Originally Posted by sputter1
I have a question. How do we know or find out if the 15hz is being coloured by 30hz or by how much if at all?
For example, using my REW graph can we tell if the 15hz is actually 15hz?
I have a SMS bringing down 2 peaks for this graph fwiw.
I think James is just saying that people think they are hearing 15hz when in fact it's a higher frequency that they are hearing. I.e., most people will watch a movie like the new Transformers movie, hear some really great low bass at high levels and think it must be "below 20hz" when in fact the movie is filtered so that it doesn't even permit much sub 20hz content at a decent SPL level, but the 30hz stuff is aplomb and sounds/feels "deep" so they may think they are getting 15hz when it's actually north of 25hz.
Or, take any scene that does in fact have 15hz content, it's obviously going to be mixed with heavy aspects of 20/25/30/35hz stuff intermixed at the same time. What would be cool is to watch a movie with the Spec Labs software running at the same time so you can see where the sub 20hz stuff is hitting.
I recall with my Mirage OM200 (first sub) I thought I was getting lots of really low stuff. Then I upgraded to the PB13, and then figured out "okay, now I know what I was missing". Now with the absolute overkill I have in my room (single PB13 nearfield in sealed mode and 2 dual AV15H subs upfront), there are passages where my head feels like it's going to implode which I don't recall feeling before (or at least not to the same extent).
Jim - run increasing sweeps to about 105/110db (listen for stress on the woofer though) to see if the sweeps remain linear and check for THD as well. If you're "hearing" a lot during the first part of the sweep (10hz to 20hz) it's likely more distortion than anything else.
At 75db you're not going to feel 15hz. But if I recall, you have a ton of room gain at least in one corner up to about 25hz (I recall huge peaks with the PB13 there!).