Great Waveguide List

D220Ti derives its VHF extension from resonance of the "snowflake" diaphragm embossing rather than pistonic behavior, much as JBL relies upon their diamond surround for similar. That shows up as what it is in CSD, breakup modes exhibiting stored energy, in my view. Both are also titanium with limited damping inherent in the material itself, as opposed to aluminum, for example, or poly, and thus, best practice is provide damping via other means, such as a dusting of Aquaplas, as JBL does in its TOTL versions of their drivers.

Yes, they sound different; DE250 and BMS, for example, being decidedly "smoother." Remember, however, that the original entry-level EconoWaves are intended as an economical introduction to the particular pleasures of constant directivity system design, and we make no apologies for this, providing clear upgrade paths for those so desiring's further pursuit. Even the bolt-on D220Ti on QSC 152i is an audible improvement, as others have found.... :)

Footnote: Wayne Parham is correct -- the round waveguides suffer the center-to-center distance issue in the verticals, as I have demonstrated in "Flex It" prototypes. A 10" axisymmetric cannot play as low in the horizontal as a 14" x 10" asymmetric like 152i which further benefits in pattern control and workable crossover frequency from narrower beamwidth in the vertical. Thus, considering best design practice, the asymmetrics win hands down, which is why I don't do round waveguides except to illustrate the requisite compromises. Geddes concedes the Nathan waveguide is too small to be crossed as low as he does in that design.
 
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... the asymmetrics win hands down, which is why I don't do round waveguides except to illustrate the requisite compromises. Geddes concedes the Nathan waveguide is too small to be crossed as low as he does in that design.

Improperly stated: I DO crossover "as low as he does" and and make it work (sure bigger is ALWAYS better), but the product gets rave reviews, which pretty proves my point that CTC spacing is way overblown.
 
Earl has asserted many times in these very pages -- given the option, we go with the data; there's no excuse for not doing the best we can with what we know. He has steadfastly refused to publish the verticals, but we got a first look at Nathan in the Princeton polars a couple of weeks ago, and they support Parham's position.

It's easy enough to suggest that they don't matter, or that one doesn't care about them, but falling back upon "People like the product" in the context of not presently being able to do anything about the issue seems, well, somewhat vacuous.

[There's no need for me to suggest what other products people like here; we all know THAT drill, too.... ;) ]
 
Here's that 10"PE WG with the D220 measured in the center out to 45 degrees off axis with a 6uf cap in line:
4374573056_2c500f6cd5.jpg


Dan
 
Footnote: Wayne Parham is correct -- the round waveguides suffer the center-to-center distance issue in the verticals, as I have demonstrated in "Flex It" prototypes.

Hello Zilch

Why are you limiting it to round waveguides?? What about rectangular waveguides with a symmetrical pattern like the 2342 and 2344 used in the 4425 and 4430 monitors?? What about the symmetrical PT waveguides?? While we are at it how about the Array series Bi Radials that deliberately set the CTC worst case??

They are just as compromised as Earls rounds and the Arrays even more so. Not to mention all the PT boxes that use a rectangular waveguide independent of the pattern. They are all no good?? If so why??

Rob:)
 

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Hi, Rob,

It's not only about center-to-center distance, but also the crossover frequency -- for any given C/C distance, a lower frequency (the crossing over generates the vertical nulls) provides a wider (taller) forward lobe.

The difference between sitting and standing in a typical home listening setting is ~10°, and thus, the forward axis in a system with a 10° (-6 dB intrusion) vertical lobe must be precisely aimed (steered) midway between them. I typically aim for a minimum +/- 10° lobe about the design axis.

I have all of those horns, and a bunch of the square PTs, but have never measured their vertical polars in systems. For SR applications, there is considerably more freedom, because the distance to listeners is usually greater, but for quality listening, it matters. At -6 dB, we may as well be listening to Earl's speakers in their on-axis notch.

