KeithL
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Post by KeithL on Sept 13, 2024 10:38:54 GMT -5
No big surprise... and it just confirms something we already know... The best and most effective type of "room correction" or "room treatment" is to remove the walls and ceiling... (Unfortunately that one has a few significant "down-sides".) The proverbial "natural response of the speaker" ... well ... this is as close to anechoic as I'll ever get. Ground plane test at 6ft. I'm in the dipole null with my house 20ft behind me. To the left and right there's virtually nothing close enough to reflect back. View Attachment16-300Hz, 10Hz rumble filter on; Hi, Med, Lo damping settings (light, med, dark blue). No smoothing at all. THD no more than 1% @40hz. THD peaks at 16%, 13%, 11% @16hz for Lo, Med Hi damping respectively. View AttachmentView AttachmentI'm done with the theory, now to build up the other one and get them in the room! This proves it. We should bring our systems outside for the best frequency response! No correction needed! |
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KeithL
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Post by KeithL on Sept 13, 2024 10:57:25 GMT -5
The only catch there is that, when you eliminate some of the room modes, you are left with just a few that "purely dominate" the situation. And, arguably, "that's how an organ pipe works". (One of the arguments in favor of using a bunch of small subs is that the room modes are all different... so they sort of blur together and average out. And, for anyone considering this sort of project, one of the disadvantages of an open-baffle sub is that it will tend to have a 12 dB/octave rolloff as you go lower below the "baffle cutoff". So they require active EQ to provide a 12 dB/octave boost... And lots of big drivers, with a lot of surface area, and a lot of travel, to move all that air... And enough power to do the job driving them... You can design a reasonably small sealed or ported sub that can deliver a lot of output at rather low frequencies. That's just not an option with an open-baffle sub. Another interesting thought... Another "design variation" would be to stack several sheets of felt inside the cabinet behind each of the woofers. Basically stack sheets of felt behind the drivers... with some sort of grating to serve as a "back panel" to hold them in place. If you do that then they sort of transition from "open baffle" to "infinite baffle" at low frequencies... The felt provides resistive absorption for at least some of the back-wave energy... But only "sort of" since you can't possibly absorb all of the back-wave. But the situation, as seen by the driver, is more damped, so resulting resonances should at least have a lower Q. (It might produce interesting results... and could be tried without major modifications...) Remember that most drivers have a rather high mechanical Q and, with an open baffle, there is really nothing to modify that. And a servo that works by using feedback from a second coil is not as tightly coupled as a "purely electronic servo". (The "in-box resonance" of your driver is pretty much the same as "its free air resonance" and most modern drivers do want/expect a bit of mechanical damping.) Among the reasons to use an open baffle dipole sub is that the room resonances are not engaged as much as a conventional sealed or ported sub. With sealed or ported the pressure wave is omnidirectional, bouncing off all walls, ceiling and floor. And those resonances can add up either constructively or destructively. With the open baffle dipole the room modes to the sides and top and bottom of the sub are not engaged as much, due to dipole cancelation. Here is an illustration. I measured at 3ft using a regular amplifier with no servo and no shelving filters to compensate for the dipole cancelation. I had the sub pointed in the direction of the 15ft length of the room (orange trace). Then I turned the sub 90 degrees so it was playing across the 11ft width of the room (green trace). Resonances of the length mode are 37.5, 75, 112.5, 150. For the width modes 51, 102, 153. The ceiling is 8ft, and its modes are 70.3 and 140.6. You can see the modes illustrated at the bottom of the graph and they correspond to the trace colors. View AttachmentIndeed, with the speaker pointed in the length orientation there is a peak at 37.5 , but not at 51. With it pointed in the width orientation the peak is at 51 but not 37.5. Beyond that the modes start to stack and at the microphone can add up either positive or negative. As we would expect, the floor/ceiling mode is the same for both orientations but there's actually a cancellation in both measurements around 140. So then I did a series of measurements as close as I dared to the cone (given the long travel at low frequencies). Here again with the regular amp with no servo and no shelving filter compensation, you see a very flat response from this speaker right down to just below 30Hz, where it rolls off 12db/octave. And this is as expected because the Fs of the driver is ... 28.3Hz! View AttachmentView AttachmentNext week sometime when I finally pull the Outlaw subs out of the listening room and install the dipoles, I will put the 12" Outlaw sub in the den in the exact same spot and measure to see how it excites the room modes. SCIENCE!  |
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Post by marcl on Sept 13, 2024 11:29:09 GMT -5
