posted
found this on another forum and thought it would make me look smart......hahahahah
To calculate the power response of a ported enclosure system, you will need to know the following: Vas = equivalent compliance of driver (litres) Qes = electrical Q of driver at resonance Fs = resonance frequency of driver (Hz) PEmax = maximum input power for driver Fb = resonance frequency of the system F3 = frequency at which response is down by -3dB Dia = effective driver diameter driver (cm) Xmax = peak linear displacement of driver cone (mm) then,
pi = 3.14159265359 c = speed of sound in air (345 m/s) Ro = density of air (1.18 kg/m^3) n0 = free-air efficiency of driver SPL = SPL of driver @1W/1M Par = maximum linear power output Per = electrical input required to produce Par PeakSPL = Thermally-limited SPL in passband
Maximum output at a given frequency F can be calculated as follows:
Fn2 = (F/Fs)^2 Fn4 = Fn2^2 A = (Fb/Fs)^2 B = A/Qts+Fb/(Ql*Fs) C = 1+A+(Vas/Vb)+Fb/(Fs*Qts*Ql) D = 1/Qts+Fb/(Fs*Ql) E = (97/49)*A dBmag = 10*LOG(Fn4^2/((Fn4-C*Fn2+A)^2+Fn2*(D*Fn2-B)^2)) Pmax = (K1/n0)*((Fn4-C*Fn2+A)^2+Fn2*(D*Fn2-B)^2) /(Fn4-E*Fn2+A^2) SPLmax = K2+10*LOG(Fn4^2/(Fn4-E*Fn2+A^2)) SPLtherm = PeakSPL+dBmag
where,
SPLmax = displacement-limited SPL at frequency F (dB/1M) SPLtherm = thermally-limited SPL at frequency F (dB/1M) -------------------------------------------------------- To calculate the frequency response of a ported enclosure system, you will need to know the following: Vb = net box volume (litres) Fs = driver resonance frequency (Hz) Qts = driver Q at system resonance Fb = box tuning frequency (Hz) Ql = box losses (Ql=7 can be assumed for most cases) then,
Fn2 = (F/Fs)^2 Fn4 = Fn2^2 A = (Fb/Fs)^2 B = A/Qts+Fb/(Fs*Ql) C = 1+A+(Vas/Vb)+Fb/(Fs*Qts*Ql) D = 1/Qts+Fb/(Fs*Ql) dBmag = 10*LOG(Fn4^2/((Fn4-C*Fn2+A)^2+Fn2*(D*Fn2-B)^2)) ------------------------------------------------------------------------------------------------------------------
To calculate the power response of a 4th order bandpass system, you will need to know the following: Vas = equivalent compliance of driver (litres) Qes = electrical Q of driver at resonance Fs = resonance frequency of driver (Hz) PEmax = maximum input power for driver Fb = resonance frequency of the system F3 = frequency at which response is down by -3dB Dia = effective driver diameter driver (cm) Xmax = peak linear displacement of driver cone (mm) Vr = net volume of sealed section (litres) Vf = net volume of vented section (litres) then,
pi = 3.14159265359 c = speed of sound in air (345 m/s) Ro = density of air (1.18 kg/m^3) n0 = free-air efficiency of driver SPL = SPL of driver @1W/1M Par = maximum linear power output Per = electrical input required to produce Par PeakSPL = Thermally-limited SPL in passband
Maximum output at a given frequency F can be calculated as follows:
Fn2 = (F/Fs')^2 Fn4 = Fn2^2 A = (Fb/Fs')^2 B = A/Qts'+Fb/(Ql*Fs') C = 1+A+(Vas'/Vb')+Fb/(Fs'*Qts'*Ql) D = 1/Qts'+Fb/(Fs'*Ql) E = (97/49)*A dBmag = 10*LOG((A*Fn2)^2/((Fn4-C*Fn2+A)^2+Fn2*(D*Fn2-B)^2))) Pmax = (K1/n0)*((Fn4-C*Fn2+A)^2+Fn2*(D*Fn2-B)^2)/(Fn4-E*Fn2+A^2) SPLmax = SPL+dBmag+10*LOG(Pmax) SPLtherm = PeakSPL+dBmag
where,
SPLmax = displacement-limited SPL at F (dB/1M) SPLtherm = thermally-limited SPL at F (dB/1M ---------------------------------------------------------- To calculate the frequency response of a 4th order bandpass system, you will need to know the following: Vf = net front volume (litres) Ff = front volume tuning frequency Vr = net rear volume (litres) Fs = driver resonance frequency (Hz) Qts = driver Q at system resonance Ql = box losses (Ql=infinite (10000) can be assumed for most cases) then at frequency F,
A = (1/Ff)^2*F^4 B = ((1/Ql+(Fs/Ff)/Qts)/Ff)*F^3 C = (((1+Vas/Vr+Vas/Vf)*Fs/Ff+(1/Qts)/Ql)*Fs/Ff+1)*F^2 D = ((1/Qts+(Fs/Ff)/Ql*(Vas/Vr+1))*Fs)*F E = (Vas/Vr+1)*Fs^2 G = A-C+E H = -B+D dBmag = 20*log(F^2/(G^2+H^2)^.5) ------------------------------------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------------------------------------
