I’m going to build SL’s Phoenix, but am attracted to the all in one design of the Orion. For one thing it'll be easier in a shared room.to move around two boxes rather than four. So I’m thinking of mounting the Phoenix midrange baffle onto the Orion H frame woofer cabinets.
The W frame is wider and lower; the H frame resonance is higher (but with an XO at 120 Hz, both resonances are relatively outside the effective range of the woofers) and by the way the drivers are mounted - the W frame has the benefit of force cancellations.
What do people think of the ‘hybrid’ approach?
Thanks
Thanks
The W frame is wider and lower; the H frame resonance is higher (but with an XO at 120 Hz, both resonances are relatively outside the effective range of the woofers) and by the way the drivers are mounted - the W frame has the benefit of force cancellations.
What do people think of the ‘hybrid’ approach?
Thanks
Thanks
The integrated Orion style cabinet couples the strong twin bass driver forces, directly to the mids & tweeters. By SL going this way, this did not *appear*be a problem.
Though the sound of the Orion can now be improved - Revision 0.1 http://www.linkwitzlab.com/orion-rev1.htm - by decoupling the mids from the mid range panel!
So maybe something was lost in integration . .
Though the sound of the Orion can now be improved - Revision 0.1 http://www.linkwitzlab.com/orion-rev1.htm - by decoupling the mids from the mid range panel!
So maybe something was lost in integration . .
best of both worlds?
Beginning to think that the best all round compromise is to do a woofer ‘box’ Orion - H style, sitting underneath the midrange baffle, but just sitting off it, isolating vibrations.
This would still have the integrated look, and allow experimenting with different-better woofer locations, when "she who likes to be obeyed" is away and/ or I move to a bigger room.
It does mean I'd need a pair of inverted U shaped brackets to support the midrange baffle, straddling the woofer box. Though these could be used as a base, to support midrange driver brackets a la Orion Revision 0.1. This may be a simpler path to further midrange driver isolation than the Phoenix midrange driver spline arrangement, which I hear can be fiddly to construct.
I suspect that Phoenix XO would not require any change, but I still need to confirm or check this??
Thanks
Beginning to think that the best all round compromise is to do a woofer ‘box’ Orion - H style, sitting underneath the midrange baffle, but just sitting off it, isolating vibrations.
This would still have the integrated look, and allow experimenting with different-better woofer locations, when "she who likes to be obeyed" is away and/ or I move to a bigger room.
It does mean I'd need a pair of inverted U shaped brackets to support the midrange baffle, straddling the woofer box. Though these could be used as a base, to support midrange driver brackets a la Orion Revision 0.1. This may be a simpler path to further midrange driver isolation than the Phoenix midrange driver spline arrangement, which I hear can be fiddly to construct.
I suspect that Phoenix XO would not require any change, but I still need to confirm or check this??
Thanks
Rick,
Any kind of a hybrid.....W or H, with Orion or Phoenix style main panels is do-able. There might be some changes required to the crossover system depending upon how you implement it. Generally, a W-baffle would probably require a notch filter and an H-baffle probably wouldn't. The fore/aft position of the mid-panel relative to the bass baffle might also require some time delay.
The force cancellation of the W-frame woofer is desirable if your floor construction/support is marginal. If you're on a slab or some other solid base then I don't believe the H-frame construction would be a problem.
I think isolating the mid-panel from the bass is desirable in all instances.
Davey.
Any kind of a hybrid.....W or H, with Orion or Phoenix style main panels is do-able. There might be some changes required to the crossover system depending upon how you implement it. Generally, a W-baffle would probably require a notch filter and an H-baffle probably wouldn't. The fore/aft position of the mid-panel relative to the bass baffle might also require some time delay.
The force cancellation of the W-frame woofer is desirable if your floor construction/support is marginal. If you're on a slab or some other solid base then I don't believe the H-frame construction would be a problem.
I think isolating the mid-panel from the bass is desirable in all instances.
Davey.
I only saw it yesterday, but while I’m sure it’s right, John K’s woofer is stuffed with 3 ½ inch fibregalass, which deviates from the SL theory.
I’m not 100% convinced that there is no trade-off for the U shape’s efficiency gain, but there doesn’t at this point appear to be any evidence of any negatives. The effect on room modes is hardest to be certain of
I’m not 100% convinced that there is no trade-off for the U shape’s efficiency gain, but there doesn’t at this point appear to be any evidence of any negatives. The effect on room modes is hardest to be certain of
Well, Linkwitz is taking into account flow resistance in some form...