The only catch there is that, when you eliminate some of the room modes, you are left with just a few that "purely dominate" the situation. And, arguably, "that's how an organ pipe works". (One of the arguments in favor of using a bunch of small subs is that the room modes are all different... so they sort of blur together and average out. And, for anyone considering this sort of project, one of the disadvantages of an open-baffle sub is that it will tend to have a 12 dB/octave rolloff as you go lower below the "baffle cutoff". So they require active EQ to provide a 12 dB/octave boost... And lots of big drivers, with a lot of surface area, and a lot of travel, to move all that air... And enough power to do the job driving them... You can design a reasonably small sealed or ported sub that can deliver a lot of output at rather low frequencies. That's just not an option with an open-baffle sub. Another interesting thought... Another "design variation" would be to stack several sheets of felt inside the cabinet behind each of the woofers. Basically stack sheets of felt behind the drivers... with some sort of grating to serve as a "back panel" to hold them in place. If you do that then they sort of transition from "open baffle" to "infinite baffle" at low frequencies... The felt provides resistive absorption for at least some of the back-wave energy... But only "sort of" since you can't possibly absorb all of the back-wave. But the situation, as seen by the driver, is more damped, so resulting resonances should at least have a lower Q. (It might produce interesting results... and could be tried without major modifications...) Remember that most drivers have a rather high mechanical Q and, with an open baffle, there is really nothing to modify that. And a servo that works by using feedback from a second coil is not as tightly coupled as a "purely electronic servo". (The "in-box resonance" of your driver is pretty much the same as "its free air resonance" and most modern drivers do want/expect a bit of mechanical damping.) I don't see where absorbing some of the back wave is a benefit. You actually want the low frequencies below 120Hz to cancel at the top, bottom and sides so that those modes are greatly reduced and they don't act on their own or in combination with the length mode to disrupt the response. My tests in the small untreated room demonstrated how the modes are mostly only present in the direction of the figure 8 radiation and additional modes do not combine. Response was surprisingly controlled ... especially considering it was just one sub in the middle of the room. Of course when I bring it into the treated listening room and compare directly to the response of the two conventional subs ... we shall see. Yes I actually measured the rolloff of the dipole and even characterized the compensation required using my miniDSP ... all as expected. But I don't see where the compensation filters have any downside. The resulting response is 3db down at 16Hz. Impulse response is excellent, and distortion (as measured in the ground plane test) was <2% above 30Hz and rising over 10% only below 20Hz. But yes, you have to do all those things .... compensate, add drivers, enough power ... and the servo (which of course you can do in a sealed or ported sub too) helps to control the lighter cones with the net result being a very fast impulse response. In the end what is hoped is that these subs provide a similar experience to the planar dipole Magnepan experience, with more dynamic range and clarity and less room interaction. Distortion, Impulse and Phase for Hi, Med, Lo servo (light, middle, dark)    |
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Post by leonski on Sept 13, 2024 13:37:48 GMT -5
The only catch there is that, when you eliminate some of the room modes, you are left with just a few that "purely dominate" the situation. And, arguably, "that's how an organ pipe works". (One of the arguments in favor of using a bunch of small subs is that the room modes are all different... so they sort of blur together and average out. And, for anyone considering this sort of project, one of the disadvantages of an open-baffle sub is that it will tend to have a 12 dB/octave rolloff as you go lower below the "baffle cutoff". So they require active EQ to provide a 12 dB/octave boost... And lots of big drivers, with a lot of surface area, and a lot of travel, to move all that air... And enough power to do the job driving them... You can design a reasonably small sealed or ported sub that can deliver a lot of output at rather low frequencies. That's just not an option with an open-baffle sub. Another interesting thought... Another "design variation" would be to stack several sheets of felt inside the cabinet behind each of the woofers. Basically stack sheets of felt behind the drivers... with some sort of grating to serve as a "back panel" to hold them in place. If you do that then they sort of transition from "open baffle" to "infinite baffle" at low frequencies... The felt provides resistive absorption for at least some of the back-wave energy... But only "sort of" since you can't possibly absorb all of the back-wave. But the situation, as seen by the driver, is more damped, so resulting resonances should at least have a lower Q. (It might produce interesting results... and could be tried without major modifications...) Remember that most drivers have a rather high mechanical Q and, with an open baffle, there is really nothing to modify that. And a servo that works by using feedback from a second coil is not as tightly coupled as a "purely electronic servo". (The "in-box resonance" of your driver is pretty much the same as "its free air resonance" and most modern drivers do want/expect a bit of mechanical damping.) Among the reasons to use an open baffle dipole sub is that the room resonances are not engaged as much as a conventional sealed or ported sub. With sealed or ported the pressure wave is omnidirectional, bouncing off all walls, ceiling and floor. And those resonances can add up either constructively or destructively. With the open baffle dipole the room modes to the sides and top and bottom of the sub are not engaged as much, due to dipole cancelation. Here is an illustration. I measured at 3ft using a regular amplifier with no servo and no shelving filters to compensate for the dipole cancelation. I had the sub pointed in the direction of the 15ft length of the room (orange trace). Then I turned the sub 90 degrees so it was playing across the 11ft width of the room (green trace). Resonances of the length mode are 37.5, 75, 112.5, 150. For the width modes 51, 102, 153. The ceiling is 8ft, and its modes are 70.3 and 140.6. You can see the modes illustrated at the bottom of the graph and they correspond to the trace colors. View AttachmentIndeed, with the speaker pointed in the length orientation there is a peak at 37.5 , but not at 51. With it pointed in the width orientation the peak is at 51 but not 37.5. Beyond that the modes start to stack and at the microphone can add up either positive or negative. As we would expect, the floor/ceiling mode is the same for both orientations but there's actually a cancellation in both measurements around 140. So then I did a series of measurements as close as I dared to the cone (given the long travel at low frequencies). Here again with the regular amp with no servo and no shelving filter compensation, you see a very flat response from this speaker right down to just below 30Hz, where it rolls off 12db/octave. And this is as expected because the Fs of the driver is ... 28.3Hz! View AttachmentView AttachmentNext week sometime when I finally pull the Outlaw subs out of the listening room and install the dipoles, I will put the 12" Outlaw sub in the den in the exact same spot and measure to see how it excites the room modes. SCIENCE! 'That's how an organ pipe works.' Has anyone here but me spent time listening to a pipe organ? Did a Church Tour (self organized) years ago and heard many classical and 'ancient' instruments. Including some played by Bach and other Baroque composers. Amazing in a large reververent space. And the bass? Unlike any I'd ever heard before.....or since. But here in SoCal? We have one of the few (I suspect 3 or fewer) OUTDOOR Municiple Pipe Organs remaining in the world. The Spreckels Organ has OVER 5000 pipes and is the largest of its type on Earth. Come to San Diego any SUNDAY for a free concert. Me? I'd recommend a winter visit with RAIN. The instrument sounds best in cool, damp weather...... |
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Post by marcl on Sept 13, 2024 15:18:14 GMT -5
Looms larger than I had in my head, for some reason, but not a problem. The acoustic center is 7ft from the front wall and it’s fine. And actually the 25% point is 6’7” so could push it back another 5-6” and not overlap the 3.7. I’ll test it laying down across in front of the TV too, and it’s funny because it looks too big but it actually would sit an inch below the glass table. Either way, we’re probably moving the coffee table into the den. So next couple days as I get the other one built I will also likely disconnect the front Outlaw sub and hook this one up and start testing.   Oh and ... I did not line the inner walls of the cabinet with anything ... no Norez or Dynamat. I sent Danny Richie the ground plane test results and I asked what - if anything - Norez would do to improve the performance. He replied "The No Rez will tighten up the response and provide a cleaner sound.". |
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Post by marcl on Sept 13, 2024 15:38:04 GMT -5
The only catch there is that, when you eliminate some of the room modes, you are left with just a few that "purely dominate" the situation. And, arguably, "that's how an organ pipe works". (One of the arguments in favor of using a bunch of small subs is that the room modes are all different... so they sort of blur together and average out. And, for anyone considering this sort of project, one of the disadvantages of an open-baffle sub is that it will tend to have a 12 dB/octave rolloff as you go lower below the "baffle cutoff". So they require active EQ to provide a 12 dB/octave boost... And lots of big drivers, with a lot of surface area, and a lot of travel, to move all that air... And enough power to do the job driving them... You can design a reasonably small sealed or ported sub that can deliver a lot of output at rather low frequencies. That's just not an option with an open-baffle sub. Another interesting thought... Another "design variation" would be to stack several sheets of felt inside the cabinet behind each of the woofers. Basically stack sheets of felt behind the drivers... with some sort of grating to serve as a "back panel" to hold them in place. If you do that then they sort of transition from "open baffle" to "infinite baffle" at low frequencies... The felt provides resistive absorption for at least some of the back-wave energy... But only "sort of" since you can't possibly absorb all of the back-wave. But the situation, as seen by the driver, is more damped, so resulting resonances should at least have a lower Q. (It might produce interesting results... and could be tried without major modifications...) Remember that most drivers have a rather high mechanical Q and, with an open baffle, there is really nothing to modify that. And a servo that works by using feedback from a second coil is not as tightly coupled as a "purely electronic servo". (The "in-box resonance" of your driver is pretty much the same as "its free air resonance" and most modern drivers do want/expect a bit of mechanical damping.) 