Looking For A Solution To Rumbling Stages

PolkaHero · #1 06-19-2011, 09:10 PM

I played a wedding last night at a country club with a hollow stage. My Bergantino NV610 did nothing but rumble even when I propped it up on a dolly. I couldn't really lean the cabinet against a wall because of the wheels in the back.

Here's my proposed solution: Start using my Ampeg 810AV cabinet again and use only the top four speakers in these situations. That way I can hear myself better (top two speakers would be closer to ear level than the Berg) and I shouldn't have to worry as much about the cabinet coupling with the stage. Has anyone tried this and does it work? I've always run the 810 full range. Not really crazy about carrying it again compared to the Berg, but this is a problem that happens more often than not.

With my SVT-VR, would this cut the impedance to 8 ohms instead of four? Is that okay for the amp? It has a 4 and 2 ohm impedance switch on the back.

rpsands · #2 06-19-2011, 09:14 PM

1. half of the svt-810 is 8 ohms, and no you cannot use that with your SVT-VR if it has no 8 ohm taps.

2. How often has this happened? Typically hollow stages just have a resonant frequency you need to dial out - cutting some bass typically works, but a parametric eq can help.

ghiadub · #3 06-19-2011, 09:35 PM

Have you tried a gramma pad?

PolkaHero · #4 06-19-2011, 09:37 PM

Quote:

Originally Posted by rpsands

1. half of the svt-810 is 8 ohms, and no you cannot use that with your SVT-VR if it has no 8 ohm taps

Then why would Ampeg sell the SVT-VR/810AV combination with that option in the cabinet?

PolkaHero · #5 06-19-2011, 09:40 PM

Quote:

Originally Posted by ghiadub

Have you tried a gramma pad?

I have a smaller one that I used to use to prevent vibrations from getting to a rack setup I was using. It isn't big enough for the 810/Berg cabinets. Do you think a bigger version would help?

will33 · #6 06-19-2011, 10:16 PM

Some guys say they work, I've never used one so I don't know. If you don't have an eq knob in the right spot to dial out the resonance getting it up on something to break contact might help might not.

And it is wierd that they'd sell an amp/cab combination that wouldn't work with all of it's features. They should've made it two 2ohm halves with a series connection when running both. That wouldn't be possible with the 32ohm speakers they're using though....you're pretty much stuck with it as is.

JimmyM · #7 06-19-2011, 10:50 PM

Quote:

Originally Posted by PolkaHero

Then why would Ampeg sell the SVT-VR/810AV combination with that option in the cabinet?

Because they have other heads.

will33 · #8 06-19-2011, 10:57 PM

Yeah but the 810 goes with the tube head Jimmy, everybody knows that.

ghiadub · #9 06-19-2011, 11:05 PM

Quote:

Originally Posted by PolkaHero

Do you think a bigger version would help?

They do make a bigger one, the great gramma, it holds up to 300lbs just like the smaller one.

I have used it a bit and it helps a lot on some stages, and some stages, not so much.
I use it when I know it will be hollow. I have never A/B'd and thought that the pad made it sound worse.

If you are EQing for room waves, a 1/3 octave is the ticket to "ring" out tones that are being amplified by the room.

jungleheat · #10 06-19-2011, 11:06 PM

EQ for a problem like this is probably not the best solution. The problem is physical, therefore the solution should be physical. Decoupling from the stage is therefore the best bet. There are certainly a lot of creative ways of doing this. Carrying around ~70 pounds of extra cabinet to use as a speaker stand does not seem like the best one.

I would try something along the lines of a milk crate (or 2), covered with a folded blanket, rubber pad/mat, etc... using discretion to make sure the cab and anything sitting on it are stable and not going anywhere.

Another option (though this veers towards carrying around 70 pounds of dead weight) would be to construct an uber solid "base" to set the cab on. This might be more stable and could also have aesthetic advantages. Basically, get some MDF and make a "box" with about the same footprint as the cab, maybe a little bigger, and fill the inside completely with sand. Cover the top (and maybe the bottom) with dynamat or something similar. If you don't know, dynamat is a product mainly aimed at car audio applications that is designed to deaden resonances. You can get it in 1 foot square sheets that are about 1/8" thick. In fact, you could even try any appropriately sized sheet of MDF (24"x24" or whatever you need with a little extra in case you change cabs) "coated" on both sides with dynamat and just set that under the cab directly on the floor. You could even make another one for on top of the cab to prevent vibrations in the amp head.

