Volume-sucking walls

[jlane72t]

I had a strange experience this weekend. Jammed with a couple of guys in their basement. Three of us, a guitarist playing thru a medium-sized combo and a drummer. Neither of them were playing particularly loud, I didn't even have earplugs in and I can be rather sensitive to volume. I've certainly jammed with much louder.

For some reason, I couldn't be heard. I was running my LittleMark III into an Avatar 2x10, my usual rig I've played in all kinds of environments without ever turning it up even halfway. Yet this weekend I had the volume and gain cranked to 10 and still couldn't keep up. 300 dimed watts, eight feet from the other guys, and it was barely audible when they were playing.

I was using 2 very tonally different basses so it wasn't them. My amp EQ was flat as always. I suspect it had to do with the cement walls and cement floor...the guys were each against the wall (a corner between them) and I was opposite them in the open room, facing towards that corner. So is it possible to suck that much volume out just by having all that concrete around?

I felt a personal blow to the micro-head cause when the guitarist said "I, um, think you need a bigger amp pal" and I attempted to explain to him that I've blown the walls out of much bigger spaces with it.

[christw]

I have an interesting situation in my room a lot like that. I have two 8" subwoofers on either side of my computer desk and there is a spot in the middle of the room where you cannot hear any bass at all. However, it gets louder as you move radially outwards and around the perimeter of the room it rattles with bass.

You could try moving your amp (next time?) to find a better position. I'm not usually in the middle of my bedroom so it isn't an issue for me.

[jlane72t]

Yeah for some reason at the time it didn't occur to me to try moving the amp. I will be trying that next time....but I'm curious about the reasons why, not just the solution.

[Jazzdogg]

I've attached a spreadsheet about the LF boundary cancellations that can vex bassists; the information comes from ProSound.net:

http://www.padrick.net/LiveSound/CancellationMode.htm

[Doodaddy]

Originally Posted by Jazzdogg

I've attached a spreadsheet about the LF boundary cancellations that can vex bassists; the information comes from ProSound.net:

http://www.padrick.net/LiveSound/CancellationMode.htm

Beat me to it.

Though I will say that this is more of a situation in the lower spectrum of your instrument.

[billfitzmaurice]

Originally Posted by jlane72t

So is it possible to suck that much volume out just by having all that concrete around?

Yes. Reflections off the walls in small areas result in phase sourced response suck-out as much as 24dB deep. This fact is what gave rise to the myth of 'wave development'. It's why you often can't hear your lows on stage, where there are boundaries close to both your speaker and you, while farther back in the room the lows are shaking the room.

[Blankandson]

Concrete is horrible with the 300Hz area of sound. When setting up a small system in a concrete block building, I ALWAYS pull the EQ down around 300Hz. Even if that is all I do it helps. This may have nothing to do with your bass not being heard but it may help get rid of some PA feedback next time you gig there. Next time you go to a venue, look around for large accoustic pannels hanging around the walls. Those are there for a reason. Maybe you can hang some old blankets where you rehearse?

[Gearhead17]

Originally Posted by Blankandson

Concrete is horrible with the 300Hz area of sound. When setting up a small system in a concrete block building, I ALWAYS pull the EQ down around 300Hz. Even if that is all I do it helps.

I had the same experience myself - on the other hand, I used that frequency range to cut through my band and hear myself. I kept it in check though.

With a lot of concrete surfaces, it usually helps me to remove a good amount of energy below 80hz, and just focus on the 200-600hz spectrum of bass tones to get some sort of audible tone. It may sound bad, but at least I can hear myself.

I have done shows with 2 Eden 410XLT's (PA for vocals only) and the brick walls surrounding the entire room killed just about everything with my tone and volume. I barely heard myself play unless I was within three feet of the rig. When I did our sound check, I noticed 30 feet out you could no longer hear much of what I played - it was just some rumble with unintelligible notes. Two Eden 410XLT's should be crazy loud, and they were in CERTAIN environments.

