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


Chris A

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Thanks! I knew it was similar to a La Scala on it's side. That makes the horn itself only about 18-19 inches (minus the driver...) I have 9.5 foot ceilings in my larger room. Unfortunately it is about square at around 20-21 ft.

 

So you are getting down to 40Hz or lower with your configuration? Will be interesting to see some measurements after the weather warms up a bit. We're getting ready for temps in the low teens.

 

Bruce

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On 1/18/2016 at 11:30 AM, Marvel said:
So you are getting down to 40Hz or lower with your configuration?

 

Here is a frequency response and phase measurement in the center (non-corner) position, after crossing and EQ using a BMS 4592 dual-diaphragm driver:

 

10394696_K-402-MEH(onaxismid-wall)frequencyresponseandphasewithminphase.thumb.jpg.4297ca0b3ba6ef05f873d2bef0d225fe.jpg

 

Chris

Edited by Chris A
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Are you saying that a 20" deep conical-tractrix horn with two 15 inch woofers is able to perform equal to, or better than a 55" exponential horn path length Jubilee or K-horn bass bin?

 

 

I'm still sorting out, so much of the following are my listening impressions...not yet backed up by data. That data will be forthcoming, however, it's not a data-only decision, as you well know.

 

At frequencies above 175 Hz...yes, hands down. That's the real advantage of this configuration: matched polars, phase, and point source performance that the K-402 + Jubilee bass bin just doesn't have.  This is much more audible than I'd originally anticipated.  Enough difference alone that I'd consider this configuration on top of a Jubilee bass bin, but crossed lower around 200 Hz or perhaps even a bit lower.  It's just too good to not want what it brings to the table, IMO.  (I'm planning to gather polar data in this region to verify what my ears are hearing.)

 

Between 135-175 Hz, the New Center actually is still better (IMO) due to its point source performance, but the difference is much less than above. 

 

Below 135 Hz down to 60-70 Hz, the Jubilee bass bin in a corner performs better. When you consider the Jubilee bass bin size, corner-location requirements, and resulting HF horn height above the floor, that's a big pill to swallow, however, especially its added cost, (YMMV, obviously.)

 

Below 40-60 Hz, I'd rather cross to a horn-loaded sub for reasons of limiting IMD, but I'd be extremely happy with either bass bin, especially either in a corner, with the Jubilee bass bin performing with lower measured IMD and THD.  Both sound very tight and impactful, however.

 

Below 40 Hz, you still have capability (albeit using EQ) in the New Center that the Jubilee bass bin cannot fully follow due to its more limited woofer area: the New Center has double the woofer area alone, among other advantages, such as 6 dB-octave roll-off performance vs. 18-24 dB octave for the Jubilee bin in a corner below 32 Hz.

 

Overall, it's not a toss up. 

 

If you wanted to improve the New Center bass performance over what I'm currently using, that would be quite easy to do, either using reflex ports or baffles in a room corner, or both.  The Jubilee bass bin is pretty much optimized already with marginally better performance available if you use larger baffles to integrate its horn transition to the corner of the room.

 

...Not that I'm trying to get anyone upset... :ph34r:

 

Chris

Edited by Chris A
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Not upset at all, more like impressed. If not for my infatuation with the good looks of my Klipschorns, I might be buying parts for a K-402 full range system already.

 

In the meantime, am wondering why straight axis bass horns of the past needed to be so very much larger?

 

What is it about the Unity/Synergy style and your Klipsch K-402 based full range horn that defies past limitations? Is it the slight flare at the end of a short cone?

 

If one added this flare extension to the exit of a La Scala, K-horn or Jubilee, will it transform into a profoundly superior speaker?

 

Your project now has me thinking about loudspeakers more than I normally do.

 

post-58241-0-70900000-1453151799_thumb.j

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In the meantime, am wondering why straight axis bass horns of the past needed to be so very much larger? What is it about the Unity/Synergy style and your Klipsch K-402 based full range horn that defies past limitations? Is it the slight flare at the end of a short cone? If one added this flare extension to the exit of a La Scala, K-horn or Jubilee, will it transform into a profoundly superior speaker?

 

 

I don't wish to give anyone the impression that "new physics" is involved -- it isn't.  The issue has always been the so called "mid-bass problem".  PWK struggled with it in the Khorn design, changing the compression slot in its bass bin to be smaller in order to to improve its well known issue to reach 400 Hz.  One of the reasons why I believe that some people prefer the La Scala or perhaps Belle over the Khorns' bass bin (also perhaps using a subwoofer with the La Scalas/Belles) is that the Khorn performance over its decade of usable bandwidth (~32-400 Hz, nominally) is about at the limit that one can achieve with a bass horn--even folded. 

