Power Amp Suggestion for 8 Ceiling Speakers

Discussion in 'Location Recording' started by puppy, Jan 1, 2008.

  1. puppy

    puppy Guest

    I'm helping out a meditation center and we don't have much budget.

    We got 4 pair of Proficient C620 6.5 Inch Ceiling Speakers (total of 8 speakers) for a very large room.

    Proficient C620 Ceiling Speakers
    • Design: 2-way coaxial in-ceiling
    • Power Handling: 5-100 watts
    • Frequency Response: 36Hz - 20kHz
    • Impedance: 8Ω
    • Sensitivity: 91dB

    We already have a Korg D888 as mixer and audio recorder. We will only use the PA for speech/recording.

    Questions

    1. Can you please recommend power amp(s) to output to those 8 speakers?
    2. Should we also get a feedback eliminator?
    3. We also need to do standard RCA and 1/8" audio outputs to a TV and Logitech wireless speakers for another room from the same source. I should just be able to do this from Korg D888 right?

    Thanks
     
  2. JoeH

    JoeH Well-Known Member

    Both Rane and QSC make true mutlichannel power amps, rack-mountable, with pro connections in & out, etc. They have separate power supply rails for each channel, and they all funcion like separate mono blocks. (I think the Rane is 6 channel, not sure about the latest QSC.) The RANE is roughly 100w/ch., if I recall.

    You may be able to do some summing (if it's mono) for the two extra speakers, running a pair in parallel will bring it down to 2 ohm loads per channel (which really won't bother the amp all that much), or you can try them in series wiring which will keep the load where you want it.

    Also, you can just get a stereo amp from the extra two channels; a 100w stereo amp won't set you back all that much.
     
  3. moonbaby

    moonbaby Mmmmmm Well-Known Member

    Normally, I stay clear of feedback eliminators. Most of them suck the tone out of the mic. Is this for a single voice? Will the voice talent be stationary? Or will the speaker (vocalist, not the loudspeaker) be moving around the area? Will there be a handheld mic, or a head-mounted or a lavalier involved? Wireless?
    If the speaker is moving about the area with a wireless rig under those ceiling loudspeakers, then maybe a feedback eliminator IS in order. The only one that I can concienciously recommend is the Sabine P-Solo. It will alter the tone of the mic, but that will happen with any of them. It is without a doubt, the fastest-responding and most stable of the ones on the market. Definitely worth the difference in price over the horrible Samsons and Behr^%$rs.
    Keep in mind that the Korg was designed to RECORD with, not handle live sound. In order to send your mix to other rooms, you really should have an "Aux. Mix" that will let you do this independently of tyhe "Main Mix".
    Typically, this is referred to as a "pre-fader" mix, so that the adjustments made in the "house" are not reflected in the "Aux", and vice-versa. But if you can use the effects mix off the Korg, that can provide you with at least a seperate volume-controlled "post-fader" mix to the other room.
     
  4. puppy

    puppy Guest

    Thanks for the information.

    Basically a gooseneck mic will be mounted on a table and the speaker will not be moving in the area.

    I never imagine that a mutlichannel power amp would cost more than $1000. RANE only has 4-channel (I think 6-channel is discontinued). QSC does have 8-channel. There is no alternative solution?

    The QSC 8 channel has two models:
    # 100 watts per channel at 70 volts (CX108V)
    # 90 watts per channel at 8 ohms and 130 watts per channel at 4 ohms (CX168)

    Line6 amp modeling boxes.

    CX168 is what we need right?
     
  5. puppy

    puppy Guest

    If I get two QSC PLX-1104, would it work?

    Line6 amp modeling boxes.
     
  6. moonbaby

    moonbaby Mmmmmm Well-Known Member

    OK, since you are just using a gooseneck, you may not need a feedback eliminator if the speakers aren't firing into the mic. BTW, Sabine makes a device called the Phantom Rider. This is designed specifically for stationary gooseneck mics. I use one for conferences, etc., and it really helps deal with talent that may not be very "mic savvy". And it's a bargain...google Sabine Audio.
    Why do you really need so many discrete power amp channels? If you get 70-volt transformers for the speakers, and drive them with a 70-volt suitable power amp, 2 channels should be fine. And, if you check out "Rane" on e-Bay's Pro Audio section, you will find some pretty good deals on the 6-channel amp.
     
  7. puppy

    puppy Guest

    According to another user, he asked me to send him photos of the speaker. He said it looks like conventional 8-ohm 2-way speakers with a crossover. No 70-volt transformer. He suggested doing four series-parallel-wired speakers with one QMS RMX-850.

    I came across this link. RANE DA 216S Distribution Amplifier. Would this work for us as well?

    http://www.rane.com/da216s.html
     
  8. moonbaby

    moonbaby Mmmmmm Well-Known Member

    NO!!!! The DA216S is a DISTRIBUTION amplifier, NOT a POWER amplifier!!! A distribution amplifier takes line (or, in this case, line or mic)
    level signals and DISTRIBUTES them to various zones' power amplifiers.
    It does not power speakers.
    Furthermore, practically any 8-ohm speaker can be adapted to 70-volt line use by adding the appropriate transformer (readily available from a sound contractor). I suggest you contact a sound contractor in your area. You are certainly not qualified to handle this job. I just watched a church down the street from me BURN to the GROUND because of improper wiring and installation of a sound system they had just put into their lobby. It made national news the weekend before Christmas. Don't be penny-foolish.
     
  9. puppy

    puppy Guest

    Thanks. I think we are going to end up with QSC RMX 850 with series/parallel speaker wiring and put 4 speakers on each channel.
     
  10. sheet

    sheet Well-Known Member

    Respectfully, I disagree. I never recommend 2 ohm loads. You won't find good paging amps that run at 2 ohms anyway, because that is not proper design. You should look at 70+V systems if your speakers are transformered. If not, then you can buy transformers for them, or spend more money on more power and deal with the power loss from long cable runs through small awg wire.

    I do not know the speakers that you have. You have the cart before the horse really. You should buy what is right for the job. You should read JBL's contractor series library notes about spacing and how to determine the quantity required for an area.

    Speakers have a q. The q will determine how far apart the speakers can be without phasing. Ideally you want speakers with high-q, so that you can get more together, have them sum, and thus add more output without adding power. You can have a 25W system play louder than a 100W system with the right speaker configuration.

    If the system is a paging system with music playback, I would recommend a TOA product with DSP. This will allow you do everything in one box. Rane is good stuff too, but pricey when you buy their dsp stuff. TOA allows you to add cards as their needs grow, or only buy cards for the task at hand.

    People that start off with feedback eliminators have no business running or designing sound systems. Those are the last choice when all else has been exhausted. It comes down to picking the right speakers, having them placed correctly, using the right mic, with the proper gain structure.

    I am not going to beat you up about this. It is a no money deal. But really, no money deals are a big pain in the booty, because the people are not going to be happy with performance, and your rep is tarnished. I would walk away. It's ok to say no.
     

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