Bass Shaker Pro installation question

Discussion in 'Speakers' started by oppie, Jun 9, 2005.

  1. oppie

    oppie Auditioning

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    I searched and read all the other posts on these but they dont seem to answer the question i have.

    I just got 2 of the 50W RMS Pro Bass shakers.
    I have the Aura Amp-75 to power them, which is 100W.
    Specs say 60W RMS mono @ 4 ohm
    and 85W RMS Peak mono @ 4 ohm

    I want to wire this up right. So would it be series or parallel??

    I think it should be series right? But is the 8ohms it produces ok for the amp?

    Thank in advance for all your help
    dan
     
  2. Eric Hargrove

    Eric Hargrove Stunt Coordinator

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    When i measured my Aura pro bass shakers, They were roughly 3.5 ohms each. Parallel wiring would equal a 1.75 ohm load at the amp which is mostly likely too low. Your only choice if this is a single channel mono amp, which it sounds like it is, is to wire your shakers in series.
     
  3. oppie

    oppie Auditioning

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    Hey thanks for the reply...

    I also just got this answer from aura themselves...

    ""Either way is fine…parallel will get you more power though…the resistance should be a bit above 2 ohms…""

    But in your test the ohms were lower huh. I also always thought i should be doing series.

    It is a single channel amp
     
  4. Eric Hargrove

    Eric Hargrove Stunt Coordinator

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    Yeah, when I measured with an ohmeter, they were lower. If Aura says they can be run in parallel off that amp, I would give it a shot. Don't be too surprised if the amp runs pretty warm though...
     
  5. oppie

    oppie Auditioning

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    Is that going to cause the amp to burn out sooner or anything like that? No fire risks though right?

    thanks a ton for your help i think i am going to start installing these today.....

    Guess i will try parallel first

    thanks
    dan
     
  6. Eric Hargrove

    Eric Hargrove Stunt Coordinator

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    Yes, it could cause the amp to burn up. Most amps are not rated for that low of impedance. Series wiring is definitely going to be easier on the amp. The only downside to series wiring would be less overall power.
     
  7. Dick Boneske

    Dick Boneske Stunt Coordinator

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    Just remember, DC resistance measured with a meter is NOT the same as speaker impedance seen by the amp. Most 8 ohm speakers measure 3-6 ohms DC. Most 4 ohm speakers measure 1.5-3 ohms DC.

    Based on that, these will look like a 4 ohm load to your amp if you parallel them. It really doesn't matter, as for any given power level (watts), the amp will work as hard if they are in parallel or series. A high quality amp will drive these in parallel with no problem.

    Hope this helps.
     
  8. Eric Hargrove

    Eric Hargrove Stunt Coordinator

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    Hi Dick,

    I agree with you. The impedance of a speaker (in this case a transducer) is not static, it varies with frequency.

    8 ohm drivers measuring 3-6 ohms and 4 ohm drivers measuring 1.5-3 ohms has not been my experience. While they often times measure a bit lower than their stated impedance, they are usually close. My Aura Pro bass shakers are rated at 4 ohm and when measured with an HP 3458A DMM in a 4-wire configuration measure 3.5 ohms each. Based on 3.5 ohms for each transducer, parallel wiring for this example would be 1.75 ohms not 4 ohms. The only way to get to 4 ohms with this example would be to parallel two transducers that measured 8 ohms to begin with.

    In Dan's correspondence with Aura, they state parallel or series are both acceptable. That tells me the amplifier has a pretty stout power supply. The load at the amplifier does matter. The amplifier will be working harder and running warming in parallel. This is because halving the impedance is asking for double the current from the amplifier. If the amplifier can supply this added current, the amplifier will produce more power. If it cannot, it will either shutdown or go into protection mode until the load returns to an acceptable level for the amplifier.

    There are additional issues with parallel wiring I did not take the time to address like the corresponding decrease in damping factor. It is probably not a big issue in this application as these are tranducers that shake what they are attached to instead of producing sound like a speaker.

    My advice, use series wiring unless you feel more output is needed.
     
  9. Frank.C

    Frank.C Auditioning

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    Here is a silly question.

    What is parallel and what is series, and how do you wire them?

    I'll be buying either 2 or 4 shakers in the near future. (As soon as I can figure this thing out).

    PS. Now I know the shakers need their own amp. Thanks.
     

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