Wide Dispersion Systems & Room Golden Ratios

[KT66]

As the hot topic on Horn Blasphemies or 'Why the hell use Horns' was getting unwieldy to read & follow ..

Readers will recall I advocate wide dispersion (WD) for the various good(?) reasons submitted there BUT, of course, room effects will prevail and rooms with good proportions are ever more necessary to avoid objectionable standing wave re-enforcements excited by the omni dispersion systems - objectionable mainly at the low end, BTW.

That might be why some of you claim that 'narrow' or 'controlled dispersion - what ever that means'** speakers sound better in some rooms .. true, I believe it.. becaused they might be taming a 'bad' room. But then that's like making a virtue out of a fault.

Note:1 ** If by 'controlled' you mean 'wide' I agree else ..

best to go WD and have your architect design you a room with good proportions.. what ? yea ok ..

Elsewhere I've mentioned PWK's Dope from Hope on this subject of Bolt's Golden Ratios.

Oh .. lest I get shot down in flames, 'narrow' speakers will also sound better in a good room so no need to say you can't afford an architect and invest in cheap beamy speakers instead.

Note 2 : WD is the practical solution to a pie-in-the-sky omni system so the terms are interchangeble for the purposes of this thread.

[boom3]

I agree with everything you said, save for the last part. I've heard several pie-in-the-sky omni systems that have elaborate back stories about point sources being the supposed Holy Grail of speakerdom. It's all baloney. The omnis of the 70s-remember the Design Acoustics DA-12 dodecahedrons? were mediocre speakers with cheap drivers blasting every which-a-way. Then there were the lemmings who followed the Bose 901 with cutesy designs based on crystal shapes. Live musical instruments are not point sources, and after being processed through the recording chain, recorded music is nowhere near a point source. The point source boys-among them Amar Bose-took a leap from single-frequency electromagnetic radiation in free space and tried to fit acoustics, and practical loudspeakers into it. Going back to PWK, the ideal radiation pattern of a speaker is 90 degrees uniform over every audible octave. If you have cornered, high quality speakers you are getting the closest approach to that. I add the caveat that speakers designed for very wide dispersion don't do well in corners due to early sidewall reflections. I built a pair of systems that has about 120 degree dispersion up to the 9th octave. It sounds mediocre in corners due to these reflections. That's one reason why they were replaced with Cornwall IIs.

[KT66]

I agree, corner placement requires the 90deg sectoral coveage. WD systems will obviously perform best without nearby objects to reflect and confuse (blur) the stereo image. Keeping clear of objects will be diffcult to achieve in all installations. But this can be said of any system.

A more or less uniform room wall illumination that does not compromise the direct path (speaker->ears) would be the ideal. This will require furniture distribution control This direct path is what is used by the ears to form the stereo image the rest is balanced reverberation that adds presence.

Incidently, corner placement is the optimun position for best room illumination (eigentone exitation)

[TBrennan]

KT---What horn patterns have you experimented with and which do you prefer?

I've used horns and lenses from 60 degrees horizontal to as wide as 130 degrees. IMO&E horns of about 90 degrees worked best in the main room I was using. However in another room 60 degrees worked very well.

In only one case did I think that very wide patterns were good; that was a case of substituting 120 degree radials for the stock mid horns in a pair of LaScalas. In that case the wider pattern tamed the "fierceness" of the LS midrange in that situation.

Very wide patterns did give a big "cloudy" sound that might appeal to those that like a big soundstage; fans of Maggies say. But I think the effect was overdone.

[KT66]

TBrennan

I think the differences you describe might be due to ratio of direct to reflected (reverberant) sound and in a given room you might over egg the pudding. At one extreme with only direct sound it would be like listening thru headphones at the other a very confused wall of sound a la Phil Spector and boomy bass depending on the bottom-end room responses.

Some might even suggest tayloring driver dispersion patterns to suit each room - hardly a commercial proposition!

BBC studio monitors were designed with wide axial responses and hence the recommendation to always mount them at least 3ft from rear wall and clear of near objects ( and never, ever in a corner). The idea is to give the direct wave an excellent chance of reaching the listener before the rest of the turmoil.

I do not claim to be an acoustitian much of what I've suggested can be read in various treatises by John Watkinson.

BTW, I use La Scalas and they are a bit 'forward' but isn't the Khorn that uses idem mid/hi drivers equally so ? If not why not ?

[TBrennan]

KT---I think matching dispersion patterns to the room is a good idea indeed. However one pretty much has to be a DIY speaker enthusiast to do so.

