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Post subject: Open back vs. Closed back speaker cabs...
Posted: Wed Dec 01, 2010 6:49 am
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I was wondering if the difference is strictly "closed-back" cabs being "boomier" and so better for bass amps? I'm sure there's more to it though...

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Posted: Wed Dec 01, 2010 7:04 am
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It can also depend on what kind of speakers you're using. For example most people agree that Celestion Vintage 30s sound better in a closed back cab. Although I personally have them inside both open and closed and they sound good in each.


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Post subject: Re: Open back vs. Closed back speaker cabs...
Posted: Wed Dec 01, 2010 8:11 am
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tyronne wrote:
I was wondering if the difference is strictly "closed-back" cabs being "boomier" and so better for bass amps? I'm sure there's more to it though...

-T


Enhanced low frequency response and better dispersion control are hallmarks of a bass-reflex enclosure. Which is why professional-grade bass amps and PA/SR gear seldom employ infinite-baffle (open back) enclosures.

Indoors, the open-back combo guitar amp sounds "airier" and more three-dimensional while a closed-back cab is perceived to be more directional. Outdoors though, and the open-back combo falls on its face because nearly 50% of the volume is radiated to the rear. This principle holds true regardless of the speaker brand.

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Posted: Wed Dec 01, 2010 9:36 am
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I agree with most of everthing else posted.

I will just add that if you play standing up and walk around the room (you have to have a long enough chord), I notice that the volume and tone seems better as I get a certain distance with a closed back cab. Another plus of a stack situation when playing is that the conrtols can be accessed easier.

I really don't like sitting down in front of the closed back cab as much. To in my face. For sitting down close, I like the small open back amp generally. Of coarse so many other factors can into play.

So it depends on how I am practicing.

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Posted: Wed Dec 01, 2010 9:36 am
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I agree with most of everthing else posted.

I will just add that if you play standing up and walk around the room (you have to have a long enough chord), I notice that the volume and tone seems better as I get a certain distance with a closed back cab. Another plus of a stack situation when playing standing up is that the conrtols can be accessed easier.

I really don't like sitting down in front of the closed back cab as much. To in my face. For sitting down close, I like the small open back amp generally. Of coarse so many other factors can into play.

So it depends on how I am practicing.

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Posted: Wed Dec 01, 2010 1:29 pm
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There is also a technical reason to use in a open or close cabinet. let me try to explain with words:

The speaker is a "RLC" circuit coupled to Mass-spring-absorber. The absorber is calculated for an application for instance to be used in close cabinet. If you use this kind of speaker in an open cabinet the absorber coefficient is not the expected one and the displacement of the "membrane" is not under control, you have a risk to break the speaker. (I don't speak with differential equations ...) 8) 8) 8) 8) 8)

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Posted: Wed Dec 01, 2010 1:58 pm
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Tissan wrote:
There is also a technical reason to use in a open or close cabinet. let me try to explain with words:

The speaker is a "RLC" circuit coupled to Mass-spring-absorber. The absorber is calculated for an application for instance to be used in close cabinet. If you use this kind of speaker in an open cabinet the absorber coefficient is not the expected one and the displacement of the "membrane" is not under control, you have a risk to break the speaker. (I don't speak with differential equations ...) 8) 8) 8) 8) 8)


:?: :?: :?: :?:

Sorry Tissan, but I'm not buying that.

If you compare an original '66 Twin Reverb with a likewise-original '66 Bassman you will find the same Oxford 12T8 speakers in both cabinets.

One enclosure is an infinite-baffle, the other is a bass-reflex.

Your explanation holds no water at all.

Arjay

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Posted: Wed Dec 01, 2010 6:35 pm
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I enjoy using both simultaneously. I like an open back combo with a closed back extension cabinet. Adds a touch of tightness and grunt to the bottom end. Also sounds breath-ier in soft attack situations. Me like.


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Posted: Wed Dec 01, 2010 10:34 pm
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I prefer the bottom end punch that a closed cabinet gives you.Last night I stood in front of my old '68 2-15 Bassman cabinet while I had my 69 Bassman head cranked with a Les Paul going through and I could feel the air moving by my legs as I played-you'd never get that from an open back amp or cabinet.

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Posted: Wed Dec 01, 2010 11:11 pm
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BMW-KTM wrote:
I enjoy using both simultaneously. I like an open back combo with a closed back extension cabinet. Adds a touch of tightness and grunt to the bottom end. Also sounds breath-ier in soft attack situations. Me like.



+1

I'm generally playing a combo with a bass-reflex extention cab these days, usually a Twin Reverb stacked on a Dual Showman cab. I like the way the rig projects, either indoors or outdoors, and the added bass definition definitely fills out my tone. An unrelated benefit -- it's the perfect height for an ashtray and my drink!

:mrgreen:

Arjay

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Posted: Wed Dec 01, 2010 11:28 pm
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For indoor work, I've always preferred the open back, a couple of feet from a wall or corner(for compression). Outdoors, yeah I'd have to mic it. Tissan, RLC...what does this mean ? I'm aware of the reactive load aspect and some of the magnetic and heat principles. OK, It's dawning on me.... the "mass-spring-absorber" is speaking to the voice coil's ability to dissapate heat, control magnetic collapse, and govern cone excursion? Am I close to what you are talking about ? Art

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Posted: Thu Dec 02, 2010 12:03 am
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RLC......"resistance" + "inductance" + "capacitance", Art.

A electrical coil will contain all three elements, in both static and dynamic conditions.

HTH

Arjay

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Posted: Thu Dec 02, 2010 2:14 pm
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It's physics but I didn't say that some should not work in both conditions because it is depending of the absorber coefficient;
However if the speaker is designed to be in a close cabinet or bass reflex, the coefficient can be optimized to get optimized displacement response. Using this speaker in other condition will change the absorber coefficient and may create overshoot during displacement (it is equivalent to a second order RLC when the R become small, then you have oscillation before stabilization). Imagine that the oscillation is the displacement of the diaphragm, of the speaker, if you have oscillation you may have more displacement than possible, consequently the diaphragm, will hurt mecanically the min or the max.

But you are right, Retro, for guitare speakers, they are very rigid and the coeeficient absorber probably not dependant of the design of the cabinet; a big part of them are use in open cabinet.

note: RLC + 1 Retro, mass-pring-absorber (the model has 2 springs opposed) is the equivalent physic of the membrane in the speaker (like a car wheel spring and absorber or like a RLC circuit), the dissipation is linked to the thermal resistor between the heat source and the ambiant temperature, The heat source is active power is meanly the coil resistor, the reactive power is the magnetic power used to create force that pushes or pulls the diaphragm.

Retro "Don't waste water, protect the planet"

http://www.tymphany.com/files/papers/AE ... edance.pdf
http://www.epanorama.net/documents/audi ... dance.html

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Posted: Thu Dec 02, 2010 8:00 pm
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wow, love the jargon in the above posts... "the coefficient can be optimized to get optimized displacement response."


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Posted: Fri Dec 03, 2010 12:06 am
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Thanks for the links, Tissan. I've looked at them for a bit of time, but will read them thoroughly. Art

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