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Post subject: XF Guitar Cabs
Posted: Wed May 16, 2012 4:21 pm
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According to this site:

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In an audio engineering course on how not to build a speaker the typical electric guitar cabinet would be around the top of the list.


Apparently this is more suitable.

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Not my opinion - just sharing the info.

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Post subject: Re: XF Guitar Cabs
Posted: Wed May 16, 2012 5:00 pm
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Well, it may not be your opinion but it is the company's opinion that is selling those cabinets. However there is absolutely no data on the website to support that opinion. But I will tell you one thing, given the way those speakers are recessed and angled in the cab, they are going to suffer from horrible edge diffraction due to the cabinet edges which will probably cause more problems than it solves. Look up speaker edge diffraction and you will understand.

Addendum: Let me clarify by saying that the statements about the effect on horizontal dispersion and comb filtering by horizontally mounted speakers are true, they just failed to provide any information to demonstrate the impact. I have doubts that angling the speakers inward like that will help alleviate either effect. In any case, take a look at Fender's design for the 1954 V-Front Super amp to see how Leo first attempted to improve speaker dispersion:

http://ampwares.com/amplifiers/fender-v-front-super/

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Post subject: Re: XF Guitar Cabs
Posted: Wed May 16, 2012 7:36 pm
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The portable enclosure intended to house a guitar amp chassis and speaker(s) has always been a proposition based on compromise and it's no secret that the infinite-baffle design used by 95% of all combo-type amps is notoriously inefficient. That said, most of them sound great and work well. The human ear renders the ultimate judgement -- not a bunch of poindexters with slide-rules and pocket protectors.

:mrgreen:

Arjay

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Post subject: Re: XF Guitar Cabs
Posted: Wed May 16, 2012 9:29 pm
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Retroverbial wrote:
The portable enclosure intended to house a guitar amp chassis and speaker(s) has always been a proposition based on compromise and it's no secret that the infinite-baffle design used by 95% of all combo-type amps is notoriously inefficient. That said, most of them sound great and work well. The human ear renders the ultimate judgement -- not a bunch of poindexters with slide-rules and pocket protectors.

:mrgreen:

Arjay


Actually, the open back combo speaker cabinet is not really an infinite baffle. By definition, an infinite baffle is exactly that; a speaker baffle that is infinitely large. Since that is not practical, the typical implementation of an infinite baffle is a very large, sealed enclosure. Examples are speakers mounted into a surface that forms one wall of a large closet or room. Sometimes the speakers are mounted into a ceiling that opens into an attic. The enclose is so large that is does not provide any "springiness" like that of an acoustic suspension speaker where the trapped air helps support the speaker. In any case, an infinite baffle prevents the back wave of the speaker from being transmitted into the room, eliminating any cancellation effects between the front and back waves. Infinite baffles were very popular back in the 50s before Acoustic Research introduced the acoustic suspension AR-1 loudspeaker.

The open back guitar speaker cabinet is really a type of dipole speaker where the sides of the baffle are folded around the speaker, preventing some but not all cancellation of the front wave by the back wave. Cancellation of mid and high frequencies is prevented due to the fact that their wavelengths are shorter than the folded sides of the cabinet and can't escape, while the longer wavelengths of the lower frequencies will wrap around the cabinet allowing some cancellation. A properly designed open back speaker will still provide decent bass response while sounding "airier" than a closed back speaker.

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Post subject: Re: XF Guitar Cabs
Posted: Wed May 16, 2012 11:26 pm
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For the purposes of this discussion, it is an infinite baffle.

That's how most folks commonly define the open-back combo and have for the last fifty years or so.

Do you have a pocket protector, Bill?

:mrgreen:

Arjay

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Post subject: Re: XF Guitar Cabs
Posted: Thu May 17, 2012 6:08 am
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To the OP, Howell... two issues. 1.) How does canting the two speakers towards each other help the tone? I don't even remember a Hi-fi speaker cab with this arrangement. and 2.) the guitar amp cab has to be able to withstand being toted about. I would think making the front face tilted inwards, in the fashion of the drawing, would make the overall structure less sturdy.

Just my opinions.


