Hi there,
me thinks one thing is "swinging" and "nobaffle" is another.
Swinging is cool concerning vibration and nobaffle too.
But the situations where you can afford loosing a whole
octave bandwith or more are quite limited.
Pic shows a 100mm diameter driver without baffle and
on a tiny baffle approx 22cm x 35cm.
Should i reveal which is which ?
Kind Regards
me thinks one thing is "swinging" and "nobaffle" is another.
Swinging is cool concerning vibration and nobaffle too.
But the situations where you can afford loosing a whole
octave bandwith or more are quite limited.
Pic shows a 100mm diameter driver without baffle and
on a tiny baffle approx 22cm x 35cm.
Should i reveal which is which ?
Kind Regards
Attachments
Last edited:
OB Vibes
OBers,
Permit me to present a few thoughts for your consideration, analysis, assessment and judgment. If in the process a current practice or method is criticised, kindly take it in the light of the argument, and not otherwise. An active discussion on these basics is only going to help clear the air, I believe.
Let us face it--how many dynamic drivers are presently manufactured for use in Open Baffles, or to be used without baffles? None, to my knowledge.
So assuming that most are intended to be used with baffles, let us look at how we make a selection. Drivers are selected for a particular frequency band of interest based on the maker's data. When it comes to OB use, 'reasonable' levels of equalization too are in the mind of the designer.
OB developed as a reaction to the ills of the closed baffle. Then the reaction against truly large, if not infinite, baffles led to the present crop of optimized 'just-enough'-sized crop of baffles. As a progression, many thought that if a smaller baffle was better, surely 'no-baffle' was the best. The bandwaggon effect attracted many to this fold as the argument appeared logical. IMHO, a most unfortunate state of affairs. Why?
A driver's reproduction band depends on its piston area, the area of the baffle and other parameters. And the 'nudist' (no-baffle, nude+ purist) ends up in a corner when he chooses a driver that can handle a particular range in a 'nude' status, when he later finds that the characteristics of the driver of choice is counter to other requirements like the polar pattern, 'beaming' etc. There is a practical limit to equalization, and eq should always be a 'soft' compromise, I believe.
So let us accept that the driver, being designed for use with a baffle, has to have one, however small, to raise it to within the 'passband' of acceptability and usability within the chosen range. As I hinted at earlier, if the maker had intended it for use as a nude driver, he would have given it a different geometry--as I understand it something that is dictated by the laws of physics.
Rather than being sidetracked by enthusiasm to do away entirely with the baffle once we find that it is 'bad', we should be objectively examining it and 'cutting it down' to our minimal requirements. We have now within our reach good software simulation and measurement tools that make the task of analysis and design easier. It takes only a matter of minutes to analyze a full set of variants and come to some educated conclusions. Let us prudently base our design decisions on these very essential basic steps, and not be carried away by a 'trend'.
So in sum, if you want to do away with the baffle, you are welcome to pare it down to the minimum so that it will meet the requirements of the passband, directivity etc, and it should be a happy compromise when it comes to eq etc. If you want to operate 'nude', make sure that your penchant for that doesnt lead you to err on other sides.
The beacon light on which we have fixed our collective gazes on is an uncoloured reproduction of what I would call 'recorded reality'. This surely calls for compromises, but my call is for intelligent and objective compromises.
Having put the ball into play, I urge the more knowledgeable among my peers to think aloud so that the air is clarified and our mission of reaching the goal is made easier.
Good vibes to all.
OBers,
Permit me to present a few thoughts for your consideration, analysis, assessment and judgment. If in the process a current practice or method is criticised, kindly take it in the light of the argument, and not otherwise. An active discussion on these basics is only going to help clear the air, I believe.
Let us face it--how many dynamic drivers are presently manufactured for use in Open Baffles, or to be used without baffles? None, to my knowledge.
So assuming that most are intended to be used with baffles, let us look at how we make a selection. Drivers are selected for a particular frequency band of interest based on the maker's data. When it comes to OB use, 'reasonable' levels of equalization too are in the mind of the designer.
OB developed as a reaction to the ills of the closed baffle. Then the reaction against truly large, if not infinite, baffles led to the present crop of optimized 'just-enough'-sized crop of baffles. As a progression, many thought that if a smaller baffle was better, surely 'no-baffle' was the best. The bandwaggon effect attracted many to this fold as the argument appeared logical. IMHO, a most unfortunate state of affairs. Why?
A driver's reproduction band depends on its piston area, the area of the baffle and other parameters. And the 'nudist' (no-baffle, nude+ purist) ends up in a corner when he chooses a driver that can handle a particular range in a 'nude' status, when he later finds that the characteristics of the driver of choice is counter to other requirements like the polar pattern, 'beaming' etc. There is a practical limit to equalization, and eq should always be a 'soft' compromise, I believe.