I think what he is saying (correct me if you think I'm wrong) is a) simplified models that are incorrect show you that a U-baffle has 6dB more output, and b) if you had a perfect flow resistor, the pattern would be a cardioid, but in reality it is probably not too likely. This last bit sort of jives with my own experience, that being some FEA modeling (without any flow resistance). Unfortunately, I have not verified my modeling yet, so I can currently only claim to be a trained monkey pushing buttons. Based on my button pushing, I do plan to build an H-baffle sometime in the future and hopefully take some polars in the parking lot. The reason I want to try H instead of U is because of the simulated very nasty polar response for a U-baffle I got, while the H is fairly decent (at least one geometry I came up with). I posted this stuff on my website.
I think what he is saying (correct me if you think I'm wrong) is a) simplified models that are incorrect show you that a U-baffle has 6dB more output, and b) if you had a perfect flow resistor, the pattern would be a cardioid, but in reality it is probably not too likely. This last bit sort of jives with my own experience, that being some FEA modeling (without any flow resistance). Unfortunately, I have not verified my modeling yet, so I can currently only claim to be a trained monkey pushing buttons. Based on my button pushing, I do plan to build an H-baffle sometime in the future and hopefully take some polars in the parking lot. The reason I want to try H instead of U is because of the simulated very nasty polar response for a U-baffle I got, while the H is fairly decent (at least one geometry I came up with). I posted this stuff on my website.
On a quick look http://ldsg.snippets.org/HORNS/index.php
an interesting website – I’ll have a good look when time permits.
an interesting website – I’ll have a good look when time permits.
rick57 said:
There's always room interaction. Dipole subs have a major front to back room mode which should be EQed as you would with a monopole. They have a smaller side mode. I personally think it isn't entirely the room stuff that makes dipoles better, but rather the lack of a box.
I didn't do a full bunch of measurements for U v H (although I should have) but my subjective opinion was that having the drivers at the front of the Box (check my site) gave slightly deeper/louder bass, but the H-frame gave slightly better quality bass.
Any differences weren't huge and unlikely to be repeatable. Were I going to rebuild my woofers (and I may) I'll probably move them out to U position, but with the same depth I have now. And use TC2s.
As someone mentioned, the differences between H and U are minimal compared the differences between box and no box. Go with what you thinks looks friendlier.
Steve
(JPK) I posted this under a dfferent topic, but I see lots of discussion here so I am reporting it in this thread with some additional comments. Let me also add that the overly simplified analysis on the Linkwitz site is inadiquite to model the performance of a real u-frame. It doesn't consider the driver's response of parameters. It dosen't consider that the resistance of a lined/stuffed u-frame is frequency dependent. A more indepth modeling tool can be obtainded from the FRDC. It is a MathCAD tool based on Martin King's TL worksheets that we developed together. Additional discussion and measured results are presented here
http://www.geocities.com/kreskovs/NaOdelay.html
and here
http://www.geocities.com/kreskovs/NaOdelay1.html
The MAthCAD design tool can be found here
http://www.geocities.com/kreskovs/U-frame-design.html
Additionally, SoundEasy V9.00 has U-frame and H-frame enclosure analysis features. It will evel allow you to analyse assymmetric H frames.
My original post follows:
(JPK)Let me make a couple of comments. First, a U-frame is not a true cardioid. The polar response will vary with frequency and with damping. The resonance peak of an undamped U-frame is at approximately C/(4L) where C is the sound speed and L the length of the U frame. At very low frequency, generally below that where there would be appreciable acoustic output, the undamped u-frame has a dipole pattern similar to an H frame dipole of the same total length (L/2 length ducts on both sides of the driver). However, as the frequency rises to a point where we start getting useful SPL out of the device the polar pattern starts to deviate from the H frame. Due to the asymmetry of the front and rear responses of the U-frame the polar response begins to loose it's 90 degree nulls. At the point where you are about 2 octaves below the resonant frequency of the U-frame the polar response is pretty much an oval. It is still symmetric front to rear.
