Jim, in the comb-filtering you talk about (vertical plane), doesn't that depend at least as much on the gap between drivers than the center-to center distance? Let's say we have a bunch of 4" square drivers. We operate them in their piston range. If they can be butted up to within a small distance (with respect to the wavelength at the highest frequency of interest), how will that be different than a continuous ribbon?
SY,
The separation between drivers in the line is the center to center distance. You can minimize this separation by mounting the drivers flange to flange which reduces the c-t-c distance. But a discrete line would only equate to a continuous line source at 20 kHz with 0.67" c-t-c spacing between drivers.
Jim
The separation between drivers in the line is the center to center distance. You can minimize this separation by mounting the drivers flange to flange which reduces the c-t-c distance. But a discrete line would only equate to a continuous line source at 20 kHz with 0.67" c-t-c spacing between drivers.
Jim
Moray
Why don't we let this one simmer, and let the dialectically talented forum members toss it around for a while.
Sneer & geer - mea culpa - thanks for the reality check.
We all have our pet peeves; regardless of my personal accomplishments or contributions to the DIY art, after almost 40yrs addicted to the audio bug, I've seen my fair share of "revolutionary" or "thinking outside the box" designs.
It's been my observation that not all of them pan out, and that occasionally there's more creativity involved in the marketing material than the actual technical design. (and when claims run counter to our generally accepted interpretations of laws of physics .....)
Few of us have the credentials to refute Roger's engineering accomplishments, but IMHO, any commercial product bearing such performance specifications and price tag is fair game for arm chair analysis.
The speaker in question will be demonstrated at the RMAF06 (Room 1104) in October, and hopefully a wider audience will be able to appreciate and publish their reviews and names.
BTW, I find this FAQ particularly interesting:
how does that work?
Why don't we let this one simmer, and let the dialectically talented forum members toss it around for a while.
Sneer & geer - mea culpa - thanks for the reality check.
We all have our pet peeves; regardless of my personal accomplishments or contributions to the DIY art, after almost 40yrs addicted to the audio bug, I've seen my fair share of "revolutionary" or "thinking outside the box" designs.
It's been my observation that not all of them pan out, and that occasionally there's more creativity involved in the marketing material than the actual technical design. (and when claims run counter to our generally accepted interpretations of laws of physics .....)
Few of us have the credentials to refute Roger's engineering accomplishments, but IMHO, any commercial product bearing such performance specifications and price tag is fair game for arm chair analysis.
The speaker in question will be demonstrated at the RMAF06 (Room 1104) in October, and hopefully a wider audience will be able to appreciate and publish their reviews and names.
BTW, I find this FAQ particularly interesting:
how does that work?
Hi folks -
I'm new here, finally decided to join the forum after lurking a while. I've been intrigued by full range line arrays for awhile. I dicovered R. Russell's IDS-25 design during some surfing a week ago, and am delighted to see it being discused here. I might be wrong, but I think the point he is trying to make in his comb filtering article is that it's measurable by an instrument, but our brain doesn't hear it, at least not enough for it to be a problem. He's not saying comb filtering doesn't exist. There's lot's of things in audio that are measurable but don't matter when it come's to our ears and brains. All the distortion of tube gear is a pretty good example of that. Anyway, that's the gist I get from his article.
His web site also makes reference to him publishing this very design for DIY in the July 2006 issue of AudioXpress. Does anybody have a copy handy? I'm wondering what drivers he specifies.
Also on the subject, what about a tall panel speaker, like a Maggie or a Martin Logan. I had a pair of Logans a few years ago, and they sounded incredibly pure in the high frequencies, and yet they're puting out the same high frequency information three feet above my head (while sitting down) as is coming straight at me from the middle of the panel. The sound coming from higher up is obviously farther from my ears and would be delayed, but from my sitting position I heard NOTHING coming from higher up the panel. When I stood up I heard only the top of the panel. It seems to me this is the very thing Russel is talking about - the brain zero's in on the sound coming from the closest point, and eliminates the "mess" that would occur if we heard the whole thing at once (from comb filtering, delay, or whatever). Seems to me this "Hass effect" is a very important thing, and would work the same for any long sound source, whether it be a long panel or an array.
I'm new here, finally decided to join the forum after lurking a while. I've been intrigued by full range line arrays for awhile. I dicovered R. Russell's IDS-25 design during some surfing a week ago, and am delighted to see it being discused here. I might be wrong, but I think the point he is trying to make in his comb filtering article is that it's measurable by an instrument, but our brain doesn't hear it, at least not enough for it to be a problem. He's not saying comb filtering doesn't exist. There's lot's of things in audio that are measurable but don't matter when it come's to our ears and brains. All the distortion of tube gear is a pretty good example of that. Anyway, that's the gist I get from his article.
