TL or BLH with distributed multi-driver arrangement? - diyAudio
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Old 26th January 2013, 12:29 AM   #1
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Default TL or BLH with distributed multi-driver arrangement?

Has anyone tried using multiple drivers distributed along the length (or part of the length) of the line in a transmission line or back loaded horn? Something on this order...

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I have considered something like this as a possibility in a couple of situations and was wondering how the distribution of drivers would affect aspects of performance such as FR ripples and resonances. Does such a system alleviate ripple problems or exacerbate them? In what portion of the line might one want to place the drivers?

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Old 26th January 2013, 12:40 AM   #2
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Bose has done much research in this area. Check out Bose U.S. Patents 7,426,280 and 7,886,869 to start with

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Old 26th January 2013, 10:39 AM   #3
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Short version: it can be done; the line essentially 'feels' an oblong drive unit. The acoustic centre can be taken as the centre of the array of drivers. You may (may) find it evens out harmonic resonances since you're exciting the line over a greater length. A driver at the throat of a pipe provides maximum excitation of the fundamental & all harmonics. As you move it further down the pipe, you will vary the level of excitation of various harmonic modes (& to an extent the fundamental, particularly if a reasonable amount of damping is present).

Depends on the design itself too of course. In an aperiodic TL for example, which is stuffed with the object of providing a flat impedance curve (and in the process usually, though not invariably, has little output from the terminus), it will rarely make a major difference for obvious reasons. In a more lightly damped QW box which you're presumably referring to since you mention back-horns as well, it will have a more significant impact. If the line damping is done carefully though, I don't see any major problems in principle; there are several MTM TLs & MLTLs for e.g. with the drivers sharing the same line; I've done plenty like that with good results. Lynn Olson has used independent lines for the later versions of his (excellent) Ariel, but that was because the earlier types had two lines of physically different lengths that were then merged into one toward the bottom of the cabinet. With drivers sharing a single line, of a single length, this shouldn't be a problem.

Hope that helps a bit

Last edited by Scottmoose; 26th January 2013 at 10:41 AM.
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Old 26th January 2013, 11:29 PM   #4
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Thanks Scott. That is very helpful.

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