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Mesa Boogie Walkabout Mega-thread Part 10

#1,781
bonz - darrell said:
Update: Surprisingly the 1x15 cabs sounded horrible. Not just mediocre, but horrible. With both 1x15's plugged in (for a 4 ohm load), they were probably less than half the volume of the 2x15 cab (at 4 ohms), and distorted with the same amp settings as going into the 2x15... and horribly distorted when I tried to bring the 1x15's up to the same volume.

The cones in the 1x15's were bouncing back and forth at least an inch. After doing some research, it would seem that the port is dramatically undersized on those two cabs. I found some plans online that create 1/2 of a Sunn 2x15 cab (the 2000s if I remember correctly).

So last night I pulled the speakers back out, and unscrewed the front panel (it wasn't glued). My plan at the moment is to create a new face assembly that includes the classic long narrow port (2 1/2" x 20 as I recall) and the 45 degree baffle inside.

I know that kinda falls into a thread about cab building, and I'm going to end here. But it definitely shows the effect of cabs on a head, and how a perfectly good amp can be completely failed by crappy cabs...

Oh well, let the woodwork games begin!
Click to expand...
Have fun with the woodworking games! And good point about the cabs. I think many people (and I used to be in that cab) underestimate what a huge impact they can have on your tone, max volume, articulation -- everything, really. When you're playing electric, cabs are, to some extent, analogous to the body of a doublebass -- not entirely, of course, but they are the big, vibrating, air-moving part of your instrument -- an important part!

If you do achieve improvements with the WA and those cabs, report back!
 
#1,782
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#1,785
This has nothing to do with the cabinets being 115 versus 215. There are other possible causes, for example did you verify that both drivers have the same polarity? Some aftermarket recone kits do not use the original standard which is positive voltage on the positive terminal causing cone to move inward.

ALWAYS verify cabinet polarity when working with JBL drivers, and verify that with positive voltage on the CABINET'S positive terminal, each driver moves outward.

Only then can you "assume" your problem is due to porting, but you should calculate this to confirm (or not) of it is a porting issue. Guessing is not the way to get good results!

Another thing... the 140's are good for about 125 watts "RMS" each, no more than that. Be careful you don't damage the drivers from too much power.
 
#1,786
rodl2005 said:
@bonz - darrell
Are you sure the 15s ain't outta phase with each other? If I plug in and get half the volume. ..I immediately check phase.
Might be
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I have them taken apart making the new baffled fronts. I'll check the input jack soldering job.
I don't think its phase because of the farting out/distortion but its definitely worth checking...
Thanks!
 
#1,791
Flaky Tuna said:
Is the Mesa Walkabout louder than say an Ampeg V4B?
Click to expand...

It's hard to say. I owned a vintage V4 for a while at the same time I had my Walkabout (which I still have). Watt for watt that V4 was one of the strongest amps I have ever owned. It would get crazy loud for 100W. I have A/B tested them in the same cab. But if I had to guess I would say they are about the same volume wise.

That being said, I run my Walkabout with two Scout 15" cabs. It gets stupid loud. I have had people come turn my volume all the way down after shows to prove that the master volume is on about 1.
20160612_112708.jpg
 
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#1,792
As the walkabout can safely do (about 500w @) 2 ohms. ..with 3 12"s it'll get very loud. I found it'd often be not quite enough clean volume into 2 12"s but add another - reducing the impedance to 2.67 ohms and it would be as loud as I could ever want without PA support. Ime...louder than the V4B will get. ..but, hey, that's 100 watts compared to 300-500w
Also. ..its close..but doesn't quite have that all tube output. ...that the V4B etc have. A VERY nice amp. But I'll take a tube output section over a hybrid design any day.
 
#1,794
bonz - darrell said:
I don't think its phase because of the farting out/distortion but its definitely worth checking...
Thanks!
Click to expand...
This is exactly why I suggested it, one driver with reversed polarity changes the acoustic loading on the other driver, so neither will behave as they should (in addition to the obvious lack of low frequency volume)
 
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#1,795
Flaky Tuna said:
Very helpful. Thank you. I had a walkabout that I paired with Genz Benz Uber 410, but I thought it sounded pretty sterile. I guess I have to redo this voyage with some sealed 12's to get the sound I'm after.
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The Walkabout REALLY opens up at 4 or 2.67 etc ohms. Provides almost double the power and the extra drivers (cone area to push more air) really adds a lot more volume.
If think that GB UBER cab would be superb with the amp but 2 410Ubers would REALLY let that WA show its muscles.
The WA has a terrific and very adaptable eq section. I'm sure I could make damn near ANY cab sound great with it.
It's more an issue (for me at least) of whether there's ENOUGH cab to get the volume needed. ..coz the WA has tone in abundance.
 
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#1,797
agedhorse said:
This is exactly why I suggested it, one driver with reversed polarity changes the acoustic loading on the other driver, so neither will behave as they should (in addition to the obvious lack of low frequency volume)
Click to expand...

Bingo! One cab was wired black to sleeve, the other red to sleeve. Made them both black to sleeve -- big difference (to say the least).

Thanks agedhorse! I would have never figured that out...

I'll post up pics of the new cab faces with baffles later.
They're going to rehearsal loaded with e140s tomorrow, and k140s next week

I'll report the results as well.

Once again, thanks agedhorse....
 
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#1,798
Excellent. Now you should perform the battery polarity test to be sure that it confirms to modern day polarity standards. My guess is that they will be backwards.

I went through the factory JBL school during the early 80's and this was a big issue as my they were revising their internal standards to conform with the rest of the world. Legacy products retained the old polarity standard and new products migrated to the new standard.
 
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#1,799
agedhorse said:
Excellent. Now you should perform the battery polarity test to be sure that it confirms to modern day polarity standards. My guess is that they will be backwards.

I went through the factory JBL school during the early 80's and this was a big issue as my they were revising their internal standards to conform with the rest of the world. Legacy products retained the old polarity standard and new products migrated to the new standard.
Click to expand...

Ahha. Confirming that the wiring was backwards was simply a google search away. But a battery polarity test is beyond my scope of knowledge. I'll google that, but anything you can add would be helpful.

Thanks!

edit: so basically with a 9v battery hooked positive to postive on the speaker and negative to negative on the speaker, when I connect that battery, the cone should go in first, then out. Correct?

edit2: both of my k140's when connected red to pos, black to neg go in then out when connected to a 9v battery. I'll check my e140's tomorrow (they're already loaded in my car)...
 
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