Member
Joined 2003
Hi Lynn,
Since you are looking hard at the 12NDA520, I was going to take some FR and CSD shots of the smaller 10NDA520 for you this past weekend.
Unfortunately, the spring yard workers were out in force both days so you'd have seen the response of various leaf blowers, lawnmowers, etc Hopefully I can do it next weekend.
Paul
Since you are looking hard at the 12NDA520, I was going to take some FR and CSD shots of the smaller 10NDA520 for you this past weekend.
Unfortunately, the spring yard workers were out in force both days so you'd have seen the response of various leaf blowers, lawnmowers, etc Hopefully I can do it next weekend.
Paul
Hi Lynn,
I think the final word(s) are still out... it all may depend on application and on which priorities one sets. For instance I haven't tried the 15" crossed high in a proper design yet, in practice I still use it up to 300 Hz only, with a midrange, because I have no tweeter capable of going down to 1-1.2k. Such a higher X-O has only been a preliminary investigation. And PaulW seems to still have a soft spot for his ribbons even though the 1" compression driver likely would win on dynamics.
So why are these large drivers so good? I suppose it's a combination of factors. The specific high end pro drivers we discussed here in fact incorporate all the technology of the better audiophile drivers, yet at high efficiency and high power handling. To some extent I also believe it's a matter of "no replacement for displacement" , similar to what the line array people already know... Then, I strongly suspect experienced pro audio designers design with experience from musical intrument application in mind. In other words they might have a good handle on what types of trade offs are more musically acceptable. Although, the distortion measurements of these drivers are also objectively very good.
I'm curious as to Paul's CSD results for the 10" (somehow I haven't succeeded in convincing my software yet do produce a CSD, something is wrong with the gating. or maybe it's me). Maybe here one will see a weak point of the larger drivers.
I think the final word(s) are still out... it all may depend on application and on which priorities one sets. For instance I haven't tried the 15" crossed high in a proper design yet, in practice I still use it up to 300 Hz only, with a midrange, because I have no tweeter capable of going down to 1-1.2k. Such a higher X-O has only been a preliminary investigation. And PaulW seems to still have a soft spot for his ribbons even though the 1" compression driver likely would win on dynamics.
So why are these large drivers so good? I suppose it's a combination of factors. The specific high end pro drivers we discussed here in fact incorporate all the technology of the better audiophile drivers, yet at high efficiency and high power handling. To some extent I also believe it's a matter of "no replacement for displacement" , similar to what the line array people already know... Then, I strongly suspect experienced pro audio designers design with experience from musical intrument application in mind. In other words they might have a good handle on what types of trade offs are more musically acceptable. Although, the distortion measurements of these drivers are also objectively very good.
I'm curious as to Paul's CSD results for the 10" (somehow I haven't succeeded in convincing my software yet do produce a CSD, something is wrong with the gating. or maybe it's me). Maybe here one will see a weak point of the larger drivers.
Well, ScottG, you were right all along. The Azurahorn AH-550 looks like an obvious match for the BMS 4540 and 4552 - assuming there aren't weird conflicts in the throat area of the AH-550.
The 300mm mouth diameter even matches the 18Sound 12NDA520 in size, although in practice I suspect it will actually overhang the front baffle in order to have good time alignment. With a cutoff of 550 Hz, it looks any crossover between 1.4 kHz and 2 kHz would work fine, since both drivers have extensive flat-response regions above and below the crossover point. As mentioned earlier, this "cross well above horn cutoff" is sanctioned by Le Cleac'h himself, who ought to know.
Has anyone tried the BMS 1" compression drivers with the small Azurahorn? Results? Comments?
P.S. If anyone has any comments, feel free to answer here or in that "other" thread.
The 300mm mouth diameter even matches the 18Sound 12NDA520 in size, although in practice I suspect it will actually overhang the front baffle in order to have good time alignment. With a cutoff of 550 Hz, it looks any crossover between 1.4 kHz and 2 kHz would work fine, since both drivers have extensive flat-response regions above and below the crossover point. As mentioned earlier, this "cross well above horn cutoff" is sanctioned by Le Cleac'h himself, who ought to know.
Has anyone tried the BMS 1" compression drivers with the small Azurahorn? Results? Comments?
P.S. If anyone has any comments, feel free to answer here or in that "other" thread.
Lynn Olson said:
Its an infrequent thing.
