VI Moving Coil Driver Modeling & The Infinite Baffle Enclosure
	A.	Electromagnetic Drivers
		1.	Magnet: Resembles cross section of metal pipe.  
		2.	Frame: Supports outer rim of cone at one end, magnet assembly at 			other
		3.	Surround: Connects outer edge of cone to basket.  
		4.	Cone: Transfers acoustic power of the air into the load
		5.	Spider: Accordion looking cloth to keep voice coil assembly 			centered in the gap
		6.	Dust Cap: Protects voice coil assembly and gap from foreign 			debris
		7.	Top and Bottom plates: Create mantic gap that coil sits in.  
		8.	Gap: Between plates where magnetic lines of flux radiate from 			center outward through coil to edge.
		9.	Coil: Formed by wrapping turns of wire around cardboard voice 			coil form.  
		10.	Pole Piece: Connects to bottom and forms center plug
		11.	Pressure Equalization Hole: Gap is small and voice coil moves 			rapidly, so pressure is released. 
	B.	The Voice Coil
		1.	Voice coil can either be overhung or underhung.
		2.	Motor magnet strength given by BL product, L is length of wire, B is 			magnetic flux.
		3.	Only the length of wire immersed in the gap affects B.
		4.	Overhung wire goes outside the gap
	C.	Voice Coil Non-Linearities
		1.	Coil cannot exceed maximum distance because number of coils in 			the gap is no longer constant which introduces nonlinearities
		2.	If drivers suspension bottoms out this also causes harmonic 			distortion
		3.	Mechanical resonances on surface of the cone also cause 				harmonic distortion
		4.	Axial modes occur when one portion of the cone is moving forward 			and the other backwards 	(concentric circles)
		5.	Radial modes are like slices of a circle
		6.	This can be offset by strengthening concentric rings or radial 			bands.
		7.	Bands terminate at the rim and bounce backwards again, but 			proper termination can minimize 	reflections.
	D.	First mode of breakup
		1.	Operation will be linear until resonance on the cone surface occur.
		2.	First mode of resonance creates first resonant peak
		3.	Can be found by looking at impedance plot for bumps or notches
		4.	fbreakup = 0.523 t/a (E/p)^.5
			t = thickness of driver
			a = piston radius
			E = Young's Modulus of driver
			p = density of driver
		5.	These parameters can be determined based on material of driver
	E.	Functional Components
		1.	Electrical
			a.	Voice coil inductance Le
			b.	DC Resistance Re
			c.	Parasitic capacitances between wire turns (negligible)
			d.	Values can be found by checking Theile-Small parameters 				of drivers
		2.	Mechanical
			a.	Cone or diaphragm has most significant mass, Mmd
			b.	Suspension system (surround and spider) has spring 				component called Cms 
			c.	Suspension system has mechanical friction Rms
		3.	Acoustical
			a.	Depends on enclosure driver is mounted in as this 					determines load of front and back of cone.
			b.	Generalized with air loads Zab and Zaf for front and back.
