more LF acoustic questions

[wrgflyfish]

I've read lots and have some ideas but want to get validation.

Our room is 40 x 70. The floor is carpet covered concrete. The stage is 40 x 10 on one end. At the other end in each corner is a mechanical room 8 x 10 ish. The ceiling is open wood trusses with wood for the ceiling itself. The walls are 12 ft that peak to 17 ft at the center. There are 4 large windows along each wall and the walls are drywall. The mechanical rooms are only 8 ft high so there is an open area above them.

The stage is the most permanent stage you can make and still be temporary which was required by occupancy rules. The stage is 2 ft high made essentially like a stand alone deck (not fastened to the walls). The front is coverered with wood paneling. The top is carpeted. The drum kit sits in the center of the stage on additional risers. The risers are 4 x 6 foot and are framed with 2x4s and a sheet of 1/2 inch plywood on top. They are stacked with 2 of these on the bottom and a 3rd on top so it is 8 inches tall.

The sound booth is at the back in front of one of the mechanical rooms. It is a wood desk built on top of 8 inch joists. We have the amps on the stage with the mixer and a Driverack at the booth. Only the mains currently go through the driverack. The monitors use aux sends from the board.

On the back wall behind the stage we have 8 2x4 DIY sound panels to help with monitor bounce (I think 2 inch thick). Behind the drum kit we have 1 of those panels horizontal. In one corner of the stage we have 2 of those panels vertical and in the other corner we have 1 of those panels vertical.

We have piano, electric guitar, acoustic guitar, bass, un-miked drums plus up to 4 vocalists. The bass is on the stage with a bass amp for his monitor. We have 2 wedge monitors that has both guitars and lead vocal and 2 wedge monitors that have vocals and acoustic guitar. The pianist has a personal monitor. The bass has no additional amplification.

During special services there may be additional instruments. Our decibels can normally be kept between 90 and 95. To do that requires us to normally only use the monitor sound from the instruments.

So the problems are multiple:

1) Lots of unclear bass in the room. The stage resonates and we have lots of peaks at the 100hz frequency.
2) The over all volume is higher than we would like too but when you get people singing it adds up.
3) The clarity of our instruments is limited because of the monitor bounce.
4) We have to cut a lot of bass (currently do that on the input side of the driverack and the output side of the guitar monitors.

I see 3 primary things we can do in no particular order.
1) We can add more sound panels in the corners especially but everywhere too.
2) We can add some diffusers.
3) We can try to stop the stage from resonating.

Questions then follow on the best way to do that:

1) Would adding sheet insulation to the risers help any or do we need to do something to the whole stage? Getting under the stage will be a little bit difficult so I don't want to do it more than once.
2) Would putting a deadening layer under the bass amp help?
3) We have left over sheet batting insulation (still wrapped in plastic) from the building project in the attic. Would it do any good to put those above the mechanical rooms?
4) What about the sound booth? We can feel it rumble with the lows in the room. Would adding sheet insulation under the desk or on the modesty panel help any?

Lots of information and lots of thoughts and questions, I hope it isn't too overwhelming.

Wendell

[waynehoskins]

Some questions...

Style of music?
Can you push the PA more?
What is the PA? How good is the processing?
What are the monitors?
What's your stage volume?

Quick thoughts...
That room seems a little small to have major issues at such a low frequency.
How's the clarity? Could that be the issue and not excessive low frequency standing waves?
If you can't get the PA over the stage volume, that can lead to the perception of "there's too much bass".

[cmchamp]

My thoughts were along the lines with Wayne's regarding stage volumes.
It is good practice to place a high pass filter between 100Hz and 150Hz on any floor wedges in smaller rooms to reduce the LF energy washed from stage.
Personal monitors might be something to look at seriously.
Processing for the monitor signal path is a must as well to increase clarity for foldback.
Regarding dampening the stage, more mass and fill the void.
C.

[wrgflyfish]

Style of music? - Contemporary Christian Rock for the trouble songs but we have quite the mix.

Can you push the PA more? - We can but the overall volume goes too high.

What is the PA? Two Community Veris28 Two-way Dual 8" 750 Watt mounted on trusses w/crossover cutting out the lows, no sub

How good is the processing? Our board stinks.

What are the monitors? The vocals monitors are JBL JRX112m Two-way 12" 500 Watt. I don't know the other 2 off the top of my head but are much older and not the same.

What's your stage volume? The whole room is pretty consistent with volumes but the band always wants more. It is worse when we have 2 guitarists because they then share a monitor.

How's the clarity? I would call it muddy/rumbly in general. The reverb is quite high.

Could that be the issue and not excessive low frequency standing waves? I would say yes but there seems to be certain songs that are extra bad. I haven't checked the chords on those songs to see if there is a pattern.

Something else I thought of while answering this question is that we are near the interstate and semis driving by will also add to our rumble issue. They are a good 100 - 150 yards away but you still hear/feel them.

