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Why does putting the cab on the floor make it sound so huge?

Flux Jetson

Flux Jetson

Guest
May 3, 2012
2,084
99
Colorado River Basin, Arizona
#1
I could have worded that better but I needed more words.

I have these two cabs ...

Carvin210andCarvin410-1-1.jpg


Which ever one I put on the bottom produces a LOT more perceived low end, and even seems to produce more SPL. Notice I used the words "perceived" and "seems", ok?

So what is up with that?

Either one sounds pretty anemic when it's the one on top and solo'd.

And while I got ya ... why is the 210 just plain old louder? A lot. I use a Mackie FR1400i power amp in ~stereo~ mode, both cabs are 4ohm. No matter which channel I put the 2x10 on, I have to put the level knobs roughly "3 hours" apart to get them to be fairly even loudness levels. By "3 hours" I mean if I put the 210 at 9 o'clock on the output level knob, I must put the 410 at 12 o'clock. It's like this no matter which channels I run the cabs on, I've swapped speaker cables back and forth, swapped their channels, and so on. This is true even if both cabs are on the floor, or the 210 is on top of the 410, or the 410 is on top of the 210 ... whatever.

Does it have something to do with the 410 being totally sealed and the 210 being shelf ported (allowing more air to move out of those large shelf ports)?

The sensitivity specs say the 410 should be about 4db louder, but it sure isn't. All four speakers are operating, btw.

Just curious.

My main question is why putting a bass cab on the floor makes it so much more massive sounding.

Thanks for tolerating "speaker 101" questions.

:)
 
#2
When a cabinet is placed at a room boundary, be it a wall or floor, you get two effects. One is that you eliminate cancellation that occurs when a wave reflected off the floor arrive back out of phase withe the direct wave. In addition, every room has a number of natural resonances, and the nodes of these resonances occur at room boundaries. Thus placement near boundaries makes it easier for the speaker to excite the resonances.
 
#3
mje said:
When a cabinet is placed at a room boundary, be it a wall or floor, you get two effects. One is that you eliminate cancellation that occurs when a wave reflected off the floor arrive back out of phase withe the direct wave. In addition, every room has a number of natural resonances, and the nodes of these resonances occur at room boundaries. Thus placement near boundaries makes it easier for the speaker to excite the resonances.
Click to expand...

+1......Acoustic coupling.

Using boundries to work for you instead of against you.

Although, in particularly boomy rooms, you can use that same science to purposely cause some cancellations and reduce woof/improve clarity, etc.
 
#5
The carpet helps dampen some treble and upper midrange reflections. With a loose wood floor, like the crappy stages some of us play on, the output of the speaker excites the floors resonance and makes it vibrate, something like a giant drum head. The rig vibrates in turn because it's sitting on the vibrating floor.


Link to chart of wavelength distances/boundry cancellations and enhancements, etc. Rule of thumb for subwoofers is to place them less than 2 ft. or more than 8ft. from boundries to avoid the 1/4 wavelength cancellations in the 40hz to 100hz bandwidth they'll be playing.

[Invalid or Expired Link Removed]


Link to Bill Fitzmaurice's subwoofer placement instruction page. These same rules apply for the low frequencies coming from a bass rig as well as conventional subwoofers. You just don't face your nass rig into the corner because it plays mids and highs as well.

http://billfitzmaurice.info/forum/viewtopic.php?f=10&t=398


Lots of good info in his Educational links here...


http://billfitzmaurice.info/forum/viewforum.php?f=18
 
#6
Yea, carpet acts kinda like an absorber, but only for "higher" frequencies, so long as it is not massively thick. It won't "slow" down any bass soundwaves because the wavelengths of bass frequencies are very long in relation to the thickness of the carpet. This is why bass sounds can completely traverse the backseat of a car that has a subwoofer in the trunk---the wavelengths are so long, that foam padding in seats doesn't stand a chance.

A wooden floor above ground can also reinforce the sound if it is sturdy enough. Basically boundary loading like a cab on the floor, on the floor and against the wall, or against 3 walls in a corner, increase the SPL at the listener position because the sound is radiating more "narrowly". Think about a standard incandescent light bulb used in older flashlights. With a given voltage on it, it will only emit so much light (in all directions). But place this bulb at the focus of a parabolic reflector (such as that in a flashlight), and now you have a lot more light, but only in one concentrated spot. So it's brighter at the at spot, even though the total light being radiated is still the same as before it was in a parabolic reflector.
 
#7
I've often daydreamed about a ported bass cab that had one driver facing straight down, about a foot from a base board, with four open sides where the air can radiate in all directions. Then do the same thing with another driver facing straight up, with another board spaced about 8 inches/a foot where the sound hits it and radiates in all directions. The upper and lower cabs are sealed off from one another.

It seems as though something like that (properly tuned) would eliminate focal hot spots (or unfocused dull spots), and even the drummer would hear what the audience hears.
 
#10
Flux Jetson said:
I've often daydreamed about a ported bass cab that had one driver facing straight down, about a foot from a base board, with four open sides where the air can radiate in all directions. Then do the same thing with another driver facing straight up, with another board spaced about 8 inches/a foot where the sound hits it and radiates in all directions. The upper and lower cabs are sealed off from one another.

It seems as though something like that (properly tuned) would eliminate focal hot spots (or unfocused dull spots), and even the drummer would hear what the audience hears.
Click to expand...

