Rear Porting Feedback problems?

[kringle77]

I play in mostly smaller clubs where the band gets stuffed into a corner, specifically the drummer. This creates all kinds of problems with vocal mics picking up wall reflections etc. Often, the low end from a bass amp will cause the kickdrum mic to feed back in these small rooms. My amp usually is closer to the crowd and the drumset and usually, since we use in-ears and I dont' hear my amp anyway, we set a pa top on it so it's out front. Will having a rear ported cab throw more low end towards the drummer and cause more feedback? Im thinking that it will.

[T-Bird]

Hi.

The port direction and/or location won't have any effect on the feedback. Ports don't "throw" anything, they're there to tune the helmholz resonator (cab) in order to make the speaker behave like the designer wants (/wishes ).

What's the FB frequency BTW?

Regards
Sam

[Steveaux]

If the room is that small, do you really need to mic the drums?

Anyway, run the kick mic through a gate. Set the gate high enough that only a solid stomp on the pedal will get through. The low end rumble that's building up to feedback won't be strong enough to clear the gate.

[kringle77]

To answer both of you, the problem is when low low rumble gets the kick drum vibrating. that starts the feedback. I know that it happens because low frequencies tend to collect in corners and thats exactly where the drummer sits. I always mic the kick, I also gate it very hard. Im just asking about the bass cab effect. Thanks guys

[4Mal]

I never noticed anthing like that when running Bag End 1x15's or 2x15's ... I do try to get my cab off of side walls and out of corners whenever possible, I also tend to double check that I'm not adding too much bottom when I'm stuck there if my cab is also serving the house.
Given the IEM thing - why not just add a sub to the PA and be done with the amp entirely ?

[lbwdog]

I would think the problem could be solved by proper EQ on the drum mic. Just cut the freq where the feedback occurs.

[MNAirHead]

are there any gizmos that trigger a sound? For many gigs, a bass drum is the only one that needs a boost

[Eric Moesle]

Initial post doesn't make much sense. He later says that its not feedback, but that the bass is making the bass drum head vibrate and resonate.

If that's the problem, you need to better tune the bass drum head itself, and adjust the EQ on your bass amp so that its not sending such low vibrations to the back of the stage.

The fact that you are pushing so much volume and low end in a small room is disturbing, to say the least . . .

A rear port means NOTHING as to which direction the low frequencies are "being thrown". Absolutely nothing. So long as the port isn't blocked by putting it up against a wall, there is absolutely NO difference whatsoever in a rear or front ported cab.

[kringle77]

I ran without an amp for most of the last 3 years. Big subs, the whole works. The midrange sound out of a pa is never the same. Recently I went back to my amp and just running the kick through the subs. Actually since going back to an amp, I have been using just one wall loaded JBL prx118sxlf and it's plenty. The whole sound has gotten cleaner. I've heard enough. Thanks, guys.

[Bassmec]

Originally Posted by kringle77

I play in mostly smaller clubs where the band gets stuffed into a corner, specifically the drummer. This creates all kinds of problems with vocal mics picking up wall reflections etc. Often, the low end from a bass amp will cause the kickdrum mic to feed back in these small rooms. My amp usually is closer to the crowd and the drumset and usually, since we use in-ears and I dont' hear my amp anyway, we set a pa top on it so it's out front. Will having a rear ported cab throw more low end towards the drummer and cause more feedback? Im thinking that it will.

Find the resonant frequency and odd as it may seem to a bass player CUT! frequencies from microphones that are irrelevant to intelligibility mostly around 100Hz you can high pass all Vox mics at 60hz 18db per octave and you can remove at least 5dB at .5 octave q at 120Hz odd from most kick drum mic's.
Boost a shelf at 800Hz by as much as 6 db unless its an Audix D6 mic which already has a big presence lift.
Try to get the PA to enhance the Kick drum Click not so much the boom as you have discovered small clubs have plenty of boom already.
If you can find an audio engineer that understands resonance and EQ to operate your PA its always a help.
If that dont work and the kick still isn't loud enough EQ'd without resonant ringing its down t' shop t' get some kick drum triggers M'lad.

Sometimes less bass is more something else?!.

[kringle77]

I've had 3 drummers that used kick triggers. I loved them. Unfortunately, none of them kept up on the adjustments, fit, etc. and over time the response would start to fall off as far as triggering, sensativity, etc. A frequent lazy musician syndrome. Im pretty good with sound and eq, I was just wondering how rear ports would effect anything. Apparently they won't.

[Bassmec]

Originally Posted by kringle77

I've had 3 drummers that used kick triggers. I loved them. Unfortunately, none of them kept up on the adjustments, fit, etc. and over time the response would start to fall off as far as triggering, sensativity, etc. A frequent lazy musician syndrome. Im pretty good with sound and eq, I was just wondering how rear ports would effect anything. Apparently they won't.

Just keep the back of the cab as far off a wall as sensible,
get rid of all other booming in your band, become a booming nazi!. thus keeping exactly the right amount of boom all for your evil self.
Drummers can be programmed to keep drum triggers working properly, you just have to punch in the information.

[Zooberwerx]

i've used nothing but Acme cabs with rear ports for the past 10 years and never had a problem. OTOH, for the first 5 years, I though they were cubbys for my empty beer cans.

Riis

[Petebass]

Theres a good article on the acme website explaining why port placement us pretty much irrelevant. In terms of the port triggering feedback on the kick mic, the frequencies at which Ports operate are low enough that dispersion is omnidirectional anyway. Changing the port position won't change anything.

Can I ask if the kick mic is on a stand? If so the feedback could be triggered through vibrations through the floor. A cheap rubber car mat underneath the mic stand works wonders. And I also agree that it would be helpful to identify the feedback frequency and using EQ to tame it.

[kringle77]

The rubber mat tip is a good idea. Im not having a problem with feedback very often, this thread kind of got slightly off track. I just wanted to make sure that a rear ported cab won't cause me any extra live sound headaches and apparently, it won't. Very cool. I'll have to look up the acme article. Thanks