Mesa Walkabout Megathread!

[Vic]

I also switched out the fan, which may controversial, but I decided it was worth a try since the factory fan is so loud. We'll see if I go into shutdown any time soon.

Which fan did you use. I used a Vantec Stealth (vantecusa.com), which is noticeably quieter, but still not as quiet as I'd like, however, it's was the highest airflow I could get at the lowest dB level without going significantly lower in airflow.

I did a bunch of research into the stock fan and alternatives, but admittedly, I didn't really push for the quietest, because of the lack of airflow that goes with.

 

[JJBluegrasser]

I used some cheesy Typhoon fan (which contrary to another post I saw, is in fact, not very loud at all). I wasn't very specific or careful about the airflow either. What was the target airflow you were going for?

Jason

 

[Vic]

I used some cheesy Typhoon fan (which contrary to another post I saw, is in fact, not very loud at all). I wasn't very specific or careful about the airflow either. What was the target airflow you were going for?

Jason

Sunon MagLev (OE):
------------------
KDE1208PTS206
80x80x25mm
12VDC, .1A, 1.2W
2700rpm, 36.5CFM
31dBA
[Invalid or Expired Link Removed]

Vantec Stealth:
---------------
SF8025L
80x80x25mm
12VDC, 0.1A, 1.2W
2050rpm, 27 CFM
21 dBA
[Invalid or Expired Link Removed]

So, the "target" in theory should be 36CFM or so, but there's no such fan with output near that at a lower dBA rating, so I picked the lowest dBA rated fan I could find within a reasonable range of stock. The next step down is a drop all the way to like 19CFM or something, pretty quiet fan, but likely doesn't move enough air to really protect the amp under a decent load in a warm club stage and/or hot summer day gig.

 

[tombowlus]

Sunon MagLev (OE):
------------------
KDE1208PTS206
80x80x25mm
12VDC, .1A, 1.2W
2700rpm, 36.5CFM
31dBA
[Invalid or Expired Link Removed]

Vantec Stealth:
---------------
SF8025L
80x80x25mm
12VDC, 0.1A, 1.2W
2050rpm, 27 CFM
21 dBA
[Invalid or Expired Link Removed]

So, the "target" in theory should be 36CFM or so, but there's no such fan with output near that at a lower dBA rating, so I picked the lowest dBA rated fan I could find within a reasonable range of stock. The next step down is a drop all the way to like 19CFM or something, pretty quiet fan, but likely doesn't move enough air to really protect the amp under a decent load in a warm club stage and/or hot summer day gig.

How do these specs compare to the stock fan?

 

[Vic]

How do these specs compare to the stock fan?

The Sunon IS the stock fan (OE=Original Equipment).

 

[Vic]

What you all want to look for is a PC "case fan", 80x80x25mm 12VDC. Have fun.

 

[tombowlus]

The Sunon IS the stock fan (OE=Original Equipment).

I missed that little "OE", sorry.

Thanks for the (seemingly unnecessary) clarification!

Tom.

 

[JJBluegrasser]

Here's a question for you guys. The fan I put in is about 22cfm. Vic, you're right, I could be messing with trouble here. Has anyone ever pushed the Walkabout into thermal shutdown? How often, in what conditions, under what load, and had you modified the fan? Tom, I know you've run it with a 2 ohm load on a number of occasions. Have you actually seen it shut down?

Thanks,
Jason

 

[tombowlus]

Tom, I know you've run it with a 2 ohm load on a number of occasions. Have you actually seen it shut down?

Thanks,
Jason

Nope. And the only time it ever got hot on me was with an 8 ohm load, and I was having to push both the Gain and the Master pretty hard to get the volume I needed.

 

[Vic]

Update...

I just ordered a "Silenx" fan, which pushes 28CFM at only 14dBA! It's supposed to be the absolute best at "dBA per CFM" so to speak.

[Invalid or Expired Link Removed]

I also ordered a fan gasket/isolation kit from subzeropcs.com and will see if I can get it to work... the Mesa has those standoffs...

http://www.subzeropcs.com/acoustifan_fan_gaskets.html

 

[Vic]

Impedence and amp heat issues...

Just to make sure we're all on the same page here, this might help, when thinking about potential overheating issues...

Simply: At lower load impedences, an amp has a greater potential to overheat, especially at higher volume levels. Period.

The reason...

All power sources have a thing called "internal resistance" (DC, or impedence for AC). That's what you're trying to "match" for optimal power transfer on an amp, which in most cases, is still 4 ohms.

So, since a resistor gets hotter if you push more current through it, likewise, if you run lower impedence cabs, you push more current thru the (series) circuit, more current also goes thru the internal load on the amp (which is fixed), so it gets hotter. It really is that simple.

If you push an amp that's designed to run with 4 ohm loads at 2 ohms, it WILL get hotter than the design criteria. Period. Will it actually "OVERheat"? That's the specific question with each amp, depending on tons of stuff, of course. If an amp is spec'd at 4 ohms, but has such serious cooling designed in, which seems to be the case here, it may still be safe.

Just like overclocking a PC... exactly the same thing... demand more, it gets hotter, but it may very well be ok if you dissipate the heat quickly enough. Parts may wear faster, but nothing should blow up or burn up.

What makes an amp "capable" of pushing a 2ohm load is it's ability to produce enough current to maintain voltages at lower load levels without running out of juice.

