When you Rumble 100 Mod is not well planned

[Willie5String]

I decided to mod my Rumble, with a goal of keeping the weight down, and it turned into a major rebuild

I added the Basslite S2012, which sounded good, but then decided that since it was ported, I wanted to move the frequency down to 44 Hz, well to accomplish that I ordered 2 3" flared port tubes from Madisound so that I would not experience port chuffing....then to put the tubes in, I had to remove and remake the baffle board to move the speaker up in the enclosure, to do that I had to replace the grille cloth with mesh and reinforce and line the enclosure.

It sounds great, even the low B sounds pretty good, but, I basically rebought the amp doing the "upgrades", probably would have been way better off buying the 200.

 

[basscooker]

BUT; the build-bug was fed, yes?

 

[Willie5String]

Picture 2 for reference

 

[Willie5String]

BUT; the build-bug was fed, yes?

It was, for now

 

[basscooker]

Haha
Agreed.
It will get hungry again.

Next post by @Willie5String :
"Cloning a Rumble 112 cab"...

 

[G-Dog]

@Willie5String, you should post a link to this thread in the TB Fender Rumble Club thread. I'm sure many of the Rumblers there would love to see it. And you could get a free membership, too.

 

[Phreaky Phriday]

It's way more portable than the 200, right? Thats a big upgrade.

 

[Willie5String]

It's way more portable than the 200, right? Thats a big upgrade.

Yes, with all the changes, I added 1 pound to the weight, so it is still under 25#

 

[Plain Old Barry]

So the original design was properly thought out for what it was meant to be?

 

[Gopherbassist]

What is port chuffing?

 

[David Morison]

Port Chuffing is extraneous noise produced by the ports in a vented cabinet when they are asked to operate at a higher SPL than they were designed to handle. Basically, the speed of the air moving back & forward in the port increases with SPL - depending on a few other factors, this can produce audible "wind" type noise once it gets above a certain speed. Larger ports generally exhibit lower airspeeds, all else being equal.
Upgrading the speaker in an existing design can therefore run into this problem, if the original ports were only sized to handle the expected air movement from the original, lower-spec driver.

 

[dfp]

Before the mod to avoid chuffing (changing tubes, baffle, etc) had you already tested the new tuning and speaker and observed chuffing with your use of the modded combo?

 

[Willie5String]

Before the mod to avoid chuffing (changing tubes, baffle, etc) had you already tested the new tuning and speaker and observed chuffing with your use of the modded combo?

I could hear some chuffing when the amp was dimed, but also the port tubes were set at the wrong frequency.

Short answer:
I could have used 2 3" ABS pipes that were fitted into the existing holes by only drilling out the existing holes about 1/4" larger, but if you know me, you would know that I am a belt and suspenders kind of guy.

Long Answer:

There is a formula that is used to determine the correct area of a port, it is 12 sq in for each Cu Ft of enclosure, the Rumble 100 is about 1.3 Cu Ft (that's what I got from measuring mine). Using the enclosure size and port area, and the Fs of the Basslite S2012, you can determine where to set the depth of the port to get the tuning desired.
In this case, the enclosure was 1.3 cu ft, the port area of 2 ports was 14", Fs of the Basslite S2012 is 46 Hz, I chose 44 Hz. When I did the calculations, the port depth was ideally 9.5". Since the cabinet is 12" deep, you can't have the port tube closer than it's ID from the back wall of the closure, I chose 9.25". I'd have gone a little deeper if I could have as the lowest note on a 5 string bass is 31 Hz, so ideally a great enclosure that works with a 5 string would go down a little below that.

My modded Rumble sounds pretty good dimed, but I would be pretty hesitant to slam the B string as it would overextend the speaker and kill it.