you are quite right, wunhuanglo
I once again looked up Linkwitz´explanation of edge diffraction at
http://www.woodartistry.com/linkwitzlab/faq.htm#Q8
And yes, I see, it is somehow the opposite sides of the same coin. To get it clearer for myself, I simulated the same baffle for closed box (green) and OB (red) in "EDGE". (driver vertically centered on the baffle, so response is far from optimal)
Down from 700 Hz the green curve would describe what is traditionally named baffle step reponse (at least where BSD compensation is aimed at), the red curve is the dipole roll-off. Above 700Hz it´s baffle edge diffraction. Interesting that it is much heavier for the Ob than for the closed box.
Thank you for making me think again
Rudolf
I once again looked up Linkwitz´explanation of edge diffraction at
http://www.woodartistry.com/linkwitzlab/faq.htm#Q8
And yes, I see, it is somehow the opposite sides of the same coin. To get it clearer for myself, I simulated the same baffle for closed box (green) and OB (red) in "EDGE". (driver vertically centered on the baffle, so response is far from optimal)
Down from 700 Hz the green curve would describe what is traditionally named baffle step reponse (at least where BSD compensation is aimed at), the red curve is the dipole roll-off. Above 700Hz it´s baffle edge diffraction. Interesting that it is much heavier for the Ob than for the closed box.
Thank you for making me think again
Rudolf
Attachments
Baffle step and dipole baffle size roll-off are not the same thing. Baffle step, where the sound starts to wrap around the baffle, generally occurs at a much higher frequency. It occurs due to how different frequencies disperse. The dipole roll off occurs at the point where once the sound gets around the baffle and it is early enough in the occurance of the sound wave that the front and back waves are still directly out of phase and cancel each other out. This is wavelength and distance dependent.
At least that's how I understand it in layman's terms.
At least that's how I understand it in layman's terms.
Its the Jordan JX92Sthen_dude said:
yes, see attachment
The Xbaffle simulation told me that baffle step is around 200 Hz for the Jordan driver, because the baffle is asymentric and relativly large
I use 4th order Linkwitz-Riley, I think Q=0,7 as recommended, at 160 Hz.
Equalization is done via shelving lowpass between 100Hz and 30 Hz. Additionally I needed a first order lowpass at 100 Hz to eliminate booming in the area of 120 to 200 Hz.
This stuff is done in a diy active crossover.
Is there any special effect in using ribbons in the area over 12kHz? For my feeling the effect of a supertweeter is audible but I cannot imagine, that in this area it makes any difference except for the costs.
regards
stephan
Attachments
XLBaffle.xls
Evening All,
I have been toying with the open baffle idea for quite a while now and wanted to give it a go again ... but questions arise.
1. Using the xlbaffle.xls program by Thoersten Loerch:
a) Does "Height above Floor" mean height of the driver above the floor, or height of the bottom edge of the baffle above floor?
b) Does the "distance rear wall" and "distance side wall" refer to the position of the driver or the nearest edge of the baffle from the wall?
c) There appears to be no "sensitivity" input for the speaker, but the program can give a maximum sound level. How is this possible?
2. I recently made myself a boxed subwoofer with two of the following drivers:
Jaycar CW 2145:
<<This 300mm driver has a black woven carbon fibre cone and rubber surround a high temperature Kapton voice coil and a huge magnet weighing 1.412 kilograms. Specifications:-
Nom impedance: 8ohms
Power handling 200watts RMS
Frequency range: 25Hz - 3500Hz
Sensitivity: 93dB 1watt 1metre
Voice Coil Resistance (Re): 6.9ohms
Resonant frequency (fs): 21.3Hz
Mechanical Q factor (Qms): 8.709
Electrical Q factor (Qes): 0.364
Total Q factor (Qts): 0.350
Equivalent Volume (Vas): 230Lt
Cone Area (square meters): 0.0494 >> End of Quote.
