Paul Hynes
10-07-2011, 12:50
Back on Dr Bunsen Honeydew’s thread “Why do you need a speaker crossover – discuss” on the “Blank Canvas” heading, I added a few posts about the Line source loudspeaker arrays that I use in my sound system because they do not use crossovers and also because they use several mechanical solutions to achieve very good sound quality. The interest shown in these line arrays was taking the original subject off topic so I have started this thread to discuss all things relating to full range drivers used in open baffle line source loudspeaker arrays. This information I will be posting here is based on the R&D path I took developing these line arrays and any useful information I picked up along the way from other sources that has any relevance. There will be those of you that have experience with one or more of the parameters that will be covered in this thread and I welcome any discussion and any new ideas that may be of benefit to furthering the performance of this type of design. Several of my DIY enthusiast friends have already built some of the designs that I will be discussing here and they have been very pleasantly surprised at how well such simple designs can present a musical event in a domestic environment. I have no objections to anyone building these designs for their own use in a domestic environment.
For the benefit of those who have not seen the posts I made in the Doc's thread I have copied them here, as there is some useful background information and some answers to questions posed by others in them. This will save jumping around the forum.
I use full range loudspeakers without crossovers and would not sacrifice the coherent presentation I am getting with these. During the 1970’s I used Eagle FR8 full-range drive units loaded with sewer pipes, tuned to the drive units, driven with Linsley Hood Class A amplifiers (the original simplest version in turn driven by Hood’s phono stage) and really enjoyed the musical presentation these items achieved even though the measured response could have been criticised. Everyone who heard this system was in agreement that musically it was exceptional compared to what was generally available at the time for similar levels of expenditure.
Historically I have had a lot of involvement with loudspeaker design, designers and manufacturing. I have tried most of the design options available for cabinet loading and crossovers, both passive and active through the 1980’s and early 1990’s. Whilst some of these designs were impressive for one reason or another, few approached the coherence provided by my 1970s system so I went back to full range, and I have been there ever since.
Much has changed since the 1970s but loudspeaker design is still governed by the laws of Physics. Disregarding the recording chain and replay electronics, which have their own issues that need care and attention in design, recreating a convincing illusion of a live musical event requires more than most commercial loudspeaker designs can achieve.
For instance, a classical concert performance or a rock concert will require movement of air that no single small drive unit would ever be able to realistically achieve. Think about it, you cannot reproduce the full energy of a tympani drum or a kick drum realistically with an 8 inch drive unit in a small cabinet. If you mess up the phase response through the audio band the fundamental notes and their harmonics will not be reproduced with the correct time relationship causing much musical confusion. Squash the dynamic scale and the performance fails to excite as much as a live event. I agree that a flat frequency response is not as important as these three key attributes. Anything that happens to the sound in the airspace of a live acoustic musical event will be perceived as a natural occurrence, and your brain will accept this as normal if it occurs in a sound system provided the effect is not exaggerated. Allowing a loudspeaker to generate effects that are not normally perceived at a live acoustic event can be disruptive to the illusion you wish to create. This goes for other equipment in the chain of reproduction too. Measurements are useful initially to get some idea of the overall electrical/mechanical performance but should never be solely relied upon. I have heard so many designs that measure well but sound wrong and some designs that do not measure to well by accepted standards that sound great. Your ears are your best asset when designing or choosing equipment.
Paul
You could argue that my open baffle line source arrays use mechanical solutions for tricky issues. I use Visaton B200 drivers and their individual response curve is anything but flat through the audio band, although I suspect these curves were produced from drive units that were fresh off the production line and not run in. After a month or so of run in the ragged top end smoothes out considerably and the drive unit sounds more coherent through the audio band. The bass end of an individual drive unit is lightweight due to the falling response, but happily, when mounting eight drive units in a vertical array, the parallel operation of the drive units gives a large boost in efficiency in the lower mid and bass end, which reinforces the bass very nicely in a way that evens out the bass/mid response to the point where I do not feel the need for subwoofers. The bass goes very deep when there is deep bass in the program and there is no cabinet honk or restriction as the arrays are open baffle. A well recorded kick drum sounds like a kick drum and I should know what this sounds like as I usually stood near to the drummer in the group I used to play in as a youngster.
Line arrays have benefits regarding reduced room interaction due to the way they propagate energy into the room. This is another mechanical solution to reduce an age-old problem of room interaction.
I have to admit that the top end rolls off a little earlier than many would require, however this can be a blessing with some program especially from digital sources, and the treble is nicely coherent.
