Axiom Home Page Forums General Discussion Technical Questions Towards Better Bass

There are two things I ran into recently that I am surprised to not seem to appear in mainstream bass discussions.

1. Schroeder point (hope I go the name right)

It seems there is a point in each room where soundwaves change in behavior from modal to, um, non-modal (cant remember the proper term). In most rooms it is between 150 and 200 Hz. It moves lower in bigger rooms.

The proposition is that one treats sound in the modal region differently than that other region.

2. Bass does not localize until well above 80Hz, more like 150 Hz.

If the second statement is true, how did THX arrive at 80Hz as its recommended crossover point??

They say "trust your ears". I felt at 80hz crossover I could hear where the sub was from (back of the room), but at 60hz crossover, it seemed to even the bass out and I couldn't tell where it was coming from. That's what I felt I heard anyway, whether it was because that's what I "wanted" to hear is a different story.

Hi,

I'd put it another way: Bass starts to localize acoustically at frequencies higher than 80 Hz. Or, at 80 Hz and below, bass is not easily localized in most rooms.

Of course, if you have mechanical vibrations from a good subwoofer that travel through the wooden floor or frame of your couch, as it sometimes does with my EP500, which sits next to my couch, then mechanically the bass is sort of localizable, but most of the time I've found that 80 Hz is generally excellent as a crossover point.

You do have to experiment, as room resonances and standing waves pile up in every room rather differently, but 80 Hz is a very good starting point.

Regards,
Alan

set sub in corner facing paralel to the wall set at 100 or 80 depends on size of sub

? ummm ok.

OK, so 80Hz is the 'no-brainer' point. Nobody is going to complain about localized bass if they follow THX. That makes sense.

If I understand you correctly, the way the room interacts with the soundfield will have an effect on how/when bass localizes so its different for every room.

Here's the thing. It seems there is fairly wide agreement that most of the sound that makes a boom sound like a boom and a thwak sound like a thwak is contained in the upper bass region. I saw a few postings containing time based frequency charts of low frequency events in movies and most of the energy appears to be between 40 and 100Hz with stuff sometimes extending up to and beyond 150Hz.

It also extends down to 20Hz, but I was surprised at how little energy there is below 20Hz.

You hear a lot of complaints about missing bass slam. The solution is always get a bigger sub that digs down low, but it seems that the issue is not really down low and that the issue is with the capability higher up.

Reading the notes from a recent sub get together it was interesting that people were very impressed with some high efficiency pro drivers that did not dig down deep, yet had very strong tactile bass.

Further reading suggests that, unless its a very good driver, there is a trade of between low extension and upper bass performance: its hard to get both.