After some 50 years working on the problem, I am just as convinced that there isn't another option.
I'll be doing some experiments soon, comparing multisub to dipole and cardoid. I'll be sure to document it well.
Earl, would you tell us about your research concerning monopoles, dipoles and cardioids in small rooms?
35 degrees narrower on the 6dB point is my read- that's pretty far from nearly the same. I don't like throwing away efficiency but to knock a 200 degree lobe down to 130, eventually crossing to 90, is nothing to sneeze at.
The NS-15 is 120 degrees at 500 Hz with full monopole efficiency, so I don't see the advantage except for cabinet size. But in my systems the cabinet size is dictated by the waveguide not the woofer so smaller is not an advantage for me. I'd much rather have pristine waveguide performance than anything else.
I have never denied that the technique works. I deny that there is any valid data to say that it is an audible improvement in a small room. In a large room no contest - directivity down to 100 Hz would be an advantage.
In 1981 I published my PhD thesis on the LF sound field in small rooms using the FEM. From this I learned how source placement and modal distribution were the dominate features and that room shape played almost no part (apart from the fact that it does effect modal distribution, but no "general rules" for shape were apparent). By using various statistical methods I noted that the best one could ever do in a room was to have sources at multiple locations and that once one did this the statistics were basically independent of the specific source locations.
Back in the 90's I published a AES paper using a room simulation where I used the same set of statistics from my PhD to look at monopoles, dipoles and cardioids in various locations in the same room. For a given location one or the other source might be better, but no source was better in all locations and all sources at there best locations were comparable. This is why I say that I have no preference for source type - in general it simply does not matter. Monopoles always gave the most output but not always the smoothest response.
In unpublished work I have looked at source numbers and locations using EQ and find that with EQ one can achieve a comparable result independent of the source type and location as long as three or more sources are used spread around the room. The software to do this is actually free to all on my web site, although that version does not have dipole or cardioids because, as I said, I don't see that it matters. It would be trivial to implement dipoles and cardioids, and I might do that someday, but my interest level in such is pretty low.
I have done many rooms using my multi sub technique and in every case I am able to achieve a remarkable measured performance (this is documented in the presentation on my web site.) I'll leave the superfluous subjective claims to those who believe in that stuff, but suffice it to say, no one has ever changed my setups because they didn't like them. I know of no one who has used multiple subs that will ever go back. It is simply the right thing to do and I don't care if you use dipoles or cardioids or monopoles - although monopoles will always yield the highest output.
Ah, except that I explicitly replied to your comparative statement, that the two graphs were "nearly the same" at 500Hz. The merit of the approach is certainly debatable, but with all due respect, the comparative statement you made doesn't hold water.
Thanks Earl,
FEM... Did your analysis focus on the steady-state response only, or did you include the relative level of the direct sound? Subjective though it might be, a dipole sounds quite different in the bass to me than a monopole or multisub does. Equalization eliminates a lot of the differences, yet in my (uncontrolled) experience a dipole still sounds different. I know you tend to immediately dismiss most non-blind listening tests, but please bear with me for now. Assuming my observation is correct, I assume it must be because of a different direct to reflected sound ratio. What do you think?
Mind you, I question my own observations all the time. But the observation that a dipole sounds different than a monopole, even if equalized, has stood the test of time. I think the steady-state response tells a large part of the story, but not the whole story.
I'd really like to know what you think.
FEM... Did your analysis focus on the steady-state response only, or did you include the relative level of the direct sound? Subjective though it might be, a dipole sounds quite different in the bass to me than a monopole or multisub does. Equalization eliminates a lot of the differences, yet in my (uncontrolled) experience a dipole still sounds different. I know you tend to immediately dismiss most non-blind listening tests, but please bear with me for now. Assuming my observation is correct, I assume it must be because of a different direct to reflected sound ratio. What do you think?
Mind you, I question my own observations all the time. But the observation that a dipole sounds different than a monopole, even if equalized, has stood the test of time. I think the steady-state response tells a large part of the story, but not the whole story.
