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OT - subwoofer question


metromike

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I have a couple powered Mackie subs. I think one of them may be broke. How can you tell if one is working properly?

 

the light still comes on, but I do not hear that little "pop" when i flick the power switch. Also I can feel a little vibration coming from the unit, but not as strong as the other.

 

I'll probably be taking it to a local repair shop but wondered if anyone had any thoughts??

 

Thanks!!!

Gear: Roland RD700, Yamaha MotifES6, Roland Fantom FA76, Roland JP-8000, Roland AX-7, Roland Juno-106.
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Seems to me if the OP was experiencing phase cancellation with two subs (due to inverted wiring on one) he'd have recognized the lack of bass pretty quickly. Partial phase cancellation should only be an issue in upper bass frequencies, but if he's using identical units wired correctly and roughly equidistant from listening position it should be a non-issue (if he's sitting on one and the other is ten feet away...well...).

 

Forceman's diagnostic tips sound reasonable to me, too - easy to perform with two identical units.

 

 

..
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Every system we play through has multiple subs. It's called physics. Area times displacement. One Sub can only supply a finite amount of bass. More subs are needed for more bass. It's pretty basic. If we hire sound for an indoor gig, minimum requirement is dual 18's per side. I don't see where somebody wouldn't need 2 mackie subs for a gig.

Dan

 

Acoustic/Electric stringed instruments ranging from 4 to 230 strings, hammered, picked, fingered, slapped, and plucked. Analog and Digital Electronic instruments, reeds, and throat/mouth.

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A single sub might be enough in a small pub or club when you don't want the music too loud, but the bigger room you want to cover and the louder you want it, the more speakers and subs you'll need - it's a simple equation. If you want to amplify a rock band outdoors you'll probably find that two small subs won't get you very far.
Nord Stage 3 sw73, Yamaha CP88, KeyB Legend Live, Kurzweil PC3K7, EV ZXa1 + sub. K&M stands, Hammond E112, Leslie 3300, EHX V256, Roland SE-02, Yamaha EX5R & TG77, Novation Nova desktop & much more...
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My powered JBLs have a switch on the back to adjust for phasing. I usually take a mic an make bass drum sounds through it to check subs or us the kick if the drummer is set up, though he is usually the last to get set up.

Jimmy

 

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My powered JBLs have a switch on the back to adjust for phasing. I usually take a mic an make bass drum sounds through it to check subs or us the kick if the drummer is set up, though he is usually the last to get set up.

 

Quick note on phasing - it is frequency dependent. Half the distance of the wavelength of any given frequency will be out of phase. SO if they are in phase at 80Hz, they may be out of phase at 40Hz. A Frequency Generator that allows you to sweep the frequency with a simple sine wave would allow you to get the best compromise over the entire frequency range being reproduced by the subs. Although, keep in mind, depending on your position in the room, your relative distance to each sub will change...therefore, different phasing in different positions within the room. Add room reflections/standing waves into the mix and things get even more complex. Since bass frequencies have such long wavelengths, peaks and valleys in the sound pressure within the room will be much more pronounced than the typical comb filtering that occurs at higher frequencies.

Dan

 

Acoustic/Electric stringed instruments ranging from 4 to 230 strings, hammered, picked, fingered, slapped, and plucked. Analog and Digital Electronic instruments, reeds, and throat/mouth.

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