So let us accept that the driver, being designed for use with a baffle, has to have one, however small, to raise it to within the 'passband' of acceptability and usability within the chosen range. As I hinted at earlier, if the maker had intended it for use as a nude driver, he would have given it a different geometry--as I understand it something that is dictated by the laws of physics.
Rather than being sidetracked by enthusiasm to do away entirely with the baffle once we find that it is 'bad', we should be objectively examining it and 'cutting it down' to our minimal requirements. We have now within our reach good software simulation and measurement tools that make the task of analysis and design easier. It takes only a matter of minutes to analyze a full set of variants and come to some educated conclusions. Let us prudently base our design decisions on these very essential basic steps, and not be carried away by a 'trend'.
So in sum, if you want to do away with the baffle, you are welcome to pare it down to the minimum so that it will meet the requirements of the passband, directivity etc, and it should be a happy compromise when it comes to eq etc. If you want to operate 'nude', make sure that your penchant for that doesnt lead you to err on other sides.
The beacon light on which we have fixed our collective gazes on is an uncoloured reproduction of what I would call 'recorded reality'. This surely calls for compromises, but my call is for intelligent and objective compromises.
Having put the ball into play, I urge the more knowledgeable among my peers to think aloud so that the air is clarified and our mission of reaching the goal is made easier.
Good vibes to all.
I'm not sure what exactly you were trying to say (a technical writer you do not seem to be) but I disagree with your contention that one cannot find a driver for most any given passband that doesn't require a baffle. Quick example: a baffleless 12" driver works great up to about 500Hz, with low end limited to excursion/distortion.
Wouldn't hurt for the folks who aren't familiar with dipole peaks.
Baffle versus no baffle is really a tradeoff between mechanical equalization, electrical equalization, maximum SPL, and the engineering complexity and directivity tradeoffs of producing a baffle which provides a significant amount of mechanical equalization. Personally I've not hit any situations in which I couldn't afford to raise the dipole peak; in my experience where baffles start to become attractive is around 95dB SPL. It depends on the music and other details, but that's nominally an average SPL 5dB above the OHSA threshold for permanent hearing loss and 10dB above the EU threshold. So if you find you can't hit a desired SPL in home audio without a baffle it's probably time to step back and ask a few hard questions about just how important that last octave really is.
Granted, if you're locked into passive crossovers then you're probably reliant on using baffles to provide mechanical equalization so as not to kill the crossover's efficiency. But in the past few months I'm only recalling one passive dipole build (mige0's) here on DIY; the rest all use digital crossovers and equalization.
Same here. Selection can be a bit limited in 18s and is quite restricted at 21 and above. But for 15s and smaller the problem's usually filtering out all the drivers you don't want to use to find the ones which you do want.
Last edited:
OB Vibes
454Casull,
Your quick example is all right, but have you considered its 'strengths' vis-a-vis directionality/beaming etc?
A better and a flatter response can be realized, I guess, with a much smaller driver on a small baffle considerably smaller than 12 inches--and that too without making any compromises on the polar pattern and beaming.
And have you tried comparing the sims of a circular and a rectangular baffle?
I am anticipating the evolution of an 'ideal' design for a good OB (or even a 'nude' baffle-less model) as a result of the knowledgeable interaction here. I certainly am NOT a pundit who knows everything.
Here's to good vibes!
454Casull,
Your quick example is all right, but have you considered its 'strengths' vis-a-vis directionality/beaming etc?
A better and a flatter response can be realized, I guess, with a much smaller driver on a small baffle considerably smaller than 12 inches--and that too without making any compromises on the polar pattern and beaming.
And have you tried comparing the sims of a circular and a rectangular baffle?
I am anticipating the evolution of an 'ideal' design for a good OB (or even a 'nude' baffle-less model) as a result of the knowledgeable interaction here. I certainly am NOT a pundit who knows everything.
Here's to good vibes!
So at first id like to underscore that a baffle can provide
acoustical equalization when designed properly.
At low frequencies you have to provide higher displacement
volume without baffle, so you have to use larger drivers with
nobaffle, since you also are dependent on the self baffling
effect of the driver.
Larger drivers are band limited to their top end by breackup
so you have to have "more ways" ...
To me "nobaffle" is one extreme option to choose in the
"sizeof baffle" continuum, which can be interesting
in some situations.
To make it a design paradigm is not comprehensible to
me, because it introduces restrictions in an unnecessary
way.
Especially making it a design paradigm for the low frequency
end would be - sorry - ridiculous.
