Martin Audio W8L Specifications download pdf (Page 23)

5.4 How many do I need?

There are four major factors to be taken into account when determining what model of

line array to use and how many:

Will I need delays? This is very important – see section 5.9

Spectral balance – the minimum column length required for spectral balance over

the complete audience distance – or just beyond the first delays

Maximum spl – the number and model required to achieve maximum spl

Horizontal coverage – see section 5.6

Spectral Balance

Users new to line array technology can be confused by the spectral balance requirement

because they are used to thinking in power terms only.

A straight line array’s transition distance tends to increase with line length and frequency.

If we simplify the relationship between transition distance, length and frequency (by

assuming that individual elements are omni-directional - which they tend to be at very low

frequencies) we can use an industry-standard equation to estimate the effect of line length

on the low frequency transition distance:

The transition distance is proportional to the square of the line length. Reducing the line

length by approximately 30% (which would only reduce headroom by 3dB with non-line

array systems) will reduce the LF transition distance by 50%!

The minimum column length cannot be reduced simply because the band is a quiet

traditional folk combo. A short line array column would project only mid frequencies to

the far field. It would lack warmth and sparkle as it would not be long enough for the line

affect to take effect at low mid frequencies and may not have the headroom at high

frequencies. Boosting the system’s LF and HF would simply cause too much bass in the

front seats and a lack of headroom at HF.

It is very important that you use a line array that is long enough for the low-mid

frequency projection to follow the superior mid and high frequency projection

out far enough for mid-high air absorption to have a balancing effect.

The following curves show the spectral balance of 4 and 12 W8L cabinets vs distance

taking air absorption into account for about 40% relative humidity.

1 2 ... 18 19 20 21 22 23 24 25 26 27 28 ... 136 137

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Martin Audio W8L Specifications Page 23