Seeking advice about decoupling

[SICbass]

Hi all,

I work in a show without an amp - instead I hear myself via a pre-amp through an active wedge. All fine so far.

However, the wedge tends to turn the riser that I am on into a massive sound box, producing tons of muddy bass frequencies.

Improvised efforts to decouple the wedge from the riser improve things significantly, however, I would like to build/buy something more permanent and optimal.

Are soft acoustic pucks more effective or are the small spikes (reducing contact to the riser) better?

Any advice would be much appreciated.

Cheers 

Paul 

 

 

Edited July 2, 2023 by SICbass

[chris_b]

GRAMMA pad. Beer crate. Move the monitor to a different position.

[Bill Fitzmaurice]

There's no such thing as mechanical coupling that causes the riser to resonate. There have been a few studies that prove this is the case, this is one: http://ethanwiner.com/speaker_isolation.htm

What will cause the riser to resonate is the acoustical output of the speaker. That will usually occur at a single frequency. The best way to prevent it is with a parametric EQ that allows you to cut the speaker output over a narrow range, sweeping through the frequencies until you find where it kills the resonance. Another option is to raise the speaker to 1/4 wavelength above the riser, which will cut that frequency, but finding how high to lift it is a trial and error process. 

[SICbass]

16 hours ago, chris_b said:

GRAMMA pad. Beer crate. Move the monitor to a different position.

Thanks Chris. Space is very limited, so changing position options are too. It’s a semi-permanent set-up on a show stage, so a crate, even covered looks a bit meh. Gramma pad May be an idea.

[agedhorse]

A piece of heavy carpet might help, but some of this is going to be caused by the acoustic coupling between the speaker’s acoustic output and the top diaphragm of the riser.

 

A high pass filter is one tool that may help, a parametric eq is another tool, turning down a bit might help too. 

[SICbass]

Next port of call will be a high pass filter. A parametric would be after that. I’m already at low volume. Any quieter and I’ll wear out my right hand (I’m stood right next to the drums, on the “wrong” side i.e. next to the floor tom).

[BigRedX]

Can you fill the riser with something like Rockwool RW3? Or is it open sided?

 

If that's not possible the only sensible solution would be to ditch the wedge and go for IEMs.

[EBS_freak]

As above. IEMS.

[Muzz]

Along the lines of the HPF mentioned earlier, can you dial out the bottom end in your monitor mix? Lower down the tech chain from you, for small pubs (in fact for bigger stages, too) where IEMs are impractical, I use a 112 combo on an angled stand which lifts it about 18" and angles it like a monitor at my head, but I also dial all the bottom end out of the combo, because my DI to the FoH fills in back in again automagically - I mentioned somewhere else, but I played a festival on a biggish stage, and I was admittedly fairly close to the FoH  stack on my side, but that little 112 combo sounded like an 810... 😀

[chris_b]

Any chance of changing the monitor to one that has a better sound?

[Bill Fitzmaurice]

I wouldn't blame it on the monitor. Think about what happens when your drummer leaves his sticks on top of a floor tom and you play a bit. The sticks rattle, especially at a certain note, because the head is vibrating, and not because the cab is sitting on the head. It's because the tom head is resonating in concert with the acoustic output of the cab. When a stage or riser or anything else in the vicinity resonates when you play it's for the exact same reason. The only fixes are to either strengthen the resonating surface making it too stiff to vibrate, damping the vibrations by fully covering the surface with a heavy carpet, or dialing out the resonant frequency causing the vibration with EQ.

[skidder652003]

Try one of these, you won't go back.

https://www.porteranddavies.co.uk/products/kt-platform/

[BigRedX]

2 hours ago, skidder652003 said:

Try one of these, you won't go back.

https://www.porteranddavies.co.uk/products/kt-platform/

 

I think the OP is looking for less bass vibrations, not more 😉

[skidder652003]

5 hours ago, BigRedX said:

 

I think the OP is looking for less bass vibrations, not more 😉

true!

[Phil Starr]

On 02/07/2023 at 13:26, SICbass said:

Hi all,

I work in a show without an amp - instead I hear myself via a pre-amp through an active wedge. All fine so far.

However, the wedge tends to turn the riser that I am on into a massive sound box, producing tons of muddy bass frequencies.

Improvised efforts to decouple the wedge from the riser improve things significantly, however, I would like to build/buy something more permanent and optimal.

Are soft acoustic pucks more effective or are the small spikes (reducing contact to the riser) better?

Any advice would be much appreciated.

Cheers 

Paul 

 

 

Has it ever been free of muddiness or is this a recent thing?

 

There are two probable causes of this muddiness. Poor eq or a resonance of some sort possibly even giving you a bit of bass feedback. It's probably a bit of both.

 

Floor monitors are often designed to have a flat response and few bass speakers are flat. Having any speaker on the floor reinforces the bass so floor monitors need to have the bass rolled back a fair bit just to get them back to the sound from the stack behind you. An HPF taking out the deepest bass will help too and boosting the mids will increase intelligibility enabling you to turn down a little. In this situation mids are your friends and bass your enemy.

 

You'll also be hearing a lot of bass from the PA/FOH adding to the mush. Bass is omni-directional and the higher frequencies point in the direction of the speakers.

 

Bill's example of the drumsticks is a good one. There are all sorts of resonances on stage and your riser may have it's own resonant frequency, the whole stage a different one if it is a wooden suspended stage and the air will also resonate. I doubt for example that you would have the sort corner traps to kill bass resonances that you get on a recording studio. Just moving your cab might shift these resonances so they are less troublesome or pointing it at a slightly different angle.

 

 

[SICbass]

Hi Guys,

thank you all for the advice. You’ve certainly given me plenty of good ideas to work with. I will be trying these various options in the near future.

cheers,

Paul

[Lfalex v1.1]

On 03/07/2023 at 16:46, BigRedX said:

 

I think the OP is looking for less bass vibrations, not more 😉

 

Wire it 180° out of phase? 🙃

[Downunderwonder]

3 hours ago, Lfalex v1.1 said:

 

Wire it 180° out of phase? 🙃

Not a silly idea at all. Of course it could already be out of phase somewhat, even 180°, so it would be a total gamble. Still, shaking the riser in opposition to the monitor could get you out of the woods if you got it balanced for power.