I have read a few threads about positioning of the woofer in the box, mainly discussing the pros and cons of forward facing, side firing, downward firing, close to floor boundary, close to mid-range etc. The considerations in those threads are acoustic coupling to the room, matching with the mid-range etc. My focus is different and concerns a typically rectangular baffle for a tower bass enclosure. The mid and tweeter are in a separate box sitting on top. I want to find the optimum position for a woofer mounted on the centre-line, which minimises the resonant behaviour of the driven baffle. For example, a centre mounted woofer is located at the most unsupported and least stiff position of the unbraced baffle. I have a notion that the ratio 0.618 = 1/golden ratio, may be a candidate. As I recollect, golden ratio proportions for rectangular panels maximise the dispersion between the natural frequencies, so they are least coincident (according to a measure I have to look up). Feel free to correct my proposition and suggest other positions.
In a high aspect ratio tower, the driver ideally needs to be at an odd harmonic of its 1/4 or 1/2 WL resonance and ideally this point will put it within a 1/4 WL of the XO point to get a good acoustic summation, though up to 1 WL can be used if sitting far enough away.
Generally then, the woofer would be at the extreme top, otherwise at ~1/5, 1/3, 2/5 if the XO point is low enough.
For smaller cabs, the golden or some other acoustic ratio to shape the baffle, width/depth ratio is a good plan as it minimizes the amount of damping required and ideally the driver would be offset in both planes [mirror image pairs] with one of these ratios.
GM
Generally then, the woofer would be at the extreme top, otherwise at ~1/5, 1/3, 2/5 if the XO point is low enough.
For smaller cabs, the golden or some other acoustic ratio to shape the baffle, width/depth ratio is a good plan as it minimizes the amount of damping required and ideally the driver
GM
Locate the tweeter at ear level ~ 39"
Locate the woofer as close to the floor as possible, while keeping the mid-woofer spacing less than the crossover quarter wavelength. Use an internal woofer bracing grid with no panel segment longer than the the mid-bass quarter wavelength.
example: 200Hz crossover = 68" wavelength => 17" quarter wavelength
1) mid-woofer separation should "ideally" be < 17"
2) woofer should "ideally" be <20" height
3) bass cabinet bracing should "ideally" create < 17" long panel segments
most designers usually accept a slightly longer mid-woof separation in order to locate the woofer closer to the floor to reduce ground bounce effects.
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1. Mid-woofer spacing should be less than the crossover quarter wavelength to maintain one lobe.
2. To control floor effects, the woofer height above ground vs. room placement sims recommend:
< 24” high to reduce floor bounce quarter wavelength (96”ceiling/4), and as close to the floor as possible. This also helps smooth bass SPL when the speaker is located away from rear/side walls.
3.Typically, bass frequencies are longer than the baffle width, and upper bass harmonics can be managed with a good panel bracing grid with no panel segment longer than the the mid-bass quarter wavelength. Typically one top-bottom brace interlocked with two front-rear braces.(one above and one below the woofer)
Locate the woofer as close to the floor as possible, while keeping the mid-woofer spacing less than the crossover quarter wavelength. Use an internal woofer bracing grid with no panel segment longer than the the mid-bass quarter wavelength.
example: 200Hz crossover = 68" wavelength => 17" quarter wavelength
1) mid-woofer separation should "ideally" be < 17"
2) woofer should "ideally" be <20" height
3) bass cabinet bracing should "ideally" create < 17" long panel segments
most designers usually accept a slightly longer mid-woof separation in order to locate the woofer closer to the floor to reduce ground bounce effects.
===========
1. Mid-woofer spacing should be less than the crossover quarter wavelength to maintain one lobe.
2. To control floor effects, the woofer height above ground vs. room placement sims recommend:
< 24” high to reduce floor bounce quarter wavelength (96”ceiling/4), and as close to the floor as possible. This also helps smooth bass SPL when the speaker is located away from rear/side walls.
3.Typically, bass frequencies are longer than the baffle width, and upper bass harmonics can be managed with a good panel bracing grid with no panel segment longer than the the mid-bass quarter wavelength. Typically one top-bottom brace interlocked with two front-rear braces.(one above and one below the woofer)
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