According R.H. Small is there a connection between efficiency eta [%], lower limit frequency F3 [Hz] and box volume Vb [l]:
Eta [%] = Kn · 10-5 · F33 [Hz] · Vb [l]
The factor Kn is made up of three components:
Kn = Kn(Q) · Kn(C) · Kn(G),
where Kn is the component (C) takes into account only in sealed enclosures. It is:
Kn(Q) = Qt / Qe ( For chassis with low mechanical losses (Qm>> Qe) reached Kn (Q) its theoretical maximum of 1 )
Kn(C) = Vas / ( Vas + Vb ) ( In soft clamped chassis that are built into a small housing (vas>> Vb) reached Kn (C) its theoretical maximum of 1 )
The value of Kn (G) depends on the overall quality of sealed enclosures Qtc of the system and bass reflex enclosures depends on the total losses and the total Q Ql Qts of the chassis in open air.
The whole thing is of course (like all other TSP) only in the area of piston-diaphragm movement, that is usually only in the lower frequency range.
|| = Desired lower cutoff frequency (-3 dB) of the system|
|| = Overall quality of the chassis|
|| = Overall quality of housing losses|
|| = Overall quality of the finished speaker|
|| = Maximum available cabinet volume |