Below what freq. does sound become omnidirectional?

[heresy2guy]

I've heard and read about bass being omnidirectional, but where does this begin in terms of frequency, i.e. below 200hz, 100hz, 60hz, etc...?

[Guest " "]

120hz

[sfogg]

Omnidirection or not localizable? Omnidirectional (as in radiation
pattern) will depend upon the size of the device reproducing the bass.

Gross Localization is somewhere around 80hz. However there are other
perceptual pieces to bass response such that stereo bass (as compared
to mono) is perceivable down to around 40hz.

Shawn

[DrWho]

Shawn nailed it pretty good....I just wanted to add that pretty much any 15" or smaller subwoofer is going to be nearly omnidirectional to as high as 200Hz. There are always exceptions, but with typical home environments, you can trust that the subwoofer is effectively omnidirectional at every frequency it plays.

[heresy2guy]

Thanks guys! The reason I was asking had to do with the khorn - I know that there's an issue with proper stereo imaging in large rooms do to the necessity of corner placement. It had been discussed on this board before that one way to avoid this would be for the HF section of the khorn to be moveable, so you could track it, or pan it, left or right in order to adjust for the proper imaging depending on the size and shape of the room without having to yank the speakers out of their corner recesses, which woudl destroy the bottom end. I know the khorn squawker dips to 400hz, so from there on up you could effectively direct the sound to where you want it to go should the khorn HF section swivel. It was the low frequency folded horn that I was thinking about. I guess I don't really have the technical expertise and/or lingo to explain it all, but I was picturing the khorns in the corner with their HF sections swiveled somewhat to project the best stereo image for the chosen spot of a large room (say, where the couch is placed). I can envision the dispersion from the HF section with the section thus swiveled and was, mentally, trying to contrast it with the dispersion from the folded horn (below 400hz) radiating straight out of the corners and into the room. In other words, if the Khorns upper section could swivel as above to affect a proper stereo image in the desired spot in a large room, would the resulting sound still sound "right" and "whole" seeing how the bass bin would be fixed into the corner and not able to match the same directional pattern as the swiveled HF section? That's why I was originally asking about the omnidirectional pattern/dispersion of the lower frequencies. I hope I didn't overly complicate or confuse anyone with what I'm trying to say and learn - lol. Thanks - H2G.

[DrWho]

Ah, the problem gets a bit more complicated when you throw bass horns into the mix. What you're really interested in is the horizontal polar response for the khorn (and ideally the bass bin and the MF/HF sections separately). Your best bet for obtaining these plots is to hunt down Roy and give him lots of fishing bait, blueberries, ribs, and ice-cream []

Looking at the khorn's design - I've always wondered how the sound was released from the horn, since the exit essentially fires down the side of the wall. If you think you've got good ears, you could always disconnect the MF/HF section and listen to the bass bins alone and walk around the room. Try to pay attention to the 200-400hz region and see if you can't tell whether or not it disperses evenly in all directions.

You could always just turn the tops towards the listening position and see if you like the sound - but I think I would sooner move to false corners and rotate the entire speaker. Only then will you 'know' that you don't need to redesign the crossover.

Do you have any form of measuring equipment?

[PrestonTom]

Ah, the problem gets a bit more complicated when you throw bass horns into the mix. What you're really interested in is the horizontal polar response for the khorn (and ideally the bass bin and the MF/HF sections separately). Your best bet for obtaining these plots is to hunt down Roy and give him lots of fishing bait, blueberries, ribs, and ice-cream []

Looking at the khorn's design - I've always wondered how the sound was released from the horn, since the exit essentially fires down the side of the wall. If you think you've got good ears, you could always disconnect the MF/HF section and listen to the bass bins alone and walk around the room. Try to pay attention to the 200-400hz region and see if you can't tell whether or not it disperses evenly in all directions.

You could always just turn the tops towards the listening position and see if you like the sound - but I think I would sooner move to false corners and rotate the entire speaker. Only then will you 'know' that you don't need to redesign the crossover.

Do you have any form of measuring equipment?

Mike,

Slow down and think this suggestion through (re: walking around the room to listen to the dispersion/fall off when just the bass bin is connected).

You suggested a frequency band of 200-400 Hz. The wavelengths involved are 2.5 to 5 ft long. Unless the room is anechoic, much of what you will be hearing as you walk around is the speaker interacting with the room. Various standing waves are going to dominate the apparent loudness of what you are hearing. An anechoic measure or even anechoic with 1/4 or 1/8 space loading would be tricky to extrapolate from. Although they are valid measures in that environment, once that respsonse gets convolved with the individual's room response (unknown at this point) it is difficult to predict what the combined effect might be.