	F.	The Infinite Baffle Enclosure
		1.	Wall or other large surface that isolates the front acoustic load from 			the rear acoustic load.
		2.	Air masses are large enough that compliance is infinite
		3.	Loudspeakers mounted in ceiling with no box or other enclosure 			on other side of driver
		4.	Volume compliance determines if the enclosure is big enough to 			be considered an infinite baffle.
		5.	This is the volume of air that has same compliance as drivers 			suspension system
		6.	Compliance ratio is ratio of Volume Compliance to Box Volume
		7.	Alpha less than 1 is considered an infinite baffle
	G.	Low Frequency Solution
		1.	At low frequencies, the volume velocity function is a band pass 			filter transfer function.
		2.	The peak volume velocity value occurs at natural resonant 				frequency of driver fs
		3.	Qts is total q of the system
		4.	Qts is combination of two other factors: Qms (Mechanical Q) and 			Qes (electrical Q)
		5.	Rms can be found using Qms, Cms, and Mms
	H.	High Frequency Solution
		1.	Dominated by electrical and mechanical portions of circuit model		2.	Produce 1st order Low Pass Filter
	I.	Combined Solution
		1.	For low frequencies: 2nd order high pass filter with cutoff 				frequency ws and resonant quality factor Qts 
		2.	1st order high pass for high frequencies
		3.	Resonant peak will occur if Qts is greater than .707
		4.	Low cutoff frequency is proportional to 1/Wts
		5.	Increased resonance sacrifices low cutoff edge.
	J.	On Axis Displacement Transfer Function: Displacement can be found 		using the relationship between volume velocity and displacement
	K.	On Axis Pressure Sensitivity
		1.	Pressure sensitivity is magnitude of mid band on axis pressure 			measured at 1 meter with 1 Vrms across voice coil.
		2.	This does not necessarily show efficiency of driver because 			current is necessary to calculate 
	L.	Acoustic Output Power
		1.	Volume velocity and radiation impednence needed
		2.	Similar to pressure response
	M.	Reference Efficiency
		1.	Ratio of acoustic power output to electrical power input.  
		2.	Usually close to 2%, meaning 98% power lost during transduction
	N.	Displacement Limited Electrical Input Power: Dependent on maximum 		excursion, Xmax.
	O.	Displacement Limited Power Rating
		1.	Maximum excursion limits output power
		2.	Power limit found by combining Pe(max) and efficiency equations
	P.	Voice Coil Impedance
		1.	Load is complex, not just a single resistor
		2.	Voice coil impedance Zvc found by looking into electrical terminals 			of driver
		3.	It is a parallel RLC network that must have a resonant frequency
		4.	There must be separate circuits based on frequency bands
		5.	There is a resonance from lows to mids and an inductive rise in 			the high frequencies
		6.	Resonance generates maximum impedance because of Back 			EMF
	Q.	Design
		1.	Only one degree of freedom: Type of driver.  Everything else can 			be predicted after that.
		2.	Driver specs will dictate everything.

VII. The Acoustic Suspension Enclosure
	A.	Intro
		1.	Also called closed box
		2.	Driver mounted in sealed box where no air can exact
		3.	Volume of box is only degree of freedom	
		4.	Back of the driver feels impedance of the compliance of the closed 			box
		5.	Box is filled with fibrous material which dampens standing waves 			in upper frequencies and increases compliance of air for lower 			frequencies
