This must be a touchy subject!

WHY would you want to do that in the first place? Most cabs already have some sort of insulation installed by the manufacturer, in order to control standing wave resonances. Notice that I said "control" not "eliminate".
From a technical standpoint, you're dealing with a specific air space containing specifically-designed drivers to deliver a specific range of frequencies. If I say "specific" one more time...
When you shove a bunch of sound-deadening insulation into the cabinet, you are:
(A) Changing the back pressure on the speaker cones, conceivably damaging them (in extreme cases). You're not letting them "breathe"...
(B) You are changing the resonance point of the cabinet, which may or may not suck the tone right outta the cab.
I ran across an old Marshall 8x10 GUITAR cabinet that an old high school
buddy bought in England, brand new, in 1971. His parents were loaded, they paid to have it shipped back to the States, along with the 50-watt TREMOLO head he bought with it. Anyway, a couple of years ago, he brought the cab to me to check it out; one of the old Celestions was buzzing. He swore to me that NOBODY had ever opened the cabinet up.
When I did, I was floored-there was NO insulation in the damned thing-NONE!! I have since learned that there were many Marshall cabs with NO insulation in them! That resonance is what made them so desireable...

My cabinet has no insulation in it. It also is divided in 2 cavities on the inside. I thought all cabinets were hollow.

Every manufacturer has their own take on how cabinet construction is approached. While dimensions are similar, most of the additions such as insulation and boards to separate the speakers, are simply particular to each builder. Sometesting may have gone on in an early stage of cabinet development but most often its simply "how we do things" that apply.

I have a LOT of experience with cabinets of all sorts, and I have never personally seen a 4-12 cabinet with a divider that was anything more than a point of contact for screwing the back on securely. Unlike a cabinet similar to an SVT 8-10, which has a completely sealed compartment for every 2 speakers, every 4-12 cabinet I have been inside of is mostly open. Though a screw point divider will affect the sound somewhat, its mainly there to support the large area of the back from flexing and rattling at high db's.

This isnt to say that your cabinet is completely sealed into two separate chambers.....this is only to say I havent seen this and from what I know about 4-12's, it wouldnt be in the sonic interest of a 4-12 cabinet to do so.

In answer to your question, stuffing your cabinet full of insulation will be as Moon said, and why would you want to do this???

If you are trying to get it to play quieter then you need to look elsewhere to solve this problem. Turning down is always an option.

BTW...Most of the 4-12 cabinets I have seen that had insulation in them were made of inferior quality plywood or pressboard and needed the insulation to dampen the BAD frequencies. Marshalls do not have insulation in them if they are the high-end veneer woods. It IS the resonance that makes the older ones sound like they do.

For those who havent experienced these, the oldest Marshall cabinets came with vents in the back, making them effectively an open-back design. With the advent of higher power they closed the backs in order to save the speakers from destruction.

I believe mine is sealed. The one thing I notice is that it doesn't bottom out at high volume. It's amazing that i've been playing guitar for so long and still don't know shit about them. I use my ears rather than searching for buying gear. Everyone keeps questioning why I'd want to stuff the cab. But I just want to know how it will colour the sound. Maybe a better question is : How can you alter a cabinet to change its tonal characteristics? I once heard of screwing plex-glass over 3 of the 4 speakers to get a natural compression. Never tried it, sounds sketchy.

Plexiglass? Hmm, I think you're right about the "sketchy" part. Can't imagine that ever sounding remotely decent.

I know of several people who have put tape (I don't know what kind, probably electrical tape or masking tape) on the grille cloth of their cabs covering up the approximate location of the center of the speaker cones. It sounded awesome. Really got rid of some of the extra sharpness that was coming out of their cabinets (I think they all had Marshalls, which yes, already sound good.)

Why don't you just try Einstein.

Take your comforter an stuff it into the back of your amp and test what happens. Its not like its gonna catch fire or anything.

Stuffing a sealed speaker cabinet is done in order to minimize standing waves. Generally, guitar cabinets with guitar drivers do not require any stuffing. Using stuffing in an attempt to modify the tone of a guitar cabinet would be a bad idea, because it will make the cabinet sound worse, not better.

Sealed cabinets rely on the volume (size of the space) within the cabinet for it's particular speakers, and therefore its resonance. If you stuff it with any form of dampening material (fiberglass being the most common), you change it's resonant frequency, its projection, while rolling off the lows more gently, and subduing the highs from the cabinet (part of its projected "sound"). It will basically sound choked and muffled.

It's any easy experiment, however, if the back comes off. Otherwise you must remove a speaker or two to install the "stuffing." It is a worthy experiment, if for no other reason than to train your ear to hear such differences, if you're willing to do it. I can almost guarantee you'll be removing whatever you put in your cab though! It just won't have the same energy or sound when stuffed. It may, however, improve bass, if you plan to use it for it's original purpose - for bass guitar.

