The only concern I'd have with that is the driver break up will start to occur in a 15" around 2 k maximum, and thats only 1 octave away, so 6 or 12 db down on a simple non-digital crossover.
I understand the concern with the dispersion of a larger driver, but as such life is always a compromise...
Owen
I understand the concern with the dispersion of a larger driver, but as such life is always a compromise...
Owen
Hi all,
Not to belabor the point ...oh no not at all.... and here we go again...
The EnABLE cones, from my experience, all have dispersion angles that are controlled by the cone angle of incidence. If the driver has a dome, and the dome is treated, you can be certain of getting significantly smoothed high frequencies and they will be controlled in dispersion by the cone walls.
Not kidding here, but, I have almost no experience with open center drivers. Although the highs will be just as smooth, I am not dead certain that the dispersion will be just as it is when the dome is present.
A center horn can also be integrated much more smoothly with a treated cone, but , you will have to ditch the screen, and you want to, trust me.
Bud
Not to belabor the point ...oh no not at all.... and here we go again...
The EnABLE cones, from my experience, all have dispersion angles that are controlled by the cone angle of incidence. If the driver has a dome, and the dome is treated, you can be certain of getting significantly smoothed high frequencies and they will be controlled in dispersion by the cone walls.
Not kidding here, but, I have almost no experience with open center drivers. Although the highs will be just as smooth, I am not dead certain that the dispersion will be just as it is when the dome is present.
A center horn can also be integrated much more smoothly with a treated cone, but , you will have to ditch the screen, and you want to, trust me.
Bud
My own choice for best voice reproduction is no more than 6 to 8 inches in diameter for a midrange without crossovers at voice frequencies.
Baffle trials with a modified Alpha 6 then become possible with LF helpers gradually crossing into the upper bass range.
Hi John,
I am curious about your comment for the rear wave being angled downwards when you tilt an OB. Presumably you mean where a FR driver is completely open backed.
If there was some felt like damping behind the main driver and the baffle was sitting on the floor, do you expect the same thing to be deleterious, especially for a system that will need to be domesticated and sit closer to a room corner?
On the same tack, surely this would not affect LF only drivers mounted at floor level?
Cheers ........ Graham.
Baffle trials with a modified Alpha 6 then become possible with LF helpers gradually crossing into the upper bass range.
Hi John,
I am curious about your comment for the rear wave being angled downwards when you tilt an OB. Presumably you mean where a FR driver is completely open backed.
If there was some felt like damping behind the main driver and the baffle was sitting on the floor, do you expect the same thing to be deleterious, especially for a system that will need to be domesticated and sit closer to a room corner?
On the same tack, surely this would not affect LF only drivers mounted at floor level?
Cheers ........ Graham.
swak said:
Looking at the 6ND410 data, it has a piston-band efficiency of 98 dB/metre. Two of them in parallel would be around 5~6 dB more, or about 103~104 dB. However, with the limited Xmax a true crossover no lower than 300 Hz with a 12 dB/oct slope would be wise.
The horizontal and vertical dispersion would start to diverge around 1 kHz in classic MTM fashion, with an implication that direct-arrival freq response curves no longer mirror the subjective impression of frequency response (this was my experience with the Ariel). As mentioned previously, a half-crossover could roll off the lower driver around 1 kHz, offsetting the gain from directivity we see in the published curves. This leaves the lower driver with 1.5 octave effective bandwidth, which begs the question of using it at all, since it's only "helping" in the 300 to 1 kHz bandwidth.
The added complexity of the polar pattern - using both together or with half-crossover - bothers me a little bit. There are a lot of polar-pattern transitions in the 200 to 5 kHz range, making the job of tuning the crossover subjectively a lot more difficult. I've designed 4-way speakers before, and tuning the crossover to be subjectively flat takes a very long time with all that complexity going on.
