Horn Gurus: Implications of modifying the exit angle of Khorns?

[formica]

I was wondering the implications of modifying the exit angle of Khorns while keeping the same mouth area. I posted this as part of an existing thread in 2 channel... but got no "technical" responses.

Basically this came up in a discussion about angling the high frequency drivers in a khorn to allow a seating area which would be further back than the typical ½ x the front room width. What I proposed is if someone had the room behind the Khorns to rotate the whole wall rather than just the top unit... this would be a more elegant solution.

Option (1) would be what you would typically expect... while Option (2) would allow a seating position which is further back, in a relatively narrow room.

This would result in a narrowed exit path at point (A) but a wider one at point (. The mouth size would technically remain the same... so I was wondering what effects, if any, this would have on the frequency response?

I was hoping some of the "horn gurus" would give some input...

Thanks...

Rob

[TBrennan]

I can't see why it would have any bad effects on the basshorn response. Looks like a good idea, given that one could actually implement it.

[colterphoto1]

look at the dispersion of the mid horns, does this arrangement create more early reflections from the side walls?

Michael

[JJkizak]

Might try just rotating the top section of the K-horn if possible as a test without doing a 50K remodeling job relocating walls and ceilings. Bass is fairly non directional. Only four screws fasten the sections together and there are small rubber pads between them so they can just sit there for a test.

JJK

[Klewless]

When I had my home made Khorns, I did a similar thing. Rather than having the corner project outside the room as you show, I put sides on the back of the Khorn bass and rotated it within the corner, achieving the same effect.

It sounded as good as my authentic Khorns of today which do not have the bass horn modified in any way. I have plans to put side boards on my existing Khorns some day.

Another alternative is to construct a "corner house" to put the Khorns into that you can integrate into the room (and rotate) without extending backwards beyond the front wall. If one were to shorten the room the "corner house" could be implemented with a wall between them across the room providing other possibilities, such as equipment cabinets, recessed TV, etc.

In summary I liked my Khorns toed in a bit and do not feel anything was lost. Of course I do not have proper test equipment to verify what I did acoustically. But my ears were happy.

[D-MAN]

Why not just turn the top cabinet, the bass horn doesn't care what angle it's at, but the mid and tweeter certainly does. That angle is the important one for listening position.

DM

[Deang]

Why not just turn the top cabinet

Because it looks like crap, and as everyone knows -- it's better to look good than to sound good.

[D-MAN]

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On 2/22/2005 12:41:54 PM DeanG wrote:

Why not just turn the top cabinet

Because it looks like crap, and as everyone knows -- it's better to look good than to sound good.

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YES, indeed it does.

but it will PROVE what I am saying as an experiment. The next step is to make a top cab that DOESN'T LOOK LIKE CRAP when the horns are positioned as needed...

{EDIT} It should be noted that the K400/401 is designed to require baffle mounting (if I remember correctly, but I could be wrong). Even so, a "turret-mounted" baffle assembly could be constructed to allow for the whole thing to be positioned inside of an aesthetic cabinet top, IMO.

The most important consideration would be the overall length of the midrange horn, which is very long, and may prevent much "adjustment". Experimentation would be required to determine whether this approach can be taken. So this particular mod might prove to be an all-or-nothing type of change.

{edit#2}It would, however, be more cost effective to swap out all the upper horns and cabinets than changing the room itself to accomodate stock Khorns.

DM

[D-MAN]

I've found that the best position for the upper horns to point to is actually "outside" of the listening position, rather than directly on-axis.

{edit} The soundstage actually would be a straight line between the front of the speakers rather than an oval shape towards the listening position, I just couldn't draw exactly what I wanted to, but I figure that this gets the point across. I don't like for things to "stick out" much in front of the listening position, although the horns can be arranged to provide that effect, if desired.

DM

[formica]

I'm looking into different layout possibilities for a projected music/HT room, but I often find that the listening distance is a limiting factor. By having a way of modifying it, it allows for many more placement options.

I may or may not use it, but it's good to have the option.

