Bass trap?

jazzmonkey · #1 09-09-2010, 09:36 PM

Can setting a bass cab atop another bass cabinet or combo amp dampen your sound?

I do remember reading about putting your cab on another cab not in use and losing volume due to the other speaker having a damping effect since it absorbs the vibrations from cone movement. I can't find that thread to save my life.

Thanks,
Rex

Tim Skaggs · #2 09-09-2010, 09:49 PM

I don't know about another idle cabinet absorbing sound, but anytime you elevate a cab up off the floor, they usually lose a significant amount of bottom end because they lose the coupling to the floor.

jazzmonkey · #3 09-09-2010, 09:58 PM

Yeah I have heard that as well. Does that equate to losing volume also? I guess a more appropriate title for the thread would have been volume trap.

JimmyM · #4 09-09-2010, 11:22 PM

edit: move along to the next post...nothing to see here.

Andysalt01 · #5 09-10-2010, 12:11 AM

My understanding is you lose a db or so in lows throughoss of coupling with the floor. Im waiting for alex claber at barefaced to publish a spreadsheet of sorts on his website at some point in the future as i had query or two aong these lines when i bought a cab from him. Im not very tech though so ill stop here!

billfitzmaurice · #6 09-10-2010, 06:00 AM

Quote:

Originally Posted by jazzmonkey

Can setting a bass cab atop another bass cabinet or combo amp dampen your sound?

If one of the cabs is not plugged in the answer is yes.

JimmyM · #7 09-10-2010, 08:58 AM

Quote:

Originally Posted by billfitzmaurice

If one of the cabs is not plugged in the answer is yes.

really? that means i'm one of the dopes then

sorry about that. but how does that work? seems strange to me that the bottom cab would absorb the sound and counteract the top one.

billfitzmaurice · #8 09-10-2010, 11:38 AM

Quote:

Originally Posted by JimmyM

how does that work?

Energy that otherwise would put sound into the room instead vibrates the non-functioning cone.

PSPookie · #9 09-10-2010, 11:41 AM

Quote:

Originally Posted by billfitzmaurice

Energy that otherwise would put sound into the room instead vibrates the non-functioning cone.

Interesting. To what extent?

ballison · #10 09-10-2010, 11:44 AM

Ive got an interesting thought on this...if it sounds good to you, do it. if not, change it. put more effort into how you're playing then thinking about "if the cabs unused cone is being vibrated thus reducing the efficiency of my amp"

JohnMCA72 · #11 09-10-2010, 11:45 AM

Quote:

Originally Posted by billfitzmaurice

Energy that otherwise would put sound into the room instead vibrates the non-functioning cone.

I can see where that could "theoretically" happen, but is it noticeable and/or measurable? What would be the difference between stacking an active cabinet on top of an inactive one vs. a solid block of the same dimensions?

billfitzmaurice · #12 09-10-2010, 12:09 PM

Quote:

Originally Posted by JohnMCA72

I can see where that could "theoretically" happen, but is it noticeable and/or measurable? What would be the difference between stacking an active cabinet on top of an inactive one vs. a solid block of the same dimensions?

It is both noticeable and measurable. When speakers are measured care must be taken that no unused speakers are anywhere near those being measured. A 'drone' speaker can easily give 3dB of suck out. That's 1/2 of your power.

JimmyM · #13 09-10-2010, 12:14 PM

well don't i feel like an idjit? well then, my apologies to the op.

Fetusyolk · #14 09-10-2010, 12:28 PM

Quote:

Originally Posted by billfitzmaurice

It is both noticeable and measurable. When speakers are measured care must be taken that no unused speakers are anywhere near those being measured. A 'drone' speaker can easily give 3dB of suck out. That's 1/2 of your power.

how close is 'anywhere near' ? are you also saying that idle cabinets in the room (that the active cabinet is NOT on top of) will have an effect?

okcrum · #15 09-10-2010, 01:47 PM

Quote:

Originally Posted by billfitzmaurice

It is both noticeable and measurable. When speakers are measured care must be taken that no unused speakers are anywhere near those being measured. A 'drone' speaker can easily give 3dB of suck out. That's 1/2 of your power.