I guess this approach, with a full crossover somewhere around 300 Hz, and the onset of vertical beaming at 1~2 kHz, is more suited for folks who are comfortable with 3 or 4-way active-crossover systems, line arrays, or big, complex speaker systems. I've done 'em myself, but I've never felt the results justified the huge, years-long effort that goes into them.
The "telephone bandwidth" of 500 Hz to 3 kHz is a region where very small changes in directivity, deviations from flatness, or shifts in tonal character are extremely audible. Transgressing this bandwidth with multiple drivers of different sonic characters is the downfall of most overcomplex hifi speakers, and the reason why they don't sound integrated or coherent - unnatural, in other words, the opposite of a fullranger.
In other words, one or two 6ND410's would work fine, measure well, have plenty of power-handling, etc. etc. - but it takes away from the underlying design philosophy of what I'm trying to do - a wideband pro-quality driver with high power-handling that is augmented by complementary drivers in the bass and a HF transducer that comes in at a fairly high frequency. It reverts the design to a more traditional 3-way with a mid driver array - to me, this is the traditional "high-end" sound, which some like, but I'm not one of them. I'm guessing some of the readers of this thread would like it just fine, though - this is a matter of personal taste.
As for the sonically bad effects of beaming in a 12" mid driver, well, I very much liked the image, spatial, and 3-dimensional qualities of the Bastani Apollo. I didn't much care for the Prometheus, but then, the driver is completely different, and the whole Bastanis concept is critically reliant on the sonic goodness of the widerange driver, which uses no crossover at all, on either end. There's an actively-powered monopole sub that comes in around 160 ~ 200 Hz, and a horn tweeter with a phenolic diaphragm that comes in at some high frequency.
I'm not quite as much a purist as Bob Bastani, and am willing to do things like equalize and have complementary groups of drivers to flatten out the response. But I don't want to go as far as Siegfried Linkwitz, with multi-amping, low-efficiency audiophile drivers, and extensive line-level equalization. Having met both designers and spoken with each for several hours, I have a good idea where they're coming from, and what they want to accomplish.
My goals are different enough I don't feel I'm "ripping off" either of them - I'm not using their techniques directly, and my end goals are a bit different as well. It's kind of a middle ground between the two, maybe a bit more tilted in the Bastani direction.
The whole exact-control-of-polar-pattern is a religion I'm not a member of, having not been that impressed with any speaker that hews to this design philosophy. I'm especially unconvinced by the 90-degree controlled-dispersion school - maybe for PA use, but I don't think it works all that well in domestic environments. The claim of improved imaging in particular I find to be inapplicable - to my ears, speakers that follow these home-theater-influenced philosophies sound dry and closed-in, with not very good reproduction of depth and extra-width effects (which are part of any normal stereo recording).
Which is why I can see the need for rear-facing tweeters if HF directivity in the front is on the narrow side. In fact, I can see the need for two rear tweeters, one facing straight back and looking upwards at the junction between the rear wall and ceiling, and another facing sideways and looking up at the junction between the side wall and the ceiling.
Ideally, the "side" HF enhancement tweeter could be connected in the old Polk cross-channel arrangement, with the Left side tweeter having a +L-R feed, and the Right side having a -L+R feed. This way the antiphase signal - which is mostly reverb - keeps the ambient impression wide at the highest frequencies, countering the HF narrowing that is typical in narrow-dispersion speakers.
I remember references to "Stiff cones " and "pistonic behavior" here.
I believe that the old 15-16" drivers such as Altec had rather flexible cones, which allowed them to decouple for various frequencies. The the whole cone produced the low frequencies, the smaller area close to the center produced the higher frequencies.As the higher frequencies were produced by a smaller diameter of the cone, they had better dispersion. Smaller diameter voice coils seem to promote this characteristic. Is this impression correct?
I believe most "modern" PA drivers have stiff cones and huge voice coils. They are made to reproduce a narrow band of frequencies and handle lots of power. These characteristics are not necessarily what we want here. Now we also might not want a flexible cone either, for the disadvantages it brings, but we shouldn't be surprised that most current 12" drivers have a narrow range of response.
