Issues with certain notes through PA

Not quite sure what's happening here. Normally, I use a Low Cut filter ( HPF) on the lower notes. Since it's on the G String you could use a Fishman Dual Parametric DI.
There's one in the TB Classifides right now for a very reasonable price.

 

Why not use the DI on the Sansamp to try something different first? The BDDI is designed to operate that way, and is industry standard as they say. Right now your feeding a preamp, into another preamp, then out through the Ampeg DI.

The DI on inexpensive amps like the BA series is an afterthought. There's a reason a good DI box cost a couple hundred bucks.

I'D start there first. if you get the same results, then you can eliminate that its in issue with either preamp.

 

You didn't mention what mixer you're running. Anything digital will have parametric EQ's, and should find the offending frequencies in short order. A analog board with sweep mids might too, if the mid frequency control goes low enough.

 

Are the subs in your p.a. on stage? They shouldn't be, unless your stage is made of concrete. Boomy stages can make you hear some very unsavory things.

 

First question: Does the same problem happen when you play those notes on the D string? If not, then despite your perception, the bass itself is almost surely where you want to start the solving. There are steps you can take with the bass itself (deadening, soundpost, strings, etc.) to mitigate the unwanted booming/blooming.

Second question: Does the problem occur only in this room? Generally, a wolf tone occurs as frequency-specific feedback between the instrument and a speaker which is near to it, but you have indicated that there is no wolf tone on stage. It sounds like you have found a "room wolf tone," for lack of a better term - an unfortunate coincidence of room dimensions and frequencies.

I've played such rooms. If it's not your room (meaning you can't change it), about the only thing you can do without drastic EQ is to experiment with speaker placement to change the reflection pattern. Apparently the problem is around 110-115 Hz (and maybe overtones of same). In the end, you may simply have to adjust your playing to the room.

 

I like to use my own modest backline and ask the desk to bring up the mids, cut out the subs if poss and no bass through the monitors. But that’s without IEMs so might not solve your probs, Trimmo. In any situation I always use HPF.

 

I sometimes do have boomy sounds around F# G and Ab. I guess this depends on the instrument, maybe this is around the body´s resonance frequency. Some strings types will emphasize those notes, others not. What works for me is a notch filter. In your case the notch frequency should be around 115 Hz.

 

I know exactly what you’re dealing with, and a high pass filter can help, but at the expense of rolling off considerably more low end below the problem notes.

The open G (or closed/fingered on the D string) is 98hz, and the octave overtone is 196. This is a sonic area where A LOT of content is summed (~90-200hz) and it’s not surprising that these notes want to take off on you, particularly as the volume goes up.

A simple amp EQ won’t give you what you need. My move has been to aggressively high pass my signal, sometimes up to 150hz or more— enough to eliminate the feedback potential. Then, I boost/add low end back into my signal. My Aguilar has a low shelf at 40hz that I boost to get the “body” back into my tone. What these EQ curves do is create an attenuation for the problem frequencies and then restore punch to the fundamental frequencies of the instrument. Most importantly, it makes the instrument “feel” right when I’m playing at loud volumes.

 

Pat,
Are you sending the HPF signal FOH, through a DI and then boosting the low end on the amplifier? I've tried this before and usually it works.

 

Sometimes a screwdriver and a trip through all the speakers tightening speakers, grills, etc will cure some of this. Sometimes a speaker that's on the way out will make the same sound on certain notes.

 

Room + Instrument resonance.

Notch filter 110-115Hz, or parametric EQ, both more useful solution than HPF for these frequencies.

 

You need a notch filter with adjustable frequency and width. They usually are added to pre-amps

EBD2 or if you have more dough the Felix. EBD2's notch filter is great but works only on one channel. If you are just using one pickup EBD-2 is good enough.

Note that the Felix priced at +1K - you cannot have both HPF and notch on a channel, while you can with the EBD2 but the HPF frequencies are fixed but quite useful.

Cut is more useful than boost . Remember that

 

That's exactly what I do: Lop off most of the sub and low content before it hits the FOH, and let them boost the lows back into the mix. Often times, I don't need to add any low end on my amp if the FOH is doing the heavy lifting. I'll keep my stage tone very mid-heavy for articulation and intonation referencing. If I'm powering the room from the stage, I'll boost the lows on my amp.

 

Great idea, I've been fighting Mainstage Subwoofers, on outdoor concerts for years.

 

Subs are the double bassist’s nemesis.

 

Notch filter. In addition to EBD2 and Felix (already mentioned), you might consider Radial AC Driver...