Hello all,
I've recently been bitten by the OB/Dipole bug and have just built myself a set of 3-way actively crossed mains (Alpha15A, Dayton PS220-8, B&G Neo3PDRW (dipole operation) and am just falling in love with the intoxicating sound of open baffle loudspeakers. I can and probably will put together a build thread so I can hopefully get some feedback on this build.
I plan on using them (and a OB/Dipole center channel I'll be designing) for home theater duties in addition to music. Now I need to replace my very old and very laughable rear-speaker situation. I want dipole operation, but I also want them to be able to make some bass. I'll want the mid/tweet to be approx 30-36" off the ground. I don't want them to be too bulky either. What do?
Enter the LXMini. I am not entirely opposed to just building the kit as S.Linkwitz specified-- and that would probably the smartest and easiest idea, but where's the fun and DIY spirit in that? I fancy using different drivers. Specifically, the Dayton PS180-8 and the B&G Neo3PDRW planar ribbon tweet.
If you haven't already mocked this idea up in your head, just picture the Tower of Sauron from the Lord of the Rings. 😀
Setting aside the details, I like the idea of a omnipole woofer/lo-mid and a dipole hi-mid/tweet for my surround speaker duties.
Can you guys please help me sort through the logistics of this theoretical design?
Some notes and concerns I already have in mind:
Thoughts? This is just a pipe dream... No pun intended
PipeDREAM no more. Here it is! (Link to entire build album)
I've recently been bitten by the OB/Dipole bug and have just built myself a set of 3-way actively crossed mains (Alpha15A, Dayton PS220-8, B&G Neo3PDRW (dipole operation) and am just falling in love with the intoxicating sound of open baffle loudspeakers. I can and probably will put together a build thread so I can hopefully get some feedback on this build.
I plan on using them (and a OB/Dipole center channel I'll be designing) for home theater duties in addition to music. Now I need to replace my very old and very laughable rear-speaker situation. I want dipole operation, but I also want them to be able to make some bass. I'll want the mid/tweet to be approx 30-36" off the ground. I don't want them to be too bulky either. What do?
Enter the LXMini. I am not entirely opposed to just building the kit as S.Linkwitz specified-- and that would probably the smartest and easiest idea, but where's the fun and DIY spirit in that? I fancy using different drivers. Specifically, the Dayton PS180-8 and the B&G Neo3PDRW planar ribbon tweet.
If you haven't already mocked this idea up in your head, just picture the Tower of Sauron from the Lord of the Rings. 😀
Setting aside the details, I like the idea of a omnipole woofer/lo-mid and a dipole hi-mid/tweet for my surround speaker duties.
Can you guys please help me sort through the logistics of this theoretical design?
Some notes and concerns I already have in mind:
- Am concerned about the likely possibility that suspending that Neo3PDRW tweet directly centered above the woofer, that the radiated sound from that driver will resonate the very thin and delicate planar ribbon tweet, and either damage it or at the very least cause distortion. This would probably be a deal breaker. Do you agree?
- I was thinking of a 2000-2500hz x-over point-- unsure of type/slope as of yet.
- I have a MiniDSP 8x8 fed by a pre/pro, and 16x100w (@ 4ohm) high quality amplifier channels on tap to drive these.
- I also have a UMIK-1 acoustical measurement microphone, RTA software, an oscilloscope, and REW to work with.
Thoughts? This is just a pipe dream... No pun intended
PipeDREAM no more. Here it is! (Link to entire build album)
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Bump.
Anybody have any advice?
I think my biggest question revolves the top bullet-point; will the B&G Neo3 PDRW resonate undesirably if placed fairly close to another larger driver, directly in its radiation path?
Anybody have any advice?
I think my biggest question revolves the top bullet-point; will the B&G Neo3 PDRW resonate undesirably if placed fairly close to another larger driver, directly in its radiation path?
Isn't the planar tweeter just as close in your current implementation as well? I'd give it a try and see what happens.
I suppose it is in a way. It's on the same plane and facing the same direction as the PS220-8 in my OB setup. I know sound waves travel along the baffle, and as such that would travel over the tweeter in this arrangement. But I'm not sure if the vibrations imparted on the planar from this arrangement would be equal to having the planar placed directly in front of the midrange radiator. Still learning how sound propagates in a very grassroots manner 🙂
No, this will not be an issue.
I was thinking of a 2000-2500hz x-over point-- unsure of type/slope as of yet.
I have a MiniDSP 8x8 fed by a pre/pro, and 16x100w (@ 4ohm) high quality amplifier channels on tap to drive these.
I also have a UMIK-1 acoustical measurement microphone, RTA software, an oscilloscope, and REW to work with.