Just to drive home the point. Put your low fequency signal through the bas bin then stand on axis (0 deg) and simply walk backwards (slowly and remain on axis). The apparent loudness will fluctuate wildly as you step in & out of various room modes.

It is tricky stuff.

-Tom

[mas]

"What you're really interested in is the horizontal polar response for the khorn"

Please read what Tom has written again.

And Mike, stop once again and think about this... ( don't you love how we just move you around like a puppet! [] ?)

You have a bass horn unloading into 1/8 space. And we are now worrying as to whether the bass horn's Q may be more focused than that? Heck, folks can't achieve that Q using wave shaping techniques such as the cardioid sub configuration. And yet we are still concerned about the possibility of 'beamy' bass in 1/8 space? If only we had such problems!

Let me put it another way...If you can find a configuration that can reliably generate well controlled bass dispersion with a Q greater (more focused) than that presented by 1/8 space, PLEASE call me, as I know some folks who would gladly pay for the rights to use it!

Ah, Flatlanders... the joy of myopically focusing on the frequency response. Only that could have folks chasing the Q of a bass horn in 1/8 space!

[][][]

Have fun!

[DrWho]

Yes, I am well aware of the modes in the room - and yet even after pointing it out I would still give the same recommendation to walk around the room. Wow, go figure...It's really not that hard to tell that a speaker starts beaming (or the opposite) - yes, even in a room in the 200-400Hz range. If you've never tried it - then booger off. If you have and not succeeded - then you're not listening correctly, or your room is utter crap in that range. We're not talking about 1dB and 1 degree accuracy here [6] But even then, if the room is crap in that regard, then sitting off-axis from the speaker is going to be crap too.

I'm pretty sure it was in the JAES article, but it was talking about the design of the Jubilee relative to the khorn and how the better HF extension was partially obtained by collapsing the horizontal polars - as compared to the khorn where the exit flares did not allow this - almost implying that there is less energy in the top end of the khorn directly on-axis. If you look at the Jubilee bass bin polars, you'll notice that it's about 50 degree wide at 300Hz, so claiming that directivity at those frequencies is unobtainable is just pure crap.

As far as myopic frequency response....what the heck are you talking about?!? You take your distaste for the frequency response way too far - and this isn't even a situation where the time domain is changing. Holy fricken crap. It most certainly makes an audible difference. By all means live in your little world of the time domain and signal aligned Bose speakers [6]

Man, I love it when people try to shoot down "easy cheap ideas" and then complain about the ideal world and then don't provide any useful information....oh, and keep repeating themselves without applying anything to the specific question at hand.

So englighten us....what exactly would you recommend for improving the sound in this situation without spending money? How exactly does looking at the signals in the time-domain benefit us in this situation and how is it going to change the implementation of the "mod". Or do you prefer making it seem like others don't understand anything at all because they offer compromised approaches in context of the specific situation?

Of course I don't expect a positive natured reply, but instead just more crap about how I don't know anything and therefore must be making recommendations that lead to worse sound [] Nobody is targetting the ideal here.

[PrestonTom]

Mike, Mike, Mike,

No one is beating up on you. Far from it. I am just reminding all of us that low fequencies mean big sound waves. As such, you should not focus on the "output of a speaker cabinet" rather the focus should be on the output of the "cabinet/room" as system. The effects I was referring to are certainly not 1 & 2 dB fluctuations. They are much bigger than that and other consequences creep in also (time stuff).

Many things may have similar measures when viewed using comparably with a long (ish) term amplitude spectra. But they can sound quite different. The difference is, in part, in that other domain (the time domain). MAS stresses this issue and I do not disagree. But I will let him speak for himself....

Incidentally, these things are difficult to measure, capture and understand. It is no mystery why folks shy away from them. I had a poor grad student in my lab that had to explain the use of Golay codes etc to me for a project we doing (measuring acoustic diffraction patterns around the head and external ears). It was frustrating for the both of us when we were trying to get our arms around some of these things. Eventually he educated me (slightly), but it was a struggle.

-Tom

[DrWho]

As far as the 1dB/2dB changes...you missed my point. I was saying that we're not trying to determine the polar response of the speaker to within 1dB and 1degree. I was trying to elude to gaining a general feel for how the speaker is behaving as being more than enough. A 6dB change by moving off-axis is certainly going to be noticeable - even in light of +-10dB changes occuring in the room...(in fact, the time domain analysis will even support this).