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On 2/22/2005 8:39:20 AM Klewless wrote:

If one were to shorten the room the "corner house" could be implemented with a wall between them across the room providing other possibilities, such as equipment cabinets, recessed TV, etc.

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Although I didn't mention it... that is the idea. The surrounding rooms would remain rectangular, and the space could be borrowed from the room itself. (ie: the front wall would move into the room a bit). This would allow for a recessed RPTV and centre channel... but a front projector wouldn't benefit as much. Given the plasterwork has to be done anyways, its basically integrated "false" corners.

Rotating the Klipsch top horns does allow for a little fine-tuning, but seems to be more work with less flexibility (limited rotation).

Make the room wider is the correct answer, but we all know that isn't always easy nor adapted to HT viewing.

later...

Rob

[Colin]

good drawing Dman! what is the effect of putting a backwall on the Khorn bin and then turning the unit to the rear, so you are adding another fold to the horn (but keep the top unit in the corner facing the listener)?

[D-MAN]

Rob, I have exactly the same problem. Limited as to how far back I can put the listening position.

I specifically wanted to avoid changing the room to deal with the speakers, and went for changing the speakers to deal with the room. Did not want to create a "white elephant" out of the house because I want to sell it someday with as little problems as possible.

Colin: it would take up more room, and unfortunately not go any lower, as the horn fc determined by the expansion rate does not change, it's just longer and ends in a bigger mouth, but not quite large enough to allow free-standing use. I imagine that it could be approaching satisfactory floor+single wall use, although its shape would still be somewhat awkward.

DM

[artto]

Rob, the implications are that the minimum recommended unobstructed distance on the side walls is 4 from the front of the Khorn which is approximately 79 from the corner. To see this more objectively, draw a line on the floor, parallel to the front of the Khorn, 28 out in front of it, from wall to wall. This is technically where the Khorn ends. Beyond this distance very little, if any, additional acoustic loading or reinforcement is obtained from room boundaries. Think of it as if the walls and floor are truly extensions, the final fold, of the folded horn. And since the rate of flare and horn length is a major determining factor of the low frequency cut-off, by changing the horn boundary angles in the last fold, you are essentially changing the rate of flare of the bass horns last fold. And also by not doing it symmetrically (one side of the horn is now expanding more, while the other side is decreased), you are essentially defeating the whole purpose of what a Klipschorn is all about, and that is to get true 1/8 space reinforcement of a trihedral room corner to effectively make the speaker much larger than what it really is (8x larger), so it can reach down that extra ½ to full octave (depending on your specific rooms acoustical properties), sort of a free lunch so to speak. Since this is an exponential horn, its size must increase exponentially to obtain a substantially lower cutoff frequency, therefore becoming extremely large and not practical for almost any domestic situation. In my own room I got around this to some extent by using the rooms modal properties and fundamental resonance frequency (19Hz) to reinforce the lowest frequencies.

The other implication is that mentioned by colter. Lets not forget that PWK designed the mid horn for controlled directivity, to radiate most of the horns acoustic energy into the room evenly from a 45 degree angle to obtain the widest room coverage at maximum efficiency (lowest distortion). Therefore turning the corner placed mid horns at a steeper angle will certainly produce more early reflections which will negatively affect imaging and resolution. Over the past 20+ years of experimentation with these speakers I've found that they don't like a lot of absorptive materials around the mid/treble horns (to reduce early reflections) which why I employed the polycylindral surfaces so the area around them could be kept "live", but diffused instead of dead and absorptive.

Rotating the top as JJK suggested is an alternative, provided you keep the bottoms in a proper corner, and do something to get the side wall reflections away from the mid/treble horns, while keeping proper boundaries on the top of the bass horn (which as we know, the top unit normally provides).

The suggestion D-Man made regarding the best position for the upper horns to point to is actually outside of the listening position, rather than directly on-axis is something that is entirely dependent on obviously less than ideal conditions as a means to try and compensate for it. Ive been through this before myself. There was a time I liked to sit beyond the axis. There was a time I preferred to listen as D-Man suggested. But these were all situations that are probably more typical for most people and were done to compensate for less than ideal circumstances.

