Floor vs. Wall Mounted Reverb Pans???

[Mango Moon]

Hello All,

I've got a quick question on the variable mounting styles for reverb pans, especially for those of you familiar with the Fender '63 Reissue Outboard Reverb Tank . . .

I own several combo amps with reverb, and without exception, all have their reverb pans mounted securely on the floor, and they work just fine, yet the Fender '63 Reissue outboard reverb tanks all have their pans loosely suspended from the wall (not the floor) by four springs.

As anyone who has used one of these knows, these things are exceedingly fragile, especially when powered-up, because any movement of the tank, no matter how slight, causes the 'suspended' pan to move freely, which in-turn causes the springs inside to swing excessively and in some cases to crash. And if the thing has signal of any volume traveling through it at the time, its not a pleasant experience!

Although it is true that Accutronics, Gibbs and other reverb manufacturer's recommend wall mounts over floor mounts, when I have contacted them, they have not been able to explain the need for this 'suspended' approach to mounting the pan. So the question is, why? Why did Fender choose to mount these Accutronics 4AB3C1C reverb pans in this way? Why aren't they 'fixed' or fastened securely to the wall to prevent excessive motion like any other reverb pan would be?

Does anyone have an answer on this?

[Tom Phillips]

I'll offer a few comments.
1. The outboard Fender reverb was their first reverb product.
2. The form factor of the cabinet probably influenced the mounting of components.
3. The original unit had a lockdown mechanism for transport and the external spring suspension was an integral part of that mechanism.
4. The tanks in combo amps are usually not firmly screwed down to the cabinet floor. Fender usually puts them loosely in a bag. This helps reduce acoustic & mechanical vibration coupling to the tank.
5. If a "wall mounted" tank crashes too easily, then the suspension springs probably need to be adjusted. (Could be internal or external springs needing adjustment) The tanks are actually available under unique part numbers for different mounting configurations. The difference is the rigging of the internal suspension springs and that can be changed in the field with a little effort. Because of this, you won't have the optimum suspension if you just move the position of a given tank without adjusting the internal spring attach points. Most vendors don't stock all the possible tank configurations.

Got to run.
Regards,
Tom

[Mango Moon]

Tom,

Thanks for the feedback, but I'm afraid this still hasn't answered the central question for me. Regardless of spring tensions, etc., why (on the outboard tanks alone) does the entire pan need to be suspended (free-floating on springs), as much as 1/2" away from the wall itself?

In other words, since the internal springs themselves (which free-float inside the external pan) are what actually creates the reverb effect, why can't the external pan be fixed to the surface rather than having both the pan and the internal springs free-floating? I don't know any better way to articulate it.

Also, I'll reiterate that of the three combo amps that I currently own with factory reverbs installed (i.e., a '62 Magnatone 480, a '65 Reissue Fender Deluxe Reverb, and a 2003 Gomez G-Reverb), all have 'immobile' reverb pans (i.e., they are permanently 'fixed' to the surface with screws, no springs, no bushings, no nothing).

[52 Bill]

...why (on the outboard tanks alone) does the entire pan need to be suspended (free-floating on springs), as much as 1/2" away from the wall itself?

I think Tom answered this for you, it is part of the traveling lockdown system. The major problem with all mechanical reverb tanks is that they are fragile in nature and do not travel well. They have gotten better through the years, but they still are the weak link in the chain.

If you look at the tank system, there is a foam pad mounted on the front wall inside the tank. When the tank is unlocked, the springs are loose and free to work as they were designed to work. When the tank is locked down for traveling, the springs are pushed into this foam pad to help keep them from being damaged while the unit is being thrown in and out of the van by the roadies.

The 4 suspension springs that you are wondering about allow for the tank to be pushed into and released from the foam pad.

[Mango Moon]

O.K., O.K., thanks Bill! I feel kinda like the idiot GEICO caveman at the Billy Jean tennis tournament where he says:

"I get it, I get it . . . I quit, but I get it!"