I'd also bet that you could do the B&O filter design without serious combing problems.. consider using a 12 or 15 inch co-axial model without the compression tweeter and instead replacing with a more standard tweeter "flush" mount, (with baffle), centered in the larger coax driver. Move the mid driver just below 1 kHz for its midpoint (based on its operating passband). That should work. But again, it IS a different design.
Also, I think that the open baffle bipole hypercardoid would work rather well to - Unlike most fullrange drivers, a 12 inch driver typically has a large center motor assembly and does not radiate enough high freq. "penetrating" sound to the rear of the driver that could pass through a typical 12 inch driver's diaphragm (..an obvious exception might be the 12" PHY driver - but that isn't a driver thats really been considered). (..and this is even more different design-wise.)
I honestly think that it all depends on the implementation and what you really want out of the design. Get those goals down (ALL the goals), and I can prob. recommend just about any driver known to man that would have the best chance of accomplishing that.
As to the BMS compression driver:
Generally: These "ring" drivers (once "broken in") are extremely detailed in sound but can be rather "hifi" in sound - i.e. "pin point" imaging but not as 3D'ish. (..and I suspect you want something more 3D, but I could be wrong.) Anyway.. At the bottom of its passband (resonance area), all the drivers will exhibit time domain problems, but in reality (at lest compared to most commercial designs), the BMS drivers decay rather well - and to an extent it is dependent on the horn's design.
From what I've gathered information on - the 4540ND is the best sounding driver of the group (as mentioned by an other that has had access to all but the most recent drivers under production), despite its lower price and its supposedly lesser low-freq. passband.
Now as for the Horns..
The first thing that concerns me is horizontal polar deviation. What *I* really want to see is a polar plot that has no more than 1-2 db of deviation from its on axis response over its intended passband and uniform directive limit (typically expressed as -3db point over a coverage angle.. i.e. 90 degrees). This is something I'd first discuss with the Azurahorn people before purchasing. Of course at its freq. extremes this constant coverage won't hold true, BUT the low freq. portion should have an appropriate filter for that and it isn't as important for the highest freq.s as long as the constant coverage extends for most fundamentals (i.e. you can always add a super tweeter).
Then next thing I want to see is a W I D E dispersion horizontally. At least to me - EVERY moderate to low coverage angle horn I've heard sounds completely artificial (i.e. exceedingly poinpoint, bright, poor soundstage, poor depth, 2D in the worst sense). On the other hand though, I've personally never heard a design that has a uniform coverage angle down through the midrange that was low in coverage (i.e. highly directive) - so who knows, a hypercardoid midrange might well work with such a directive horn?
Also, (at least with most horns) - with fairly steep high pass filters you should have your crosspoint at least half an octave above the horn's cuttoff freq.. Example - The DDS 90 degree waveguide that Paul has specs 900 Hz, so with a LR 4th order I'd want a highpass crosspoint of at LEAST 1350 Hz. Of course lower order filters need to have considerably more bandwidth between its crosspoint and the horns cutoff freq.. Also, there is a lot more to this - looking at the horn and driver freq. response typically shows where the crosspoint is maximally lowest. Additionally, roundover's like the Le Cleac'h based Azurahorn can often extend this freq. a bit lower than the general rules (as above) would imply.
Finally, I want a lower freq. driver that has as close as possible a radiation pattern for at least most of its upper passband that will sum "correctly" to the coverage angle of the horn (+/- a few db) for at LEAST a half octave below the crosspoint, and hopefully that much above the crosspoint as well.
IF you fairly well follow those 4 basic rules - you'll almost certainly get good sound (with other proper design), if perhaps not exactly the sound you are looking for.
In the case of the 18Sound 12NDA520, (and assuming I had a horn coverage angle that was appropriate with a cutoff of around 500 Hz), Looking at its freq. response I'd probably choose about 900 Hz for the crosspoint with a LR 4th order. An LR 2nd order? - about 1200 Hz. Here the LR version allows a bit more "give" to the lower freq. response because its a -6db design, if instead it was a -3db then I'd worry some because the crosspoint would need to be a bit higher in freq., (and particularly with a lower order crossover), would likely cause problems with the 12" driver becoming too directive above 1.4 kHz.
If your contemplating the BMS 4540ND, then you would need to factor in its freq. response. - and THAT would suggest a LR 4th order of about 1.4 kHz with the 18Sound 12NDA520.
IMO though, I would NOT use any of the BMS models. I'd want a lower freq. response that the 450ND and 4552ND just can't provide. Additionally, I'd want something that was a bit more "3D" in sound. Instead I would choose any of the 2 inch exit compression drivers from Radian. With the most expensive 950 probably providing the best sound and allowing for something like a JohnK transient perfect 2nd order around 1.2 kHz.