There is no substitute for doing it right. And I will go out on a limb once again and say that you aint heard nothin yet, until you at least begin to approach it this way. All these exercises trying to adapt the Khorn to this or to that are like trying to put a 426 Hemi on a bicycle so you can get to the store faster. If you dont have the proper conditions to take advantage of it (like a drag strip from your house to where ever youre going) the point is moot. If one simply likes going through the exercise of doing it, because they enjoy it, then great. But dont expect it to necessarily accomplish what you had hoped for. Of course, thats one of the reasons Klipsch began to make other speakers, which were intended to be more appropriate for a wider range of conditions, as well as less expensive.

[sunnysal]

good posts! artto, methinks, has it about right...move the headsection out to see how it sounds but keep the bass cabs in the corners..regards, tony

[JJkizak]

Wow! Two 426 aluminum hemi's, one in each corner, would that blow somebody's mind or what?

JJK

[formica]

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On 2/22/2005 6:23:42 PM artto wrote:

There is no substitute for doing it right. And I will go out on a limb once again and say that you aint heard nothin yet, until you at least begin to approach it this way.

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Right now I'm tring to establish what the different options are and their implications, but I will, no doubt, have some more questions for you on optimizing the projected room once I figure out what I want. This will be a basement renovation in an early 1950's home... so it has many limitations you don't get building new. I definitely do agree with you that avoiding compromises entirely, would produce the best result.

Subject for another thread would be what constitutes a "reasonable" compromise... false corners, LaScalas, Cornwalls, etc? This will obviously vary from person to person, but I was impressed with the Khorn's performance in a very compromised temporarily setup in my living room next to where my Cornwalls normally sit. I honesty didn't expect them to outperform the Cornwalls... but yet they did on many levels. These weren't purchased to be used there, but who could let them sit on a palette while designing and building a room? Until then, I had preferred the Cornwall's more balanced sound compared to the LaScala/Belle.

As for the possible integrated "false" walls, I figured the modified exit angles would change the resistance presented to the two horn paths, increasing it on one side while decreasing it on the other. Technically speaking though, the flare rate would remain the same for the overall horn as well as it's overall resistance. The 1/8 space should also still be valid? Although I have a general idea of the physics involved in a horn, I don't I have a deep enough knowledge to predict the outcome. I do understand that asymmetry is more critical in higher frequency horns (and hence the large variety of adapted flare rates, etc...) ... but PWK included some compromises within his own designs of the bass horns, finding that they had a relatively small effect. Both the LaScala and the Belle have some which are simple to see, but I haven't verified the Khorn drawings.

I do see the increased mid/high horn reflections mentioned by colter, as possibly a greater loss.

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the minimum recommended unobstructed distance on the side walls is 4 from the front of the Khorn which is approximately 79 from the corner.

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Oddly enough I remember a "dope from hope" paper which mentioned 48" from the corner... although your proposition seems more reasonable. Integrating a 6-1/2' angled wall would be more difficult when you figure this will push the speakers closer to the centre the greater the desired angle is.

Thanks for the inputs so far... got some more thinking to do...

Rob

[Deang]

Artto -- I've gone through some of your old posts, and gone back over our emails -- and I finally understand what you are saying. I have turned my Klipschorns back in to minimize the angle at which the edge of the false corners meet the side walls -- I've also pushed them back as far they will go. The horns are now firing across/in front of me, and though still not ideal -- I have to admit it is an improvement.

"...the minimum recommended unobstructed distance on the side walls is 4 from the front of the Khorn which is approximately 79 from the corner. To see this more objectively, draw a line on the floor, parallel to the front of the Khorn, 28 out in front of it, from wall to wall."

I understand this, but have never read this before. My understanding has always been that 48" from the rear to the front completes the horn.

[tigerwoodKhorns]

Have you checked out the Tractrix (spelling??) horn that AL K is building. This will allow an installation like the D-man photo above. You will have to modify the top of the speaker to allow rotation, but it should work.

My concern is that if the horn is recessed inside of the top bin, the disbursement outside of the mouth of the horn may be interupted on the top and bottom.

Chris