While I was waiting for the box to be finished at my snail pace,
I mounted one of the drivers into the middle of a interior door (approx 2m * 0.8m) that I was about to throw out, (mounted the door on some wooden stands about 600mm from the rear wall and 1.5 m from the end wall) hooked up a 300 W subwoofer amplifier (crossover at 120 Hz built in) and a sine wave generator. Swept the signal through 20 to 150 Hz and there was very little sound AT ALL coming out of the "baffle" at these levels. There was however spectacular cone movement, especially around Fs when it was positively frightening! But why no sound? I was wondering if isome disappeared into the cavity of the door, but this seemed unlikely to be the entire reason, especially given that when I plugged the figures into Xlbaffle.xls it appears that there should have been quite acceptable amounts of sound, at least up around the 100 - 120 Hz frequencies, despite the lowish Qts of the driver.
I can accept that perhaps my perception of sound level could be HIGHLY flawed, but it all seems quite worrying to a beginner. (You chappies and chappesses seem quite able to stick a reasonable midrange speaker into a piece of cardboard and make it work, and then refine it to world-beating standard.)
a) What could be going on with my first ever totally failed open baffle?
b) I need encouragement in this please, or should I just lash out and make a Linkwitz Phoenix or Orion, having let Siegfried worry about the details, and hang the expense?
Best regards,
George Boles.
Evening All,
I have been toying with the open baffle idea for quite a while now and wanted to give it a go again ... but questions arise.
1. Using the xlbaffle.xls program by Thoersten Loerch:
a) Does "Height above Floor" mean height of the driver above the floor, or height of the bottom edge of the baffle above floor?
b) Does the "distance rear wall" and "distance side wall" refer to the position of the driver or the nearest edge of the baffle from the wall?
c) There appears to be no "sensitivity" input for the speaker, but the program can give a maximum sound level. How is this possible?
2. I recently made myself a boxed subwoofer with two of the following drivers:
Jaycar CW 2145:
<<This 300mm driver has a black woven carbon fibre cone and rubber surround a high temperature Kapton voice coil and a huge magnet weighing 1.412 kilograms. Specifications:-
Nom impedance: 8ohms
Power handling 200watts RMS
Frequency range: 25Hz - 3500Hz
Sensitivity: 93dB 1watt 1metre
Voice Coil Resistance (Re): 6.9ohms
Resonant frequency (fs): 21.3Hz
Mechanical Q factor (Qms): 8.709
Electrical Q factor (Qes): 0.364
Total Q factor (Qts): 0.350
Equivalent Volume (Vas): 230Lt
Cone Area (square meters): 0.0494 >> End of Quote.
While I was waiting for the box to be finished at my snail pace,
I mounted one of the drivers into the middle of a interior door (approx 2m * 0.8m) that I was about to throw out, (mounted the door on some wooden stands about 600mm from the rear wall and 1.5 m from the end wall) hooked up a 300 W subwoofer amplifier (crossover at 120 Hz built in) and a sine wave generator. Swept the signal through 20 to 150 Hz and there was very little sound AT ALL coming out of the "baffle" at these levels. There was however spectacular cone movement, especially around Fs when it was positively frightening! But why no sound? I was wondering if isome disappeared into the cavity of the door, but this seemed unlikely to be the entire reason, especially given that when I plugged the figures into Xlbaffle.xls it appears that there should have been quite acceptable amounts of sound, at least up around the 100 - 120 Hz frequencies, despite the lowish Qts of the driver.
I can accept that perhaps my perception of sound level could be HIGHLY flawed, but it all seems quite worrying to a beginner. (You chappies and chappesses seem quite able to stick a reasonable midrange speaker into a piece of cardboard and make it work, and then refine it to world-beating standard.)
a) What could be going on with my first ever totally failed open baffle?
b) I need encouragement in this please, or should I just lash out and make a Linkwitz Phoenix or Orion, having let Siegfried worry about the details, and hang the expense?
Best regards,
George Boles.
I remember connecting up my first subs and thinking that they were not producing much sound! That's how it is at those low frequencies.
