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I think it's an issue only because people have different goals. Some people want to recreate the recording as accurately as possible, to reproduce it without any additions or subtractions from the amplifier, the driver, the box or the room. Often this requires the careful placement of everything in the room, including the listener. I believe that these listeners want to enjoy the original music as if they were present at the recording rather than in their own home.
Other people want to create a listening experience that is part of their surroundings, one that allows the sound to interact with their listening space because they find it sounds more natural to them. Instead of trying to transport themselves to the recording venue they want to bring the recording into their listening space and they accept that this will be different.
At the end, as was pointed out before, we are at the mercy of the quality and the decisions made by the producer and his/her staff.
I am over-simplifying and some people will object that I'm trying to categorize them. But the point is that we will disagree with each other on points of implementation where we have different goals and it has nothing to do with audiophoolia.
The topic of this thread is questioning the relevance of, and if necessary, eliminating box colourations (including bad effects that the box has on the driver), not the room.
Other people want to create a listening experience that is part of their surroundings, one that allows the sound to interact with their listening space because they find it sounds more natural to them. Instead of trying to transport themselves to the recording venue they want to bring the recording into their listening space and they accept that this will be different.
At the end, as was pointed out before, we are at the mercy of the quality and the decisions made by the producer and his/her staff.
I am over-simplifying and some people will object that I'm trying to categorize them. But the point is that we will disagree with each other on points of implementation where we have different goals and it has nothing to do with audiophoolia.
The topic of this thread is questioning the relevance of, and if necessary, eliminating box colourations (including bad effects that the box has on the driver), not the room.
People remove the back of their boxes (or the box completely) and think, they have started to eliminate "box colorations". What they have mainly done in that case, is changing the interaction of the box with their room. I wasn't sure that everybody was aware of this.
Rudolf
If the assumption is that a dipole hovers around its 4.8 d.i., then there are plenty of monopole speakers that are more directional. Nearly every horn speakers ends up gently climbing to a d.i. of 10 dB say, +-2dB. A dipole can climb in directivity too, so in the end their only significant differences are in the first Octaves.
I do agree that a dipole that is carefully aimed can knock out a few of the first reflection, but I doubt that most users toe them in to the degree required for that.
And...
And in addition they have very significantly altered the amount of time it takes for reflections to arise, and probably the amplitude as well. Shifting reflections from the early arrival window to a much later arrival time makes a very large difference on how our hearing system (both conscious and subliminal) interprets the information.
Although much information has been given about the Haas precedence effect, there are those who suspect that the time-smear caused by early reflections is actually a lot more audible than previously thought, especially where the subliminal is concerned.
There is some suspicion that our "instant localization" form of hearing, being more connected with survival instinct than with the pleasure centers in the brain, runs in a parallel circuit.
While the offending time-smear may not be all that noticeable on surface-level consciousness, it IS detected by the subliminal system. I've done some experimenting with subjects using GSR testing (yes, in lieu of EEG's, the correlation is very good however) and found that we are VERY sensitive to the acoustic equivalent of "ghosting" caused by early reflections. (Don't ask for white papers, none available yet, I may some day get funding to conduct a formal peer-reviewed study... human testing is very time-consuming. And boring. I make speakers, and am not vying for a full-time research job unless it pays really well.)
However, this does not stop me from concluding that we should do as much as we can to minimize early reflections from the drivers, front AND back, and that these reflections may well be a big part of what is perceived as "box-sound". And that the front vs back emissions of the speaker box or baffle need to be extremely coherent with each other front back and front to side, meaning FR coherent but also time-coherent.
Why is the relative degree of coherence between the front and back so important? Looking at direct-arrival signal and the signal that goes on to bounce off the walls: the more these signals look like each other in time and frequency (BEFORE they bounce around), and the later the reflections occur, the easier it seems to be for our subliminal system to interpret them as "Oh, that's the room sound" and essentially disregard the reflections.
Conversely, when there is a substantial lack of coherence, this confuses the localization system.
