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SVS CS-Ultra.... Where's the power?

Discussion in 'Subwoofers' started by galewis1, Jan 21, 2005.

  1. galewis1

    galewis1
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    I finally managed to put enough cash away to buy a power amp to drive my CS-Ultra that I acquired a few weeks ago. However, I think something is wrong as I'm not getting much output from the SVS.:(

    I bought a Behringer EP2500 power amp which is rated at 700wpc into 4 ohms (the CS-Ultra needs 500w @ 4 ohms) and connected it downstream of my Arcam AVR300 using a 75ohm RCA phono > TRS 1/4" jack (made up by the cable guru, Mark Grant of these very forums. This connects from the RCA sub-out of AVR300 to Input 1 on the Behringer EP2500.

    I'm then using about 3 metres of some old QED 79 strand speaker cable to connect from the Behringer to the SVS.

    With the AVR300 volume set to '80', I'm finding that I have to turn up the gain on the EP2500 to about 180 degrees to get any decent
    output from the SVS. The Behringer has an indicater light that lights up
    (annoyingly) when it's getting an input signal. It doesn't light up at all until I
    turn the gain up at least 90 degrees, then it starts to flicker to life.
    I've even tried it in bridged mono (2400w into 4 ohms :eek: ), but it made very little, if any difference. I would have thought with that much power on tap that I'd hardly have to touch the gain control on the Behringer to really feel the action.

    On the AVR300, my main speakers (KEF XQ1's) are set to small and sub cross-over is set to 100hz. I've tried playing around with the settings, but with no real benefit.

    There are also some jumper settings on the back of the EP2500 including a
    Clip Limiter and Low Cut Filter which, if switch on can be set at 30Hz or 50Hz. I've played around with these and I can't really tell much of a difference.

    I know the Arcam is OK because it was working fine with my recently retired KEF sub.
    The EP2500 appears OK. If the input light is barely flickering then that's why there's not much output to the SVS right?

    The way I see it, it's either some setting within the AVR300 that I'm not setting correctly, the sub cable not suitable/wired wrongly (doubtful on the second part since it's a Mark Grant) or perhaps something wrong with the input side of the Behringer.

    Any ideas anyone. I'm really gutted.... I was expecting to be blown away by the power of the SVS. :lease:


    Cheers

    Gary
     
  2. stonking

    stonking
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    Mute button pushed in?
     
  3. Nimby

    Nimby
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    Let's try and isolate where the problem lies:

    Just try bunging the CSU on the end of any amplifier mono channel via speaker cable and feed it a full range music signal. If the CSU doesn't frighten the hell out of you then there is a problem with the CSU.

    The CSU has a large enclosure and should be efficient enough to frighten the neighbours three doors down on 60 Watts. Higher power amps should simply give you tighter and more dynamic bass transients. But it isn't absolutely necessary for a full bass performance. Remember that most large hifi speakers are only using under 100watt stereo amps. Just think of the CSU as just another (mono) speaker woofer. (one that bites) :devil:

    Nimby
     
  4. galewis1

    galewis1
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    Thanks Nimby...


    I'm working on the theory that the EP2500 is a professional amp that is expecting a higher gain input than you would get on a consumer amp LFE output (something in the order of +14db I understand).

    This means 'up' ing the LFE trim (max i think is +10db on the AVR300) which does appear to work... Whether that's the correct resolution to the problem is another matter.... I'll post back when I find/work it out.

    Appreciate your response all the same...

    Thanks

    Gary
     
  5. ailean

    ailean
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    Bingo Gary!

    Yes pro audio line levels are higher, some Behringer gear can be switched to consumer levels which can help, but I doubt the poweramps have this feature.

    Keeping the filters off and increasing the output gain on your processor should help, but may add distortion at high gains.

    Because your processor is only passing <100Hz signals to the amp the led will probably not register as much as when receiving a full bandwidth signal, it should still flicker most of the time thou as bass signals are more sporadic (sp) in most soundtracks.

    And yeah these leds can be rather distracting in home use. ;)

    The usual soundlevel measurements should of course help you verify it's balanced with the rest of your speakers.

    Oh and welcome to Club SVS! :cool:
     
  6. Tom Vodhanel

    Tom Vodhanel
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    Hi Gary,

    If you are still having problems, email me at SVS techsupport. Radio Shack has an inexpensive ($39-49 ) preamp that should solve your problems and I do believe it is available in 220v too.

    Tom V.
    SVS
     

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