Need help designing some PA speakers

Discussion in 'Archived Threads 2001-2004' started by ArmenK, Oct 19, 2002.

  1. ArmenK

    ArmenK Stunt Coordinator

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    The UCLA AES's project for this year is a pair of outdoor PA speakers. I have been doing some research but have not been too succesful in finding the info I need. I really like the Eminence Delta-15 LFA driver but dont know what tweeter to match with it. I was looking at some horn tweeters because of their efficiency and off axis response but I am confused about one thing: most horn tweeters have pretty low power handling, usually around 40 W RMS, while the woofers can handle much more power, around 300-400 W RMS. How would I go about designing this thing so that I can connect the speaker to a high power and not destroy the tweeter? Sorry if its a simple question but I do not have much experience in this area. It seems that subwoofer design is so much simpler since there was only one driver. I have not even been able to find some good software to simulate a 2 way speaker, most of the software is only for subwoofers. Please provide any sources of information and any recommendations that you may have. Thanks alot!
     
  2. Wayne A. Pflughaupt

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    John,

    Good choice to look into horn drivers. They are the de-facto standard for PA speakers.

    Actually the horn is only what determines the dispersion pattern. The actual drivers are know as “compression drivers;” they bolt to the horns.

    But things are really not as bad as they appear.

    For one, there are plenty of compression drivers with higher power ratings than 40 watts. Take a look at JBL and Electro Voice lines.

    Second, compression drivers are highly efficient. In fact, in a two-way system the compression driver typically has to be “padded down.” So if you can only find one at 40 watts, you are getting a lot of output for the 40 watts.

    The simplest way to design a two-way system is to make it biamped, using an active out-board crossover and one amp channel for each driver. This is not most cost efficient method, but it is the preferred method for any serious PA system. It gives the highest SPL levels, and level matching between drivers is easier.

    Regards,
    Wayne A. Pflughaupt
     
  3. ArmenK

    ArmenK Stunt Coordinator

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    How many watts can I realistically pad on a driver? I assume it depends on the power ratings of the resistors involved but I dont know enough about the circuit design to calculate the max power it could handle.
     
  4. Greg Monfort

    Greg Monfort Supporting Actor

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    >The UCLA AES's project for this year is a pair of outdoor PA speakers. I have been doing some research but have not been too succesful in finding the info I need.
    ====
    Seems like getting a copy of the AES's Vol. 2 of their Loudspeaker Anthology to learn about the subject and then design/build some LF/midbass horns so you don't need so much power/pad down the horn mid/tweeter would be the obvious thing to do. [​IMG]
    Regardless, a driver only draws as much power as it's 'asked' to based on the level control and any insertion losses in the system between the amp's outputs and driver inputs, so while padding it down increases it's power handling capacity somewhat, the flip side is that it will 'ask' for more because it's been made less efficient by a like amount. IOW in a PA application you're still up against the mid/HF driver's power handling/excursion limits so you've got to design a system that maximizes LF/midbass efficiency, one way or another.
    GM
     

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