 

[JJBluegrasser]

Vic,
I agree with you completely. I'm actually an electrical engineer, who coincidentally works 2 feet from a mechanical designer that specializes in thermal analysis of electronic circuits. We discussed it some this morning, and it really just an issue of tolerance. How over designed is the existing Mesa hardware. Since none of us know for sure, the only way to tell is to test it in a heat chamber or try to gather statistical data from other users and see how likely a thermal shutdown is.

J

 

[Vic]

How over designed is the existing Mesa hardware. Since none of us know for sure, the only way to tell is to test it in a heat chamber or try to gather statistical data from other users and see how likely a thermal shutdown is.

That would be an awesome test, but not on my baby.

Coincidentally, when I spoke to the tech at Mesa, he admitted that they just threw a high CFM fan in there without really doing any thermal analysis to see what was really required under different loads... just to be safe without doing the testing... so it very likely could be overkill (which is what I'm counting on.)

I asked him for the CFM spec, so I could just start searching for potential replacment fans without having to look up the one in my amp first, and without putting warranty violation at too much risk.

I'll post results with pics once I figure out what I'm going to do with the Silenx fan and the isolation kit. I really think that'll be the ticket, and if you're decent with a soldering iron, an easy sub-$20 mod to quiet the beast in low volume environments.

 

[JJBluegrasser]

So here's another one for ya'll. (I'm still interested to hear if anyone has actually thermally shut this thing down yet). Does anyone know the speaker(s) sensitivity in the 1x12 Scout? Is it two 8 ohm speakers (forward and downward facing) wired in parallel to 4 ohms? I'm wondering because I'd like to hook up an EA Cxl 1x12 (8 ohms) to it and I'm interested in how much of a volume mismatch I will create.

Any thoughts?

Jason

 

[GRoberts]

So here's another one for ya'll. (I'm still interested to hear if anyone has actually thermally shut this thing down yet). Does anyone know the speaker(s) sensitivity in the 1x12 Scout? Is it two 8 ohm speakers (forward and downward facing) wired in parallel to 4 ohms? I'm wondering because I'd like to hook up an EA Cxl 1x12 (8 ohms) to it and I'm interested in how much of a volume mismatch I will create.

Any thoughts?

Jason

My Walkabout Scout cabinet came with a total 4 ohm impedance. So I'm guessing it's an 8 ohm 12", and 8 ohm passive radiator in parallel that produces the 4 ohm load.

 

[Vic]

My Walkabout Scout cabinet came with a total 4 ohm impedance. So I'm guessing it's an 8 ohm 12", and 8 ohm passive radiator in parallel that produces the 4 ohm load.

A "passive" radiator, by definition is not electronically driven, hence the name. It's driven indrectly (passively) by the active driver (the speaker).

There's just the one 8 or 4 ohm driver in there.

 

[JJBluegrasser]

So, I just called the Mesa factory and I had an interesting conversation with customer service. I got a more thorough explanation of the passive raditor design (Vic was dead on once again) and I asked about speaker sensitivity. The answer was very entertaining to me:

"Everything at Mesa is designed by sound, not specs."

I guess that's cool. Mission accomplished. The thing sounds great. That being said, I'd still like to know if I can equally match up my 103 db sensitivity 8 ohm EA Cxl 1x12 with my 4 ohm Scout Combo.

I guess, at the end of the day, I can just hook it up and go with how it sounds.

Jason

 

[GRoberts]

So, I just called the Mesa factory and I had an interesting conversation with customer service. I got a more thorough explanation of the passive raditor design (Vic was dead on once again) and I asked about speaker sensitivity. The answer was very entertaining to me:

"Everything at Mesa is designed by sound, not specs."

I guess that's cool. Mission accomplished. The thing sounds great. That being said, I'd still like to know if I can equally match up my 103 db sensitivity 8 ohm EA Cxl 1x12 with my 4 ohm Scout Combo.

I guess, at the end of the day, I can just hook it up and go with how it sounds.

Jason

I hooked up a Bergie EX112 8ohm cabinet to the Mesa 4ohm Scout and ran them together. It sounded wonderful. But I also just used the Scout by itself at one of my outdoor jazz/blues gigs this weekend and it performed wonderfully by itself. This gig however is at a very moderate volume level. I was VERY impressed with the Scout in a live setting.

 

[Vic]

I'd still like to know if I can equally match up my 103 db sensitivity 8 ohm EA Cxl 1x12 with my 4 ohm Scout Combo.

In a word, yes. This would give you roughly a 2.6 ohm load, assuming the impedence curves and efficiency ratings were identical or at least pretty close between the two cabs. But for the sake of getting to a sensible theoretical answer in a timely fashion, let's say they are.

What this means is,

1.) You'll be underdriving your Mesa, so it'll run hotter, but may not actually overheat depending on exactly how hard you do push it and how warm the environment is. I know for a fact there are those out there who have run all the way down to 2 ohms with no problems. Worst case, it may go into thermal shutdown, but if Mesa's info is correct, you won't damage the amp. Just might be embarassing at a gig.

2.) The Scout cab will still see by far the majority of the power, so the majority of your tone will still come from there, and the EA will play more of a supporing role, which can still be useful to help fill space... and ironically, potentially allow you to run a lower volume level at the amp and counter item #1 above.

IMHO, and YMMV

 

[Vic]

Another reply to my PM...

I'm not familiar with the scout cab, and I have never tried other tubes. I like the sounds that i can get out the head with the tubes it has. I really like my american jazz bass and my ric 4003 through a boss overdrive pedal through the head. I use a hartke 4x10 and an ampeg 4x10 with a horn and I think it sounds awesome.