Thoughts? This is just a pipe dream... No pun intended
As long as you take measurements, and base your choice of crossover design on those, you can succeed. Measure on and off axis, and look for off-axis peaks and dips. You want to have as few of these as possible. Using the smallest baffle (or no baffle) helps in this regard.
I wasn't initially planning on running it completely completely nude; I planned on using the same flush-mount bezel as pictured in my 3-way OB mains, counter-sunk into a 1/2" thick MDF baffle (not sure on size/shape/design/implementation yet). I know circle baffles are bad. How about oval? A different shape?
I'm concerned about running the Neo3 completely nude/suspended/hanging/swinging or whatever you want to call it, because since the membrane alone is not all that large, I would think that lower frequency roll off would be an issue. My ideal 2-2.5khz crossover point might be too low for the Neo3 in this scenario? Do you suppose this would be preferable to running it on a 5-6" total overall dia round baffle as described above?
I will do some preliminary RTA/REW testing and comparative analyses on the driver, both on a baffle as well as completely nude. Indoors and outdoors (to negate room reflections).
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Hang up your Neo3, nude, and measure the frequency response. If you are concerned about it, measure distortion as you increase level and see what you can tolerate. Don't exceed max recommended input power.
PICS!
Here they are guys...
Quick specs:
B&G Neo3 PDRW (dipole operation; rear cup removed)
Dayton PS180-8 (sealed 5" x 28" ABS pipe + heavy damping the entire length of the line) Approx .3 ft3 not factoring for damping material.
Tweeters are on-axis with listener ears @ seated position in couch. Approx 34-36" from ground.
Behringer DAC -> Toslink Optical -> MiniDSP
Active xover & EQ via MiniDSP 2x8
Solid State amplification from ATI amplifiers, capable of 100w/ch @ 4ohm and 80 @ 8ohm.
DIY Pipedreams - Imgur
I just finished them this morning at 3am, and had to sleep and go to work. So I only got to listen to them for a brief time (at 3am) at low volume.
First impressions: The imaging!!! Oh the glorious imaging! 😱
From the second I played the first song on these after setting my xover points (0hz-to-1800hz for midbass section and 1800hz mid-to-tweet) and flattening my EQ settings, the speakers literally vanished. Completely transparent. So much so that it is almost eerie! They're just tossed in my living room, carelessly positioned directly in front of my OB mains, which have been disconnected temporarily so that I can use their MiniDSP 2x8 to test these. Every single track, the speakers just disappeared. They have the same MASSIVE and very live soundstage that my OB mains deliver too. It is very peculiar to hear such a massive sound/stage and well defined imaging come from such physically small speakers. Since I'm running the Neo3PDRW as a dipole, and the woofer is essentially an omni-directional monopole (with excellent off-axis dispersion up to my xover point), the music sounds perfect whether you're standing in front of or behind them.
Voicing matches my OB mains based on the 8" version of this Dayton point source driver, and another Neo3 tweet-- both open baffle. The bass is admittedly a bit thin without EQ. With EQ it is not bad, but still not impressive or outstanding in any way. The midrange being produced from the Dayton 6.5" is fast, articulate, clear, and with a touch of EQ, nice and full. The Neo3 PDRW is as good in this situation as it is in my open baffles-- which is nothing short of awesome. Perhaps even more transparent! I haven't had enough time auditioning them yet though, so I don't want to say too much more than this for now.
All in all, I'm *very* happy with the results so far. All I had planned was to use these as my rear surround speakers, parked beside my couch, and fairly nearfield to my ears. With the imaging that I'm hearing so far, I am VERY interested to run some DTS movies and quadraphonic DTS music through them.
If I wanted to run these as mains (I would be delighted to if I wasn't so attached to my larger/more capable OB mains), I would consider making these a three-way and integrate a pair of stereo subwoofers. I'm thinking about an 8" woofer with decent excursion capabilities (10-15mm xmax) and power handling (150-350w) coupled to a passive radiator in a sealed box (passive radiator b/c I want ported-like extension in a VERY small space, while maintaining good group delay, responsiveness and accuracy). The notion is that I would essentially build that box around the current base, so the pipe runs through the center of the subwoofer enclosure, but is not acoustically significant in its operation, other than displacing box volume. The passive would be on the opposing face of the active woofer.
Also, despite my valiant efforts to stuff the bajeezus out of these pipes with polyfill (but not too densely), and remove any sharp edges inside the enclosure, the pipe does still resonate some. It didn't ring, but I could feel a good deal of vibration being transferred through the pipe from the speaker. To address this, I thought why not just go out and get a 6" ABS pipe and run it over the existing 5" pipe, and fill the open cavity with sand...? Super cheap and simple and I think would help quell any significant remaining resonances. Thoughts?
Here they are guys...
