Help with resonance issue.

[DaveSwenson]

A friend is about to head out on tour and is having a problem.

it's a dual rectifier head through a dual rec cab with vintage 30s.
Basically, with the bass, mid and treble all at 12 o' clock, whenever A 440 is palm muted, i.e the open A string or 5th fret on the E string, there's an INSANE amount of low end resonance that i measured at around 100Hz. It completely swamps everything in the room. I tried multiple guitars, so it's that's not it...


Any ideas?

 

[domct203]

Have you tried turning down the bass, and turning up the treble & presence?

Is this a new problem that just surfaced? Recto's are very bottom heavy.

You could also throw a parametric EQ in the FX loop and notch out around 100hZ to see if that helps.

Dom

 

[screamingdaisy]

1) Try turning down the bass knob.

2) Try moving it around the room. If I remember a cab in the centre of the room has no bass boost while a cab placed against a wall will double the low end and in a corner will quadruple it.

3) If the cab sitting down on a hollow floor it'll couple with the floor and turn the floor into a woofer. Try uncoupling the cab from the floor by putting it up on it's casters, or up on top of a road case.

4) Try turning down the bass knob.

 

[knotts]

Is the reverb on at all by any chance? My Lonestar would do a strange similar thing when I hit a G on the 3rd fret of my Low E string on my clean channels; crazy kind of springs vibrating against each other (never figured out what it was). I wonder if with distortion in manifests itself as you've described.

 

[vick1000]

If the cabs not on casters, add them, or get it off the floor on some small blocks, etc...

 

[DaveSwenson]

Thanks for all the ideas. This friend has about 30 years of experience as a player and sound tech. He's baffled so the amp is heading to the tech. Hopefully it's something simple.

 

[afu]

My cab does it at 120 Hz. I put on permanent casters to help. A foam pad along the bottom helps if I need it on my hard floors. I have to be careful with the bass knob if I don't want to make Ba'al Zeebub's bowel sounds.

What kind of settings are being used?

For mine, tube rec + Vintage + bass @ noon = WHUMP!

 

[Given To Fly]

A friend is about to head out on tour and is having a problem.

it's a dual rectifier head through a dual rec cab with vintage 30s.
Basically, with the bass, mid and treble all at 12 o' clock, whenever A 440 is palm muted, i.e the open A string or 5th fret on the E string, there's an INSANE amount of low end resonance that i measured at around 100Hz. It completely swamps everything in the room. I tried multiple guitars, so it's that's not it...


Any ideas?

A=440Hz is on the 1st string, 5th fret.

What kind of room were you in when you measured the resonance? If it was a smaller room, try the biggest room available. I think the resonance is an "acoustics" problem but if the resonance is still overpowering the room than I'm at a loss and should be "tarred and feathered." :shock:

 

[3124+]

bad filter caps

 

[UnderJollyRoger]

I experienced this behaviour first at home while recording something via Ampsims ... depending on what I use, the palm mutings around the same frequency (well, a little higher but in the same region) were really louder than the rest ... nowadays I tamed it with a Multiband Compressor and a little bit of EQ ...

With the real amp, it's more or less the same ... depending on the guitar, the gain setting (more gain = more resonance) etc. ... but I always had problems just dialing it out with a normal Guitar EQ, because the Bass pot seems to be set lower than the troubling frequency ... I would have to cut just too much Bass until reaching the resonating frequency ... btw., this shows that the lower Bass regions in an electric guitar are not the important ones ... the real power and frequency information is a little bit higher, somewhere between 100 and 200 probably.

Your problem might be something different, but just saying ... 8)

 

[bandit2013]

I do not believe it is the amp that is the cause. If your friend has the oversized cabinet that may do it. My first Recto cab was problematic in that nature while palm muting. At the time I was using a Mark IV and bought both of them together 15 years ago. Since the Mark IV was a combo I did not use the 412 cab all that much. It was far worse with the Mark V. I had recently transplanted the original V30 into a traditional sized cabinet and was amazed on the difference that made. I now have another standard Mesa Recto 412 cab (the oversized one) which does not exhibit the flub or low resonance drone. I have not checked the speakers of the new Mesa cabinet as I assume they are V30 (ordered it though sweetwater). I could pull one of the handles off or perhaps the jack plate but prefer not to break the seal at this time since the cabinet sounds terrific.

One could rule out the amp if the cabinet does the same thing with a different amp hooked up to it at the same note as you described.

 

[jbird]

I once had one of the speaker wires of one speaker in my old recto 4x12 cab vibrate loose/off, and it sounded farty like a blown speaker! Could this be the problem?

 

[bandit2013]

Dropping one of the speakers in a 412 cab would result in change in total impedance. Instead of 8 ohm load you will wind up with 12 ohms since the Mesa cabs are wired parallel/series. Left side is parallel, right side is parallel and both sides are connected in series. This would be the case with the stereo split and mono jack arrangement. If the cab was wired series/parallel, losing one speaker would take out one side completely and wind up with 16 ohms. I doubt that would result in fart like tone. The oversized Recto cabinet has a different resonant frequency than say a traditional size cabinet. I was amazed when I transplanted the V30s from the old OS cab to a traditional size cab (non-mesa branded cab with Celestion 16 ohm elite speakers which had too much mids and the smallest ceramic magnets). The same speakers that would flub out easily were tamed in the smaller enclosure. Flub was gone as was the horn like sound at the same frequency as described in the original post. Interesting to note: I did buy another OS Recto cab last year and for some reason it does not have the same characteristic issues as the 15 year old cabinet. I am tempted to remove one of the handles to take a look inside with a flashlight. Does it even have V30? The new cabinet sounds amazing compared to the old one when it had the V30's in it. I even tried it with the Mark IV which was prone to flubbing the original cab with ease as well as the MC90 which gave up its voice coil a few years ago.

One thing I did notice, with the steel frame of the V30 (and MC90) speaker, if there is too much torque applied to the 4 bolts, the speaker cone will warp when mounted improperly since the foam gasket will push against the areas of the rim that have no screws. This will cause it to sound as if the voice coil is damaged. One way to avoid bending the outer ring of the metal basket is to install small spacers on the mounting bolts that will allow compression of the gasket but will prevent bending of the basket when tightening the nuts. I noticed this when I attempted to reinstall the MC90 that came with the Mark V combo shell.

One other thing, if the cab leaks air it will make some strange sounds, vibrate, or sound terrible with low frequencies since there is more travel of the speaker. V30's do not sound all that good with a vented, ported cabinet unless it is tuned properly. I have tried a V30 in a sealed extension cab with the back panel removed and thought the speaker was toast. All it did was flub such that I thought the cone was going to tear itself apart. However, when I sealed the back it sounded awesome. At one point I was tempted to rip the cones out by stabbing it with a large screwdriver and taking out some frustration with a sledge hammer on the magnet. I am glad that I did not do this and found use for them in a traditional sized 412. Now V30 has become one of my favorite speakers.

There may be one trick one could do to change the resonance of the oversized cab, add a 2x4 on top of the center post inside the cabinet. If I ever remove the EV speakers from the old OS 412 cab I may do this since I kept the original center post that I added a 2x4 to it. I replaced the original post with a new one since I had vibration issues with the EV speaker. Just a simple mod changed the resonance of the OS cab dramatically.