My Somewhat Unconventional take on Ideal Speaker Cabinet Size

Every now and then I am asked a question that directs my thoughts towards cabinet dimensions.  A good one just came in to the WGS Q&A forum.  When I get to thinking, I often get to blogging.  So ... let’s talk guitar speaker cabinet dimensions!

First rule: there are no rules.  There are a plethora of "ideal size" cabinet calculators available.  Those are fine for some purposes, like for getting the most bass response in a certain frequency range out of a certain sub driver, but I personally don’t believe they have much to offer when we’re talking guitar speaker cabinets.  This is particularly true where open-back cabinets are concerned.  I just took a quick inventory, and I have 12 1x12 combos, and no two of them have the same dimensions.  Here is a quick run-down of a few notable models, all of which sound quite good in their own way. (All dimensions in inches, rough, simply a quick tape-measure reading)

My old narrow panel 5e3 tweed Deluxe: 20”x16”x8” (width, height, depth)

A late 60’s Unicord 65: 16x29x7

My 1965 Deluxe Reverb: 22x16.5x9.5

My 1983 Rivera erea Concert: 24x19.5x10.5

A Gibson GA20RVT “Gold Tone”: 24x17x10.5

Jet City JCA2112RC: 21x20x11

Bugera Vintage 22: 22.5x18.5x10.5

My Bob Burriss Boutique "convertible" 1x12 cabs: 23x17x10

It is notable that all of these, save for the Burriss cabs, are open-back to varying degrees.  The Burriss cab can be either open or closed back.  In my view the lesson here is that, when it comes to an open-back cabinet, there is a great luxury of acceptable variance.  Probably the best sounding of the bunch is the smallest, the old tweed Deluxe, but I don’t think the cabinet dimensions account for much of that.  If anything, it’s the 55 year old nearly floating baffle and pine cab constructions that formulate it’s mojo.  And, of course the circuit itself!  As Fender went on to higher power amps that used bigger speakers, Leo really just made the cabinets as big as was necessary to contain the chassis and speaker while allowing for easy access.  Leo, the old repair man, was always making stuff that was easy to service.

So, my take on an open back cabinet is pretty much this: Make it something that will comfortably accommodate your speaker(s) and other size needs and make it about 9-11 inches deep.  Let the baffle resonate, and use a light resonant wood for the cab itself.  I know, that’s terribly un-scientific, but remember, I come from the Leo Fender school of thought.  Now, let’s think like Jim Marshall.

Marshall may not have invented the closed-back guitar cabinet, but he sure perfected it.  A closed back cabinet has a lot more ability to influence the sound of a Driver than an open back, and I think that here the dimensions become quite important.  Here, I will be very brief.  This wheel has already been invented by Mr. Jim Marshall; we need not re-invent it.  I’ve never heard a closed-back cabinet that sounds better than a Marshall 1960.  Same goes for Marshall’s 1965 4x10 cab and their 1936 2x12 (24x30x12).  Mind you, I’m talking about what folks usually want out of a closed-back cabinet: huge, thumping, tight urgent tone.  The relatively new Marshall 1912 1x12 (18x20x11.5) cab is okay, but I think they skimped on cabinet volume a little.  My personal fav here is the slightly larger Avatar G112 at 24x20.5x11. 

For me, the difference between the really good sounding closed-back cabs and the ones that leave me wanting more usually comes down to this: the bigger box wins.  I always refer to the 1960’s and 1936’s as “big box” cabs, since they are among the largest examples of the form you will find.  Put head to head, a 1960 will blow away an MG 4x12 loaded with the same drivers.  Sure, construction is a little different, but it’s the added size that really matters!

So, back to that "optimum size" calculator.  Don’t use it.  Guitar speaker cabinets are like guitar speakers themselves; what looks good on paper rarely sounds good in real life.  Unlike, say, control room monitors, where you WANT a nice flat and wide response, guitar cabinets, generally speaking, should substantially color the sound.  On paper, transistors whoop butt on tubes, but we all know which usually sounds better in real life.

So, my suggestion on "ideal" size for a closed back cabinet is this: flatter Jim Marshall by copying his best cabinet designs.

Yes, there are a few guitar cabs that use tuned ports/vents to enhance low-end response.  Here, it becomes important to take into account all of the T/S parameters of a given speaker and mate it to a cab that is of the proper dimensions and with the proper port dimensions.  But, this is rare in guitar cabinets, and in real life these cabinets rarely fare as well in real live as on paper.  When you start tuning the vents/ports on a cabinet, you usually are augmenting a narrow band in the lower octaves of human hearing.  Good stuff in the land of bass bins and bass guitar cabs, not usually so good in guitar cabinets (think WOOFY).  Feel free to disagree, post it here if you wish.  Ultimately guitar tone is all about personal preference, and what I’ve laid out here is simply one man’s personal preferences.

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