I view the degenerate case for a horn as a flat baffle: it still has gain (half-space). Many like to use the term "baffle step", but it's where the flat baffle fc occurs due to "mouth size" or 1/4 wavelength across the baffle width. Apparently straight-sided horns have gain below fc just like the special case of conical expansion (i.e., S=x^2).
Danley talks at length about the continuously changing area expansion rate for the "conical" profile, but he's really talking about straight-sided more generally--not just x^2. Beranek and Olson both show real acoustic resistance below "fc" for the conical expansion, which is true also for straight-sided. This is an extremely important property for the MEH loading to a very low frequency without having a horn mouth the size of a room wall, as it would be in the case of exponential and hyperbolic expansions. It's the reason why the Khorn works so well below its anechoic fc of ~110 Hz.
Somewhere between 90 degrees and 180 degree horn coverage angles, the beneficial effects of horn loading disappear. I'm referring to the "tight, crisp horn-loaded bass" sound, i.e., apparent absence of modulation distortion and mass effects of the direct radiator dominating the sound at low frequencies. At 180 degrees coverage angle, it sounds just like a direct-radiating woofer.
Le Cléac'h horns have issues with non-constant polars (as do all non-straight-sided horns). They work well as midrange horns only if placed far away from room boundaries and the room is fairly dead acoustically, but IMO fall apart when in boundary effect due to non-constant polars.
The K-402 isn't conical, but has about 2/3s of its axial length dominated by straight-sided sections. Polar coverage control is spectacular...shown anechoically here with vertical scales in degrees (not dB as shown). Handover to room boundary polars and corner gain occurs at the same frequency band as the Khorn bass bin (~110-170 Hz). Its large mouth controls polars below 170 Hz better than the Khorn bass bin:
those are nice polars without a hint of beaming in them but I'm not sure exactly what I'm looking at. What is plotted on the ordinate - the angle at which the SPL is 6 db down relative to on axis?
Is this measurement data from your own MEH? How else would you get full range data? At the HF end, which CD was used and would that affect the apparent coverage ?
The horn begins to lose pattern control about where Keele's formula predicts but its interesting to see where it goes full omni, i.e. where it hands off to the boundaries. Its that transition region between omni and controlled where its so difficult to predict how the room and its boundaries will affect the sound and the measurements.
Is this measurement data from your own MEH? How else would you get full range data? At the HF end, which CD was used and would that affect the apparent coverage ?
The horn begins to lose pattern control about where Keele's formula predicts but its interesting to see where it goes full omni, i.e. where it hands off to the boundaries. Its that transition region between omni and controlled where its so difficult to predict how the room and its boundaries will affect the sound and the measurements.
Yes.
Here is a set of horizontal REW measurements on the K-402-MEH (normalized to zero degrees on-axis response) that I ran in my back yard on an elevated rotating base. Note that the designed coverage angle is 45 degrees (90 degrees included angle) - halfway between the two orange traces:
Put them into full corners and the transition is seamless (both measured and while listening to an upsweep). Put one along a wall elevated off the floor and the response is little changed except a loss of frequency response from 31-40 Hz and the widening of polars at 110 Hz--which is fairly graceful in that it occurs at a low enough frequency where localization of early reflections isn't an issue (i.e., all well below 170 Hz).
I find that it behaves in a much more user friendly way in terms of freedom of room placement than the Klipsch horn-loaded bass designs. Perhaps this is due to the K-402-MEH having enough woofer radiating area to compensate for mid-wall placement.
I find that there's quite a bit of latitude in how to handle the room boundary handover with this MEH design.
No folds in the horn design, having a well designed horn mouth without intermediate impedance bounce points (i.e., no hard chine flare ridge in the mouth that's present in Danley SH horns), and a coverage angle that matches the room corner boundary angle--all work to the advantage of integrating the MEH into the room quite well.
No attempt was made to incorporate mouth baffles to smooth the acoustic transition to the room boundaries. With just a little effort, further room transition could be easily had if you feel it necessary. I didn't...
The compression driver used in the anechoic plots was a B&C DE75, I believe.