If you can't get the PA over the stage volume, that can lead to the perception of "there's too much bass".

It is good practice to place a high pass filter between 100Hz and 150Hz on any floor wedges in smaller rooms to reduce the LF energy washed from stage. The band won't like what they hear on stage but I can explain and convince them. We really work well together most of the time.

Personal monitors might be something to look at seriously. - On the wish list but probably won't happen until the next building phase. At which point I will insist on an acoustic designer up front.

Processing for the monitor signal path is a must as well to increase clarity for foldback. - The guitar monitors have a 9 band eq on them and the vocal monitors have none although all the inputs have a 80Hz cut off. I can reroute the guitars into the driverack to get a better eq there and then use the 9 band on the vocals. We have discussed doing this anyway because the driverack also has the automatic gain control that might help on the louder dynamic changes.

Another thought makes me think the stage volumes are the culprit. When we play a CD (even loud) it doesn't seem nearly as muddy. In fact we boost the lows there. We play the CD through the monitors as well so they sort of act like our sub.

[waynehoskins]

If it's full-out rock-and-roll (a la Crowder), then you want to mike everything up including the kit, put a shield around the kit for isolation, probably isolate guitar amps in another room, lose as many wedges for ears as you can, get good dynamics processing, add subs, and perhaps turn the PA up a bit more.

[prochlea]

you might also consider putting the wedges on spikes. Your wedges could be coupling with the stage and increasing the LF energy. We had problems with muddy bass until I decoupled the subs from the floor(the subs sit on the stage). I actually used some scrap 2x4's and made some little pieces to put under the subs.

[SamG269]

I was looking at your pics.. Are your speakers flown behind the stage?

[wrgflyfish]

"a la Crowder" is accurate. We have tried with and without a shield on the kit. Neither has helped the overall volume or overall sound. We run without a shield now because the drums sound so much better that way. Our guitars are run through the house amps. Their only sound is in the monitors. The speakers are flown from a truss that is about even with the front of the stage.

I hadn't thought about the wedges coupling just the bass amp. That's pretty cheap to try. Is there consensus that 2x4x would work as well as insulation?

[prochlea]

Is there consensus that 2x4x would work as well as insulation?

It works for us - we have 2 15" subs stacked on each side, and I use about a 4" square block under each corner, and we set it all up on a rug that's flipped over so the soft side is on the bottom.

[waynehoskins]

Originally Posted by wrgflyfish

"a la Crowder" is accurate. We have tried with and without a shield on the kit. Neither has helped the overall volume or overall sound. We run without a shield now because the drums sound so much better that way. Our guitars are run through the house amps. Their only sound is in the monitors. The speakers are flown from a truss that is about even with the front of the stage.

I hadn't thought about the wedges coupling just the bass amp. That's pretty cheap to try. Is there consensus that 2x4x would work as well as insulation?

Add a shield but mike it up. The shield isn't to reduce volume, but reduce bleed into other mics. Mic the guitars and everything.

The best single thing you can do to reduce stage volume is to move the drummer over to ears. Since the drum wedge is the loudest thing on stage, by removing that you've made a decent dent in it.

This month I'm mixing a jazz musical revue at the local theatre, and it's peaking low 90s (C-weight slow) on the meter. That seems too low for modern stuff -- not that it should be 120, but perhaps 100. Also that's slow response; fast response would tend to yield higher numbers with uncompressed program -- so if you're uncompressed and measuring fast, the low 90s you spoke of possibly are lower than the mid 80s, peak low 90s, of my musical.

Can you try miking everything and turning up the PA in a rehearsal to see how it sounds? What do you have for per-channel compression?

Another test, in a rehearsal, take an SPL reading, and then turn the FOH rig off. What does it read then? If it didn't drop more than a couple of dB, or nothing at all, then excessive stage volume is part of the problem.

[Gracetech]

Decoupling the monitors is going to be barely percieveable. Your problem is you have too much back wave coming off of your monitors. In a space like yours i would use as small a monitor as you could get. Right now your LF from your monitors is overpowering anything your mains can do. Think about it you have 4 monitors where all of the LF energy is going into the audience at full volume and the only thing you have to balance it out is what i would consider fills(Veris28 ). Roll off your wedges starting at around 400Hz step down a dB for every band below it. So If 400 is 1 dB down then 200Hz will be 4 dB down...so on so forth.

It's going to sound comparatively "Thin" to the musicians but it will help you manage the LF energy in the house. If your room is full of bodies then you shouldn't have any LF issues. Humans make the best LF traps. .

crt

[Tim Padrick]

I find that most folks like the vocal monitors to sound "big & chesty" when they do the old "check one two". But once the band starts and the house is up, the only thing that monitor fatness does is muddy up the sound both on stage and in the house. Thin those wedges out buy cutting what you can below 400, so long as it does not affect pitch rendition or the ability to find the beat.