I think you missed the meaning of my post....so let me try to sum it up in one phrase and see if it makes more sense:
Saying something along the lines of "that is crap because it doesn't follow my ideal thinking" is much different than saying "that is crap, here is a better approach based this better understanding". See the difference?

What's the point of saying, "wow - hey idiot, stop looking at the frequency response" and then just stopping there? It ignores the personal things Mark knows about me (I don't "debate" the same things he does in all the other threads only because I think it makes me look smart), and then it doesn't provide anything beneficial to the discussion.

Or am I way outta line? If so, I do sincerely apologize. I'd hate to find myself biting a hand that is feeding me...

[garyrc]

Back to the original question, reworded to use "not localizable:"

"Below what frequency is bass not localizable?"

I have a 15" Klipsch RSW-15 sub, with the low pass set for 40Hz at 36 dB per octave. It is not often used for straight music listening, but is always used when running a movie, along with Klipschorns, a Belle Klipsch center, and Heresy II surround. The sub is in phase, well integrated, and set a tad lower than flat via acoustical measurements.

With the noise signal my AV movie preamp uses to adjust channel levels by sending the noise signal to each speaker in turn, the bass is as localizable as hell, even though set for 40 Hz and below!! It's very obvious where it is.

With movie music & effects, the leading edge of the attack of whatever instrument is playing, or Foley is sounding, almost always comes from somewhere else in the sound stage (even though some big bass drums have a fundamental around 40 Hz, a lot of the beater contacting the drum head is above that frequency), and that attack seems to localize the sound away from the sub, and places it wherever it should be. Once in a while, very rarely, the sub gives itself away. When the movie people less than creatively use their famous "bass machine," and it is set for very low frequencies, with no natural instrumental attack, we know where the bass is coming from.

[sfogg]

"With the noise signal my AV
movie preamp uses to adjust channel levels by sending the noise signal
to each speaker in turn, the bass is as localizable as hell, even
though set for 40 Hz and below!! It's very obvious where it is."

Are you sure your preamp is filtering the noise with the crossover point set? I don't think they all do that for some odd reason.

Shawn

[TheEAR]

40Hz and below bass is not directional,if it apears to be the crossover slope is not steep and you hear information a good deal above 40hz. We can say even as high as 80hz can be listed as omnidirectional. As the driver can face any direction and the pressure generated bu the driver will do the trick.When sound is very directional the driver should face the listener.

[bodcaw boy]

Yes, I am well aware of the modes in the room - and yet even after pointing it out I would still give the same recommendation to walk around the room. Wow, go figure...It's really not that hard to tell that a speaker starts beaming (or the opposite) - yes, even in a room in the 200-400Hz range. If you've never tried it - then booger off. If you have and not succeeded - then you're not listening correctly, or your room is utter crap in that range. We're not talking about 1dB and 1 degree accuracy here [6] But even then, if the room is crap in that regard, then sitting off-axis from the speaker is going to be crap too.

I'm pretty sure it was in the JAES article, but it was talking about the design of the Jubilee relative to the khorn and how the better HF extension was partially obtained by collapsing the horizontal polars - as compared to the khorn where the exit flares did not allow this - almost implying that there is less energy in the top end of the khorn directly on-axis. If you look at the Jubilee bass bin polars, you'll notice that it's about 50 degree wide at 300Hz, so claiming that directivity at those frequencies is unobtainable is just pure crap.

As far as myopic frequency response....what the heck are you talking about?!? You take your distaste for the frequency response way too far - and this isn't even a situation where the time domain is changing. Holy fricken crap. It most certainly makes an audible difference. By all means live in your little world of the time domain and signal aligned Bose speakers [6]

Man, I love it when people try to shoot down "easy cheap ideas" and then complain about the ideal world and then don't provide any useful information....oh, and keep repeating themselves without applying anything to the specific question at hand.

So englighten us....what exactly would you recommend for improving the sound in this situation without spending money? How exactly does looking at the signals in the time-domain benefit us in this situation and how is it going to change the implementation of the "mod". Or do you prefer making it seem like others don't understand anything at all because they offer compromised approaches in context of the specific situation?

Of course I don't expect a positive natured reply, but instead just more crap about how I don't know anything and therefore must be making recommendations that lead to worse sound [] Nobody is targetting the ideal here.

go get'em doc!!

have a blessed day,

roy delgado

[bodcaw boy]

"What you're really interested in is the horizontal polar response for the khorn"

Please read what Tom has written again.

And Mike, stop once again and think about this... ( don't you love how we just move you around like a puppet! [] ?)

