Old Sound Man,

YES, SIMON!

I run sound for a few local bands who play mainly in smaller clubs and have a question about speaker placement. My setup uses two high/mid cabinets (each have two 8’s and a tweeter) and an 18" powered sub on each side of the band. I made a pole mount adapter that lets me mount both high/mid cabinets next to each other just above ear level. In general, it sounds pretty good for a small system, and doesn't take a gorilla to move it, but I just read an article about Rat Sound's Microwedges that has me thinking.

In the article, it said if you are using more than one wedge for a performer, don't put the same sound into them all, in order to avoid comb filtering caused by the sound arriving at the performers’ ears at slightly different times. The article recommended putting instruments into one and vocals into another, for example. If that's the case, listeners who are relatively near my main speakers, both of which are producing the same sound, are going to be experiencing this as well.

I thought about splitting the sounds as the article recommends, but as the listener gets further away from the speakers, the comb filtering is going to become less and less so I'm not sure if it's worth the cost of another amp and cables. Can you give me an idea at what type of distances this is going to be an issue? If it's only a problem within a couple of feet of the speakers, then I'm going to forget I asked this question and make myself some more coffee. But if it's an issue for, say, 20 feet, where the dance floor typically is, then I might plunk down some money for another amp. Any thoughts?

YES, SIMON, I HAVE GOT SOME THOUGHTS. THE SHORT ANSWER IS THAT WHAT THEY ARE REFERRING TO IS A MONITOR TECHNIQUE, WHICH IS NOT PRACTICED IN ANY HOUSE SYSTEMS I HAVE EVER HEARD OF, EXCEPT FOR THE GRATEFUL DEAD WALL OF SOUND THIRTY YEARS AGO, WITH SEPARATE CABINETS FOR EACH INSTRUMENT AND SINGER. I DO NOT RECOMMEND CONSUMING MASS QUANTITIES OF ILLEGAL SUBSTANCES THE WAY THOSE GUYS DID BACK THEN.

BUT, LET ME EXPLAIN TO THE PEOPLE AT HOME THAT I ASKED YOU PRIVATELY JUST WHERE YOU READ WHAT YOU WERE ASKING ABOUT. YOU RESPONDED THAT YOU READ IT ON THE MICROWEDGE SITE. WELL, AS YOU MAY KNOW, MR. DAVE RAT, WHO DESIGNED THE MICROWEDGE, ALONG WITH THE FINE FOLKS AT RADIAN, WHO MANUFACTURE IT FOR MASS CONSUMPTION (THIS DOES NOT CONSTITUTE AN ENDORSEMENT OF RADIAN OR THE MICROWEDGE, BY THE WAY …) ANYWAY THE RAT MAN HAS BEEN KNOWN TO CONTRIBUTE SOME VERY FINE PIECES OF AUDIO ADVICE TO PROSOUNDWEB.COM, THE VERY SAME PEOPLE WHO PAY ME TWENTY BUCKS AND PACK OF SMOKES FOR EACH OF THESE COLUMNS I WRITE.

SO I WENT RIGHT TO THE RAT’S MOUTH, AND PREVAILED UPON THE DAVESTER (WHOM I HAVE NEVER MET IN MY LIFE, BUT SEEMS LIKE A DECENT DUDE) TO GIVE YOU AN ANSWER TO YOUR QUESTION! YOU ALSO ASKED A FOLLOW-UP QUESTION, AND RAT-O-MUNDO IS SO GENEROUS HE ANSWERED THAT ONE TOO!!

HERE IS DAVE’S FIRST RESPONSE, NOW LEAVE HIM ALONE!

THE INFO ON THE MICROWEDGE PAGE IS REFERRING TO "TWO MICROWEDGES PLACED SO CLOSE THAT THEY ARE TOUCHING OR NEARLY TOUCHING." PUTTING A FEW FEET BETWEEN THEM, OR THE EQUIVALENT OF A PHANTOM MICROWEDGE, IS ENOUGH DISTANCE FOR MOST APPLICATIONS. THE MICROWEDGES BEING SO COMPACT AND COAXIAL ALLOWS YOU LOCATE THE SPEAKERS MUCH CLOSER TOGETHER THAN CONVENTIONAL WEDGES. PAYING ATTENTION TO THE INTERACTION OF VARIOUS SOUND SOURCES IS VERY IMPORTANT, WHILE THE EFFECT THEY HAVE ON EACH OTHER IS GREATLY REDUCED AS THE DISTANCE BETWEEN THEM IS INCREASED OR IF THEY ARE POINTED IN DIFFERING DIRECTIONS.

