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How many watts?

tajanestajanes
in DIY

a) Can someone plz calculate watts necessary to max out a MCM 8in 55-5670 in a closed box and/or aperiodic box set-up? (the speaker will be bi-amped, so an amp channel will be exclusive to this woofer), and

b) in general (not necessarily directed to the above driver) suggestions / comments on how much amp ‘headroom’ would you recommend for say a 3 way? ( I realize power requirement its subject to driver sensitivity, but overall looking for ways to target headroom).

I'm thinking 2x watts (to max out a driver) is a fair amount of headroom to target, but I've seen articles that are all over the place.

thx

Comments

  • Ed_PerkinsEd_Perkins

    What exactly do you mean by max out? Do you mean reach x-max excursion? The size (and resulting Q factor) of the box will determine when & where X-max will occur. If you throw the 55-5670 into WinISD it will calculate a closed box with a Q of about 0.707 and with a volume of 16.5 liters. In that box you'll reach X-max with 50W, but not until 10 Hz. On the other hand, if you make the box 1/2 the size (8.25 liters, Q = 0.906) X-max is still reached at 10 Hz, but at 110 W, well beyond the driver's 80W rating. WinISD is a quick way to check out all these things and there's a tutorial for it right here on this site by none other than JR.

  • tajanestajanes

    Ed, thx for your help with this. My older Mac doesn't do WinISD, and the Parralles / Window software didn't take to well either.

    I was looking at a multi channel amp that's rated 130w RMS per channel, and will be crossing over to a sub preferably around 60Hz. Curious if the WinISD would show if I could push (if needed via dsp) this driver at say 60 Hz +3db, or perhaps it might show how many watts maxes excursion at 60 Hz?

    In any event, thanks again for your time and info !

  • JasonPJasonP

    I tossed the published specs into Unibox. Here is my result given a 13L sealed box, and 80 watts input power:

    That red line is the maximum output SPL for the displacement of the driver within it's 7.5mm xmax.

    If you want me to model more I can.

    = Howard Stark: "This is the key to the future. I'm limited by the technology of my time, but one day you'll figure this out."
  • JasonPJasonP

    Also, a neat tool with less graphics showed up for me in a google search years ago: baudline.com/erik/bass/xmaxer.html

    It'll calculate displacement limitations for drivers assuming no box help (vented, etc.)

    = Howard Stark: "This is the key to the future. I'm limited by the technology of my time, but one day you'll figure this out."
  • JasonPJasonP

    At 160 watts:

    It meets displacement limits at roughly 80hz, but if you are crossing at 60 hz it'll have reduced output already. So in regards to excursion, 160 watts crossed over at 60hz looks fine to me.

    = Howard Stark: "This is the key to the future. I'm limited by the technology of my time, but one day you'll figure this out."
  • tajanestajanes

    Jason,
    Perfect. Thx (and thx for the link)

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