Bratislav -
You're absolutely right about the brightness of the room, but the effect is mitigated by the size and shape of the space. The living room is HUGE (especially for me since I moved here from a NYC apartment!). Additionally, there are virtually no parallel walls and the only 90 degree angles are between the floor and the walls. Even the ceiling is wierd and canted.
Due to the room shape, I can place the speakers more than 12 feet from any surface other than the floor, so reflections are minimal.
Curtains behind the listening area dampen back reflections.
Werner -
The dynamic driver OB design has many similarities in sound to the quads, but adds the dynamics that (IMHO) are the only critical flaw of the quads.
For anyone designing a dipole sub, have you researched the Celestion 6000? Very interesting design!
You're absolutely right about the brightness of the room, but the effect is mitigated by the size and shape of the space. The living room is HUGE (especially for me since I moved here from a NYC apartment!). Additionally, there are virtually no parallel walls and the only 90 degree angles are between the floor and the walls. Even the ceiling is wierd and canted.
Due to the room shape, I can place the speakers more than 12 feet from any surface other than the floor, so reflections are minimal.
Curtains behind the listening area dampen back reflections.
Werner -
The dynamic driver OB design has many similarities in sound to the quads, but adds the dynamics that (IMHO) are the only critical flaw of the quads.
For anyone designing a dipole sub, have you researched the Celestion 6000? Very interesting design!
Attachments
my heretical consideration
I don´t see any cogent reason to make the OB as thick as possible. In contrast to a boxed speaker there is not much pressure on the baffle. It´s only the movement of the speaker that makes it vibrate.
So if you isolate the baffle from the structure that holds the speaker, you could use any material as thin as statically justifiable. I believe that 1 mm distance between baffle and speaker would hardly reduce the acoustical properties of the baffle.
My conclusion:
Mount the speaker on a stand as rigid as possible and put the baffle in front of it - without any effective mechanical contact.
Any opinions about that?
Rudolf
I don´t see any cogent reason to make the OB as thick as possible. In contrast to a boxed speaker there is not much pressure on the baffle. It´s only the movement of the speaker that makes it vibrate.
So if you isolate the baffle from the structure that holds the speaker, you could use any material as thin as statically justifiable. I believe that 1 mm distance between baffle and speaker would hardly reduce the acoustical properties of the baffle.
My conclusion:
Mount the speaker on a stand as rigid as possible and put the baffle in front of it - without any effective mechanical contact.
Any opinions about that?
Rudolf
stixx
This is a real opportuity. A chance to determine "What an open baffle looks like" The transperent panels others are doing is an obvious option and looks better than I expected. Your designs a quite sophiticated and are beautiful while minimizing the apparent size (although your designs are quite a bit too small for full range) I like # 2 the best, yet it has less tricks. I guess I like simple! Solid panela alsoallow for damping on thhe back-something transperent doesn't
Since they are on your computer, why not scale them about 50% wider to get closer to the required size?
Tcpip
Use the glass. At that price you can't go wrong, and I suspect they wil be bette, not worse.
This is a real opportuity. A chance to determine "What an open baffle looks like" The transperent panels others are doing is an obvious option and looks better than I expected. Your designs a quite sophiticated and are beautiful while minimizing the apparent size (although your designs are quite a bit too small for full range) I like # 2 the best, yet it has less tricks. I guess I like simple! Solid panela alsoallow for damping on thhe back-something transperent doesn't
Since they are on your computer, why not scale them about 50% wider to get closer to the required size?
Tcpip
Use the glass. At that price you can't go wrong, and I suspect they wil be bette, not worse.
Saba baffles
Variac,
thank you for the kind words.
I know that my baffles are on the small side, but for two reasons: first I couldn't live with a baffle of the size of a door in my livingroom and I am considering the use of a subwoofer anyway, and second does the Saba's model quite well in Thorsten's spreadsheet, having a measured Qts of beyond 1.
With other drivers (like the expensive Supravox'es) my baffle definitely will be too small......
Later
Oliver
Variac,
thank you for the kind words.
