Originally Posted by bossobass
I wasn't referring to LMS, but instead, a standard overhung driver, as in virtually every driver tested, commercial or otherwise.
I'm not sure what the distinction is between a licensed XBl^2 motor and a Wiggins designed XBl^2 motor, nor am I sure I understand what the age of the design has to do with anything (which is a little over 5 years, to answer your question).
If you're saying that any split gap motor can be called XBl^2 then the license agreement seems lacking.
The motor topology is what is licensed. As Ilkka has well demonstrated, there is more to a subwoofer than linear BL vs. excursion, even though it is a very important contributor. Linearity of the suspension, operational noises, mechanical resonances, thermal dissipation and linearization of inductance and B field with varying power and excursion are all additional contributors to the quality of the end result. Of course even then there is a big difference in a driver with a moving mass of ~300g vs ~80g and what they will be best suited for.
In the past 2-4 years Dan has been doing LOTS of commisioned research into surround design, spider design, the use of shorting rings, etc., etc., often for non-music related operation. I'm not saying Dan is the only one who knows how to design a quality driver. What I am saying that Dan's knowledge and input on a driver's design extends well beyond the rebates in the pole & top plate.
Even then, at some point the paying customer will get what they ask for, or what they are willing to pay for. Trade offs of some level are made in every
Bottom line is that very few Wiggins subwoofers have been tested in a way that gives a frame of reference. There are theoretical advantages and they've been discussed many times. Dan himself has made the case you're suggesting, by mentioning the SDX and AVA drivers, that the XBl^2 license means basically nothing, specifically in the case of the Avalanche drivers, which also have never been tested.
Again, it was never said that the license "means nothing." The license means the motor topology was used as the licensee saw fit, and that an XBL^2 motor can allow for unique shaping of the BL curve, with the potential for very flat BL over some range of excursion. This says nothing of the cone, frame, surround or spider used and what their limits are.
PA-SchmeeA and App-Schmapp. Put that driver in 5 cubes and let someone listen, then switch the driver with the Mael-X, match FR with L/T and match levels and tell me who heard what or how one was better because it's specified for HT apps.
Saying that one has more headroom above X and the other has more headroom below X, or one uses a smaller amplifier than the other, etc. is irrelevant.
If you draw the in-room extension line at 10Hz and listen at average levels in 3-4,000 cubes, there will be no discernible difference.
Not really sure what your point is above. My point was that there are efforts made in either driver which would be excessive in certain applications, and are the reason for the huge price differences. The advantages are still there. The buyer has to decide whether the differences and trade offs justify the price to them. If drivers were compared where one was being grossly over-driven, expect it to sound worse, regardless of how well it works in the first 10-20mm of Xmax.
I understand the problems you face having to work within a strict set of parameters, but no such problems exist in DIY. That's why my subs are Tumult based and yours are not.
The pesky reality of actual availability of good performing XBL^2 drivers 2-3 years ago is the reason the SubMersive doesn't use an XBL^2 driver. I shelved a more expensive and slightly larger design as I couldn't rely on the potential suppliers at that time. Times have changed, and some variation of that product concept will come to life in the not-too-distant future.
I have sampled and rejected plenty of XBL^2 drivers, just as I am using plenty in upcoming designs for AV123, TCA & myself. I'm also still using conventional motor drivers where XBL^2 options had not yet exceeded the performance of well optimized, conventional drivers, or where I haven't had time/money to develop the right custom driver for the use. XBL^2 motor or not, a driver still has to be well optimized for its use.
Tumult is a great driver. I've said so many times. I'm just not sure what XBl^2 has to do with that fact vs the same driver with an overhung motor.
you then followed up with:
Originally Posted by bossobass
It struck me when Ilkka told me the Tumult MKI is a 'bad' driver, meaning high in harmonic distortions vs other drivers. This seems to have been furthered by the results of the SDX drivers tests.
So is the Tumult a great driver or a bad driver? Ilkka's independent testing confirms what has been discussed here and Dan has posted long ago about the design of the Tumult. While many get caught up in a few numbers dependent on other factors, Ilkka's full set of response testing clearly illustrates that the Tumult has higher excursion and suspension linearity than the SDX. Look at the response below 30Hz as the level is increased. You can clearly approximate the excursion required for those levels and can see the lack of compression below 20Hz, which requires that BL be maintained, as well as reasonably low compression overall.
Since we aren't seeing much compression, that suggests that the distortion is related to other non-linearities, especially as excursion is relatively low above 50Hz. The obvious correlation of the distortion rise and its higher order content with the inductive roll off of the frequency response suggests that inductance & current modulation are prime suspects. Ilkka's more recent testing confirms that diagnosis. I found very similar distortion behavior in the Avalanche & Atlas-15 drivers I tested long ago.
In the end, we come back to the fact that the full execution of any design is key, and no single wonder-technology guarantees a great end result. Different motor designs, methods and techniques simply give us more options and flexibility in getting to that end goal.