That is rather some kind of "large driver", "long throw",
"cool equalization" sport. The most expensive monster
wins.
Sorry for being that direct. Nothing to say against
active concepts though, there are for sure some more
degrees of freedom in compensation.
Kind Regards
Since lobing and directivity has been used as an argument
against baffles, there are some sources available
e.g. at linkwitzlab.com
or
http://www.wvier.de/texte/Dipollautsprecher-FV.pdf
stating that a baffle width of driver diameter
D x 2.2 yields the most balanced response and
should not be exceeded to avoid lobing.
This leads in fact to very narrow baffles, in the
particular plane where lobing is to be avoided.
(Mostly side lobing is the more relevant.)
To minimize diffraction artefacts also a rounded
shape of the edges (depending on directivity of
the driver in the frequency range under question)
and an asymmetrical position of the driver on the baffle
is advantageous.
(Adding a rounded structure at the circumference
of a driver basket means "adding a baffle" right ?
I am just asking.)
Both techiques are suppressed by the "nobaffle"
paradigm ...
As long as we have to stay with real drivers, not idealized
ones, the directivity pattern is also influenced dominantly
from breackup modes of the drivers themselves at higher
frequencies.
As mentioned before, a design paradigm enforcing larger
drivers also enforces breackup, if not accounted for by
increasing the number of of ways by using specialized
drivers within their smaller usable bandwiths to avoid
that breakup.
It is simply untrue, that all these severe problems
- which are introduced by the "nobaffle" option if
m i s u s e d and m i s u n d e r s t o o d as a
design paradigm -
can be "equalized", since
- mechanical limits,
- cone breackup and
- spatialy and time distributed effects of diffraction
are (have been, are right now and will be) beyond
the scope of equalizing.
Kind Regards
against baffles, there are some sources available
e.g. at linkwitzlab.com
or
http://www.wvier.de/texte/Dipollautsprecher-FV.pdf
stating that a baffle width of driver diameter
D x 2.2 yields the most balanced response and
should not be exceeded to avoid lobing.
This leads in fact to very narrow baffles, in the
particular plane where lobing is to be avoided.
(Mostly side lobing is the more relevant.)
To minimize diffraction artefacts also a rounded
shape of the edges (depending on directivity of
the driver in the frequency range under question)
and an asymmetrical position of the driver on the baffle
is advantageous.
(Adding a rounded structure at the circumference
of a driver basket means "adding a baffle" right ?
I am just asking.)
Both techiques are suppressed by the "nobaffle"
paradigm ...
As long as we have to stay with real drivers, not idealized
ones, the directivity pattern is also influenced dominantly
from breackup modes of the drivers themselves at higher
frequencies.
As mentioned before, a design paradigm enforcing larger
drivers also enforces breackup, if not accounted for by
increasing the number of of ways by using specialized
drivers within their smaller usable bandwiths to avoid
that breakup.
It is simply untrue, that all these severe problems
- which are introduced by the "nobaffle" option if
m i s u s e d and m i s u n d e r s t o o d as a
design paradigm -
can be "equalized", since
- mechanical limits,
- cone breackup and
- spatialy and time distributed effects of diffraction
are (have been, are right now and will be) beyond
the scope of equalizing.
Kind Regards
Last edited:
OB vibes
Dear all,
Sorry for the gap of a few weeks. Busy with many things, but with the investigations too in the meantime.
Permit me to present the results of some baffle vibration investigations. These are empirical results. The intention is to share it with you so that the more knowledgeable among you might choose to pursue it further in a more scientific manner so that all of us would benefit.
The test gear was simplicity itself-- a good low power amp with lo-cut and hi-cut filters and a pair of good, 'known' speakers, fed by the 'probe' made from an old LP piezo cartridge. Be warned though, that it is easy to generate high amplitude transients with accidental knocks etc and fry the amp or the speaker. Always mute the amp/turn down the volume while you adjust the setup.
My plan was to look for ways to minimize the baffle vibrations at its core. As we all know, large baffles and boxes do contribute a lot more than the drivers do, the more so at lower frequencies. But even at higher frequencies, the 'smearing' produced by unwanted panel vibrations do spoil the imaging, which I believe is the basis of enjoyment in reproduced music.
Please note that the 'ground reference' is the fixture which connects the system to ground. The judgements are highly subjective, though every attempt is made not to be biased. The quantity and nature ('sound') of the unwanted vibration is rated on a scale of 1 to 10 and each setup is judged and rated.
The conventional mounting practice is to mount the driver rigidly to the baffle. So a rectangular baffle with various mounting options were tested and rated. The baffle is 20 mm ply and the driver used is an average 8" woofer. Please refer to the sketches attached.
