Directivity in any region matters I would think, why would having directivity below the Schroeder frequency be futile? The direct vs indirect energy relationship exist there as well doesn't it? Higher directivity is going to create less indirect energy, what am I missing.
_ am trying to grasp this concept as well....the idea that the adjoining woofer needs to "keep up" with the horn.....if my CD+horn is 100db sensitivity and I turn down the gain to match the levels of a 92db 15" below it.....the Horn is stilll....100db....the (benefits of) mechanical sensitivity of a driver can not be offset by turning the gain down...makes no sense its just a volume knob....now if there's something going on with passive crossovers....well....its vintage anyway (joking =). The underlying theme (to me) is that High sensitivity derived mechanically, has an advantage in SQ that a much lower sensitivity driver cannot match...but leave it at that....if I can suck the life out of a horn by dialing gain back I should be able to pump life into low sensitivity woofer and all a sudden all is well....and thats not the case. Its probably really the efficiency that is to blame.
Sensitivity increased while efficiency remains the same, you get more excursion and spl per signal
Efficiency increased while sensitivity remains the same, you decrease excursion per spl/signal
Surely efficiency is the catalyst for the increased SQ.
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We call it the Schroeder frequency but there's actually the ray acoustic region, followed by a sparse modal region, followed by the modal region. Schroeder is within the sparse modal region.
Most speakers in the multi-way forum are designed to operate in the ray acoustic region. Few speakers in the multi-way forum are designed to operate in the sparse modal region. No speakers in the multi-way forum are designed to operate in the modal region. Modal region speakers are in the subwoofer forum.
john k... summarized points from a research paper on designing speakers to operate in the sparse modal and modal region here. (I'm really grateful to john k... for posting that information because it used to befuddle me.) In Pursuit of a 20-20k Dipole Loudspeaker
When you're in the modal region you have a physics problem and a psychoacoustic problem. The physics problem is the sound waves are so long they get squashed by the room boundaries. The psychoacoustic problem is your brain needs to hear the low frequency long enough to recognize what it's hearing. By the time your ear has been exposed to the LF sound long enough for your brain to recognize it the sound wave has bounced around the room many times and has hit your ear from many different angles. Further, we have difficulty localizing low frequency signals even when we are in a large room or an open field. If you can't localize a low frequency in an open field you're definitely not going to localize it in a small room where it's bouncing all over the place.
As an example, if you wanted to build a horn to control a 70Hz frequency with a 90 degree angle it would need to be 15 feet wide and 7 feet deep. In the end it wouldn't perform any better than an 8" woofer in a small sealed box. However, with an 8" woofer you can locate several of them around your room in a multi-sub strategy as Earl Geddes and Todd Welti suggest.
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Exactly. All the very best systems use bass horn cabinets, and thats why I even choosed to do so. Without a bass horn cabinet, dynamics of the lows can't compete with the horn dynamics.
hottattoo,
Those are not my conclusions, but conventionally established relationships between terms that can be either direct (positive) or inverse (negative). They have general validity and cannot be practically circumvented.
Yes, flux density referring to the internal field B, which is inversely related to magnetizing field intensity H. Yes, control includes damping.
So, the stronger the electric field, the more control of the magnetic field and the more control of the diaphragm. Efficient systems display a comparably weak electric field and high magnetizing field intensity (a bad combination).
In the end personal preference is the only thing that matters, should weigh more than cold facts. There is no point in being dishonest with ourselves.
Those are not my conclusions, but conventionally established relationships between terms that can be either direct (positive) or inverse (negative). They have general validity and cannot be practically circumvented.
Yes, flux density referring to the internal field B, which is inversely related to magnetizing field intensity H. Yes, control includes damping.
So, the stronger the electric field, the more control of the magnetic field and the more control of the diaphragm. Efficient systems display a comparably weak electric field and high magnetizing field intensity (a bad combination).
In the end personal preference is the only thing that matters, should weigh more than cold facts. There is no point in being dishonest with ourselves.
