Marshall Cabs Farting Out

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Bad.Seed

Bad.Seed

Well-known member
So, I'm running into an interesting issue with 2 of my Marshall cabs,
One is a 90's JCM 900 cab. The t75's were replaced by k85's by me not long ago, but the cab still sounded farty in the low end, like it wanted to burst apart with palm mutes after the speaker swap.
The other cab is a newer production 1960, with the same T75's.
Both my guitarist and I have been having issues with them sounding like they just can't handle the low frequencies. Neither my guitarist or I use excessive amounts of low end, and both our tones are pretty midrange heavy. We both also use assorted amps, and it happens no matter what amp is brought to practice.
I've pulled my cab apart and tightened down all the screws with force, as every marshall cab I've ever owned needed the speaker and baffle screws tightened somewhat regularly as they seem to like to back out.

Could it be the room? I haven't played a 1960 in my home for an extended period of time, but I just don't remember Marshall cabs sounding this flimsy. Anyone else had this same or similar experience?
 
Do they have a center post? If not, try a 2x2 center post. If so is it secured by a wood screw to the back panel? This can help if you don’t already have it. Another way to focus the sound better, tighter is to add polyfill to the back panel ala Bogner. Sealing up the cab with silicone might help as well; along the front inside perimeter where the baffle is screwed on.
 
I've had speaker cables make me chase goblins.

Did both of these cabs just recently start doing this? Are these crimped connections?
 
Racerxrated said:
Do they have a center post? If not, try a 2x2 center post. If so is it secured by a wood screw to the back panel? This can help if you don’t already have it. Another way to focus the sound better, tighter is to add polyfill to the back panel ala Bogner. Sealing up the cab with silicone might help as well; along the front inside perimeter where the baffle is screwed on
Click to expand...
I know on my cab, I secured the center post with a screw through the back panel.

The Polyfill might be a neat trick, I've truthfully never looked into it. I have 2 Bogner helios cabs, but never tried removing the polyfill to see the difference with and without
 
SpiderWars said:
I've had speaker cables make me chase goblins.

Did both of these cabs just recently start doing this? Are these crimped connections?
Click to expand...
They've been like this for a bit, but it was really starting to get to both of us last practice.
 
When I had a 1960 cab (80's era) the center post came loose a little bit and made the whole thing fart like a truck driver after a stop at Taco Bell.

Open up the back and check to make sure whether it's secure or not. If not, that's likely your issue.

Second thing is the battery trick. It's possible one (or more) of your speakers is not working or are wired out of phase. Since your cab is rear loaded, open the back of the speaker cab. Connect a speaker cable to the cab and touch a 9V battery so that one terminal touches the tip of the cable, and the other terminal touches the ring. Observe the speakers (you'll hear a pop noise). Are they all moving in the same direction (or moving at all?). If there's one or more moving in a different direction, then they're out of phase. If one (or more) doesn't move at all, then it's defective and needs a repair/replacement.
 
EDIT:

Can't hurt to check the things I mentioned in my post above, but the fact that it's two separate cabs in the room makes me think there's something about the room and the resonant frequency where you're palm muting.

Does the fart get worse at a specific frequency? What happens if you let the chord/note ring instead of muting it?
 
dirtyfunkg said:
EDIT:

Can't hurt to check the things I mentioned in my post above, but the fact that it's two separate cabs in the room makes me think there's something about the room and the resonant frequency where you're palm muting.

Does the fart get worse at a specific frequency? What happens if you let the chord/note ring instead of muting it?
Click to expand...
It's really just in the palm mutes where it sounds like the cab is flexing, almost like there is breakup in the speakers but it's just the cab frequencies not getting along with something.
 
I’m not at all a tech savvy guy, but can just add that my Ubercab had the same issue for a bit (and it has polyfil in the back, so probably won’t solve your issue), but I took it to my local tech and was a quick, cheap fix for me, but not sure what he did exactly. It’s been totally solid for years now though since then

From what I can tell, polyfil seems like it can make things sound bigger and tighter, but the overall sound will be smoother, more homogenous and polished and not as lively or exciting in some ways as would be without the polyfil, so I guess there are trade offs with both styles
 
like others have mentioned the loose center post needed some beefing up in one of my 1960 cabs.. never had a problem since.
 
Could just be the baffle construction on those cabs (floating/screwed in vs. fixed/glued in, like Mesa).
 
braintheory said:
I’m not at all a tech savvy guy, but can just add that my Ubercab had the same issue for a bit (and it has polyfil in the back, so probably won’t solve your issue), but I took it to my local tech and was a quick, cheap fix for me, but not sure what he did exactly. It’s been totally solid for years now though since then

From what I can tell, polyfil seems like it can make things sound bigger and tighter, but the overall sound will be smoother, more homogenous and polished and not as lively or exciting in some ways as would be without the polyfil, so I guess there are trade offs with both styles
Click to expand...
That's what I've always gathered about polyfill, which is why I've never tried it.

Truthfully, the Uberkab I had sounded dead and dull, so I traded it for a Helios ST 412 and couldn't be happier with the trade. The Helios sounds huge yet still bright enough to sit in the mix right. It seems very well balanced and I really dig it.
 