The other day I heard highly modified K-Horns that used Altec 511B midhorns (with a TAD 2001 drivers) and wide dispersion Beyma tweeters. Several posters on this board are using similarly modified "Klipsch" speakers. I suspect that the wider dispersion of such mods is what people are liking about them as much as improved driver performence.

[artto]

I think possibly youre confusing terms. Controlled Directivity, as PWK put it, is simply that. The directional qualities of the speaker, particularly the mid/treble, are controlled (such as by a particular horn design), so that the speaker radiates into a specific angle of coverage (horizontally & vertically) for the typical conditions it was intended.

Since PWK recognized that speakers placed in the room corner are able to perform more efficiently, especially in the low-end, thereby lowering distortion, and that the widest angle of room coverage can be obtained from that same location while maximizing the output of the speaker over that same angle of coverage, his designs reflected this observation.

Wide dispersion systems are not responsible for objectionable standing wave re-enforcements excited by the omni dispersion systems. This is strictly a phenomena related to room proportions, primarily in simple shaped rooms, where any or all dimensions are equal to, or shorter than the longest wavelengths being produced. In fact, the best place to excite any & all room modes is in the corner. What and how much of any of these effects you actually hear will also be affected by other objects in the room, the speaker locations and your position in the room.

[D-MAN]

Tom has enlightened me (go figure!) on an important point that I found to be true by empirical testing that I would like to pass on...

The "tighter" dispersion characteristic horns CAN TEND to be harsher, that is, the 60x40 deg. CAN be more harsh or biting than a 90x40, etc, given the same driver. In particular, I am speaking of the midrange horns.

I've found this to be the case, using the same driver on different horns with the horn dispersion being the only variable that was changed. I've settled on the 90x40 as being my fav.

DM

[3dzapper]

"BTW, I use La Scalas and they are a bit 'forward' but isn't the Khorn that uses idem mid/hi drivers equally so ? If not why not ?"

The bass response is much better than that of the LaScalla which, after all, is a PA speaker. The increased bass output and lower response of the Khorns better match the mid and HF horns. It's hard to describe but, Khorns when compared to other speakers including the LaScalla, Belle, Cornwalls have a "big" sound the others can't match. The loading of the room by using the boundries as a part of the speaker is more complete.

Besides the Khorns and LaScala I also have Heresys. Even with an SW-15 subwoofer, they lack the bigness of the Khorns although the sub can go "lower". (Sw-15-3db=27Hz;

Klipschorn -3db=35Hz; Lascala -3db=53Hz; Heresy -3db= 63Hz)

Rick

[sfogg]

Rick,

" Even with an SW-15 subwoofer, they lack the bigness of the Khorns although the sub can go "lower". (Sw-15-3db=27Hz; Klipschorn -3db=35Hz; Lascala -3db=53Hz; Heresy -3db= 63Hz)"

Might be because you have stereo bass on the K'Horns vs. mono bass with the sub. Stereo bass can be perceived (different then localized) down to around 40ish hertz. It can add a sense of spaciousness and envelopment to the playback compared against mono reproduction if the recording has stereo bass in it.

Shawn

[WMcD]

I had sort of avoided the subject in responding to the Blasphomy thread. A discussion of directivity would inject another level of complexity.

PWK had described his midrange horns as having "controlled directivity". This was in contrast to the then, new, constant directivity.

Part of the problem with a midrange horn is the driver. The output rolls off, typically, above 3 kHz. If the horn mouth is relatively small, it becomes more directional (in the vertical plane) above 3 kHz. The output narrows down, again in the vertical plane. This allows the combination of horn and driver to work up to 6 kHz.

In theory (my theory), the K-400 etc. have somewhat constant coverage in in the horizontal of about 90 degrees.

Per Don Keele, this whole directivity thing demands mouth sizes which are relatively large. In fact, if you want a narrow coverage, you need a bigger mouth in that axis. It is all relative to the wavelenght being transmitted.

Also, I'd pointed out that the "Tratrix" midrange (used in the Forte II) uses a larger mouth height than the exponential it replaced in the Forte. The directivity in the vertical plane is more narrow with the taller mouth. And because it doesn't have to have 104 dB of response, we're not trying to squeeze out every last dB out of the combination by directivity.

One upshot of this is that if the horn only has to work down to 1.5 kHz (to pick a number) you can get directivity without a huge midrange horn.

It is somewhat a "thought experiment". You have to look at horn dimensions in terms of the critical wavelenghts. Horns of the same dimensions vary in "size" as wavelenghts vary.

Please note that some of Klipsch "Inc."'s more recent midranges use a tall mouth. It looks a bit like an old CW with the vertical oriented mid.

The above is a discussion of what you need to get a relatively narrow beam and why you might need it. The next issue is whether it is beneficial.

