Mesa Boogie Walkabout Mega-thread Part 10

[agedhorse]

It does matter if you ever use these cabinets with others wired in the conventional way.

Battery with minus to sleeve and plug to tip should cause the cones to move outward. Removing the battery will cause the cone to return to its resting position. Just momentarily touch the battery, don't leave the battery connected.

 

[bonz - darrell]

I know this isn't exactly on topic of Walkabout heads, but since it affects my Walkabout, I figured I would post it here. There's always discussion about "what's the best cab for the Walkabout", so I'm just gonna make my own cabs.

Here goes.

Below is a picture of the new fronts (no stain yet). I used 3/4" baltic birch plywood (the same as original construction). There's an internal baffle at 45 degrees, similar to the plans online where people have dissected the Sunn 2000s. There are several discussions out there about people that have made 1x15's based on half of the 2000s. Some used the port size (square inches) of the 2x15, others used half that for each 1x15. I went with the idea that half the cone area might want half the port. I know there's lots of science involved here, and I got totally lost in the technical jargon. My way was by-guess-and-by-golly. lol.
The nice thing about the construction of these cabs is that front face simply unscrews from the cabinet itself, so if I'm unhappy with the results, I'll do some more research and break out my table saw again.
I took out the fiberglass insulation when I was working on the cabs, and haven't put it back in. There was really mixed feelings on this as well online. I'll have to do some more research...

I kind of lost on one aspect of this project. The point of going to a pair of 1x15 cabs was for maneuverability, flexibility and weight. My PH 212 weighed somewhere north of 85 lbs. It sounded great, but was big, heavy and awkward.
Each of these homebrew cabs with a JBL E140 weighs 74.2 lbs on my bathroom scale. The K140's are 8 lbs lighter, and will eventually go into these cabs, I think. But still, 66 lbs times two is not really what I had in mind.

 

[Worldeeeter]

I know this isn't exactly on topic of Walkabout heads, but since it affects my Walkabout, I figured I would post it here. There's always discussion about "what's the best cab for the Walkabout", so I'm just gonna make my own cabs.

Here goes.

Below is a picture of the new fronts (no stain yet). I used 3/4" baltic birch plywood (the same as original construction). There's an internal baffle at 45 degrees, similar to the plans online where people have dissected the Sunn 2000s. There are several discussions out there about people that have made 1x15's based on half of the 2000s. Some used the port size (square inches) of the 2x15, others used half that for each 1x15. I went with the idea that half the cone area might want half the port. I know there's lots of science involved here, and I got totally lost in the technical jargon. My way was by-guess-and-by-golly. lol.
The nice thing about the construction of these cabs is that front face simply unscrews from the cabinet itself, so if I'm unhappy with the results, I'll do some more research and break out my table saw again.
I took out the fiberglass insulation when I was working on the cabs, and haven't put it back in. There was really mixed feelings on this as well online. I'll have to do some more research...

I kind of lost on one aspect of this project. The point of going to a pair of 1x15 cabs was for maneuverability, flexibility and weight. My PH 212 weighed somewhere north of 85 lbs. It sounded great, but was big, heavy and awkward.
Each of these homebrew cabs with a JBL E140 weighs 74.2 lbs on my bathroom scale. The K140's are 8 lbs lighter, and will eventually go into these cabs, I think. But still, 66 lbs times two is not really what I had in mind.


View attachment 896263

Cool project, but good gawd...those are some boat anchors! I'm sure you have your reasons for the JBL speakers (if they're originals, now discontinued, they're classics, and probably sound amazing), but they weigh 22.25 lbs. each. I'd throw some neos in those cabs and shed 30 lbs. between the two!

 

[agedhorse]

IMO, the cabinets would look a lot better with full faced grills of some type rather than the "disco car speaker" grills you have.

You might run the math and see where your porting falls... you might find that the original guesses don't work as well as they might have seemed compared with the knowledge we have today.

 

[bonz - darrell]

IMO, the cabinets would look a lot better with full faced grills of some type rather than the "disco car speaker" grills you have.

You might run the math and see where your porting falls... you might find that the original guesses don't work as well as they might have seemed compared with the knowledge we have today.

Yeah, that's where I ran into the difficulty -- the math. I truly didn't take time to understand what all those crazy numbers in the speaker specs meant. When I have a bit more time (and before I call this project complete), I'll have to post up some questions once I have some to ask.

If I remember right, the cabs now have 50-ish square inches of porting. That's a far cry from the 19.63 the the 5" radius circle made.
Although, now the the speakers are wired correctly, I wonder what they would sound like with the original port size.

Anyone that has some math knowledge that would like to contribute, I'm an eager student...


I agree, I think the cabs would look way better with a metal extrusion grill covering the entire face. For now, I'll leave them as is, until the final specs are figured out on the port size etc.