This is one of the advantages of the Eminence Beta, it is a more "old school" driver- small voice coil, more flexible cone. ( I think they recently changed the cone material and suspension though) Modifying this model is commonly done not just because it is cheap, but als ofor these other reasons.
I believe that the old 15-16" drivers such as Altec had rather flexible cones, which allowed them to decouple for various frequencies. The the whole cone produced the low frequencies, the smaller area close to the center produced the higher frequencies.As the higher frequencies were produced by a smaller diameter of the cone, they had better dispersion. Smaller diameter voice coils seem to promote this characteristic. Is this impression correct?
I believe most "modern" PA drivers have stiff cones and huge voice coils. They are made to reproduce a narrow band of frequencies and handle lots of power. These characteristics are not necessarily what we want here. Now we also might not want a flexible cone either, for the disadvantages it brings, but we shouldn't be surprised that most current 12" drivers have a narrow range of response.
This is one of the advantages of the Eminence Beta, it is a more "old school" driver- small voice coil, more flexible cone. ( I think they recently changed the cone material and suspension though) Modifying this model is commonly done not just because it is cheap, but als ofor these other reasons.
Speak of the devil, I just looked up the Apollo and found this:
http://www.audioasylum.com/forums/bastanis/messages/470.html
here's the Apollo:
http://www.bastanis.com/catalog/pro...d=131&osCsid=a30e702d94bdae03b0233290ef3c8154
http://www.audioasylum.com/forums/bastanis/messages/470.html
here's the Apollo:
http://www.bastanis.com/catalog/pro...d=131&osCsid=a30e702d94bdae03b0233290ef3c8154
Graham Maynard said:
Yes, any kind of OB alignment excluding if you heavily damped rear wave for the main driver. I wouldn't say it's necessarily detrimental, but typically if you fire the rear wave angled down, it lowers the soundstage quite noticeably.
Lynn's a box guy, so I have to keep reminding him not to forget about the rear wave.
Variac said:
speaking of Apollo, the Llambda Apollo was probably one of the best 15s ever made... last comment Nick had on them said it would cost 10k in tooling to put them back in production... John at Styke (called something else now) would know who has the rights to the design.
http://www.diyaudio.com/forums/attachment.php?s=&postid=775848&stamp=1133022200
http://www.diyaudio.com/forums/showthread.php?postid=792333#post792333
dave
The Variable Geometry Solution
Yup, you're right, it's 3 dB, so the net piston band efficiency would be 101 dB/metre, not the 104 dB/metre mentioned earlier. In practice, phase addition isn't always precisely zero degrees, and driver efficiency mismatches exist also, so it can be a fraction of a dB or so down from theoretical maximums.
I also want to thank swak for the earlier suggestion about the dual 6ND410 - it got me thinking about the conversations I had years ago with Siegfried Linkwitz.
When I first heard Linkwitz's Beethovens's, I was deeply impressed. Superbly spacious sound, beautifully balanced, powerful, dynamic, with much of the effortlessness and ease of an electrostatic, but none of the hard-to-set-up crankiness and questionable midbass of electrostats. But the electronics - oogh - multi-amping with six or eight 200-watt amps, and a zillion op-amps with the mandatory 6 dB/octave frequency contouring demanded by the 1/f transition of the flat baffle. A lot of wattage of the amplifiers disappeared into that 1/f transition, and it worked the Scan-Speak drivers hard. Part of the reason for all the 24 dB/octave active crossovers was to separate the frequency bands, keep the excursion for each set of drivers in the reasonable range, and keep overall system IM distortion at reasonable levels.