I know that my baffles are on the small side, but for two reasons: first I couldn't live with a baffle of the size of a door in my livingroom and I am considering the use of a subwoofer anyway, and second does the Saba's model quite well in Thorsten's spreadsheet, having a measured Qts of beyond 1.
With other drivers (like the expensive Supravox'es) my baffle definitely will be too small......
Later
Oliver
Oliver, you are right, the open baffle with sub is a good way to go.
And a baffle the size you show will be reproducing most of the music anyway.
Similar to the Baszilla but the midrange on yours might be going a a lot lower-what is the frequency you think you will be crossing to the sub?
Mark
And a baffle the size you show will be reproducing most of the music anyway.
Similar to the Baszilla but the midrange on yours might be going a a lot lower-what is the frequency you think you will be crossing to the sub?
Mark
Glass baffles
Check these out. The builder, on another forum, said the glass was a real pain to work with but, in his opinion, the sound is better than plastic. He went to extremes to reduce vibrations and stored energy.
http://www.gwabsynect.com/laglass/index.htm
Check these out. The builder, on another forum, said the glass was a real pain to work with but, in his opinion, the sound is better than plastic. He went to extremes to reduce vibrations and stored energy.
http://www.gwabsynect.com/laglass/index.htm
An externally hosted image should be here but it was not working when we last tested it.
Re: Glass baffles?
Konnichiwa,
In some cases, yes. In most - no. But you can (like I did) wire an additional T-Network into the speaker level inputs to get added EQ and use the variable stuff to do the rest. Still not ideal for most Dipole Subs though.
From my general experiences using glass as acoustic and/or structural material, excellent sounding and very breakable. Two attemps shipping me glass baffles ended up with the insurance paying, I gave up. Plasic breaks a lot less and sounds much better than having NO baffle as it's broken again....
I suspect laminated, tempered bullet proof glass would be fine, if you have long green.
Sayonara
Konnichiwa,
Werner said:
In some cases, yes. In most - no. But you can (like I did) wire an additional T-Network into the speaker level inputs to get added EQ and use the variable stuff to do the rest. Still not ideal for most Dipole Subs though.
tcpip said:
From my general experiences using glass as acoustic and/or structural material, excellent sounding and very breakable. Two attemps shipping me glass baffles ended up with the insurance paying, I gave up. Plasic breaks a lot less and sounds much better than having NO baffle as it's broken again....
I suspect laminated, tempered bullet proof glass would be fine, if you have long green.
Sayonara
Sjef -
Sorry for the typo. The link is
www.audiocircle.com
Stixx -
Your designs are stunning. I am rather partial to the first one without the straight lines, though I've recently learned the hard way that compound curves are easier to make on the 'puter then in the shop...
One potential problem I see with the design is that the drivers are centered on the baffle. Ideally, you want to offset the driver to minimize and distribute the resonance peaks.
ldsg.snippets.org/AUDIO/LIBRARY/phi.html
I'm a strong believer in augmenting OB designs with separate subs, but unless you want to dipole the sub, you will lose a lot of the dipole bass magic with such a narrow baffle. You want them to go low enough that the sub is just that, not an separate woofer.
Rudolf -
I think that thicker is better. I certainly got better results going from 1/4 inch to 1/2 inch thick baffle material, most of which I attribute to increase mass and rigidity
I don't think you want to leave a gap, even of just 1mm. You wouldn't build a box speaker like that would you?
I'm no expert, but the force that vibrates the baffle is not the mass of the moving cone so much as the positive and negative pressure differentials between the back and front faces. De-coupling the driver from the baffle will only reduce the panel vibrations so much. Should be easy enough to test with a cardboard baffle...
All -
Can someone explain me how to do those nifty quote thingies...?
Sorry for the typo. The link is
www.audiocircle.com
Stixx -
Your designs are stunning. I am rather partial to the first one without the straight lines, though I've recently learned the hard way that compound curves are easier to make on the 'puter then in the shop...