1. Conventional setup. The baffle is upright and 'ground referenced' at its edges, with the driver mounted rigidly to it.
Very powerful vibes emitted by the baffle. The complexity of the vibrations is also high.
2. The same mounting as above, but with the baffle horizontal and ground-ref at the baffle edges.
Vibrations reduced, probably because of the weight of the driver and gravity contributing to some panel stiffening/damping.
3. Same as above, but with the system ground-ref at the magnet structure. Much lower vibrations, shifting to slightly higher frequency ranges -- a change in baffle material is likely to affect the 'quality' of the vibrations.
4. Same setup as above, but with the baffle edges ALSO now ground-referenced.
Great improvement overall. Still residual vibrations are there.
5. Same as above, but with the baffle decoupled from the driver basket by lossy and elastic gasket that offers an air seal.
Almost no unwanted vibrations from the baffle.
6. Upright setup, with the driver mounted and ground-referenced at the magnet structure. The mounting is made lossy by hard rubber gasket. ( A thick inner tube strip will do.) I could notice that wherever there was an 'interface' between the vibrating metal (driver, its basket etc) and the baffle, an order of improvement was obtained when there was a layer of lossy material in between, rather than when it was directly mounted.
The mounting mechanism adopted is a 'spine' of rigid material--stone, concrete, sanwiched glass etc is ideal, but at a pinch, sandwiched ply or mdf will also provide good results. The baffle is mounted in a lossy manner to the spine, with an elastic and lossy round gasket providing air-seal to the edge of the driver basket and at the same time offering a high degree of decoupling.
Almost no vibrations even at high drive levels.
7. Same setup as above, but with a baffle that is now made up of glued sheets of 12 mm and 8 mm ply and mdf. Much better results.
8. Same as above, but the baffle is now a sandwich of two sheets of ordinary window glass, with one side plain and the other side textured, naturally, with the plain sides glued together with a smear of Silicone.
Virtually no detectable vibrations.
These are the observations that I have been able to make. I present it before my more knowledgeble and research-minded peers with the hope that this could lead to better solutions. Thanks in advance.
Great vibes to all !
Dear all,
Sorry for the gap of a few weeks. Busy with many things, but with the investigations too in the meantime.
Permit me to present the results of some baffle vibration investigations. These are empirical results. The intention is to share it with you so that the more knowledgeable among you might choose to pursue it further in a more scientific manner so that all of us would benefit.
The test gear was simplicity itself-- a good low power amp with lo-cut and hi-cut filters and a pair of good, 'known' speakers, fed by the 'probe' made from an old LP piezo cartridge. Be warned though, that it is easy to generate high amplitude transients with accidental knocks etc and fry the amp or the speaker. Always mute the amp/turn down the volume while you adjust the setup.
My plan was to look for ways to minimize the baffle vibrations at its core. As we all know, large baffles and boxes do contribute a lot more than the drivers do, the more so at lower frequencies. But even at higher frequencies, the 'smearing' produced by unwanted panel vibrations do spoil the imaging, which I believe is the basis of enjoyment in reproduced music.
Please note that the 'ground reference' is the fixture which connects the system to ground. The judgements are highly subjective, though every attempt is made not to be biased. The quantity and nature ('sound') of the unwanted vibration is rated on a scale of 1 to 10 and each setup is judged and rated.
The conventional mounting practice is to mount the driver rigidly to the baffle. So a rectangular baffle with various mounting options were tested and rated. The baffle is 20 mm ply and the driver used is an average 8" woofer. Please refer to the sketches attached.
1. Conventional setup. The baffle is upright and 'ground referenced' at its edges, with the driver mounted rigidly to it.
Very powerful vibes emitted by the baffle. The complexity of the vibrations is also high.
2. The same mounting as above, but with the baffle horizontal and ground-ref at the baffle edges.
Vibrations reduced, probably because of the weight of the driver and gravity contributing to some panel stiffening/damping.
3. Same as above, but with the system ground-ref at the magnet structure. Much lower vibrations, shifting to slightly higher frequency ranges -- a change in baffle material is likely to affect the 'quality' of the vibrations.
4. Same setup as above, but with the baffle edges ALSO now ground-referenced.
Great improvement overall. Still residual vibrations are there.
5. Same as above, but with the baffle decoupled from the driver basket by lossy and elastic gasket that offers an air seal.
Almost no unwanted vibrations from the baffle.
6. Upright setup, with the driver mounted and ground-referenced at the magnet structure. The mounting is made lossy by hard rubber gasket. ( A thick inner tube strip will do.) I could notice that wherever there was an 'interface' between the vibrating metal (driver, its basket etc) and the baffle, an order of improvement was obtained when there was a layer of lossy material in between, rather than when it was directly mounted.