As a bonus, the physical decoupling approach should allow you to actually turn down your amp, as more energy will be going to projecting the sound out to the audience (and you), giving you more headroom (and you get to keep your EQ however you want it).

**cheezewiz** · #11 06-19-2011, 11:14 PM

The Berg is superior to the Ampeg in every way. You're not going to help yourself by swapping that out. Just get a Gramma pad. Either buy another the same size as you have and put them together, or buy the large one.

PolkaHero · #12 06-20-2011, 07:12 AM

Quote:

Originally Posted by will33

Yeah but the 810 goes with the tube head Jimmy, everybody knows that.

And it looks so good with my SVT! The Berg just doesn't match as well. I guess I'm superficial.

PolkaHero · #13 06-20-2011, 07:14 AM

Quote:

Originally Posted by cheezewiz

The Berg is superior to the Ampeg in every way. You're not going to help yourself by swapping that out. Just get a Gramma pad. Either buy another the same size as you have and put them together, or buy the large one.

I think you're right Cheese. That Berg basically slays the tone of my Ampeg: tighter yet has more bottom end. I think I'll get another Gramma and try that out. It would raise the cabinet a little, also.

tharv · #14 06-20-2011, 07:20 AM

Quote:

Originally Posted by ghiadub

Have you tried a gramma pad?

+1

prd004 · #15 06-20-2011, 07:21 AM

Using half the speakers in an 810 still won't decouple your cabinet from the stage floor anyway. The gramma is made specifically to do this. Either get the great gramma or put two regular ones together. It's not a 100% perfect solution but they do work.

More annoying: Why in the heck does any music venue have a hollow stage???!!!!! I know, they're everywhere, it's just annoying!

billfitzmaurice · #16 06-20-2011, 09:41 AM

Quote:

Originally Posted by PolkaHero

I shouldn't have to worry as much about the cabinet coupling with the stage.

There is no such thing as a cab mechanically coupling with a stage. A resonant stage may vibrate, but a cab that vibrates is defective. Any any and all coupling is acoustical. You can reduce acoustical coupling by lifting the cab two to three feet off the stage, as well as pulling it away from the rear wall, but the best solution is a parametric EQ that allows you to remove the offending frequency or frequencies from your output. What isn't there can't excite stage resonances.

stflbn · #17 06-20-2011, 09:52 AM

As bill pointed out... Putting the amp on a dolly and slightly tilting it would have had the same effect.... it's not contact with the stage doing it... it's proximity. Moving it forward away from a wall will help. Raising it a large distance UP (likely don't want to do with an 810) works.

I've personally found that grammapads help quite a bit in times like these and I always carry one around with me. Not a guaranteed solution, but I feel they definitely help on boomy stages, or concrete dungeons.

billfitzmaurice · #18 06-20-2011, 09:59 AM

Quote:

Originally Posted by stflbn

As bill pointed out... Putting the amp on a dolly and slightly tilting it would have had the same effect.... it's not contact with the stage doing it... it's proximity. .

De-coupling requires the cab be lifted 1/4 wavelength off the stage. Boom tends to be in the vicinity of 100Hz, where 1/4 wavelength is 2.8 feet. A dolly that lifts the cab even six inches won't help, that's 1/4 wavelength at 560 Hz. Tilting will help, not because it does anything to suppress boom, it doesn't, but because it makes the mids and highs easier to hear, which helps mask the boom.

PolkaHero · #19 06-20-2011, 12:32 PM

Quote:

Originally Posted by prd004

Using half the speakers in an 810 still won't decouple your cabinet from the stage floor anyway. The gramma is made specifically to do this. Either get the great gramma or put two regular ones together. It's not a 100% perfect solution but they do work.

More annoying: Why in the heck does any music venue have a hollow stage???!!!!! I know, they're everywhere, it's just annoying!

I think I'm going to get the Great Gramma, thanks for the responses.

On hollow stages: probably because they're cheaper to make. Screw the musicians and their acoustical needs!

Blankandson · #20 06-21-2011, 09:14 PM

Just a suggestion: a band I was in centuries ago showed up at the Univ of Missouri and found a room that was all concrete with a hollow wooden stage in one end. We asked if we HAD to set up on the stage and the mgr said we could set up anywhere we wanted. We set up along a long wall midway between the ends. Then kept rotating the PA cabs slightly further out (making a wider angle) until we found a place where there was minimum slap or bounce. We just setup on the floor. Lots of people said later that we were the best sounding group to have ever played in that room. No wonder! That stage and it's location would have trashed anyone's sound.