Undamped there is more of a disadvantage to a u-frame than advantage compared to an H frame since the on axis response is about the same. There is a little more radiated power to the sides, but the system resonance is also an octave lower, thus closer to the crossover point.
Now when damping is added the story changes. To envision what happens consider that the response from the front and rear are composed of two components. First there is the part due to the driver motion. Call that D. Then there is the part due to the resonance of the u-frame, call it R. The front response is just D and the rear response is -D +R where the negative signs is used to note that the rear driver response is 180 out of phase with the front. Ideally, damping could be added such that R was driven to zero so the front a rear response would be identical. In such a case the U-frame would generate a true cardioid polar response and would also have an on axis SPL of 6dB greater than the H frame with similar damping over its useful range. Unfortunately, R can not be completely damped without having other effects. AT very low frequency, below the range of useful response, the damping has very little effect. As the frequency rises towards the typical resonance (150 to 200 Hz, depending on U-frame length) the damping becomes effective and the 1/4 wave peak can be significantly controlled. However, as the frequency continure to rise the damping continues to be effective so that it is never possible to obtain front and rear radiation that is identical. The test is to find the optimum damping that will result in minimizing the rear radiation. My experience is that the rear radiation can be reduced by 10 to 15dB over most of the u-frames useful range.
10 or 15dB might not sound that great [and doesn't look particularly spectacular on a polar plot scaled in dB] but look at the implication on the effect of reflections from a rear wall. Consider a monopole, a dipole and a U-frame with 10dB reduction in rear radiation. [Remember that a 10dB reductiuon means the radiated power is 1/10 that of the 0dB level, hardly insignificant.] With a monopole the reflection from the rear wall will radiate back forward and, neglecting differences in level, the reflected wave will sum with the direct front radiation either in phase or 180 degrees out of phase or somewhere in between. The limits of in and 180 out yield either a 6dB peak or a null. With a dipole, the result is the same except since the rear wave starts out 180 out of phase the frequency where the peaks and nulls occur will be inverted with respect to a monopole. Now consider the u-frame. Again the rear radiation will sum with in the limits of in phase or 180 degrees out of phase. But since the level is 10dB below the front radiation the reflected wave has less of an effect. Summed in phase the result is a maximum of a 2.4dB peak. Out of phase the results is a worse case of a 3.3dB dip. Obviously the in room case is much more complex than this but there are clearly advantages with the front to back room resonances with a U-frame.
So in summary, the correctly damped u-frame can yield a nominal 6dB greater on axis sensitivity than an H frame dipole with the same "foot print" over its useful frequency range which translates to 6dB greater max SPL for the same driver excursion; total radiated power lies somewhere less than a monopole but greater than a dipole (a true cardioid has the same radiated power as a dipole); it potentially has advantages over both mono and dipole systems with respect to front to rear room resonances; and the single draw back is that the resonance peak is an octave lower that a dipole with the same footprint. This proves to be of little concern when used as a woofer system with appropriate crossover.
Lastly, a dipole with the same sensitivity and max SPL limitations can be consturcted by making each leg of an H frame of length L so that the foot print of the dipole would be 2L, twice that of the U-frame. Of courde, this dipole would also have the same 1/4 resonances as the length L u-frame. The idea driving me to use of the u-frame was the greater sensitivity in a smaller package.
http://www.geocities.com/kreskovs/NaOdelay.html
and here
http://www.geocities.com/kreskovs/NaOdelay1.html
The MAthCAD design tool can be found here
http://www.geocities.com/kreskovs/U-frame-design.html
Additionally, SoundEasy V9.00 has U-frame and H-frame enclosure analysis features. It will evel allow you to analyse assymmetric H frames.
My original post follows:
(JPK)Let me make a couple of comments. First, a U-frame is not a true cardioid. The polar response will vary with frequency and with damping. The resonance peak of an undamped U-frame is at approximately C/(4L) where C is the sound speed and L the length of the U frame. At very low frequency, generally below that where there would be appreciable acoustic output, the undamped u-frame has a dipole pattern similar to an H frame dipole of the same total length (L/2 length ducts on both sides of the driver). However, as the frequency rises to a point where we start getting useful SPL out of the device the polar pattern starts to deviate from the H frame. Due to the asymmetry of the front and rear responses of the U-frame the polar response begins to loose it's 90 degree nulls. At the point where you are about 2 octaves below the resonant frequency of the U-frame the polar response is pretty much an oval. It is still symmetric front to rear.
