Perhaps it's been said already, but it's apparent that compression drivers are (almost) exclusively associated with high directivity applications.
Even if one compares a direct radiator in a horn with a compression driver in a horn of similar directivity, the compression driver usually represents something closer to a point source over a greater bandwidth due to size.
I'd bet that systems of identical directivity (not practically possible) would blur the low-level listening comparisons greatly.
Assuming quality components and implementation, etc, I think directivity could be the driving factor more than actual driver type. Particularly at low-levels, Moving air is moving air.
-- mark
Even if one compares a direct radiator in a horn with a compression driver in a horn of similar directivity, the compression driver usually represents something closer to a point source over a greater bandwidth due to size.
I'd bet that systems of identical directivity (not practically possible) would blur the low-level listening comparisons greatly.
Assuming quality components and implementation, etc, I think directivity could be the driving factor more than actual driver type. Particularly at low-levels, Moving air is moving air.
-- mark
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I have been told the contrary by some people whom have used many horns, so I think it just boils down to the specifics of each design. Also explained in a book published by Focal Press, once horns are longer than 30 cm, you start to hear coloration of horns. The only way to be sure is to get all these different systems that claim to be dynamic all into one place and settle the issue.
Replay gain set for each composition will normalize this easy enough. Doubt your hearing is reduced enough to make the difference between the two of you. More like personal preference and a critical ear
That can't really be true since the waveguide cannot know what the source of a wave is. Only the shape of the waveform could be different, but then they can also be the same. A waveguide driven by a flat piston is exactly the same as one driven by a compression driver. A dome with a waveguide will be different, but not that much.
Yes but in the same book the author says the Kinoshita horn (derived from a TH4001, and more than 40cm deep) sounds nice and uncolored...
"Long horns = coloration" misconception
I am aware of the original research that arrived at this conclusion (Newell and Holland), but I still think that this is essentially an unsupported claim - or, rather: a case where the observed colorations in the case of longer horns were coincidental, rather than the result of horn length itself.
I.e. there may have been other reasons (horn wall vibrations, diffraction, HOMs, mouth reflections, ...) why those long horns used in their tests sounded colored, which probably had nothing to do with horn length per se.
In their article, N&H note that one particular long (>30cm) wooden radial horn (Fostex H320) did NOT sound colored at all (in fact, in the blind test they ran it resulted as sounding the closest to a direct radiator, tonally). Baffled by what to them appeared to be a contradiction of the empirical 'rule' they were set to prove ("once horns are longer than 30 cm, you start to hear colorations"), they decided that in that particular case only the short (<10cm) metal throat adaptor should be regarded as the "true" horn, while the wooden "lips" should only be seen as "directivity devices" that have no influence on sound coloration.
In all honesty, this sounds to me like a blatant attempt to defend a wrong thesis (>30cm = colorations) in the face of contradicting evidence (the Fostex horn), using an ad-hoc hypothesis that does not stand scrutiny (the wooden "lips" DO still follow an exponential expansion rate, and, for all intents and purposes, are integral part of the overall horn).
Marco
I am aware of the original research that arrived at this conclusion (Newell and Holland), but I still think that this is essentially an unsupported claim - or, rather: a case where the observed colorations in the case of longer horns were coincidental, rather than the result of horn length itself.
I.e. there may have been other reasons (horn wall vibrations, diffraction, HOMs, mouth reflections, ...) why those long horns used in their tests sounded colored, which probably had nothing to do with horn length per se.
In their article, N&H note that one particular long (>30cm) wooden radial horn (Fostex H320) did NOT sound colored at all (in fact, in the blind test they ran it resulted as sounding the closest to a direct radiator, tonally). Baffled by what to them appeared to be a contradiction of the empirical 'rule' they were set to prove ("once horns are longer than 30 cm, you start to hear colorations"), they decided that in that particular case only the short (<10cm) metal throat adaptor should be regarded as the "true" horn, while the wooden "lips" should only be seen as "directivity devices" that have no influence on sound coloration.
In all honesty, this sounds to me like a blatant attempt to defend a wrong thesis (>30cm = colorations) in the face of contradicting evidence (the Fostex horn), using an ad-hoc hypothesis that does not stand scrutiny (the wooden "lips" DO still follow an exponential expansion rate, and, for all intents and purposes, are integral part of the overall horn).
