What about Jubilee Khorn ?

[IB Slammin]

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On 9/18/2003 5:09:45 PM Maron Horonzak wrote:

Rothchild or Ripple or better than bottle,d water.

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Gulp.....Burp......Excuse me.....

tc

[Hel Guedj]

I plainly agree. Especially with Mahler.

[John Warren]

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On 9/18/2003 5:55:16 PM John Warren wrote:

So according to your "physics", I should only be able to hear

18kHz

and up in my headphones.

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Artto-

Above is what I stated, note that I said 18kHz (=18,000 Hz). Why? because the distance between my eardrum and the transducer in the headphone is about .7", enough for an 18kHz signal. So why then do I hear deep bass in a headphone?

You are implying that room size must be comparable to the wavelength being reporduced to "hear" the wavelength.

This is patently 100% false, its a myth.

The techniques to develop deep bass in small rooms are specialized and require that the room be "pressurized" by the drivers in the same manner that the headphone transducer "pressurizes" your ear canal. This means that the room have "leakage" lossess that are known and accounted for. No, it is not simple. BUT it is NOT impossible and NO physical laws need to be broken to achieve the desired goal of deep bass in a small room.

The technique is spelled out in the reference I gave you.

[artto]

John...yes..I read the 18Hz wrong...my apologies.

the other stuff, I don't have time to answer tonight as I am logging off. But I will get you the answer.

But briefly.....the fact is most all rooms (even mine) are not pressurized. Fact number two, the anechoic chamber at Klipsch has a pressurized seal. CLOSED BOX. TIGHT. Every (low frequency)speaker placed in there cuts off at aproximately the same point. How do you explain that John? Let's hear YOUR PHYSICS.

[John Warren]

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On 9/18/2003 7:00:38 PM artto wrote:

How do you explain that John? Let's hear YOUR PHYSICS.

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I gave a reference!

I said it takes SPECIAL ROOM CONDITIONS!

BUT IT IS NOT PHYSICALLY IMPOSSIBLE.

Besides, anyone that has travelled in a true luxury vehicle (say a Bentley) with a well engineered sound system will know immediately that stunningly low bass can be heard in a small volume. It requires that the air be pressurized such that the ear canal is driven in a fashion similar to the way a set of headphones drives them.

Note too, next time you hear that ridiculous BOOM sound coming from that low rider Honda Accord just remember that it provides evidence of the extreme efficiency of the physics of pressurized sound chambers.

[michael hurd]

Take a woofer / box combination that starts to roll off at 50-60 hz in your house, and stuff it in your car. See what happens for your self. Not that I am an expert, or even have a good working knowledge of acoustics, but I know that the cabin gain of an automobile will give you reinforcement in the lower frequencies.

[WMcD]

I'm not quite sure where to wade in here.

The Jubilee's we heard in 2000 at Hope were, in my view, the theater model, with a facade of hardwood and grills. A very nice piece of design. The treble unit was some fiberglass horn with a B&C driver. I didn't see the crossover. Fair to say that these were mockups or prototypes at best.

Perhaps the factory was keen on having something to show while Paul was still with us. I'd vote for that. We were not shown the midrange horn which appears in the picures.

There was a comparison between the K-Horns on the back wall and the Jubilee on the front. I thought the Jubilee's has better bass while the K-Horns had better treble. The hardware would be expected to create this.

I can see why Klipsch might have a problem with getting treble unit for the Jubilee unit at the "right" cost. If is is to be exposed to view, a nice hardwood implementation will be a work of art and engineering. Difficult to do both at once. For all the merits of the K-5 and K-400 they are not very pretty, except to the true believers.

On the room thing. I'm inclided to agree with Art. It takes a pretty big room to get eigenvalues to give a boost at 40 Hz. That is what I see in the math. Opposite corner to opposite corner (i.e. front right bottom corner to back left top corner) might make it possible in a reasonably sided room. And if there are two sending units where the bass is in phase, that helps. Therefore, things may not be as flawed as one thinks at first blush.

Please note that his eigen value thing relies on pressurization at the wall.