One potential problem I see with the design is that the drivers are centered on the baffle. Ideally, you want to offset the driver to minimize and distribute the resonance peaks.
ldsg.snippets.org/AUDIO/LIBRARY/phi.html
I'm a strong believer in augmenting OB designs with separate subs, but unless you want to dipole the sub, you will lose a lot of the dipole bass magic with such a narrow baffle. You want them to go low enough that the sub is just that, not an separate woofer.
Rudolf -
I think that thicker is better. I certainly got better results going from 1/4 inch to 1/2 inch thick baffle material, most of which I attribute to increase mass and rigidity
I don't think you want to leave a gap, even of just 1mm. You wouldn't build a box speaker like that would you?
I'm no expert, but the force that vibrates the baffle is not the mass of the moving cone so much as the positive and negative pressure differentials between the back and front faces. De-coupling the driver from the baffle will only reduce the panel vibrations so much. Should be easy enough to test with a cardboard baffle...
All -
Can someone explain me how to do those nifty quote thingies...?
Variac,
the baffles should go down into the high 60's, so crossing the (dipole-) sub at little lower than that should give good results.
But then.....a dipole sub is another project......my current sub is a closed design with an Alumapro Alchemy driver which should also integrate quite well.
Eric,
thank YOU for the kind words.....stunning is what came to my mind when I saw your baffles....I just love solid hardwood!
Those compound curves can be done quite easily on any surface with Scotch tape of at least 15mm width.....just keep trying until you are satisfied with the shape of your curve!
Offsetting drivers on the panel has to be considered, for esthetical reasons they ended up in the middle of the baffle.
I also think that both drivers are sitting too high....?
Oliver
the baffles should go down into the high 60's, so crossing the (dipole-) sub at little lower than that should give good results.
But then.....a dipole sub is another project......my current sub is a closed design with an Alumapro Alchemy driver which should also integrate quite well.
Eric,
thank YOU for the kind words.....stunning is what came to my mind when I saw your baffles....I just love solid hardwood!
Those compound curves can be done quite easily on any surface with Scotch tape of at least 15mm width.....just keep trying until you are satisfied with the shape of your curve!
Offsetting drivers on the panel has to be considered, for esthetical reasons they ended up in the middle of the baffle.
I also think that both drivers are sitting too high....?
Oliver
Erik Wrote:
There are many people who have built OBs with wings on leather hinges. Lots of gap between main baffle and wings there. And no complaints yet.
But you could always fill the gap with rubberfoam.
I have done that, even with plywood. I used a VERY narrow bafffle with the speaker mounted on it. Real bad vibrations. I put wings on the baffle to get the required width and isolated these wings mechanically from the narrow baffle. Vibration of the wings was almost undiscernible.
IMHO there is not much sense in transferring the principles of sealed box construction to open baffles.
Rudolf
There are many people who have built OBs with wings on leather hinges. Lots of gap between main baffle and wings there. And no complaints yet.
But you could always fill the gap with rubberfoam.
I have done that, even with plywood. I used a VERY narrow bafffle with the speaker mounted on it. Real bad vibrations. I put wings on the baffle to get the required width and isolated these wings mechanically from the narrow baffle. Vibration of the wings was almost undiscernible.
IMHO there is not much sense in transferring the principles of sealed box construction to open baffles.
Rudolf
I think Rudolf make some good points. In order to move the open baffle designs ahead, (and isn't this cool, we ARE probably working to move ahead the state of the art in open baffle) we need to determine what matters and what doesn't- not use ideas from other designs without thinking them through.
First, The gaps. How wide a gap can you have between panels?
This must be frequency dependent, right? Can someone come up with a theory and graph showing permissible gaps for different frequencies? One help in allowing gaps is that most tweeters are sealed on the back, so aren't affected by the baffle at all.
Lots of great design possibilities are possible with gaps. I especially am considering 2 doors that cover the drivers in a baffle that is quite narrow. When it is time to play, open the doors and viola: the drivers are exposed, and the baffle is twice as wide! Huge SAF
Second, isolating the baffle from the driver seem to be a very good idea. I believe that even isolated, the baffle will have a tendency to vibrate a bit, but an order of magnitude less that if they are connected! A huge surface like a baffle doesn't have to move very much to affect the sound a lot! In fact maybe that's where some (a lot? ) of the bass comes from! Of course-that gap thing again- how close does the driver perimeter have to be to the hole in the baffle?
