Effect of low QTS in bass horns?? Vas for dual loaded cabs??

[Boyd]

I'm pretty sure Bill has mentioned before than drivers with high QTS will have reduced low bass when horn loaded, but what is the effect of low QTS (~0.2) in a FLH?

While the effects of QTS in sealed & ported boxes seem to be pretty well explained across the interweb, I've found little specifics on the effect of low QTS in a bass horn, beyond a broad generalization that 'low QTS drivers are suitable for horn enclosures'.

Part of what raised my questions regarding QTS was the discovery of this driver http://radianaudio.com/wp/?wpdmdl=3613 And while I don't realistically expect that this driver would be suitable for say, a T48 (let alone the price - I could almost dual load a pair of cabs with 3015LF for the cost of one of these!), it seems like a pretty unique driver with some interesting specs (21.3mm Xmax!).

Also, I'm curious about how dual loading effects the desired driver Vas? Given drivers of otherwise similar specs, would you ideally want lower Vas for dual loaded cabs, to maintain optimum rear chamber tuning and low end response?

[Bill Fitzmaurice]

I'm pretty sure Bill has mentioned before than drivers with high QTS will have reduced low bass when horn loaded, but what is the effect of low QTS (~0.2) in a FLH?

The same thing, a loss of bass. Qts can be too high and it can be too low. Less than 0.2 is usually too low. Depending on the other specs even less than 0.25 may be too low.
BTW, the chart shown on the data sheet is bogus. No way does that driver have that response, because the Qts is way too low to deliver that result in a ported box, or any box for that matter. The only way it could have that response is with Qts closer to 0.3.

[Boyd]

Thanks Bill.

Yeah I was a bit suspect of that graph too. Just interesting as the specs were so unusual.

How about dual loaded Vas?

[Bill Fitzmaurice]

How about dual loaded Vas?

Vas relates to how large the rear chamber must be. If you want to use two drivers the rear chamber must be larger. Since the overall cab must be larger to allow two drivers to fit a larger rear chamber is a given. With respect to horns Vas is the least significant spec anyway.

[osse]

hi Bill, with the high power/low qts drivers popping up, what would you consider the most important other specs to relate the low qts to? Rog Mogale advocates high EBP drivers which is if I understand these things right somewhat similar with using low qts drivers for horns, good cone control, fast transient response but lacks some of that nice low hz hifi boom and could end in a sterile/fatigueing bass horn.

1. are for example a high EBP(156)/low qts(0,21) driver a bad combination for bass flh's?
2. if 1. is correct, could you compensate the low qts with a lower EBP for a more natural/not so fatigueing sound in flh's? I'm amazed how long you can listen to your designs and never feel ill so obviously you know a thing or two about it.

Thanks!

[Bill Fitzmaurice]

High EBP and low Q in a low Fs driver go hand in hand, you can't have the one without the other. IMO ideal EBP for a bass horn is in the vicinity of 100. Higher EBP is OK for midbass horns.