I’M NOT SURE WHAT CO-AXIAL MEANS, SIMON, I THINK IT IS WHEN RON WOOD AND KEITH RICHARDS ARE SO WASTED THAT THEY ARE LEANING AGAINST ONE ANOTHER ONSTAGE, PLAYING THEIR AXES, AND BOTH LAUGHING SO HARD AT THE THOUSANDS OF LEMMINGS THAT PAY TO SEE THEM IN THEIR OLD AGE, THAT THEY CAN BARELY STAND UP. IT’S SORT OF LIKE CO-DEPENDENT, OR CO-CONSPIRATOR. BUT YOU WOULDN’T LEAVE DAVE RAT ALONE, WOULD YOU?

I read the article on www.microwedge.com/setup.htm, but they've changed the wording a bit since I read it. It now says split the sources to increase vocal intelligibility, rather than the previous comb filtering statement.

There is another statement on the same page about two monitors side-by-side starting to act like a line array and reducing coverage angles that I'm not quite following. Can you explain a line array and how putting speakers side by side changes their coverage?

WHEN TWO OR MORE SOURCES ARE SIDE BY SIDE (HORIZONTALLY), IN CLOSE PROXIMITY, THERE IS SIGNIFICANT "OFF AXIS" INTERFERENCE IN THE HORIZONTAL DOMAIN DUE TO THE OFFSET IN DISTANCES TO THE SOURCES. THEREFORE CAUSING CANCELLATION AT VARYING FREQUENCIES, AND THEREFORE REDUCING THE OVERALL VOLUME OFF TO THE SIDES. THE SAME APPLIES VERTICALLY OR DIAGONALLY OR WHATEVER OTHER AXIS. "ON AXIS" OR ANY OTHER POSITION WHERE SOURCES ARE EQUIDISTANT FROM THE LISTENING POSITION, THERE IS MINIMAL INTERFERENCE AND MAXIMUM COUPLING, THEREFORE RESULTING IN AN INCREASE IN LEVEL.

WHEN TWO SOURCES HAVE AN INCREASED PHYSICAL DISTANCE SEPARATING THEM, THE COVERAGE AREA IS INCREASED, IF WHEN YOU GET "OFF AXIS" FROM ONE SOURCE, YOU ARE APPROACHING "ON AXIS" FOR ANOTHER SOURCE. THE INCREASED DISTANCE FROM THE FURTHER SOURCE ALSO MEANS THAT THE FURTHER SOURCE IS LOWER IN VOLUME AND THEREFORE CAUSES LESS INTERFERENCE WITH THE NEARER SOURCE. THE OFF AXIS INTERFERENCE IS, OF COURSE, FREQUENCY AND DISTANT DEPENDANT. ALL IN ALL, WHEN TWO HF SOURCES ARE IN VERY CLOSE IN PROXIMITY AND POINTED IN THE SAME RELATIVE DIRECTION, THE OPTIMUM LISTENING AREA WHERE BOTH SOURCES ARE NEARLY THE SAME IN VOLUME AND EQUIDISTANT, IS RELATIVELY SMALL.

MAKES SENSE TO ME! AND I AM JUST AN OLD KNUCKLEHEAD, ACCORDING TO SOME OF THE IDJITS ON THE LAB! I’M SURE THEY KNEW ALL THIS WHEN THEY WERE SPITTING UP ON A FLANNEL BLANKIE ON THEIR MOMMY’S SHOULDER!

AREN’T YOU PROUD THAT DAVE RAT TOOK THE TIME TO HELP YOU, SOUNDMAN? NOW STAND UP STRAIGHT AND GO OUT THERE AND MIX A SHOW!

LUV –

- THE OLD SOUNDMAN

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