'That's how an organ pipe works.' Has anyone here but me spent time listening to a pipe organ? Did a Church Tour (self organized) years ago and heard many classical and 'ancient' instruments. Including some played by Bach and other Baroque composers. Amazing in a large reververent space. And the bass? Unlike any I'd ever heard before.....or since. But here in SoCal? We have one of the few (I suspect 3 or fewer) OUTDOOR Municiple Pipe Organs remaining in the world. The Spreckels Organ has OVER 5000 pipes and is the largest of its type on Earth. Come to San Diego any SUNDAY for a free concert. Me? I'd recommend a winter visit with RAIN. The instrument sounds best in cool, damp weather...... Not withstanding the fact that pipe organs and open baffle dipole subwoofers have nothing in common other than the fact that I will certainly play sound from the former, through the latter Yes, it's really cool to hear a big pipe organ live, especially if it has a 32' rank. I heard the one in the big church in Reykjavik, and also in some smaller churches in PA. Verizon Hall in the Kimmel Center in Philadelphia has one and I have an SACD of that organ with the orchestra playing the Saint Saens No. 3. This album has some really nice deep bass!  |
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ttocs
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Post by ttocs on Sept 13, 2024 15:51:14 GMT -5
Oh and ... I did not line the inner walls of the cabinet with anything ... no Norez or Dynamat. I sent Danny Richie the ground plane test results and I asked what - if anything - Norez would do to improve the performance. He replied "The No Rez will tighten up the response and provide a cleaner sound.". Rhetorical question: Which means? . . . . . |
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KeithL
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Post by KeithL on Sept 13, 2024 16:56:29 GMT -5
The reason I would offer is that I really wouldn't want "a real pure true dipole response". So I'm pushing it in the direction of being partially an infinite baffle... And I'm also adding some mechanical damping - in the form of the air resistance of the felt - to help damp the driver itself. The problem is that, at frequencies where the wavelength is much longer than the baffle, with a pure dipole you WILL have near perfect cancellation. (And, considering that the wavelength at 20 Hz is 50 feet... that's going to be most of the time unless you have a huge baffle.) The woofer moves forward, it pushes the air out the front, the air goes around the side, and in the back. At the very edges you get that nice theoretically perfect "wavefront going past your listening position"... But, at least in principle, you get pretty much NO bass anywhere else in the room. (Because the driver is simply not "pushing air towards the rest of the room".) The air goes out the front, and in the back, and vice versa. At the edges you get the wavefront from the air going around the baffle. But, at any other point in the room, you get essentially zero pressure change... which is sort of like "zero bass". This means that you only have a very narrow sweet spot... anywhere really near one of the edges of the baffle. Or perhaps really close to the front and rear... (Where the air being pushed by the driver "has to go past you to get between the front and the back".) But, pretty much, ONLY where the air has to go PAST you in order to get from front to back and back to front. (You don't get much "wave like activity" propagating into the rest of the room. I know I'm oversimplifying a bit there... But, at very low frequencies, it's not that far off... And that's what I've seen described with some speakers like Linkwitz... They sound really great... but ONLY if you're sitting pretty close to the edge of the baffle... (So a relatively tiny sweet spot in a normal room.) The only catch there is that, when you eliminate some of the room modes, you are left with just a few that "purely dominate" the situation. And, arguably, "that's how an organ pipe works". (One of the arguments in favor of using a bunch of small subs is that the room modes are all different... so they sort of blur together and average out. And, for anyone considering this sort of project, one of the disadvantages of an open-baffle sub is that it will tend to have a 12 dB/octave rolloff as you go lower below the "baffle cutoff". So they require active EQ to provide a 12 dB/octave boost... And lots of big drivers, with a lot of surface area, and a lot of travel, to move all that air... And enough power to do the job driving them... You can design a reasonably small sealed or ported sub that can deliver a lot of output at rather low frequencies. That's just not an option with an open-baffle sub. Another interesting thought... Another "design variation" would be to stack several sheets of felt inside the cabinet behind each of the woofers. Basically stack sheets of felt behind the drivers... with some sort of grating