Further up the frequency range is a different matter!
I recommend the open baffle concept and if you can afford to then I would say yes, go for the Orions! Otherwise, find a 'full-range' driver and place that on a baffle about four by two feet and just experiment.
Unfortunately, if you have boxed subs (other than TL's) you will find them a bit 'slow' compared to the open baffles.
Further up the frequency range is a different matter!
I recommend the open baffle concept and if you can afford to then I would say yes, go for the Orions! Otherwise, find a 'full-range' driver and place that on a baffle about four by two feet and just experiment.
Unfortunately, if you have boxed subs (other than TL's) you will find them a bit 'slow' compared to the open baffles.
George,
Welcome to the world of OB. Your results are why I say forget the spreadsheets. Only experimentation will tell you true results. For there to be no bass at 100hz, you must have been standing at the side, not in front. At the side there won't be bass even with 10ft wide baffles. Try it again with the door baffle on the floor. There will be a huge difference between on its side on the floor and on its end.
You should note that the Orions have 2 drivers for bass in each speaker, the effective baffle width is much wider than your door due to the sides in the bass section, and the woofers are much closer to the floor. Each of these have a tremendous effect on the amount of bass at the listening position.
Welcome to the world of OB. Your results are why I say forget the spreadsheets. Only experimentation will tell you true results. For there to be no bass at 100hz, you must have been standing at the side, not in front. At the side there won't be bass even with 10ft wide baffles. Try it again with the door baffle on the floor. There will be a huge difference between on its side on the floor and on its end.
You should note that the Orions have 2 drivers for bass in each speaker, the effective baffle width is much wider than your door due to the sides in the bass section, and the woofers are much closer to the floor. Each of these have a tremendous effect on the amount of bass at the listening position.
Re: XLBaffle.xls
Konnichiwa,
XLbaffle assumes ALLWAYS a baffle reaching to the floor. The hight above floor refers to the driver center.
Room walls are referred to. Xlbaffle assumes a rectangular baffle with optimised (golden ratio) left/right placement of the driver.
Actually there is, indirectly, the SPL is derived from the Thiele Small parameters but as such only valid around driver resonance and does not account for rising midrange SPL as found in some drivers etc.
Could it be that door tends to flex and does not provide a stiff surface, plus possible air leakage?
Also, a quick check in XLBaffle suggests that the driver would make a VERY high excursion at low frequencies.
Did you try playing some music?
How did you measure the SPL response? directly on axis (remember, dipoles are highly directional EVEN AT THEIR LOWEST FREQUENCY).
Sayonara
Konnichiwa,
GeorgeBoles said:
XLbaffle assumes ALLWAYS a baffle reaching to the floor. The hight above floor refers to the driver center.
GeorgeBoles said:
Room walls are referred to. Xlbaffle assumes a rectangular baffle with optimised (golden ratio) left/right placement of the driver.
GeorgeBoles said:
Actually there is, indirectly, the SPL is derived from the Thiele Small parameters but as such only valid around driver resonance and does not account for rising midrange SPL as found in some drivers etc.
GeorgeBoles said:
Could it be that door tends to flex and does not provide a stiff surface, plus possible air leakage?
Also, a quick check in XLBaffle suggests that the driver would make a VERY high excursion at low frequencies.
Did you try playing some music?
How did you measure the SPL response? directly on axis (remember, dipoles are highly directional EVEN AT THEIR LOWEST FREQUENCY).
Sayonara
Encouragement Received, But more Questions!!
Many thanks for your responses. They make sense and back up some of my suspicions.
1. My door was on its side, and touching the floor (all except for about 12 mm), but it was hollow and I imagine the mounting was a bit floppy, so perhaps a lot of sound was lost that way.
2. "Measurment" of sound level was done with a "Mark I Tympano-Cochleometer" (much like a Mark I Optico-Retinometer in the visual realm.)
3. I am still unclear about "distance rear wall" and "distance side wall". Do these distances relate to the DRIVER or the EDGE OF THE BAFFLE from the adjacent walls?