But again though, thats just another idea!
Oh, BTW - IF you want a "2.5" helper design for the open baffle loss I have several ideas. If you want to keep with the 12" 18Sound drivers AND are willing to use a parallel crossover then look at the costly (but worth it) Zero Ohm inductors by Mundorf. (I have an alternate suggestion for the Tone Tubby.)
It seems we're all on a very similar page here, both in design goals and in ideas to achieve them. Ironically I have friends here who have Azurahorns with Lowthers, and just a few weeks ago I drew a LeCleac'h contour for a 500Hz horn to be produced in small series by a friend here. The main horn will be for 2" drivers, and in fiberglass (see my post #131 for pic for pic). I also drew attachments for 1.4" and 1" drivers one can later have made on a lathe or a CNC, in wood, to extend the horn for the smaller drivers.
My own goals are very similar to ScottG's comments above, I posted this here some time ago as well - ideally let the 15ND930 go up close to 1k +-200 Hz, with a compression driver on top (the 1.4" 18Sound NSD1480 looks very good on paper) and a wide 120 degree coverage to match the 15" in dipole or cardioid mode (see my post#130 for pic). The question is whether the 15" satisfies this high up in the long run, or whether a midrange is necessary. Right now I still have a 6.5" midrange between the 15" and the tweeter because no way I can use the dome down to the 1.2k range in normal listening. I only could do some preliminary testing at low listening levels, which indicated promise.
In any case the 12" would be an easier choice on the upper side of the passband, question is how much added IMD you'll get from added bass stress in dipole operation, compared to the 15". Maybe not much, especially with the AIC model.
My own goals are very similar to ScottG's comments above, I posted this here some time ago as well - ideally let the 15ND930 go up close to 1k +-200 Hz, with a compression driver on top (the 1.4" 18Sound NSD1480 looks very good on paper) and a wide 120 degree coverage to match the 15" in dipole or cardioid mode (see my post#130 for pic). The question is whether the 15" satisfies this high up in the long run, or whether a midrange is necessary. Right now I still have a 6.5" midrange between the 15" and the tweeter because no way I can use the dome down to the 1.2k range in normal listening. I only could do some preliminary testing at low listening levels, which indicated promise.
In any case the 12" would be an easier choice on the upper side of the passband, question is how much added IMD you'll get from added bass stress in dipole operation, compared to the 15". Maybe not much, especially with the AIC model.
ScottG, your info is much appreciated, especially your experience with drivers I know little about, such as prosound anything.
I have to "read between the lines" because my design priorities are somewhat different than yours. My preferences have been formed by speakers I've liked from other designers (that I've heard for myself) and the sonic qualities I've liked and disliked in my own designs.
Constant directivity vs frequency is fairly low on my priority list. I'm the guy that usually crosses over an octave higher than anyone else - the Ariel, for example, with its Scan-Speak tweeter with 1mm excursion, has a measured 4th-order acoustic crossover at 3.8 kHz.
Since driver excursion increases at a rate of 12 dB/oct in direct radiators, even fairly small increases in crossover frequency decreases the "area under the curve" for excusion quite substantially - and this is audible as IM distortion, grain, congestion, and an overall stressed sound. With horns, it seems they fall off the cliff even more severely, with gross horn coloration when pushed too close to the edge.
I guess this is partly because I'm an old-school BBC-style designer, and never believed the data coming out of Canada from the NRC and the popularized data from the HT crowd. Probably more significantly, I've never heard a constant-directivity speaker that I liked, so this design parameter doesn't carry much weight with me.
It sounds like your design experiences are different than mine, and you like different things, which is good! I surmise we hear stereo in somewhat different ways, and have different sets of expectations of what a "good stereo image" sounds like. As an old quadraphonic guy, my expectations are quite different than the direction that the mainstream has taken over the last 20 years.
I'm curious about this 1" versus 2" business. I've heard that small-format CD's are more "strained" and "hifi" sounding, vs the more relaxed sound of the large-format CD's. But I've also heard that 2" CD's get into trouble at high frequencies, and need a supertweeter to make it past that last 15 kHz or so. What's the deal here?
Are small HF horns even available for 2" throat size? I really don't want a 3-foot horn crossed at 500 ~ 800 Hz: that pretty much defeats the whole idea of the widerange dipole in the first place. If I can't find a good-sounding horn/driver that isn't insanely huge, I'll get a high-efficiency ribbon (or maybe the Mundorf AMT) and be done with it.