		6.	Filled box will appear larger than it is.
		7.	Filling is usually 20-50% of volume.
		8.	Apparent volume increase doesn't exceed 40%, usually 20-25%.
		9.	Acoustic suspension has compliance ratio of greater than 3.
	B.	Low Frequency Solution
		1.	RLC bandpass at low frequencies.
		2.	Total Volume Compliance Vat is volume of air with same 				compliance as system total compliance Cat (=Cas/(1+alpha))
		3.	LF is a bandpass with nearly identical volume velocity equations
	C.	High Frequency Solution
		1.	Dominated by electrical and mechanical portions
		2.	Identical to infinite baffle
		3.	1st order low pass filter 
	D.	On Axis Pressure Transfer Function
		1.	2nd order HPF band edge on low end
		2.	Same as Infinite Baffle except Qtc can be controlled using box 			volume
		3.	Qtc can only be controlled in upwards direction, resonance can 			only be increased
		4.	Large Box: Cat increases, fc decreases, Qtc decreases
		5.	Small Box: Cat decreases, fc increases, Qtc increases
	E.	Impedance Response
		1.	Almost same as Infinite Baffle
		2.	Difference is peak impedance occurs at resonant frequency of 			closed box system.
		3.	Impedance response can be tested electronically, you can change 			volume of box until impedance plot is correct.
	F.	Alignments and Transient Response
		1.	Alignments are choice over final Qts
		2.	0.2-0.5: over damped, best transient response, poorest bass
		3.	0.500: critically damped: good transient response, poorer bass
		4.	0.577: Bessel: maximally flat delay response, poor bass
		5.	0.707: Butterworth: lowest f-3, maximally flat response
		6.	>0.707: Chebychev: resonant peaking, transient response rings
	G.	On Axis Pressure Sensitivity: Only the subsets change for new overall 		system
	H.	Reference Efficiency
		1.	Same as infinite baffle except subscripts changed for system
		2.	Adding fill increases Vab which decreases k, arguably making the 			system more efficient.
	I.	Displacement Limited Electrical Input Power: Same as infinite baffle 		except changes to subsets for new system.
	J.	Displacement Limited Power Rating
		1.	Only change is subsets for different system
		2.	Enclosure designs are for bass response only, meaning just for 			woofers.
		3.	Tweeter and midrange excursions have such small excursions 			that any enclosure will appear as an infinite baffle.
		4.	Some of these have their own enclosures, but this is usually to 			protect them from vibrations of woofer.
	K.	Acoustic Suspension Design Guide
		1.	Box volume controls the overall Qtc of the system
		2.	FIlling of box also possible
		3.	Either start with driver and choose Qtc or desired Fc, or try to 			specify botth Qtc and f-3 and find the correct driver.
		4.	Methods of predicting frequency response:
			a.	Vance Dickason
				1)	Decide on Qtc of system and select driver with Qts 					lower than desired response (Q can only be 						increased.)
				2)	Calculate compliance ratio and then box volume and 					predicted resonant frequency.  
			b.	Richard Small
				1)	Decide on final Qtc and select driver with Qts lower 					than desired response
				2)	Guesstimate mechanical quality factor Qms using 					rules of thumb: 5<QMc<10 unfilled 2<Qmc<5 filled
				3)	Calculate Qec
		5.	Enclosure Dimensions
			a.	Golden ratio: 0.6x1.0x1.6
			b.	Squarish: 0.8x1.0x1.25
			c.	Dimensions alter modes of standing waves
			d.	Perfectly cube or spherical enclosures are avoided
		6.	Testing
			a.	Measure input impedance of speaker
			b.	Done with AC input source (oscillator), low power amplifier, 				power resistor	
			c.	Resistor must be in expected range, ie 32 ohms
			d.	Apply oscillator to circuit and measure AC input Vin as well 				as Vx at different frequencies, then calculate input 					impedance.
			e.	fc is impedance maximum, adjust until fc tuned properly
VIII: The Bass-Reflex Enclosure
	A.	Intro 
		1.	Adds tube, and vent to Closed box
		2.	Also called Bass Reflex, Ported, Vented, Thiele-Small
		3.	Thin layer of acoustic filling to prevent standing waves
		4.	Tube/enclosure is a helmholtz resonator at very low frequencies to 			extend low frequency response
		5.	Mass of tube becomes another variable
		6.	Pros: Lower f-3 frequency.  Better Efficiency.  Helholtz Resonator 			extends response.
		7.	Cons: Enclosure larger than closed box, f-3 same or higher, 			resonator causes unwanted audible effects
	B.	Modeling Bass Reflex Enclosure
		8.	Consists of driver, port, chamber.
		9.	Volume velocity consists of: Driver Volume Velocity, Port Volume 			Velocity, Box Volume Velocity, Lossy-Leak Volume Velocity, 			Lossy-Absorption Volume Velocity
		10.	Losses determined by quality of carpentry
		11.	Each volume velocity has an associated Q
	C.	The LF Combination Analogous Circuit: There are four reactive 			components
	D.	Bass Reflex Operation
		1.	Response broken down into lower than fb(resonant frequency), 			at fb, and above fb.
		2.	Below fb
			a.	Below fb there is unloading, where driver moves back and 				air is blown out port, driver moves forward and air is sucked 				through the port.  
			b.	This means there is no real acoustic load from enclosure
		3.	Above fb
			a.	Drivers excursion is small and box acts as infinite baffle
			b.	Resonator has no output
		4.	At fb
			a.	HH resonator energized from back side.
			b.	Amount of delay time it takes for acoustic wave to reach 				opening of port on front is enough to exactly invert phase 				360 degrees, so output output of HH is in phase with front of 				cone
			c.	 Driver tries to move but air is flowing in or out of the port.