Marco
You can listen to recordings of a conical horn almost twice that length with various drivers here:
http://www.diyaudio.com/forums/multi-way/212240-high-frequency-compression-driver-evaluation.html
Listen for yourself if the horn sounds "colored" or if the different drivers (Aluminum, Polyester, Titanium diaphragms) dynamics sound any different at the different SPL and drive levels the recordings were made at.
Other than noting the distortion differences at high drive levels, so far no one has mentioned anything about dynamic differences.
Art
This legend of the colouration of horns as soon their length is over 30cm was originally due to a paper writen by Newell and Holland published in 1995 in JAES.
http://www.nutshellhifi.com/library/Holland&Newell_1995_Sound_of_Horns.pdf
This was at a time where the termination of the mouth of the horn was considered as secondary.
Good horns having a termination able to produce very few refelction from mouth to throat have been proved to have very few colouration. (And one of the 2 best horns in the above paper has such curved termination at the mouth)
IMHO there is not an ounce of truth in that legend. Horn colouration is not related to the length of the horn.
( Unfortunately, even Lynn Olson as many used to consider that paper.)
Best regards from Paris, France
Jean-Michel
I quite agree that length alone is not the cause of coloration in horns, the whole design from driver through horn lip all need to match up. One wrong part can cause wrong conclusions.
I have not done enough research to know how each part effects perceived sound, but I have done enough to know I would take too much time to get a combination to my satisfaction, and I have access to very few horn designs with none coming close. But I have worked with direct radiating drivers long enough to have a good feeling what needs work and to prioritize efforts to reasonable steps. But I definitely will get back to horns when I get to the larger speakers. Hopefully I can get a compression driver supplier to work with me on new designs then.
Right now, I have the 3" direct radiating driver where the performance is satisfactory, but some improvements will be made in the next round. Some of the customer process takes up too much labor and hard to control quality in large quantities. The 6" attempt is two fold, tuning a concept to provide wide range while keeping the production process as common to current practices as possible.
Low level listening is the best I have experienced so far, and I play at levels where it is pretty much not audible in the next room even with the door open.
I have not done enough research to know how each part effects perceived sound, but I have done enough to know I would take too much time to get a combination to my satisfaction, and I have access to very few horn designs with none coming close. But I have worked with direct radiating drivers long enough to have a good feeling what needs work and to prioritize efforts to reasonable steps. But I definitely will get back to horns when I get to the larger speakers. Hopefully I can get a compression driver supplier to work with me on new designs then.
Right now, I have the 3" direct radiating driver where the performance is satisfactory, but some improvements will be made in the next round. Some of the customer process takes up too much labor and hard to control quality in large quantities. The 6" attempt is two fold, tuning a concept to provide wide range while keeping the production process as common to current practices as possible.
Low level listening is the best I have experienced so far, and I play at levels where it is pretty much not audible in the next room even with the door open.
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Hello soongsc,
For most listeners, the common meaning of dynamic differs of the definition we used in signal analysis.
For audiophile a system is considered as dynamic in given listening conditions (evening in a quiet home, inside a car in a crowdy road , etc.) when the listener can easily listen to details during low volume excerpts of a record and when with the same gain setting his audition is not saturated on large volume excerpts. The audiophile defines dynamic during audition as the ability to reproduce both small and large signals, without having to modify gain.
In many listening environment not enabling to reproduce 120 dB, we have in order to obtain such result to use more or less compression of the signal (and preferably H2 distorsion added to the signal). Then, in different listening conditions (window of level between min accepable level to perceive détails and max levels allowed), this can be obtained using different type of loudspeakers .
Best regards from Paris, France
Jean-Michel Le Cléac'h
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I have spent some time pondering this as well.
One possible explanation would be that for the mix between direct sound and room/reverberant energy that is captured on the recording, there is an implied distance from the source and when your replay level matches roughly the level that you would experience from that source at that distance, this aspect is satisfied and it sounds more plausible. This would all be judged subliminally, typically.