On the other hand, I'm not so convinced about the effect of pressurization of the whole "chamber" either. It makes sense that if there is on open doorway or kitchen passthrough at the back or the room, there can not be any gross pressurization. But that might not be totally correct if we take a close look at localized situations. Consider that any section of a horn is open toward the mouth. Given that our corner is supplemented by the ceiling, there is going to be some local pressurization because it is more like a horn.

The bottom line is that both standing wave phenomenom in a relatively large area (eigenvalues and standing waves), and pressurization in a relatively small areas are basically relying on common principles of localized sealed off conditions compared to wavelenght. Rooms have those. And what is small or large may well overlap. It may well be that any given room response is a combination of both.

My best thoughts.

Gil

[John Warren]

The physics of deep bass in small rooms requires that the room dimensions be smaller than the wavelength of sound being produced and that the time constant of the room resulting from pressure leaks be large compared to the frequency being reproduced.

The procedure and physics are published and the high end auto sound installers are close to the ideal conditons with the best automobiles. It is difficult to do in a real room but it is not impossible.

Again, I reference Pierce's article. A number of JAES articles about this topic are also available. It's nothing new.

[sfogg]

" Fact number two, the anechoic chamber at Klipsch has a pressurized seal. CLOSED BOX. TIGHT. Every (low frequency)speaker placed in there cuts off at aproximately the same point. How do you explain that John?"

If that chamber is truely anechoic at those frequencies then it isn't influencing (no reflections) the bass reproduction. So even if it were true that the room size limits the low end response (which it doesn't) then this wouldn't be what is occuring in that anechoic chamber.

Along the same idea as the headphone example is if the wave needs to completely fit into the space it is in then how could we hear bass (or even midrange) at all with our tiny little ear canals?

An example... fill your bathtub with water. Now go to one end and with a board or something slowly push up and down on the top of the water. With a little work you can easily create a wave which has a much longer wavelength then the length of the tub. It is no diffirent with sound waves in your room.

Shawn

[formica]

I think John Warren captured the gist of my initial question, in a more direct way.

Actually from the responses so far, I somehow get the feeling we are discussing two different things;

1) Does a sound with given frequency need to develop its full length in order to be audible by the human ear?

My understanding of the ear would indicate that full wave length development is not required... as the ear will pickup sounds as they "pass by"... whether outdoors, in an anechoic chamber, or wearing headphones... as long as the membrane is vibrated at a given frequency. The room, per sae, does not prevent the sound from being created... but perhaps affect what we perceive of the sound once it has been created.

2) Will a small room's effects alter a sound wave to the point that it no longer distinguishable by the human ear?

I believe this is where the true question lays... will the room reflections of the lowest bass frequencies render them beyond recognition?. For very long wavelengths, the leading edge of the reflected sound will more than likely reach the ear before the trailing end of the same wave has completed it's first pass. The ear will be excited by the initial wave, as well as its reflection simultaneously. The brain, combined with the outer ear should be able to distinguish the difference between direct and reflected sounds... after all, the human brain is very capable of filling in and differentiating information, and a wave pattern is very predictable. Or is this where the problem lies?

Unfortunately I don't have the issue of AudioXpress with the "Deep Bass in Small Rooms", nor is it available on their web site... but this would probably clarify some of the physics of bass in rooms.

Later...

Rob

[John Warren]

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On 9/18/2003 11:30:37 PM formica wrote:

1) Does a sound with given frequency need to develop its full length in order to be audible by the human ear?

My understanding of the ear would indicate that full wave length development is not required... as the ear will pickup sounds as they "pass by"... whether outdoors, in an anechoic chamber, or wearing headphones... as long as the membrane is vibrated at a given frequency. The room, per sae, does not prevent the sound from being created... but perhaps affect what we perceive of the sound once it has been created.

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This is the exactly right and (quoting Pierce) "the ear responds to pressure variations and any mechanism that results in a time-varying change in pressure between the outer and inner ear of sufficient magnitude in frequency will result in the perception of sound"...."This is why headphones, for example, can convey real LF information, they simple cause a difference in pressure between the inner and outer ear (of sufficient magnitude, my words).

I will further quote Pierce...