His web site also makes reference to him publishing this very design for DIY in the July 2006 issue of AudioXpress. Does anybody have a copy handy? I'm wondering what drivers he specifies.
Also on the subject, what about a tall panel speaker, like a Maggie or a Martin Logan. I had a pair of Logans a few years ago, and they sounded incredibly pure in the high frequencies, and yet they're puting out the same high frequency information three feet above my head (while sitting down) as is coming straight at me from the middle of the panel. The sound coming from higher up is obviously farther from my ears and would be delayed, but from my sitting position I heard NOTHING coming from higher up the panel. When I stood up I heard only the top of the panel. It seems to me this is the very thing Russel is talking about - the brain zero's in on the sound coming from the closest point, and eliminates the "mess" that would occur if we heard the whole thing at once (from comb filtering, delay, or whatever). Seems to me this "Hass effect" is a very important thing, and would work the same for any long sound source, whether it be a long panel or an array.
Near field line arrays do have the characteristic that their sound decreases by 3 dB per doubling of the distance vs. 6 dB per doubling of the distance for a point source. Hence, in a listening room the sound intensity is nearly constant. Thus you can walk toward the sources and hardly discern a volume change. This characteristic is well described in my Near Field Line Array White Paper (NFLAWP).
This characteristic happens for either discrete driver line arrays or continuous driver line sources. It really has nothing to do with driver spacing (comb lining) but rather depends on the array or source height and frequency.
Jim
Near Field Line Array White Paper
This characteristic happens for either discrete driver line arrays or continuous driver line sources. It really has nothing to do with driver spacing (comb lining) but rather depends on the array or source height and frequency.
Jim
Near Field Line Array White Paper
planet10 said:
I understand that, but that's not really the point I was trying to make. Forget about "comb filtering" for a moment. With a large panel speaker there obviously is sound coming from the whole thing, and some points on that panel are farther from your ears than other points. And yet you don't hear any delay effects or muddyness of any kind. Just pristine clarity that seams to be coming from a single point source. I'm no expert, but it seems to me that this "Hass effect" where the brain picks up the first sound to arrive and cancel's out the "mud" following it (within a very small time window) might be the reason. An instument measuring such a speaker (or an array) would pick up everything, and yet our ears don't seem too. At least mine don't - I hear what seams to be a point source when I listen to a single panel speaker or array. If this Hass effect phenomenon is true, instument measurements of comb filtering could very well be irrelevant to what we actualy hear, as Roger Russell says.
I've tried DIY line arrays and found them to have an interesting sound, but in the end decided they dont solve any real problem and only create more problems. I think they are generally a solution looking for a problem.
Advtanges
-------------
1. Very quick and dynamic sounding. Micro details resolved very well.
2. can really throw sound out there.
3. Dynamics seem similar to live music event.
Disadvantgages
--------------------
1. If expensive drivers are used then cost
2. More extensive woodworking and larger speaker size.
3. More crossover components. Or more amplifiers adding to cost.
4. Strange lack of line arrays in commercial designs outside of stadiums
5. Doesnt sound real in the living room. Very artifical sounding. Dynamics larger than life.
6. Extremely directional sound(especially vertically). Possibly not good for small living room and home theatre. In other words, the sweet spot is small. Supposedly reduced ceiling and floor reflections have never been an issue as far as Im concerned.
7. Imaging challenged. IMO, good two-ways and a few ribbons seem to do this best.
In particular, if I had to say what line arrays were good for it would be for making cheap 3" drivers sound better than they have a right to. But in the end, it's still an array of cheap drivers that have been elevated a few notches.
Advtanges
-------------
1. Very quick and dynamic sounding. Micro details resolved very well.
2. can really throw sound out there.
3. Dynamics seem similar to live music event.
Disadvantgages
--------------------
1. If expensive drivers are used then cost
2. More extensive woodworking and larger speaker size.
3. More crossover components. Or more amplifiers adding to cost.
4. Strange lack of line arrays in commercial designs outside of stadiums
5. Doesnt sound real in the living room. Very artifical sounding. Dynamics larger than life.
6. Extremely directional sound(especially vertically). Possibly not good for small living room and home theatre. In other words, the sweet spot is small. Supposedly reduced ceiling and floor reflections have never been an issue as far as Im concerned.
