3-Way System Design Using the M4: Rent Com Inc: Audio Visual, Video, Projection, Presentation Rental AV Equipment

3-Way System Design Using the M4

Let us now turn our attention to designing a full-range reproduction system using the M4. A full-range system should be capable of delivering the same acoustic power at each octave throughout its bandpass. If we use this criteria to design our system, we can begin by noting that the acoustic output of a single M4 can be up to 150 acoustic watts in the middle of its bandpass. To be conservative, we will base our estimates on the M4's output at 200Hz, the lower frequency limit of its pass band. At 200Hz, the acoustic output power of a single M4 is:

How many low-frequency devices will be necessary to deliver the same 100 acoustic watts into the environment? Assuming a 200 watt power rating and 5% efficiency (both very typical specifications), our required number of bass speakers will be:

How many high-frequency devices will be necessary to deliver the same 100 acoustic watts into the environment? Let us assume that our high-frequency driver can handle 100 watts from 2000Hz up, and that it is 25% efficient in this passband. Our required number of drivers will be:

At this point it becomes apparent that the massive output capability of a single M4 can dwarf the output capabilities of the other devices needed to complete the passband. One solution is to relax the acoustic output of the system to a practical working level, which will mean that the M4 will be operating with a large amount of headroom, not a bad idea for the critical midrange. It should also be pointed out that a few assumptions have been made in our design problem. The same directivity factor has been assumed for each device. This means that bass horns or special arraying techniques must be used to provide directivity that extends into the bass region. Remember that wavelengths get larger as frequency goes lower, so the required pattern control devices can become quite large. Also, it should be emphasized that this is a very conservative and worst case estimate for the M4, whose typical acoustic output is closer to 150 acoustic watts through most of its passband. But, it never hurts to be conservative, and this approach results in an extremely reliable system.

See Figure