 

The Jubilee bass bin has the same issue, albeit with much better on-axis higher frequency performance than the Khorn bass bin (designed as the Khorn II toward the end of PWK's life with Roy D. assisting in the specifics of design and testing).  The result was the "Golden Jubilee" of the Khorn, renamed because its performance was that much better than the Khorn's bass bin that it deserved a new designation. 

 

The remaining issue with the Jubilee bass bin is its very narrow polars above 220 Hz due to its dual mouths interacting to form, in effect, an array of two emitters (horn mouths), which narrows its HF polar performance significantly, just like in the Khorn bass bin. (This also applies to the Belle at a higher frequency--about an octave, but not so much the La Scala) 

 

Also there has always been the issue of vertical separation of the horn mouths in the Khorn and in the Jubilee - more than 1/4 wavelength at the crossover frequency.  These vertical separations cause disturbances in horizontal and vertical coverage at the crossover frequencies (also between the tweeter and midrange, too), as well as the psychoacoustic effect of a non-point source loudspeaker over a point source one.  The effects of this single design detail was noted in the Altec 604 and later horn-loaded and reflex loudspeaker designs.

 

These really aren't revelations, only design trade-offs that may or may not be well known. All loudspeaker designs have design trade offs and strengths/weaknesses--that isn't really a revelation, either.

 

So the current horn design makes use of a different set of design trade offs than Khorns or even the Jubilee, recognizing the strengths of the K-402 horn design by Roy and the multi-entry horn design (i.e., Unity horn) of Danley.  So the subtleties of these two designs are put together into a new design that hopefully makes use of the strengths of those other designs and not their weaknesses. 

 

So the current design (New Center) makes use of the ideas of a point source design, multiple entry horn, and conical horn design below its Fc to yield a design with different performance and physical size characteristics that address the design weaknesses of the prior designs.  It also introduces it's own design weaknesses, of which I've identified a few in the above postings.  The idea is to produce a design that addresses customer needs/wants that aren't currently being addressed by the prior designs.

 

Some of those needs include things such as: better midbass performance in terms of polars, single point source loudspeaker (better imaging/presence), much smaller package, not having to use a room corners if they aren't available, lower cost, and perhaps a couple more customer needs/wants that haven't been addressed by the existing products (Klipsch and Danley, etc.).  The current New Center design has the potential to do that, IMO. 

 

So the current horn uses the real strength of the K-402's conical horn and tractrix horn properties, but simply extends that performance to its limit, using the same design trade that Danley uses with its full-range multiple entry horn designs.  Nothing really new by itself, but the combination IS new. 

 

Also note that the current design really doesn't make use of the Khorn, La Scala, Belle, or Cornwall designs because those designs don't have the design characteristics of the K-402 or the Danley Unity horn designs that are needed. Otherwise, it would look like a kit to update those designs.  That's really not the case in this instance.  It would be nice if it could.

 

So, in a nutshell, the current design combines the strength of the K-402 horn profile with the conical multiple-entry horn into a single aperture full-range horn loudspeaker design.   It recognizes some design trades that others might have missed.  Hopefully, the weaknesses of this design are minimized to create a significantly better design for a large customer segment whose needs aren't currently being addressed through current products: Jubilee or Danley Unity/Synergy designs.

 

Chris

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Note that you're not having to provide those mouth dimensions twice with the current design (i.e., the New Center) relative to the standard Jubilee design...or that you're having to deal with the effects of a severely undersized midrange horn mouth of the Khorn, thus dumping a lot of extra off-axis SPL into your room between 400-1700 Hz on your ceiling and floor, thus coloring the timbre emanating from the midrange itself unless further steps are taken to ensure plenty of absorption is present on the floor and ceiling (or the ceiling is 9 feet or higher in order to avoid early reflection issues). The current design doesn't require those measures to be taken to ensure a tonally balanced presentation.

 

Having two bass horn mouths side-by-side in both the Khorn and Jubilee bass bins also creates issues than having one horn mouth in the K-402, which is sized to hold its polars down to essentially the same frequencies as the Jubilee bass bin--in a frequency region below which the human hearing system can easily distinguish the size of the polars controlled by the horn itself or those controlled by the confines of the room (using quarter or eighth space loading).  That's another trick of the current design--just like the Khorn and Jubilee bass bins, except that you get a bit more latitude to place these loudspeakers along a wall instead of just in a corner.