With the Avatar 210, was it stacked vertical? Try tilting it next time - I have my own personal 2x4 piece with me for the same purpose

[chadhargis]

Try turning the cab toward the wall, or setting it in a corner.

If your 210 can handle full gain and full volume of a 300w head, it's the God of all 210 cabs.

I've got a Markbass 102p 210 combo and at a little less than half gain and about 1/3 volume, the 10's will fart on the low notes if I dig in. Of course, that's with the low bass on the head bumped a bit and also bumped on my bass. I like the low end. LOL! I added another 210's, and I don't have that issue any more. I rarely turn up past 25% and the volume is PLENTY. I did this on my last gig where I had no PA support with a keyboard and drums. I had a recorder set up in the back of the room and there was PLENTY of bass. The stage was vibrating from my bottom end. The way God intended.

[jlane72t]

Well, it's a 500w cab so I assume it can "handle" it from an avoiding-damage perspective. As far as tone quality....well at that point I was happy to just to hear *anything*

[JimmyM]

Originally Posted by jlane72t

Well, it's a 500w cab so I assume it can "handle" it from an avoiding-damage perspective.

sorry, but that's an incorrect assumption. 500w is the wattage that the voice coils burn out. but in the real world, the fartout point is much lower, usually at least half as low. so don't just assume that your cab can handle the wattage they quote...power handling specs are one of the most abused and most bogus specs out there.

[Petebass]

Buy a big thick curtain and hang it on the wall. Put a rug on the floor. And if you can, install some corner reflectors.

[Foz]

Low frequency resonances cannot be controlled with blankets.

Best bet in the situation you describe is to do as advised above and move the speakers - the corner you describe between the drummer and guitardist might have worked better - or perhaps a similar corner area across the room???

The reverberant behavior of a room is an extraordinarily complex mechanism and citing single dimensions does not help one understand the mechanism as a whole. Room reverberation is a 3d matrix of resonance patterns intrinsic to all of the the room's dimensions. FWIW I bet you plunked you rig down on a spot with multiple modal nulls. Download the "Room Modes and Reverberation Time Calculator" from the link below if you want to explore the concept of a room's intrinsic modes.

http://forum.studiotips.com/viewtopic.php?f=27&t=1414

In addition to room modes you may also wish to read a bit on speakers interfering with themselves due to strong reflections off nearby surfaces coming back to the speaker [SBIR] - this issue is much over emphasized on the web and over simplified as well. In a real room, SBIR is not a simple matter arising from the distance of the speaker to a single surface, and can just as easily cause increased responses versus "suck out" - see section 4.2 here for more:

http://www.rpginc.com/news/library/PS_AcD.pdf

Don't pretend all concrete room features share acoustic properties, this will not prove true in the real world. Cement, plaster, concrete block, tile, brick and other cementitious materials will vary a great deal as to sound absorption properties - especially when comparing painted versus unpainted versions [materials with no holes or the holes filled with paint are very reflective]. Unpainted coarse concrete block is actually a reasonably absorptive material all the way across the band - painted block much less so.

You can look at some Sabine numbers [acoustic absorption index - higher number means more absorption] for these materials and a number of others here:

http://forum.studiotips.com/viewtopic.php?f=27&t=2841

example - Sabines per frequency band:

63 125 250 500 1k 2k 4k 8k

0.36 0.36 0.44 0.31 0.29 0.39 0.25 0.25 Concrete block, coarse
0.10 0.10 0.05 0.06 0.07 0.09 0.08 0.08 Concrete block, painted

[Mr. Foxen]

Leaning right up against the wall, putting your ear near it can make the bass audible to you, because you don't have the cancellation from that wall. I only noticed that because I was pressed against a wall trying to avoid the treble for a guitarist who eqs standing on top of his half stack.

[Petebass]

Originally Posted by Foz

Low frequency resonances cannot be controlled with blankets.

Last I looked, bass was a full range instrument?