[Mike P.]

A lot of this gets over analysed. All any modeling program can do is give a ball park idea of what to expect. Linearity, distortion, compression, panel resonance, etc are all extremely important when talking about critical listening as in music reporduction, but way to much is of this is focused on for a HT environment. Below is an example. I know what this graph "sounds like" because I built it. An IXL-18 in 12 cu.ft. tuned to 16 hz with three 4 inch ports.

I can ship this sub away and have it tested. There will be graphs of distortion, port compression, frequency response, etc. showing how a SDX15 or a LMS18 is superior to my IXL-18. Yet when a canon blast goes off at 120 db at 20 hz and the whole house shakes, it's nothing but pure pleasure on peoples faces. All you need to do to build as great HT sub is pick a decent driver and stay within the manufacturers recommendation for Xmax and power handling. Then sit back and enjoy the experience. For the majority of people it's what it's all about.

 

[Mike P.]

With your post showing two different drivers tuned to 16Hz, I assumed you were referring to HT. For music applications the only thing you can do to be guaranteed the results you're looking for is go with what has been proven. I would think it's safe to say that using a sub at 50% or less of its capabilities is within the linear range. There will be small differences between subs at those levels that can be seen on a graph, but if you can't hear any differences, there would be no point in persuing it further.

 

[Mike P.]

Is this at the same SPL?:scratch:

I was using the SDX15 and LMS18 as two examples that would probably have better test results compared to the IXL-18.

 

[Mike P.]

The final result is going to be dependent on the amount of room gain from the specific environment. There are build threads that show the modeled response, the actual response and the final response with equalization applied to create the smoothest response.

 

[Mike P.]

Modeling will show you the effects of comparing different cabinet sizes and tunings of the same sub or different subs. My point is the final in room frequency response looks nothing like the modeling. For example, model the Adire Audio Shiva sub in 2 cu.ft. sealed. Now compare that modeled frequency response to Waynes in room response of unequalized and then equalized graphs.

http://www.hometheatershack.com/for...led-ported/15599-built-subwoofer-project.html