If you're game, give it a try and report your findings here. :wink:

tifftunes ... stuffing changing resonance frequency is a wives' tale, stuffing a cabinet will not change the sensitivity or dispersion of the cabinet (projection). and it will not roll off the lows any differently than unstuffed. The low freq roll-off is strictly determined by the T/S specs of the driver in relation to the cabinet volume. And, NO, stuffing DOES NOT increase the apparent volume of the cabinet as "seen" by the drivers (another wives' tale).

SonOfSmawg wrote: tifftunes ... stuffing changing resonance frequency is a wives' tale, stuffing a cabinet will not change the sensitivity or dispersion of the cabinet (projection). and it will not roll off the lows any differently than unstuffed. The low freq roll-off is strictly determined by the T/S specs of the driver in relation to the cabinet volume. And, NO, stuffing DOES NOT increase the apparent volume of the cabinet as "seen" by the drivers (another wives' tale).

I should revisit old posts more frequently... I've been remiss in my attentions of late.

My previous post is accurate and correct. And, I've never heard anyone's wives speak of such a subject...

I suspect your experience in this area is severely limited, based upon your comments. My experience, however, is years of actual testing, and experimentation, designing and building, aided by CAD software (written by and for a major driver manufacturer - Eminence). I have been using my own cabinets (designed and built by me) for nearly a decade now. I've built hundreds...

Stuffing a cabinet will not, as you pointed out, change a driver's sensitivity, or be effected by a driver's sensitivity. Driver sensitivity is irrelevant to this discussion.

Everything else you said is indeed inaccurate and/or incorrect.

Pardon the extra cheeky response from me. But the righteous, mightier than thou attitude you project is definitely undeserved, and unappreciated. “Mind your own business” comes to mind. And speaker cabinets (or at least understanding how the work) do not appear to be your business.

This sort of ill-informed and rudely-delivered commentary is one of the main reasons I rarely come to RO anymore.

If you feel that using Eminence Designer has made you into an expert, so be it. However, attacking those with the CORRECT information, just because you don't like being corrected, is just plain wrong.

You are both wrong.
No further comment.

SonOfSmawg wrote: This sort of ill-informed and rudely-delivered commentary is one of the main reasons I rarely come to RO anymore.

SOS! Good to see ya. Its been a while. You're always welcome here, as you know. While I understand there are always differing opinions as well as different takes on most subjects, it seems a cross-handed slap at the REST of the R.O. community on your part was delivered and it seems inappropriate.

While you and Tiff may disscuss and batter about your differing conglomeration of information, I feel that as of the last TWO years, R.O. has been a very civil and non-confrontational place to be. Perhaps your lack of visitation here has not allowed you to experience this.

I hope you read this is candor and with the brotherhood it meant with. I always enjoy your visits and feel you contribute greatly to our place in this sea of information floating about in hyperspace.

Peace on you and yours this holiday season. Dave.

OKAY. There are as many theories about cabinet design as there are cabinet designers. Disagreeing with one another is to be expected. Hell, theres always a major clash in the realm of studio acoustics and by those who have DEGREES in this kinda thing!!!.

I dont care whos' right and whos wrong, I only wish it to be a cordial dissemination between those in the know and hopefully by dissagreeing you both learn something from each other. I know for a fact the SOS is very knowledgeable in this and I also know that Tiff is fully aware of what he speaks. So play nice and lets hear whats what in this arena and we'll all learn something in the process.

A long time ago many engineers did not agree with Dr. Klipschs' theories on sound reproduction. Some still dont. It doesnt mean he was wrong. Certainly not from what I have owned and heard.

That's why I kept out of it.

The bottom line in a 4-12 cab is how it sounds.

Some people like one thing and others another.

From what I understand the standard for a 4-12 shouldn't even sound good. Tell that to Jim Marshall and all the people that used his 4-12 greenback cabs including myself. Maybe that's why the originals were a little taller than wide.

I have owned so many cabs and it seems for sound the speakers make more difference than the dimensions. Also the width of the baffle board. things like closed or open back and even the type of open back.

I have owned many Marshall 4-12's and none had insulation. I had old smaller fender 2-12 and 2-10 tremolux cabs and I removed the stuff inside to improve the sound. With the stuff inside the cab sounded a bit muddy when the amp was cranked but better then when it wasn't. Leo did not turn those amps on 10 like I did though.

Leo's big 2-12 cabs sounded terrible no matter what, his big old 2-15 with JBL's and a Dual Showman head sounded awesome. Even Hendrix used those.

So try it and if you think it's sounds better it does. All this talk is such nonsense. Leave it for designing stereo equipment.