The mounting mechanism adopted is a 'spine' of rigid material--stone, concrete, sanwiched glass etc is ideal, but at a pinch, sandwiched ply or mdf will also provide good results. The baffle is mounted in a lossy manner to the spine, with an elastic and lossy round gasket providing air-seal to the edge of the driver basket and at the same time offering a high degree of decoupling.
Almost no vibrations even at high drive levels.
7. Same setup as above, but with a baffle that is now made up of glued sheets of 12 mm and 8 mm ply and mdf. Much better results.
8. Same as above, but the baffle is now a sandwich of two sheets of ordinary window glass, with one side plain and the other side textured, naturally, with the plain sides glued together with a smear of Silicone.
Virtually no detectable vibrations.
These are the observations that I have been able to make. I present it before my more knowledgeble and research-minded peers with the hope that this could lead to better solutions. Thanks in advance.
Great vibes to all !
Attachments
Good work!
I did some tests on this myself, and my best results was something like your #7, only with sand fillings for damping. I used two 6mm layers of MDF as an outer skin, and a 19 mm MDF with cutouts that was filled with sand. It worked very very well, and might have been even better if I had made a swing for that baffle as well. Anyway - I moved on to suspending the bare drivers instead, which I prefered over the sandloaded baffle. Maybe because the bare driver was suspended, and the baffle not, or maybe because the bare driver offered improved off-axis response? I seriously dont know.
Some pics:
I did some tests on this myself, and my best results was something like your #7, only with sand fillings for damping. I used two 6mm layers of MDF as an outer skin, and a 19 mm MDF with cutouts that was filled with sand. It worked very very well, and might have been even better if I had made a swing for that baffle as well. Anyway - I moved on to suspending the bare drivers instead, which I prefered over the sandloaded baffle. Maybe because the bare driver was suspended, and the baffle not, or maybe because the bare driver offered improved off-axis response? I seriously dont know.
Some pics:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Very thorough study indeed!
To give me (or us) a better understanding of what you did, some questions:
You fed the loudspeaker-induced vibration of the baffle back into the loudspeakers, right? What kind of input did you use? Noise, sweeps, music?
I am not shure whether this "resonance-feedback" would get focused on a few distinguished frequency peaks or would it be rather broadband? Could you tell more about it?
Can you tell us where you placed the pick-up on the baffles? Near to the driver or at the edges? Did the baffle size and the pick-up position stay the same for all tests or how did it vary?
Thanks for more information.
To give me (or us) a better understanding of what you did, some questions:
You fed the loudspeaker-induced vibration of the baffle back into the loudspeakers, right? What kind of input did you use? Noise, sweeps, music?
I am not shure whether this "resonance-feedback" would get focused on a few distinguished frequency peaks or would it be rather broadband? Could you tell more about it?
Can you tell us where you placed the pick-up on the baffles? Near to the driver or at the edges? Did the baffle size and the pick-up position stay the same for all tests or how did it vary?
Thanks for more information.
OB vibes
Wonderful craftsmanship there, Stig.
And haven't we all tried sand filling at one time or other! For a large and heavy cabinet or baffle, nothing probably can beat sand done properly.
Bare drivers have nothing much to recommend them--except when they are larger than the needed minimum size for a particular range. Go for the baffle, no wider than the recommended 2.2 x Diameter of the driver, and you are sure to reap great results.
Incidentally I obtained great results when the whole assembly was suspended on a rectangular wire frame using rubber/neopene O-rings. If you will permit me I would say, Fantastic!! Do try it and see that the suspended assembly's weight/compliance is adjusted such that the 'swing' is say, 2 HZ to 5 Hz or something like that.
I am wondering who is going to do some really scientific experimentation in this direction so that we would all have some methodologies to follow.
Thanks.
Wonderful craftsmanship there, Stig.
And haven't we all tried sand filling at one time or other! For a large and heavy cabinet or baffle, nothing probably can beat sand done properly.
Bare drivers have nothing much to recommend them--except when they are larger than the needed minimum size for a particular range. Go for the baffle, no wider than the recommended 2.2 x Diameter of the driver, and you are sure to reap great results.
Incidentally I obtained great results when the whole assembly was suspended on a rectangular wire frame using rubber/neopene O-rings. If you will permit me I would say, Fantastic!! Do try it and see that the suspended assembly's weight/compliance is adjusted such that the 'swing' is say, 2 HZ to 5 Hz or something like that.
I am wondering who is going to do some really scientific experimentation in this direction so that we would all have some methodologies to follow.
Thanks.
