Hi Didier,

I'm somewhat surprised that you seem to feel obliged to use a 120 L. box so that you don't regret later, whereas I've given you in post # 12 a few smaller box options that would be better for your living room space as you say (e.g. Win ISD Pro (2016) QL 7: 85 L. (3 cu. ft.), tuned at 40 hz, also pretty flat response except for a small .75 db drop around 85 hz, F3 @ 40 hz). Rob has added the suggestion of low frequency DSP to increase the bass.

My word of caution on that was "... isn't a good idea in my view even if you compensate with DSP (i.e. equalization) because it requires more power which leads to more distortion caused by increased cone travel..." In a home hi-fi setup, as Rob mentions, where one doesn't usually try to rattle the planet, if you have sufficient power available to provide + 6 db LF boost (= 4 times the power) and the driver is capable of reasonably high excursion (1400 ND: Xmax 7.62 mm, good) then why not go for it ? I would, with or without EQ.

I mentioned in post # 20 "A steep high-pass filter is usually required as E-V doest it with their "step-down mode EQ" and there are other conditions like, if my memory is correct, tuning half an octave below "normal", not just any frequency below... You should read more on this issue." My point here was that you don't pick an Fb at 30 hz because Rob did so. It all depends on each specific case. The above-mentioned box of 85 L. with a proposed tuning at 40 hz would lead to a 30 hz tuning if designed for "Step-Down Operation". Another box another tuning...

I've pulled-out my tech stuff on E-V's Step-down mode EQ. The above mention about high-pass filter and tuning half octave below are in fact correct. B6 alignments are attributed to Thiele by both E-V and Keele, however refined by Keele while he worked at Electro-Voice.

E-V's "step-down mode" is an approximate B6 alignment, but a tried and proven concept. To my knowledge, no other major Manufacturer has used these as extensively as E-V. I would then be tempted to suggest you follow the way E-V does it since its a known recipe.

No time now, but I'll be back tomorrow to quote some juicy and easy to understand paragraphs from E-V's description/explanation of "step-down mode" operation.

BTW I'm not really in favor of building test boxes and never have made any to test woofers since its double the work and my experience at building many tells me the computer model is sufficiently precise (except vent length), if well made, to avoid them. Too many people try a quickly made box of shady construction, barely braced with questionable air tightness and then assume results will be the real thing. Not so, you must compare comparable stuff. If you make a test box it has to be identical (except finish) to the proposed final one so that you get real results of what the final product will be. Double the work for little or nothing in my view. Unless you make only one, well made, test and decide if you keep, if yes then you have only one left to do...

Richard