One other point that I would like to make is about construction methods and materials used in horn manufacturing. Very early on I happened to take an old Altec 311 aluminum horn and copied the exact contour of that horn and duplicated it in an alternative material. To say that they sounded different would be an understatement. The material that I used was a glass filled micro balloon and polyester material of my own creation. This was strictly an experiment to compare materials, not to change any other parameter of the horn design. I don't have the response curves any longer but they were very different and it was obvious to everybody who heard them that they did not sound the same. I used this original work and much more to develop horn lenses that I produced from polyurethane foam material that was the first use of this material that I know of. The machine to dispense that material cost over 100K$ by itself without any ancillary equipment that was also needed to produce those parts. The only material that I can say that had a similar sonic signature to it was wood. The material has a density of 65pcf and I would have to look up the modulus of elasticity and the Young's modulus to tell you exactly what it is. So we need to look at more than just shape and expansion rates when analyzing why one waveguide sounds different than another, this becomes a very complex problem quickly as you start to add all the real contributing properties to the end result. I will be using this material in the enclosures that I am currently working on for my new speaker design.
Interesting. I have always found the Japanese wooden horns to be invariably well sounding, despite some of them being just very 'classical' (and unoriginal) radial / sectorial ones.
Marco
Marco,
I have made some beautiful wooden horns in the past from layers of mahogany or other nice woods made by stacking and gluing sections. It may not be simple for some to do, but being a pattern maker for many years I could make some very complex shapes that way. These horns always sound very nice and are very rigid and have very low resonance properties. It is just the costs of producing in this manner that make it non viable for most commercial reasons. I have heard many old Westlake Audio systems in the past that had wooden horns and have seen many wooden TAD and other radial horns. The wood does make sound very different than an equivalent aluminum or even fiberglass horn given the exact same contours.
I have made some beautiful wooden horns in the past from layers of mahogany or other nice woods made by stacking and gluing sections. It may not be simple for some to do, but being a pattern maker for many years I could make some very complex shapes that way. These horns always sound very nice and are very rigid and have very low resonance properties. It is just the costs of producing in this manner that make it non viable for most commercial reasons. I have heard many old Westlake Audio systems in the past that had wooden horns and have seen many wooden TAD and other radial horns. The wood does make sound very different than an equivalent aluminum or even fiberglass horn given the exact same contours.
Yes, source type wouldn't matter much for a given size. I was speaking in a the practical sense, based on the given bandwidth a driver is expected to cover.
As a direct radiator source for a given band has to be larger (assume we want comparable output, etc) than its CD counterpart, so multipath and HOMs kick-in earlier, which no XO can address
-- Mark
That's true. There have been controlled studies done that strongly correlate perceived reverberance/spaciousness to loudness. When blind testers are asked to rate concert hall acoustics, and are presented with a playback volume lower than that of original event, they rated concert hall acoustics as drier and less spacious than when played at actual level.
This makes complete sense, as much low level info exists (under good listening conditions) that can easily slip below the hearing threshold (or more often the noise floor of playback environment).
I'd argue that for music that is highly compressed before ever reaching human ears at inception in the studio, playback level is more simply linked to the kick-*** factor than anything else. The
floor for perception is moot.
Good stuff above. We kind of expect the dynamic range to be scalable (compress) when we lower the volume, and the obvious fact that the quietest elements can no longer be heard seems somehow wrong. Obvious in the case of a single event (cough or rattle), but what happens to the tone of an instrument or voice is less so. Lowering the volume does not really sound like increasing the distance, or a barrier - the only equivalents in nature, but it shares some of the loss in detail.
Producing good tone from a saxophone (I learnt from my teacher) requires it to be blown with power, which is uncomfortably loud in your own home. Since getting used to it (and shutting the door) I now listen to jazz at a similar volume and I am surprised just how much more there is within it then. And it demands full attention.
In short, we need volume and sensitivity. The length of the horn is not the issue to my ears. I have LM555s with a 18mm throat on a JMLC horn over a metre long and it is as clean as a 425 horn. Sounds surprisingly the same given the different BW, if that is sensible. But of course it is a lot harder to make a large horn non resonant than a small horn.
martin
Producing good tone from a saxophone (I learnt from my teacher) requires it to be blown with power, which is uncomfortably loud in your own home. Since getting used to it (and shutting the door) I now listen to jazz at a similar volume and I am surprised just how much more there is within it then. And it demands full attention.
