Open Back, Closed Back

[ComingApart]

Ok, basic question.
What are the typical differences in the two?
Why are most combos open back while most cabs that I've seen are closed?

[chickenpicker]

Originally Posted by ComingApart

Ok, basic question.
What are the typical differences in the two?

One sort, you can see the speaker from the back. The other, you can't.

[jhundt]

if you put a closed back on most combos there will be no air flow to cool the tubes. I built a combo cab with a closed back and a 15" speaker. Sounds very nice. But it's a little bigger than an open-back would be.

[Cobra8272]

i'm going to build a cab over the next few weeks, either a 1 x 12 or a 2 x12 so i've been checking designs and suggestions etc.
Bottomline seems to be open back cabs sound more bass-y and closed back highlight the mids and highs- (refer to the Celestion webpage ).
I think i'll end up with an open back 1 x12 but use something like the Greenback as price/cost will be an issue
Cobra

[yegbert]

Ted Weber has this note in his Q&A about open backs:

The amp would sound louder overall at the expense of losing a little on the low end...

I have a BF Bassman 2x12 cab that I've converted to 2x15. It was designed closed back, I've used it closed and open back. The bass seems stronger and directionally focused on this one of mine when it's closed. Open, what's behind it has more effect on the sound.

[4mal]

Closed back cab's typically have better (or at least more...) bass response. That translates as punch when you're standing in front of it. Open back cab's tend t emphasiszre the mids and hi's. That translates as 'airy' pretty well.

An option that I'seen folks use with Fender combo's is to build a panel that will make the amp 1/2 to 3/4 closed. This basically adds a portion of the bass response and re-voices the amp to a certain extent. I've been thinking about that with my Pro. Just get a little more body out of that cabinet.

[Joe-Bob]

Closed back cabs are also very directional.

[JohnnyCrash]

There's a couple of reasons for either in any build...

--

Probably the first major difference is:

Closed back's GENERALLY have a "tighter" more focused Bass response.

Open back's have more dispersion (room or area volume) and a more "loose" bass response.

--

For combos, where portability is important, the obvious benefit is the extra "dispersal" of audio (some backwards).

Some speakers actually sound better in either an open or closed scenario. Celestion Vintage 30s sometimes get "mushy" bass unless they're in closed cabs (although I have had a V30 in an open 1x12").

--

My personal rule of thumb is:

If I need exceptionally tight bass I go with closed - if I need portable volume (or "airy chime"), I go with an open back.

[Sqwerl]

I have always heard a larger backboard , giving less open area in the back will add bottom. True or untrue ?

[Cobra8272]

sorry i've got it wrong way around - follow this link
http://professional.celestion.com/gu...ibel/index.asp
cobra

[yegbert]

Cobra8272,

Yes, that info from Dr Decibel is in agreement with Weber's info and what's been said otherwise here so far on a general point: closed back will help produce a stronger bass. However, the recommendations from those two sources what speaker features would make them work best in either are different, and only Weber provides anything in the way of an explanation:

Originally Posted by professional.celestion.com's Dr Decibel

The closed-back type of cabinet has much more bass presence and a tighter feel. The sound is more directional, however, and can feel slower or less free and open. For this reason I would usually choose a large magnet speaker (eg Vintage 30) in a closed back cabinet as it is less bass-heavy. The effect of the large magnet outweighs the effect of the cabinet.

I have heard people say that the Vintage 30 ONLY works in open cabs, and others say it ONLY works in closed so ultimately it's all down to personal taste, your tone and style, and how you set your amp controls.

Originally Posted by Weber's [i

Let's Talk Speakers Q & A[/i]]When a person designs a speaker, one of the considerations is how much the cone will move and the subsequent loudness for a given amount of power driving it. If the designer uses a loose spider and fairly flexible surround on the cone, the voice coil will have an easier time moving the cone and the speaker will be loud with a small amount of power. The problem with a loose spider and surround is that as the power is increased, it takes the cone to its mechanical limit of movement and it gets harsh. This is an underdamped system and can also sound ringy. If you put this speaker in a sealed or closed back cabinet, the air that is trapped in the cabinet acts as a spring or big balloon that the back of the cone pushes against. This air mass helps control the movement of the cone and also affects the damping of the system, making the speaker sound more in control. A designer who uses a big magnet, tight surround and tight spider is designing for a low system Q, good damping, and good transient response. In other words, when you hit it with a sharp attack note, it responds and then stops very quickly rather than ringing on and on. This speaker would work well in an open back. However, in a sealed or closed back, the air mass spring we discussed earlier would add to the damping, potentially causing the speaker to be overdamped, compressed, and lifeless.