0 Members and 1 Guest are viewing this topic. Read 24136 times.
Some things are true whether you believe them or not.It's pesky a lot of the times, but that's the way it is. Cheers,Dave.
I think, the lower the frequecies that harder is to located as what AJ said. In a real world, we dont listen to test tone, we listen to musics with a range of low frequencies, and that helps us locate where is comming from.
If you do measurements of frequency along the speaker response from measuring on the rear, there will be a big gap in response. The high will be dminish over the lows. Im not sure if that would still qualify as omni if you get a dimish response from a different angle.
Well in this case, what is left is the woofer and the baffle. The enclosure no longer is part of the contributing factor. In an open baffle, when you get in 90 of axis, there will be a cancelation of front and rear waves, so how does that constitute a omni?
Yes AJ, i undertand that in a enclosed sub, most of the frequencies will wrap around the sub itself. But this is also dependent to the baffle length. Though, no one will make a sub with 20 feet long baffle, the example is to show that the frequency it self is dependent to the baffle length. If you do measurement of a sub with 20 fett baffle, from front and back, you will end up will different response, specially to the 20 feet wave length frequency. In this case, at least an enclosed subwoofer ( the whole unit box and the woofer) is not a ominirectional source. The woofer becomes the radiating source, right? Because thats what the vibrations starts and create that low frequency. The frequencies will wrap around the sub from the front and not from behind.
Just because it's OB does not stop it radiating omni. In fact, it MUST radiate omni in order to create the cancellation you see at the sides of an OB. If it did not radiate in that fashion, the cancellation could not occur.Bryan
That's not conjecture. When a (sub) driver is pushed hard, it will generate non-linearities (distortion) in it's acoustic output (from the motor, etc) after the electrical filter.
Yes, the wavelength has to be large with respect to the box size. AJ did imply that I think.
Medium Jim,This isn't proof of anything wrong with what was said. If it is because the content above the expected crossover point is getting through (not hitting an acoustical "brick wall") that causes it, then the culprit is not actually bass frequencies being played in mono.
Well, in the case Medium Jim gave, where given stereo signal to separate left and right subs it would not do this, and only does it when given mono... if that is accurate the explanation here doesn't fit. It would be true on both cases and only when driven hard.I think it is actual musical information that is being produced from the subs, higher than the crossover would indicate, and not a matter of distortion.Also, forgot to mention before, a down firing sub has similar benefit to the bandpass at reducing the "stray" acoustic output. -Tony
I don't understand the first part of your response, but the middle part is incorrect. It has nothing to do with music, stereo/mono or the crossover itself. The slope could be 24db or 240db, it's irrelevant. Because the source of the detectable HF components are being generated in/by the driver itself, after the amp/XO. No amount of filtering the input signal has any effect. The caveat here is that the driver is being driven hard enough into non-linearity for it to create harmonics high enough in frequency and intensity as to be detectable.Down firing would be very limited in effectiveness as the harmonics can fall into "mid" bass frequencies that the down firing orientation/floor absorption do little/nothing to attenuate. A damped bandpass would be far more effective. I think that's why Earl favored them. Though he may be leaning towards sealed these days. Which is smart (but too long for me to go into technically).Please note that I have been careful not to say that the 80hz (clean, without detectable harmonics) guideline for (non) localization is absolute. It isn't. Things are a bit more complex that that, but it is still a good guideline.cheers,AJ
Down firing would be very limited in effectiveness as the harmonics can fall into "mid" bass frequencies that the down firing orientation/floor absorption do little/nothing to attenuate. A damped bandpass would be far more effective. I think that's why Earl favored them. Though he may be leaning towards sealed these days. Which is smart (but too long for me to go into technically).
I really thought that the cancelation was due to the front and rear waves of th woofer. Am i missing something?
It is - but from the fact that they are naturally out of phase. The fact that each of the phases radiates spherically is what allows them to cancel to the sides. If they were not radiating through the full 180 degree arc (and farther), they could not cancel.Also, in general all should remember that we're tending to concentrate to the sides - the radiation is 3 dimensional. The waves do not cancel vertically as they do to the sides. Bryan
The waves will actually wrap around the sides of the cabinet and come off of the front wall of the room. This is well known and proven. Look up SBIR. Believe what you will but this does happen.My point in the arc was in line with the discussion on OB speakers where they tend to cancel at the sides.
Ok, if they wrap or radiate around why not just say it that way, why use the word omnidirectional? I have never heard omnidirectional word apply into something that is not an object. A bass frequency is a measurement and can not radiate on its own. A subwoofer can. So what would be the proper way to discribe omni directional, the bass, the frequecies or the sub?Is not like i dont want to believe, but wording seems off to me.