 

Those are the reasons why the design in this case is so compact, relatively speaking. No magic involved--just better use of real estate.

 

Chris

Edited by Chris A
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I just ran WinISD on a ported box configuration.  If the box volume were about what the current box volume size is, and the ports were tuned for 40 Hz (four 2" ports about 15 inches long), there would be about a:

 

0 dB gain at 34 Hz

7 dB gain at 40 Hz,

3 dB at 50 Hz,

1 dB gain at 60 Hz.

 

post-26262-0-00980000-1453233668_thumb.g

 

This would add a rather large phase shift starting at 50 Hz (about 360 degrees), and group delay of well over 30 ms (i.e., not a very attractive approach). but I'm sure that harmonic distortion, modulation distortion, and required amplifier gain would be lower.

 

Perhaps there is a way to adjust the "Q" a bit, and control the phase shift, which is massive in the current example.

 

I still think that the current closed box configuration (acoustic suspension), using more amplifier power is a more "hi-fi" approach and the harmonic distortion levels would be lower than trying to use any direct radiating subwoofers, and cleaner than using TH subs, especially below 40 Hz, and still give significant sub-34 Hz performance. 

 

Perhaps a little more thinking on this subject is prudent before cutting holes and attaching ports.

 

Chris

Edited by Chris A
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I realize this is only one system so far, but how much power are you hitting this with? I realize I probably wouldn't be able to go low power SET on one of these, but it is still rather efficient, yes?

 

Bruce

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I haven't measured the bass channel yet.  You might be able to use something like a 300B SET on the bass bins in the current non-vented (closed box) configuration, perhaps even less.

 

I'm currently using a Crown D75A (45 w/channel) and there are no problems at all.  Note that the current configuration is using dual 15" woofers, and regardless of the venting or no venting, those are pretty efficient.

 

Chris

Edited by Chris A
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No problem.  These are good questions. 

 

Your 2A3 is probably enough for the bass channel, considering that you're not driving a passive crossover with lots of reactance.

 

Chris

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  • Klipsch Employees

 

Are you saying that a 20" deep conical-tractrix horn with two 15 inch woofers is able to perform equal to, or better than a 55" exponential horn path length Jubilee or K-horn bass bin?

 

 

I'm still sorting out, so much of the following are my listening impressions...not yet backed up by data. That data will be forthcoming, however, it's not a data-only decision, as you well know.

 

At frequencies above 175 Hz...yes, hands down. That's the real advantage of this configuration: matched polars, phase, and point source performance that the K-402 + Jubilee bass bin just doesn't have.  This is much more audible than I'd originally anticipated.  Enough difference alone that I'd consider this configuration on top of a Jubilee bass bin, but crossed lower around 200 Hz or perhaps even a bit lower.  It's just too good to not want what it brings to the table, IMO.  (I'm planning to gather polar data in this region to verify what my ears are hearing.)

 

Between 135-175 Hz, the New Center actually is still better (IMO) due to its point source performance, but the difference is much less than above. 

 

Below 135 Hz down to 60-70 Hz, the Jubilee bass bin in a corner performs better. When you consider the Jubilee bass bin size, corner-location requirements, and resulting HF horn height above the floor, that's a big pill to swallow, however, especially its added cost, (YMMV, obviously.)

 

Below 40-60 Hz, I'd rather cross to a horn-loaded sub for reasons of limiting IMD, but I'd be extremely happy with either bass bin, especially either in a corner, with the Jubilee bass bin performing with lower measured IMD and THD.  Both sound very tight and impactful, however.

 

Below 40 Hz, you still have capability (albeit using EQ) in the New Center that the Jubilee bass bin cannot fully follow due to its more limited woofer area: the New Center has double the woofer area alone, among other advantages, such as 6 dB-octave roll-off performance vs. 18-24 dB octave for the Jubilee bin in a corner below 32 Hz.

 

Overall, it's not a toss up. 

 

If you wanted to improve the New Center bass performance over what I'm currently using, that would be quite easy to do, either using reflex ports or baffles in a room corner, or both.  The Jubilee bass bin is pretty much optimized already with marginally better performance available if you use larger baffles to integrate its horn transition to the corner of the room.

 

...Not that I'm trying to get anyone upset... :ph34r:

 

Chris

 

so there is nothing that is being compromised?  nothing that is being minimized?  and dont worry....i am not upset.  lol!  

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