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Driving Subs - Stereo or bridged mono?

Peter.GordonPeter.Gordon Posts: 14
edited June 2011 in PA Connectivity
G'day all.

I'm a little (lot) confused whether to run my subs in stereo or bridged mono.

My subs are Seer Audio PSII-600 (Chinese copies of something else I believe) , Specs below;

Frequency Response:45Hz-250Hz
Impedance :8 ohms
Long-term Power(RMS):600W
Power Peak :1200W/5Min
Sensitivity :100dB(2.83v/m)
Maximum SPL :116dB
Connection :2×NL 4 speakon
Low :18 IN×1(460mm)
N.W. :43kg

My amps (Quest 3004) are quoted at 8ohm - 660W per channel @ 1kHz at <0.05% T.H.D. both channels driven @ 8ohm & 1100W per channel @ 1 kHz at <0.05%T.H.D. both channels driven @ 4ohm.

No figures are given for bridge mode, but the manual states the following;

"Power is proportional to the square of the voltage swing, so four times the output power is possible. The reality is that this would exceed the capability of the output stage but a considerable increase in output will result all the same.

The recommended load impedance is 8Ω in bridge mono mode but a speaker load of 4Ω will be satisfactory under most circumstances".

Now, my way of thinking is that in the real world, away from test equipment, even if the amp was capable of 2000W in bridge mode there would be little change to perceived volume and the amp would run cooler in stereo?

Is there any reason to change this way of thinking?




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    GadgetGadget Posts: 4,915
    Hi :mrgreen:
    Well, usually when they build an amp and give it a model Like "3002" it means @4 ohms (or 2 ohm stereo) the amp will put out 3000 watts or 2X1500 watts respectively...

    Now, if you have 2, 8 ohm speakers and you are then feeding each cabinet 1500 watts...in bridged mono...

    It is said that the human ear can hear a 2dB change and that a 3dB change is a relative doubling of the sound (but actually it takes 4-6 dB to accomplish that...

    However, to get twice as loud you need 10X the power...or, if you have 1000 watts to get 2X as loud you would need to have 10,000 watts

    Now, those speakers are not really subs at all.. they are bass speakers and if they will only handle 1200 watts peak you better not go that route or your going to cook those voice coils...especially if this is heavily compressed recorded music...

    Live sound requires a lot more dynamics.. so in the right situation.. that 1500 watts per could be just the ticket... but then again you need to be careful...
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    OklaPonyOklaPony Posts: 48
    Maximum SPL :116dB

    You think that's actually accurate?
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    DraDra Posts: 3,777
    1200w would give it a hair over 130db max.

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    GadgetGadget Posts: 4,915
    Sorry Dra.. I disagree here
    116dB probably accurate.. long term...maybe 118-120 with boundaries..
    130dB that thing would FLY APART in short order
    Your using gain not figuring on efficiency, loss and power compression

    MAYBE if there were 6 ground stacked against a wall...

    But the 116dB figure is for 1 speaker in full space I assume.

    I'm betting a 3" voice coil stamped basket driver...and I am betting that is a "program rating, not an RMS one.
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    DraDra Posts: 3,777
    Sorry, didn't mean to imply that you would get 130db. Only that the math (and that is how almost everyone lists there output) says that is the number. I aggre that the verbage and the numbers don't mesh with typical terminology.

  • Options
    Holy Mother of God! I developed a buzz in one of the subs that I thought for all the world was a blown speaker.

    Opening up the side of the box I found an 18" speaker with an 8 legged cast frame you could use as a car wheel! BTW, the magnet on the back was 12" across with a 4" hole in the middle.

    The Buzz turned out to be loose screws holding one of the mesh grills in place. :-)

    Sometimes the Gods smile on me ;-)
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