050, you can cross over to the bass bin at 200 Hz--one driver, one horn from 200 Hz to 20 kHz.  And the sound is very, very smooth and precise all the way through that passband.

 

If you instead use a SEOS-30 with the Axi2050, you're going to need something to close the SPL gap between 400 Hz and 200 HZ.  If the loudspeaker is in a full room corner--like corner horns--you can probably span that gap.  But the moment that you take the loudspeakers out of eighth space (corner) loading, you've got a SPL response issue. 

 

The problem is just physics:  the horn mouth needs to be about 35-40 inches wide to control its polars down to 200 Hz--where boundary gain takes over and controls the in-room directivity below the room's transition (Schroeder) frequency.  The SEOS-30 loses its horizontal directivity at ~340 Hz.  That's just a little too high for how most people choose to use their loudspeakers (i.e., NOT in full room corners). 

 

The other problem that I've had is that Auto-Tech doesn't seem to respond to requests for quotation for anything.  It could be that they're simply ignoring requests from those living in the North America, but I suspect that they are not really selling the SEOS-30 presently--unless you're buying a lot of them in one large order.

 

Bottom line: look for a straight-sided horn with dual-flare that is at least 35-40 inches across the mouth is the major axis direction.  It you're going to do a "full range MEH", that's a requirement--unless you're going to make them obligate corner horns. 

 

I recommend doing it in plywood using Bill Waslo's Synergy Calc spreadsheet.  It's a lot less expensive for material costs, and you get to control the exact dimensions (over 35 inches mouth dimension) for the horn.

 

Chris

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Thanks everyone. The reason I’m looking at the SEOS-30 is mostly build simplicity. I’m in a big city with no back yard, garage or anything like that to use for wood work. So for something based on Bill’s spreadsheet I would have to hire a carpenter and then things get expensive quickly. Whereas a rectangular CLD box can be built at home with pre-cut wood from one of the various home depot like stores here. What intrigued me about the K-402 MEH in this thread was the omission of the midrange cone drivers by using a large compression driver, which makes it so much easier for this ready make approach. Most threads / projects go the 1-inch plus 4-inch cone midrange route, this is why I posted here.

 

I’m fully aware a SEOS-30 will not control directivity down to Schroeder frequency unless I put it in my shower, but if that was a sine qua non criterium there would only be a handful of speakers in the world in the first place. It’s a compromise I would be willing to live with. Since autotech don’t put their prices on the website, I’m not going to make them public here, but you could easily get a surround system for the price of a single K-402 and they’re extremely well built from about 10mm thick fibreglass (which might be just about perfect for the woofer taps). And in Europe they’re readily available, I’ve bought several of their smaller waveguides from them. I realise that the situation might be pretty much the opposite in the US.

 

Also I would aim for a x-over point around 400 or 450 Hz or so, which allows for more (and cheaper) options than the Axi2050. I’m not trying to make the argument that any of this is better than the Axi2050 on a K-402 (not at all!), but three pieces (LCR) of that combo would set one back around 10k over here, and that’s just for the horn and the compression driver. Whereas a couple of 12-inch woofers and a BMS 4590 on a SEOS-30 would cost somewhere around a grand per channel. And the 400 - 450Hz crossover has been proven to work in many MEH’s with the 1-inch plus (one or several) 4-inch midranges.

 

If I had (access to) a proper wood work shop, I would absolutely pursue the plywood version based on Bill’s spreadsheet. The whole idea behind this is to find a solution that is as ready made as possible and here the SEOS-30 seems to be the second best option after the K-402 at a much lower price point and at least in EU it’s easily available. The BMS 4590 is more expensive than a 1-inch and a couple of 4-inchers, but it’s “bolt on and done”. The key to the whole thing is the choice of woofers and the location, shape and size of the woofer taps and maybe some sort of ‘mounting construction’ for the woofers. And that’s really what my question was aimed at. I realise that was way too implicit in my initial post. And if nobody has done this with a SEOS-30, I guess I’ll have tackle it myself. But I haven’t even been able to wrap my head around Hornresp, so this might prove to be a challenge.

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Didn’t want to start a new thread, so I’m going slightly off topic. Anybody have any amp matching advice with a K402 MEH? Thinking Crown, class D xls 1502 or class AB k1.

probably my class A Pass xa25 for mids. 
Any problem sonically, or otherwise, mixing A and D in K402 MEH horn? Or just go K1?

any other amp advice? Thanks

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5 hours ago, Vathek said:

So for something based on Bill’s spreadsheet I would have to hire a carpenter and then things get expensive quickly.

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.

 

Chris

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1 hour ago, VDS said:

Anybody have any amp matching advice with a K402 MEH?

You can do what you like for the woofer channels--they aren't critical.  The compression driver channel--probably a good class A or AB amplifier is what I'd recommend.  Others may have their own opinions that includes class D.  I had a poor experience with Hypex, so I'd avoid class D.

 

Chris

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1 hour ago, VDS said:

Didn’t want to start a new thread, so I’m going slightly off topic. Anybody have any amp matching advice with a K402 MEH? Thinking Crown, class D xls 1502 or class AB k1.

probably my class A Pass xa25 for mids. 
Any problem sonically, or otherwise, mixing A and D in K402 MEH horn? Or just go K1?

any other amp advice? Thanks

VDS - I've been considering the same question for my upcoming K402 MEH build, thanks for asking.  Nelson Pass (I believe in an interview on youtube, maybe the San Francisco audiophile society interview?), cautions against mixing amp topologies with different distortion characteristics (it can lead to unpredictable results per Nelson).  I believe class D distorts at higher frequencies, but is not as much an issue for lower frequencies as Chris mentioned.  I'm picking up a firstwatt F6 clone to drive the Celestion Axi2050's, and am still kicking around choice of woofers and amps to drive them.  Let us know what you end up with.

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