It would operate as a sort of bandpass, cancelling out some highs by firing imto the boumdries. Subwoofers can face any direction as they radiate in all directions anyway. Mids and highs must face the listener. That's the dispersion stuff we talk about in here.

One exception to that is cardoid subs. They use those cancellations and enhancements to help "steer" the sound toward the listener.
 
#12
will33 said:
It would operate as a sort of bandpass, cancelling out some highs by firing imto the boumdries. Subwoofers can face any direction as they radiate in all directions anyway. Mids and highs must face the listener. That's the dispersion stuff we talk about in here.

One exception to that is cardoid subs. They use those cancellations and enhancements to help "steer" the sound toward the listener.
Click to expand...
A bandpass would be ok for the 1khz to 2-5khz range as far as I'm concerned. (Sometimes I actually use a wah pedal in parallel with my clean tone to produce a strong focused vocal tone, I use synth modules to route the signals in parallel then mix them to suit me). I know when I stand right next to my cabs, where my body is actually right next to the cab, the 1khz to 2khz +/- range is really focused well, and of course the lows find me anywhere I stand. So there's this great, super defined scoop going on. Tight lows, and very defined BPF with a bandwidth of roughly 1khz to about 2khz. I recently bought a software realtime analyzer, I've been wanting to use it to get a general idea about what exactly is going on when I stand next to the cab. I wanted to get a reading out in front of the cabs, about ten feet out directly aligned with the voice coils, then a camparative reading right next to the cab. I know there's all of these variables (mic calibrations etc) but I'd at least get a relative difference reading between out in front of it and right next to it. I'd learn something at least. It wouldn't be anything to compare to anything outside of that test environment but it would provide a relative difference at least.

I like really strong "voice" for my bass most of the time (what I call "the bronze sound") and standing directly next to my cab as if the cab and I were two people standing next to each other and facing the same direction there is a wonderful BPF effect going on. That was what made me think of the speaker facing straight up with a ~deflector~ board above it and four open sides. Like a 1x10 or something in a ported cab facing upward, with a thick board at a ?proper? distance above it.

Just imagining things.
 
#14
Others know more about this than me but...

I always thought it was about low frequencies being less directional than higher frequencies. This is why you can always hear bass booming from a club or bar from some distance even though it isn't that loud.

If that's right then it is more about the cab being low down than the fact it is on the floor. Lie down in front of the lower cab and it might not sound as boomy.

Feel free to contradict me if that is just plain wrong.
 
#16
Flux Jetson said:
A bandpass would be ok for the 1khz to 2-5khz range as far as I'm concerned. (Sometimes I actually use a wah pedal in parallel with my clean tone to produce a strong focused vocal tone, I use synth modules to route the signals in parallel then mix them to suit me). I know when I stand right next to my cabs, where my body is actually right next to the cab, the 1khz to 2khz +/- range is really focused well, and of course the lows find me anywhere I stand. So there's this great, super defined scoop going on. Tight lows, and very defined BPF with a bandwidth of roughly 1khz to about 2khz. I recently bought a software realtime analyzer, I've been wanting to use it to get a general idea about what exactly is going on when I stand next to the cab. I wanted to get a reading out in front of the cabs, about ten feet out directly aligned with the voice coils, then a camparative reading right next to the cab. I know there's all of these variables (mic calibrations etc) but I'd at least get a relative difference reading between out in front of it and right next to it. I'd learn something at least. It wouldn't be anything to compare to anything outside of that test environment but it would provide a relative difference at least.

I like really strong "voice" for my bass most of the time (what I call "the bronze sound") and standing directly next to my cab as if the cab and I were two people standing next to each other and facing the same direction there is a wonderful BPF effect going on. That was what made me think of the speaker facing straight up with a ~deflector~ board above it and four open sides. Like a 1x10 or something in a ported cab facing upward, with a thick board at a ?proper? distance above it.

Just imagining things.
Click to expand...


With some 'cipherin' and experimentation, you could get just ehat you're looking for. That's what some of these newer cabs like Glasstones and Xsonics do. The downfiring woofers bass and lowmids add to the overall oitput, while the uppermids/highs are pretty much just heard from the forward facing woofer/tweeter. The old Acoustic 408 I think?...415 cabs used a similair concept on a larger scale, with 2 forward facing drivers and 2 more firing up and down.

Good on ya for gearing up with the test mic stuff, I'll be doimg the same thing in a couple months. That'll really tell you what's going in and you can then identify just what parts of the sound you want/don't want to hear in relation to the level of the rest of the bandwidth and manopulate your drivers to achieve that. Good ol' trial-and-error works too, but being able to measure and quantify what's happening really helps.

You could start experimenting just by using 2 separate cabs and a couple boards. Fire one into the floor, one forward or upward and move the boards around.
 
#18
CL400Peavey said:
I think you would be amazed at what you lack if you filtered out above 1,000 hz.
Click to expand...

I would agree. You need some reproduction up there, though it doesn't have to be as hot as the rest of the bandwidth depending on how you're trying to voice the cab.

You also have to allow for a room full of bodies damping down the uppermids and highs.

1khz is pretty low though. Flatwounds with the tone rolled off still has some sort of content higher than that, just not as much in comparison to the lower sounds. I have some old woofers that don't do much of anything above guesstimating 2khz and that's about as "warm" as I'd care to get. Any less would be too muddy and undefined, even for flatwound blues or reggae.

IMO, of course.
 

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