Liked the sound, but that implementation ... hmmm, not for Mr. Triode here. That was several years ago at the CES. Then I heard the Apollo's at the 2005 RMAF. Hello, efficient dipoles driven by a 20-watt amplifier - and that played LOUD, in horn territory, way louder than anything Scan-Speak makes. And Bob, unlike Siegfried, broke all the rules - the big, heavily-treated Alnico-magnet 12" driver is operating far outside the piston band, there's no highpass crossover at 200 Hz to "protect" it from big bad bass, and the baffle seemed a lot narrower than theory demanded. Gary Pimm measured a -3 dB 220 Hz rolloff from the 15-inch-wide baffle - that seemed a lot smaller than theory demanded.
I thought about what I'd heard for some time afterward. I did a little math calculating the path-length differences and adding them together again as vector sums, and was surprised to find the -3 dB point is actually somewhere between 1/6th and 1/8th of a wavelength for an open baffle. So the required baffle in order to meet a subwoofer wasn't as big as I thought.
About a year ago I had an insight and saw something that I think Linkwitz may have missed. Driver efficiency, frequency response, and power-handling drop by 6 dB/octave for a dipole compared to a monopole (below the 1/f frequency, set by the baffle size). This is obvious and we all know this.
Linkwitz solves this by applying a compensating 6 dB/oct lift (an integrator) at all frequencies below the 1/f, and splitting the frequency bands so no set of drivers needs to handle much more than a couple of octaves, thus limiting the overall boost necessary in any frequency band.
But ... there's another way to solve this. You can build a cascade of drivers, doubling the driver count as you go downward, octave by octave. Say the 1/f frequency is -3 dB down at 200 Hz. You have one fullrange driver, two drivers working in tandem at 200 Hz and below, four drivers working together at 100 Hz and below, and so on.
The crossovers are a simple low-pass cascade, and are NOT in series with each other. Instead, the #1 driver is working full-range, #2 driver has a 1st-order lowpass at 200 Hz, and #3 and #4 have a 1st-order lowpass at 100 Hz. All of them work together below 100 Hz, and if it desirable for the fullrange driver to be lowpassed at 1 ~ 4 kHz, they all share that filter, in additional to their individual filter sections.
I think of this as a variable-geometry driver that varies its area with frequency. The number of drivers exactly compensates for the 1/f loss, keeping efficiency and frequency response flat, and not requiring any 1/f response shaping, passive or active. No extra amplifier power is required - this is the big one for me - since the driver efficiencies neatly compensate for the dipole 1/f loss.
By controlling the degree of overlap, the response can be built up or reduced in the frequency range that is most room-sensitive. All it takes are simple tapped inductors.
Of course, what makes it all possible are the long wavelengths at these frequencies. The Japanese have a saying, "Nature is as cruel as it is kind." The very thing that we're struggling against - the 1/f loss due to growing wavelengths - is exactly what makes the variable-geometry solution possible. Things get much more awkward in the midrange and up, with all kinds of annoying lobing problems from vertical arrays. But at 200 Hz on down, with those generous 6-foot wavelengths, no problem. Everything is in phase thanks to the 1st-order lowpass filters working in parallel, so the array works as one at the lowest frequencies.
There are other refinements that are possible. If drivers are mounted with the edge of their frames almost touching the floor (and I mean an inch or less), the floor forms an image just below the driver. This is another pair of drivers for free. The phase cohesion is destroyed when the driver is its own diameter (or higher) above the floor, so the near-floor mounting should be reserved for the most low-frequency part of the array. But it's there if you want it.
The dipole shape is interesting as well. Boxes, as we know, create standing waves thanks to the parallel surfaces inside them. But one type of wing hasn't been investigated, and it's quite simple: just put a wing on one side, but not the other! No parallel surfaces, no standing wave. So if the driver is placed asymmetrically on the front baffle (something you want to do anyway) put the side wing on the side the driver is closest to. This increases the path-length without setting up the standing waves of a W or H-box, or even the usual wings on both sides. No parallel surfaces, no delayed reflections.