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Post subject: Re: XF Guitar Cabs
Posted: Thu May 17, 2012 6:32 am
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BMW2002Ti wrote:
To the OP, Howell... two issues. 1.) How does canting the two speakers towards each other help the tone? I don't even remember a Hi-fi speaker cab with this arrangement. and 2.) the guitar amp cab has to be able to withstand being toted about. I would think making the front face tilted inwards, in the fashion of the drawing, would make the overall structure less sturdy.

Just my opinions.

Hi BMW, To the question in your first statement. I ain't gotta clue. To your notion in the second statement. I concur.

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Post subject: Re: XF Guitar Cabs
Posted: Thu May 17, 2012 6:52 am
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Retroverbial wrote:
For the purposes of this discussion, it is an infinite baffle.

That's how most folks commonly define the open-back combo and have for the last fifty years or so.

Do you have a pocket protector, Bill?

:mrgreen:

Arjay


I'm not going to argue. I know how the speaker design literature defines "infinite baffle". If by having a pocket protector implies that I have studied speaker design in detail, then the answer is yes.

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Post subject: Re: XF Guitar Cabs
Posted: Thu May 17, 2012 7:12 am
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I am proud to say that I wore a pocket protector during my service tech years. Those that didn't wear one, either weren't prepared, or had holes and/or ink-stains in their shirt pocket. :lol:

No self-respecting engineer would be caught without his trusty pocket protector. It would be like Underdog without his ring. :lol:

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Post subject: Re: XF Guitar Cabs
Posted: Thu May 17, 2012 7:19 am
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If it weren't for the poindexters of the world we'd all be banging sticks, bones, and rocks to make music.

Right Arjay?

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Post subject: Re: XF Guitar Cabs
Posted: Thu May 17, 2012 7:21 am
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Hey! Those guys in the movie "10,000 BC" sound great with the sticks, bones, and rocks. :lol:

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Post subject: Re: XF Guitar Cabs
Posted: Thu May 17, 2012 7:47 am
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I'll chalk calling an open back, dipole speaker cabinet an "infinite baffle" right up there with Leo calling a vibrato a tremolo and vice versa. :wink:

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Post subject: Re: XF Guitar Cabs
Posted: Thu May 17, 2012 7:57 am
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bluesky636,

Isn't a an open-back combo amp cab as close to an infinite baffle as is possible? Technically, even a wall or ceiling mounted speaker is sill in an enclosure, whether the wall itself, the room behind the speaker, or the attic, it's still an enclosure. To have a truly "infinite" baffle, the speaker would have to be mounted to only the flat baffle, and hanging from cables only outdoors on a desert plain or in outer-space. Your thoughts?

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Post subject: Re: XF Guitar Cabs
Posted: Thu May 17, 2012 8:08 am
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shimmilou wrote:
bluesky636,

Isn't a an open-back combo amp cab as close to an infinite baffle as is possible? Technically, even a wall or ceiling mounted speaker is sill in an enclosure, whether the wall itself, the room behind the speaker, or the attic, it's still an enclosure. To have a truly "infinite" baffle, the speaker would have to be mounted to only the flat baffle, and hanging from cables only outdoors on a desert plain or in outer-space. Your thoughts?

I'll think about that while I count to infinity.

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Post subject: Re: XF Guitar Cabs
Posted: Thu May 17, 2012 8:18 am
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shimmilou wrote:
bluesky636,

Isn't a an open-back combo amp cab as close to an infinite baffle as is possible? Technically, even a wall or ceiling mounted speaker is sill in an enclosure, whether the wall itself, the room behind the speaker, or the attic, it's still an enclosure. To have a truly "infinite" baffle, the speaker would have to be mounted to only the flat baffle, and hanging from cables only outdoors on a desert plain or in outer-space. Your thoughts?


An infinite baffle prevents ALL rear radiation from a speaker from interfering and canceling the radiation from the front of a speaker. An open back speaker has no chance of doing that at lower frequencies due to the wavelengths involved. At low frequencies, an open back speaker acts as a dipole. Since a truly infinite baffle is impossible to achieve, the only way to do it is by a very large full enclosure. I described the typical implementation of an infinite baffle speaker in my earlier post. Feel free to look it up if you don't believe me.

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