Pros and cons of stacking...

[mikewalker]

Thanks for all the feedback here. I have definitely decided not to dive in and order an amp stand... gonna try "boxing" this weekend!

 

[Zbysek]

Stack them on the floor, especially since you are playing in loud rooms without PA support.

If you want to have HF content closer to your ears, get EAR BOX from Phil Jones Bass. That's what I am using in similar situations...

[Invalid or Expired Link Removed]

 

[Downunderwonder]

A black rayon table cloth from a catering supplies store makes the beer crate you borrow from the bar look kosher.

You could even start with the bottom cab unplugged if you have FOH support. The sound guy might buy you a beer.

 

[Zbysek]

You could even start with the bottom cab unplugged if you have FOH support.

That's what I do too. I plug the bottom cab only if need it...

 

[Rick James]

Bass frequencies have wavelengths in air around a meter +/-.

A wavelength at 343 Hz is a meter. At 100Hz it's about 3.4 meters, at 50 Hz 6.8 meters.

Transfer from the drivers to the stage plate actually increases as the cab is elevated above the stage plate for the first 1/4 wavelength

That's would defy at least two laws of physics, the inverse square rule being one. The reason it changes at 1/4 wavelength is that's where the total distance traveled to the floor and back is 1/2 wavelength, so the reflected wave is 180 degrees out of phase with the original wave, resulting in a cancellation at and near that frequency, but only at and near that frequency. The cancellation frequency, known as floor bounce, also shifts depending on the position of the listener.

You could even start with the bottom cab unplugged if you have FOH support.

If you do that the unused cab will act as a bass trap.

 

[agedhorse]

It's all about tradeoffs, but within a couple of feet the boundary effect distance becomes pretty insignificant compared to the potential benefit of hearing the cabinets better.

 

[AngelCrusher]

Here's the issue, I learned from a lot of gigs and touring.

Over thinking this stuff is not worth it. Why? every room will be different. You will get dialed in one night and then be chasing the dragon the next.

My tech could have stacked my cabs like dominos and toppled them over randomly throughout the gig and I would not have cared. Why? I use in ears. And I believe the end game of what you are looking for will probably involve them as well.

 

[fig]

The box with "the beer effect" gets my vote!

Beer boxes? No, man, let's take it to the next level.

Seriously, I need my cabs off the ground, so I voted "Stacked on a box". I'm 6ft 2in and on a short stage, it's kinda mandatory. Otherwise, I get too loud as the output is blowing at my legs and butt, plus I don't hear the articulation as well. Short and/or tight stages are the majority of my gigs these days. "Stacked on the floor" is out for me LOL.

I've done the 'stacked w/stand" on occasion, just 'cause it looked cool. And it works fine to get the sound to my ears also.

Optimal performance and efficiency considerations go out the window when I'm playing small stages. And no matter the verifiable science behind this stuff, I'm sure my big body right in front of whatever configuration I'm using is wreaking havoc with the optimal performance LOL. The reality is I have to dial something in, make sure I can hear it well, and play in my small, non-ideal area.

Over thinking this stuff is not worth it. Why? every room will be different. You will get dialed in one night and then be chasing the dragon the next.

Exactly.

 

[Honkey tonk]

Did not vote
Did not see the option for using a screwgun with screws to screw the cab to the floor

Or high pass the lower cab

 

[Downunderwonder]

If you do that the unused cab will act as a bass trap

way to let the cat out of bag

The sound guy might buy you a beer.

 

[mapleglo]

I have my pair of 1x12's stacked on a small box I made.

I find that it helps to bring them closer to my ears so I can hear them better, and may help to de-couple them from the stage (though the riser may not be high enough).

 

[bucephylus]

A wavelength at 343 Hz is a meter. At 100Hz it's about 3.4 meters, at 50 Hz 6.8 meters.

Thanks for some exact numbers. I just gave an order of magnitude number so others could get a physical sense of the lengths involved.

That's would defy at least two laws of physics, the inverse square rule being one. The reason it changes at 1/4 wavelength is that's where the total distance traveled to the floor and back is 1/2 wavelength, so the reflected wave is 180 degrees out of phase with the original wave, resulting in a cancellation at and near that frequency, but only at and near that frequency. The cancellation frequency, known as floor bounce, also shifts depending on the position of the listener.

Also, thank you for the explanation of phase cancellation.

My measurements of the energy transfer from the cab to the stage were performed with several different mechanical de-coupling devices placed beneath the cab; and the ONLY factor that directly scaled with the energy transfer to the stage plate was the cab height above the plate. When I noticed that apparent relation, I stood on the plate while lifting the cab, and could both feel the vibration intensity in my feet scaling and see the signal on the corresponding oscilloscope amplitude from the plate sensor increase as I lifted the cab above the plate. That surprised me as well. My measurements were at 200Hz, with a projection SPL of around 95 dB. And, I’m referring to picking up the cab by a distance of about up to a half meter; roughly a beer crate. Though I guess it depends on how big your beer bottles are, eh?

At those settings, the plate response is both apparent and well behaved. I’d suggest you try it; and then we can have an interesting discussion about the physics.

 

[Wasnex]

I'm not an acoustical engineer (although I do play one on TV) and I was wondering if anyone can educate me about the "boundary effect", and how substantial that really is.

I have two identical 1-12 cabs, and would like to stack them for optimal performance and efficiency - but also keeping in mind I'd like to hear my articulation very well.

These are my three options I have been considering :

View attachment 3408304

The "stacked on the floor" potentially offers "floor boundary coupling" plus "the line array effect" - but it's not pointed anywhere near my ears... (I'd typically be positioned no more than 5 or 6 feet in front of it)

The "stacked on box" potentially offers LESS (zero?) "floor boundary coupling" plus "the line array effect" - and it's pointed somewhat closer to my ears...

