cabinet tweaking

[antichef]

I have a Marshall JCM900 series 1960B cabinet that I'm not in love with - it has the stock speakers, and I want to replace some or all of them. But before that, I have to face the fact that the cabinet itself is troublesome - it has a somewhat tubby bass-y sound when compared to some other cabinets I have (including a JCM800 1960A that has the same type of speakers), and at first it had some rattles. I fixed the rattles by taking it apart, removing some of the internal bracing, and putting leather and felt (depending on what I could get to fit) on the ends of the bracing and putting it back in place.

But the tubbiness is still an issue. I just had some insulation work done, and I have some spare scraps of Owens Corning 703. Is it worth my time to try to treat the bass issue by putting some of that inside the cabinet? If so, do you have any tips on how/where to put it in place?

 

[Phrasemaker]

Personally I'd decide on the drivers you're going to use, fit them and play them in before doing anything major to the cabinet. Speakers all have their own characteristics which can alter over time. A new set of cones might well deliver a tighter bass due to their type or the fact that their is greater stiffness in their edges where they are designed to perform a piston movement at lower frequencies.
I reloaded a 4x12 cab last year and was initially disappointed with the low end or seeming lack of it. Once I'd thrashed the cones for a couple of weeks they improved a whole lot.
So maybe see where you're at with the new drivers first.

Regards

Tim

 

[Greg_L]

I have a Marshall JCM900 series 1960B cabinet that I'm not in love with - it has the stock speakers, and I want to replace some or all of them. But before that, I have to face the fact that the cabinet itself is troublesome - it has a somewhat tubby bass-y sound when compared to some other cabinets I have (including a JCM800 1960A that has the same type of speakers), and at first it had some rattles. I fixed the rattles by taking it apart, removing some of the internal bracing, and putting leather and felt (depending on what I could get to fit) on the ends of the bracing and putting it back in place.

But the tubbiness is still an issue. I just had some insulation work done, and I have some spare scraps of Owens Corning 703. Is it worth my time to try to treat the bass issue by putting some of that inside the cabinet? If so, do you have any tips on how/where to put it in place?

That JCM 800 cab is probably all plywood, while the 900 era cab may have an MDF back board. Making a birch plywood backing board could help. Make sure that center brace is tight, secure, and bumps up hard against the back panel. The felt trick is good. Many of the old Fender cabs were stuffed with stuff, but I've personally never heard of it being useful with the big Marshall cabs. Wouldn't hurt to try it I guess. I think just a speaker swap and/or new back panel will take care of it.

And it could just be how those speakers interact with that cab. A speaker upgrade is never a bad idea, and tons of speakers are an upgrade over 75s. They're not bad speakers, they just aren't great. You need some G12-65s. Everyone does.