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**The Official Comb Filtering Thread**

tallboybass

tallboybass

Supporting Member
Feb 25, 2003
4,573
1,163
69
Tulsa, Oklahoma
#1
Man, I love the discussion of comb filtering as much as the next guy and thought we could keep it contained here instead of "filtering" into the other threads. There have been fascinating ideas batted about and it would be awesome to continue that talk here. Jimmy's vertical cab stacking thread certainly has a lot of good info in it, as well as the Bergantino Neo thread. What do you think?

Alan
 
#3
tallboybass said:
Man, I love the discussion of comb filtering as much as the next guy and thought we could keep it contained here instead of "filtering" into the other threads. There have been fascinating ideas batted about and it would be awesome to continue that talk here. Jimmy's vertical cab stacking thread certainly has a lot of good info in it, as well as the Bergantino Neo thread. What do you think?

Alan
Click to expand...
Most of what matters is explained here:
[Invalid or Expired Link Removed]

What is said there applies specifically to low frequencies and cabs that are separated. But the same physics apply to higher frequencies (above 1kHz roughly) with drivers that are mounted side by side. And the same simple rule applies to both situations: Don't. Don't separate low frequency sources, and don't mount high-frequency sources side by side.
 
#4
Thanks Bill, that's a very informative article.

Here's a visualization of CF that helped me understand a little more.
 

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#7
My new favorite anti-comb-filtering rig......Genz Shuttle 6.0-12T combo stacked on a vertical UL210. It sounds amazingly great! (heaviest component in rig=38 lbs., total weight=69.5 lbs.) The Shuttle seems to respond well to cabs with lots of booty. The two cabs are the same width.....they look to be designed to work together!:bassist:

I was wondering though, because of the slightly staggered drivers in the UL210, would there still be some CF?

Thanks, Alan
 
#8
There is comb filtering when speakers are stacked vertically as well, it's in the opposite plane. There are additional issues to consider when stacking vertically, including the height of the second or higher cabinet off the floor combining with the reflaction from the floor. This is also an issue when placing a single driver an appreciable distance above the floor.

Fortunately, the (negative) effects are pretty minimal in practice.
 
#9
billfitzmaurice said:
Most of what matters is explained here:
[Invalid or Expired Link Removed]

What is said there applies specifically to low frequencies and cabs that are separated. But the same physics apply to higher frequencies (above 1kHz roughly) with drivers that are mounted side by side. And the same simple rule applies to both situations: Don't. Don't separate low frequency sources, and don't mount high-frequency sources side by side.
Click to expand...

How do common guitar cabs get away with this?
 
#10
SwamiRob said:
How do common guitar cabs get away with this?
Click to expand...

On paper, they don't. However, similar to 410 configurations, I don't really notice the off axis response issues that are talked about (primarily in the audiophile stereo literature), at least in the specific situation of amplifying a bass guitar or electric guitar.

I've probably played a 1000 gigs with guitarists using Twin Reverb amps with side by side 12's, and they sound totally even across the stage and across the room when I'm in the audience.

I've also done many A/B's 'on the gig' with various 210 cabs...placing them in vertical and horizontal orientation. Besides a slight perceived increase in absolute low end in some cases when a 210 is placed horizontally (is this due to floor coupling or possibly a reduction in off axis upper mid response due to comb filtering that made the cabs sound 'more bassy'?... I have no idea... it was very subtle), I never really noticed a significant difference across the stage or out in front of the cab. I'm sure it was there, but as a few have pointed out, this sort of 'orientation' effect was overwhelmed by the other acoustical impacts of room, player, amp/cab match, etc., etc., etc., etc.

As Agedhorse points out, there are many, many subtle issues in cabinet design, and each configuration has it's slight positives and negatives. It's better IMO and IME to use your ears when choosing a cabinet or any piece of gear:)
 
#11
KJung said:
I've probably played a 1000 gigs with guitarists using Twin Reverb amps with side by side 12's, and they sound totally even across the stage and across the room when I'm in the audience.
Click to expand...