Over all of the earlier postings, I was alluding to these concepts without really spelling them out clearly. Sorry about that. It was swak's suggestion that made me think this through, generalizing it into an overall principle that can be adapted to any dipole speaker.
P.S., thanx to johninCR for the reminder about the focus location for the phantom rear image. Stereo images that are too close to the floor sound terrible, you're quite right, and the slight tilt to the OB will certainly create a phantom that hovers close to the floor. Not desirable. The OB needs to be vertical, not tilted backwards.
As for the bass array, well, that's a different story. When the wavelengths are similar to room dimensions - and 6 feet is starting to get there - the localizations, especially vertical, start to merge together. Besides, that corresponds to real-world images, with bass instruments sitting close to the floor. Treble and mids at the top, and bass at the floor, that corresponds to real life.
planet10 said:
Yup, you're right, it's 3 dB, so the net piston band efficiency would be 101 dB/metre, not the 104 dB/metre mentioned earlier. In practice, phase addition isn't always precisely zero degrees, and driver efficiency mismatches exist also, so it can be a fraction of a dB or so down from theoretical maximums.
I also want to thank swak for the earlier suggestion about the dual 6ND410 - it got me thinking about the conversations I had years ago with Siegfried Linkwitz.
When I first heard Linkwitz's Beethovens's, I was deeply impressed. Superbly spacious sound, beautifully balanced, powerful, dynamic, with much of the effortlessness and ease of an electrostatic, but none of the hard-to-set-up crankiness and questionable midbass of electrostats. But the electronics - oogh - multi-amping with six or eight 200-watt amps, and a zillion op-amps with the mandatory 6 dB/octave frequency contouring demanded by the 1/f transition of the flat baffle. A lot of wattage of the amplifiers disappeared into that 1/f transition, and it worked the Scan-Speak drivers hard. Part of the reason for all the 24 dB/octave active crossovers was to separate the frequency bands, keep the excursion for each set of drivers in the reasonable range, and keep overall system IM distortion at reasonable levels.
Liked the sound, but that implementation ... hmmm, not for Mr. Triode here. That was several years ago at the CES. Then I heard the Apollo's at the 2005 RMAF. Hello, efficient dipoles driven by a 20-watt amplifier - and that played LOUD, in horn territory, way louder than anything Scan-Speak makes. And Bob, unlike Siegfried, broke all the rules - the big, heavily-treated Alnico-magnet 12" driver is operating far outside the piston band, there's no highpass crossover at 200 Hz to "protect" it from big bad bass, and the baffle seemed a lot narrower than theory demanded. Gary Pimm measured a -3 dB 220 Hz rolloff from the 15-inch-wide baffle - that seemed a lot smaller than theory demanded.
I thought about what I'd heard for some time afterward. I did a little math calculating the path-length differences and adding them together again as vector sums, and was surprised to find the -3 dB point is actually somewhere between 1/6th and 1/8th of a wavelength for an open baffle. So the required baffle in order to meet a subwoofer wasn't as big as I thought.
About a year ago I had an insight and saw something that I think Linkwitz may have missed. Driver efficiency, frequency response, and power-handling drop by 6 dB/octave for a dipole compared to a monopole (below the 1/f frequency, set by the baffle size). This is obvious and we all know this.
Linkwitz solves this by applying a compensating 6 dB/oct lift (an integrator) at all frequencies below the 1/f, and splitting the frequency bands so no set of drivers needs to handle much more than a couple of octaves, thus limiting the overall boost necessary in any frequency band.
But ... there's another way to solve this. You can build a cascade of drivers, doubling the driver count as you go downward, octave by octave. Say the 1/f frequency is -3 dB down at 200 Hz. You have one fullrange driver, two drivers working in tandem at 200 Hz and below, four drivers working together at 100 Hz and below, and so on.
