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  1. #1
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    Buying the right amp.

    My church has just moved from a house to a hall and I've been put in charge of buying the sound equipment.

    I have a Yamaha promix 1 mixing board
    2 600 Watt 8 Ohm speakers
    2 250 Watt 8 Ohm speakers

    Now I just need a couple amps and I'm wondering what I should get, I was in one place where the guy wanted to sell me two Behringer EP2500 amps, but they are 1200 Watts into 2 ohms.
    I'm not really much of a sound guy... I just happen to be the most technically inclined person available.
    Any help would be appreciated

  2. #2
    Do you have a budget?
    'I think my intimate relationship with electronics started as a child when I was playing with a screwdriver and a wall plug, Doc, and...'

  3. #3
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    Currently we're looking at buying used to save costs, but essentially right now there is no set budget.

  4. #4
    OK, well the berringer seems a little big for the speakers. What are they? By the way, bless you for your service, and welcome to the forum!

    You may want a smaller amp to drive the speakers, and maybe a better quality. Berringer, well, we eat them alive at my church. (well, we do have an arena-size mega-system, so we go through alot of equipment anyway) I refrain from recommending specific brands, but since you bought such a sweet board, I would try to stick with that level of quality. (you will absolutely fall in love with the scene memory, especially if other people will be operating it also).

    Anyway, it's best to match the amp's output with the speakers, and you can go lower, but not higher. This is more of a guideline as there are exceptions. I mean both the power (watts) and the impedance (ohms).

    I hope this is enough info to prompt your next question.
    'I think my intimate relationship with electronics started as a child when I was playing with a screwdriver and a wall plug, Doc, and...'

  5. #5
    It is best to stick with the RMS ratings. The ratings are a guideline, none of the speakers out there are going to list exacting numbers, but you cannot go wrong getting an amp that is 'matched' to the speakers. If you find that you aren't getting enough volume this way, you simply need more amps and speakers.

    The Behringer amp is rated at 1200 W at 2 ohms, your speakers are rated at 8 ohms, so you'd have no trouble with that amp and those speakers. the 4 ohm output is what you should look at, if you are going to drive two boxes off each side of the amp.

    I would recommend a couple of good old QSC RMX 2450's. They are great all-around amps and I've never had any trouble with them, plus you can usually find them on the used market at a good price. I would stay away from the bottom-of-the-barrel stuff... Pretty much look at it like this: If the price seems to be so much 'better' than the competition, there had got to be a reason, and its not just that the manufacturer wants to save you a couple shillings, if you know what I mean....

    Look at the way companies power their own speakers. Find a model that is available in a passive model and a powered model. You will find that the amps inside are not rated above the RMS rating of the non-powered box. if they are, there is certainly some internal processing going on to make sure the unit is not overpowered.

    There is a conventional belief that you should buy a bigger amp than your speakers, in sound systems with experienced operators, this is how we do it, but anything with volunteers or folks who are still learning, I'd stay away from higher powered amps than the speakers you have.

    Make sure your signals are clean all the way through your rig, and put the amps limiters on, you should be fine.

  6. #6
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    Not 100% sure of the brand of speakers (have to wait until next Sunday so I can check)

    I didn't know Behringer wasn't a good brand... personally I thought Yamaha was more bottom of the barrel. And I do love the scene memory on the board, should make it fantastic since we have three different worship groups.
    I guess my current question would be: what would be the best wattage and ohm rating to look for to power my speakers? We are all volunteers and mostly ignorant when it comes down to all this (I have done sound at another church but that was essentially just adjusting the levels and recording)

  7. #7
    Hey, Tov,

    Re-read what Bassred said above. I don't know that I can put it better at your level of expertise as far as matching speakers to amps, but Berringer is crap compared to Yamaha, and Yamaha is not the bottom of the barrel by far, but some of thier budget stuff I think is.

    I uderstand the rest of your last question, but may I ask you something about the hall you intend to use all this in? I don't want to drag you into all the math and stuff but it does play a part, a rather large part, and I, and others here, can maybe help you head off some acoustic problems, like feedback, etc. I do, in my heart , think this is important.
    would you please describe the hall? and also in aproxamate feet?

    My idea here is to help you figure out what is needed first and then figure out the gear. In other words, lets see if what you already have fits the bill.
    'I think my intimate relationship with electronics started as a child when I was playing with a screwdriver and a wall plug, Doc, and...'

  8. #8
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    The hall is in an rec center, has concrete block walls (a nightmare, I know) it's about 40' x 35' we're currently renting the centers board, which is an old 80's board that is pre-amped at 800W 8 Ohms, so we're using our 250W speakers with it.
    We are currently looking at buying two amps so we'll just be running one box off each side of the amp. I understand matching RMS rating at this stage of the game is a good idea... but do I need to double the wattage for two speakers? or if I got stereo amps would that mean that it was putting out the listed wattage per channel or overall?

  9. #9
    Cool, a blank block room. With as many people as can be packed in there, I hope! You shouldn't have much of a feedback issue, given the room size, maybe the lows. Maybe some reverb, but that's an easy fix with some strategically placed heavy curtains or something.

    Amps, at least what you are looking for, have 2 channels, 1 & 2, and they can call it left and right, but that doesn't really mean stereo, just that there are two amps in one box. (stereo is a matter of what you put into them).Just about all of this type amp will list 'watts per channel into -- ohms'. (Don't worry about 'bridged' numbers, because you won't be using the amps that way). If an amp you're interested in is listed as '---watts stereo' they almost certainly mean that the 2 channels combined are that many watts.

    Watch out for equipment rated in 'peak' or some other form of power. RMS is pretty much the same as 'continuous' or 'average', but 'peak' is different. Peak is what the equipment can deal with all of a sudden for a split second, more or less. (there are manufacturers who play tricks with these terms in order to sell stuff, so be careful).

    In your case you are connecting 1 speaker (or I should probably say 'box') to each channel, so you want one amp listed at '600 watts RMS per channel into 8 ohms' and the other at 250.

    Now, I have another question. Is one pair of speakers (boxes) for the high frequencies and the other pair for the lows? or are both pairs 'full range'?

    The reason I ask is that if the former is the case you will need a 'crossover' to separate the hi's and low's prior to the amps.

    If the latter is the case, then the crossovers may be built into the speakers. Again, what models are the speakers?
    Last edited by penniesfromheaven; 7th Jul 2009 at 12:17.
    'I think my intimate relationship with electronics started as a child when I was playing with a screwdriver and a wall plug, Doc, and...'

  10. #10
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    Ok, now I understand that.

    The guy who sold me them said they were full range, we're going to use the two 250W speakers as monitors. I can check on Sunday about the model of the speakers and get back to you (unfortunately everything is stored in a utility closet we're renting from the hall, so can't really check on that)

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