I'd really like to know what you think.
What do I think? I think that you misunderstand how sound perception works in a small room at LF. There is only the steady state, there is no "direct sound" nor is there a "near field" of any appreciable level. The sound reaches steady state throughout the entire room long before the ear can even detect the frequency or presence of that sound.
So while you believe that you hear a difference between monopoles and dipoles it is certainly not due to what you believe it is.
Comparing a dipole to a monopole with both sources at the same location is no real test at all. They excite the room completely differently so of course they will sound different. How then does one even compare LF sources? The only thing that I know has any validity is the steady state sound field. There is nothing else. Get that the same for any two LF sources and they will have to sound the same. If you still hear a difference then its something higher in frequency than the modal region or you are hearing something that is not there.
When I heard Orions the only thing about them that I liked was the bass. It was very good. I would describe it as on-par with my multiple sub setup, but certainly not better. Admittedly the Orions owner did nothing special to get that sound while I did extensive testing and setup. That says a lot about the quality of a dipole with minimum work. But my system could probably play 20 dB louder than the Orions without breaking a sweat. That was a big difference IMO.
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Sadly there are few individuals who have the skill, resources and willingness to integrate multisubs manually. That all consumer receivers manage bass in a wrong way doesn't help the situation. Apart from (discontinued?) JBL Bassq and SFM from the Synthesis line, there just isn't a plug-and-play solution available.
Concerning the optimal crossover frequency, are there any drawbacks to having it in about 300 Hz region? I'm thinking about the FAST concept and potentially it's pretty trivial to crossover a woofer and a small fullranger at this frequency, perhaps 1st order. I've seen some references to the rule that with 1st order crossovers drivers must play two octaves beyond the xo frequency, which is probably too stringent for a small 3 inch fullranger.
I remember clearly when Orion+ was landed in our living room for two weeks. Bass was fat, slow and quite unintegrated at upper bass due to front wall and corner reflections, which dominate reflected power in our house. Positioning was more careful than plug & play, and electrical setup according SL's instructions. Local diy-person described bass sound as “slack sh*t like dipole bass”. I silently agreed knowing that this was not final statement neither dipole nor Orion. Next step was to enter ASP circuit into spice and simulate better values to dipole EQ section. Original values seemed to be for free space (with ground) or glass room in CA. Balance and speed was much better after soldering new resistors on PCB. I don’t see much “easiness” in this case when user environment did not match with engineering environment.
At the same time super-cardioid is possible to move from big house to concrete bunker of 16m2 with zero adjustments, without substantial drawbacks in tonal balance, speed and accuracy - better than Orion in those four setups what I have heard. I would call it as smart acoustic design still realizing that there are some trade offs. Why would I bother to tune multiple subs even for my best friend if good pure stereo reproduction is possible by plug & play.
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Knowing you did research on this and you have a vast knowledge of the matter, I would appreciate some relevant and trustworthy references for the above.
From what I've been able to quickly lookup:
- the ear integration time at low frequencies is reported anywhere between 10-ms (here: Ear integration time and | Comp.DSP | DSPRelated.com ) and 30-50 ms (depending on the circumstances). Granted, I was not able to find a value specifically for the range below 100Hz.
- a cycle takes 20 ms at 100Hz and 40ms at 50Hz
- but reaching steady state at ~100Hz seems to take significantly longer than that. Intuitively, the sound would need to travel many times the dimensions of the room, which means a few hundred ms. This analysis by Linkwitz reports 90% steady-state after 224 ms: Dipole vs Monopole woofer
That would mean:
- either the ear should be actually able to perceive low frequency sound long before steady-state is reached.
- or I am missing something.
I do not agree with the 224 ms number for steady state. It would be many times lower than that.