7. Imaging challenged. IMO, good two-ways and a few ribbons seem to do this best.
In particular, if I had to say what line arrays were good for it would be for making cheap 3" drivers sound better than they have a right to. But in the end, it's still an array of cheap drivers that have been elevated a few notches.
Slinco,
I think the difference is that your Logan's are dispersing as a true line source, as a cylinder, so any point on the plane projects sound with very little vertical dispersion. A bunch of conical drivers act as a true line source, but it's only above and below the ends of the arrays that dispersion is limited. Within the plane of the array the drivers disperse in a more normal manner (ie the array alignment doesn't force each one to beam it's energy). That's what causes the comb filtering, and why I can hear those latest arrival times of the sound from the top and bottom drivers. This effect is most likely the cause of the exaggerated and distorted imaging of multi-driver arrays.
Jim warns us against using larger drivers to keep the sonic impact of comb filtering more limited to an attenuation of the high frequencies. Then if accurate imaging is your thing vs the big sound appeal, you use Jim's suggested power tapering to make the late arrival times unnoticeable, and you get great sound with the significant benefits of an array. Whether you can go without a tweeter as Mr. Russell suggests, remains to be seen, but I think that those who dismiss line arrays from a theoretical standpoint due to comb filtering predictions are making a mistake. Line arrays offer a special kind of sound that is very different from traditional boxes, just like Open Baffles are different. I love the combination of the 2 and look forward to the opportunity to use quality drivers in that implementation.
I think the difference is that your Logan's are dispersing as a true line source, as a cylinder, so any point on the plane projects sound with very little vertical dispersion. A bunch of conical drivers act as a true line source, but it's only above and below the ends of the arrays that dispersion is limited. Within the plane of the array the drivers disperse in a more normal manner (ie the array alignment doesn't force each one to beam it's energy). That's what causes the comb filtering, and why I can hear those latest arrival times of the sound from the top and bottom drivers. This effect is most likely the cause of the exaggerated and distorted imaging of multi-driver arrays.
Jim warns us against using larger drivers to keep the sonic impact of comb filtering more limited to an attenuation of the high frequencies. Then if accurate imaging is your thing vs the big sound appeal, you use Jim's suggested power tapering to make the late arrival times unnoticeable, and you get great sound with the significant benefits of an array. Whether you can go without a tweeter as Mr. Russell suggests, remains to be seen, but I think that those who dismiss line arrays from a theoretical standpoint due to comb filtering predictions are making a mistake. Line arrays offer a special kind of sound that is very different from traditional boxes, just like Open Baffles are different. I love the combination of the 2 and look forward to the opportunity to use quality drivers in that implementation.
Comments on Line Array Questions
A few comments on the last few posts are in order:
1. "And yet you don't hear any delay effects or muddyness of any kind. Just pristine clarity that seams to be coming from a single point source. I'm no expert, but it seems to me that this "Hass effect" where the brain picks up the first sound to arrive and cancel's out the "mud" following it (within a very small time window) might be the reason. An instument measuring such a speaker (or an array) would pick up everything, and yet our ears don't seem too. At least mine don't - I hear what seams to be a point source when I listen to a single panel speaker or array. If this Hass effect phenomenon is true, instument measurements of comb filtering could very well be irrelevant to what we actualy hear, as Roger Russell says"
Observe that for a near field array the sound raidates parallel from the speaker so it doesn't spread. The Haas effect helps as well to mitigate sound overlap.
2. Replies on advantages and disadvantages of line arrays.
"Advantages
1. Very quick and dynamic sounding. Micro details resolved very well.
2. can really throw sound out there.
3. Dynamics seem similar to live music event. "
To me those are important features for my viewpoint and why one will enjoy near field line arrays.
"Disadvantages
1. If expensive drivers are used then cost
2. More extensive woodworking and larger speaker size.
3. More crossover components. Or more amplifiers adding to cost.
4. Strange lack of line arrays in commercial designs outside of stadiums
5. Doesnt sound real in the living room. Very artifical sounding. Dynamics larger than life.
6. Extremely directional sound(especially vertically). Possibly not good for small living room and home theatre. In other words, the sweet spot is small. Supposedly reduced ceiling and floor reflections have never been an issue as far as Im concerned.
7. Imaging challenged. IMO, good two-ways and a few ribbons seem to do this best."
No reason to argue about the first two points. On point #3 line arrays don't need any more crossover components than conventional point source speakers.
On point 4 the there are several commercial line arrays in the home market but they are upscale high end audio priced. Add also that line arrays aren't necessarily SAF approved in most homes.