Third, Even if you mount the drivers on the centerline of the baffle they are mounted off center in the baffle. The distance to the floor is a free lunch which I think is one of the main reasons these smaller baffles work. It is in effect infinate since the floor keeps sound from short circuiting in that direction. The distance from the top of the baffle is usually different from the distance to the sides, so the huge dips in response due to the drivers being in the exact center of the baffle aren't going to happen. I think that this also means to mount the drivers as low as possible, maybe tilting the baffle back as some have done to point them at a seated position. This way you get a much wider baffle on the top and the bottom is stil blocked by the floor
That's about it....
Mark
First, The gaps. How wide a gap can you have between panels?
This must be frequency dependent, right? Can someone come up with a theory and graph showing permissible gaps for different frequencies? One help in allowing gaps is that most tweeters are sealed on the back, so aren't affected by the baffle at all.
Lots of great design possibilities are possible with gaps. I especially am considering 2 doors that cover the drivers in a baffle that is quite narrow. When it is time to play, open the doors and viola: the drivers are exposed, and the baffle is twice as wide! Huge SAF
Second, isolating the baffle from the driver seem to be a very good idea. I believe that even isolated, the baffle will have a tendency to vibrate a bit, but an order of magnitude less that if they are connected! A huge surface like a baffle doesn't have to move very much to affect the sound a lot! In fact maybe that's where some (a lot? ) of the bass comes from! Of course-that gap thing again- how close does the driver perimeter have to be to the hole in the baffle?
Third, Even if you mount the drivers on the centerline of the baffle they are mounted off center in the baffle. The distance to the floor is a free lunch which I think is one of the main reasons these smaller baffles work. It is in effect infinate since the floor keeps sound from short circuiting in that direction. The distance from the top of the baffle is usually different from the distance to the sides, so the huge dips in response due to the drivers being in the exact center of the baffle aren't going to happen. I think that this also means to mount the drivers as low as possible, maybe tilting the baffle back as some have done to point them at a seated position. This way you get a much wider baffle on the top and the bottom is stil blocked by the floor
That's about it....
Mark
If the leather hinge extends the entire length, then there is no gap. If not, then you're loosing the effectiveness of the wings. I've yet to see a design like this. Can you refer me to one of these "many people"?
PHY-HP publishes recommended plan for a large folding baffle. The plan specifies the use of (difficult to find and expensive) piano hinges. This is to seal the folds.
Foam rubber sealing the gaps is a good direction to start thinking. You want to connect the panels with a material that is compliant enough to fold, tight enough prevent air leakage, yet firm enough to not vibrate sympathetically with the the pressure differentials.
I have tried this as well and concur that the vibrations on the wings was minimal. Unfortunately, so was the bass extention.
Why? Are the laws of physics suspended because we're talking about OB rather than sealed or ported boxes? If you build a leaky sealed box, you get lousy bass. Same concept. Cancellation.
Agreed that the paradigm shift to OB designs requires scrutiny of our assumptions. It does not mean we should throw them out, but rather we should examine how they effect an open baffle design. For example, the internal relections of a box would not initially seem to effect OB's, but when you add wings, that is exactly what you get.
Another example is the driver offset on the baffle. In a sealed box the issue is one of defraction as the soundwaves transfer from 1/2 space to full space. Irrational number ratios in the offsets are effective in smoothing out the response. With OB speakers, the issue is the Fe point where cancellation begins. Interesting enough, the same baffle concepts work to smooth out the dipole response and minimize the effect of the Fp.
I believe that gaps can positively effect the response of an OB speaker, but not because they are insignificant.
Naw. I don't think this is right. I'm a little rusty on my high school physics so please excuse me if I try an analogy.