[QUOTEYes, flux density referring to the internal field....... high magnetizing field intensity (a bad combination).][/QUOTE]
I can't follow you here. Flux density is the product of field strength H and permeability. So B is proportional to H. And I don't see where your electric field is coming from. We have electric current in a conductor (voice coil) where the difference in potential between both ends of the conductor in the magnetic gap is benign and therefore negligible.
High efficiency systems DO have high control over cone motion but sometimes at the cost of reduced output at their fundamental resonance.
When it comes to the advantages of field-coil drivers I can see two points:
The magnetic path is electrically conductive and therefore resists against shifting of field lines as a function of the forces involved which in turn reduces Barkhausen noise and nonlinear distortion. A property that it shares with Alnico magnets. The second advantage it does also share with Alnico but it can go much farther: The magnetic path can be driven into very high saturation which makes it very "stiff" and therefore further helps reducing nonlinear distortion.
Regards
Charles
I can't follow you here. Flux density is the product of field strength H and permeability. So B is proportional to H. And I don't see where your electric field is coming from. We have electric current in a conductor (voice coil) where the difference in potential between both ends of the conductor in the magnetic gap is benign and therefore negligible.
High efficiency systems DO have high control over cone motion but sometimes at the cost of reduced output at their fundamental resonance.
When it comes to the advantages of field-coil drivers I can see two points:
The magnetic path is electrically conductive and therefore resists against shifting of field lines as a function of the forces involved which in turn reduces Barkhausen noise and nonlinear distortion. A property that it shares with Alnico magnets. The second advantage it does also share with Alnico but it can go much farther: The magnetic path can be driven into very high saturation which makes it very "stiff" and therefore further helps reducing nonlinear distortion.
Regards
Charles
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Individual preferences exist and cold facts exist too. [If we discard the assumption of mystical properties] One may individually prefer certain facts; he may know them, want to know them, not want to know them, or even fantasize non-existent facts that he likes
.Hi Joe, thanks for sharing experiences.
My experiences with compression drivers although similar in achieving the excellent sound we desire, run a bit different with respect to implementation.
I've had great success with CD/horn combos used with both direct radiator mids and bass, and horn loaded mids and bass. Whether my system is all horn loaded top to bottom, or a hybrid, doesn't seem to matter. What does seem to matter is the degree of tuning excellence brought to whatever the setup.
All of my various CD/horn builds have been 4-way, and active 4-channel multi-amps.
Whether i need to attenuate the CD or not is a non issue.
There's no need to match sensitivity/efficiency between the 4 driver sections, other than for max spl and headroom.
Any attenuation is done in the floating point digital domain with sufficient resolution to ensure there are no gain structure/snr issues.
I can easily see however, that with passive xovers it's more important to match the multiple sections' acoustic outputs to keep from wasting power, as of course the driver sections have to padded down to the section with the lowest output. I guess the wasted power issue is also more acute when using a single amp to drive more sections.
Along with muti-amping, I use dsp for timings, with FIR implementations handling both linear phase xovers and minimum phase EQ's.
The digital timing allows the various sections' mouths to be physically aligned in the same vertical plane, and avoids the diffraction issues from having to stagger horn mouths in order to keep voice coils physically aligned. No horns playing over or around each other.
The use of FIR, imho, brings many advantages i won't dive into, other than to say linear phase xovers are an absolute joy to use....whatever the order.
I see you mention having used DEQX. I've been surprised by how many reports I've heard from users who were less than convinced with what they achieved with it.
That always puzzled me until i read the manual.
I think it would take quite a bit time and experience using it, to follow their implementation process to full fruition.
(It's my major issue with most products that introduce digital tuning, especially FIR file software generators.....they are too dang complicated to promote rather guaranteed success. but i digress....)
I feel blessed to have learned the manual implementation of FIR via rephase..... before moving on to more automated methods or structured processes.
Ime, the automated methods and structured process can easily do more harm than good, until their capabilities or lack of, are fully understood....(something I'm continually learning).
DEQX is a case in point...when you dissect its specs, it really doesn't have that much processing capability to implement its various filters .
Please don't get me wrong, they are great units, but I don't think they are fully capable of demonstrating what dsp using FIR implementations can do for SQ. just my 2c, fwiw...
