Fuzzy TL from HobbyHifi

[Henkjan]

has anyone seen this? according to the designer it is a new type of TL that should have the advantages of the TL in the low range, but not the dips in the frequency in the lower mids.... his explanation is also rather fuzzy, he bases his conclusion on comparing his AJHorn simulation with his measurements. apart from a dip ~200Hz (at that resonance there is also a rimple in the imp curve, both measured and sim-ed) the measured curve is rather flat, and the AJHorn sim as expected is not.

I trust the sim engine of AJorn, but I know that it's input (as in how well can one describe the line and stuffing) is no where near as acurate as can be achieved with MJK's mathcad sheets. it would not surprise me that once I run it through a proper sim, that sim and measurement are in much better allignment...

[Henkjan]

and here the AJHorn sim result (red curve is simmed as BR, to show that the design is a true TL and not a BR)

[GM]

What makes it 'new'? Looks like a MLTL to me........

GM

[Scottmoose]

Agreed, & a somewhat under-damped one at that. Or even (if we can stretch the definition slightly), an Olney labyrinth or daline. Certainly nothing new here. Looks like it's making life harder than it has to be too. You'd probably be able to get the same or better performance out of a simple straight mass-loaded pipe.

[flaevor]

sure, but the way he says it, sells magazines.

[Scottmoose]

...which is why I rarely bother reading magazines.

[GM]

OK, didn't realize this was from a magazine article plus wasn't sure if I was missing something.

GM

[Scottmoose]

Doesn't look like it.

FWLIW, I've just stuffed it through MathCAD, assuming an FE207E (factory spec) & WAGing a 26cm width as we don't have much in the way of dimensions, or the driver used. Doesn't look too bad, but nothing that a simple straight line couldn't do.

[flaevor]

It is funny through you guys and the short fat thor thread I learned that port placement can turn a bass reflex into an MLTL. Now I always wonder when people build a Bass reflex box if they realized this when they're placing their ports for optical reasons.

[Scottmoose]

Sort of. The basic difference between a BR & an MLTL is that a BR assumes no standing waves in the cabinet. An MLTL deliberately generates & uses standing waves (the cabinet vertical mode).

It's true enough though -when the fashion for tall, slim floorstanders first raised its head, not a few people (and some companies, truth be known) were left scratching their heads because the LF output was not what they'd expected, i.e. they'd inadvertantly created an incorrectly tuned MLTL rather than a BR, so they needed to go back & re-tune the thing to account for this.