The near field amplitude response of the line array falls off at only 3 dB for every doubling of distance whereas a point source propagating a spherical wave front falls off at 6 dB per doubling of distance. This adds further to the overall efficiency in a beneficial way. The very high efficiency of the lines means I only need a few watts to achieve concert levels, which is a nice side effect of the parallel drive units and the effects of the way the wave front is propagated into the room, which is once again a result of a mechanical solution.
Using eight drivers per channel means the lines can move enough air for concert levels without extreme cone excursions so the distortion levels of the drive units are very low.
So effectively I have moved away from complexity by implementing mechanical solutions in the loudspeaker design to minimise components in the signal path. There are no crossover components in the arrays. This has benefited the electronics too and my power amp has one mosfet and one resistor in the direct signal path and my line preamp is an LDR L-pad with one LDR directly in series with the signal. There is just no need for any voltage gain in these sections.
This works for me and I have not felt the need to work on the speakers or amplification for over four years. Prior to that I was always fiddling around spending vast amounts of R&D time looking for improvements.
Out of interest the system is great for home cinema duty too and some of the sound effects in the blockbuster films can be awesome.
Paul
I am trying to keep up with posts on this thread tonight but things are getting a little disjointed so bear with me if I miss something,.
I cannot photo the lines this week as we are re-decorating the lounge and making it more music friendly, however I have some photos of the line arrays I took at the old Cumbrian address that are on Photobucket at the following links :-
http://i700.photobucket.com/albums/ww7/paulhynes/Picture036.jpg
http://i700.photobucket.com/albums/ww7/paulhynes/Picture039.jpg
and the power amp :-
http://i700.photobucket.com/albums/ww7/paulhynes/SE1.jpg
and the line preamp :-
http://i700.photobucket.com/albums/ww7/paulhynes/VCCS1C.jpg
Anyone wishing to experiment and use these designs for their own personal system is welcome, but please do not use them commercially without arranging a license, as this is very disrespectful, and one of the main reasons people do not publish details of their design work nowadays.
Chris (technobear),
The efficiency gain is frequency dependant and gradual. Horn-loaded systems display this effect for different reasons.. The higher frequencies tend to beam and not reinforce, but the low frequencies couple and reinforce. With a bit of care with the selection of drive units, this can give a relatively flat response down to the low frequencies.
Another attribute of the line source is the wave front generated is essentially cylindrical in its expansion into the listening area. A floor to ceiling line source would show no ceiling or floor reflection removing a prime source of room interaction. Any reflection off the side walls sounds like venue reverb. In this instance as the line are open baffle there is a reflection from the rear wall, like planar speakers. If the line arrays are orientated correctly, the delay time is long enough not to interfere with leading edge information and the imaging remains intact with the reflection once again sounding like venue reverb. Venue reverb is normal and we tend to accept it accordingly.
I am aware of the phase plug options but I am not finding problems with beaming in reality. Once again this is a natural phenomenon and I think our brains may just ignore the effect as long as it is not exaggerated. When I get some time I will experiment with the recommended phase plugs to see how they affect behaviour with the line array.
Richard,
You are quite right about the commercial issues and domestic harmony. This is why I have not bothered to market the line arrays. However I think I am one of the lucky ones in that my lass and my daughter both love music and film, and art in general for that matter, so I can do what I want with the AV system even though it is in the main lounge. With this system I have not been working on a commercial solution, it is purely for myself and I will follow my wildest dreams to get the system where I want it to be. Speaking of dreams, I often dream up solutions to engineering problems while asleep. Does this happen with you too? It can save a lot of R&D time if the dream works in real time.
Ali,
The B200 is a good driver with the right parameters for use on open baffles. It is not perfect like every other driver, but it does have that musical magic that few modern drivers, that I have tried, seem to have. As you have some to listen to you will know what I mean. I did consider large diameter bass units in the early stage of my B200 experience but the benefits of the line array were drawing me like a siren. The reason the line arrays do not sum higher up the frequency bandwidth is due to the directional nature of the higher frequencies. The further up the bandwidth you go the more directional the beam becomes. This does increase combing effects. Even with a single source, as soon as the wave front hits an obstacle and is reflected back into the sound field, a combing effect will occur. For those mot familiar with this terminology, a combing effect occurs when two or more wave fronts collide and intermingle causing reinforcement, or cancellation, depending on the relative phase of the wave front. This is a natural phenomenon and the brain accepts it as normal.
The B200 line array is 2 metres tall.
You are lucky that your lass has the same love of music as you do.
John,
The line arrays are not as overpowering as you might think, as the baffles are quite slim. Tall maybe, but slim. Is the Ben Harper you refer to in your musical appreciation the son of Roy Harper?
