Calculate box size using bass reflex alignments



Image
  1. Find out the Qts of your driver, by measuring it, or look for it in the data sheet.
  2. >>> If Qts is lower than 0.4, you will end up with a flat alignment.
    >>> If it’s higher than 0.4, the alignment will be non-flat.


  3. Find out fs and Vas of your speaker, by either measuring it or by looking it up in the data sheet.
  4. Choose a diameter for the port.
  5. Choose the alignment you would like, and go to the appropriate table.
  6. Use the radio button left of the Qts value to get all parameters and the results will be calculated.

  7. If you change the Thiele/Small parameters or the Port diameter , click the 'Recalculate' button

       QB3             SBB4             SC4       



Thiele/Small Parameters Alignments from table
Fs : Hz H :
Vas : liters a :
Port diameter : cm f3/fb :



Frequency Response


The frequency plot gives an impression of the radiated frequency range of the speaker.






QB3

QB3 or Third-Order Quasi-Butterworth – is the most popular vented alignment, because it yields a smaller box and a lower f3. However, the transient response is not as good as SBB4 or SC4.

QL 3

QL 7

QL 15

Qts H a F3/Fs Peak  Qts H a F3/Fs Peak  Qts H a F3/Fs Peak
 0,1004,330331,29045,67090  0,1003,841634,39255,22330  0,1003,684135,47935,07150
 0,1103,937125,68245,14560  0,1103,494728,23414,73860  0,1103,349429,12864,60040
 0,1203,609621,41694,70690  0,1203,205823,54994,33370  0,1203,073224,29844,20690
 0,1303,332518,09744,33480  0,1302,961519,90463,99020  0,1302,839820,53923,87300
 0,1403,095015,46354,01500  0,1402,961517,01503,69490  0,1402,640017,55633,58590
 0,1502,889213,33863,73710  0,1502,571214,67843,43810  0,1502,457015,14983,33620
 0,1602,072911.59943,49320  0,1602,412912,76853,21260  0,1602,315813,18023,11690
 0,1702,550410,15813,27720  0,1702,274311,18553,01280  0,1702,182611,54782,92250
 0,1802,40928,95023,08440  0,1802,14959,85892,83450  0,1802,064410,17972,74880
 0,1902,28307,92802,91130  0,1902,03888,73612,67410  0,1901,95899,02182,59260
 0,2002,16947,05522,75480  0,2001,93937,77752,52890  0,2001,86408,03312,45120
 0,2102,06666,30412,61250  0,2101,84946,95242,39680  0,2101,77847,18222,32250
 0,2201,97335,65312,48240  0,2201,76786,23722,27590  0,2201,70076,44462,20450
 0,2301,88815,08512,36300  0,2301,69355,61322,16470  0,2301,62995,80102,09600
 0,2401,81004,58662,25280  0,2401,62545,06552,06200  0,2401,56525,23611,99560
 0,2501,73814,14672,15080  0,2501,56294,58221.96670  0,2501,50584,73751,90230