"Contrast this to the behavior required of the woofer when the woofer wavelengths are small compared to the room dimension, or the so-called "free-field" conditions (also approximated by an anechoic chamber). Here the excursion of the woofer must go as the inverse square of the frequency in order to maintain a flat response. This condition is satisfied mechanically by the drivers operating in the so-called mass-controlled region of operation, above the fundamental mechanical resonance. Below resonance, the system is operating in the stiffness controlled region and the excursion no longer goes as the inverse square of the frequency. This is precisely the behavior needed for flat frequency response in the pressurized room case. It would seem then, that you need to achieve a system where the room dimensions and the system resonance are coordinated in a way such that above resonance the system sees the near free field conditions and below it is working to pressurize the room as a whole."

How to do it>

1. Largest room dimension not to exceed 1/4 of the wavelength of the system resonance.

2. Room cannot have any significant leaks.

3. The speaker enclosure itself cannot leak back into the room (here and infinite baffle or seald enclosure are the only options). NO BASS REFLEX.

There are other rqmnts, these are the basics.

[John Warren]

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On 9/18/2003 7:00:38 PM artto wrote:

But briefly.....the fact is most all rooms (even mine) are not pressurized.

>>The fact that you do not have a room that satisfies the conditions necessary is meaningless.

Fact number two, the anechoic chamber at Klipsch has a pressurized seal. CLOSED BOX. TIGHT. Every (low frequency)speaker placed in there cuts off at aproximately the same point. How do you explain that John? Let's hear YOUR PHYSICS.

>>An anechoic chamber converts SOUND PRESSURE (i.e. acoustic power) into HEAT. It is designed to work COMPLETELY AGAINST what is being proposed by the pressurized room concept. HOW Mr. Artto do you propose, using your physics, to pressurize a room that is converting sound pressure to heat as efficiently as you are generating it?? An anechoic chamber is attempting to create a free-field, open space.

You CAN pressure an anechoic chamber, it would require that you SATURATE the chamber with so much acoustic power that the wedges are no longer effective in converting sound to heat.

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[John Warren]

Double post

[artto]

After pondering some of the peculiar responses to my posts, it occurred to me that there is probably some amount of misinterpretation & misunderstanding going on here. First let me clarify a few things. When I wrote about room cut-off frequency relative to speaker response, this does not mean that this is the absolute low frequency that a can be produced in any given room. Just as in speakers, the term cut-off frequency (also known as the turn-over frequency) is defined as the lowest or highest frequency in the pass band of a filter or audio device (or this case, the room itself) and is usually considered to be the first frequency that is 3dB lower than a reference frequency (usually somewhere in the middle of the band). This is NOT saying that the room simply cuts off ALL frequencies below that point, or that lower frequencies cannot be produced. It means the frequency response begins to roll-off around that point because of the speakers interaction with the rooms boundaries. The smaller the room, the higher this frequency is. Can you produce a 16Hz tone in a smaller room? Well, yes, BUT, look at what happens here. Even if you have a speaker that tests flat down to 16hz in free space, you will still need tremendous amounts of boost at that frequency in a very small room (barring any room resonances) to make it sound or measure (ugh) 'flat'. The smaller the speaker, the more boost (EQ) you will need to bring that low-end up. Same thing with the room. The smaller the room, the more boost will be required for a flat response as the frequency goes down into the sub-bass region. There is no free lunch here. You can accomplish this any number of ways. All of them involve increasingly large amounts of speaker and/or amplifier power. And then of course, were back to the question of where & how much of a trade off do we want to make between speaker size, or number of speakers used, how much additional amplifier power is required, and the associated increase in distortion and noise that results from this. Not to mention the costs involved. At some point, more real estate (larger room) actually becomes cheaper. And its also a better solution. Lets not forget, that in the smaller room, with the pumped up sub-bass frequencies (whether this is accomplished via subwoofers or electronic EQ, etc.) you will also receive (as a benefit or detriment, depends on the room & listening position) increasing amounts of lumpy low-end response as there is much more interaction with the rooms boundaries which result in standing waves, which are areas of pressure build-up (increased dB), and other areas where the waves null, or cancel each other (decreased dB). If youre lucky, some of these very low standing wave frequencies might just happen to fall on the same frequencies as musical tones, at your listening position, in which case this would bring the level up somewhat, giving a more apparent flat response in the deep & sub-bass frequencies. The down side is that there will also be cancellation, somewhere in the room, at that & other frequencies. This is one of the reasons broadband absorption & diffusion are so important to good sound (the keyword here is broadband). If youre really resourceful and do your homework, you can use this to your advantage, to a certain extent. My room for instance, has a known resonance at 19Hz. Thats why the system response is down only 9dB at 20Hz. Its because of a room resonance, and Khorns being what they are, can take advantage of this, probably more so than other speakers (and please dont tell me how 9dB is a lot. Thats still better efficiency at that frequency than most, if not any domestic subwoofer with their increased direct radiator distortion, and quite phenomenal for a horn system). So in my situation, whats the trade-off to extend the bass response approximately a half octave so it sounds flat? Well, as I mentioned above, it seems like eight KSW-15 would do it. Want flat to 16Hz? Probably have to double the quantity again. So now were at sixteen of these just to reach another half octave. Hmmm. Even in my relatively large room, Im not so sure I want (or have room for) 16 of these things. As you can see, the requirements to produce low frequencies, at the same relative output, with the same low distortion, goes up substantially as the frequency goes down. A smaller listening room just complicates things further.