With regard to the reflections issue, in order of suitability, I've found that the speakers that tend to work "best" in a regular room appear to be:
1) Fully time-coherent OB open baffle with near-constant directivity at ALL frequencies,
2) Fully time-coherent Omni-directionals (which by definition have constant directivity!)
3) Fully time-coherent "constant directivity" front-firing speakers.
Note the emphasis on full time-coherence, that seems to be a very important part to satisfy the subliminal localization mechanisms. (This why we use a DEQX in our big reference system, to get full time-coherence in the entire omni-directional radiation pattern).
So then, if we view the signal reflection issue from the perspective of early vs late reflections arising from a "little" box, i.e. a regular enclosure or a "big" box, i.e. the listening room, it becomes a little more difficult to say that these are entirely separate issues. It seems better to include the room as part of the system, and not just narrowly focus on the enclosure.
And it would appear that if we can have the reflection happen later, and be more coherent with the direct arrival signal, even if it is quite large in amplitude, then the overall combination is heard as "better" by the subliminal - and clearly for some of us, it is also heard as "better" by the conscious level hearing.
When the internal reflections are almost completely dissipated as they are in our omni-system, or in our sealed box CD ("constant directivity") comparison speakers, then the subjective quality battle between the OB and the omni starts looking very even, except the OB sounds more neutral (read: "better") in most rooms. Note: In very good rooms, there is almost no subjective difference!
In a regular un-treated room the Time-coherent, nearly constant directivity OB wins in almost every case. Both OB and omni seem to outperform the CD box (mainly because the CD box is NOT in fact CD, it transitions to a wider beam below 700 Hz and looks like an omni below 300Hz).
In sum, we may not be able to so easily isolate the notion of "box colorations" to just the boxes. The directivity of the box and how it interacts with the room is a major "box coloration" issue, and so is the issue of early vs late reflections, and so is the time-coherence, and so is the uniformity of acoustic power that goes into the room, and so is .... the list goes on... Pick your favorite!
May Peace Be with Us
Yes!
And in addition they have very significantly altered the amount of time it takes for reflections to arise, and probably the amplitude as well. Shifting reflections from the early arrival window to a much later arrival time makes a very large difference on how our hearing system (both conscious and subliminal) interprets the information.
Although much information has been given about the Haas precedence effect, there are those who suspect that the time-smear caused by early reflections is actually a lot more audible than previously thought, especially where the subliminal is concerned.
There is some suspicion that our "instant localization" form of hearing, being more connected with survival instinct than with the pleasure centers in the brain, runs in a parallel circuit.
While the offending time-smear may not be all that noticeable on surface-level consciousness, it IS detected by the subliminal system. I've done some experimenting with subjects using GSR testing (yes, in lieu of EEG's, the correlation is very good however) and found that we are VERY sensitive to the acoustic equivalent of "ghosting" caused by early reflections. (Don't ask for white papers, none available yet, I may some day get funding to conduct a formal peer-reviewed study... human testing is very time-consuming. And boring. I make speakers, and am not vying for a full-time research job unless it pays really well.)
However, this does not stop me from concluding that we should do as much as we can to minimize early reflections from the drivers, front AND back, and that these reflections may well be a big part of what is perceived as "box-sound". And that the front vs back emissions of the speaker box or baffle need to be extremely coherent with each other front back and front to side, meaning FR coherent but also time-coherent.
Why is the relative degree of coherence between the front and back so important? Looking at direct-arrival signal and the signal that goes on to bounce off the walls: the more these signals look like each other in time and frequency (BEFORE they bounce around), and the later the reflections occur, the easier it seems to be for our subliminal system to interpret them as "Oh, that's the room sound" and essentially disregard the reflections.
Conversely, when there is a substantial lack of coherence, this confuses the localization system.
With regard to the reflections issue, in order of suitability, I've found that the speakers that tend to work "best" in a regular room appear to be:
1) Fully time-coherent OB open baffle with near-constant directivity at ALL frequencies,
2) Fully time-coherent Omni-directionals (which by definition have constant directivity!)