I'm sorry but I simply don't believe you're listening Ken! I have tested this theory numerous times with guitar amps and my bandmates consistently notice the 2x12" combos sounding better on their side with the speakers vertically aligned. I have also found that guitar 4x12" cabs are so directional that you can be unable to hear them across the other side of the stage but out in the room if you're in line with them they can be so loud they totally screw up the mix.

Alex
 
#12
alexclaber said:
I'm sorry but I simply don't believe you're listening Ken! I have tested this theory numerous times with guitar amps and my bandmates consistently notice the 2x12" combos sounding better on their side with the speakers vertically aligned. I have also found that guitar 4x12" cabs are so directional that you can be unable to hear them across the other side of the stage but out in the room if you're in line with them they can be so loud they totally screw up the mix.

Alex
Click to expand...

I hear a lot, but that I don't hear:) I haven't played with a 4x12 guitar amp in 20 years, so can't comment there.
 
#14
KJung said:
I hear a lot, but that I don't hear:) I haven't played with a 4x12 guitar amp in 20 years, so can't comment there.
Click to expand...

Have you tried turning a 2x12" combo on its side and comparing vs the normal position? Obviously if it's miked and coming back through the monitors then it won't be so obvious but if the guitar amp is the sole source of sound the difference between horizontal and vertical is huge. Even my drummer notices! ;)

Alex
 
#15
alexclaber said:
I'm sorry but I simply don't believe you're listening Ken! I have tested this theory numerous times with guitar amps and my bandmates consistently notice the 2x12" combos sounding better on their side with the speakers vertically aligned. I have also found that guitar 4x12" cabs are so directional that you can be unable to hear them across the other side of the stage but out in the room if you're in line with them they can be so loud they totally screw up the mix.

Alex
Click to expand...


I agree...especially in an open space (outdoors). I would venture to guess that this is because there is no room pressurization or reflection from walls or what have you. A 4x12 guitar cab can be deafening directly in front of the cab, but completely drowned out of the mix a few feet over.
 
#16
alexclaber said:
Have you tried turning a 2x12" combo on its side and comparing vs the normal position? Obviously if it's miked and coming back through the monitors then it won't be so obvious but if the guitar amp is the sole source of sound the difference between horizontal and vertical is huge. Even my drummer notices! ;)

Alex
Click to expand...

I have not, only 210 bass cabs. I would guess that guitar cabs would be a little more sensitive to this, but again, it's pretty much a non issue for me personally (i.e., the effect, which of course is real, is a minor issue relative to the million other things that impacts dispersion, tone, volume, performance, etc., etc., etc.).

If you find cabs that are able to be vertically oriented, of course, no problem there. If you find a side by side oriented cab that you love the sound of, IMO no problem there either, taking everything into account IMO.
 
#17
KJung said:
I have not, only 210 bass cabs. I would guess that guitar cabs would be a little more sensitive to this...
Click to expand...

Not a little more sensitive, it makes a HUGE difference due to the far greater midrange and treble content of typical guitar tone.

When I turned up for soundcheck last night my guitarist had his 2x12" combo turned on its side and raised up on a beer crate. Magic!

Alex
 
#18
NoGraveConcern said:
I agree...especially in an open space (outdoors). I would venture to guess that this is because there is no room pressurization or reflection from walls or what have you. A 4x12 guitar cab can be deafening directly in front of the cab, but completely drowned out of the mix a few feet over.
Click to expand...

Indeed - room reflections can help solve the disastrous off-axis tone to some degree but outdoors it is painfully obvious.

The same is true with power alleys due to separated subs - indoors the boundary reflections obscure the issue somewhat but outside you run into numerous obvious 24dB notches in the bass response.

Alex
 
#19
This might not be appropriate to talk about in this thread, and maybe I've missed it, but how do you avoid this in a PA context. I run sound from the stage with my band, and I am constantly running out of ideas on how to bring the kick drum up in the mix. And I definitely do notice the off axis sound difference. Right about 10-25 feet out from the speakers is the 'sweet spot,' but if I stand directly in front of either speaker, there is a rather pronounced difference - way less low end.
 

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