Polars Plots for Altec Multicells?

[weltersys]

Originally Posted by Kindhornman

There is much going on here that seems to have been lost. I'll stay out of the Synergy or Paraline discussion for now, but there are many design issues with both of these on a very technical basis. You may want to overlook those issues but they are there.

There are "design issues" with every type of horn design, I have pointed out many of those issues in this thread.
Like you, I have been around through the introduction and refinement, and abandonment of the pinched throat horns as they made their way around Altec, EV and JBL, and owned quite a few of the latter two back in the 1980s.

Each horn type has positive and negative aspects that must be weighed against each other for the desired application.

I would not advise the use of the Paraline for home use, the negative aspects outweigh the positive.

Any technical issues inherent in the Synergy design approach are far outweighed by the many technical issues it solves.
The simplicity of construction, saving in real estate, reduced midrange distortion, even dispersion, and single point source radiation pattern in my opinion make it a winner for the mid/high portion of what Steve is attempting.

Steve will hopefully make up his own opinion after making a listening comparison between horn types.

Art

[Kindhornman]

Art,
On your last post I am in complete agreement with you. I see no good coming from trying to use the Paraline in a home environment for high end sound applications. I understand your position on the Synergy design for large format PA use.

[weltersys]

Originally Posted by Kindhornman

Art,
On your last post I am in complete agreement with you. I see no good coming from trying to use the Paraline in a home environment for high end sound applications. I understand your position on the Synergy design for large format PA use.

The Synergy design is applicable for large format PA use or home use, one great feature is they sound coherent in the near field (as near as the horn mouth) or at stadium distances.

Obviously, the driver count, amplification power needed for the desired SPL, and dispersion patterns can all be adjusted for home use.

As the requirements for surround speakers are different than left/center/right, I would not likely be using the same dispersion pattern for the side and rear, but that is yet another "design issue" for Steve to consider.

Art

[steve71]

Originally Posted by weltersys

The nice curves reduce difraction..

The questions raised by Bear and Kindhornman's objections were clearly answered in my posts #63 and 65, take a close look at the on and off axis response of a conical horn coupled to an "old school" driver.

You can look up Keele's work, and see comparisons of 10 cell horns and all that:
http://www.xlrtechs.com/dbkeele.com/...xp%20Horns.pdf

What I referred to as the Keele break, simplifies all his math, but basically amounts to after 2/3 of the length from the conical portion of the horn, the sidewall angle is approximately doubled, ie, a 60 "breaks" into around 120 degrees at the end. Wider dispersion angles require less than double the "break" angle, as can be seen in the top veiw of a Manta Ray horn.

The exponential throat portion of the Manta Ray was responsible for good LF loading, the conical portion provided excellent pattern control.
Pattern control is of paramount importance in covering large audience with multiple horns, as overlapping patterns create interference patterns, reducing intelligibility.

Unfortunately, the hard break between the throat as well as the long throat section cause distortion problems (Earl's HOMs) and the long throat before the break causes an acoustical center variation with frequency.
Keele fixed one major problem of exponential horns, but introduced several sound quality issues.

Using a small offset horn midrange cone on the same conical horn eliminates the need to cross so low, so loosing the LF loading the exponential section provides is no longer an issue.
It provides a single point source, eliminating a big "elephant in the room" problem- large format horns won't be within 1/4" wavelength of the mid cone driver at the crossover frequency, so by design will have off-axis vertical problems, those problems come raining down from ceiling reflections.

You can build conical expansion 2 way cabinets using your 288s not much bigger than your multicells that will go low enough to cross in to the Gjallerhorn.

If you did decide that you still need supertweeters, you could stick them on top, with the same problems you'd have sticking them on top of any other set up.
You probably won't need or want super tweeters for surround, as it is normally band limited already.

Art

Thanks for all the info and the link. I understand the theoretical limitations of the multicells beaming when used above the point at which the individual cells break the 1/4 wave length rule. It's just in practice where there are peaks and nulls all over the room, how much of an issue is it? The multicells do sound great, but I would love to hear the SH-50's.

Anyway I might be buying a hand full of Altec A6's. At the very least they should keep things moving with the theater build and buy me time to study the synergy horn without holding things up.

[Pano]

Yes they should.

FWIW, I run multi-cells but also like the synergy horns. They do different things well. Both are enjoyable to listen to.

[steve71]

Originally Posted by Pano

Yes they should.

FWIW, I run multi-cells but also like the synergy horns. They do different things well. Both are enjoyable to listen to.

1505's? Any incite into pro's & con's?

[Pano]

The 1505s are my favorites. Alas - too rich for my blood. I run the more humble 1005, which isn't bad for a small room. I also own 803s, which are nice, but not as nice as the 1005s.

The only cons I find is that it's hard to get the big multis to play high, ~7-8Khz is tops. But that may be driver dependent. I remember with Westrex drivers on the 1505, I really didn't feel the need for tweeters. They did add some "air" but I usually found it artificial sounding.

I'm a fan of the multicell. I just don't know another type of horn that gives me such a realistic sounding space and timber. Some folks don't like them, but I suspect much of that is on a theoretical basis, not from listening to them in a well implemented system.