The similar things are at play with headphones. Headphones are EQd to a degree that would make most audiophiles freak. They are not measured flat in the same sense that we think about speakers (or rooms). There are no standard measurements. No standard references. Every manufacturer has their own way of measuring & specification. Its kind of the way things were a few decades ago with amplifiers before the FTC stepped in. About the only thing you could really trust was the manufacturers reputation. And ironically, the best ones had the worst specs, because they didnt try to exaggerate the performance under the best conditions. They told you how the unit would perform under the worst case scenarios and the most difficult conditions. Klipsch also falls into that kind of heritage. Are you going to trust the headphone manufacturer that boasts their headphones have a frequency response of 14Hz to 50KHz, or the one with a superior reputation that refrains from publishing such rubbish?

As far as subs & Khorns go, you will notice that even ones like the KSW-15 are voiced to match the Reference series. I have had many conversations with various Klipsch engineers over the years and not one of them has ever recommended any subwoofer that matches well with a Khorn. As I mentioned above, possibly if you have enough room, and care to put 16 or more KSW-15s in your room, possibly the distortion would be low enough & the acoustic output high enough at 16Hz to be of benefit as a match with Khorns. I did once know a fellow who had Khorns with a subwoofer that matched well. A horn loaded subwoofer no less. However, he built it out of concrete, and it extended the entire length of his house with the throat/driver at one end of the basement & the mouth opening into his listening room at the other end through the floor. Like I said..theres plenty of ways to accomplish this. But theres no free lunch here.

[sfogg]

"It means the frequency response begins to roll-off around that point because of the speakers interaction with the rooms boundaries."

The opposite is usually what occurs. You get 'room gain' in the deep bass which increases as frequency decreases down to a certain point.

http://www.adireaudio.com/tech_papers/enclosure.htm

or many of the pages from:

http://search.yahoo.com/search?p=%22room+gain%22&ei=UTF-8&n=20&fl=0&xargs=0&fr=fp-top&b=1

Of course you will also get large peaks and valleys at specific points based on the room dimensions.

You can use 'Visual Ears' to model the gain your room would have in the low bass.

http://www.kbacoustics.com/visualears/index.html

Finally you can take your subwoofer outside away from walls and measure its low end response. Bring it back in your room and measure it again using the same tones and amount of power into it.

Shawn

[formica]

As a side note... the KSW is not well respected (even here) for accurate bass reproduction and extension... and is definitely not a good match to your K-horns. I'm not even sure the RSW series will extend low enough to be a real benefit.

If you wanted to experiment, something along the lines of a Velo HGS18 or perhaps a bottom dweller from SVS (PB2 or B4?) would make a better/bigger audible difference.

[artto]

formica.....in all honesty, I have yet to hear subwoofer that I have any respect for. Even that huge concrete horn that my long past away friend built had its own set of problems & limitations.

