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Smaller bridged amp vs larger amp connected in stereo?

Discussion in 'Amps [BG]' started by sears, Dec 7, 2013.

  1. sears

    sears

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    I just got an Acme B2 series II, 8 ohms and am planning a modular system around it. Maybe getting another one down the road. An amp to send 5-600 watts into each cab.

    1. A stereo setup like the QSC 1804 is the obvious choice. 550 wpc at 8 ohms. Use one side until I get another cab.

    2. The less expensive Crown XLS1000 sends 700w to 8 ohms in bridged mode. If I were to get another 8 ohm B2 couldn't I daisy chain the cabinets, creating a single 4 ohm entity that the XLS1000 would send 1100 watts to?

    In the real world, is option 1 going to get you better results than running an amp closer to its limit as in option 2? Will the speakers respond the same daisy-chained or would they rather be hooked up each to a channel?
  2. Zooberwerx

    Zooberwerx Gold Supporting Member

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    Yes, this is a reasonable option. I'd spend the extra $$ and snag a 1500 or 2500 (I have both). As I understand it, bridged mono better accommodates the wider voltage swing of a single 8 ohm enclosure. That being said, I use a bridged mono 1500 or 2500 to power (2) 8 ohm Acme B-2's, 8 ohm HyDrive 410, or 5.2 ohm LDS 8 X 8. I use the same amps (bridged) to run dual 8 ohm mains and subwoofer (daisy-chained, of course). I keep an eye on things and come nowhere close to approaching the limits on any component. I did send one XLS into protective shut-down (I think) by intentionally clipping the amp (no speakers attached!) during gain structure set-up but that was an extreme situation.

    Your speakers won't know the difference. Do read all you can on appropriate set-up applications...stupid behavior results in component damage / failure.

    Edit: maybe I shouldn't say "stupid". Let's leave it at "pushing any component beyond its design limitations will result in damage / failure".

    Riis
  3. Marko5657

    Marko5657 Supporting Member

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    Just know that two 8-ohm cabs (4ohms) on bridged-mono is a 2-ohm load on the amp.
  4. BassmanPaul

    BassmanPaul Gold Supporting Member

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    Per channel yes. If the amp is not safe at 2Ω per channel it cannot be bridged into 4Ω.

    Zooberwerx and I have disagreed on this subject in the past and I guess we still do! :D

    I have never felt the need to bridge any of my amplifiers. I use one or two B2 cabinets from each channel of my amps. The amps are set to run in parallel mono. I have never wanted for volume. I consider putting five or six hundred watts into a cabinet rated at 350W dangerous for that cabinet. It's simply too easy for things to get out of hand in the midst of a gig or even by accident.

    As posted, bridging is about getting a larger voltage swing across a higher impedance load. It's not about wringing every last watt out of an amplifier.
  5. Zooberwerx

    Zooberwerx Gold Supporting Member

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    ^^ Paul also drives 42 mph in the fast lane while en route to the hockey game. That was particularly satisfying as I've reinforced stereotypes concerning (a) anybody over the age of 65 and (b) Canadians.

    My LDS (5.2 ohms) is a better example as it is rated at 1000 watts.

    In all fairness, I am playing the South Norfolk Moose Lodge tonight...laugh away!

    Riis
  6. sears

    sears

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    If 4 ohm bridged mono = 2 ohm load on each channel, then that's back to my original question. Is that bad for the amp? Is it preferable to spend a little extra and use one stereo channel for each 8 ohm cabinet?

    If Crown says the XLS is capable of delivering a signal to a 4 ohm load in bridged mono mode (say 1100 watts) then does it matter if it's seeing one 4 ohm cabinet or two daisy chained 8 ohm cabs?

    As far as overpowering it, all of the amps I'm considering have attenuator dials. Given the debate on overpowering Acme cabs, if I CAN overpower them safely (by attenuating the signal) can't I work my way up to a comfortable, safe volume?

    Finally, if I choose to bridge, I would use a special bridging speakon cable to connect the first speaker to the amp. Would I daisy chain the Acmes by using 1/4" speaker cable from the input of one to the input of the second?
  7. Zooberwerx

    Zooberwerx Gold Supporting Member

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    The DriveCore is rated to 2 ohms/ side so you'll be okay. Conventional wisdom holds that running one channel / one enclosure puts less of a demand on the plant. Personally, I'd go with the 2500 which kicks ~450 watts / channel 8 ohm...more power, more options in terms of application, and still well below $500.

    The XLS doesn't care whether it sees a single 4 ohm enclosure or daisy-chained 8 ohm enclosures.

    Volume is a function of preamp input and attenuator settings. Note: any power amp is capable of providing max output if given a hot enough signal, irrespective of attenuator settings.

    Yes, a bridge cable is required for said mode...you can make your own. I prefer a standard Speakon >< Speakon cable when daisy-chaining, not the 1/4" phono plugs.

    Riis
  8. BassmanPaul

    BassmanPaul Gold Supporting Member

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    Closer to 142 on the 401, our highway through the city. Well 120 if truth be told.

    I do not share the passion of my adopted country for Hockey.

    Riis I have played more than a few Moose Lodges myself. I didn't laugh, I emphasized! :D
  9. Zooberwerx

    Zooberwerx Gold Supporting Member

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    The Queen's Highway, correct? Used the route from Cornwall to Montreal back in the day.

    You can still smoke in the US based lodges but it is verboten in Canada as it is still considered a public place.

    Riis
  10. BassmanPaul

    BassmanPaul Gold Supporting Member

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    Part of the 401 has been named The "Highway Of Heroes" as the military fatalities from Afghanistan are brought from Trenton Air force base (I've played there) to downtown Toronto for autopsy.

    Not too sure about Canada as a whole but certainly within the city of Toronto smoking is banned. It has caused a big decline in the cities music scene. Fortunately I only smoke in bed! :D
  11. Zooberwerx

    Zooberwerx Gold Supporting Member

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    You mean even outside?!?

    "Highway of Heroes" is duly noted.

    Riis

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