I believe it is beneficial. An inital thought is that a wide "sweet spot" is good. That may be true.

However, it is also beneficial, in the case of the front speakers, to keep the sound off the nearby walls, floors, and ceilings. So we have the goal of constant power toward the listening area AND which drops off very quickly at the edges so that it does not spray the walls, floor, and ceiling.

Extending the sweet spot out to the walls makes for walls in the sweet spot so they can reflect sound back into the room. That is to say, a lot of reflections; which is bad.

We've seen the results of people's experiments with toe-in and wonderful results from such adjustment. In my view it is not simply a matter of the on-axix listening. Rather, it is also a matter of keeping the off-axis radiated power, off of the walls. Toe in and corner placement may well do both. However, alternate placements may be better in a given room. So experimentation is necessary.

Let me say that again in a different way. We want to keep direct sound at a high level, and reflected sound at a low level. This is again talking about the mains. A high ratio of direct sound to reflected sound is good. It makes the set more like our room does not dominate over the one in which the recording was make. Otherwise, we're listening to two rooms. The one in which the recording was make, and ours.

OTOH, we have a different requirement for surround speakers at home. Their output should seem to come from everywhere in the room. This is why the Klipsch surrounds use two horns to spray sound around as much as possible. We want more reflections off the walls. An alternative is to have treated walls and multiple speakers, as we find in movie theaters.

To some extent Bose was honoring the reflected and direct theories in his big seller which put six drivers at the back and one in the front. This grew out of his thought that sound in a concert hall was dominated by reflections off the walls. So he made a speaker which did that in a living room.

Best,

Gil

[jdm56]

Just a brief little comment about the relative "bigness" of klipschorn sound: I think that can be attributed to the simple fact the thing is sitting tight in a corner. There is a lot of output from the lower mids on down that are reflecting off the room side walls and combining with the direct radiation at such a short delay time, that the ear hears only one big image. You can prove this out by placing any normal speaker in a corner. Magically, it suddenly sounds "bigger"!

[3dzapper]

Other considerations with using wide dispersion speakers v controlled dispersion also come into play.

The latest trends in high end speakers has been to "phase align" the drivers by raking back the front driver panel and eliminating "enclosure reflections" by tapering the top of the enclosure or mounting the tweeter above the motor board.

These modifications, usually involving very large very expensive speakers necessitate the positioning of the speakers far from the room boundries. We've all seen pictures of huge $70,000 speakers in nearly the middle of the listening room so as to eliminate direct reflections from the walls.

When looking at those pictures I notice also that the speakers are "toed-in", as Gil says, and pointed at a chair in the one sweet spot. If there is but one sweet spot and the speakers are so boundry dependant, I fail to see the advantage in this latest technology. The difference in sound is as much to do with the expensive drivers employed as well as the vibration control employed at great expense to the enclosure. Some of them rival the Space Shuttle's spar system.

One must remember here that we are comparing Klipsch whose top of the line Klipschorn has a retail list price of $7,500 with speaker lines that exceed the average annual incomes of the majority of the US or UK families. That plus they look like ugly robots, boats or phalluses in the middle of the room means that most wives would simply say no. Another consideration.

I have often said here and elsewhere that Klipsch represents the best bargain in high end audio. Just the fact that they are routinely compared to the most expensive speakers in the world is testimony to that.

Rick

[3dzapper]

Other considerations with using wide dispersion speakers v controlled dispersion also come into play.

The latest trends in high end speakers has been to "phase align" the drivers by raking back the front driver panel and eliminating "enclosure reflections" by tapering the top of the enclosure or mounting the tweeter above the motor board.

These modifications, usually involving very large very expensive speakers necessitate the positioning of the speakers far from the room boundries. We've all seen pictures of huge $70,000 speakers in nearly the middle of the listening room so as to eliminate direct reflections from the walls.

When looking at those pictures I notice also that the speakers are "toed-in", as Gil says, and pointed at a chair in the one sweet spot. If there is but one sweet spot and the speakers are so boundry dependant, I fail to see the advantage in this latest technology. The difference in sound is as much to do with the expensive drivers employed as well as the vibration control employed at great expense to the enclosure. Some of them rival the Space Shuttle's spar system.

One must remember here that we are comparing Klipsch whose top of the line Klipschorn has a retail list price of $7,500 with speaker lines that exceed the average annual incomes of the majority of the US or UK families. That plus they look like ugly robots, boats or phalluses in the middle of the room means that most wives would simply say no. Another consideration.

I have often said here and elsewhere that Klipsch represents the best bargain in high end audio. Just the fact that they are routinely compared to the most expensive speakers in the world is testimony to that.

Rick