to serve as a "back panel" to hold them in place. If you do that then they sort of transition from "open baffle" to "infinite baffle" at low frequencies... The felt provides resistive absorption for at least some of the back-wave energy... But only "sort of" since you can't possibly absorb all of the back-wave. But the situation, as seen by the driver, is more damped, so resulting resonances should at least have a lower Q. (It might produce interesting results... and could be tried without major modifications...) Remember that most drivers have a rather high mechanical Q and, with an open baffle, there is really nothing to modify that. And a servo that works by using feedback from a second coil is not as tightly coupled as a "purely electronic servo". (The "in-box resonance" of your driver is pretty much the same as "its free air resonance" and most modern drivers do want/expect a bit of mechanical damping.) I don't see where absorbing some of the back wave is a benefit. You actually want the low frequencies below 120Hz to cancel at the top, bottom and sides so that those modes are greatly reduced and they don't act on their own or in combination with the length mode to disrupt the response. My tests in the small untreated room demonstrated how the modes are mostly only present in the direction of the figure 8 radiation and additional modes do not combine. Response was surprisingly controlled ... especially considering it was just one sub in the middle of the room. Of course when I bring it into the treated listening room and compare directly to the response of the two conventional subs ... we shall see. Yes I actually measured the rolloff of the dipole and even characterized the compensation required using my miniDSP ... all as expected. But I don't see where the compensation filters have any downside. The resulting response is 3db down at 16Hz. Impulse response is excellent, and distortion (as measured in the ground plane test) was <2% above 30Hz and rising over 10% only below 20Hz. But yes, you have to do all those things .... compensate, add drivers, enough power ... and the servo (which of course you can do in a sealed or ported sub too) helps to control the lighter cones with the net result being a very fast impulse response. In the end what is hoped is that these subs provide a similar experience to the planar dipole Magnepan experience, with more dynamic range and clarity and less room interaction. Distortion, Impulse and Phase for Hi, Med, Lo servo (light, middle, dark) View AttachmentView AttachmentView Attachment |
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ttocs
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I always have a wonderful time, wherever I am, whomever I'm with. (Elwood P Dowd)
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Post by ttocs on Sept 13, 2024 17:13:15 GMT -5
And that's what I've seen described with some speakers like Linkwitz... They sound really great... but ONLY if you're sitting pretty close to the edge of the baffle... (So a relatively tiny sweet spot in a normal room.) This wasn't what I experienced in the Linkwitz room at AXPONA. I waked around the room in amazement at how well the soundstage stayed intact as I moved about. |
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Post by marcl on Sept 14, 2024 8:10:45 GMT -5
The reason I would offer is that I really wouldn't want "a real pure true dipole response". So I'm pushing it in the direction of being partially an infinite baffle... And I'm also adding some mechanical damping - in the form of the air resistance of the felt - to help damp the driver itself. The problem is that, at frequencies where the wavelength is much longer than the baffle, with a pure dipole you WILL have near perfect cancellation. (And, considering that the wavelength at 20 Hz is 50 feet... that's going to be most of the time unless you have a huge baffle.) The woofer moves forward, it pushes the air out the front, the air goes around the side, and in the back. At the very edges you get that nice theoretically perfect "wavefront going past your listening position"... But, at least in principle, you get pretty much NO bass anywhere else in the room. (Because the driver is simply not "pushing air towards the rest of the room".) The air goes out the front, and in the back, and vice versa. At the edges you get the wavefront from the air going around the baffle. But, at any other point in the room, you get essentially zero pressure change... which is sort of like "zero bass". This means that you only have a very narrow sweet spot... anywhere really near one of the edges of the baffle. Or perhaps really close to the front and rear... (Where the air being pushed by the driver "has to go past you to get between the front and the back".) But, pretty much, ONLY where the air has to go PAST you in order to get from front to back and back to front. (You don't get much "wave like activity" propagating into the rest of the room. I know I'm oversimplifying a bit there... But, at very low frequencies, it's not that far off... And that's what I've seen described with some speakers like Linkwitz... They sound really great... but ONLY if you're sitting pretty close to the edge of the baffle... (So a relatively tiny sweet spot in a normal room.) Yeah the thing is, trying to theoretically describe what dipole speakers will sound like (at any frequency) is problematic because it depends so much on the room. The phenomena you describe may be theoretically plausible, but in real rooms - especially