Port Length The port length required to tune a volume of air to a specific frequency can be calculated by using the following equation: Lv = (23562.5*Dv^2*Np/(Fb^2*Vb))-(k*Dv)
where,
Dv = port diameter (cm) Fb = tuning frequency (Hz) Vb = net volume (litres) Lv = length of each port (cm) Np = number of ports k = end correction (normally 0.732)
The value for k, the end correction, can be fine-tuned by using the following values to derive the appropriate end correction figure for each end of the port, then adding them together
Flanged End: 0.425 Free End: 0.307
e.g. if both ends were flanged, k = 0.425 + 0.425 = 0.850
if one flanged, one free, k = 0.425 + 0.307 = 0.732
if both ends were free, k = 0.307 + 0.307 = 0.614
Normally, k=0.732 is assumed
In practice, it's best to use ports that are slightly longer than predicted by the above equations, then adjust their length until the correct tuning is achieved. It is much easier to shorten a port than to lengthen it!
Minimum Port Diameter To calculate the minimum diameter of the port required to prevent port noises, you will also need to know the following:
Xmax = maximum linear displacement (mm) Dia = Effective diameter of driver (cm) Np = number of ports
Calculate the minimum port diameter from the following equations:
Note: You CAN use ports that have a smaller diameter than that given by the equation above, especially if the ports are flared at both ends. However, at higher volumes, you may notice some port noise caused by the air rushing through the ports.
Slot Ports If you wish to use a slot port, first determine the diameter of a round port that has the same cross-sectional area as the slot. The following equation can be used to do this:
Dv' = 2*((W*H)/pi)^0.5
where,
Dv' = diameter of equivalent round port W = width of slot H = height of slot
Once you've calculated Dv', you can use it in the equation for Lv above to determine the required length of the slot port to tune the enclosure to the required frequency (Fb) ------------------------------------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------------------------------------
To calculate the power response of a sealed enclosure system, you will need to know the following: Vas = equivalent air compliance (litres) Qes = electrical Q of driver at resonance Fs = resonance frequency of driver (Hz) PEmax = maximum input power for driver (W) Fb = resonance frequency of the system (Hz) Qtc = final Q of the system at resonance Dia = effective diameter (cone + 1/3 surround) (cm) Xmax = peak linear displacement of cone (mm)
pi = 3.14159265359 c = speed of sound in air (345 m/s) Ro = density of air (1.18 kg/m^3) n0 = free-air efficiency SPL = driver output @1W/1M Par = maximum linear power output Per = electrical input required to produce Par PeakSPL = Thermally-limited SPL in passband
SPLd = displacement-limited SPL at F (dB) Pmax = power required to produce SPLd at F (W) SPLt = thermally-limited SPL at F (dB) -------------------------------------------------------- To calculate the frequency response of a sealed enclosure system, you will need to know the following: Fb = resonance frequency of the system Qtc = Final Q of the system at resonance
F = frequency (Hz) dBmag = SPL 1W/1M at frequency F ------------------------------------------------------------------------------------------------------------------- Just for you guys who dont trust the programs(like winISD,ect...)and want to do the math
-------------------- 12 VOLTS BABY!!!!! TEAM STETSOM USA & SALES REP TEAM STINGER BUY OHIO GENERATORS WORLD FINALS COMPETITOR 2005,2006,2008,2009 SUPER STREET 1-2 CERTIFIED 161.0 DB MARYLANDS LOUDEST DAILY DRIVER N.S.P.L. STATE RECORD HOLDER 2005,2006,2007,2008,2009 TEAM USAudio Stetsom Sales and Service stetsomrep1@hotmail.com Posts: 2226 | From: Maryland | Registered: Oct 2005
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quote:Originally posted by Mabeita: You thought wrong...
