Why do they place tweeters far from the mid-bass? - diyAudio
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Old 21st October 2008, 11:34 AM   #1
poldus is offline poldus  Europe
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Default Why do they place tweeters far from the mid-bass?

I would welcome your comments on why so many designs place tweeters quite away from mid-bass drivers. Shouldn't they be as close together as possible to aproach an ideal point-source response? What are the benefits, if any, of those designs?
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Old 21st October 2008, 03:13 PM   #2
sreten is offline sreten  United Kingdom
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Hi,

The short answer is that modern designs do not do this.
They are nearly always fairly close and vertically aligned.

/sreten.
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Old 21st October 2008, 03:35 PM   #3
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Which designs place the tweeter so far from the midbass? Yes they should be very close, though its somewhat frequency dependent. Lower frequency points for the crossover would allow them to be farther away and still sum acceptably.
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Old 21st October 2008, 03:48 PM   #4
poldus is offline poldus  Europe
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The number of speakers with tweeters widely spaced from mid-bass units is huge, ranging from extreme cases of over 10 inches to miriads of examples of tweeters that do not have their rims touching those of their bass partners, when they easily could. Instead, they opt for separating them from a couple of inches to often quite a bit more.

Even when the crossover frequency is low enough, isn't it still better to place them as close as you posibly can?

Makes me think those engineers are prioritizing benefits i am not aware of.
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Old 21st October 2008, 05:00 PM   #5
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I don't know if his site is still up, but I remember somewhere on Wayne J's speakerbuilder.net (I think it was the Eros writeup) that he mentioned that, in his experience, spacing the mids and tweeter a bit farther than normal could sometimes create a bigger soundstage.

Is it true? I have no idea. I've designed speakers with the mids and tweeters pretty much touching, and ones with an inch or more between the two drivers. In the end, that bit of driver spacing had a far smaller impact on the overall sound than whether the design was a TM or MTM. And really, the largest factor in the driver integration was not their physical layout, but the crossover design... like, by a mile.
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Old 21st October 2008, 06:12 PM   #6
pjpoes is offline pjpoes  United States
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well spacing them farther might give the illusion of more space as it would create more summing issues, especially in the power response.

It really doesn't matter if they are a few inches if that space is smaller than the wave length at the summing frequency, so I would argue that, no, its not better. As for ten inches, while I'm sure there are some, I haven't seen many. I'm just wondering if you could show me some, I would want to see if there appears to be logic behind the design.

Now if by ten inches you are referring to large horn systems, that is a different story. The same laws apply, but typically horns are crossed over quite low, and the edge of the wave is different than with a dynamic driver, so spacing can be a little different.
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Old 21st October 2008, 07:02 PM   #7
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Sometimes aesthetics are given more weight than performance. "If you can't make it sound good, make it look good"

Spacing also causes awful lobing problems with horns, but most people building that kind of speakers are more focused on luxury furniture-like finishes and exotic vintage drivers that on optimum power/polar responses.

Theoretically, the angle at which the main vertical nulls and lobes happen depends on driver spacing, but I feel this is seldom taken into account. Floor and ceiling reflections may be reduced if the optimum distance is used, but complex polar measurements are required to optimize this.
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Old 21st October 2008, 08:45 PM   #8
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Old 21st October 2008, 09:01 PM   #9
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Old 21st October 2008, 09:14 PM   #10
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Avalon acoustics designs more for looks than sound in my opinion. They claim the design is to reduce diffraction effects, but the crossover points are far too high to not have lobing issues, and all the response measurements of their speakers I have seen suggest that the design is compromised. Having said all that< i've not heard any of their speakers.

With horns, I didn't mean to say that horns don't need proper spacing, just that they can look like they are spaced too far apart, but really are fine based on summing points and radiation from the horn.
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