appropriately treated rooms - there is a whole lot more going on .... and they can sound great or terrible with respect to bass response or imaging and soundstage, etc. Bottom line is ... lots of diffusion behind, out from the front wall at least 5 1/2ft, bass traps! Here's my friend's room with 3.7s like mine. No bass traps at all. Imaging was not clear at first, so we added the diffusers and literally as he stood them against the wall I sat and watched the soundstage come together. Then we measured and looked for reflections and placed absorbers on the left side and overhead ... the soundstage solidified and got wider and deeper. And yes, imaging is best at the MLP but you can walk around the room and the sound is uniform. But, his room is 17x30 with a 9ft ceiling. Very different from my room. Bass from his VMPS sub is okay after Dirac .... but Clarity in the room is not as good as mine.  And... my Rooze setup is crazy, but I tried it and the effect in my room is amazing. In some other room (like the one above) you can't do it. I heard the Magnepan 30.7 big multi-panel speakers at a dealer in a big untreated room and they sounded good ... but imaging sucked and bass varied all over the place. The little "30.7 for condos" in a small room with lots of diffusion, and the dipole woofer with eight 6 1/2" drivers per side and 100W each ... sounded amazing. Better bass even. And I agree with ttocs that the Linkwitz and other small full range dipoles made with conventional speakers can sound good even in hotel rooms. Steve Guttenberg has had great things to say about Clayton Shaw designs and one of them is his current reference. As with ANY room ... bass absorption is necessary. But I will measure my 12" Outlaw sub again center of the front wall with no room correction ... and then I will measure the OB Dipole in the 25% position ... and we'll see the effect of the room modes. And ... I actually have two big chunks of 703/705 behind the TV and I will reposition them so they contribute more to absorbing the back wave of the dipoles before it hits the front wall. |
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Post by marcl on Sept 15, 2024 5:38:52 GMT -5
Foiled! And not by my new sub ... no, it was our old friend the XMC-2 again, up to its subtle deceptions and diversions ... the sleight of hand that gradually subverts a little at a time so that you suspect everything BUT the processor ... then eventually your own sanity. Gets me every time. Well ... a couple cold, hard, dead reboots made it listenable for the evening Season 1 finale of Gangs of London. Then this morning a Factory Reset ... and then we shall see. Ya see, my SIMPLE PLAN yesterday was to take the simplest step to simply replace my front Outlaw 12" sub with the new OB sub. That was it. Move a wire, do a baseline test with no PEQ or Dirac, then run Dirac and use ONLY the OB sub (rear Outlaw 10" sub disconnected too) until I build up the second sub and go into comprehensive testing. But to paraphrase some famous general ... no plan survives first contact with finicky software! First the easiest part, that went pretty well: Playing the Outlaw 12" sub center of the front wall, vs the OB sub 6'11" from the front wall and 2'3" from the side wall (measured at the acoustic center). Outlaw in orange, OB in yellow.   This is good! Without the 10Hz Rumble Filter the OB extends well below 20Hz. It's subtle, but the OB response is a little smoother after the big 40Hz length mode. And remember, I have a LOT of bass traps in this room including a couple big chunks of fiberglass very near those two subs in the front of the room. Look at the room modes at the bottom of the frequency response plot. The red lines are the length modes, and we would expect the OB sub to excite each of them one way or the other. But where the length, width and height modes start piling up above 80Hz, the OB is not exciting the latter two so much. The big difference is in the impulse response. The OB is on the job within a couple milliseconds while the Outlaw is still getting out of bed. And then ... it was all downhill for a frustrating 3hrs reminiscent of what I experienced three months ago trying to integrate a new piece of gear. Once I started doing Dirac calibrations and loading new filters the behavior was strange, I suspected issues with levels or the big peak confusing Dirac ... on and on ... each thing I tried produced a different symptom that made no sense .... until the definitive symptom when the processor would not make a sound from the left channel, except for the occasional random very loud SNAP! It was dinner time, lucky for the XMC-2! Dishes done in a hurry. Punt .... another cold dead reboot and I got it all back to a stable and listenable state with original PEQ and Dirac filter and still with the OB replacing the front Outlaw, and we watched the evening entertainment. So now after the Factory Reset I'll figure out how to sneak up on a Dirac calibration again ... tomorrow. For today, I have my monthly Philadelphia Area Audio Group gathering in the afternoon. Looks like 45 members gathering to hear the host's system which includes gear from Backert Labs, Art Audio, Peak-Consult, TW-Acustic .... yeah, me neither!  |
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Post by leonski on Sept 15, 2024 15:55:06 GMT -5
Marcl? I had FUN going to various persons homes and just listening. Have a soda or beer and just LISTEN. Stuff I can't afford CHECK. Stuff I'd never ordinarily hear? 2X Check. Stuff I'd NEVER buy? 3X check.
