Speaker Asylum General speaker questions for audio and home theater.

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Nay

Posted by Dave_K on January 6, 2017 at 06:02:58

In Reply to: Would you consider doing this? Yea or Nay posted by Tidycat1 on January 5, 2017 at 21:21:22:

If you're interested in a line array, try a real one.

In a line array, the spacing between drivers is important. For far-field listening, the center to center spacing should be less than the wavelength of the highest frequency to be reproduced by the drivers. For near-field listening, a better rule of thumb is half the wavelength of the highest frequency. Neither of these conditions can be met by stacking LS50s.

Given the LS50 is 302mm high and 200mm wide, if you stack them top to bottom then the maximum frequency that they operate properly as a near field line array is approximately 570Hz. Or if you turn them on their side, approximately 860Hz. In the far field you can double that. So stacked LS50s in the far field are only going to work like a line array through the bass and lower midrange. In the upper midrange and treble they are going to act like a bunch of point sources producing an interference pattern.

A practical line array for home use will have multiple vertical line sources, preferably three (bass, mid, treble), with different driver spacing for each line source. To meet the vertical spacing requirement in the upper treble requires ribbons or special tweeters that can be stacked edge to edge.

One of the main advantages of a well executed coaxial driver design like the LS50s is the possibility of achieving a nice uniform radiation pattern that falls smoothly off-axis. By doubling up the LS50s, you're already defeating the purpose somewhat. I would expect to hear some small but audible changes in the frequency response as you move up or down out of the horizontal plane where the drivers are equidistant. Also, I would expect the apparent increase in image size you noticed is accompanied by some loss of image focus. I think the downsides are going to become more apparent as you add more. More importantly, the bass extension of four LS50s is the same as one LS50. Increasing the number of speakers increases the max SPL but doesn't give you deeper bass (not without some equalization anyway).

Here is what I would do: If your budget is enough for 4 pairs of LS50s plus a sub, and assuming you like the sound of the LS50s, then consider a pair of KEF Reference 1s instead. They share roughly the same voicing as the LS50s but are better in every respect. Otherwise stick with a single pair of LS50s and add a pair of good subs.

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