3) Fully time-coherent "constant directivity" front-firing speakers.
Note the emphasis on full time-coherence, that seems to be a very important part to satisfy the subliminal localization mechanisms. (This why we use a DEQX in our big reference system, to get full time-coherence in the entire omni-directional radiation pattern).
So then, if we view the signal reflection issue from the perspective of early vs late reflections arising from a "little" box, i.e. a regular enclosure or a "big" box, i.e. the listening room, it becomes a little more difficult to say that these are entirely separate issues. It seems better to include the room as part of the system, and not just narrowly focus on the enclosure.
And it would appear that if we can have the reflection happen later, and be more coherent with the direct arrival signal, even if it is quite large in amplitude, then the overall combination is heard as "better" by the subliminal - and clearly for some of us, it is also heard as "better" by the conscious level hearing.
When the internal reflections are almost completely dissipated as they are in our omni-system, or in our sealed box CD ("constant directivity") comparison speakers, then the subjective quality battle between the OB and the omni starts looking very even, except the OB sounds more neutral (read: "better") in most rooms. Note: In very good rooms, there is almost no subjective difference!
In a regular un-treated room the Time-coherent, nearly constant directivity OB wins in almost every case. Both OB and omni seem to outperform the CD box (mainly because the CD box is NOT in fact CD, it transitions to a wider beam below 700 Hz and looks like an omni below 300Hz).
In sum, we may not be able to so easily isolate the notion of "box colorations" to just the boxes. The directivity of the box and how it interacts with the room is a major "box coloration" issue, and so is the issue of early vs late reflections, and so is the time-coherence, and so is the uniformity of acoustic power that goes into the room, and so is .... the list goes on... Pick your favorite!
May Peace Be with Us
People are scared of toe-in, and I really dont know why. I'm a tough guy however, so its 45 degrees toe-in for me. 😀
Yes, AND.... those first few octaves ARE very significant. It's the region where a good near CD type OB usually "wins" in the comparisons.
As for your second point, if users aren't going to try and optimize their system, then why bother with trying to make a really good speaker? A Bose wave-radio will do fine for lots of people!
???
Hmm, I find I like 30 a little better in untreated rooms. But your room is really the bomb, so maybe 45 is better for the really good rooms.
Yeah, I know, adjusting speakers position and angles is SUCH a chore, I think I'll just go listen to my ipod with the provided headphones...:😱
Hmm, I find I like 30 a little better in untreated rooms. But your room is really the bomb, so maybe 45 is better for the really good rooms.
Yeah, I know, adjusting speakers position and angles is SUCH a chore, I think I'll just go listen to my ipod with the provided headphones...:😱
Headphones?
Yeah, headphones...that's the answer....
No, but then I start hearing voices in my head... I really do........ and I swear I'm not crazy!...........and neither am I...........
Yeah, headphones...that's the answer....
No, but then I start hearing voices in my head... I really do........ and I swear I'm not crazy!...........and neither am I...........
I'm not doubting that but I receive the same effect and satisfaction when I try this in the middle of my lawn where reflections are a long enough delay to be called an echo, so I have a feeling there's more to it than what you have stated.
Even in the middle of your green you will get the dipole roll off, a changed directivity and the quarter wavelength resonance of the box frame, if you remove the back. I don't say that those are the only effects of the removed back. There could well be real box effects too. We just need to be aware that what we hear with the change is a mix of "less boxiness" and "dipolisation" at the same time.
Rudolf
Hey Cal, that's actually a VERY good point. Reminds me of some things that happened to me.
When you remove the room from the equation like this and still hear a big difference, this may add to the idea that there is something about conventional boxes that is bothersome, at least for some of us.
