Abe, above mentioned this helpful hint he got straight from celestion.
I own a ROV series 2 combo and recently purchased a recto 2x12 cab to use along with it. I dont gig out ever so I cant play at extreme levels often, but once in a while when the house is empty I open it up and found that my cab also had that farting sound people keep talking about.Mind you I got that farting sound while playing no higher than half way up especially playing clean, open or barre chords. I didnt really think anything was wrong with it and I knew the cab can handle my ROV. I thought about returning it but this afternoon I saw my neighbor leave,,I live in a townhouse, and poked my head out of the basement door to warn my wife and spent the next half hour doing what celestion said to do. After giving it a break for a while I went back to test her out and no bullshit,,there is no more farting sound,,I cant get it to fart out at all on any guitar I have..I cant say that I notice much of a difference in the actual sound at all,,but like I said,,no more farting out..I am now able to crank it to about 90% and it sounds sharp.
Try it out,,and good luck, P.S. I was a bit wary at first when raising the volume with the bass so high but I believe thats what really does it for the speakers. I couldnt see the actual speakers but from the feel of it,,they were really moving.
I hope that this is helpful. It comes right from Celestion's site:
http://professional.celestion.com/guitar/features/drdecibel/index.asp
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How do I break in my speakers?
Important Note! Before breaking it in it's advisable to "warm up" the speaker gently for a few minutes with low-level playing or background hum.
Break in a speaker with a fat, clean tone: turn up the power amp volume to full, and control the level with the preamp gain. Use a level that will be quite loud, but not painful in a normal size room.
Have the bass and mid up full, and the treble at least half. On your guitar, use the middle pick up position (if your guitar has more than one pick up) and play for 10-15 minutes using lots of open chords, and chunky percussive playing. This will get the cone moving, and should excite all the cone modes and get everything to settle in nicely. The speaker will continue to mature over the years, but this will get it 95% of the way to tonal perfection in the shortest time