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Identifying phase issues with cabs

LowendG

LowendG

Jul 30, 2013
1,015
1,911
NorCal
#1
My current setup has me sometimes using two different 1x12" cabs stacked--different manufacturers, different cab design. In my limited testing in medium-sized rehearsal studios they seem to play nicely together. At a volume that's where I wanna be in the mix with a loud drummer and a couple guitars through Deluxes, set up in a stage plot, it sounds good when I get out as far as I can in front of the rig. They achieve the desired result - louder than either cab alone, more lows, simply "bigger". But, I have not had the chance yet to really crank them in a larger space. So, does "if it sounds good it is good" likely apply here, or could I one day play some outdoor gig w/o FOH support, or need to carry a bigger stage and suddenly my bass does a disappearing act? I intend to get another cab to match one of them (so we don't need to go down that rabbit hole of what I should get;)) but for now this is the rig. Any way to suss it out before a trial-by-fire scenario?
 
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#3
If it sounds good close and far, it's good.

The advice about respecting the power limits of the weakest cab is spot on. If the impedance is the same, they share power pretty much equally. So if you have 300W cab and a 500W cab, the combined power handling is 2x300 = 600W. Also keep in mind mechanical power handling is often less than the RMS power rating.
 
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#4
Thanks folks, that's reassuring. As far as impedance and power handling, this is a bit of a different situation: The top cab is 4ohm 500w Avatar 1x12 being powered by a GK MB200, so 200w hitting that cab. The bottom cab is a GK MBP112 200w powered cab, receiving the line out/"chain out" from the MB200 head (the MBP cab has essentially the same power amp as the MB200 head). So, they're actually powered separately, making it a 400w 2x12 stack. I was concerned as the cab designs are pretty different. Seems best stacked this way so the little 6" mid driver in the Avatar is up highest for hearing myself. Took the logo off the GK so it just looks like a box I lifted my rig on;)
 

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#5
Try playing some pink noise through your rig, set the EQ flat, put your head down between the woofers a couple feet out in front, if the sound appears to becoming from in the area between the woofers they are in phase.

That said the crossover on the two way cabinet maybe low passing the woofer so it may sound different as in less mids and highs when comparing between the two.
 
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#6
Mike Caldwell said:
Try playing some pink noise through your rig, set the EQ flat, put your head down between the woofers a couple feet out in front, if the sound appears to becoming from in the area between the woofers they are in phase.

That said the crossover on the two way cabinet maybe low passing the woofer so it may sound different as in less mids and highs when comparing between the two.
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Interesting. I will try that. So you're saying if the sound appears to be coming from between the woofers, regardless of the two woofers sounding different, things should be in phase, correct? The 6" driver in the two-way cab has a volume control, I can try it with that all the way off too.
EDIT: just tried it. The sound does seem to be coming out of the area between the woofers, both with the 6" driver up top on and off. The woofers do sound slightly different.
 
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#10
ctmullins said:
You can check their actual phase with a 9V battery across the speaker cable jacks. All woofers should move in or out for a given battery polarity.
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Can’t do this with a powered cabinet.
 
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#11
agedhorse said:
Can’t do this with a powered cabinet.
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That's what I was thinking. And, even on the non-powered cab, IDK why but that battery thing freaks me out a little speaking as an electronics noob--like I'm gonna do something wrong see the driver coming flying out of the cab :laugh: .
I'd like to think it's safe to "assume" that GK has this thing wired correctly, and that Dave at Avatar did this properly too (it's a brand-new cab straight from him), no?. Even so, if the polarity is the same on both, I could still experience a less-than-desirable result from the two different cab designs not working well together in some frequencies, correct? Fortunately they seem to play real well together so far based on what I've described above.
 
#13
The 9 volt roughly equates to a very low "wattage" input (wattage in quotes for good reason) input to the speaker and is convenient way to tap on/off power when you have a 1/4" speaker cable, tip to positive negative to ring. I personally use a 1 1/2volt AA battery as it will deflect the cone move than enough. In any case you don't want to leave the battery connected for long periods, cone movement helps cooling of the voice coil. I've never damaged a speaker over 3" with a 9 volt battery.

JBL are the only "reversed polarity" drivers I know of.
 
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