The full range data was apparently collected from the lower output of the driver in this range - because it was in an anechoic chamber. The Klipsch anechoic chamber in Hope is only good down to about 100-125 Hz due to its internal dimensions. It would take a very large chamber to get good anechoic data at lower frequencies.
The full range data was apparently collected from the lower output of the driver in this range - because it was in an anechoic chamber. The Klipsch anechoic chamber in Hope is only good down to about 100-125 Hz due to its internal dimensions. It would take a very large chamber to get good anechoic data at lower frequencies.
Thanks.
Yes corners are great if you can use them as we both do.
I think the K-402's tall mouth helps immensely with floor bounce. Can you elevate yours high enough to bring the axis up to seated ear level without getting a floor bounce null that carpet can't kill?
re' Perhaps this is due to the K-402-MEH having enough woofer radiating area to compensate for mid-wall placement
I think what happens at midwall is that you can be some distance out of the corner and still get support at the low end of the woofer's range, where it is needed. But because you aren't in the corner you may have to address sidewall reflections.
That 2nd woofer doesn't hurt either. In the MEH, the woofers have the low end extension of a sealed box with the pattern control of the horn mouth, which is the best of both worlds. A little LT, some room gain and corner gain and subs may not be needed even for HT.
But I was disappointed to find that my room walls become transparent to sound somewhere around 30 Hz. My first clue was during break-in when the test tone was just as loud on the opposite side of the garage wall from the speaker.
I don't worry about the floor null. The K-402-MEH controls its polars down so low that the 1/4 wavelength floor null isn't really an issue with the loudspeaker being elevated. When I get three across, I can bring the horn axes down about a foot or two relative to the height of the present Jubilees. This will raise the 1/4 wave null point into a region where the MEHs won't experience a strong null.
Well, maybe for you...but in my room, I get clean and rising response down to ~16 Hz using the two TH subs in the corners. The subs also provide a very stiff false corner (half of one, that is) to move the corner speakers out into the room by an additional foot or so. I know when the subs aren't on, and they're on all the time.
Bummer. I find that below about 25 Hz, the master bedroom directly upstairs experiences everything, too.
The beamwidth is probably the main factor from which I guessed the profile. I'll post examples of where I surmised that. The middle two profiles shown to bear some resemblance to the H and V of the 402 are Hyp/Ex curves whose catenoid asypmtotes to conical at the throat.. not that this has to imply anything about the 402 of course.
Attachments
Depending on how closely the device fits in to the corner, even the highs are going to diffract a little around the edges. The proximityof the walls will be a problem but the highs are not difficult to absorb. At the low end the disturbance won't mean much, which leaves what to do about the transition region and where to put it.
If the gap between the horn straight section (the effective parallel to the wall) and the wall is large enough there might be an axial reflection if the horn is also currently loading some given frequency.
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Perhaps a bit more discussion of the vertical coverage angle: there have been comments about 40 degrees vertically, but that implies that the vertical dimension of the listening room is perhaps less than 8 feet (2.4 m). How many here have or know of listening rooms with low ceilings less than 8 feet?
How many would be able or willing to accommodate 60 degrees vertically--as in a 60 x 60 degree horn vs. a 60 x 40 degree horn?
Chris
How many would be able or willing to accommodate 60 degrees vertically--as in a 60 x 60 degree horn vs. a 60 x 40 degree horn?
Chris
If facing a choice between a 60x60 horn or a 60x40 horn, I would choose a 60x60. I think vertical pattern control is important and obviously control extends lower with the taller horn. But my first choice remains 90x60 because 90H nestles so well in a corner and illuminate the entire room. I tried 90Hx45V and my experience shows I would have been better off with 90x60.
60H horns don't fit corners so well and don't illuminate the entire room. Yes, Wm. Cowan built one into a corner but what he really did was build a baffle wall across a corner and then built the horn into the baffle wall.
Interesting that you relate a lower vertical angle to a lower ceiling height. It shows a concern with ceiling reflections. This is a subtle point. I think what is behind it is that the floor reflection is what it is and will always have to be dealt with - even if only with a hand waving argument that the ears tunes it out. Where the ceiling reflection lands depends on the ceiling height. Ideally it will pass over the listener's head and ultimately become a beneficial late reflection. But this is only true for frequencies for which the horn has directivity.
