Combing-Screw Up Question

SurferJoe46 · #1 06-10-2011, 09:58 AM

If one were to take four 15-inch individual cabs and run them in the position most like a 415, (eg: stacked in a quad-position) would it be the same or almost the same or worse than a 415 single cab?

Thinking that one of the reasons for problems in individual cabs might be that the drivers would be more than the diameter of the drivers apart, if the cabs were small enough to get the drivers into the same relative position as in a 415, would that be good enough?

It SEEMS that the biggest problem with combing is that the waves coming off the individual drivers would not be supporting each other if they are too far apart, and that their pulses would then tear into each other and destroy the sound. Right?

Is that a realistic thought?

billfitzmaurice · #2 06-10-2011, 10:04 AM

Quote:

Originally Posted by SurferJoe46

If one were to take four 15-inch individual cabs and run them in the position most like a 415, (eg: stacked in a quad-position) would it be the same or almost the same or worse than a 415 single cab?

It will be worse, as the drivers won't be as close together as in a single cab. Combing will occur above where the driver centers are more than 1 wavelength apart. Even if mounted frame to frame that's 900 Hz. Worse, the mids will beam above where the total driver cone edge to edge width is more than 1 wavelength; frame to frame that's going to be above 500Hz. There's nothing to be gained by having drivers or cabs side by side, and a lot to be lost.

SurferJoe46 · #3 06-10-2011, 10:17 AM

Aha! I see there's a fly in the juice then. Is this more true or more obvious in the choice of the 15-inch drivers I chose?

I can see certain frequency problems as you noted the centers of the drivers present a problem even when you try to mount the frames physically next to each other.

Would the frequency problem them be less if the drivers were 10-inchers or even 8-inchers?

Realistically then, it appears that no two 15-inch drivers can even be a good choice for multiple drivers-in-a-single-cab.

This seems to present an argument for using smaller diameter drivers in a multi-driver cab.

will33 · #4 06-10-2011, 10:28 AM

Smaller drivers means the distances will be shorter and the problems will start a little higher in frequency but the same problems are still there. Vertical is always best. It's a good thing to minimize vertical dispersion as nobody's ears are on the ceiling or the floor.

billfitzmaurice · #5 06-10-2011, 10:32 AM

Quote:

Originally Posted by SurferJoe46

Realistically then, it appears that no two 15-inch drivers can even be a good choice for multiple drivers-in-a-single-cab.

No two drivers of any size should ever be placed side by side unless they are low-passed below the frequency where beaming will begin, let alone combing.

Blankandson · #6 06-11-2011, 08:02 PM

So, the people who are getting a combo with, let's say, 1X15, then buying a second identical combo when they need the extra sound; they can either set them side-by-side, one atop the other, or place them a distance apart on the stage. How would the average joe ever know if he's hurting his sound or getting what's he's paid for?

billfitzmaurice · #7 06-11-2011, 08:04 PM

Quote:

Originally Posted by Blankandson

So, the people who are getting a combo with, let's say, 1X15, then buying a second identical combo when they need the extra sound; they can either set them side-by-side, one atop the other, or place them a distance apart on the stage.

They should only be placed vertically. Never side by side, never separated.

Blankandson · #8 06-13-2011, 07:54 PM

That will work with the GK MB115 if they are set on their sides, one atop the other. The way the controls are set in the top, you couldn't get to the controls on the bottom combo if they were just set atop each other. Unless you devised a frame to lift the top one up a few inches.

JimmyM · #9 06-13-2011, 08:38 PM

Quote:

Originally Posted by Blankandson

So, the people who are getting a combo with, let's say, 1X15, then buying a second identical combo when they need the extra sound; they can either set them side-by-side, one atop the other, or place them a distance apart on the stage. How would the average joe ever know if he's hurting his sound or getting what's he's paid for?

By learning a little something about how audio works.

rpsands · #10 06-13-2011, 09:57 PM

If you're going to set them side by side you can cross-fire them. You can also turn one on top 90 degrees for more coverage if you have a two stack but aren't getting enough coverage. Not ideal, but better than setting them side by side.

Fun stuff

Having fooled around with various stackings of two cabs I actually tend to like the 90 degrees on top one better than the vertical line, in situations where I have to monitor both for myself and the drummer, say. (top one toward me, bottom toward the drummer, fwiw). Not that I ever use two cabs anymore

SurferJoe46 · #11 06-13-2011, 10:10 PM

I need some closure on this right about here.

If side-by-side cabs are not the right thing to do because of wave collisions and distortions, then why do cab makers build 4x10, 4x8, 4x12 or 4x15 cabs with the drivers in a square pattern if being side by side is so bad?

Seems to me that no decent cab maker would do less than 4 of any driver in a straight vertical line and instruct the user to put it 4-tall. (EG: 2x10 cabs stacked end on end?)

rpsands · #12 06-13-2011, 10:35 PM

Because back in the day it took 8 drivers in a box to get any decent volume for bass and the only reasonably sized way to do that was to stick the second line side by side.

So now people are accustomed to that look and since cabinet manufacturers like money they sell what people want.

Rule #1 with bass cabinets: It must look cool.

seamonkey · #13 06-13-2011, 10:40 PM

that is the question of ages.
And it's all about looks over function.

Russell L · #14 06-14-2011, 06:16 AM

I read an article somewhere that said comb filtering isn't noticed by our brain. Something to do with how it ignores the waves that get there late. Something like that. Anyone wanna comment on that? I'm just trying to understand.

billfitzmaurice · #15 06-14-2011, 06:20 AM

Quote:

Originally Posted by Russell L

I read an article somewhere that said comb filtering isn't noticed by our brain. Something to do with how it ignores the waves that get there late.

That's not comb filtering, that's precedence effect. The two are not related.

SurferJoe46 · #16 06-14-2011, 07:17 AM

Then by extension of that logic, ALL square quad-patterned multi-driver cabs are built wrong and one should never have any drivers side by side even in the same cab.

If one wants to run 8 x 10, then the stack will be a single driver above a single driver above another single driver until it's ten drivers tall.

That's over 80-inches high just in drivers alone.

Russell L · #17 06-14-2011, 07:59 AM

Quote:

Originally Posted by billfitzmaurice

That's not comb filtering, that's precedence effect. The two are not related.

Thanks, Bill. I don't understand all this yet. The article was specifically about comb filtering, though. Maybe I misunderstood the guy. I believe you.