Quick specs:
B&G Neo3 PDRW (dipole operation; rear cup removed)
Dayton PS180-8 (sealed 5" x 28" ABS pipe + heavy damping the entire length of the line) Approx .3 ft3 not factoring for damping material.
Tweeters are on-axis with listener ears @ seated position in couch. Approx 34-36" from ground.
Behringer DAC -> Toslink Optical -> MiniDSP
Active xover & EQ via MiniDSP 2x8
Solid State amplification from ATI amplifiers, capable of 100w/ch @ 4ohm and 80 @ 8ohm.
DIY Pipedreams - Imgur
I just finished them this morning at 3am, and had to sleep and go to work. So I only got to listen to them for a brief time (at 3am) at low volume.
First impressions: The imaging!!! Oh the glorious imaging! 😱
From the second I played the first song on these after setting my xover points (0hz-to-1800hz for midbass section and 1800hz mid-to-tweet) and flattening my EQ settings, the speakers literally vanished. Completely transparent. So much so that it is almost eerie! They're just tossed in my living room, carelessly positioned directly in front of my OB mains, which have been disconnected temporarily so that I can use their MiniDSP 2x8 to test these. Every single track, the speakers just disappeared. They have the same MASSIVE and very live soundstage that my OB mains deliver too. It is very peculiar to hear such a massive sound/stage and well defined imaging come from such physically small speakers. Since I'm running the Neo3PDRW as a dipole, and the woofer is essentially an omni-directional monopole (with excellent off-axis dispersion up to my xover point), the music sounds perfect whether you're standing in front of or behind them.
Voicing matches my OB mains based on the 8" version of this Dayton point source driver, and another Neo3 tweet-- both open baffle. The bass is admittedly a bit thin without EQ. With EQ it is not bad, but still not impressive or outstanding in any way. The midrange being produced from the Dayton 6.5" is fast, articulate, clear, and with a touch of EQ, nice and full. The Neo3 PDRW is as good in this situation as it is in my open baffles-- which is nothing short of awesome. Perhaps even more transparent! I haven't had enough time auditioning them yet though, so I don't want to say too much more than this for now.
All in all, I'm *very* happy with the results so far. All I had planned was to use these as my rear surround speakers, parked beside my couch, and fairly nearfield to my ears. With the imaging that I'm hearing so far, I am VERY interested to run some DTS movies and quadraphonic DTS music through them.
If I wanted to run these as mains (I would be delighted to if I wasn't so attached to my larger/more capable OB mains), I would consider making these a three-way and integrate a pair of stereo subwoofers. I'm thinking about an 8" woofer with decent excursion capabilities (10-15mm xmax) and power handling (150-350w) coupled to a passive radiator in a sealed box (passive radiator b/c I want ported-like extension in a VERY small space, while maintaining good group delay, responsiveness and accuracy). The notion is that I would essentially build that box around the current base, so the pipe runs through the center of the subwoofer enclosure, but is not acoustically significant in its operation, other than displacing box volume. The passive would be on the opposing face of the active woofer.
Also, despite my valiant efforts to stuff the bajeezus out of these pipes with polyfill (but not too densely), and remove any sharp edges inside the enclosure, the pipe does still resonate some. It didn't ring, but I could feel a good deal of vibration being transferred through the pipe from the speaker. To address this, I thought why not just go out and get a 6" ABS pipe and run it over the existing 5" pipe, and fill the open cavity with sand...? Super cheap and simple and I think would help quell any significant remaining resonances. Thoughts?
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I'm fascinated by what you are doing there, sfhobbles. I have had a similar experience myself. Like you say, the speaker disappears. 🙂
There's actually good reason to think there might be some science behind it too. It's common enough in filtering that a 90 degree phase change occurs. But whether that is strictly a phase phenomena, or a right angled physical alignment is open to debate. The root of -1 called i by mathematicians, or called j by engineers (to avoid confusion with current) can be interpreted either way.
For sure, the tweeter actually does very little above 3kHz, maybe adds a a bit of air. I tested that by turning it upside down.
Personally, I'm gobsmacked how good these speakers sound with the tweeter pointing upwards. It looks like I have forgotten to screw it in. Have we reinvented the omnidirectional speaker? I really don't know! 😀
There's actually good reason to think there might be some science behind it too. It's common enough in filtering that a 90 degree phase change occurs. But whether that is strictly a phase phenomena, or a right angled physical alignment is open to debate. The root of -1 called i by mathematicians, or called j by engineers (to avoid confusion with current) can be interpreted either way.
For sure, the tweeter actually does very little above 3kHz, maybe adds a a bit of air. I tested that by turning it upside down.
Personally, I'm gobsmacked how good these speakers sound with the tweeter pointing upwards. It looks like I have forgotten to screw it in. Have we reinvented the omnidirectional speaker? I really don't know! 😀
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