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Allen Speaker placement - best distance from reflecting surface for best acoustics?

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  • Allen Speaker placement - best distance from reflecting surface for best acoustics?

    Hi Folks,

    Our church is the happy recipient of an Allen L451DK, and we're weighing options on speaker placement of the sixteen recommended speakers for this instrument.

    Fantastic resource, this forum - thought I'd ask for suggestions and recommendations for the placement of speakers for the best acoustic realization in the church.

    There are sixteen speakers in all -

    Great: 4 HR-200s and 2 HR-100s
    Swell: 2 HR-200s and 2 HR-100s
    Solo: 2 HR-200s
    Choir: 2 HR-100s
    and two SR-5s to cover the low frequency needs (these will be placed on the floor somewhere)

    The church is not big - 60 ft long (including a 15 ft altar/chancel) x 32 ft wide. Side walls are 16 ft high, and rise from the top of both sides as an A-frame to the central ridgeline at 38 ft.

    Because of the directional horns in these speakers and additional visual aesthetics, we're planning to either place the speakers sistered along the side angled rafters above the chancel, and pointing the speakers forward (away from the congregation), so the sound reflects and disperses off the front wall on its path to the congregation; or, alternatively, placing the speakers on a horizontal platform high in the rafter joists, pointing them generally up, so the sound reflects off the angled sides of the ceiling and is dispersed from there.

    We're working with Allen, and expect to have the system professionally voiced, so we'll get their advice, of course. Either system will be non-trivial to implement (requiring additional mounting hardware beyond Allen's standard hardware, and renting a genie lift, so I'd like to decide on which approach to recommend to the project before the Allen professionals come to town).

    I've been reading through the forums (fantastic resource, with several awesome and generous contributors -thanks!) - and I am convinced that reflecting the sound from these speakers as much as possible, before it hits anyone's ears, is the best thing to do.

    Long pre-amble to a short question, the answer to which I really don't know:

    All other things being equal, how far should the sound travel from a speaker, before it hits a hard surface and begins its reflected path to the happy ears of the audience?

    To be clear, if the speakers are high in the church (possibly tilted a bit), and facing a hard wall or ceiling surface, does it matter much how far the speakers are from that surface? For example, is one foot enough, or 3 feet better, or 15 feet too much?

    In our situation, in the "facing forward" configuration, the distance to the front wall will be about 10 feet, with one side edge of each of the speakers flush against the angled ceiling. In the "facing up" configuration, the speakers would range between 3 and 8 feet from the angled sides of the ceiling, and the sound would be reflected from the ceiling surfaces.

    I realize this might be hard to visualize, but hopefully the description is good enough for those with acoustic experience to tell me if the sound from speakers needs some room to develop, before it's first reflected from a surface. If so, how might this depend on frequencies and associated wavelengths?

    There will be a little flexibility for some experimentation, but not much. At least having the "facing forward - reflected from the front wall" vs "facing up - reflected from the ceiling" question resolved in advance would be helpful.

    Oh, by the way, hard surfaces everywhere, except for carpeting on the 15ft by 32 ft chancel / altar area. Very lively space, acoustically (and culturally). Also, the console is located forward, in the upper stage right area of the chancel. (How's that for mixing up the sacred and theatrical vocabulary?).

    I'm really looking forward to hearing the thoughts and experiences on the minumum / optimal / maximum distance that a speaker's sound "should" travel, before it hits a wall and has its first reflected bounce.

    Cheers, and thank you all for your help, and your passion for doing these things right!

    Last edited by Bruce.Simonson; 07-16-2018, 09:09 PM.

  • #2
    Without knowing at least what the room sounds like, anybody would be making wild guesses.

    For instance, when Walker came to install the organ at my church they changed their plan after hearing it installed and then repositioned the speakers before voicing it. And they even knew what the room sounded like prior to installing it.

    It’d be helpful to everyone here if you were able to make a recording of something musical in the room so that we’d know what the room sounds like. Maybe even some photos so we can see some possibilities.

    With all of that said, as you already guessed, I’d recommend not having direct facing speakers. I wouldn’t plan on having them face backwards though. My first thoughts is to plan on having them face up toward the ceiling. With some flexibility of angle.
    Viscount C400 3-manual
    8 channels + 2 reverb channels (w/ Lexicon MX200)
    Klipsch RSX-3 speakers and Klipsch Ultra 5.1 subwoofers