This week I was watching the storm surge waves from Izzy passing through a breakwater. While the relative strength of the wavefronts was diminished by the narrow opening, the waves emerged intact. The reason why is that there was water on both sides of the wall. What was passing through was energy.
Don't think in terms of a 1 meter wavelength not fitting though a 1 cm gap. The air doesn't pass through, only the energy does. The smallest unsealed gap will still contain air molecules quite capable of transferring energy (though it may be reduced as my analogy would indicate).
Variac, one way to conceptualize the baffle effect is the figuratively slice up your driver like a pie. For each section the sound will follow a path around the baffle to the back of the cone. With any design other than a suspended, circular, centered baffle, the path length for the sections will be different. If the bottom of the baffle is secured to the floor, those sections will effectively act like infinite baffles and will not have cancellation effects (which is why most charts seem to underestimate the bass extention of theoretical baffles). If you sum (in some fashion) the response of all the pie slices you get the response of the driver in the baffle.
The goal is to try to minimize the number of slices that have equal length. Equal lengths will reinforce the Fe point for those sections. Uneven lengths will spread out the Fe point resulting in a smoother overall response. If you have a narrow baffle with the drivers centered, then you are creating duplicate Fe points for most of the slices. Using standard offset theory (as would apply to sealed boxes) has the effect of reducing to a minimum the reinforcements of the resonance peaks.
If you are going with a winged concept, you can do an end-run by creating unequal length wings around a symetrical baffle. This will provide the same benefits as a driver offset, and also spread out the inevitable pipe resonances you will get with the wings.
I dunno. Does this make sense?
Here is an open baffle with a crack done by a rather knowledgable audio fellow.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=9557&perpage=15&pagenumber=26
If you read ahead a few posts, you will see that I asked him about how big the gap can be. I agree that your analogy about holes is quite possible, I do know that sound can pass through holes in a lens-like manner. But I think we need to know from some one that can actually state what works and what doesn't.
Probably the best resolution would be an experiment where the response of a baffle is measured, then a gap is uncovered and it is remeasured. In any case ,as you yourself point out, the problem of craks caused by folding sections is easily solved by piano hinges, flexible plastic continuous hinges, or a membrane between the hinge and the baffle. A folding baffle could be quite useful in developing practical open baffle speakers, that is why it is being discussed here.
Yes it is preferable to have a large variety of lengths, but in fact even with the drivers in line, you are quite far from a centered driver.
To do quotes: click on the Quote button, then cut and paste the text you want t o have as a quote into the window that appears.
Mark
http://www.diyaudio.com/forums/showthread.php?s=&threadid=9557&perpage=15&pagenumber=26
If you read ahead a few posts, you will see that I asked him about how big the gap can be. I agree that your analogy about holes is quite possible, I do know that sound can pass through holes in a lens-like manner. But I think we need to know from some one that can actually state what works and what doesn't.
Probably the best resolution would be an experiment where the response of a baffle is measured, then a gap is uncovered and it is remeasured. In any case ,as you yourself point out, the problem of craks caused by folding sections is easily solved by piano hinges, flexible plastic continuous hinges, or a membrane between the hinge and the baffle. A folding baffle could be quite useful in developing practical open baffle speakers, that is why it is being discussed here.
Yes, I agree, I think that this is exactly what I was saying, no?
Yes it is preferable to have a large variety of lengths, but in fact even with the drivers in line, you are quite far from a centered driver.
This brings up another point that I mentioned. Perhaps some of the bass is coming from the baffle itself vibrating. Too bad you didn't try a foam gasket around the driver perifery to see if your bass came back. That way you would know if the diminished bass is from the crack around the driver or because the baffle isn't vibrating.
To do quotes: click on the Quote button, then cut and paste the text you want t o have as a quote into the window that appears.
Mark
Vibrating of the baffle isn't always a bad thing. If you can keep it under control it can also help the performance of the driver. Audio Note for instance uses this principle for years in their speakers and I can't say that they are bad sounding. Also mr. Salabert, the founder of Phy-HP has experimented a lot with controlled resonances of enclosures for his speakers.