Yea the story of my life.....harumph!!!
-------------------- 12 VOLTS BABY!!!!! TEAM STETSOM USA & SALES REP TEAM STINGER BUY OHIO GENERATORS WORLD FINALS COMPETITOR 2005,2006,2008,2009 SUPER STREET 1-2 CERTIFIED 161.0 DB MARYLANDS LOUDEST DAILY DRIVER N.S.P.L. STATE RECORD HOLDER 2005,2006,2007,2008,2009 TEAM USAudio Stetsom Sales and Service stetsomrep1@hotmail.com Posts: 2226 | From: Maryland | Registered: Oct 2005
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posted
Nope, that's all the math you need to know if you're thinking of becoming a good box builder, and it's also the stuff that you realize is taking up all of the space in your brain that you could otherwise be using to learn how to count cards when you're in Las Vegas during CES in January.
posted
I knew there were geeks out there that would understand that, did anyone try to work out any of the formulas????????
-------------------- 12 VOLTS BABY!!!!! TEAM STETSOM USA & SALES REP TEAM STINGER BUY OHIO GENERATORS WORLD FINALS COMPETITOR 2005,2006,2008,2009 SUPER STREET 1-2 CERTIFIED 161.0 DB MARYLANDS LOUDEST DAILY DRIVER N.S.P.L. STATE RECORD HOLDER 2005,2006,2007,2008,2009 TEAM USAudio Stetsom Sales and Service stetsomrep1@hotmail.com Posts: 2226 | From: Maryland | Registered: Oct 2005
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posted
???? Then I carry the 2 and divide by what ?
-------------------- The bass killed kenny...... you bastard!! I post from my phone cause my computer hates me. I'm working on a 12th order sealed enclosure any ideas..... Posts: 105 | From: Charlotte, NC | Registered: Aug 2009
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-------------------- 12 VOLTS BABY!!!!! TEAM STETSOM USA & SALES REP TEAM STINGER BUY OHIO GENERATORS WORLD FINALS COMPETITOR 2005,2006,2008,2009 SUPER STREET 1-2 CERTIFIED 161.0 DB MARYLANDS LOUDEST DAILY DRIVER N.S.P.L. STATE RECORD HOLDER 2005,2006,2007,2008,2009 TEAM USAudio Stetsom Sales and Service stetsomrep1@hotmail.com Posts: 2226 | From: Maryland | Registered: Oct 2005
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posted
Hey need help installing f15d mono block by solid audio to bridge mode plus and minus from wich channels [LIST]
Posts: 2 | From: Cental Valley C.A | Registered: Sep 2009
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quote:Originally posted by Mabeita: Mono block in bridge mode???
What???
You're joking right?
possible if its a half bridge amp, but i dont think that is a half bridge amp.......
