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Author Topic: Cleaning up stage rumble from a big bass rig  (Read 4524 times)

Daniel Postilnik

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Cleaning up stage rumble from a big bass rig
« on: July 04, 2011, 02:18:19 pm »

I'm running sound for a Rock N' Roll summer camp in a roughly 300 cap audiotorium. Backline is set up on a stage about 50 feet wide.

Ampeg has graciously donated a nice svt-7 pro head and two 4-10 cabs for the bass rig. Aside from the one-trick-pony qualities of ampeg rigs, it's great. Problem is, it tends to create stage rumble, I think 100-125 hz, and it's been an issue both when the kids use it and the instructors, even when nothing is running in the PA. Since a bass head doesn't have a lot of equalization control, it's hard to isolate this.

I find that I have to crank the bass (taken direct, pre-eq from the head) in the PA to overcome the rumble and get any definition out in the auditorium (where it sounds fine eventually). What basic strategies might I employ, either in making adjustments on the amplifier or at the board, for controlling the stage rumble? Also, my PA is not delayed to the backline, could this be a contributing factor?

Thanks.
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Re: Cleaning up stage rumble from a big bass rig
« Reply #1 on: July 04, 2011, 02:39:23 pm »

I believe you need to de-couple the bass cabinet from the stage.  Envision an inverted pyramid-shaped piece on the cabinet corners so there is an absolute minimum area of contact with the stage.  Or you could double-, triple- or quadruple-up the material under the cabinet, creating a "pad" several inches thick.  This should also minimize or at least lessen the amount of LF transfer induced into the deck.  Or build a "sand box" under it.

Good luck
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Ned Ward

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Re: Cleaning up stage rumble from a big bass rig
« Reply #2 on: July 04, 2011, 02:41:30 pm »

Auralex makes the GRAMMA, which acoustically decouples amps from the floor and they do work well for bass amps. I have two for my home studio, and it also eliminates rattle from everything in the room when amps are up above 2. About $50 at your local Banjo Barn.

They also make a home theatre version so that you get your LF rumble, but not the rattle of everything in the room.
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duane massey

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Re: Cleaning up stage rumble from a big bass rig
« Reply #3 on: July 04, 2011, 04:22:47 pm »

Turn it down? Oh, this is a rock camp...

Seriously, this might be a great opportunity to educate the students (and instructors) on the value of working with the sound guys to sound better to the audience.
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Duane Massey
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Paul Dershem

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Re: Cleaning up stage rumble from a big bass rig
« Reply #4 on: July 04, 2011, 04:59:21 pm »

Place a variable HPF between the bass and the Ampeg head, and roll off the lows as necessary. The one I carry in by bass bag is the FDeck HPF/Pre made by Francis Deck; it's inexpensive and works very well:

http://personalpages.tds.net/~fdeck/bass/hpfpre.htm
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Bob Leonard

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Re: Cleaning up stage rumble from a big bass rig
« Reply #5 on: July 04, 2011, 09:50:25 pm »

Auralex makes the GRAMMA, which acoustically decouples amps from the floor and they do work well for bass amps. I have two for my home studio, and it also eliminates rattle from everything in the room when amps are up above 2. About $50 at your local Banjo Barn.

They also make a home theatre version so that you get your LF rumble, but not the rattle of everything in the room.

And they work quite well on hollowstages.
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Roland Clarke

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Re: Cleaning up stage rumble from a big bass rig
« Reply #6 on: July 05, 2011, 05:21:39 am »

It might well be that the problem is a standing wave! of course trying to decouple the rig from the stage (particularly if there is a void underneath) may be helpful.  As has been mentioned above I would also turn it down, it might not be very "rock and roll" but the idea is to make the show sound good. 

Turn it down, decouple the cab from the stage, and try repositioning it to see if that helps.

Good luck!
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Daniel Postilnik

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Re: Cleaning up stage rumble from a big bass rig
« Reply #7 on: July 05, 2011, 10:29:50 am »

I believe you need to de-couple the bass cabinet from the stage.  Envision an inverted pyramid-shaped piece on the cabinet corners so there is an absolute minimum area of contact with the stage.  Or you could double-, triple- or quadruple-up the material under the cabinet, creating a "pad" several inches thick.  This should also minimize or at least lessen the amount of LF transfer induced into the deck.  Or build a "sand box" under it.

Good luck
The stage isn't hollow, but I'm going to try this anyway. I think the real problem is that the campers perceive excessive guitar loudness much sooner than they perceive excessive bass loudness (due to that handy graph of perceived loudness we all know by heart) and in general there are fewer bass-playing campers and even fewer who can play tightly.
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Bill Burford

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Re: Cleaning up stage rumble from a big bass rig
« Reply #8 on: July 06, 2011, 02:33:16 am »

I sometimes get this with basses.. If you are talking about in-between songs where you just get some low rumble from the bass.. I just had this tonight.. Tonight I didn't even bother with it but it is annoying.
tonight, I was using a di and the subs are where the rumble occured.. before the di there was a BBE bass pedal thing with Lo-Contour and boost dials.. then into a Mark Bass compressor pedal.. then a Mark Bass DI where I took the signal.. then into a 2-12 combo.
I believe the rumble tonight was coming from the fact that there was so much pre-gain before the di that the slightest vibration on the strings was coming through.. the tone was great though so I didn't want to mention it and nobody seemed to care.. but I think the same pre-gain settings on other amps causes it from time to time..
the vibrations get gained up and come right through.. sometimes I just gate it some times I let it fly. .  I don't like the gate sound on the compressor I use because sometimes when the bassist plays with a lot of dynamics and they are just lightly cracking in with some fret-work.. I can hear the gate opening to a note with my ear-buds.. it doesn't seem to be very noticeable out front especially in the relatively small space and the fact that you can still hear the actual amp on stage even with full-capacity.
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Nils Erickson

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Re: Cleaning up stage rumble from a big bass rig
« Reply #9 on: July 10, 2011, 03:20:58 pm »

Daniel,

I also run a summer rock and roll camp for the kiddos!  Pretty fun stuff, and very worthwhile work.  What I have learned after almost ten years of it though it that most kids don't have a sense of what volume is appropriate for quite some time.  I would suggest unplugging the bottom cabinet, so the one aimed at their head is still working.  Take thing like drums out of monitors and have them play like you would at almost any small rehearsal place, with mostly vocals in the wedges.  Put high pass filters on all of your open vocal mics as well. Then, YOU set everyone's volume on their amps initially.

When the space fills up with 300 people, it won't likely be so boomy.  If there will never be that many people, don't worry about getting the thunder from down under in the PA...

Have your bass instructor do all they can to ensure that the student is muting open string when they aren't being played!

Also, it's never too early to teach them the importance of protecting their hearing.  Turn down, and wear hearing protection...

Have a great summer rocking with the kiddos.

Cheers,
Nils
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Re: Cleaning up stage rumble from a big bass rig
« Reply #9 on: July 10, 2011, 03:20:58 pm »


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