This summer’s project was to build a set of line array speakers for our bluegrass band that would encompass a wider frequency range than my previously built set. If you are unfamiliar with line array speakers, think Bose L2 or the huge arrays that you find centered above the crowd in large concert venues. The idea with a portable lie array is that they sound good nearly anywhere in the room, they do not need to be loud to be heard clearly nearly anywhere in the room and when judiciously placed, they can act as the band’s monitor as well as the main speakers for the audience (less stuff to carry). In addition, line arrays have a relatively narrow vertical sound spread yet a very wide horizontal sound spread (less reflective noise distortion bouncing off the floor and ceiling and more folks reached on the horizontal axis).
The older set I built included two stackable cabinets of four 5" coaxial drivers. I would use these with a 15" subwoofer. The design parameters were to have lightweight cabinets that could throw high quality sound a large distance with relatively low wattage. The line array cabinets fit these parameters with these specs:
100db @ 1W/1m @ 1000hz
95db @ 10W/32m (approx 100 feet) @ 1000hz
These worked extremely well in most situations, especially when inside a small to moderately large room. In fact, they worked too well when we recently played at a festival and our band could be heard inside a facing concert location about a half block away (both locations had their fronts wide open). Oops… The upside is that it brought more folks to hear us… Anyway, the downside of these cabinets is that they do not produce much below 150hz and so the subwoofer is needed to allow the bass to be heard. The subwoofer is a point source speaker and does not throw like the array speakers do.
So this summer, I decided to build new cabinets that could be used in conjunction with these smaller cabinets. The new cabinets have these parameters: they need to be able to fit in my Scion XB (small car), they need to produce full frequency sound including notes down to 44hz, and they need to be stackable. The new cabinets incorporate four 8" full range drivers in each cabinet (2 cabinets total). They have speaker mounts on both the bottom (for mounting on a speaker tripod) and on top (for mounting either the other 4 x 8 speaker or the 4 x 5 speaker). The 8" drivers used have a frequency response of 39hz to 14000hz (relatively flat). Since our acoustic band does not produce much sound above 14khz, I figured that these should work fine. They have a power handling of 60watts rms and produce individually 91 dB @ 1W/1m. In an 8 speaker array, this should produce approximately 100 dB @ 1W/1m. These will be very similar to the output of the smaller cabinets.
At this point, the cabinets are ready for paint, yet still need to have the hardware mounted (speaker mounts, jack plate, speakers…etc). The plan is to use one of these cabinets along with 1 smaller cabinet on smaller gigs and all 4 cabinets on large gigs. Also, I will bi-amp the cabinets so that I can control the sound traveling to cabinet. I will do this with a Carvin 12 channel/4 amp powered mixer. Each amp provides 400w rms @ 4 ohms (300w @ 8ohms).
These cabinets are quite a bit heavier and that worries me a little. I’m closer to 60 than I am to 50 and I am not a big fan of carrying heavy speaker cabinets just before playing a gig. However, my 16 year old son plays with our band and this duty may be passed on to him.
I will post pics and sound clips when they are finished.