Xmax

dallaire · 24th December 2007, 09:48 PM

Hello again, I was wondering if someone had a link that would help me find out the amount of cone extention I will be placing on my four inch mids at a cross frequency of 300hz. I am using the Peerless four inch mid/woofer HDS PPB. Is there a simple formula for fig. for this? I am using two and wiring in parallel so my rotel anp will see about a four ohm load. The driver I am using says it has a linear excursion of +or- three mm, thats about all the info I can find on this driver on this parameter.

I'm sure this is dependant on volume level, I do listen to movies at reference levels, and like my music pretty much the same. Crossover is 24db per and electronic.
Thanks,
dallaire

Svante · 24th December 2007, 10:51 PM

Yes, the RMS cone amplitude for a given sound pressure p in free space is

x=p*4*pi*r/(Sd*w²*rho0)

r is the distance at which p is measured, w=2*pi*f, rho0=1.2 kg/m³

p can be derived from sound pressure level as p=pref*10^(Lp/20)

where pref=20 µPa, Lp is the sound pressure level in dB.

So, for example, if the Lp=94 dB, r=1 m, f=300 Hz and Sd=100 cm², then

p=2e-5*10^(94/20)=1 Pa

x=1*4*pi*1/(0.01*(2*pi*300)²*1.2)=0.294 mm

forr · 25th December 2007, 09:47 AM

Hi Dallaire,

Have a look at
http://www.linkwitzlab.com/sb80-3wy.htm
there's a handy formula from which you can derive cone excursion.

24th December 2007, 09:48 PM	#1
dallaire diyAudio Member Join Date: Nov 2007	Xmax Hello again, I was wondering if someone had a link that would help me find out the amount of cone extention I will be placing on my four inch mids at a cross frequency of 300hz. I am using the Peerless four inch mid/woofer HDS PPB. Is there a simple formula for fig. for this? I am using two and wiring in parallel so my rotel anp will see about a four ohm load. The driver I am using says it has a linear excursion of +or- three mm, thats about all the info I can find on this driver on this parameter. I'm sure this is dependant on volume level, I do listen to movies at reference levels, and like my music pretty much the same. Crossover is 24db per and electronic. Thanks, dallaire

24th December 2007, 10:51 PM	#2
Svante diyAudio Member Join Date: Feb 2004 Location: Stockholm	Yes, the RMS cone amplitude for a given sound pressure p in free space is x=p4pir/(Sdw²rho0) r is the distance at which p is measured, w=2pif, rho0=1.2 kg/m³ p can be derived from sound pressure level as p=pref10^(Lp/20) where pref=20 µPa, Lp is the sound pressure level in dB. So, for example, if the Lp=94 dB, r=1 m, f=300 Hz and Sd=100 cm², then p=2e-510^(94/20)=1 Pa x=14pi1/(0.01(2pi300)²1.2)=0.294 mm __________________ Simulate loudspeakers: Basta! Simulate the baffle step: The Edge

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25th December 2007, 09:47 AM	#3
forr diyAudio Member Join Date: Dec 2004 Location: Next door	Hi Dallaire, Have a look at http://www.linkwitzlab.com/sb80-3wy.htm there's a handy formula from which you can derive cone excursion.