This might sound counterintuitive, but since you said your tones tend to be more mid range heavy it made me think of it. Have you tried dropping the mids and increasing the bass and/or depth a bit? For us guitar players we typically think when a cab is flubbing out it’s always due to the bass, so we end up dropping the bass and/or increasing mids. While that may often be the correct course of action, that can actually make it worse if the bass isn’t the culprit. I’ve experienced a number of times a cab flubbing out because the EQ wasn’t balanced correctly and the mids were actually hitting too hard. Then once the mids were dropped a little and the low end increased, things balanced out and it wasn’t flubbing out anymore. The room can play tricks on your ears with this as well, so you may need to check it with a mic to see if it works or not.
That aside, there could be air leakage around the
baffle that tightening down didn’t fix. Also, check to make sure your speaker frames aren’t bent or cranked down too much as those can cause issues too.
 
Bad.Seed said:
That's what I've always gathered about polyfill, which is why I've never tried it.

Truthfully, the Uberkab I had sounded dead and dull, so I traded it for a Helios ST 412 and couldn't be happier with the trade. The Helios sounds huge yet still bright enough to sit in the mix right. It seems very well balanced and I really dig it.
Click to expand...
Was your Ubercab front or rear loaded? Mine is front loaded, but it defintiely is a very dark sounding cab, so it can come off that way in comparisons, but I like how big and fat it sounds while also being very tight, but most of the time is like you said too dull and smooth sounding for my taste, but I’ve kept it still. It needs extra aggressive speakers in it to shine. The Kerry Wright 412 is my best cab, like a much better version of most Marshall cabs and my Diezel 412 I like a little more than the Ubercab, but not my favorite. They all have qualities though that made me hang on to them for now. My friend actually got very good results in his re-amping with my Ubercab, but the results with my KW were light years ahead
 
Bad.Seed said:
So, I'm running into an interesting issue with 2 of my Marshall cabs,
One is a 90's JCM 900 cab. The t75's were replaced by k85's by me not long ago, but the cab still sounded farty in the low end, like it wanted to burst apart with palm mutes after the speaker swap.
The other cab is a newer production 1960, with the same T75's.
Both my guitarist and I have been having issues with them sounding like they just can't handle the low frequencies. Neither my guitarist or I use excessive amounts of low end, and both our tones are pretty midrange heavy. We both also use assorted amps, and it happens no matter what amp is brought to practice.
I've pulled my cab apart and tightened down all the screws with force, as every marshall cab I've ever owned needed the speaker and baffle screws tightened somewhat regularly as they seem to like to back out.

Could it be the room? I haven't played a 1960 in my home for an extended period of time, but I just don't remember Marshall cabs sounding this flimsy. Anyone else had this same or similar experience?
Click to expand...
Well first of all, the k85s are garbage. Second of all, my Marshall BV cab ( which is the same as the 1960 cabs or jcm900 cabs or whatever you wanna call them) has better low end than my Mesa OS, without becoming farty, with amps that have arguably the thickest and deep low end on the planet ( Diezel herbert, Mesa rev F, Bogner Uberschall, driftwood purple nightmare). While the GT75s are super thick ( and scooped for sure) and have decent midrange, their overbearing low mids and low end can extend way too much with some amps. Low midrange and even middy mids can give the sensation of flabby and flubbiness due to the transients in your playing as well.

but ya know, what do I know, im no youtuber like you and reza, I’m sure you’ll figure it out. Maybe ask Glenn fricker?
 
Have you tried different speakers, other than the 2 mentioned, in that cab?
I've bought a pair of 80's Silver Jubilee 4x12s, same year, both straight. One of them(cabinet 1) sounded incredible tight, with a lot of low end punch and midrange definition. The other one(cabinet 2), was a lot darker sounding, and it didn't have as much clarity as the cabinet 1. It also had more low end, but it was a bloated type of low end, that would never get tight and defined when palm-muting. Cabinet 2 sounded better if playing open cords with low to mid gain style, but had absolutely no clarity nor low end punch with high gain heads.
Opened the cabinets and switched the speakers, and sure enough, the issue followed the speakers.
Cabinet 1 had V30s and cabinet 2 had G-75T.
What I'm trying to say is that, while you're trying to fix the cab, there is a possibility that your issue is the speaker instead.
 
Yup, I'm thinking its the speakers as well.
Take the 2 v30's and 2 greenbacks out of the Helios cab and try 'em in the Marshall cabs, and you'll know for sure.
 
fusedbrain said:
Yup, I'm thinking its the speakers as well.
Take the 2 v30's and 2 greenbacks out of the Helios cab and try 'em in the Marshall cabs, and you'll know for sure.
Click to expand...
I had the k85s in the old peavey Butcher cab prior and they sounded incredibly tight and punchy with no woof in that cab, so I really think it's the cab that is the issue. On the other hand, I put the 75's in an old yamaha cab and they sound fine in there, but I still don't love them. But no fart or breakup from the cab. So either it's the cab itself, or the room it's in at this point.
 
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