There are also four different compagnies who make speakers wth the Phy-HP units according to this principle.
A couple of weeks ago I visited the Dutch dealer of Phy-HP and listened to this enclosures. Although the cabinet wasn't totally my cup of tea I was convinced that using the right kind of wood (or other material) for an open baffle could help a lot. He uses mainly Sitca Spruce wich is widely used as material for building guitars and chello's etc. because of its good sound. The speed of sound in sitca spruce is up to ten times higher than in multiplex for instance so the resonance of the baffle is not delayed that much wich imho is much less harmfull than delayed resonances.
I'm still thinking of his proposal to make a baffle for me wich is constructed of 7mm sitca spruce with braces on the back. Kinda like a sound bottom of a piano. The baffle will be mounted on a stand wich is constructed to the speaker itself, not to the baffle.
Although this baffle will colour the sound a bit it is still much less coloured than a sealed box. I've tried the Phy on a very rigid baffle (40mm MDF) but like it a lot more on a thin 12 mm multiplex baffle. It's got a lot more body.
Every speaker has some kind of colouration it's just a matter of getting it under control the way you like it.
There are also four different compagnies who make speakers wth the Phy-HP units according to this principle.
A couple of weeks ago I visited the Dutch dealer of Phy-HP and listened to this enclosures. Although the cabinet wasn't totally my cup of tea I was convinced that using the right kind of wood (or other material) for an open baffle could help a lot. He uses mainly Sitca Spruce wich is widely used as material for building guitars and chello's etc. because of its good sound. The speed of sound in sitca spruce is up to ten times higher than in multiplex for instance so the resonance of the baffle is not delayed that much wich imho is much less harmfull than delayed resonances.
I'm still thinking of his proposal to make a baffle for me wich is constructed of 7mm sitca spruce with braces on the back. Kinda like a sound bottom of a piano. The baffle will be mounted on a stand wich is constructed to the speaker itself, not to the baffle.
Although this baffle will colour the sound a bit it is still much less coloured than a sealed box. I've tried the Phy on a very rigid baffle (40mm MDF) but like it a lot more on a thin 12 mm multiplex baffle. It's got a lot more body.
Every speaker has some kind of colouration it's just a matter of getting it under control the way you like it.
Interesting information.
I agree that the baffle vibrating could possibly help the sound,
It would certainly change the sound.
I just think it is important to determine how much
effect a vibrating baffle contributes. It seems that some of you are saying that without a resonant baffle, the bass is deficient.
So, when it comes time to design a baffle, it would be useful to know if we are trying for maximum rigidity or need to tune it to produce bass!
I agree that the baffle vibrating could possibly help the sound,
It would certainly change the sound.
I just think it is important to determine how much
effect a vibrating baffle contributes. It seems that some of you are saying that without a resonant baffle, the bass is deficient.
So, when it comes time to design a baffle, it would be useful to know if we are trying for maximum rigidity or need to tune it to produce bass!
Hi,
Surely that can not be the case.
I think that what was meant was that if it's going to resonate anyway then it be better a pleasant one to the ear then one that detracts from the enjoyment of music.
This is true for boxes too of course.
Personally I don't understand why you would want the added colourations of the baffle which is why I showed the Supravox design which uses a damped sandwich for the main panel.
Damped mounting of the speaker to the panel is even more odd since then you'd really lose bass output and fine detail in the proccess.
Any good book on the history of speaker design such as Biggs will show the basic maths and principles of OBSs.
Hope this helps,
Surely that can not be the case.
I think that what was meant was that if it's going to resonate anyway then it be better a pleasant one to the ear then one that detracts from the enjoyment of music.
This is true for boxes too of course.
Personally I don't understand why you would want the added colourations of the baffle which is why I showed the Supravox design which uses a damped sandwich for the main panel.
Damped mounting of the speaker to the panel is even more odd since then you'd really lose bass output and fine detail in the proccess.
Any good book on the history of speaker design such as Biggs will show the basic maths and principles of OBSs.
Hope this helps,
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