The dilemma is that, assuming fixed width, the radiation from the 60V horn will hit the ceiling closer and land closer in than the radiation from the 40V horn but the 60V horn will control the radiation over a wider frequency range. Which is better? In "My Synergy Corn Horns..." I found that the floor and ceiling reflections at frequencies below the vertical pattern control limit were the biggest problem. Thus I believe that the tallest horn mouth is the best, independent of ceiling height.
Yeah, historically the goal is no first reflections in front of the listening position, then a diffuse soundfield behind it, so while vertical reflections don't impact us near as much as horizontal, it definitely messes with imaging and why with the so called 90x40, 100x60, etc., horns I've used that are anything but except over a very narrow BW; I've added foam horn extensions combined with toe-in and elevated, pointing down to bleed off, focus a goodly portion of their output to minimize all that's required to 'voice' the room before getting smart and making huge ~125x60 conical horns to control them down well below 1 kHz, though still needed a small amount of mouth damping.
GM
GM
Interesting points.
Note that a large "90x60" (about 1 metre by 2/3 metre mouth size) is in the works as a default for my own personal needs.
The next design problem, however, is a multiple-entry horn for really small listening rooms. Just a point here: a lot of people believe that smaller horns are required for small rooms, but in fact the opposite is true. Since all the dimensions of the room are shorter, all the characteristic first reflection delays are shorter (which are well within the Haas zone time delays), and the characteristic absorption percentages and diffusion effectiveness are likely much lower in these small rooms. This means that it's much more difficult to get a loudspeaker that integrates well with the room, no matter where you place them in the room. It's hard to get anything that sounds good. All the problems stack up and go in the wrong direction when dealing with small rooms.
One thing is true in my experience: increase the direct to reflected ratio and things will sound better. Really large mouth horns perform better in these instances because the challenge is to keep the loss of polar control below the room mode frequency of floor-ceiling dimensions - and this is usually 110-140 Hz band. If you can control the polars to below this room mode frequency, then room "bass trapping" issues seem to be much reduced. This implies a horn of the mouth size that I identified above. Larger horn mouths are definitely needed. This is also a point that I heard from a Klipsch horn design engineer a number of years ago: small rooms require larger horns, not smaller.
One way to do this is like GM mentioned: build extensions to your horn mouths with some absorbent material (like the older Peavey QT horn uses). I recommend using absorption right at the horn mouth-side wall interface in any case to dramatically improve imaging.
So it's this "small room-large mouth horn" need that creates the more controlled and smaller coverage angles. So there is still is a need for a 60 degree horizontal horn--and it is almost is exclusively needed in really small listening rooms.
If one were going to recognize these small rooms as a characteristic for another distinct customer segment, then a smaller coverage angle horn of fairly good-sized mouth dimensions will be required in order to control these problematic early room reflections (and that I find these room sizes are typically found in countries outside of North America...especially in the EU and near east). The mouth dimensions of the Danley SH50 or SH-60 are at the small end extreme for these hi-fi applications in small rooms, it would seem.
Perhaps this is why the Le Cléac'h profile horns are so popular in the EU - because of their effectively smaller coverage angles in smaller rooms. Those horns have really narrow full-range coverage due to their curved side walls, but if they are aimed away from the walls, they behave much more like a narrow coverage pyramid-type MEH in terms of full-range coverage angle (circular cross section--which causes other issues at some distance away from the horn mouth).
Chris
Note that a large "90x60" (about 1 metre by 2/3 metre mouth size) is in the works as a default for my own personal needs.
The next design problem, however, is a multiple-entry horn for really small listening rooms. Just a point here: a lot of people believe that smaller horns are required for small rooms, but in fact the opposite is true. Since all the dimensions of the room are shorter, all the characteristic first reflection delays are shorter (which are well within the Haas zone time delays), and the characteristic absorption percentages and diffusion effectiveness are likely much lower in these small rooms. This means that it's much more difficult to get a loudspeaker that integrates well with the room, no matter where you place them in the room. It's hard to get anything that sounds good. All the problems stack up and go in the wrong direction when dealing with small rooms.