 0,2601,67193,75662,05590  0,2601,50544,15351.87780  0,2601,45124,29521.81530
 0,2701,61053,40901.96740  0,2701,45223,77141.79460  0,2701,40073,90111.73380
 0,2801,55363,09801.88450  0,2801,40293,42951.71650  0,2801,35403,54841.64710
 0,2901,50062,81861.80650  0,2901,35713,12231.64290  0,2901,31063,23141.58460
 0,3001,45122,56661.73310  0,3001,31452,84211.57320  0,3001,27032,94551.51590
 0,3101,40502,33861.66360  0,3101,27482,59441.50700  0,3101,23272,68671.45040
 0,3201,36172,13171.59780  0,3201,23762,36671.44390  0,3201,19762,45171.38800
 0,3301,32101.94321.53510  0,3301,20282,15941.38360  0,3301,16482,23761.32810
 0,3401,28281.77121.47540  0,3401,17021,96991.32580  0,3401,13412,04201.27050
 0,3501,24671.61361.41830  0,3501,13951,79641.27020  0,3501,10521,86291.12510
 0,3601,21271.46901.36360  0,3601,11061,63711.21670  0,3601,07811,69831.16150
 0,3701,18061.33601.31100  0,3701,08341,49051.16510  0,3701,05261,54681.10990
 0,3801,15011.21331.26050  0,3801,05781,35521.11530  0,3801,02861,40701.06020
 0,3901,12131.09991.21180  0,3901,03351,23001.06740  0,3901,00591,27771.01250
 0,4001,09390,99491.16490  0,4001,01061,11411,02140  0,4000,98451,15790,96720
 0,4101,06790,89741.11980  0,4100,98891,00650,97760  0,4100,96431,04660,92450,02
 0,4201,04310,80691.07630  0,4200,96830,90640,93620,01  0,4200,94520,94300,88490,08
 0,4301,01950,77251.03460  0,4300,94880,81310,89750,05  0,4300,92720,84640,84880,21
 0,4400,99700,64390,99470  0,4400,93030,72600,86180,14  0,4400,91010,75620,81620,43
 0,4500,97550,57040,95680  0,4500,91280,64450,82940,31  0,4500,89390,67190,78720,76
 0,4600,95500,50160,92100,02  0,4600,89610,56820,80010,56  0,4600,87860,59280,76181,18
 0,4700,93540,46720,88750,06  0,4700,88020,49660,77410,9  0,4700,86410,51850,73951,72
 0,4800,91660,37670,85630,14  0,4800,86510,42940,75101,32  0,4800,85030,44880,72022,36
 0,4900,89860,31990,82760,27  0,4900,85070,36610,73071,85  0,4900,83730,38300,70343,13
 0,5000,88130,26650,80140,45  0,5000,83700,30650,71292,46  0,5000,82490,32110,68894,04
 0,5100,86470,21610,77750,7  0,5100,82400,25030,69723,18  0,5100,81320,26250,67645,09
 0,5200,84880,16860,75581,00  0,5200,81160,19710,68354,01  0,5200,82100,20720,66566,33
 0,5300,83360,12380,73631,36  0,5300,79980,14680,67154,97  0,5300,79160,15470,65637,79
 0,5400,81890,08140,71861,77  0,5400,78860,09920,66106,08  0,5400,78170,10500,64839,56
 0,5500,80470,04130,70272,25  0,5500,77790,05400,65187,36  0,5500,77230,05770,641611,8
 0,5600,79110,00330,68832,78  0,5600,76770,01110,64388,87  0,5600,76350,01280,635914,7