Undamped there is more of a disadvantage to a u-frame than advantage compared to an H frame since the on axis response is about the same. There is a little more radiated power to the sides, but the system resonance is also an octave lower, thus closer to the crossover point.
Now when damping is added the story changes. To envision what happens consider that the response from the front and rear are composed of two components. First there is the part due to the driver motion. Call that D. Then there is the part due to the resonance of the u-frame, call it R. The front response is just D and the rear response is -D +R where the negative signs is used to note that the rear driver response is 180 out of phase with the front. Ideally, damping could be added such that R was driven to zero so the front a rear response would be identical. In such a case the U-frame would generate a true cardioid polar response and would also have an on axis SPL of 6dB greater than the H frame with similar damping over its useful range. Unfortunately, R can not be completely damped without having other effects. AT very low frequency, below the range of useful response, the damping has very little effect. As the frequency rises towards the typical resonance (150 to 200 Hz, depending on U-frame length) the damping becomes effective and the 1/4 wave peak can be significantly controlled. However, as the frequency continure to rise the damping continues to be effective so that it is never possible to obtain front and rear radiation that is identical. The test is to find the optimum damping that will result in minimizing the rear radiation. My experience is that the rear radiation can be reduced by 10 to 15dB over most of the u-frames useful range.
10 or 15dB might not sound that great [and doesn't look particularly spectacular on a polar plot scaled in dB] but look at the implication on the effect of reflections from a rear wall. Consider a monopole, a dipole and a U-frame with 10dB reduction in rear radiation. [Remember that a 10dB reductiuon means the radiated power is 1/10 that of the 0dB level, hardly insignificant.] With a monopole the reflection from the rear wall will radiate back forward and, neglecting differences in level, the reflected wave will sum with the direct front radiation either in phase or 180 degrees out of phase or somewhere in between. The limits of in and 180 out yield either a 6dB peak or a null. With a dipole, the result is the same except since the rear wave starts out 180 out of phase the frequency where the peaks and nulls occur will be inverted with respect to a monopole. Now consider the u-frame. Again the rear radiation will sum with in the limits of in phase or 180 degrees out of phase. But since the level is 10dB below the front radiation the reflected wave has less of an effect. Summed in phase the result is a maximum of a 2.4dB peak. Out of phase the results is a worse case of a 3.3dB dip. Obviously the in room case is much more complex than this but there are clearly advantages with the front to back room resonances with a U-frame.
So in summary, the correctly damped u-frame can yield a nominal 6dB greater on axis sensitivity than an H frame dipole with the same "foot print" over its useful frequency range which translates to 6dB greater max SPL for the same driver excursion; total radiated power lies somewhere less than a monopole but greater than a dipole (a true cardioid has the same radiated power as a dipole); it potentially has advantages over both mono and dipole systems with respect to front to rear room resonances; and the single draw back is that the resonance peak is an octave lower that a dipole with the same footprint. This proves to be of little concern when used as a woofer system with appropriate crossover.
Lastly, a dipole with the same sensitivity and max SPL limitations can be consturcted by making each leg of an H frame of length L so that the foot print of the dipole would be 2L, twice that of the U-frame. Of courde, this dipole would also have the same 1/4 resonances as the length L u-frame. The idea driving me to use of the u-frame was the greater sensitivity in a smaller package.
(JPK) I would like to make one additional brief comment. I expect to have a true cardioid woofer system design completed later this or early next year. The analysis and simulations are complete. Building a prototype and testing are next. However, I really don't expect much improvement over the U-frame. There are other issues with a u-frame that have a significant impact on system performance that go beyond the usually U vs H frame discussion which I am not prepared to discuss.
all this talk about dipole and cardioid bass got me thinking about a product that I saw at the AES convention last month.
http://www.getmad.us/MAD_SB412D.html
very interesting pro sound system designed by the guy who developed the planar elements for Monsoon speakers when they were still around. the subs and the main arrays can be either dipole or cardioid. very impressive sound considering the show floor conditions.
Greg
http://www.getmad.us/MAD_SB412D.html
very interesting pro sound system designed by the guy who developed the planar elements for Monsoon speakers when they were still around. the subs and the main arrays can be either dipole or cardioid. very impressive sound considering the show floor conditions.
Greg
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