			d.	100% of output comes from the port
			e.	This places stress on driver suspension 
	E.	Driver Excursion & Resonator Output
		1.	Driver excursion reaches minimum at HH frequency
		2.	This is due to unloading
		3.	If combined resonances of driver and resonator are off, this can be 			disastrous. 
	F.	Problems with the Vent
		1.	Mechanical stress on driver due to unloading
		2.	No back EMF when driver excursion is 0, impedance is just Re, 			causing excess current flow at resonant frequency
		3.	More power dissipated as heat
		4.	Chuffing/Windage
			a.	Vent must be 3 inches from wall of enclosure
			b.	If its not there is audible chuffing or windage
			c.	Port can be extended past enclosure, or can be curved to 				avoid this
		5.	Organ Pipe Resonances
			a.	If tube length is too long, standing waves can create 					harmonics in the tube.
			b.	Causes peaks or notches in response
			c.	Can couple with resonances of driver
	G.	On-Axis Pressure Transfer Function
		1.	Total volume velocity is sum of three volume velocities discussed 			before.
		2.	There is a resonant frequency of port/box and of driver
		3.	Q for this speaker is inverted
		4.	Response is a 4th order HPF
		5.	We try to find dimensions of box and tube to create coefficients 			needed for given filter response
	H.	Alignments
		1.	Chebychev alignments generate various amounts of ripple in 			passband and resonant hump at edge of stop band.		
		2.	Alignments for Bass reflex dependent on Qts
		3.	Higher Ql, less lossy the enclosure
		4.	Typical Ql starts at 7
	I.	B4 Alignment
		1.	Most sought after due to tradeoff of good transient and low end 			response.
		2.	q=1 for all values Ql, f-3 will always be driver's resonant frequency
		3.	Butterworth response maximumly flat though passband
	J.	QB3 Alignment
		1.	Quasi-3rd Order Butterworth
		2.	Slopes roll off less steeply
		3.	Lower Qts than B4
		4.	Similar transient response to B4
		5.	Tradeoff in bass just below cutoff
	K.	C4 Alignment Family
		1.	Chebychev characterized by ripple in passband.
		2.	To calculate data, first specify the riffle in dB then calculate other 			variables.
		3.	Requires higher Qts than B4
		4.	Transient response not as good as B4
	L.	Alighnment Comparisons: Ringing occurs in all but SC4 transient 			response
	M.	Voice Coil Impedance
		1.	Effects of unloading on impedance at low frequencies
		2.	Null at the HH resonant frequency
		3.	Produces doubly resonant circuit
		4.	Impedance measurement used to check port tuning
		5.	For B4 alignments peaks have same height
	N.	Enclosure Design with Nomographs
		1.	Drivers Qts dictates alignment in Bass Reflex
		2.	Final solution is Volume Vab and box frequency fB
		3.	Program must be written to deal with all the variables.
		4.	Nomograph has solutions to all equations in form of axes and 			curves.  
		5.	Separate graph needed for each Ql

IX.	Passive Radiator, Bandpass and Transmission Line Enclosures
	A.	 Passive Radiator Enclosures
		1.	Take a vented enclosure, replace air mass in port with mechanical 			mass of passive radiator.  
		2.	Passive radiator looks like driver without magnet motor assembly.
		3.	Specified like drivers but without Bl product, power ratings, or 			efficiency calculations.
		4.	Unwanted effects of the port including windage, chuffing, organ 			pipe resonances, and impossible port lengths are eliminated.
		5.	Because of suspension there is compliance and resistance.
		6.	Electrical model is identical except for added compliance and 			resistance.  
		7.	There is a second compliance ratio, along with tuning ratio
		8.	When compliance is infinite, response is same as vented box
		9.	Numerator's zeros of filter not at s=0 like vented enclosure so there 			is a notch in response.  
		10.	Goal is for notch to be far away from corner frequency as possible.
		11.	Hard to specify alignments cause the filter is an Elliptic Filter
		12.	Cutoff for Chebychev 4 is steeper than vented box.
		13.	Rippling in pass band determined by PR tuning ratio.  
	B.	Passive Radiator Design with Nomographs
		1.	There are six variables to solve for.
		2.	Along with dimensions and tuning, volume displacement of of 			passive radiator must be specified.
		3.	This means two nomographs must be used.
	C.	Other Passive Radiator Specifications: Same as Bass Reflex
		1.	Impedance Plot
		2.	PAR(max)
		3.	PE(max)
		4.	n0