4. To work out the effective baffle length in the arrangement in the Orion, do you just add up all the wall lengths, and is the width just the height of the box, or is there a little bit extra for the depth that the drivers are placed into the box, or is it more complicated than that?? (Is this a "W" design?)
With thanks and best regards,
George.
Many thanks for your responses. They make sense and back up some of my suspicions.
1. My door was on its side, and touching the floor (all except for about 12 mm), but it was hollow and I imagine the mounting was a bit floppy, so perhaps a lot of sound was lost that way.
2. "Measurment" of sound level was done with a "Mark I Tympano-Cochleometer" (much like a Mark I Optico-Retinometer in the visual realm.)
3. I am still unclear about "distance rear wall" and "distance side wall". Do these distances relate to the DRIVER or the EDGE OF THE BAFFLE from the adjacent walls?
4. To work out the effective baffle length in the arrangement in the Orion, do you just add up all the wall lengths, and is the width just the height of the box, or is there a little bit extra for the depth that the drivers are placed into the box, or is it more complicated than that?? (Is this a "W" design?)
With thanks and best regards,
George.
Linkwitz Orions
Good evening to you all again,
The reasons I haven't jumped in and bought the Orions are:
1. They are not cheap: but quality of components and design do have a cost which I am prepared to pay. Certainly though we are not looking at a"disposable if I don't like it" sort of product at these prices, are we! (When I bought my first "hifi" speaker cable, I was told that if it didn't work, I could use it to tie up the dog it was so cheap.)
2. I am currently living with some old Carver speakers (no model identifiers on them that I can see) on loan at present which have a 4 foot long plastic film/aluminium midrange-tweeter, in an open baffle type configuration, with three pretty borderline woofers arranged alongside, also open baffle. The treble and mid-range clarity is better than anything I have EVER heard in my life, which had consisted of dome tweeters of various configurations (B&W 802 and 805, Mirage something or others, and the Titanium one which Focal made that went into their BIG expensive systems ... mind, you, the last one was pretty good). The mid-range and treble sound is actually so good in its naturalness and in the sound stage, that I find it hard to imagine anything as realistic or better. (The L to R sound stage on the B&W 802's was better by a long way, but overall much more fatiguing to the ear.)
a.) Is the SEAS Millennium in the Orions capable of performing as well as a 12 year old magnetic planar driver?
b.) Is it the tweeter/mid-range driver itself or the open baffle of these designs which provides the magic? (Don't you just love questions like that?)
Because if there is a huge difference, I might be out there making my own design up ... hmmm, that is a big task.
3. A fair bit of construction of amplifiers (8 channels!), but it might all be worth it. I imagine that I could pull it off for less than $1000 Australian using Rod Elliott's designs, a bunch of P3a's would suit, I think. http://sound.westhost.com/project3a.htm
Best Regards,
George
Good evening to you all again,
The reasons I haven't jumped in and bought the Orions are:
1. They are not cheap: but quality of components and design do have a cost which I am prepared to pay. Certainly though we are not looking at a"disposable if I don't like it" sort of product at these prices, are we! (When I bought my first "hifi" speaker cable, I was told that if it didn't work, I could use it to tie up the dog it was so cheap.)
2. I am currently living with some old Carver speakers (no model identifiers on them that I can see) on loan at present which have a 4 foot long plastic film/aluminium midrange-tweeter, in an open baffle type configuration, with three pretty borderline woofers arranged alongside, also open baffle. The treble and mid-range clarity is better than anything I have EVER heard in my life, which had consisted of dome tweeters of various configurations (B&W 802 and 805, Mirage something or others, and the Titanium one which Focal made that went into their BIG expensive systems ... mind, you, the last one was pretty good). The mid-range and treble sound is actually so good in its naturalness and in the sound stage, that I find it hard to imagine anything as realistic or better. (The L to R sound stage on the B&W 802's was better by a long way, but overall much more fatiguing to the ear.)
a.) Is the SEAS Millennium in the Orions capable of performing as well as a 12 year old magnetic planar driver?
b.) Is it the tweeter/mid-range driver itself or the open baffle of these designs which provides the magic? (Don't you just love questions like that?)
