Originally Posted by LTD02
also, I mentioned this before, but the distortion in the sweep may be partly power related. it is obviously starting to compress based on power from the series below the frequency response sweeps that shows the compression. since there is little compression around the impedance peak, we know that most of that is power related compression. so the excursion related distortion is probably a little better than what is shown in the charts. in other words, if the same sub were tested in a very large sealed enclosure, the distortion would likely be lower for the same amount of excursion.
I suppose that you could coordinate with josh to test one of your drivers in a small sealed enclosure in order to see how distortion scales with drive level. in a small sealed enclosure with a ton of power, you may be way over 10% distortion long before the official xmax is reached for the drivers that you employ.
then again, 10% distortion is only partially meaningful in some sense because it is unclear if that level of distortion is even audible in a controlled setting with experienced listeners in the sub bass. as such, we end up with new metrics such as "usable excursion" which represents some mixture of the point where the driver starts to get noisy mechanically or the distortion really starts to explode.
Yeah, you're getting into gross misinterpretation of the data and philosophizing about sealed subwoofer design. This is where you cross the line in most of our discussions on the subject.
Xmax is defined as the point where Bl drops to 70% and the 10% THD limit is reached. I agree with that average and don't really care what anyone's neo-theory might be. Some have said that VC-gap divided by 2 isn't a good metric. I say prove it. It's a lot closer to reality than stretching 13 mm to 20 mm.
Have a look at the FR of the Dayton in the small box. Does it look like it will benefit from a lower Q (larger box) in actual use? You can put it in an IB for efficiencies sake. The curve will sound like crap and the Xmax won't change.
A K10 on a 220V/50A line is so far beyond any Dayton driver-based DIY system builder's reach I don't know what to tell you. That amp, IMHO, and I've said so before, skews the results of all of the DIY systems tested. In any case, if you see power compression in that test, be prepared to drastically lower the actual results for any end user. There's no way you see power compression. When you pump 2KW long term into a 900W rated driver, It's thermal up top and thermal/Xmax limit on the bottom. And, the amp was certainly not out of power at that point.
If you define Xmax as "some point where the driver starts to get noisy mechanically or the distortion really starts to explode", then the Xmax for the drivers I compared the Dayton to will scale accordingly.
Your formula is foreign to me. I don't have the time or desire to wade into it. It might be simpler to just compare the LMS-U results and draw a conclusion. You might conclude that the Dayton has 55% the Xmax of the LMS-U or some such baloney, and that's fine. Delusion has always ruled in these forums, generally speaking. What I'm debating here is the claim that the Dayton driver has 55% more Xmax than the designer/manufacturer claims it has based on some test Josh never performed.
You're just throwing out insane postulations instead of pointing me to the actual Xmax tests Josh performed.