I opted for nobaffle, since I wanted to operate all drivers below the dipole peak, where the directivity is constant, and frequency response is very smooth. Problem is that the baffle can be no larger than 15 cm for frequencies up to 1700 Hz where I XO to the tweeter. The choices were a nude 15 cm driver or a smaller driver on a 15 cm baffle.
In the low frequency range nude drivers are just plain stupid, I definitely agree there.
Michael (mige0) has done some great work on swinging... lets hope he will find this thread.
In the low frequency range nude drivers are just plain stupid, I definitely agree there.
Michael (mige0) has done some great work on swinging... lets hope he will find this thread.
OB vibes
Thanks Rudolf.
I am sorry I didn't elaborate on the test setup. It was all kept very simple.
The test baffle was set up in the open verandah and the piezo probe fitted to a gooseneck was touched to the baffle. The monitoring took place in the adjacent room. I played a low-range sweep tone from the computer and an amp feeding the test speaker and listened to the sounds that were coming out of the baffle via the pick-up, monitoring amp and speakers.
It is a 'odd' experience listening to what the baffle can produce! You can also play some ordinary music with bass content and be amazed at what comes out of the baffle. It is an 'ear-opening' experience, I should say!
Try it by all means.
Great vibes to all!
Thanks Rudolf.
I am sorry I didn't elaborate on the test setup. It was all kept very simple.
The test baffle was set up in the open verandah and the piezo probe fitted to a gooseneck was touched to the baffle. The monitoring took place in the adjacent room. I played a low-range sweep tone from the computer and an amp feeding the test speaker and listened to the sounds that were coming out of the baffle via the pick-up, monitoring amp and speakers.
It is a 'odd' experience listening to what the baffle can produce! You can also play some ordinary music with bass content and be amazed at what comes out of the baffle. It is an 'ear-opening' experience, I should say!
Try it by all means.
Great vibes to all!
B&W did tests where they pointed the front of the speaker into a sandfilled chamber, and thus listened to what came out of the cabinet walls. At some frequencies the cabinet itself was much louder than the speaker drivers! There is a reference to this in Martin Colloms' book "High performance loudspeakers". Recommended reading for everyone.
OB vibes
Yes Stig, I have a copy of Colloms--had it for a long time, and it sure has given me a lot of inspiration all these years. Like I said, it really felt odd to listen to the disjointed, but very real sound of the baffle.
I remember a friend of mine who did a particularly large cabinet, and his sand-filling was pure art, done after the cabinet was finished and through small holes plugged by wooden bungs after the sand was compacted with bangings and then with some rock music fed into the drivers! We all enjoyed the whole show, including the trip to the beach to collect some sand! Back in the 1980's I did a concrete sub with two 12" drivers and two hand-built PRs for a friend of mine. After the drivers were re-mounted with a couple of gaskets picked up from the kitchen section of the store (they were pressure-cooker gaskets!), the sound was indeed so pure and good.
It is time the driver manufacturers came up with some driver mounting solutions that offered a choice of mounting it by the magnet structure. Shock-mounting vibrating structures is a technique well mastered by the mechanical engineers. Maybe someone also should offer us liquid-filled rubber gaskets that could be stuck to the rims of the drivers so that we could easily decouple the drivers from the baffle board without much effort. In the same vein, I guess the manufacturers should think of putting a damping coating on the driver frames--so much easier than sticking on bits of insulation onto it. I have found that thick double-sided tape (dont remove the covertape on the top!) is a very good damper for frames.
A small 15 cm baffle (in your case, Stig) with an asymmetrically mounted small driver is going to sound far better than your nude larger one, I guess. With a small driver you could go way up too before you needed to XO.
Good vibes to all!
Yes Stig, I have a copy of Colloms--had it for a long time, and it sure has given me a lot of inspiration all these years. Like I said, it really felt odd to listen to the disjointed, but very real sound of the baffle.
I remember a friend of mine who did a particularly large cabinet, and his sand-filling was pure art, done after the cabinet was finished and through small holes plugged by wooden bungs after the sand was compacted with bangings and then with some rock music fed into the drivers! We all enjoyed the whole show, including the trip to the beach to collect some sand! Back in the 1980's I did a concrete sub with two 12" drivers and two hand-built PRs for a friend of mine. After the drivers were re-mounted with a couple of gaskets picked up from the kitchen section of the store (they were pressure-cooker gaskets!), the sound was indeed so pure and good.