And it may not only be in the build quality of such: I built dozens of really well-braced and damped rectangular enclosures and they still sounded boxy, even when with an accelerometer taped to the sides there was pretty much no resonance to be seen at full pre-amp gain. The boxiness did reduce a LOT when I started adding dividing panels to create non-parallel surfaces, pointing to resonances as the culprits. Or maybe it was just the early reflections gumming things up.
But it wasn't until I was able to build a special internal structure that really randomized the back-wave, wrapped with absorbent material that I was able to reduce the boxy colorations to inaudible when outdoors.
Emboldened by this, I then "perfected" an enclosure using double walls (an inside tube trapped inside a bigger tubular enclosure) that so completely reduced transmitted sound at the outer wall that even with a stethoscope you couldn't detect any noticeable sound from it when playing at full tilt, 120dB+ at 1m. I was pretty happy with that achievement, and built my reference system around it. Outdoors there was no noticeable "boxiness" whatsoever. No chestiness either, just an astonishingly natural midbass and midrange
Imagine my surprise and disappointment to then find that said "un-boxy" sounding enclosures, when brought back into a 27 x 12 room with a 9ft ceiling suddenly had a VERY chesty sound from a narrow-band room resonance issue at 141Hz and another near 180Hz... required a whole lot of fine-tuning with the eq'ing to tame it, and unable to do it just by the measured numbers. A +10.6db peak at 141Hz would need about -10.6dB eq with the same Q to cancel it out, right?..... well....Nope! ..... measured perfect, but that sounded too flat and dead! Similar with the 180Hz peak. So after many, many, many trial and error runs, ended up with about -6.5dB at 1/7th octave to get it to sound right. But I eventually nailed it and the reference system really sounds neutral and kick-ss good in this room (finally!)
Conversely, imagine how pleased I was when after adjusting the new OB model outdoors, I brought it in to the same room, cringing to think about the chesty room resonances, then discovering... no audible chestiness at all. No need for any room eq at all in this rather bad room.
Similar experience in a bunch of other "regular" untreated rooms. With proper "toe-in by ear", this OB does not have any of these colorations which sound boxy, at least in any one of the 20+ rooms we've tried it in. The band between 100 and 300 Hz remains mostly unaffected in most rooms, probably because it's only affecting the longitudinal modes and those main modes are most often happening at frequencies below that band.
Am I saying that OB systems in general will have similar attributes in most rooms? Hmm. If the dimensions are similar, I'd be hard pressed to argue against the notion.
How did you test that? Did you listen to one and the same speaker with and without the box with tightly matched level and frequency response?
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Markus, In Cal's case, if I am correct, he is comparing his speaker with and without an open space behind his mid-driver. With an open back behind his mid-driver there may well be fewer resonances within that cavity and fewer reflections of sound back through the cone. If I interpreted the photographs he posted properly, the other drivers are in closed spaces in his enclosure and are not affected so the level and FR remains the same for them - only the mid driver is affected by the change. Look at post 7 at the 3rd and 4th images. Of course, there may be some other changes going on - such as a shift in the XO points ?
Bigun has it correct. No changes in the XO, no controlled testing, just music. Similar effect no matter the enviro. And yes, I think it's time to remind, that I am dealing with the mids only, I have not found a way to do OB bass that appeals to me.
Hey Cal, perhaps you've answered this before, but where in the range are you crossing the mids to the bass?
I haven't tried that but I suspect it would work pretty well if the layer is thick enough. Not only does clay have good internal dampening but you are also adding "limp mass" which is an ideal issolation property.
The key with all damping layers is that they need to be fairly substantial to compete with the mechanical impedance of the stiff cabinet walls. As the cabinet becomes more rigid the damping layer required must become heavier. That is why studies show that damping applied to thin walls can do a better total job than the same damping on a thick walled cabinet.
David S.
The key with all damping layers is that they need to be fairly substantial to compete with the mechanical impedance of the stiff cabinet walls. As the cabinet becomes more rigid the damping layer required must become heavier. That is why studies show that damping applied to thin walls can do a better total job than the same damping on a thick walled cabinet.
David S.