The crossovers are a simple low-pass cascade, and are NOT in series with each other. Instead, the #1 driver is working full-range, #2 driver has a 1st-order lowpass at 200 Hz, and #3 and #4 have a 1st-order lowpass at 100 Hz. All of them work together below 100 Hz, and if it desirable for the fullrange driver to be lowpassed at 1 ~ 4 kHz, they all share that filter, in additional to their individual filter sections.
I think of this as a variable-geometry driver that varies its area with frequency. The number of drivers exactly compensates for the 1/f loss, keeping efficiency and frequency response flat, and not requiring any 1/f response shaping, passive or active. No extra amplifier power is required - this is the big one for me - since the driver efficiencies neatly compensate for the dipole 1/f loss.
By controlling the degree of overlap, the response can be built up or reduced in the frequency range that is most room-sensitive. All it takes are simple tapped inductors.
Of course, what makes it all possible are the long wavelengths at these frequencies. The Japanese have a saying, "Nature is as cruel as it is kind." The very thing that we're struggling against - the 1/f loss due to growing wavelengths - is exactly what makes the variable-geometry solution possible. Things get much more awkward in the midrange and up, with all kinds of annoying lobing problems from vertical arrays. But at 200 Hz on down, with those generous 6-foot wavelengths, no problem. Everything is in phase thanks to the 1st-order lowpass filters working in parallel, so the array works as one at the lowest frequencies.
There are other refinements that are possible. If drivers are mounted with the edge of their frames almost touching the floor (and I mean an inch or less), the floor forms an image just below the driver. This is another pair of drivers for free. The phase cohesion is destroyed when the driver is its own diameter (or higher) above the floor, so the near-floor mounting should be reserved for the most low-frequency part of the array. But it's there if you want it.
The dipole shape is interesting as well. Boxes, as we know, create standing waves thanks to the parallel surfaces inside them. But one type of wing hasn't been investigated, and it's quite simple: just put a wing on one side, but not the other! No parallel surfaces, no standing wave. So if the driver is placed asymmetrically on the front baffle (something you want to do anyway) put the side wing on the side the driver is closest to. This increases the path-length without setting up the standing waves of a W or H-box, or even the usual wings on both sides. No parallel surfaces, no delayed reflections.
Over all of the earlier postings, I was alluding to these concepts without really spelling them out clearly. Sorry about that. It was swak's suggestion that made me think this through, generalizing it into an overall principle that can be adapted to any dipole speaker.
P.S., thanx to johninCR for the reminder about the focus location for the phantom rear image. Stereo images that are too close to the floor sound terrible, you're quite right, and the slight tilt to the OB will certainly create a phantom that hovers close to the floor. Not desirable. The OB needs to be vertical, not tilted backwards.
As for the bass array, well, that's a different story. When the wavelengths are similar to room dimensions - and 6 feet is starting to get there - the localizations, especially vertical, start to merge together. Besides, that corresponds to real-world images, with bass instruments sitting close to the floor. Treble and mids at the top, and bass at the floor, that corresponds to real life.
All this crazy brainstorming is paying off!
I discussed something slightly similar in this thread:
These posts are kind of in the middle of the discussion. Clearly we didn't have a lot of theory to back us up..
http://www.diyaudio.com/forums/showthread.php?postid=398189#post398189
http://www.diyaudio.com/forums/showthread.php?postid=400445#post400445
The idea was to use about 4 of the same driver in a vertical array rolled off at different frequencies for baffle step correction, to augment the bass, and also use one of them as a midrange.. We never decided if the mid, while identical, would reproduce full range including bass, or just be a mid.....I leaned toward having just be a mid to try to keep the excursion from overloading it.
Since the response of each is identical, the drivers should certainly not interact strangely when they overlap. Except for lobing concerns of course...