It is time the driver manufacturers came up with some driver mounting solutions that offered a choice of mounting it by the magnet structure. Shock-mounting vibrating structures is a technique well mastered by the mechanical engineers. Maybe someone also should offer us liquid-filled rubber gaskets that could be stuck to the rims of the drivers so that we could easily decouple the drivers from the baffle board without much effort. In the same vein, I guess the manufacturers should think of putting a damping coating on the driver frames--so much easier than sticking on bits of insulation onto it. I have found that thick double-sided tape (dont remove the covertape on the top!) is a very good damper for frames.
A small 15 cm baffle (in your case, Stig) with an asymmetrically mounted small driver is going to sound far better than your nude larger one, I guess. With a small driver you could go way up too before you needed to XO.
Good vibes to all!
You missed my point with XO below the dipole peak. A 15 cm baffle has its peak at approx 1700 Hz, and using small drivers on a 15 cm baffle will not change that. Asymmetry might be good for on-axis response, but off-axis response will get worse - my other point is that the nude driver offers very very even off-axis response below the dipole peak.
That being said - excellent sounding results can be had from baffles even when XO above the dipole peak, but in my opinion it is less optimal.
By the way .... I did have a pair of 300 kg (each) sand-filled boxes some 1.5 years ago. Never missed them after I got into dipoles.
Depends on your SPL requirements and how low you want to go. It won't go to 117dB at 16Hz, but (according to Linkwitz's SPL spreadsheets) a nude 15 like AE's OB15 provides output comparable to the H baffled 10s on the Orion at lower cost. Seems a reasonable enough approach. For any given driver selection there's a transition SPL where baffles start to make sense. I'm not aware of any consistent method for rating speakers' maximum SPL but for most of the design options I've looked at baffles become attractive somewhere in the 90 to 95dB range. That's loud enough to cover the majority of operation of most home audio systems.
The USD $49 each, 8 inch, 3.2kg, 2mm xmax Selenium 8W4Ps I'm mostly satsified with are expensive monsters?
The dipole equalization for them's the same sort of shelving filter commonly used for baffle step correction. They don't meet the typical DIY standard for bass reach or peak SPL, but most of that capacity is typically used for that one song or occasional listening session where the volume's turned way up. It's a legitimate, if not often chosen, engineering tradeoff to give up that occasional loud song in exchange for cost and size reduction.Interesting. Do you have any actual data with accelerometers on the baffle to show the difference/improvement?
OB vibes
Stig:
Point taken; I shall keep that in mind when I do my own listening tests. No, I haven't yet tried a nude driver yet. Shall do so at the earliest opportunity so that my bias goes away. Yes, I am also interested in off-axis 'purity' as I have a feeling that it affects imaging-- and I am sold on imaging as I have all along believed that imaging, and not absolute 'fidelity', was the key to reproducing the recorded reality with some semblance of the original.
I have seen some of your work, Stig, and let me just say that I envy your craftsmanship. For that matter I know I am in the midst of great DIYers in this forum!! Yes, I can understand your take on those boxes, sand-filled or not; boxes, ah, that's what we have been having difficulties about remembering ever since we went OB. Sometimes amnesia can be so good!
Loren42:
Sorry to disappoint you- I am not an engineer collecting data. ;-)
I explained my set-up, I think--I was listening 'live' to the baffle output as fed to the monitoring amp by the LP cartridge used as a mechanical 'probe'. The output of the 'normal' baffle was enough to wake the deaf. I was comparing the degree of loudness and roughness of the picked up vibrations, but all I was interested in was to see how could get rid of ALL those unwanted vibrations, whatever their amplitude or mode was. I stopped when things turned out to be pretty silent!! When the piezo pickup was on the decoupled sandwich wooden baffle, there was just a trace of artefacts with above average drive to the test speaker. The driver was an 8" unit with a rating of about 25 W. With the sandwich glass baffle plate, the silence was really uncanny.
My point is that the vibrations were reduced by several orders and I was able to reach a point of very good acceptance. The mounting methods clearly were able to reduce the unwanted vibrations and they were reversible too. Just removing the speaker 'mouth' decoupling, and putting the baffle in close contact with the driver was enough to change the situation to worse. I trust you get my point.
I am happy that with a less than optimized setup, if I was able to achieve such a degree of reduction of unwanted artefacts, a properly engineered setup is sure to be THE solution for such ills.
The drivers were mounted with two aluminium semi-circular brackets on both sides of the 'spine', with some lossy rubber in between, and bolted together. Mechanically also this appeared better as the mounting was close to the centre of gravity of the driver.
Maybe a more mechanically-minded person will analyze correctly the vibration movements here. Earlier when I had mounted the driver with the back of the magnet solidly abutting the spine, I thought at high drive levels, there was some vibration transmitted to the spine, despite its solidity in the front-back plane. (actually I did not 'probe' the spine at this time.) When finally the driver was mounted as above there seemed to be a perceptible improvement. My feeling was that the front-back movements of the magnet structure were being absorbed as heat within the lossy packing without getting directly passed on to the spine. I think I obtained better results all over with a lossy mechanical 'interface'.
