I was reading a post on another board discussing how bl and mmd alone determine efficiency. Add in sd and you have spl. I read another post saying that compliance (cms and vas) have nothing to do with efficiency. What am I missing?

If I used dry wall instead of foam surround I don't think my efficiency will be very high.

 

efficiency:

[Output sound power (in watts) / Input electrical power (in watts)] x 100 %


I think just about any spec could change the efficiency of a speaker.
ie drywall vs. foam. hehe
not sure, but i would assume that a larger vas is going to be less efficient, than a smalller one. or maybe the exact opposite.
cms has to do with spring stiffness, or somelike that, so it should effect it too.

any one care to school us?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by vteg &raquo;</TD></TR><TR><TD CLASS="quote"> I read another post saying that compliance (cms and vas) have nothing to do with efficiency. What am I missing?

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Cms and Vas are proportional to each other. decrease the Cms and you also decrease the Vas. when you do this, the Fs raises. Fs is inversly proportional to Cms. yes you decrease efficiency when you lower the Vas, but you also gain efficiency because the Fs goes up.

 

by the way..you're thinking of sensitivity. efficiency and sensitivity are 2 different things. efficiency is the amount of electrical power converted into acoustic power. sensitivity is the spl of the point where electrical power is given.

 

Yet efficiency is related to sensitivity: more sensitivity, the more efficient the driver is to move air at lowr power.

Other variables to consider are air temperature, age of the speaker (has it even been broken in properly? When were the Ts parameters measured: new or broken in?)

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GSteg &raquo;</TD></TR><TR><TD CLASS="quote">by the way..you're thinking of sensitivity. efficiency and sensitivity are 2 different things. efficiency is the amount of electrical power converted into acoustic power. sensitivity is the spl of the point where electrical power is given.</TD></TR></TABLE>

I think efficiency and spl are related and proportional to each other, but not the same. Let's say you have two subwoofers, a 10 and 15. They both have the same motor, and mmd. Of course the 10's cone is much thicker or denser. The efficiency(force applied to mass) should be the same, but the spl on the 15 should be louder because of displacement.

Also if just dealing with bl and mmd, then just the motors ability to push the cone is in question. The output, or acoustic effienciency is directly related to spl right?

 

efficiency is expressed in percentages..sensitivity is expressed in db (1w/1m & 2.73V/1m

the 10" and 15" probably will be the same in efficiency (assuming same motor), but the 15" would be more sensitive. speakers/subs are not efficient at all. about less than 4% efficient. sent the sub 100 watts RMS and only 4 watts are converted into acoustic watts. the rest? wasted as heat (reason why we are so worried about thermal overloading)


the BL does affect spl. high BL's are favored a lot in SPL comps (take a look at the stroker ). not to say that low BL subs aren't good or anything like that.
i wouldn't think the BL or Mmd would affect the acoustic efficiency at all. sensitivity? more likely. i would highly recommend you talking to my good pal Stephan Ponte.