Per and Par

[Top Shelf]

Hey everybody,glad to finally have something to ask. I recently modeled two subs, RCF LF18x400 and a Peavey 18" Low Rider. I use an online calculator called Ishtek. Two of the summary parameters are Par and Per, I take it from other sources that Par is the actual acoustic level (in watts) coming from the speaker?? And Per is the wattage that it takes to get that level??? Is this correct, or close to?
Only reason i ask is that the RCF's Par is 6.5 watts and the Peavey's is 11.6 watts, respectivly the Per's are 227 watts and 450 w?
Does this mean if I dump 456 watts into the RCF the Par will double too? Do these two terms have any real bearing in designing,or not?
Thanks for any input.

[godfrey]

That Ishtek calculator makes no sense to me and doesn't seem overly useful either.

Why not use something that works a bit better?

[soho54]

PAR is the peak acoustic power that may be produced at the speaker displacement limit (Xmax)

PER is the electrical power to produce PAR (note, this can be greater or smaller than the speakers thermal capability

ISHTEK Speaker Design
Bottom of page.

[soho54]

I would use one of these programs instead.

This one is stand alone.
LinearTeam

This one requires Excel
UniBox - Unified Box Model for Loudspeaker Design - Kristian Ougaard

[Top Shelf]

Thanks Soho, I didn't see that there So if I put more power than Per into the specified enclosure than I will exceed the displacement limited power handling's xmax and will only see more distortion and perhaps mechanical damage....so the thermal handling far exceeds the mechanical ability???? Seems like a waste of a driver I guess the Peavey with its higher Per and Par would be a wiser choice for a driver then ,given that I want to have a 7 cu.ft box. I would still like to know if these are truly relevent parameters even though I will probably be going to another program?? Thanks again for the help

[godfrey]

Originally Posted by soho54

PAR is the peak acoustic power that may be produced at the speaker displacement limit (Xmax)

PER is the electrical power to produce PAR (note, this can be greater or smaller than the speakers thermal capability

ISHTEK Speaker Design
Bottom of page.

Yes, but it calculates PER from the efficiency you type in, so it's guess is only as good as yours.
Decent software should be able to calculate the efficiency (and display the frequency response etc)

Originally Posted by Top Shelf

... I will probably be going to another program...

Yee-ha! Now you're getting somewhere.
(Thanks for links, Soho)