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Amp for running 6x Oberton XB1500

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junoprobelaunch View Drop Down
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    Posted: 11 October 2018 at 4:16am
Hi
Soon I will be looking to purchase a high power sub amplifier to power six WSXs modded to fit an Oberton XB1500. I was originally looking at an FFA 10000 but upon realising that the Obertons were in fact 1500watts, I am back to the drawing board! I intend to purchase this amp second hand and have a budget of around £1200-£1600 (so not a K20 ;-;). Have looked at an E90 but people on here don't have alot of good things to say about them!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote White Noise Quote  Post ReplyReply Direct Link To This Post Posted: 11 October 2018 at 7:16am
We have used FFA 10k for 1700 w b&c's before now... surprising how much punch they pack


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Post Options Post Options   Thanks (0) Thanks(0)   Quote junoprobelaunch Quote  Post ReplyReply Direct Link To This Post Posted: 11 October 2018 at 12:25pm
How would you actually run them though? At 4r you wouldn't be giving them any headroom and at 2.66 you'd be underpowering
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corell View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote corell Quote  Post ReplyReply Direct Link To This Post Posted: 11 October 2018 at 2:44pm
there is no such thing as underpowering in Speakers.
Even the often repeated danger of clipping is only a Problem because it may decrease the crest factor from 1,41 (sine wave) down to almost 1 and therefor, the amp might actually overpower the Long term handling of the Speaker when the limiters were set for program power.
In a Front Loaded Horn however, you Need to set a RMS or true power limiter at 1/3 of RMS power handling, otherwise you will burn your Speakers with heavy bass Music material.
so following the same rule most People suggest (having double the power / +3dB headroom for the Peaks in the Signal above Long term power handling), you would be looking for an amp capable of 3000w per channel into 2,7 Ohm.

Please note that i personally will say (and have allready said and beeing shot down for it) that there is no sense behind the "double rms power for amps" rule. Sure, it is crucial to have headroom! But +3dB? thats a joke when you look at Music waveforms. Either go 6-10dB (surprisingly, thats how the pros run their rigs, amp max output vs. Long term power to the speakers...)or you might aswell just go for a cheaper amp with 0db headroom above RMS power handling. Thats just my opinion though!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 11 October 2018 at 3:10pm
1/4 power for horns, 1/3 for reflex is my general rule. Or less. It depends on the box.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote junoprobelaunch Quote  Post ReplyReply Direct Link To This Post Posted: 11 October 2018 at 3:14pm
Originally posted by corell corell wrote:

there is no such thing as underpowering in Speakers.
Even the often repeated danger of clipping is only a Problem because it may decrease the crest factor from 1,41 (sine wave) down to almost 1 and therefor, the amp might actually overpower the Long term handling of the Speaker when the limiters were set for program power.
In a Front Loaded Horn however, you Need to set a RMS or true power limiter at 1/3 of RMS power handling, otherwise you will burn your Speakers with heavy bass Music material.
so following the same rule most People suggest (having double the power / +3dB headroom for the Peaks in the Signal above Long term power handling), you would be looking for an amp capable of 3000w per channel into 2,7 Ohm.

Please note that i personally will say (and have allready said and beeing shot down for it) that there is no sense behind the "double rms power for amps" rule. Sure, it is crucial to have headroom! But +3dB? thats a joke when you look at Music waveforms. Either go 6-10dB (surprisingly, thats how the pros run their rigs, amp max output vs. Long term power to the speakers...)or you might aswell just go for a cheaper amp with 0db headroom above RMS power handling. Thats just my opinion though!

While I agree that double RMS + 3db is an extorniate amount of power to feed drivers, I struggle to believe that any more than 1/3 would kill drivers. I generally feed mine 1.5x RMS with careful limting settings.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote junoprobelaunch Quote  Post ReplyReply Direct Link To This Post Posted: 11 October 2018 at 3:16pm
Originally posted by toastyghost toastyghost wrote:

1/4 power for horns, 1/3 for reflex is my general rule. Or less. It depends on the box.

This goes against everything I've ever read regarding how much power to feed drivers ! So you're suggesting I feed the Obertons 375 watts of power? That seems crazy!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote junoprobelaunch Quote  Post ReplyReply Direct Link To This Post Posted: 11 October 2018 at 3:21pm
Or were you refering to their program power meaning you reccomend 1000? Seems a bit less baffling but even still...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Timebomb Quote  Post ReplyReply Direct Link To This Post Posted: 11 October 2018 at 4:48pm
He is referring to long term RMS "power",  an 1000W AES rated driver with say 5.2 ohm RE cold is tested at 72V RMS, when you consider how much resistance increases when the driver is pushed close to the edge the actual current flowing is not so much,  you can blow a 1000W rated driver with 3-400W of actual power, or less.  

Big amps are great for high output as actual program material has a high crest factor, but it is still best to use an RMS limiter set much lower so you dont feed the drivers too much power.
James Secker          facebook.com/soundgearuk               www.soundgear.co.uk
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Timebomb Quote  Post ReplyReply Direct Link To This Post Posted: 11 October 2018 at 4:51pm
A lot of the time when people say "i feed x drivers with 1000W" thats not really whats happening,  it might be an amp capable of giveing 90V rms at 8 ohms / "1000W"  at clip but with signal crest factor and resistance rise they might only be getting 100W of actual power.  
James Secker          facebook.com/soundgearuk               www.soundgear.co.uk
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Post Options Post Options   Thanks (0) Thanks(0)   Quote junoprobelaunch Quote  Post ReplyReply Direct Link To This Post Posted: 11 October 2018 at 4:53pm
So how is one supposed to work out how much power is optimal to feed drivers?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote junoprobelaunch Quote  Post ReplyReply Direct Link To This Post Posted: 11 October 2018 at 4:55pm
Thank you though Time bomb that was very helpful
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