One thing is true in my experience: increase the direct to reflected ratio and things will sound better. Really large mouth horns perform better in these instances because the challenge is to keep the loss of polar control below the room mode frequency of floor-ceiling dimensions - and this is usually 110-140 Hz band. If you can control the polars to below this room mode frequency, then room "bass trapping" issues seem to be much reduced. This implies a horn of the mouth size that I identified above. Larger horn mouths are definitely needed. This is also a point that I heard from a Klipsch horn design engineer a number of years ago: small rooms require larger horns, not smaller.
One way to do this is like GM mentioned: build extensions to your horn mouths with some absorbent material (like the older Peavey QT horn uses). I recommend using absorption right at the horn mouth-side wall interface in any case to dramatically improve imaging.
So it's this "small room-large mouth horn" need that creates the more controlled and smaller coverage angles. So there is still is a need for a 60 degree horizontal horn--and it is almost is exclusively needed in really small listening rooms.
If one were going to recognize these small rooms as a characteristic for another distinct customer segment, then a smaller coverage angle horn of fairly good-sized mouth dimensions will be required in order to control these problematic early room reflections (and that I find these room sizes are typically found in countries outside of North America...especially in the EU and near east). The mouth dimensions of the Danley SH50 or SH-60 are at the small end extreme for these hi-fi applications in small rooms, it would seem.
Perhaps this is why the Le Cléac'h profile horns are so popular in the EU - because of their effectively smaller coverage angles in smaller rooms. Those horns have really narrow full-range coverage due to their curved side walls, but if they are aimed away from the walls, they behave much more like a narrow coverage pyramid-type MEH in terms of full-range coverage angle (circular cross section--which causes other issues at some distance away from the horn mouth).
Chris
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Yes, that is my horn... I am waiting for Chris to make some available so I can get them for a 7 or 9 channel setup for my next HT.
Hopefully we will have my amp up and running soon to see how my speaker performs too. I am going to be moving soon, and will most likely give my friend the cabinet that was built regardless of how it performs as it is very heavy, and would be expensive to ship. I will post up the results if we get them before I move.
A consideration about the horn
Hi Chris (and others),
I hope this thread isn't dead
.
I was just wondering about the horn: I know that you have used the Klipsch K-402 horn, and it may be the best available candidate out there for a no-compromise MEH-kit. An alternative might be to have a company like the Polish company Autotech make a dedicated MEH from scratch. In order to be economically feasible, it would probably require a batch of quite a few horns to be made, though. However, the horns they currently sell seems to be well made and very fairly priced (I have no affiliation with the company...). The obvious advantage of the latter approach would be that the horns could be made exactly to the desired specs and optimized for this specific purpose (i.e., premade holes for woofers; perfect transition at the throat from round to rectangular, etc.). In addition, it would be really nice - at least to some of us - to be relieved of putting together a complicated flat-pack...
I do not know whether this would be impossible due to patent rights and equivalent, though...
You may already have considered this, but if not, I thought it would be worth a consideration.
Best regards
Peter
Hi Chris (and others),
I hope this thread isn't dead
.I was just wondering about the horn: I know that you have used the Klipsch K-402 horn, and it may be the best available candidate out there for a no-compromise MEH-kit. An alternative might be to have a company like the Polish company Autotech make a dedicated MEH from scratch. In order to be economically feasible, it would probably require a batch of quite a few horns to be made, though. However, the horns they currently sell seems to be well made and very fairly priced (I have no affiliation with the company...). The obvious advantage of the latter approach would be that the horns could be made exactly to the desired specs and optimized for this specific purpose (i.e., premade holes for woofers; perfect transition at the throat from round to rectangular, etc.). In addition, it would be really nice - at least to some of us - to be relieved of putting together a complicated flat-pack...
I do not know whether this would be impossible due to patent rights and equivalent, though...
You may already have considered this, but if not, I thought it would be worth a consideration.
Best regards
Peter