Open vs. Closed Back?

What is the sound difference between and open and closed back cab?

Except... you should look for an old Mitchell Sand Cabinet... it is NOT big, and only a some-what heavy... but they sound REALLY nice..! ! ! IIRC
Mitchell was around LONG before BOSE came around....

My first *experience* with Mitchell was a 2x12 SAND CABINET being run by a Fender head... (Deluxe..???) Sheeeeeiiit...! ! ! ! It rocked..! ! !
The thing about it was.... loud, full, lots of harmonics, and crisp with lots of bass....
Did I say it was loud...? ? ? ?
I think the thing that sold me was the *complete* range of harmonics that were there... these cabs had sand in them to dampen the harmonics coming off the sides and back.

If you check around, you might find that some of the better recording studios have Mitchell cabs as standard equip.

Just my 5 centimes...

A lot of good answers, including the Google search suggestion. The one thing no one has mentioned is that there's a potential benefit to an open back on a tight stage, in that the sound bouncing off the back wall can get to you easily, whereas a closed back cab on the floor behind you is kind of hard to hear. I tend to prefer the diffuseness of an open back cab, though I can also hear what people prefer in a closed back.

"Open back" cabs aren't usually totally open. There are panels that run across to protect amp and speakers and to keep stuff from falling out. I guess most open back cabs are really only little more than hal open.

I have a Fender Dual Showman cab, modified to 2x12 from the original
2x15. I took off the closed back and made panels that go across in roughly the same propostions as a Twin Reverb cab. Put this thing on its side and it looks like a Twin cab, minus amp, grown 50% larger.
Sounds like it too. Unfortunately I don't have room for it in the house so it sits, unloaded, in the shed. One of these days I'll throw some speakers in it and take it out for one show just to hear it again.

I'm not sure how these'd sound for guitar. Maybe for bass...

A transmission line speaker can be thought of as a twisted path for the rear wave that is usually tuned at 1/4 the wavelength of the resonant frequency Fs.
You are using the back wave to reinforce the low frequencies, a la Bose. Some people may like a guitar speaker that is heavy around 80 to 100 Hz, many will not. Bass is a different story, but these cabs tend to be big and HEAVY. A permanent PA installation would be a good application.

Great answers from all! Thanks.

I second the google suggestion, but here's an ultra condensed version.

Open back cabinets allow some of the rear wave of the speaker to cancel the front wave, so you have attenuated low frequency response.

If you imagine yourself glued to the ceiling, an open back cabinet will project in a "8" pattern, where a closed back cab with project in a "V" pattern. Number of drivers and driver position affect the projection angles, but that's going beyond your inquiry.

Most people would probably say that open backs sound more "airy" or ambient (assuming you have solid surfaces behind the cab for reflections), while closed cabs have more focus, bottom and punch.

Just thought I'd append these great answers...

There is a cab design... I *think* it's called "transmission line" (????)
It's closed-back but ported through the front....
and *tuned* somewhat. The old Mitchell Sand Cabinets (heavy mothers.! ! !) used this design... and they sound pretty damn good.

I've considered building one... but I've still got twenty items on my 'list' that have priority....

Ted Weber can provide info on the design and performance of these...

CONAN MAD!! MUST BREAK THINGS!!

I look at it as what did it cost anyone for me to post it? Or for anyone to reply? Nothing. At least it had something to do with amps.

So I am assuming my Boogie Mark IV with 1/2 open back does more of the open back sound than the closed back sound.

I am asking because I am having an extension cab made and I want to do the opposite with it. Probably closed back.

Also it matters how big the cab. is. Ideally speaker should be mounted on indefinite size baffle. Cabinet size being what they're in real world all things mentioned is known. Some cabs come with panel to make it open or closed back. Guytron 2X12(V30s) in my house is one of them.

Tony: I think you meant to say INFINITE baffle (I know, you try SO hard..)

Cabinet size being what they're in real world

There is no valid contraction for "they are", as there is for "you are" (you're). (Again, keep striving for perfection...)

Some cabs come with panel to make it open

(such as the ) Guytron 2X12(V30s). (There is one or, I have one) in my house .

Hang in there, Dude.....

To me, closed back cabinets do a better job of focusing the sound, where open back cabinets just tend to spread the sound all over the place in an ommi-directional manner.

Closed back cabinets tend to have tighter bass.

I like closed back cabinets better for most things.

Open back enclosures have little low frequency response, but they are cheap to manufacture.

Closed back enclosures, if designed properly, have a lot more punch and a solid low end.