The "stacked w/stand" potentially offers "floor boundary coupling" but (probably?) loses the "the line array effect" - however the top cab is pointed more towards near my ears...

All things being equal, which would be considered optimal? Are the "boundary" and "line array" effects really considerable? I'd be running about 400 WRMS through this rig. This application is for small but loud rooms, with no PA support for the bass. I've been leaning towards buying a tilt stand, but would love some opinions on this first...

I would go with stacked on a box and then wedge something under the top cab to tilt it up. You want the cabs as close together as possible. I used to run an Eden D210XLT stacked vertically on top of my rolling rack. I wedged a spare Countryman Type-85 under the front edge of the cab to tilt it back and aim it at my ears.

Boundary cancellation occurs where the distance between the driver and boundary equals approximately 1/4 wavelength. The higher you lift the cab, the lower the center frequency where the cancellation occurs. I have attached a frequency wavelength chart for your convenience.

 

[Zbysek]

Over thinking this stuff is not worth it. Why? every room will be different. You will get dialed in one night and then be chasing the dragon the next.

+1

I use in ears. And I believe the end game of what you are looking for will probably involve them as well.

I don't think this is the solution for the OP as he clearly stated there is no FOH support...

 

[Wasnex]

Here's the issue, I learned from a lot of gigs and touring.

Over thinking this stuff is not worth it. Why? every room will be different. You will get dialed in one night and then be chasing the dragon the next.

I agree, however, getting the cabs up high and aiming them directly at your ears minimizes variation from gig to gig. The idea is to increase the ratio of direct/indirect sound reaching your ears. If the speakers are on the floor aimed straight out, you don't hear the full range, direct response of the speaker because the mids and highs shoot by below your ears.

Of course you can also correct for this by standing further from the speaker, so your ears are within the dispersion pattern of the high frequencies. I have to stand about 15" in front of my Greenboy Dually to hear the higher frequencies from the cab. Unfortunately when you are standing that far away, the SPL of your direct sound drops off at the rate of 6dB for each doubling of distance, so it becomes harder to punch through any diffuse field that builds up in the low end. The more prevalent the diffuse field, the closer you need to stand to your speaker.

I normally stand about 3-4" from my rig. There were times when the acoustics were so bad that this was not close enough, but most of the time it worked well.

I think it's important to know when you can make a difference by adjusting your tone controls, and when it is a lost cause. Sometimes the best thing to do is turn down and accept that the sound is going to suck no matter what you do.

 

[Zbysek]

I agree, however, getting the cabs up high and aiming them directly at your ears minimizes variation from gig to gig. The idea is to increase the ratio of direct/indirect sound reaching your ears.

IMO, this solves only half of the problem the OP has. Yes, he will be able to hear himself better...but he still needs to carry the (loud) room with his rig as there is no FOH support...

Of course you can also correct for this by standing further from the speaker, so your ears are within the dispersion pattern of the high frequencies.

IMO, this is better approach considering the fact that there is no FOH support...

 

[Stumbo]

A box and HPF.

 

[Wisebass]

Hi guys

My measurements of the energy transfer from the cab to the stage were performed with several different mechanical de-coupling devices

I stood on the plate while lifting the cab

see the signal on the corresponding oscilloscope amplitude from the plate sensor

I have attached a frequency wavelength chart for your convenience.

I’d suggest you try it

On stage, standing on a plate, lifting a cab,

watching the oscilloscope and reading frequency charts while playing Mustang Sally…

That' s what I call a busy gig!

Sorry, I could not resist!


greetings

Wise

 

[Redbrangus]

My measurements of the energy transfer from the cab to the stage were performed with several different mechanical de-coupling devices placed beneath the cab; and the ONLY factor that directly scaled with the energy transfer to the stage plate was the cab height above the plate. When I noticed that apparent relation, I stood on the plate while lifting the cab, and could both feel the vibration intensity in my feet scaling and see the signal on the corresponding oscilloscope amplitude from the plate sensor increase as I lifted the cab above the plate. That surprised me as well. My measurements were at 200Hz, with a projection SPL of around 95 dB. And, I’m referring to picking up the cab by a distance of about up to a half meter; roughly a beer crate. Though I guess it depends on how big your beer bottles are, eh?

I found this really interesting...I hadn't given it much thought, but I guess I had always presumed that a resonant stage platform was mostly actuated by the mechanical coupling of the amp (or drum set) to the stage...your experiment indicates that it's acoustic coupling that is the culprit. That makes sense to me. And it indicates, as you seem to have confirmed, that de-coupling devices like absorbent pads under the speaker cabinet won't have much effect on the phenomenon.

But having said that, I'm also going to observe that I see a lot of folks here on TB blaming boomy, hollow stages for adverse acoustic effects that they probably don't really cause. IHMO, of course.

 

[Zbysek]

I found this really interesting...I hadn't given it much thought, but I guess I had always presumed that a resonant stage platform was mostly actuated by the mechanical coupling of the amp (or drum set) to the stage...your experiment indicates that it's acoustic coupling that is the culprit. That makes sense to me. And it indicates, as you seem to have confirmed, that de-coupling devices like absorbent pads under the speaker cabinet won't have much effect on the phenomenon.

But having said that, I'm also going to observe that I see a lot of folks here on TB blaming boomy, hollow stages for adverse acoustic effects that they probably don't really cause. IHMO, of course.

That's surprising for me. I have always felt that my rig lost substantial amount of bottom end as soon as I lifted it off the floor...even if it remained close to the floor.

I haven't done any measurements though...