TL vs driver parameters

[Henkjan]

([sorry for the cross post, but it appears the TL specialists reside in this sub forum....)

So I built this nice sub with the Tangband W69-1042 see TL sub with 2 TB69 woofs just a straight TL with A=Sd.

Since a co-worker would like a new sub, and he thought the sub with the W69 was rather large, I thought of a similar TL employing the W6-1108SA. both fs and Qt are close to those of the W69 so it was my expectation that I could simply scale the design for the smaller Sd. NOT! The simulation of the TL with MLK's 'driver offset' sheet showed a different respons, much less low. where the W69 had a rather flat curve from 100 down to 40Hz (see pic below) the W6 rolled off much earlier (sorry, forgot to make a snapshot, will post this later) with -5bB @40Hz. I tried to tweak the design, longer pipe, taper but the basic form of the curve remained the same

so there's more than just fs and Qt ....

here the sim of the W69 sub

[Scottmoose]

Not surprising. The cone Sd actually has almost nothing to do with the way a TL works you see, it's just frequently used as a convenient measurement. What's more important is line length, driver Vs, and cabinet Vb (volume).

I see from the link it's a non-tapered line, correct? For a tuning frequency with a straight line of 40Hz for example, it needs to be 84in long (tapered lines will be either longer or shorter, depending on whether it's a positive or negative taper). I'd suggest that you start altering the volume of the box. Don't increase the line length; increase / decrease the CSA of the box, and you mght be surprised. I don't have time to run a full sim on them myself, but the drivers are perfectly suitable for QW / TL loading.

Best
Scott

[Henkjan]

yes, the W69 sub has an untapered line

on your remark, I calc'ed the Vad/Sd and for the W69 it's lower than for the W6, so my 1st try will be a larger cross section so that Vb/Vad is equal for both designs

what kind of effect does BL have?

[Scottmoose]

Depends on circumstances -the design, the driver's other parameters, the enclosure and a host of other factors. In this case, not much. I wouldn't worry about it anyway -the drivers are perfectly suitable for a TL / QWR.

[Henkjan]

so, here a couple of sims. first the 1st try, this was a 2m straight line with A=Sd

[Henkjan]

this is the tapered, 2.4m long A=1.7Sd - 0.7Sd line

[Henkjan]

and here the fat long straight, 2.4m A=1.25Sd

[Henkjan]

and this is the somewhat narrower tapered line, 2.4m A=1.4Sd - 0.6Sd