Anthony,
Line arrays are used a lot in Pro Audio for good reason, so I am not surprise you are familiar with them. OK, they are relatively big in the domestic environment. If you want to have a go with them I will load the original drawings on Photobucket and post links on this thread. The concept will work with other drive units as long as they are happy working on an open baffle and have a reasonable bandwidth. I have tried some lower cost full range drivers but the results were less satisfactory. In fact I have just skipped a load of unsatisfactory drive units. Recycled properly of course.
Paul
Now to catch up with the line source array posts on the Doc's thread.
Paul
For the benefit of those who have not seen the posts I made in the Doc's thread I have copied them here, as there is some useful background information and some answers to questions posed by others in them. This will save jumping around the forum.
I use full range loudspeakers without crossovers and would not sacrifice the coherent presentation I am getting with these. During the 1970’s I used Eagle FR8 full-range drive units loaded with sewer pipes, tuned to the drive units, driven with Linsley Hood Class A amplifiers (the original simplest version in turn driven by Hood’s phono stage) and really enjoyed the musical presentation these items achieved even though the measured response could have been criticised. Everyone who heard this system was in agreement that musically it was exceptional compared to what was generally available at the time for similar levels of expenditure.
Historically I have had a lot of involvement with loudspeaker design, designers and manufacturing. I have tried most of the design options available for cabinet loading and crossovers, both passive and active through the 1980’s and early 1990’s. Whilst some of these designs were impressive for one reason or another, few approached the coherence provided by my 1970s system so I went back to full range, and I have been there ever since.
Much has changed since the 1970s but loudspeaker design is still governed by the laws of Physics. Disregarding the recording chain and replay electronics, which have their own issues that need care and attention in design, recreating a convincing illusion of a live musical event requires more than most commercial loudspeaker designs can achieve.
For instance, a classical concert performance or a rock concert will require movement of air that no single small drive unit would ever be able to realistically achieve. Think about it, you cannot reproduce the full energy of a tympani drum or a kick drum realistically with an 8 inch drive unit in a small cabinet. If you mess up the phase response through the audio band the fundamental notes and their harmonics will not be reproduced with the correct time relationship causing much musical confusion. Squash the dynamic scale and the performance fails to excite as much as a live event. I agree that a flat frequency response is not as important as these three key attributes. Anything that happens to the sound in the airspace of a live acoustic musical event will be perceived as a natural occurrence, and your brain will accept this as normal if it occurs in a sound system provided the effect is not exaggerated. Allowing a loudspeaker to generate effects that are not normally perceived at a live acoustic event can be disruptive to the illusion you wish to create. This goes for other equipment in the chain of reproduction too. Measurements are useful initially to get some idea of the overall electrical/mechanical performance but should never be solely relied upon. I have heard so many designs that measure well but sound wrong and some designs that do not measure to well by accepted standards that sound great. Your ears are your best asset when designing or choosing equipment.
Paul
You could argue that my open baffle line source arrays use mechanical solutions for tricky issues. I use Visaton B200 drivers and their individual response curve is anything but flat through the audio band, although I suspect these curves were produced from drive units that were fresh off the production line and not run in. After a month or so of run in the ragged top end smoothes out considerably and the drive unit sounds more coherent through the audio band. The bass end of an individual drive unit is lightweight due to the falling response, but happily, when mounting eight drive units in a vertical array, the parallel operation of the drive units gives a large boost in efficiency in the lower mid and bass end, which reinforces the bass very nicely in a way that evens out the bass/mid response to the point where I do not feel the need for subwoofers. The bass goes very deep when there is deep bass in the program and there is no cabinet honk or restriction as the arrays are open baffle. A well recorded kick drum sounds like a kick drum and I should know what this sounds like as I usually stood near to the drummer in the group I used to play in as a youngster.
Line arrays have benefits regarding reduced room interaction due to the way they propagate energy into the room. This is another mechanical solution to reduce an age-old problem of room interaction.
I have to admit that the top end rolls off a little earlier than many would require, however this can be a blessing with some program especially from digital sources, and the treble is nicely coherent.
The near field amplitude response of the line array falls off at only 3 dB for every doubling of distance whereas a point source propagating a spherical wave front falls off at 6 dB per doubling of distance. This adds further to the overall efficiency in a beneficial way. The very high efficiency of the lines means I only need a few watts to achieve concert levels, which is a nice side effect of the parallel drive units and the effects of the way the wave front is propagated into the room, which is once again a result of a mechanical solution.
Using eight drivers per channel means the lines can move enough air for concert levels without extreme cone excursions so the distortion levels of the drive units are very low.