On point 5 line arrays sound more like live music than conventional speakers but if you do most of your listening to FM radio and Ipods, then compressed music will be your standard.
On points #6 and 7 I can not agree with you. You must not have heard a good near field line array. Any vertical directivity is likely because the array that you heard did not cover both sitting and standing listening positions. It takes a near floor to ceiling height to create a consistent coherent wavefront. With near field line arrays the image space is larger--think sweet area vs. sweet spot. Again listen to more live music and you'll realize that the thought of a small sweet spot as exhibited by many stereo systems isn't realistic to live sources. You hear a wider sound more encompassing sound in a live set. That realism is best reproduced by a near field line array.
Jim
A few comments on the last few posts are in order:
1. "And yet you don't hear any delay effects or muddyness of any kind. Just pristine clarity that seams to be coming from a single point source. I'm no expert, but it seems to me that this "Hass effect" where the brain picks up the first sound to arrive and cancel's out the "mud" following it (within a very small time window) might be the reason. An instument measuring such a speaker (or an array) would pick up everything, and yet our ears don't seem too. At least mine don't - I hear what seams to be a point source when I listen to a single panel speaker or array. If this Hass effect phenomenon is true, instument measurements of comb filtering could very well be irrelevant to what we actualy hear, as Roger Russell says"
Observe that for a near field array the sound raidates parallel from the speaker so it doesn't spread. The Haas effect helps as well to mitigate sound overlap.
2. Replies on advantages and disadvantages of line arrays.
"Advantages
1. Very quick and dynamic sounding. Micro details resolved very well.
2. can really throw sound out there.
3. Dynamics seem similar to live music event. "
To me those are important features for my viewpoint and why one will enjoy near field line arrays.
"Disadvantages
1. If expensive drivers are used then cost
2. More extensive woodworking and larger speaker size.
3. More crossover components. Or more amplifiers adding to cost.
4. Strange lack of line arrays in commercial designs outside of stadiums
5. Doesnt sound real in the living room. Very artifical sounding. Dynamics larger than life.
6. Extremely directional sound(especially vertically). Possibly not good for small living room and home theatre. In other words, the sweet spot is small. Supposedly reduced ceiling and floor reflections have never been an issue as far as Im concerned.
7. Imaging challenged. IMO, good two-ways and a few ribbons seem to do this best."
No reason to argue about the first two points. On point #3 line arrays don't need any more crossover components than conventional point source speakers.
On point 4 the there are several commercial line arrays in the home market but they are upscale high end audio priced. Add also that line arrays aren't necessarily SAF approved in most homes.
On point 5 line arrays sound more like live music than conventional speakers but if you do most of your listening to FM radio and Ipods, then compressed music will be your standard.
On points #6 and 7 I can not agree with you. You must not have heard a good near field line array. Any vertical directivity is likely because the array that you heard did not cover both sitting and standing listening positions. It takes a near floor to ceiling height to create a consistent coherent wavefront. With near field line arrays the image space is larger--think sweet area vs. sweet spot. Again listen to more live music and you'll realize that the thought of a small sweet spot as exhibited by many stereo systems isn't realistic to live sources. You hear a wider sound more encompassing sound in a live set. That realism is best reproduced by a near field line array.
Jim
Jim Griffin said:
I used square for pedagogical reasons (going back to round introduced some complications I don't want to deal with yet). But now I'm back to confused. Let's take an example where our square drivers have a very narrow flange. In the limit as the flange width goes to zero, how is this different than a continuous ribbon? Does the introduction of any arbitrarily small (wrt to the highest desired frequency) break immediately "turn on" the comb filter?
Jim,
Ditto. The enlarged prime listening area, lack of floor and ceiling reflections, along with spreading the sound more evenly throughout the room (due to the distance vs spl advantage of arrays), are all key advantages in favor of line arrays even if they didn't sound bigger and more live than a point source speaker.
Sy,
I'm with you and do question CTC, because I don't believe even the higher frequencies are sourced from the center of the cone. Building it based on CTC gives you some cushion for overlap beyond the XO point, and having cushion sure beats coming up short.
Ditto. The enlarged prime listening area, lack of floor and ceiling reflections, along with spreading the sound more evenly throughout the room (due to the distance vs spl advantage of arrays), are all key advantages in favor of line arrays even if they didn't sound bigger and more live than a point source speaker.
Sy,
I'm with you and do question CTC, because I don't believe even the higher frequencies are sourced from the center of the cone. Building it based on CTC gives you some cushion for overlap beyond the XO point, and having cushion sure beats coming up short.
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