And a few hidden gems.
Once? one of the pair of (IIRC) Constellation Monos failed to light. These were like 40 large the pair or some such. A Volunteer from the crowd went home and brought back a PAIR of Emo Monos. From down
the line. not a '1' series.
And you know? It sounded fabulous. Speakers cost 9x or 10x what the driving amps cost. Can you spell 'mismatch'? Nobody complained! Not even the guys giving the demo..
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Post by marcl on Sept 16, 2024 3:03:53 GMT -5
Marcl? I had FUN going to various persons homes and just listening. Have a soda or beer and just LISTEN. Stuff I can't afford CHECK. Stuff I'd never ordinarily hear? 2X Check. Stuff I'd NEVER buy? 3X check. And a few hidden gems. Once? one of the pair of (IIRC) Constellation Monos failed to light. These were like 40 large the pair or some such. A Volunteer from the crowd went home and brought back a PAIR of Emo Monos. From down the line. not a '1' series. And you know? It sounded fabulous. Speakers cost 9x or 10x what the driving amps cost. Can you spell 'mismatch'? Nobody complained! Not even the guys giving the demo.. This is a great group. It's limited to 80 members and gatherings are at least monthly at a member's house with typically 30-40 attending. And yes, gear I would never own ... or never want to own ... and mostly costing many times what my system costs and to my ears not sounding as good! But great conversation and some interesting folks .... general audiophiles, a dealer or two, a writer for Absolute Sound magazine, a SiriusXM DJ, DIY hobbyists .... and a nice lunch!   In a couple weeks we're getting a demo of the BACCH-SP with its creator Edgar Chouieri. Next month we're visiting Claire Global to tour their facility. www.clairglobal.com/November meeting is at this guy's house ...  |
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ttocs
Global Moderator
I always have a wonderful time, wherever I am, whomever I'm with. (Elwood P Dowd)
Posts: 8,168
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Post by ttocs on Sept 16, 2024 7:57:19 GMT -5
Gotta give folks credit for trying to use a difficult room. Watch your head! |
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Post by marcl on Sept 16, 2024 9:39:07 GMT -5
Gotta give folks credit for trying to use a difficult room. Watch your head! Found this photo on Instagram. Looks more reasonable from this angle.  |
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Post by marcl on Sept 18, 2024 11:08:32 GMT -5
I have the first OB sub in the system, standing on the right side pretty much where I think it will end up after testing. Acoustic center is 7' from the front wall and 3' from the right side wall. Center Sub is set to LFE and goes to the OB along with <50Hz from the front L/R. They are mixed together using a Rolls mixer. Ultimately the Rolls will send LFE to both OB subs, and L/R front <50Hz to the L/R subs respectively. Small speaker bass management goes to L/R fronts      These measurements are with my usual Dirac calibration with 6 point measurement. Psychoacoustic smoothing on the frequency response. Waterfall is left channel. So far so good ... sounds great too! The second sub has all the speakers mounted. Wiring it up this afternoon. Only took about 25min per speaker this time, now that I have to tools and process worked out. |
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Post by marcl on Sept 18, 2024 15:51:10 GMT -5
Okay! Firing on all six cylinders! Time for a burger!  |
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Post by marcl on Sept 21, 2024 10:59:50 GMT -5
Maybe some practical value, or maybe ... just so I know. Have you wondered what actually happens when you turn the phase knob on a sub from 0 to 180 degrees? Pretty, isn't it. Impulse Response on the left, Phase Response on the right. Measurements were taken for the left sub only, with frequency sweeps from 10-200Hz. There is a LPF at 60Hz, 24db/octave. The left front speaker's Impulse Response is shown in blue, and it has a HPF at 60Hz, 24db/octave. No Dirac filters. there is PEQ on the sub only, to pull down the 40Hz resonance from the room. Servo damping is Hi, Extension Filter 14Hz, 10Hz Rumble Filter On.   I started with the Phase knob at 0 and turned it three clicks at a time until it got to 180. That was 13 measurements, 39 clicks, with 180 one click past the last measurement. Notice a couple things ... the difference is more gradual near 0 and 180, and more spaced in between. The transition from the negative wave to the positive wave happens around 1/3 of the way, at 12 clicks. So now with the sub and the left front speaker on, what is the effect of the Phase control? 