[artto]

Room boundaries cause low frequency pressure zones (standing waves) that increase the apparent amount of bass we perceive in our rooms, depending on our location within the room (not uniformly throughout the room as seems to be the perception around here). It also, unfortunately, more often, causes cancellation of those same frequencies at & near the actual/usual listening position. Thats why its important to do an analysis of room modes before building or choosing a listening or recording space.

Shawn..you say You get 'room gain' in the deep bass which increases as frequency decreases down to a certain point. And what is that certain point? Guess what. Its the cut-off frequency.

In regards to the Audire Audio link you posted, I have to wonder how much the person who wrote that actually knows, or even more important, understands, about acoustics (no wonder he/she didnt even take credit for authoring it). Whats their definition of an average sized room? (no mention of room proportions here) Id also love to see how they arrived at the idea that this 9dB of boost at 20Hz is flat for a full octave above that. And, how apparently this occurs in all average sized rooms. The low frequency room modes can easily be calculated for simple rooms. Possibly you or your pal at Audire Audio can show us all what kind of average sized room (whatever that is) has a 9dB of bass boost at 20Hz & is flat up to 40Hz, that is uniform throughout the room. Its not just the room size. Its also the room proportions and angles to contribute to this at the most basic level. So as far as Im concerned, without proper documentation, I have to regard the Audire Audio piece in the BS category. Primarily spun to sell the design concept of their speakers. Too bad they didnt start at the beginning.

As far as the other link to yahoo, it points to a some threads that contain posts on Audio Asylum which are also frequented by a lot of half-baked posers who truly believe they know what they are talking about based on their own theories derived from their own petty opinions. Klaus, for instance (posted in that thread) states that the lowest frequency mode for a 9'x12' room another poster was asking about is 47 Hz. Well I'd sure like to know how Klaus arrived at that. There was no height specified. I guess all rooms throughout the world are 8' high because that's what Klaus choose (assumed) without even asking, which IMO shows how inept this guy is. I had to give Klaus a spank a few weeks ago, for his half-baked, partially thought out ideas which demonstrated a total lack of understanding of sound in general, & music in particular. In following the threads in that link, I really have to laugh. So many start out with the right idea, & then totally go off-the-wall in their opinions of how to apply it.

As far KB Acoustics goes, I guess I have to disagree once again. First of all, this is their dumb statement: There is no substitute for correct speaker placement and nothing, including an equalizer, can properly remove the problems of incorrect placement. WRONG. They have it all wrong. That is what comes AFTER, you get the room right. Let me re-phase their statement: There is no substitute for getting the room & its acoustics right. Speaker placement and nothing, including an equalizer, can properly remove the problems associated with inappropriate room size, poor room proportions and improper or lack of proper acoustical treatment.

RE: Visual Ears: In KB Acoustics words Visual Ears, is an easy to use computer program that, through mathematical simulation, will help you find a "listening sweet spot" which minimizes the effects of standing waves (20-200Hz) and boundary reflections (20-500Hz).

This is a program used for determining the best listening location & speaker placement in less than ideal simple rooms, not for determining anything to do with the rooms actual acoustic properties in the first place. I must say, this is very much like putting the horse before the cart.

[Q-Man]

I can only comment on what I have. My Klipschorns

are strong down to 35 maybe 30Hz. I have my Sunfire Signature subwoofer dialed in at 35 to 40Hz. I'm not saying that it's the best subwoofer out there, but it's not bad eather. I'll turn it on and off at times to hear the difference. You never know that it's on excempt when you turn it off. Then you easily hear what your missing without it. I think it blens well, but then I would rather have anything reproducing sound below

30Hz then nothing at all. I would love to have a horn loaded sub, but the last time I tried to design one on paper it got a little over my head. Maybe I'll try it again someday. Meanwhile I'm looking into the SVS B4 plus.

[D-MAN]

There is quite a difference in coupling a very small diaphram with a very small excursion through a very small distance (the ear canal) and the propagation of the same low frequency wave at a hearable volume from a distance of several feet through the atmosphere in a larger enclosed space, which is therefore subject to diffractions and reflections and subsequent modal cancelations due to room boundaries. That is why the room needs to be at least a certain size to reproduce usable low frequencies.