I discussed something slightly similar in this thread:
These posts are kind of in the middle of the discussion. Clearly we didn't have a lot of theory to back us up..
http://www.diyaudio.com/forums/showthread.php?postid=398189#post398189
http://www.diyaudio.com/forums/showthread.php?postid=400445#post400445
The idea was to use about 4 of the same driver in a vertical array rolled off at different frequencies for baffle step correction, to augment the bass, and also use one of them as a midrange.. We never decided if the mid, while identical, would reproduce full range including bass, or just be a mid.....I leaned toward having just be a mid to try to keep the excursion from overloading it.
Since the response of each is identical, the drivers should certainly not interact strangely when they overlap. Except for lobing concerns of course...
Re: Re: The Variable Geometry Solution
A better and more realistic way is to double the drivers for the first octave and double the "D" for the second octave. Tapering the baffle using wings, combined with appropriate consideration of the floor reinforcement has the potential of a very simple XO solution. Once you get close, then you can use placement distance from the front wall to fine tune bass response. If you have a fixed placement, then you have to design with that in consideration and leave room for flexibility, since room construction is not created equal.
Recent pages brings up my biggest problem with the purely technical approach adapted from boxed speaker design. You have to leave those crutches behind to some extent when designing OBs. Otherwise you end up with the complexities that SL uses, some of which end up contradictory to each other along the way.
With OB's the physical structure can help counteract a lot of the sub 500hz problems that open alignments introduce. That ends up being the simple part of the equation, with what happens above that point being less clearcut.
MJL21193 said:
Quoted above is the single most intelligent idea I've read here.
A better and more realistic way is to double the drivers for the first octave and double the "D" for the second octave. Tapering the baffle using wings, combined with appropriate consideration of the floor reinforcement has the potential of a very simple XO solution. Once you get close, then you can use placement distance from the front wall to fine tune bass response. If you have a fixed placement, then you have to design with that in consideration and leave room for flexibility, since room construction is not created equal.
Recent pages brings up my biggest problem with the purely technical approach adapted from boxed speaker design. You have to leave those crutches behind to some extent when designing OBs. Otherwise you end up with the complexities that SL uses, some of which end up contradictory to each other along the way.
With OB's the physical structure can help counteract a lot of the sub 500hz problems that open alignments introduce. That ends up being the simple part of the equation, with what happens above that point being less clearcut.
A new thread has been made from copies of posts in this and 2 other threads on EnAble + Mamboni
http://www.diyaudio.com/forums/showthread.php?s=&threadid=100399
dave
http://www.diyaudio.com/forums/showthread.php?s=&threadid=100399
dave
Here's a terrific amount of information about prosound drivers by ScottG, Paul W, MBK and many others.
The results they got from the 18Sound drivers look very promising; thanks, guys, the work you put into this thread is most impressive, and not found anywhere else that I've come across. What you've already discovered will definitely come in handy for the new system, along with EnABL, Mamboni, and all the dipole information that's turned up in this thread so far.
The results of combining prosound drivers with the cone - and open baffle - treatments should be most interesting. Whether EnABL and/or Mamboni can overcome the many faults of coaxes, though, remains to be seen.
The results they got from the 18Sound drivers look very promising; thanks, guys, the work you put into this thread is most impressive, and not found anywhere else that I've come across. What you've already discovered will definitely come in handy for the new system, along with EnABL, Mamboni, and all the dipole information that's turned up in this thread so far.
The results of combining prosound drivers with the cone - and open baffle - treatments should be most interesting. Whether EnABL and/or Mamboni can overcome the many faults of coaxes, though, remains to be seen.
Re: Re: Re: The Variable Geometry Solution
OK, I'll bite, what's "double the D"? Diameter of the driver? Distance to the floor?
I'm in partial agreement with the comments about SL's approach - the Bastani experience illuminated just how good "doing it wrong" can sound. I'm looking forward to finding out where all of this theory fails to apply to the real world - the much simpler experience of designing the Ariel showed how far off the literature about MTM's were, something I didn't expect at the time. For years, I'd read how wonderful MTM's were, and how you could slap together any old crossover and it made them perfect.
