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Mesa Boogie Walkabout Scout-extension for 4 ohm optimization

PJams

PJams

Mar 13, 2017
53
98
Scottsdale
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#1
Hi,

I have the Walkabout Scout 12", 4ohm model. I am a newbie at figuring out how impedance works. Would an 8 ohm extension cab that has two separate drivers (say a 2x12) paired with the 12" in the combo create the suggested 4 ohm load?

I have scoured previous threads and this specific question does not appear to have been addressed.

Thanks,

PJams
 
#3
LeftyD said:
I'm going to say, no. If your model is the 4 ohm model, it is running at 4 ohms with the 1x12 speaker in it. If you add an 8 ohm cabinet to it, you will now be running it at 2.67 ohms.
Click to expand...

True. You would need to change your 4 ohm Scout speaker with an 8 ohm speaker. Then you would be able to achieve a total 4 ohm load when combining with an 8 ohm rated extension cab (regardless of the number of drivers). 8 ohms + 8 ohms = 4 ohms.
 
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#6
Yep. At one point I had a matching 12" Scout combo and 12" Scout extension (wine taurus/beige grills). I ordered the extension at 8 ohms and swapped the speaker on the combo. Pretty nice rig, should have kept it since I went ahead and bought another Walkabout combo later on after trying out a few other things.
 
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#7
If I added a 2X10 or a 2x12 to my current setup and ran at 2.67 ohms, since the extension cabinet has two drivers, would the power then be evenly distributed among all three speakers? Also, do you think I would be missing the effect of the radiator if the walkabout was sitting atop a 2x10 or 2x12, or would the extension more than make up for the radiator?
 
#11
Using a multimeter, unplug the speaker from the amp and measure the D.C. resistance from tip to sleeve on the plug. If it's below 4 ohms it's a 4 ohm driver (should be around 3 ohms) and if it's beteeen 4 and 8 ohms (should be between 5&6 ohms) than itscthe 8 ohm version.
 
#12
PJams said:
If I added a 2X10 or a 2x12 to my current setup and ran at 2.67 ohms, since the extension cabinet has two drivers, would the power then be evenly distributed among all three speakers?
Click to expand...

If you ran your current setup (4 ohm internal 12") with an 8 ohm 2x10 (or 2x12) extension cabinet, the internal speaker would get 2/3 of the power (because it is 4 ohms), and the external cab would get 1/3 of the power (because it is 8 ohms). The 1/3 power would then be split in half between the two drivers, so each driver gets 1/6 of the total power. So therefore the internal driver would be working 4x harder than each of the drivers in the extension cab.

Additionally you would risk damaging your amp because 2.67 ohms is lower than the recommended minimum 4 ohms.

Not a good idea. I wouldn't try it.
 
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#13
I have two Walkabout 12" 4 ohm combos, and I've run 'em in about every configuration I can imagine, including periodically running them as a ministack from one amp at 2 ohms.

My 2¢ based on that experience:
  1. Neither of my redhead-era WA heads has balked at running the two WA cabs (at a 2-ohm load). I've played multihour gigs at 2 ohms without the amp getting particularly warm.
  2. But that's because the cabs are the bottleneck, and pushing them past a certain point would just result in more speaker compression and heat, but not much more usable volume. So even with two WA cabs, I'm not flogging the head especially hard. (I think it was lomo who reported years ago that he didn't notice much SPL difference b/w the 4 and 8 ohm WA cab versions. I suspect that's true.)
  3. Putting 1 & 2 together: if you're adding more cone area to get more volume, my advice is to use the WA head to drive different cabs entirely rather than sending half (or more) of your amp's power to a WA cab (4 or 8 ohm version) that hits its SPL limits pretty early. For example, a WA head drives my Bergantino AE212 or Schroeder 21012L noticeably louder (and cleaner) than it'll drive two WA cabs. The Berg and Schro cabs—each of 'em a 4 ohm cab—I wouldn't double up to run the Walkabout at 2 ohms; because either will take all the head can give at 4 ohms, and together they'd give it room to work too hard at 2 ohms.
Not that the WA combo cab isn't useful. It's surprisingly big and rich sounding, and it's convenient for the right sized gig. But if you're chasing more volume, I'd take a different road.
 
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#17
aaronious said:
I have the 4ohm combo. Today I will be replacing my 4 ohm factory speaker with an 8 ohm Celestion. Will report back soon.
Click to expand...

I suggest you consider the stock 8 ohm speaker, the TS parameters are more critical due to the passive radiator loading of the cabinet.
 
#18
I'm going to repeat myself here so there's no confusion... it is not recommend tgatvtgw WA be operated at 2 ohms. While it should hopefully survive, there is a much higher risk of (expensive) damage to the amp.
 
#19
agedhorse said:
I suggest you consider the stock 8 ohm speaker, the TS parameters are more critical due to the passive radiator loading of the cabinet.
Click to expand...
Can you explain what that means in layman's terms please. I have put the Celestion in there and it sounds fantastic. Unless I'm going to blow something up I will keep it in there. But you would MOST CERTAINLY know better than I.
 
#20
aaronious said:
Can you explain what that means in layman's terms please. I have put the Celestion in there and it sounds fantastic. Unless I'm going to blow something up I will keep it in there. But you would MOST CERTAINLY know better than I.
Click to expand...
There's no way to know what the mechanical power handling is because the passive radiator affects the tuning and the driver used has taken this into account.

It may work fine, but it may also be damaged, though you do have the lower power of the amp working in your favor.
 

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