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Re: Head to cab connections
6/12/2012 7:01 PM
Gar Whitenton (5737) wrote:
absolutely. There are, as I am sure Mo will agree, some things to take into account. First and foremost is phasing. If the cabs are out of phase, they will tend to cancel each other out. Another is throw. Let's discuss the 3 main types of cab designs. First is called acoustic suspension. This is a sealed cab, no ports. Second, and usually most efficient, it called bass reflex, or ported design. Most bass cabs are this type. These are the cabs that are sealed but have one or more ports, usually in front. Lastly is the folded horn design. The are the cabs the (usually) you cannot see the driver. Some you can see the driver, and they usually have a large square opening beneith the speaker. Ok, each of these cabs will differ in efficiency, decibel to input ratio, and throw. Throw is basically out far out front (or behind) the cab the sound waves come together to produce the best sound, tones, and volume. The throw of cabs typically depends a lot on the design, acoustic suspension being the shortest, bass reflex being next, and folded horn being the longest throw. Throw also has a lot to do with the size and design of the actual driver. A 15" usually has a greater throw than a 10" driver, PLUS two 15" drivers from different manufacturers can have different throws. This is because of variances in voice coil diameter, cone material and thickness, efficiency, even frame design and magnet weight/strength. Anyway, this is why at the very least the elements inside a single cab should be matched up.
So, why does are rig sound "fuller" when using two of the same cabs? Because the throw is the same for both cabs, therefore wherever you stand, you are getting roughly twice the sound pressure level. This is why Mo says it is a no no to mix and match cabs. And I completely agree.
But...all this is assuming a few things. 1: You intend to always stack your rig in the Marshall fashion, and 2: you do not own a decibel meter.
When I was actually performing on a regular basis, I would first "test the room" with the meter and an output tone of A 440. I would generally set my 18" folded horns (2) as far back as possible. These provide a deep bass (very deep) that would rattle beers off table and blow out a match at 10 feet. I would move my sealed Altecs, 2-15's in each x 2 cabs, about halfway up the stage on either side facing more in than towards the audiance. Lastly I would place my single cab with 2-15's, a bass reflex design, pretty much right behind me pointed straight out. This setup varied with the actual room. Then of course there was whatever the soundman did through the PA.
Anyway, the point is this: It ain't carved in stone. Depending on the sound you want, you might find yourself mixing up any number of cabs. The simple solution for solid clear bass, follow Mo's advice and do NOT mix and match. To taylor your sound, experiment. If you look at my AB homepage you can see part of the rig I used to run through, manely one of the Altec stacks.