In short, we need volume and sensitivity. The length of the horn is not the issue to my ears. I have LM555s with a 18mm throat on a JMLC horn over a metre long and it is as clean as a 425 horn. Sounds surprisingly the same given the different BW, if that is sensible. But of course it is a lot harder to make a large horn non resonant than a small horn.
martin
Hello Jean-Micheal,
It is true that different people will perceive and describe dynamic quite differently, this is why it would be interesting to get these into one room and watch the confusion.
There is a problem when drivers get close to the extremes of BL and Km, the nonlinear characteristics sort of causes high frequency harmonics to vary depending on where the VC is at the time, this creates unpredictable perception. I have heard some design configurations to sound audiophile dynamic, but the music as a whole does not sound right, and to make things more complicated, stores get really excited saying that this will sell, like a foxy lady with a fancy chassis.
What I have learned listening with different auditors is that people have there own way of pointing out very specific issues when listening to a system. This was very valuable to me. I also look at TV sets the same way, I see different problems with different TVs regardless of price. Some seem amazingly flat but colorful, some seem to have depth, but the color not right, then there are those that leave too much shadow in players move around causing blur. Sometimes I just wonder why they don't take care of those technical issues, but then there is a magic word I remembered, differentiation! Marketing wants to see differentiation, that is what they learn. If everything looked perfect enough, then the only thing to compete with is price. This is the last situation companies want to be in. Regardless whether audio or video, I personally find a way to get performance as close to the feeling the original performance as financially practical, and really hope that consumers are picky enough to do that. This is the only way companies that put forward the effort will excel. But right now, the user base is diverse on preference, and at lease a small group really want to feel the music, this is where I spend lots of effort to accomplish because it is what I wanted ever since I got my first audio equipment.
Listening is a very important part of development, and there is really no shortcut to acquiring the necessary experience. If one gets the experience, one can listen and make a good decision on what tests to make to verify the source of a sound quality problem. Lots of professionals will dismiss certain audibility issues by hanging their hat on somebody else's research, I think it is the wrong attitude.
Is 120 db important? Well, I believe it is not that absolute number that counts, rather it is what happens in that range. I trust that there is less problem in the digital technology, but rather the limitation starts from converting digital to analog throughout the analog section. Quite often people might need to do something to the source recording to compensate or compromise for those limitations. I have spent a significant amount of time trying to get an amplifier to work reliably at different listening levels from very low level up to listening levels challenging the limits of the drivers. As a mater of fact, it was even necessary to tune the frequency response in a way that will provide maximum usable SPL range of the driver providing a balance between the bandwidth. It is also necessary to want the same clean and natural sound at high volume levels as well as low. Power supply matching and layout played an important role here, again, lots of things considered that don't show up in research and textbooks. Being an audiophile my self, I found myself with a maze of cables, each attracted me at different times, but finally I had to go and get into that area as well.
Quite interestingly, most research focus on very niche parts of technology, and my specialty is integration of technology, this is why it seems easier for me to get a feeling how to integrate some ideas, understand the fundamental nature of the issue, then integrate the understanding to develop solutions. Things would be easier if a strong team were in place, but that really only happens by chance. I would say Steve Jobs was pretty lucky. Apple products are moving closer to my liking since I got my first Apple II+, at the time I got it! it cost pretty much the same I would pay for a MacBook now.
For Beyond the Ariel, I really think better integration of the analog section and good listeners with combined efforts are necessary if anything is going to come out of it. I do not see any reports on improvements and missed hits on this project, and from the discussion going on, it seems that the project is in a standing circle where things are changing, and there is no idea what part is right. This is quite different from how I am used to see work done. Generally, we will have a set of design guidelines which are established based on technical reasons, these criteria can change if there is a technical reason for the change, and in the process of development, more design criteria will be added as experience is accumulated. What this process does is that it reduces the cross effects of technical improvements allowing the improvements to be accumulative. For example, always using stiff diaphragm is a criteria, yes. It may cause problems. But it is then necessary to solve the other problems rather than shy away and revert to soft material. I am still interested to see what will result from this thread.