Arranging drivers "crossfire" style

[jefffluker]

Hey guys (and girls?!?!),

Planning my next speaker project, looking to depart from plain horn/woofer/subwoofer T/S boxes.

I'm curious about the "crossfire" driver arrangement, specifically how it seems to resolve some dispersion and response anomalies.

Questions:

What is the correct or most effective angle between driver planes?

Does this arrangement work with woofers?

Does this arrangement work with compression drivers?

Do passive crossover circuit components (caps/chokes/resistors) alter or negate the gains in dispersion or response?

I'm excited by this technology, and would like to include it in my next design.

Jeff Fluker
jeff@hotwaxunlimited.com
985.543.0057

[Chris Roemer]

Hey guys (and girls?!?!),

Planning my next speaker project, looking to depart from plain horn/woofer/subwoofer T/S boxes.

I'm curious about the "crossfire" driver arrangement, specifically how it seems to resolve some dispersion and response anomalies.

Questions:

What is the correct or most effective angle between driver planes?

Does this arrangement work with woofers?

Does this arrangement work with compression drivers?

Do passive crossover circuit components (caps/chokes/resistors) alter or negate the gains in dispersion or response?

I'm excited by this technology, and would like to include it in my next design.

Jeff Fluker
jeff@hotwaxunlimited.com
985.543.0057

What's a plain T/S box?
Do you have a "crossfire" link extolling these virtues?

[Sydney]

Do you have a "crossfire" link extolling these virtues?

I suspect that the sole link is the web page by programmer Randall Hyde.
( Though it hardly qualifies as a definitive thesis or white paper )

[billfitzmaurice]

Do you have a "crossfire" link extolling these virtues?

http://homepage.mac.com/randyhyde/we...udioStuff.html

[Randy L]

Considering Mr. Hyde's test report, I wonder why the audio world hasn't picked up on this and designed multiple speaker "arrays" in a crossfire pattern instead of splaying. Maybe cabinet design and appearance aesthetics? Or is there more to this than meets the eye?

I also see the report is showing a horizontal dispersion pattern. I wonder what the vertical plane would look like if drivers in a vertical array were crossfired, instead of the typical splaying "curve" we see.

[Sydney]

Considering Mr. Hyde's test report, I wonder why the audio world hasn't picked up on this

This presumes validity and merit: Randall's web page is not a report, and it lacks the basics of objective scientific methodology.
The Pro audio industry is aware of the science and math behind pattern interference ( as evidenced in peer reviewed works, AES papers and reference books )

[billfitzmaurice]

Considering Mr. Hyde's test report, I wonder why the audio world hasn't picked up on this and designed multiple speaker "arrays" in a crossfire pattern instead of splaying.

Splayed cabs only came into being at the insistence of uninformed consumers who insisted on having them. What the market demands manufacturers will provide. Read this set of articles:

http://www.gtaust.com/filter/05/07.shtml

Cross firing isn't a panacea for all sonic ills. You do see it employed extensively in the midrange elements of line array cabs.

[Sydney]

A little further in the series: The Birth of the Array Part5
http://www.gtaust.com/filter/08/07.shtml
Is the recognition:
"The big conventional array is not dead. As much as we have seen their weaknesses, they still have virtues, one of which is flexibility; they will go more places a line array will."
Members of the Pro sound speaker industry ( to expedite implementation ) have provided dispersion data in a standardized format that can be used be "aiming software". If the individual component data is provided, the complex acoustic summation can be calculated.
This facilitates the concept of mapping performance areas with audio building blocks of known properties.
Note also the unseen complex signal manipulation behind the physical transducer orientation.

[AMC]

Hey guys (and girls?!?!),

Planning my next speaker project, looking to depart from plain horn/woofer/subwoofer T/S boxes.

I'm curious about the "crossfire" driver arrangement, specifically how it seems to resolve some dispersion and response anomalies.

Questions:

What is the correct or most effective angle between driver planes?

This should depend on the dispersion of the driver and the area to be covered.

Does this arrangement work with woofers?

Yep

Does this arrangement work with compression drivers?

The effects get 'interesting' at higher frequencies, and a CD and it's associated horn generally are capable of providing wide enough dispersion for it not to be necessary.

Do passive crossover circuit components (caps/chokes/resistors) alter or negate the gains in dispersion or response?

I'm excited by this technology, and would like to include it in my next design.

Jeff Fluker
jeff@hotwaxunlimited.com
985.543.0057

One of the problems I see with it, is it tends to be too bulky for use in a PA top (imagine a PA top with 2 12s side by side) and then what kind of horn? Looks are important to the average consumer. Seems to be a nice option for specialized cabs (see BFMs XF guitar cabs) and it does get used in mids in line array cabs. Could be an interesting option for mids in a 3 way cab, think 1or2 12", 4 6"mids, and a CD?

[AMC]

I also see the report is showing a horizontal dispersion pattern. I wonder what the vertical plane would look like if drivers in a vertical array were crossfired, instead of the typical splaying "curve" we see.

I have actually seen that done. Don't if it was better or worse, but it is done.

[Sydney]

What is the correct or most effective angle between driver planes?

Does this arrangement work with woofers?

Does this arrangement work with compression drivers?

Jeff: Woofers and drivers have dispersion that varies with frequency, and or are attached to devices that effect dispersion. To predict and answer your questions would depend upon those variables

Meyer ( an established pro sound company ) used MAPP software in 2005 to produce a cross-fire plot:

It used 2 Meyer cabs which were NOT designed to be crossed fired; to show where pattern interference was greatest and also resultant null.
It demonstrates the problems with an generalized implementation technique applied inappropriately to the design.

[AMC]

The Meyer example points out the problems with "one size fits all" solutions. That example seems to be wrong because it has them fired at too much angle for the inherent dispersion pattern. Less angle would of course fix (read lessen the problems) this. But drivers have variable patterns, and thus the fix depends on many factors. Cross firing and splaying are band-aids, and not solutions. Cross firing may be a better band-aid, but that is all. It may however be the solution for some situations where a specific environment needs to be addressed, and versatility is not needed.

[Sydney]

The Meyer example points out the problems with "one size fits all" solutions.

Correct those cabs were designed for a specific application: long throw for clustering.
A JBL SRX 712M is a floor monitor ( advertised 90 x 50 dispersion, HF section only ). As a floor monitor it wasn't really designed for crossing firing or splaying and a less than ideal design to base analysis and draw sweeping conclusion. This doesn't mean that both practices aren't used on performance stages with the inherent issues.
Modern speaker and line modules often employ lens or diffraction grating and use signal processing to mitigate pattern interference issues. This sets them apart from a simple physical cross-firing.