The other element in this is the dispersion pattern of axisymmetric waveguides. The nulls extend full beamwidth and "color" the floor and ceiling bounce. With typical asymmetrics (40° - 50° vertical pattern), the design can actually use the nulls to augment the pattern control in the crossover region where the transition from woofer to waveguide occurs. Have you watched Wayne's video?

http://www.pispeakers.com/misc/Vertical_Nulls.wmv
 
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Hi Zilch

It's not only about center-to-center distance, but also the crossover frequency -- for any given C/C distance, a lower frequency (the crossing over generates the vertical nulls) provides a wider (taller) forward lobe.

Yes that's true. That's why I don't understand why you would automatically discard a axisymetrical horn/waveguide. It's the total design that determines how far apart and where the nulls will be. I am not disagreeing with you that there can be advantages to closer spacing I just don't see it as a paramount concern when I am looking to choose what horn to use. Hey that's just me we all have our own design criteria that we use.

There are some really decent horns/waveguides that would be discarded on that parameter alone that you could use and end up with a fine sounding system. I just look at it from the point that it can unnecessarily limits your choices.

Rob:)
 
The main reason I went with a round OS waveguide is that 100% of the sound comes from an OS waveguide.

Not 50%.
The other half of the sound comes from a non OS waveguide or horn flare.
Which half are you listening to?
Heck if I know, so I chose to be 100% certain it would be OS WG.

Sure sound bounces off the floor and ceiling with a round OS WG, but those problems are easily fixable.

The lobing is problematic. But I'm not sure it matters all that much. More of a second or third order concern.
 
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The vertical polars as measured by Princeton on the Nathan toward the tweeter:
An externally hosted image should be here but it was not working when we last tested it.

That looks darn good with about a 20 degree window if I'm reading that right. I wish they hadn't used a 10 dB scale!
Toward the woofer:
An externally hosted image should be here but it was not working when we last tested it.

Yea, toward the woofer's not so bueno, but that just means you don't have to put these rather large speakers onto big stands.

The B2031P is similar but as measured by me toward the tweeter in 11.25 degree steps using a 5 degree scale:
b2031polarstweet.jpg

toward the woofer:
4vw.jpg


The Mackie HR 624 mk2 has a similar sized vertical lobe as well. All of these are axisymmetric. At 9ft away, that gives you over 3 ft of a vertical window. I'd think that's plenty. I can't hear any issues with it. I'd say it's not a deal breaker, more like a "proceed with caution" type of thing.

Dan
 
I just look at how broad, or how many lines the response is essentially flat. Then have a look at how many degrees the lines are apart.

In the graph of the Nathan, you can see that there are 3 lines that are nearly identical through the crossover and one that's not too far away--that's roughly a 15 degree window. My first estimate looks off.

The B2031P you can see 3 lines that are roughly the same and they are 11.25 degrees apart=22.5 degrees of good response. Zilch and I measured it in the lab and I think it was a wee bit better than that d/t improved measuring in 5 degree increments. Maybe he'll chime in and confirm that.

My experience basically says that it doesn't really matter at 9 ft/3 meters, but they be d/t the fact that the speakers I've measured will give me 3 ft of flat coverage at my listening position.

Then the distance thing is just geometry. I use this: Right Triangle Angle And Side Calculator

Dan
 
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The jabo horns by le cleac'h should sound excellent also.

High Efficiency Speaker Asylum - 16 horns measurements - Jmmlc - December 07, 2010 at 01:50:12
"The "shoot out" of the European Triode Festival 2010 (ETF2010) was devoted to horns and waveguides. 16 horns were brought by participants to ETF2010 for the contest.
Aside of the official shoot-out I could measure all the 16 horns in the same excellent conditions (a very large room with a very late first reflection)."


There is a 36 page pdf done by le Cleac'h showing new ways of measuring horn reflections. The avantgarde one looks good also. page 19 is his. Notice the lack of grass in his compared to the sectorial horns, and the many reflections in the mantaray horns.

http://forums.melaudia.net/attachment.php?aid=1760

awesome article.

Norman