0, +12 clicks, 90, 180. Remember that at 0 the sub polarity is negative relative to the front speaker, and at +12 clicks the sub polarity is just starting to go positive.  As you would expect, the lowest dark blue trace is with Phase=0 (opposite the front speaker) and response gets smoother as the Phase control is turned toward 180. Notice that dip at 100Hz in all the plots. I wonder if that has to do with phase alignment of the left speaker and the sub at 60Hz? Well using The REW Alignment Tool I told it to Align Phase at Cursor (60Hz) and sure enough, with a 3ms delay on the 100Hz dip is pretty much gone and the two above it are improved too.  Unfortunately I can't more the sub forward or the speaker backward 3 1/2ft and I don't have independent delay controls for them with any DSP. The subs are already 7ft from the front wall. But actually Dirac did a pretty good job smoothing it all out. So what did I learn? Well, I can't use the Phase control to affect any alignment of each sub to its corresponding front speaker. All I can do is make sure the polarity is correct. And, I made some pretty pictures. |
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Post by leonski on Sept 22, 2024 15:36:16 GMT -5
One thing about 'phase'. I suspect it would work best if Both the subs were acting 'in unison'.
After settling on your settings and recording the data?
Do an A/B polarity swap on ONE of the subs and listen. Swap back than turn the phase control to the opposite 'stop'.
I'm curious about what changes you may or may not hear.
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Post by marcl on Sept 23, 2024 9:41:18 GMT -5
One thing about 'phase'. I suspect it would work best if Both the subs were acting 'in unison'. After settling on your settings and recording the data? Do an A/B polarity swap on ONE of the subs and listen. Swap back than turn the phase control to the opposite 'stop'. I'm curious about what changes you may or may not hear. Of course my goal with this build is to improve the sound for music and movies. But also I really want to quantify a lot of things that have never been clearly documented about how dipole subs work in general and specifically how this design with this servo amp works. So I'm optimizing along the way but also doing extra tests to quantify what each setting does. Sure, listening is important. But many, many people ONLY listen and never measure. And I know from doing both, that I can listen on two different days or even morning and evening the same day and have it sound different ... and I changed NOTHING. But what would someone say? "Oh that's because the noise in your power line was lower at night ... or on Sunday night vs Monday morning". No ... not a chance ... it's psychoacoustics and brain stress and sensory distraction .... So I do not make random changes and try to decide if I hear a difference. I make changes based on a hypothesis, measure the result, see if the result confirms the hypothesis ... and THEN I listen to see if the expected audible effect of the hypothesis is evident in the listening. Anyway, what are the most important things to do when integrating subs? - With more than one sub they must be time and level aligned to each other. That means the same level at the MLP and with an impulse response measurement that starts playing at the same time.
- When crossing between a main speaker and sub for Bass Management, the goal is to align the phase of the two speakers at the crossover point. Phase changes with frequency so they will not be in phase at every frequency, but you try to align them at the crossover.
Phase, delay and polarity are terms that should be carefully and separately used, as is appropriate.
Right now if I measure my left front speaker and the left sub ... the polarity is the same with the phase control of the sub at 180. The levels are matched. Response is smooth across the 60Hz crossover point. But it appears that the front speaker is playing 3ms ahead of the sub, and there's nothing I can do about that in my current setup.
Today I have a few ideas for testing, and the first thing I'm going to do is see if switching the wires on the sub does exactly the same thing as turning the phase knob from 0 to 180.
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The proverbial "natural response of the speaker" ... well ... this is as close to anechoic as I'll ever get. Ground plane test at 6ft. I'm in the dipole null with my house 20ft behind me. To the left and right there's virtually nothing close enough to reflect back.