-------------------- 12 VOLTS BABY!!!!! TEAM STETSOM USA & SALES REP TEAM STINGER BUY OHIO GENERATORS WORLD FINALS COMPETITOR 2005,2006,2008,2009 SUPER STREET 1-2 CERTIFIED 161.0 DB MARYLANDS LOUDEST DAILY DRIVER N.S.P.L. STATE RECORD HOLDER 2005,2006,2007,2008,2009 TEAM USAudio Stetsom Sales and Service stetsomrep1@hotmail.com Posts: 2226 | From: Maryland | Registered: Oct 2005
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posted
To calculate the power response of a sealed enclosure system, you will need to know the following: Vas = equivalent air compliance (litres) Qes = electrical Q of driver at resonance Fs = resonance frequency of driver (Hz) PEmax = maximum input power for driver (W) Fb = resonance frequency of the system (Hz) Qtc = final Q of the system at resonance Dia = effective diameter (cone + 1/3 surround) (cm) Xmax = peak linear displacement of cone (mm)
pi = 3.14159265359 c = speed of sound in air (345 m/s) Ro = density of air (1.18 kg/m^3) n0 = free-air efficiency SPL = driver output @1W/1M Par = maximum linear power output Per = electrical input required to produce Par PeakSPL = Thermally-limited SPL in passband
SPLd = displacement-limited SPL at F (dB) Pmax = power required to produce SPLd at F (W) SPLt = thermally-limited SPL at F (dB)
This is already flawed c = speed of sound in air (345 m/s) , I know we never tune to sea level,and I dont know anyone who does. Ro = density of air (1.18 kg/m^3), Air density decreases with increasing altitude, as does air pressure. It also changes with variances in temperature or humidity. At sea level and 20 °C, air has a density of approximately 1.2 kg/m3. So with these 2 variables C and Ro this should only be used as a guide line only when using this long calculation.
posted
hahahahahaha I live at sea level well actually 25' above and 100' from, M&M congrats on your scores at finals and I didnt know you guys were spl "geeks" I always thought you guys were too cool for that!!!! But Murilo.....thats another story! hahaha
-------------------- 12 VOLTS BABY!!!!! TEAM STETSOM USA & SALES REP TEAM STINGER BUY OHIO GENERATORS WORLD FINALS COMPETITOR 2005,2006,2008,2009 SUPER STREET 1-2 CERTIFIED 161.0 DB MARYLANDS LOUDEST DAILY DRIVER N.S.P.L. STATE RECORD HOLDER 2005,2006,2007,2008,2009 TEAM USAudio Stetsom Sales and Service stetsomrep1@hotmail.com Posts: 2226 | From: Maryland | Registered: Oct 2005
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quote:Originally posted by kraven moorehead: hahahahahaha I live at sea level well actually 25' above and 100' from, M&M congrats on your scores at finals and I didnt know you guys were spl "geeks" I always thought you guys were too cool for that!!!! But Murilo.....thats another story! hahaha
Well, not geeks by all means. But We know this first hand, for example we live in an area that is around 3100feet above sea level. When going from 3100 feet to 600-700 feet above sea level, ( or Tulsa civic center 644 feet above sea level ) that is a big adjustment and you can`t really fine tune an extreme vechicle. But you can tweak the frequency without touching the box, and that is temperature to get to the closest frequency. Once you nail the temperature down,(because you have all ready tested that at home) the speed of sound will now work with you, and you can see it`s gain from a lower altitude. Of course the more sealed up a vechicle is the more effect temperature and speed of sound has.
posted
I saw that in my car at finals. Was anyone else having trouble finding frequency? It kept jumping around for me. Same settings week before in sweltering heat I did a 161.1 there it was a 160.4. I let the car run in the staging lanes and had the heater cranked the car was warm when i went to the lanes and it did a 160.8. I think a few more degrees in the temp and I might have won.
-------------------- 12 VOLTS BABY!!!!! TEAM STETSOM USA & SALES REP TEAM STINGER BUY OHIO GENERATORS WORLD FINALS COMPETITOR 2005,2006,2008,2009 SUPER STREET 1-2 CERTIFIED 161.0 DB MARYLANDS LOUDEST DAILY DRIVER N.S.P.L. STATE RECORD HOLDER 2005,2006,2007,2008,2009 TEAM USAudio Stetsom Sales and Service stetsomrep1@hotmail.com Posts: 2226 | From: Maryland | Registered: Oct 2005
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posted
So what effect dose barometric pressure have on all this with temp and hummidity?
-------------------- TEAM XTREME LOUD AUDIO THE LOUD CROWD Team Dc Sound Labs. Posts: 2789 | From: Springfield Ma | Registered: Apr 2004
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posted
Ok guys another ? the higher the pressure the lower the # or the other way around i have not tested this yet but been doing some thinking lately. do to testing in the crapy wether. then a few nice days back to the crapy wether i have seen a few cool things.
-------------------- TEAM XTREME LOUD AUDIO THE LOUD CROWD Team Dc Sound Labs. Posts: 2789 | From: Springfield Ma | Registered: Apr 2004
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