You have a bass horn unloading into 1/8 space. And we are now worrying as to whether the bass horn's Q may be more focused than that? Heck, folks can't achieve that Q using wave shaping techniques such as the cardioid sub configuration. And yet we are still concerned about the possibility of 'beamy' bass in 1/8 space? If only we had such problems!

Let me put it another way...If you can find a configuration that can reliably generate well controlled bass dispersion with a Q greater (more focused) than that presented by 1/8 space, PLEASE call me, as I know some folks who would gladly pay for the rights to use it!

Ah, Flatlanders... the joy of myopically focusing on the frequency response. Only that could have folks chasing the Q of a bass horn in 1/8 space!

[][][]

Have fun!

actually with a horn that large, you can get a nice pattern going at 200 hz and up.....

have a blessed day,

roy delgado

[mas]

Poor Mike. ;-)

I referred strictly to the LF response and realm that is not dominated by any beaming!

Sure you can wander about the room until the cows come home and notice varying LF response, but none of that is going to be attributable to the LF 'beaming' and polars.

Hence re-reading Tom's referral to the issue of standing waves and room modes. You want to deal with the varying LF frequency response? Deal with the room modes. You want a solution? Deal with the standing waves. I would consider bass traps.

Gee, why might someone suggest this? Precisely because we have tried it! But perhaps not with the degree of experience you have had. The irony is that we were doing it before you were born. ;-)

And if you have a controlled 50 degree dispersion in the LF bin, it should be published precisely for that reason. So now we have bass bins with higher Q than mid and HF drivers. And no, I don't really care what upper limits one is trying to extend the bins MF reponse. That wasn't the issue,and it certainly wasn't the same aspects of the bin to which you were referring to with regards to the LF energy propagated along the walls.

But maybe you are right... An attempt to identify room modes and standing waves, looking at a waterfall response and utilizing tools in the time domain to determine where those room resonances are, probably wouldn't help at all. Nope! Those fools who use them are just carnies luring unsuspecting rubes into their lairs.

No useful ideas? Really? We have a 1/8 space horn in a 90 degree corner and our crisis is identified as LF beaming. Yeah, I wouldn't want to be outside the sweet spot there. Especially as you made a comment, something about the low frequency energy following the walls. So we are in a limited space, the bass energy is following the walls and the problem is a limited horizontal polar...Well, you've lost me. But I am easily lost.

But then, on the other hand, without any measurements or walking about, I wouldn't be at all amazed that room modes will dominate in the LF below ~250Hz. In fact,I could hang out a shingle and become an acoustical pychic! Below 250 Hz, I would risk my reputation and predict the presence of apparent frequency anomalies based upon the presence of demon standing waves!

And silly me, (as my problem, despite my psychic prowess, is that I do not put much stock in psychics), I would simply use the appropriate tools to identify and treat the room modes. But then, I have done this and none of this really amazes me. So, no useful ideas or solutions. Where I come from avoiding wasting allot of time chasing snipe is considered a useful suggestion. But as you have all the time in the world, by all means, explore to your hearts content and reinvent the wheel at your hearts leisure. Ah, youth!

Hmmm... So the criteria is how to fix room modes "without spending any money". Well, Mike, you've got me there. You might just have an expense if you build some bass traps. Now, don't get me wrong. I would never go so far as to suggest that one actually measure and determine exactly what it was that they were actually trying to fix, as I find that concept to be an anathema, but walking around some more may help, if not to fix the room modes, then to vent some of that emotional energy which seems to be a larger impediment to addressing the issue than determining what modes one might need to address.

And I'm sorry if acknowledging and addressing room modes is simply an "ideal". Now me, I would call it practical, But call it whatever you want. After all, its your reality if you say it is.

And where is this nonsense coming from that anyone has said that you 'don't know anything'? Wow! Sorry, but you are on your own with this one, as neither I nor anyone else (of which I am aware) has ever said anything meant to imply any such thing. But if someone said such a thing to me about you, I would counter that you are awfully sharp! After all, being an old fart, I am still sitting and don't have the wherewithall to be up walking around. Gee, maybe walking around would help...;-)

And just where in Heck (you know the place next to the Hades place) do you mean and get off saying:
"What's the point of saying, "wow - hey idiot, stop looking at the
frequency response" and then just stopping there? It ignores the
personal things Mark knows about me , and then it doesn't provide anything beneficial to the
discussion."