 

[agedhorse]

Yeah, that's where I ran into the difficulty -- the math. I truly didn't take time to understand what all those crazy numbers in the speaker specs meant. When I have a bit more time (and before I call this project complete), I'll have to post up some questions once I have some to ask.

If I remember right, the cabs now have 50-ish square inches of porting. That's a far cry from the 19.63 the the 5" radius circle made.
Although, now the the speakers are wired correctly, I wonder what they would sound like with the original port size.

Anyone that has some math knowledge that would like to contribute, I'm an eager student...


I agree, I think the cabs would look way better with a metal extrusion grill covering the entire face. For now, I'll leave them as is, until the final specs are figured out on the port size etc.

5" RADIUS or DIAMETER? If it's the radius, the area is 78 sq. in. If it's the diameter, the area is ~20 sq. in.

 

[bonz - darrell]

5" RADIUS or DIAMETER? If it's the radius, the area is 78 sq. in. If it's the diameter, the area is ~20 sq. in.

Lol. Hard to imagine that my math skills are so weak, considering I have a BSc in Computer Science (and code every day for a living).

I definitely meant Diameter, which is just under 20 square inches of area.

 

[agedhorse]

Lol. Hard to imagine that my math skills are so weak, considering I have a BSc in Computer Science (and code every day for a living).

I definitely meant Diameter, which is just under 20 square inches of area.

So THAT'S how bugs get into code

I made the decision while in school that I would stay with the analog hardware track (control systems and power systems) rather than switch over to software and digital hardware. I saw how quickly the industry was changing (late 1970's) and the thought of staying current with the technology just scared the crap out of me. Glad I made that decision, as it is is hard enough keeping up with the trade magazines as it is in a slower moving field. I don't know how you manage to do it?

 

[bonz - darrell]

So THAT'S how bugs get into code

I made the decision while in school that I would stay with the analog hardware track (control systems and power systems) rather than switch over to software and digital hardware. I saw how quickly the industry was changing (late 1970's) and the thought of staying current with the technology just scared the crap out of me. Glad I made that decision, as it is is hard enough keeping up with the trade magazines as it is in a slower moving field. I don't know how you manage to do it?

Ummm. They're not 'bugs'. They are either 'undocumented execution paths', or 'retirement plans'. lol.

Eventually, most programmers either specialize so thoroughly that there is only a limited amount of relevant reading, or they generalize so completely that they become hardware installers (not totally true, but you get my drift).
With that said, give me any language or operating system, and I can be conversant in it fairly shortly, and fluent in just a few weeks/months. A language is like most any other, there are certain concepts and constructs that are generic across languages, but how they are implemented varies (widely). With 'new' technology, someone has always done something with it, and the internet is a valuable resource once you get past the ego of some of the posters.

"Geek ads" make it seem like you need to have five years experience in a technology that's only been out for two when you apply for a job. I avoid those companies, they are un-realistic and, well, geeky.

Anyhow, later this week I'll start by reading up on cabinet volume and how it's calculated so that I can more clearly ask reasonable questions...

 

[bonz - darrell]

Cab update: with the input plugs wired consistently between the two cabs, and the new ported faces, my two cabs sound great with my Walkabout.

Loud, full, fun.

I'll continue to research the exact port size they should have. In the meantime, I'm going to stain the new fronts to match the rest of the cabs and gig them next weekend.

edit: but maybe with the k140's -- the e140's are just stupid heavy...

 

[agedhorse]

Nice to see a project and its hurdles thought through and followed up with.

 

[bonz - darrell]

Further update on my e140's and k140's. All four are wired reverse to current standards -- meaning with a 9volt battery test the cone goes in on contact, then returns to resting position when I remove the black lead.

So my question is --
Assuming that my 2x15 cab (loaded with EV's) is normal polarity, should I wire both of these cabs with black to red at the speaker so that they will be compatible with any other speaker they might wind up being paired with?

I could see using my 4ohm 2x15 with one of my 8ohm 1x15's...

 

[agedhorse]

Yes, wire the jbl's so that the tip goes to black and the sleeve goes to red.

With the EVs, the top would go to red and the sleeve to black. This way they will all have the same acoustic polarity and will work with other cabinets.

 

[bonz - darrell]

Yes, wire the jbl's so that the tip goes to black and the sleeve goes to red.

With the EVs, the top would go to red and the sleeve to black. This way they will all have the same acoustic polarity and will work with other cabinets.

Thanks agedhorse.
I think I'll leave myself a note inside both cabs so that in 10 years (or tomorrow!) I'll remember why they are wired 'backwards' and not be tempted to 'correct' them...

 

[agedhorse]

Good idea!

 

[rorsini]

Hey TB Walkabouters,

Thanks for the endless thread about my favorite amp!

I just completed my fan replacement project, and I'm happy with the result so I wanted to share.