Because if there is a huge difference, I might be out there making my own design up ... hmmm, that is a big task.
3. A fair bit of construction of amplifiers (8 channels!), but it might all be worth it. I imagine that I could pull it off for less than $1000 Australian using Rod Elliott's designs, a bunch of P3a's would suit, I think. http://sound.westhost.com/project3a.htm
Best Regards,
George
Re: Encouragement Received, But more Questions!!
"distance rear wall" and "distance side wall" relate to the DRIVER center. If the wavelength of a frequency is four times the "distance rear wall" or "distance side wall" these frequencies are attenuated. If the wavelength is double the distance these frequencies are amplfied. XLbaffle takes care of that.
XLbaffle is not particularly suited to calculate a H or W baffle like in the Orion. The most (and only?) important dimension of a H or W baffle is the depth. You should look up the how-abouts at http://www.linkwitzlab.com/models.htm#B and #C
Rudolf
George,GeorgeBoles said:
"distance rear wall" and "distance side wall" relate to the DRIVER center. If the wavelength of a frequency is four times the "distance rear wall" or "distance side wall" these frequencies are attenuated. If the wavelength is double the distance these frequencies are amplfied. XLbaffle takes care of that.
XLbaffle is not particularly suited to calculate a H or W baffle like in the Orion. The most (and only?) important dimension of a H or W baffle is the depth. You should look up the how-abouts at http://www.linkwitzlab.com/models.htm#B and #C
Rudolf
Re: Linkwitz Orions
Konnichiwa,
A potentially quite useful device, but not in order to generate a curve that can be compared to simulations.
In all my various spreadsheet calculators I always assume the distances to the center of the sound source (driver center), as was also remarked by Rudolph.
You cannot even get a good approximation of M/W/H baffles using my calaculator. They are complex resonant systems not ameanable to easy analysis using my spreadsheets and even the Formulas Linkwitz provides are not terribly accurate.
No.
It is both.
Sayonara
Konnichiwa,
GeorgeBoles said:2. "Measurment" of sound level was done with a "Mark I Tympano-Cochleometer" (much like a Mark I Optico-Retinometer in the visual realm.)
A potentially quite useful device, but not in order to generate a curve that can be compared to simulations.
GeorgeBoles said:3. I am still unclear about "distance rear wall" and "distance side wall". Do these distances relate to the DRIVER or the EDGE OF THE BAFFLE from the adjacent walls?
In all my various spreadsheet calculators I always assume the distances to the center of the sound source (driver center), as was also remarked by Rudolph.
GeorgeBoles said:
You cannot even get a good approximation of M/W/H baffles using my calaculator. They are complex resonant systems not ameanable to easy analysis using my spreadsheets and even the Formulas Linkwitz provides are not terribly accurate.
GeorgeBoles said:
No.
GeorgeBoles said:b.) Is it the tweeter/mid-range driver itself or the open baffle of these designs which provides the magic? (Don't you just love questions like that?)
It is both.
Sayonara
GLONG! All of a sudden, I am less happy. Kuei Yang Wang, have you heard either the Orions or the Millennium tweeter in a quality enclosure? I thought that I had things nearly, finally sorted out in my mind.
Perhaps then, I should be making something with one of the long ribbon tweeter/midranges. Likely contenders would be: B&G, Newform, DHenryP's DIY design ... any thoughts?
Are there any others out there who have experience in this specific area who either agree or disagree with Kuei Yang Wang's thoughts. Kuei Yang Wang, is there anything to elaborate on with regards this quetion?
Thanks again to Rudolph and Kuei Yang Wang for your thoughts.