I trust that clears the air from my side.
Great vibes to all!
Stig:
Point taken; I shall keep that in mind when I do my own listening tests. No, I haven't yet tried a nude driver yet. Shall do so at the earliest opportunity so that my bias goes away. Yes, I am also interested in off-axis 'purity' as I have a feeling that it affects imaging-- and I am sold on imaging as I have all along believed that imaging, and not absolute 'fidelity', was the key to reproducing the recorded reality with some semblance of the original.
I have seen some of your work, Stig, and let me just say that I envy your craftsmanship. For that matter I know I am in the midst of great DIYers in this forum!! Yes, I can understand your take on those boxes, sand-filled or not; boxes, ah, that's what we have been having difficulties about remembering ever since we went OB. Sometimes amnesia can be so good!
Loren42:
Sorry to disappoint you- I am not an engineer collecting data. ;-)
I explained my set-up, I think--I was listening 'live' to the baffle output as fed to the monitoring amp by the LP cartridge used as a mechanical 'probe'. The output of the 'normal' baffle was enough to wake the deaf. I was comparing the degree of loudness and roughness of the picked up vibrations, but all I was interested in was to see how could get rid of ALL those unwanted vibrations, whatever their amplitude or mode was. I stopped when things turned out to be pretty silent!! When the piezo pickup was on the decoupled sandwich wooden baffle, there was just a trace of artefacts with above average drive to the test speaker. The driver was an 8" unit with a rating of about 25 W. With the sandwich glass baffle plate, the silence was really uncanny.
My point is that the vibrations were reduced by several orders and I was able to reach a point of very good acceptance. The mounting methods clearly were able to reduce the unwanted vibrations and they were reversible too. Just removing the speaker 'mouth' decoupling, and putting the baffle in close contact with the driver was enough to change the situation to worse. I trust you get my point.
I am happy that with a less than optimized setup, if I was able to achieve such a degree of reduction of unwanted artefacts, a properly engineered setup is sure to be THE solution for such ills.
The drivers were mounted with two aluminium semi-circular brackets on both sides of the 'spine', with some lossy rubber in between, and bolted together. Mechanically also this appeared better as the mounting was close to the centre of gravity of the driver.
Maybe a more mechanically-minded person will analyze correctly the vibration movements here. Earlier when I had mounted the driver with the back of the magnet solidly abutting the spine, I thought at high drive levels, there was some vibration transmitted to the spine, despite its solidity in the front-back plane. (actually I did not 'probe' the spine at this time.) When finally the driver was mounted as above there seemed to be a perceptible improvement. My feeling was that the front-back movements of the magnet structure were being absorbed as heat within the lossy packing without getting directly passed on to the spine. I think I obtained better results all over with a lossy mechanical 'interface'.
I trust that clears the air from my side.
Great vibes to all!
Good polar response (off-axis response) is maybe the most important factor for truly great imaging, in my opinion. The same goes for tonal balance. Nude drivers operated below the dipole peak is one way to achive this, but not the only one of course.
Regarding bass and no-baffle. Problem is not sufficient SPL, but distortion. I tried my 21" Beyma nude, and it sure could provide enough SPL down into the 30 Hz range. Problem is that the dipole peak happens at some 350 Hz, where the response starts to fall off 6 dB/oct. To simplyfi, lets say that the response has fallen off 18 dB three octaves below that (~44 Hz). That also means that the upper harmonic distortion components are much louder than the fundamental. The total distortion will be much too high.
In my experiments I found that a nude 21" whan playing 40 Hz, the upper harmonics was the only thing I could hear, the fundamental tone was lost. This gets even worse because of the ear's falling sensitivity with lower frequencies.
Low distortion is the main reason I went for eight 21" and large H-baffles.
Regarding bass and no-baffle. Problem is not sufficient SPL, but distortion. I tried my 21" Beyma nude, and it sure could provide enough SPL down into the 30 Hz range. Problem is that the dipole peak happens at some 350 Hz, where the response starts to fall off 6 dB/oct. To simplyfi, lets say that the response has fallen off 18 dB three octaves below that (~44 Hz). That also means that the upper harmonic distortion components are much louder than the fundamental. The total distortion will be much too high.
In my experiments I found that a nude 21" whan playing 40 Hz, the upper harmonics was the only thing I could hear, the fundamental tone was lost. This gets even worse because of the ear's falling sensitivity with lower frequencies.
Low distortion is the main reason I went for eight 21" and large H-baffles.
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