Yeah, right. In practice it was fiendishly difficult to align for subjectively flat response - and with extremely flat drivers, too. It took quite a while to dawn on me that I was trying to work with two dissimilar sets of freq resp curves at once (direct first-arrival sound vs total energy into the room, with the first 3 mSec removed). MTM's are actually kind of nasty to work with, with odd midrange colorations that are phase dependent. It took quite a bit of phase-twiddling on the midbass drivers to get the thing to integrate and sound like one driver.
Based on that experience alone, I'm sure that all those hypercomplex graphs and theory are going to fall down - badly - when I start measuring and listening. What's really strange is all the endless wrangling about the ideal polar pattern vs frequency, a theological discussion if there ever was one. Nobody seems to agree about anything.
johninCR said:
OK, I'll bite, what's "double the D"? Diameter of the driver? Distance to the floor?
I'm in partial agreement with the comments about SL's approach - the Bastani experience illuminated just how good "doing it wrong" can sound. I'm looking forward to finding out where all of this theory fails to apply to the real world - the much simpler experience of designing the Ariel showed how far off the literature about MTM's were, something I didn't expect at the time. For years, I'd read how wonderful MTM's were, and how you could slap together any old crossover and it made them perfect.
Yeah, right. In practice it was fiendishly difficult to align for subjectively flat response - and with extremely flat drivers, too. It took quite a while to dawn on me that I was trying to work with two dissimilar sets of freq resp curves at once (direct first-arrival sound vs total energy into the room, with the first 3 mSec removed). MTM's are actually kind of nasty to work with, with odd midrange colorations that are phase dependent. It took quite a bit of phase-twiddling on the midbass drivers to get the thing to integrate and sound like one driver.
Based on that experience alone, I'm sure that all those hypercomplex graphs and theory are going to fall down - badly - when I start measuring and listening. What's really strange is all the endless wrangling about the ideal polar pattern vs frequency, a theological discussion if there ever was one. Nobody seems to agree about anything.
Hi Lynn.
1 driver FR; 2 <200Hz; 4 <100Hz; room gain <50Hz; for flat efficiency response, though driver efficiencies are often measured at 1kHz.
Maybe the selection of more efficient LF drivers wrt a chosen FR would simplify; with the LF drivers running <100 but having an additional <200 tapering ( eg. R + Zobel ) section at -6dB, like baffle step in reverse.
Wrt baffle edge. What about felted 3" radii backwards, possibly one being sided. No side reflections for cone depth, yet increased baffle size.
Hi Variac,
Did you ever come up with an idea for overcoming the low composite impedance of your four driver line, or was (non-commercial) amplification expected to match.
With similar thoughts of my own I have tried for single amplifier drive, the -6dB reducing of LF power ( C//R ) to a commonly baffled FR driver, this not only to limit its excursion, but to reduce the development of reverse LF pressure drive motion at resonance so that other drivers then lesser affect the FR at higher frequencies.
Cheers ....... Graham.
1 driver FR; 2 <200Hz; 4 <100Hz; room gain <50Hz; for flat efficiency response, though driver efficiencies are often measured at 1kHz.
Maybe the selection of more efficient LF drivers wrt a chosen FR would simplify; with the LF drivers running <100 but having an additional <200 tapering ( eg. R + Zobel ) section at -6dB, like baffle step in reverse.
Wrt baffle edge. What about felted 3" radii backwards, possibly one being sided. No side reflections for cone depth, yet increased baffle size.
Hi Variac,
Did you ever come up with an idea for overcoming the low composite impedance of your four driver line, or was (non-commercial) amplification expected to match.
With similar thoughts of my own I have tried for single amplifier drive, the -6dB reducing of LF power ( C//R ) to a commonly baffled FR driver, this not only to limit its excursion, but to reduce the development of reverse LF pressure drive motion at resonance so that other drivers then lesser affect the FR at higher frequencies.
Cheers ....... Graham.