I have to say that I am very much much impressed with the knowledge of some of the people who post here. This is what DIY is all about, people looking to pick an off the shelf item to use and enjoy and the people who can explain how and why these products work. Where would we be without the work and research of Harry Olsen, Ed Wente, Don Keele, Dr. Geddes, Dr. Bruce Edgar and many others. A "simple" thing like a compression driver, horns, waveguides turns out NOT to be so simple. I enjoy and learn every time I look at this topic. Many thanks to all those who post here !!!
The topic of "high resolution" has come up several times and is also somewhat complicated. I will try to explain my observations with my particular speaker system. Most of us know how the brain interprets sound is very complicated and still not fully understood so sound quality can be subjective on an individual basis.
Some posters here have noted that I use 3 drivers to cover 450hz. to 20k+. I could have easily done this with 2 drivers and have done so.. The 3 driver approach sounds much better, I believe, do to less driver stress. All of the drivers I use have powerful motors, beryllium diaphragms and are very efficient. There is one other parameter, diaphragm resonances, and where they fall at various frequencies. It is my contention that these spurious resonances will get in the way of perceived resolution. Beryllium pushes these resonances further up in frequency then aluminum or titanium thus making them less audible. Just my take.
Truextent Beryllium for Audio Domes, Cones and Assemblies
Joe
The topic of "high resolution" has come up several times and is also somewhat complicated. I will try to explain my observations with my particular speaker system. Most of us know how the brain interprets sound is very complicated and still not fully understood so sound quality can be subjective on an individual basis.
Some posters here have noted that I use 3 drivers to cover 450hz. to 20k+. I could have easily done this with 2 drivers and have done so.. The 3 driver approach sounds much better, I believe, do to less driver stress. All of the drivers I use have powerful motors, beryllium diaphragms and are very efficient. There is one other parameter, diaphragm resonances, and where they fall at various frequencies. It is my contention that these spurious resonances will get in the way of perceived resolution. Beryllium pushes these resonances further up in frequency then aluminum or titanium thus making them less audible. Just my take.
Truextent Beryllium for Audio Domes, Cones and Assemblies
Joe
Use the ripple tank simulator. Add a horn. Then wrap a small box around the horn, because that's your room relative to long low frequency wavelengths.
Ripple Tank Simulation
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Works for me; horns are decade [5 octave] reproducers at best, so at ~5.6 octaves based a typical 22 kHz upper limit, it ideally needs to be divided up based on even acoustic power distribution, especially since actual horn/box loading peters out at its effective upper mass corner, but normally stuck with whatever driver/horn combos is available.
GM
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For sure the room dominates, so truncated horns loading just enough to couple to the HF suffices, or in many cases, just use [multiple] H.E. [horn] drivers in a sealed or damped vented alignment depending on the desired efficiency/cutoff point.
GM
Omg thank you so much! someone posted this ripple simulator in my thread earlier this year and I haven't been able to find it buried within the pages...oh you one.
camplo,
most importantly, for low distortion, in any electrical interface (boundary conditions), the pressure difference must be small.
phase_accurate,
The quality aspects are not evident from that relationship. Higher magnetic intensity exacerbates the diseases mercilessly plaguing magnetism, such as random polarizations, misaligned magnetic moments, transitions at near resonance, saturation, hysteresis.
Magnetic fields cannot exist without electric fields and they cannot control themselves, it is done by electric fields presenting an opposing resistive force.
Electromagnetism is everywhere. It is also a prerequisite for life.
All this is incorrect.
¤
You won`t be able to show that higher energy implies lower distortion, which should defy common sense in the first place (but it does not).
most importantly, for low distortion, in any electrical interface (boundary conditions), the pressure difference must be small.
phase_accurate,
The quality aspects are not evident from that relationship. Higher magnetic intensity exacerbates the diseases mercilessly plaguing magnetism, such as random polarizations, misaligned magnetic moments, transitions at near resonance, saturation, hysteresis.
Magnetic fields cannot exist without electric fields and they cannot control themselves, it is done by electric fields presenting an opposing resistive force.
Electromagnetism is everywhere. It is also a prerequisite for life.
All this is incorrect.
¤
You won`t be able to show that higher energy implies lower distortion, which should defy common sense in the first place (but it does not).