Best regards,
George
Konnichiwa,
I heard them in a number of DIY and commercial speakers. I have also heard the various assorted other Dome tweeters, the best of this rather bad lot are the Focal inverted domes or the Thiel inverted ceramic domes. Conventional domes are not suited to use in high fidelity speakers, inverted domes are only a little better. Try spherical wave horns with low compression ratio drivers or ribbons with a modest horizontal waveguide.
I'm non too hot on magnetic planars (or any other full range dipole) either, but Quad ESL's and other sensible fullrange ESL's (can be DIY'ed) are the best solution if you like the presentation given by planars (or in other words full range dipoles).
For something more conventional you could look at the Audax PR170M0 in an open back or apperiodic enclosure combined with Aurum Cantus or Fountek Ribbon and then add an active dipole section (like 4 x 8") for the bass. That would likely be one of the best compromise solution using conventional, compact and affordable Speaker that combines the good sides of ESL's/Ribbons/Planars and of Electrodynamic systems.
Sayonara
GeorgeBoles said:
I heard them in a number of DIY and commercial speakers. I have also heard the various assorted other Dome tweeters, the best of this rather bad lot are the Focal inverted domes or the Thiel inverted ceramic domes. Conventional domes are not suited to use in high fidelity speakers, inverted domes are only a little better. Try spherical wave horns with low compression ratio drivers or ribbons with a modest horizontal waveguide.
I'm non too hot on magnetic planars (or any other full range dipole) either, but Quad ESL's and other sensible fullrange ESL's (can be DIY'ed) are the best solution if you like the presentation given by planars (or in other words full range dipoles).
For something more conventional you could look at the Audax PR170M0 in an open back or apperiodic enclosure combined with Aurum Cantus or Fountek Ribbon and then add an active dipole section (like 4 x 8") for the bass. That would likely be one of the best compromise solution using conventional, compact and affordable Speaker that combines the good sides of ESL's/Ribbons/Planars and of Electrodynamic systems.
Sayonara
Konnichiwa,
They have. Madisound bought a very large batch and are still supplying them. For after that, Sammi Sound Korea have a passable substitute, the SR165A50 (yes, I have used these too) though I liked the Audax a little better.
Sayonara
Nuuk said:Correct me if I am wrong but I though that Audax had stopped supplying drive units for DIY.
They have. Madisound bought a very large batch and are still supplying them. For after that, Sammi Sound Korea have a passable substitute, the SR165A50 (yes, I have used these too) though I liked the Audax a little better.
Sayonara
This sounds like what I might looking for. Something quite the opposite of my Ellis 1801 (SEAS Excel in BR and dome tweeter) but able to be powered to movie levels with a low powered amp, powered bass section aside.
When you say open-back, how is that different than dipole?
Would you arrange the bass drivers in a line or something like an H configuration? Four 8's instead of a pair of 12's?
Konnichiwa,
For movies and some REAL SPL handeling consider the big Neotek ribbon and a d'Appolito Array with two PR170M0. That should easily exceed 100db/W/m.
Open back with some flowresistance will be more of cardiode than a dipole.
More a kinda "M" or "W" configuration, 2 High. This is for a compact and affordable LF array, around 20" tall & 10" or less wide, upon which could be seated our MF/HF Box with PR170M and one of the smaller ribbons.
I would normally recommend a suitable set of bigger woofers, up to 4 X 15" per side in a "M" arrangement.
No, more like a pair of 10" or a single 12".
Sayonara
ultrachrome said:
For movies and some REAL SPL handeling consider the big Neotek ribbon and a d'Appolito Array with two PR170M0. That should easily exceed 100db/W/m.
ultrachrome said:
Open back with some flowresistance will be more of cardiode than a dipole.
ultrachrome said:
More a kinda "M" or "W" configuration, 2 High. This is for a compact and affordable LF array, around 20" tall & 10" or less wide, upon which could be seated our MF/HF Box with PR170M and one of the smaller ribbons.
I would normally recommend a suitable set of bigger woofers, up to 4 X 15" per side in a "M" arrangement.
ultrachrome said:
No, more like a pair of 10" or a single 12".
Sayonara
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