I was looking into this far too deeply. I was expecting a sonic or 'electronic' explanation as to why Fender did it (something related to the sound), when there never was an electronic reason. In other words, the only reason for having the pan suspended so, is for travel, period. Got it!

So, if you're a studio-based player (like me), you don't need to have it suspended (i.e., the pan can be secured tightly to the wall or floor), and that's precisely the answer I was looking for, because now (and don't share my pending patent on this with anyone - yuck-yuck), I can put a securely wall-mounted 2-spring unit and a securely floor-mounted 3-spring unit all in the same box, and switch between them at-will with a common RCA cable. I've just gotta figure out a way to make the floor-mounted pan (the 3-spring) clear the lone 6V6 tube.

God is 'good' Sabu!

Thanks guys!

[Enzo]

SOME reverb pans are screwed down tight to the wood, but most of them are mounted either in a bag or at least there are four very soft grommets allowing the pan to be cushioned.

If you crank a pan down tight to the wood, the wood then becomes a sounding board and can transmit sound energy into the pan. You really don't want the vibration from speakers being channeled back into the pan. That causes reverb feedback and other undesirable things.

A reverb pan should be mounted securely enough to stay in place, but should be able to float.

[Steve Conner]

In a system like this, every stage of vibration isolation helps. A "stage" of isolation is a mass dangling on a spring, so an Accutronics tank screwed firmly to the cabinet has one stage, and the same tank dangling on yet another set of springs has two stages.

I recently built a combo with reverb, and I screwed the pan to the floor, in a vinyl bag with grommets on the screws, so I guess the grommets make one and a half stages. I set up the recovery gain so it barely feeds back with the reverb maxed, and it seems to give plenty of 'verb.

Fender would have used the two-stage isolation in their standalone reverb because they had more room inside the thing than there is in a combo.

Of course, these systems are designed to stop vibrations in the audible range from causing reverb feedback. The optimal isolation for that is a heavy mass and a limp spring. But as any spring reverb owner knows, that actually makes subsonic vibrations worse, ie, it's a recipe for disaster if you move or shake the thing!

That's just the way spring reverb is, it's not designed to work while riding down stairs on a skateboard.

[jrfrond]

The suspension is just an extra measure of acoustic decoupling. In a head/cabinet system, you could probably get away with solid mounting. In a combo, you need all the help you can get, which is why they are generally mounted in a bag or with rubber isolation washers.

Here's a little hint: I have found that the pan case design itself can lead to excessive howling due to sympathetic resonance. When mounting an Accutronics pan, pull the sides out a bit so that the corner edges do not touch. It will break up the standing wave in the walls of the pan, and increase isolation dramatically.

As to wall vs. floor-mounted pans, it really does not make a difference, but there IS an Accutronics spec that changes the spring tension depending on which method you choose. The last letter corresponds to this as follows:

A = Horizontal, open side up
B = Horizontal, open side down
C = Vertical, connectors up
D = Vertical, connectors down
E = On End, input up
F = One End, output up

C through F correspond to wall-mount.

[TD_Madden]

Slightly off-topic......

I had a buddy in high-school ('72) whose mom's old car had a radio with reverb...you could make it crash by hitting potholes. I forget the car-maker, but the rear-window of that big sedan was also electrically powered..

[Mango Moon]

Thanks guys.

I was (and am) aware of the alphabetic coding for these things based on mounting position and RCA location, but I've gotta wonder about this business of variable 'spring tension' based on same. It makes sense to me that a wall-mounted pan (especially one suspended away from the surface) might be able to get away with slightly softer springs, but acoustically speaking, I'm not sure how it would matter.

As for expectations of use while "riding down stairs on a skateboard"? Mmmm, not even close! The two units I have will damn near crash if someone simply breathes on them! That's how absurdly sensitive they are, and I'm not alone. I've seen a number of instrumental surf bands perform live over the years and they've had some of the very same problems. On one occasion, it was downright apocalyptic! You'd have thought someone had detonated a 100-megaton nuke on-stage. NOTE: You don't see Dick Dale (at 120-130dB) playing these silly little things - at least not un-modified!

