So I have a older Peavey 412M (pre-Sheffield) cab which last night during a recording session (and actually rehearsal the week before), was having some problems with the upper right hand Celestion G12K-85 speaker farting out on the clean channel, at first I lowered the bass and that fixed it. The amp is a Bugera 333XL, and while recording cleans we swapped to the other guitarist's Marshall cab and had absolutely no problems.

Now, I have a few questions

1) Would it be okay to substitute the "farting" speaker with an Eminence out of my Line6 1X12 cabinet for the time being just to get rid of the noise?

2) I noticed a very noticeable volume difference between the Marshall and the Peavey cabinets. The Marshall is a lot louder than my 412M, not sure if it's the speaker difference (I think the Marshall has greenbacks in it), construction, or if there is more going on with the Peavey than I thought.

3) Would mixing in the modern equivalent (Celestion G12K-100) in with the 85's harm anything? I've heard the 100's are the same as the 85's but I'm not sure....I could also nab another (or even a set) of spare 85s off of ebay eventually.

Still have a little more diagnosis to do (ie, need to figure out if it's cab vibrations causing my input jacks to rattle, I have a little modification I plan to do to the Bugera to make input jack replacement easier and faster, and replace the jacks with stronger vintage-style metal jacks as found in old Fender amps from the 60's).

Either way, need to get the cabinet going, I have a gig at a major local festival coming up in 2 weeks + 2 gigs before that including one on Saturday. Can't really afford new speaker(s) at the moment so I got to make do with what I have available.
My Current Mains
- 1996 Fender Jag-Stang with EMG Pickups
- 1998 Fender Jaguar with Cool Rails
- 1982 Hondo Paul Dean II (DiMarzio Super II X2)
- 2010 "Fender" Jazzmaster (Home built)
- 2013 Squier VM Bass VI (stock)
1. It would be okay if the speaker is the same impedance (8 ohm, 16 ohm?) as the others.

2. Construction differences that would make a sonic difference are unlikely between Peavey and Marshall 4x12 cabinets. It's probably the speakers.

3. Again, impedance is the first issue. After that, power handling and efficiency are important.

It may be worth putting a dish in the back that would accept Speakon connectors in addition to 1/4" jacks. Most pro audio has already gone this direction. Much more positive connection, very unlikely that vibration will cause problems.