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In the Forum: Horn-Loaded Speakers
In the Thread: Problems with horns: upper bass
Post Subject: Winter Is But A SeasonPosted by Dresden on: 11/13/2008
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In terms of the length of the horn, I'm allowing myself a total height of 7'6" (just below the average ceiling height of 8').  In regards to the mouth diameter, that's another matter.  (It appears that I will have to build two [2] different prototypes--one with a 4" mouth, the other with a 7" mouth.  It's one of those things some guy mentioned, 'you can't predict the actual performance of the horn just by calculations--the horn design must eventually be judged on its performance AFTER it is built'.  What was his name...oh, yes, 'Romy the Cat', I believe [lol].)  I've already decided on a driver as well, the JBL 2206H (there is, however, an almost identical driver, the Selenium 12WS600, which call my attention, given that it's almost half the price for the same performance).  I'll initially go with the JBL 2206H, given that JBL drivers have always measured very close to the published specifications, which makes my job easier.

I would love to try a specialty compression driver of sorts, but I believe the approach I've decided on will allow me more flexibility, should the driver I initially use be inappropriate for loading the horn (I don't believe I'll have any problems as such, though).  One thing I will be implementing (as an option which can be added/removed with virtual ease) is a reducer (like that of a phase plug), which may or may not help to channel the acoustic energy more smoothly.  In regards to having 'undesirable' high frequencies output the horn, that will not be a particular concern (I'll be using an electronic crossover [manufactured by Rane] which will prevent any unwanted frequencies from being reproduced outside of the desired range.  I know, I know...why a crossover?  And Solid State?  I'm a realist--I need this done for a particular purpose, and the crossover [and most other equipment made by Rane] have always provided a transparent, smooth sound [that's been my experience].)

One other, very important concern you've mentioned is the fact that of the 'almost parallel walls'.  I've studied and thought alot about my options in addressing this design challenge throught this summer, arriving at one conclusion:  MASS.  Most people will use different layers of various materials to dampen resonances and so forth.  But I still view this as a correction to what may actually be a defective design.  In my study of the matter, the horn should be able to perform without emitting almost any unwanted resonances (normally achieved through bracing), and then, and only then, should the horn be dampened with any of the known methods to quiet any vaguely discernible resonances that may exist.  But in many ways, I'm my own worst enemy, a glutton for punishment (if you will)--given that my approach will be to build the horn first, achieve an acceptable performing design/dimension, brace (the entire length of each side, bend), and fill the space with a polymer.  I know, it's insane, it will probably weight three or four times as much as a comparable size horn would, but to me, mass is the ideal structure to killing any potential resonant areas.  (When bracing indiscriminately, designers will brace a few key areas--only to discover NEW resonances in other areas.  It drives me crazy, thus my approach and conclusion to use reall mass.)

I'll confess--though it will be made in VERY small quantities (should the design be successful to begin with), the system will be offered for sale to the few who find it interesting.  (It will suit private homes and permanent installations [for small venue area], for obvious reasons.  (Nevertheless, I'll be building this whether or not I sell a single set--at least it'll look good in a small local museum.)

In reference to the WAF, I'm divorced (and swore both to God and the devil never to marry again--lol).  But more seriously, I've put ALOT of hours to coming up with a design that will be very pleasing to the eye--despite it's size.  (Performance for the target audience is key, but I had to put alot of energy and time to coming up with a design that was aesthetically pleasing in order to create an acceptable arrangement.  I still designed around the configuration which has the best chance to achieve the desired audio goals first, of course, but in the end, the design morphed into something quite beautiful (in my opinion, any ways), and looks alot better than the initial design I had in mind several months ago (prior to having considered the audio performance goals).  In short, it will be a tall loudspeaker, but many wives (and girlfriends, lovers, other sig.) will probably want to have sex on this.  LOL.

I'm in New Haven, CT, but I have plans to move to North Carolina this coming year.  The fates will have to decide whether to allow me the pleasure (I love Charlotte).

 Romy the Cat wrote:

You need to decide what length of the horn you can afford. When I mean “afford” I ment the position of the horn in context of the rest of your system. You know the lowest cut off - 40Hz. So, the most suitable for you length and the mouth size will give you the throat diameter. If you have unlimited space in your room then be advised that starting form some point the increase of length and minimization of the throat will increase loading but also will introduces some unwanted colorations. You see, the longer horn is them more “parallel” it is. A horn that we use for audio have very slow opening at beginning and in very long horn the “beginning of the horn” section is very long, it might be a foot or two of virtually parallel walls. For the frequencies that the 40Hz horn will be caring the “virtually parallel walls” are the essentially the parallel walls.  I have no idea when it becomes a factor but too long horns tend to be congested and colored.

So, you have a horn, you have a throat diameter, then you need to find a driver. To decide on a driver is very complicated ceremony and my absolute rule is following in it: “It is absolutely imposable to predict with a serenity how a driver will sound after it will be loaded in a given horn.” You might do for compression driver, or for conventional driver, in fact any driver that you will be using with back chamber will become a compression driver.   The section of driver is a big subject… Linearity is not something that I would even care; do not think about it as you have no control over it anyhow. I laugh when people talk about linearization of bass horn frequency response.

Where are you? A well-sounding 40Hz horn is very interning accomplishment to experience. If you are near US’ New England and if you listen serious music then I would like to be invited after you finish the projects.

Rgs, the Cat

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