SBB4

SBB4 or Super Fourth-Order Boom Box – is characterized by a large box, low tuning frequency (longer vent) and good transient response (which puts the term boom-box out of place).

QL 3

QL 7

QL 15

Qts H a F3/Fs Peak  Qts H a F3/Fs Peak  Qts H a F3/Fs Peak
 0,2001,00005,44443,54010  0,2001,00005,89803,36860  0,2001,00006,08443,29960
 0,2101,00004,90313,32550  0,2101,00005,33393,15180  0,2101,00005,51133,08180
 0,2201,00004,43553,12800  0,2201,00004,84572,95210  0,2201,00005,01492,88110
 0,2301,00004,02902,94540  0,2301,00004,42042,76740  0,2301,00004,58212,69550
 0,2401,00003,67362,77610  0,2401,00004,04782,59600  0,2401,00004,20252,52330
 0,2501,00003,36112,61860  0,2501,00003,71142,43660  0,2501,00003,86782,36330
 0,2601,00003,08502,47180  0,2601,00003,42862,28830  0,2601,00003,57112,21460
 0,2701,00002,83992,33470  0,2701,00003,16992,15030  0,2701,00003,30702,07640
 0,2801,00002,62132,20680  0,2801,00003,16992,15030  0,2801,00003,07081,94830
 0,2901,00002,42572,08730  0,2901,00002,73151,90310  0,2901,00002,85881,83010
 0,3001,00002,25001,97590  0,3001,00002,73151,79320  0,3001,00002,54481,79320
 0,3101,00002,09161,87240  0,3101,00002,37611,69220  0,3101,00002,46501,62220
 0,3201,00001,94841,68760  0,3201,00002,22331,60000  0,3201,00002,33841,53230
 0,3301,00001,81141,68760  0,3301,00002,08431,51620  0,3301,00002,19581,45140
 0,3401,00001,70021,60600  0,3401,00001,95761,44060  0,3401,00002,03571,37900
 0,3501,00001,59241,53130  0,3501,00001,84191,37280  0,3501,00001,94671,31460
 0,3601,00001,49381,46320  0,3601,00001,73571,25760  0,3601,00001,83751,31460
 0,3701,00001,40351,40140  0,3701,00001,63921,25830  0,3701,00001,73721,20710,01
 0,3801,00001,32051,34560  0,3801,00001,54841,21040  0,3801,00001,64471,16260,01
 0,3901,00001,24411,29520  0,3901,00001,46561,16790,06  0,3901,00001,55931,12330,16
 0,4001,00001,17361,24990  0,4001,00001,38901,13020,14  0,4001,00001,48031,08860,27
 0,4101,00001,10851,20910,01  0,4101,00001,31811,09660,24  0,4101,00001,40701,05770,41
 0,4201,00001,04821,17240,05  0,4201,00001,25231,06670,37  0,4201,00001,33901,03030,57
 0,4301,00001,99231,13940,12  0,4301,00001,19111,03990,37  0,4301,00001,27571,00590,73
 0,4401,00000,94031,10960,20  0,4401,00001,13411,01600,66  0,4401,00001,21670,98400,91
 0,4501,00000,89201,08280,30  0,4501,00001,08090,99440,82  0,4501,00001,16160,96431,10
 0,4601,00000,84690,05850,41  0,4601,00001,03130,97501,00  0,4601,00001,11010,94661,30
 0,4701,00000,80491,03650,53  0,4701,00000,98490,95741,17  0,4701,00001,06190,93051,50
 0,4801,00000,76561,01650,66  0,4801,00000,94140,94151,36  0,4801,00001,01670,91601,71
 0,4901,00000,72890,99830,79  0,4901,00000,90060,92701,55  0,4901,00000,97430,90271,91
 0,5001,00000,69440,98150,93  0,5001,00000,86220,91371,74  0,5001,00000,93440,89062,13
 0,5101,00000,66210,96631.08  0,5101,00000,82620,90151,93  0,5101,00000,89690,87952,34
 0,5201,00000,63180,95231.23  0,5201,00000,79230,89042,13  0,5201,00000,86160,86962,56
 0,5301,00000,60330,93941.38  0,5301,00000,76030,88012,33  0,5301,00000,82820,85992,78
 0,5401,00000,57650,92751.54  0,5401,00000,73020,87062,53  0,5401,00000,79670,85132,99
 0,5501,00000,55120,91651.70  0,5501,00000,70170,86192,73  0,5501,00000,76700,84323,21
 0,5601,00000,52740,90631.86  0,5601,00000,67470,85372,93  0,5601,00000,73880,83583,43
 0,5701,00000,50480,89682,02  0,5701,00000,64930,84623,13  0,5701,00000,71210,82893,65
 0,5801,00000,48360,88802,18  0,5801,00000,62510,83913,33  0,5801,00000,68680,82243,86
 0,5901,00000,46350,87972,34  0,5901,00000,60220,83253,53  0,5901,00000,66280,81644,08
 0,6001,00000,44440,87202,50  0,6001,00000,58050,82643,73  0,6001,00000,64000,81084,29
 0,6101,00000,42640,86942,66  0,6101,00000,55990,82063,93  0,6101,00000,61830,80554,51
 0,6201,00000,40930,85812,82  0,6201,00000,54030,81524,12  0,6201,00000,59770,80064,72
 0,6301,00000,39310,85182,98  0,6301,00000,52160,81024,23  0,6301,00000,57810,79594,93
 0,6401,00000,37770,84583,14  0,6401,00000,50380,82544,51  0,6401,00000,55940,79165,14
 0,6501,00000,36310,84023,3  0,6501,00000,48690,80094,70  0,6501,00000,54150,78745,35
 0,6601,00000,34920,834463,46  0,6601,00000,47080,79674,90  0,6601,00000,52450,78365,55
 0,6701,00000,33590,82993,61  0,6701,00000,45540,79265,09  0,6701,00000,50830,77995,76
 0,6801,00000,32330,82523,77  0,6801,00000,44070,78895,27  0,6801,00000,49270,77645,96
 0,6901,00000,31130,82073,92  0,6901,00000,42670,78465,46  0,6901,00000,47790,77316,16
 0,7001,00000,29990,81654,08  0,7001,00000,41330,78195,65  0,7001,00000,46370,77006,36


SC4

SC4 or Forth-Order Sub-Chebyshev – about the same enclosure size and f3 as the SBB4, but with different tuning frequency.
Somewhat degraded transients compared to SBB4.