Bill, I'm presuming you're talking about mechanically conducted cab-to-cab coupling here, as the cone-to-cone return loss would be much higher than 3 dB unless the cabs were facing each other and very close. Is any of that energy reradiated? Or is it just dissipated in the unused cabinet as heat? I know in a measurement situation that wouldn't make a difference as it still screws up the measurement.

jazzmonkey · #16 09-10-2010, 02:46 PM

Quote:

Originally Posted by ballison

Ive got an interesting thought on this...if it sounds good to you, do it. if not, change it. put more effort into how you're playing then thinking about "if the cabs unused cone is being vibrated thus reducing the efficiency of my amp"

Great post, it really helps add to the discussion, especially after billfitzmaurice has already chimed in. Kudos.

Everyone else, thanks for taking the time to answer my question and join the discussion without unnecessary assumptions and condescension.

Jimmy - no need to apologize. I appreciate your input based on your experience, heck, IMO experience is usually the trump factor in most things.

Honestly the only reason I'm asking is b/c I just got a cab and first night out was a jam sesh and I put on top of a combo amp that was not only smaller footprint than my cab, but was also not being used. I could not get any cut from the Aggie DB112 run by my max12. I could barely hear the cab, it sounded like it was starting to break up a little, and I knew if I pushed it any harder, it would have started to fart. I have a TE 30W 110 combo amp that I was thinking would have done a better job, and has with almost the same arrangement as that night.

Come to think of it, the way I was setup, the ports were firing underneath a table into stack of rubbermaid tubs and random stuff, so perhaps I could have been losing some perceived low end/volume from that as well? I know that the low freq is omni directional, but before the wave "blooms" isn't it possible for it to become stifled? Maybe bill can illuminate us once more?

I actually have another thread going on where I tell the story, but all I hear over there is crickets. Think I'll delete that now and let this one take over.

billfitzmaurice · #17 09-10-2010, 03:04 PM

Quote:

Originally Posted by Fetusyolk

how close is 'anywhere near' ??

Indoors, as in a living room, an unused woofer anywhere in the room will affect things. We generally measure cabs outdoors, and an unused cab within 50 feet will show up in the measurement. A drone cab beneath an active one could have a major effect.
OP, also keep in mind that a cab lifted will seem to have less bass because you can hear the mids and highs better. You also will lose some boundary reinforcement in the midbass. Those two factors along with a drone cab could have major tonal ramifications.

craig.p · #18 09-10-2010, 03:29 PM

It's been common knowledge for decades in the the audiophile world that leaving an unused speaker cab in the room is just asking for it in terms of wrecking one's sound. Having one underneath a working cab is a worst-case scenario.

On the other hand, many rooms are already pre-wrecked either in terms of construction or what's already in there, so some perspective is in order. Bringing your amp into an acoustically poor room onto a hollow stage where there's an unused backline present is one extreme example. So, sometimes it pays to worry, and sometimes it doesn't. Each situation is different and you do what you have to do.

jazzmonkey · #19 09-10-2010, 03:56 PM

BFM & craig.p - thanks guys, you all have been a huge help.

I was very surprised that I got such weak throw from the Aggie, if it were really that quiet, I don't think it would be so well reviewed. Now I know that it was all about the setup/room acoustics, what a relief. It was my first time jamming in that particular place, as well as with the new cab, so go figure.

I feel much better now about adding a DB112NT to my DB112 instead of taking it back, paying 15% restock, and getting the pair of Berg AE112s. Honestly, I liked the voicing of the DBs better, not by much. I did have a hard time making my choice, now I have no regrets, and I get to save a bit! SWEET!

Thanks again,
Rex

okcrum · #20 09-10-2010, 05:31 PM

I'm trying to understand the numbers here, Craig and Bill. Is half the power of the live speaker in a, say, living room absorbed at the unused cab+speaker's resonant frequency, or at all frequencies the cab could respond to? I mean, it's clear we're not talking about a simple single surface reflection.

Or should I just go grab the reference mic and measure it myself?