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Old 18th July 2002, 09:55 AM   #21
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Hi Poor, glad you are getting the hang of it...

Buying an amp for these things should be easy, but may be expensive, unfortunately.

IMHO you should go for a profesional amp, as domestic/in car amps are just not reliable enough for gigging.

I'm sure this will be discussed in depth on the LAB forum once people have built some boxes, but for the time being I would track down a local second hand pro audio dealership and tell them your needs.

From the power rating of your main speakers, you will need at least 6-800w per side for your subs, and I would suggest a capability to drive 2 ohm loads is vital, both for when you expand your rig, (you will!), and it is a good measure of an amps design and construction to drive loads this low.

I would suggest something like the EV or Amcron 1200w jobbies, (but not Amcron Powerbase, I have a local dealer friend who has a big pile of these, dead, in the corner of his warehouse, and its just not worthwhile for him to fix them), but there are many types I am not familiar with, especially as you are in the States, and I'm in the UK!

I'm sure, once you have the boxes built, you could take your rig down to a s/h dealer and just audition their amps to find one you can afford and like, as most pro noise boys, even though they might have gone into sales, love playing with kit, and will find something to suit.


Hope it goes well-
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Old 18th July 2002, 11:00 AM   #22
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Hi Poor,

Even thought the LAB drivers have an Rdc or 4R, with two in the enclosure and paralleled, the load should still be about 4R total that the amp sees. Any decent pro amp will drive them, and there were even suggestions about using a good quality plate amp for smaller venues.

Sensitivity should be well over 100dB/W/m from about 60Hz up. If you applied some EQ to flatten it below 60, say to 40 (just below bottom E) and high pass it from there you might only need a few hundred watts a side. My advice would be, to hire something for a night, and see what you really need in the size venues you play. My guess would be 400W a side max for quite decent size clubs, and probably less for smaller ones.

Don't use car amps or normal domestic gear. It never stands up to the rigours of live use, and usually doesn't have balanced inputs. The few exceptions would be brands like Bryston or Perreaux, who had a foot in each camp.

Cheers
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Old 20th July 2002, 04:00 AM   #23
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Quote:
If you applied some EQ to
flatten it below 60, say to 40 (just below bottom E) and high pass it from there you might
only need a few hundred watts a side.
Eq by no means reduces your need for power. In fact, it does just the opposite. If you add, ohh... i don't know, 3 dB of eq at 40hz playing program material, power needed at 40hz will be 4x of that needed everywhere else. So, at 100 watts, with 3db of eq, 400 watts will be needed for minimal headroom. However, your SRM's are about 100 dB efficient from midbass +, and would need no more that 20 watts to blow you're head off. So, let's say you add 6 dB at 40 Hz, you would need 240 watts for the lows. In my opinion 400W @4ohms /side would be optimal for your price/performance ratio. You may need to reconsider your $400 window. Finding a decent 300-400 watt amp for less than that is hard unless you go used(which you probably should). Plate amps aren't a bad idea either, there is a thread posted by the one and only slicemaster101 concerning big, bad plate amps.
-andy
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Old 20th July 2002, 04:41 AM   #24
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Quote:
Originally posted by bostarob


Eq by no means reduces your need for power. In fact, it does just the opposite. If you add, ohh... i don't know, 3 dB of eq at 40hz playing program material, power needed at 40hz will be 4x of that needed everywhere else. So, at 100 watts, with 3db of eq, 400 watts will be needed for minimal headroom.
Where did I say EQ reduces power requirements? I agree that generally it increases them. However in this case we have some bins that will be affected by their environment quite strongly, and so the required EQ will vary. My suggestion for axeing below 40Hz, was assuming that this rig will be used in smaller venues, where the drum kit won't be played through them If there is no real LF energy below 40Hz (bottom E on a bass guitar), cut it, to stop any LF rubbish being played through your system. It will often clean up the sound considerably, and reduce amp power output, reducing distortion and increasing headroom for wanted signals.

When I said sensitivity should be about 100dB/W/m, I was actually factoring in about 6dB of low end boost to bring it to the roughly 106dB they will be from maybe 80Hz up.
Quote:
However, your SRM's are about 100 dB efficient from midbass +, and would need no more that 20 watts to blow you're head off. So, let's say you add 6 dB at 40 Hz, you would need 240 watts for the lows. 400 would be optimal for your price/performance ratio. You may need to reconsider your $400 window. Finding a decent 300-400 watt amp for less than that is hard unless you go used(which you probably should). Plate amps aren't a bad idea either, there is a thread posted by the one and only slicemaster101 concerning big, bad plate amps.
-andy
At 100dB/W (EQ included, see above), it won't be hard to use 400W in a medium/large club, with lots of lowend in the mix, and a densely packed room. Whether the mains will be able to keep up is another question, as I'm not fmiliar with what poor but proud has.

Second hand is a good idea for the amp, and will help keep the budget down, no matter what speaker is chosen. Buying from a reputable source like Jammin Jersey, you can probably get a reliable known brand amp for that. These boxes will sink over 1.5kW each, so a 400W amp is small, and even the 186's will do a lot more than the rating of the driver. The plates also might be a good option (if you get a good reliable one), because the bottom rear cormer of the LAB box is spare and it can save on speaker cables and rack space.

Cheers
Brett
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Old 21st July 2002, 02:36 AM   #25
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Sorry folks...

If you are using an amp as apart of your livelyhood I would never trust a plate amp... It may just be professional snobbery, but most plate amps,( or domestic amps for that matter), are just not reliable enough for the stresses required for live music, and personallly I would prefer to spend a little more money on something that would be there when I needed it...
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Old 26th July 2002, 03:31 PM   #26
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Seems to me that for best price to performance ratio, 186 horns w/ 18" driver and a used rackmount amp of medium high power (at least 400W @ 4ohms /side) is the way to go. Is there something that I am overlooking?

Brett-we are in agreement
-andy
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