So effectively I have moved away from complexity by implementing mechanical solutions in the loudspeaker design to minimise components in the signal path. There are no crossover components in the arrays. This has benefited the electronics too and my power amp has one mosfet and one resistor in the direct signal path and my line preamp is an LDR L-pad with one LDR directly in series with the signal. There is just no need for any voltage gain in these sections.
This works for me and I have not felt the need to work on the speakers or amplification for over four years. Prior to that I was always fiddling around spending vast amounts of R&D time looking for improvements.
Out of interest the system is great for home cinema duty too and some of the sound effects in the blockbuster films can be awesome.
Paul
I am trying to keep up with posts on this thread tonight but things are getting a little disjointed so bear with me if I miss something,.
I cannot photo the lines this week as we are re-decorating the lounge and making it more music friendly, however I have some photos of the line arrays I took at the old Cumbrian address that are on Photobucket at the following links :-
http://i700.photobucket.com/albums/ww7/paulhynes/Picture036.jpg
http://i700.photobucket.com/albums/ww7/paulhynes/Picture039.jpg
and the power amp :-
http://i700.photobucket.com/albums/ww7/paulhynes/SE1.jpg
and the line preamp :-
http://i700.photobucket.com/albums/ww7/paulhynes/VCCS1C.jpg
Anyone wishing to experiment and use these designs for their own personal system is welcome, but please do not use them commercially without arranging a license, as this is very disrespectful, and one of the main reasons people do not publish details of their design work nowadays.
Chris (technobear),
The efficiency gain is frequency dependant and gradual. Horn-loaded systems display this effect for different reasons.. The higher frequencies tend to beam and not reinforce, but the low frequencies couple and reinforce. With a bit of care with the selection of drive units, this can give a relatively flat response down to the low frequencies.
Another attribute of the line source is the wave front generated is essentially cylindrical in its expansion into the listening area. A floor to ceiling line source would show no ceiling or floor reflection removing a prime source of room interaction. Any reflection off the side walls sounds like venue reverb. In this instance as the line are open baffle there is a reflection from the rear wall, like planar speakers. If the line arrays are orientated correctly, the delay time is long enough not to interfere with leading edge information and the imaging remains intact with the reflection once again sounding like venue reverb. Venue reverb is normal and we tend to accept it accordingly.
I am aware of the phase plug options but I am not finding problems with beaming in reality. Once again this is a natural phenomenon and I think our brains may just ignore the effect as long as it is not exaggerated. When I get some time I will experiment with the recommended phase plugs to see how they affect behaviour with the line array.
Richard,
You are quite right about the commercial issues and domestic harmony. This is why I have not bothered to market the line arrays. However I think I am one of the lucky ones in that my lass and my daughter both love music and film, and art in general for that matter, so I can do what I want with the AV system even though it is in the main lounge. With this system I have not been working on a commercial solution, it is purely for myself and I will follow my wildest dreams to get the system where I want it to be. Speaking of dreams, I often dream up solutions to engineering problems while asleep. Does this happen with you too? It can save a lot of R&D time if the dream works in real time.
Ali,
The B200 is a good driver with the right parameters for use on open baffles. It is not perfect like every other driver, but it does have that musical magic that few modern drivers, that I have tried, seem to have. As you have some to listen to you will know what I mean. I did consider large diameter bass units in the early stage of my B200 experience but the benefits of the line array were drawing me like a siren. The reason the line arrays do not sum higher up the frequency bandwidth is due to the directional nature of the higher frequencies. The further up the bandwidth you go the more directional the beam becomes. This does increase combing effects. Even with a single source, as soon as the wave front hits an obstacle and is reflected back into the sound field, a combing effect will occur. For those mot familiar with this terminology, a combing effect occurs when two or more wave fronts collide and intermingle causing reinforcement, or cancellation, depending on the relative phase of the wave front. This is a natural phenomenon and the brain accepts it as normal.
The B200 line array is 2 metres tall.
You are lucky that your lass has the same love of music as you do.
John,
The line arrays are not as overpowering as you might think, as the baffles are quite slim. Tall maybe, but slim. Is the Ben Harper you refer to in your musical appreciation the son of Roy Harper?
Anthony,
Line arrays are used a lot in Pro Audio for good reason, so I am not surprise you are familiar with them. OK, they are relatively big in the domestic environment. If you want to have a go with them I will load the original drawings on Photobucket and post links on this thread. The concept will work with other drive units as long as they are happy working on an open baffle and have a reasonable bandwidth. I have tried some lower cost full range drivers but the results were less satisfactory. In fact I have just skipped a load of unsatisfactory drive units. Recycled properly of course.
Paul
Now to catch up with the line source array posts on the Doc's thread.
Paul