The ear would take at least several period of a sound to accurately detect it. If you look at the gamma-tone filter representations of the ear, which are considered the most accurate they will estimate about 60 ms. for a 70 Hz tone and something like 50 ms. for a 100 Hz. tone. The longest dimension is in my room, for example, 14 feet so a complete trip of sound would take about 28 ms. I would estimate that steady state would be reached some time before the signal was clearly detected at 70 Hz and would probably just reach steady state at 100 - 150 Hz. We are not going to hear the sound "reflecting" around the room at frequencies below 150 - 200 Hz.
The gamma tone filter impulse responses are shown in a graph in the presentation that I showed on my website. They only go down to about 200 Hz, but I wrote a program to simulate these filters which showed a 60 ms. time for a 70 Hz. tone.
Reviewing SL paper, I find him to be rather conservative in his approach and his model is very simple, but I could accept a time of 150 ms. for steady state in his room at 113 Hz as that would be pretty consistent with what I am saying. Stan is always trying to prove his point about dipoles and sometimes he stretches things a bit. Maybe we all do, but I do not claim a preference for any specific type of sub so I am not trying to prove one better than another.
The ear would take at least several period of a sound to accurately detect it. If you look at the gamma-tone filter representations of the ear, which are considered the most accurate they will estimate about 60 ms. for a 70 Hz tone and something like 50 ms. for a 100 Hz. tone. The longest dimension is in my room, for example, 14 feet so a complete trip of sound would take about 28 ms. I would estimate that steady state would be reached some time before the signal was clearly detected at 70 Hz and would probably just reach steady state at 100 - 150 Hz. We are not going to hear the sound "reflecting" around the room at frequencies below 150 - 200 Hz.
The gamma tone filter impulse responses are shown in a graph in the presentation that I showed on my website. They only go down to about 200 Hz, but I wrote a program to simulate these filters which showed a 60 ms. time for a 70 Hz. tone.
Reviewing SL paper, I find him to be rather conservative in his approach and his model is very simple, but I could accept a time of 150 ms. for steady state in his room at 113 Hz as that would be pretty consistent with what I am saying. Stan is always trying to prove his point about dipoles and sometimes he stretches things a bit. Maybe we all do, but I do not claim a preference for any specific type of sub so I am not trying to prove one better than another.
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There shouldn't be any numerical or graphical data in my previous post. Is forum software making something funny in there? I can write some random numbers 819275936 and link an image if that helps you to read the text.
P.S. If someone else is interested in previous image without data, there is quite old unsmoothed FR measurement of speaker with super-cardioid bass up to 400 Hz.
nice to see this steered back on topic
I have had really nice results crossing at 250 Hz, but that was from a horn loaded mid-bass to a "fullrange" (actually I call it a wide-band driver) Tang Band 1772, also horn loaded, up to 3500hz where a ribbon tweeter took over.
Much to my delight, for all intents and purposes most of the image seemed to eminate from the front-horn loaded Tang-Band. From my experience, the only way to get a wide-band driver, such as the TB W8-1772 is to front horn load the thing. Otherwise the low mids seem anemic. But, of course, that's also my very personal bias. 250-3500hz covers most of the critical mid-range.
I have had really nice results crossing at 250 Hz, but that was from a horn loaded mid-bass to a "fullrange" (actually I call it a wide-band driver) Tang Band 1772, also horn loaded, up to 3500hz where a ribbon tweeter took over.
Much to my delight, for all intents and purposes most of the image seemed to eminate from the front-horn loaded Tang-Band. From my experience, the only way to get a wide-band driver, such as the TB W8-1772 is to front horn load the thing. Otherwise the low mids seem anemic. But, of course, that's also my very personal bias. 250-3500hz covers most of the critical mid-range.
So is that link "fat, slow and quite unintegrated at upper bass" or "without substantial drawbacks in tonal balance, speed and accuracy"? Just so that I know.
This looks pretty good. Is this measurement of your KS-1804 cardioid loudspeaker ?
If it is, it looks impressive for unsmoothed inroom response. Doesn't get much better than that.
You might want to read everything that is written in measurements/posts posted before writing any sarcastic comments. That would be polite.
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