And lastly, using the Fender Deluxe Reverb, Super Reverb and several other reverb combos as an example, I'll argue that there's still no significant rationale for suspending (isolating) the pan up and away from the surface, when those amps all have more room inside them than the standalone box has, and all have their reverb pans placed firmly (immovably) into a vinyl bag that is then tightly secured to the floor at both ends by screws. In other words, they could have easily installed the pans in those amps up and away from the surface just as they have the '63 reissue standalone reverb tanks, but they didn't.

[Tom Phillips]

...And lastly, using the Fender Deluxe Reverb, Super Reverb and several other reverb combos as an example, ... all have their reverb pans placed firmly (immovably) into a vinyl bag that is then tightly secured to the floor at both ends by screws...

I submit that the bag mounting method is NOT "firmly (immovably)" mounted.
By that statement I originally thought you meant that the tank was screwed directly to the wood.

[Mango Moon]

Tom,

Thanks for your response and I think this topic has probably been beat-up enough at this point, but I'll close by saying that on my older Magnatone amp the pan is indeed attached directly to the wood on the floorboard by screws, without a vinyl bag or any covering, and the screws travel through small, black rubber grommets which essentially isolate the pan from the wood of the floorboard, but only slightly in my view. In fact, from the standpoint of independent movement from the cabinet, there is arguably none. If anything, it serves as an electrical (not physical) isolation.

Conversely, in the case my Fender units, which are all 'factory' (i.e., they're un-modified), the metal reverb pan is held unattached but tightly inside a vinyl bag, and the attachment screws pass through the edges of that bag only, not through reverb pan itself. Thus, in theory the pan is free to move inside that bag, but in practice, it ain't happenin' - its just too tight to move.

Thanks again everyone.

[Enzo]

Mango, it is not about the pan being able to move around in the bag, it is to prevent speaker vibration from getting to the long springs inside the pan. Wrapping the pan in the bag keeps air vibrations reduced, and it is also a cushion bewteen the cab wood and the metal pan. I agree the pan can't move around once crammed in the bag, but that was never the point of the bag.

You will also often find a piece fo cardboard cut to cover the open side of the pan and taped to it while inside the bag. This is further efforc to keep accoustic energy off the long springs.

Johns idea of spreading the corners of he pan walls is good. I dampen the metal with weather stripping, which is something the factory does as well. A long strip of self adhesive weather stripping foam stick along the top wide surgace of the pan prevents it from resonating and ringing.

The rubber gromments all there is between pan and bottom? On some amps that is the case. Cushions it only slightly it seems to you. Well, sometimes slightly is the difference between howling reverb and one that behaves. AMps are not all the same. In some models, there is not a large sonic reverb feedback issue, so if they can save the expense of a vinyl bag or extra assembly step, they do it that way.

I can tell you I have had to add these countermeasures to some amps that had a plain old bare reverb pan screwed down to the wood directly just because the damned thing WAS feeding back.

[Mango Moon]

Enzo,

Yup, you're exactly right on the cardboard insert - my Fenders all have such a cardboard piece inside the vinyl bag, and all seem to work just fine with no excessive vibrations, feedback, etc. In fact, they all sound great. Some are two-spring units, some three. The lone Magnatone is another story though. Its got no bag, no cardboard, no nothin', just bolted straight to the floor with grommets, but then the reverb effect is rather poor on that particular amp anyway, so its no big loss.

I like your suggested weather stripping idea. In fact, I've done something similar with the noisy, crash-prone standalone tank. Just finished it this afternoon. I put the pan in a vinyl reverb bag with cardboard insert and then I attached the bag to the floor using two, six-inch strips of velcro on each side (four total). It effectively raised it up off of the floor and now works like a charm with no unexpected or unwarranted crashing. Works for me.

Thanks for the feedback!

[Enzo]

The weatherstripping idea is not mine, I see it on commercial amp reverb pans, but it is also a trick automakers learned long ago. They glue long stripes of rubber on the inside surface of large body panels so they don;t make sheet metal noises as you drive around. A stripe of weatherstripping foam rubber glued down the center of the wide top face of a reverb pan prevents it from resonating.