When I ever called you an idiot without a big smile on my face? And if I ever do, THEN you can b!tch! Got it!? But I haven't called you an idiot! And except for the past few minutes, I never thought I would! ;-) But keep this nonsense up and I just may have to! I merely suggested that you were getting too caught up in the the trees and merely would benefit from standing back and seeing the forest, and realizing that you are dealing with standing waves! Thus I pointed to Tom's astute observation where he stated exactly that! From there I assumed that a smart whippersnapper like yourself would know what to do with standing waves! But then, of course, we all know the answer! You walk around and intimidate them into submission!

But I will admit, your nonsensical reference to me and Bose should hurt! I a sure there is some nexus between the two, but unfortunately the comment is wasted on someone as simple as I, as I just don't get it, and I never have had Bose speakers, but I am sure it will hurt when and if I ever figure out the oh so pointed jab!

And when I refer to Flatlanders, I refer to a general trend, a focus that myopically focuses on a particular point of view and refuses to expand their horizons and to hazard to risk looking at an issue from other varying points of view. If you feel this applies to you, so be it, that is your interpretation and I wouldn't dare debate that. But I do find it amazing that my standing back and making what was intended to be a light quip in a humorous jest was so dastardly.

But then, a silly person like myself, after all the sturm and drang of the drama, would still determine the nature of the room modes and treat them. And if my legs got stiff, I just might walk around to determine of the treatment actually solved the problem. But then, being a silly person, I would also take measurements to confirm that notion in the "ideal" world too - as I am just that kind of guy, I like to do proof of performance tests rather than to simply be satisfied emotionally in my belief that the effort should have been sufficient to fix the problem. But that is my hangup.

I hope you find that you are looking for on your travels as you walk about the room. Oh, and I have heard that those Australian's do a similar ritual...I think its called a 'walkabout'. I wonder if there is any connection? ;-)

[mas]

"What you're really interested in is the horizontal polar response for the khorn"

Please read what Tom has written again.

And Mike, stop once again and think about this... ( don't you love how we just move you around like a puppet! [] ?)

You have a bass horn unloading into 1/8 space. And we are now worrying as to whether the bass horn's Q may be more focused than that? Heck, folks can't achieve that Q using wave shaping techniques such as the cardioid sub configuration. And yet we are still concerned about the possibility of 'beamy' bass in 1/8 space? If only we had such problems!

Let me put it another way...If you can find a configuration that can reliably generate well controlled bass dispersion with a Q greater (more focused) than that presented by 1/8 space, PLEASE call me, as I know some folks who would gladly pay for the rights to use it!

Ah, Flatlanders... the joy of myopically focusing on the frequency response. Only that could have folks chasing the Q of a bass horn in 1/8 space!

[][][]

Have fun!

actually with a horn that large, you can get a nice pattern going at 200 hz and up.....

have a blessed day,

roy delgado

Thanks Roy,

In the mid frequencies polar lobing and beaming can indeed be an issue. And room interaction can indeed exacerbate that phenomena as well.

But being a person of very limited intelligence, I was choosing to myopically focus on the original question and those frequencies that are generally low Q that fall into the realm that might be addressed by the question of "I've heard and read about bass being omnidirectional, but where does

this begin in terms of frequency, i.e. below 200hz, 100hz, 60hz, etc...?"

[]

[mas]

Oh, and for the record...

Anyone who persists in looking at only one domain to the exclusion of the others in acoustics is a Flatlander.

I know that some of you may be inadvertently traumatized by this statement, but you will just have to deal with it.

[]

[DrWho]

In the mid frequencies polar lobing and beaming can indeed be an issue.

That's what I was referring to??? [^o)]

You want to deal with the varying LF frequency response?

No - dealing only with the directivity of the top-end of the bass bin

I don't really care what upper limits one is trying to extend the bins
MF reponse. That wasn't the issue,and it certainly wasn't the same
aspects of the bin to which you were referring to with regards to the
LF energy propagated along the walls.

I am talking about the "HF" energy (not LF) being propogated along the walls in direct response to the concept of sitting off-axis from the bass bin, but on-axis with the top section. This is most certainly 'the issue' and the reason for the question in the first place.

something about the low frequency energy following the walls

Again, just to stress the point - talking about the 200-400Hz region of the khorn's horizontal polars.

"So the criteria is how to fix room modes "without spending any money".

The criteria is how to sit off-axis from the bass bin and enjoy your sound. Even if you have a treated room, you would still have to address changing polars (if they indeed changed).

Btw, I think the "hey idiot" comments got way lost in translation.....I keep forgetting there's no voice inflection on the forum. Not to mention all ya oldfarts [] probably aren't up-to-date on the slang. The only problem is I dunno how to translate it to "old speak" either [][][]