QL 3

QL 7

QL 15

Qts H a F3/Fs Peak  Qts H a F3/Fs Peak  Qts H a F3/Fs Peak
 0,2501,00933,40802,60830  0,2501,03383,89612,22820  0,2501,04204,08902,30970
 0,2601,03223,23012,43910  0,2601,05343,67552,39490  0,2601,06013,85002,14770
 0,2701,05293,05162,28600  0,2701,07033,45512,07840  0,2701,07513,61191,99700
 0,2801,07032,87312,14730  0,2801,08423,23601,94390  0,2801,08713,37571,86470
 0,2901,07812,69522,02170  0,2901,09513,01931,82290  0,2801,09583,14291,74600
 0,3001,10042,51881,90780  0,3001,10282,80621,71370  0,3001,10112,91471,63910
 0,3101,11092,34471,80420  0,3101,10732,59771,61490  0,3101,10312,69241,54260
 0,3201,11872,17381,70970  0,3201,10862,39521,52510  0,3201,10162,47741,45490
 0,3301,12362,00691,62320  0,3301,10652,19971,44310  0,3301,09662,27111,37490
 0,3401,12551,84481,54370  0,3401,10122,01251,36790  0,3401,08842,07481,30160
 0,3501,12441,68851,47030  0,3501,09261,83471,29860  0,3501,88961,23421,23420
 0,3601,12031,53871,40230  0,3601,08101,66721,23450  0,3601,06261,71661,17200
 0,3701,11331,39611,33900  0,3701,06671,51091,17510  0,3701,04561,55671,11460
 0,3801,10341,26161,27980  0,3801,04981,36651,12000  0,3801,02651,41011,06150
 0,3901,09091,13561,22440  0,3901,03091,23431,06890  0,3901,00581,27791,01250
 0,4001,07581,01871,17230  0,4001,01031,11461,02150  0,4001,98401,15911,96750
 0,4101,05860,91101,12360  0,4100,98861,00700,97770  0,4100,96151,05350,92620
 0,4201,03940,81281,07780  0,4200,96620,91130,93730  0,4200,93900,96040,88840
 0,4301,01880,72381,03480  0,4300,94360,82660,90010  0,4300,91670,87870,85390
 0,4400,97700,64390,99470  0,4400,92120,75210,86600  0,4400,89510,80740,82260,01
 0,4500,97440,57260,95720  0,4500,89920,68580,83480.01  0,4500,87440,74530,79420.02
 0,4600,95150,50930,92220  0,4600,87800,62970,80640.01  0,4600,85470,76840,76840.03
 0,4700,92860,56330,88980  0,4700,85780,57980,78040.02  0,4700,85470,69110,76840.05
 0,4800,90590,40400,85970  0,4800,83850,53610,75670.03  0,4800,81870,60270,72390.07
 0,4900,88370,36050,83180  0,4900,82030,49780,73510.05  0,4900,80250,56660,70470.09
 0,5000,86210,32230,80600,01  0,5000,80310,46420,71550.07  0,5000,78730,53480,68730.12
 0,5100,84120,28850,78220,02  0,5100,78700,43450,69750.09  0,5100,77320,50680,67140.16
 0,5200,82120,25860,76010,02  0,5200,77190,40830,68100.12  0,5200,76010,48200,65690.20
 0,5300,80210,23210,73970,03  0,5300,75780,38490,66590.15  0,5300,74790,45990,64370.24
 0,5400,78380,20840,72080,05  0,5400,74450,36400,62000.19  0,5400,73660,44020,63150.29
 0,5500,76640,18720,70330,06  0,5500,73210,34530,62000.23  0,5500,72600,42250,62040.34
 0,5600,74990,16180,68710,08  0,5600,72050,32840,62750.27  0,5600,71620,40650,61010.39
 0,5700,73410,15080,67200,10  0,5700,70960,31310,61660.31  0,5700,70700,39210,60060.45
 0,5800,71920,13500,65790,12  0,5800,69930,29920,60650.31  0,5800,69840,37890,59190.51
 0,5900,70490,12050,64470,14  0,5900,68960,28650,59710.41  0,5900,69030,36700,59380.57
 0,6000,69130,10720,63240,17  0,6000,68050,27490,58830.46  0,6000,68280,35600,57620.63
 0,6100,67840,09840,62090,20  0,6100,67190,26410,58020.51  0,6100,67570,34590,56920.70
 0,6200,66610,08320,61010,23  0,6200,66380,25420,57260.57  0,6200,66900,33660,56260.77
 0,6300,65430,07230,61010,26  0,6300,65610,24490,56540.63  0,6300,66270,32810,55650.83
 0,6400,64300,63000,59060,29  0,6400,64880,23630,55870,68  0,6400,65670,32010,55080,90
 0,6500,64300,63000,59060,29  0,6500,64880,23630,55870,68  0,6500,66270,32810,55650,90
 0,6600,62180,04350,57260,32  0,6600,63530,22080,54650,80  0,6600,64580,30580,54031,00
 0,6700,61180,03430,56440,39  0,6700,62890,21360,54090,89  0,6700,64080,29940,53551,12
 0,6800,60220,02580,55670,42  0,6800,62290,29330,53550.92  0,6800,63600,29940,53111,19
 0,6900,59290,17500,54930,46  0,6900,61710,20060,53050,98  0,6900,63140,28760,52681,26
 0,7000,58400,00960,54230,50  0,7000,61160,19460,52581,05  0,7000,62710,28230,52281,33


Conventional and Assisted Alignments of Arbitrary Order and Box Quality Factor ( Ext. link )




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