I will now use this amp for mostly practice in my quite living room. The previous fan noise level really kept me from using it in this context. But I really wanted to get lots of hours practicing with it so that I can try to develop a consistent sound with it. After replacing the fan, the noise level is a lot better. There still some noise, but it's a lot closer to the level of my GB Streamliner then it was with the stock fan from Mesa.

I walked into Mesa HQ last week and talked to them about it before I pulled the trigger. I was told that they recommended 41cfm from whatever fan is in there. Since I never run it at or more then 2ohms I figured I was safe with the new fan blowing at 35cfm.

Also, when I was at Mesa I plugged in my amp next to a newer blackface model and my silverface with the stock Sunon fan was about three times less noisy then the newer Walkabout model. That could be because they now have a lot more venting in the sheet metal cover, but it was way louder for whatever reason.

Here's some pics from the operation today:

Mesa ships the Walkabout with a Sunon fan, stock:

It was reasonably easy to figure out which of the three wires was the fan speed indicator, which knew I didn't need. For polarity of the two power wires, I tried the wires one way and the fan didn't start, so I switched them and the fan ran normally in the correct direction; blowing air into the housing, over the heat sink. I was going to install the power plugs (in the upper-left of this next photo) so I could swap the fan out more easily later, but space was tight in the case and I didn't want to deal with the possibility of the extra plastic parts rattling around inside.

Here's the new fan, wired and mounted. I didn't do anything about insulating the fan mounts from vibrating the case, so maybe that's something more I could try as well. I think it's good enough for me how it is. I also didn't want anything that could possibly come apart inside as the amp bounces around in transit, like the rubber mounts that came with the new fan.

Here it is, back in action on the Berg, and sounding better then ever (to my ears)!

Here's the package from the replacement fan. I paid $9.33 from Amazon and it arrived in about a week.

Cheers,
Rob

 

[Bugeyed Earl]

I swapped out the factory fan in my silver faced Walkabout with the same Silenx model last year (I soldered it directly to the board, not sure it was worth the hassle...) Now that I've acquired an M6 with its dual fans, I'm wondering what all the fuss was about

On a vaguely related note, I recently sold an Ampeg PF350 head, and the buyer mentioned that the fan was noisy, but I never noticed that it even had one! Different strokes etc...

 

[sratas]

Replaced the stock Sunon fan with a Noctua NF 8, mainly because it costed a third of a silenx one. The improvement has been massive. Now perfectly tolerable even in the studio. I noticed that with the amp cover unscrewed the new fan is remarkably silent, a breeze, whereas with the cover back on The fan noise gets amplified, like a sort of resonance from the case itself.
When mounting the fan, I tried to isolate the fan from the chassis as much as I could using spacers and using the stock Noctua silicon mounting holes on the fan. Maybe this is the reason because my WA has improved so much. Even the stock fan was much more silent when the case was open.
Another factor to consider is the transmitted vibrations of the fan to a resonating material under it. The WA comes with 4 tiny rubber feet glued on the bottom. My used unit had only two, because the other two were lost. The noise produced by the amp standing on my desk was ridiculous, jet take off like.
I cannot understand how a great and pricy amp can have such a flimsy feet job, Mesa should really fix this.
I drilled holes in the chassis and mounted 4 new big and tall rubber feet with screws, nuts and washers...just the way it should be done. Super stable, super isolated, high enough to accomodate a handle under it.

 

[MarkA]

Replaced the stock Sunon fan with a Noctua NF 8, mainly because it costed a third of a silenx one. The improvement has been massive. Now perfectly tolerable even in the studio. I noticed that with the amp cover unscrewed the new fan is remarkably silent, a breeze, whereas with the cover back on The fan noise gets amplified, like a sort of resonance from the case itself.
When mounting the fan, I tried to isolate the fan from the chassis as much as I could using spacers and using the stock Noctua silicon mounting holes on the fan. Maybe this is the reason because my WA has improved so much. Even the stock fan was much more silent when the case was open.
Another factor to consider is the transmitted vibrations of the fan to a resonating material under it. The WA comes with 4 tiny rubber feet glued on the bottom. My used unit had only two, because the other two were lost. The noise produced by the amp standing on my desk was ridiculous, jet take off like.
I cannot understand how a great and pricy amp can have such a flimsy feet job, Mesa should really fix this.
I drilled holes in the chassis and mounted 4 new big and tall rubber feet with screws, nuts and washers...just the way it should be done. Super stable, super isolated, high enough to accomodate a handle under it.

Maybe the small feet are there to make the Walkabout easy to slide in and out of its combo cabs? In any case, if you're not going to do that, the big feet sound like they'd be an improvement for noise, handle clearance (something I've run into with the WA atop a small cab) and protecting the amp from cab vibrations.

 

[sratas]

The best thing about bolted feet is that they will keep their place forever no matter how the amp is handled...I was tired of having my feet falling off, even my budget gear is better in that regard
i had to give up using the mesa bag, the head doesn't fit anymore, but the advantages prevail