Since directivity isn't that important to me, my upper limit on the 12" driver is set by the onset of breakup - which for the Tone Tubby and 12NDA520 appears to be around 5 kHz. Depending on sonics, I might not use a lowpass filter at all - but then again, with the Ariel, I ended up tracking the natural rolloff of the Vifa drivers, and giving them a speedup around 4 ~ 5 kHz.
I definitely want to avoid notch filters. I've always had reservations about my speakers that used them - there's a fairly considerable loss of transparency, dynamics, and most serious of all, a flattening of tone color.
Going through your criteria, we're in agreement about having an adequately high crossover for the horn. No argument there; I'm probably further out on that limb than you are. As for frequency vs directivity, well, we can agree to disagree, since I think we're aiming for different goals, especially regardling perception of stereo. I'm pretty far from the mainstream when it comes to stereo, surround sound, and spatial impression.
If the best 1" BMS 1" is more "mechanical" and "hifi" sounding than the best 2" Radian, that makes a difference to me, a big difference. Also very curious about your thoughts on 2.5 designs that overcome the baffle loss - for the 18Sound and Tone Tubby drivers, since I'm still undecided on these things. Something tells me I'll be buying several sets of drivers. Oh well.
I have to "read between the lines" because my design priorities are somewhat different than yours. My preferences have been formed by speakers I've liked from other designers (that I've heard for myself) and the sonic qualities I've liked and disliked in my own designs.
Constant directivity vs frequency is fairly low on my priority list. I'm the guy that usually crosses over an octave higher than anyone else - the Ariel, for example, with its Scan-Speak tweeter with 1mm excursion, has a measured 4th-order acoustic crossover at 3.8 kHz.
Since driver excursion increases at a rate of 12 dB/oct in direct radiators, even fairly small increases in crossover frequency decreases the "area under the curve" for excusion quite substantially - and this is audible as IM distortion, grain, congestion, and an overall stressed sound. With horns, it seems they fall off the cliff even more severely, with gross horn coloration when pushed too close to the edge.
I guess this is partly because I'm an old-school BBC-style designer, and never believed the data coming out of Canada from the NRC and the popularized data from the HT crowd. Probably more significantly, I've never heard a constant-directivity speaker that I liked, so this design parameter doesn't carry much weight with me.
It sounds like your design experiences are different than mine, and you like different things, which is good! I surmise we hear stereo in somewhat different ways, and have different sets of expectations of what a "good stereo image" sounds like. As an old quadraphonic guy, my expectations are quite different than the direction that the mainstream has taken over the last 20 years.
I'm curious about this 1" versus 2" business. I've heard that small-format CD's are more "strained" and "hifi" sounding, vs the more relaxed sound of the large-format CD's. But I've also heard that 2" CD's get into trouble at high frequencies, and need a supertweeter to make it past that last 15 kHz or so. What's the deal here?
Are small HF horns even available for 2" throat size? I really don't want a 3-foot horn crossed at 500 ~ 800 Hz: that pretty much defeats the whole idea of the widerange dipole in the first place. If I can't find a good-sounding horn/driver that isn't insanely huge, I'll get a high-efficiency ribbon (or maybe the Mundorf AMT) and be done with it.
Since directivity isn't that important to me, my upper limit on the 12" driver is set by the onset of breakup - which for the Tone Tubby and 12NDA520 appears to be around 5 kHz. Depending on sonics, I might not use a lowpass filter at all - but then again, with the Ariel, I ended up tracking the natural rolloff of the Vifa drivers, and giving them a speedup around 4 ~ 5 kHz.
I definitely want to avoid notch filters. I've always had reservations about my speakers that used them - there's a fairly considerable loss of transparency, dynamics, and most serious of all, a flattening of tone color.
Going through your criteria, we're in agreement about having an adequately high crossover for the horn. No argument there; I'm probably further out on that limb than you are. As for frequency vs directivity, well, we can agree to disagree, since I think we're aiming for different goals, especially regardling perception of stereo. I'm pretty far from the mainstream when it comes to stereo, surround sound, and spatial impression.
If the best 1" BMS 1" is more "mechanical" and "hifi" sounding than the best 2" Radian, that makes a difference to me, a big difference. Also very curious about your thoughts on 2.5 designs that overcome the baffle loss - for the 18Sound and Tone Tubby drivers, since I'm still undecided on these things. Something tells me I'll be buying several sets of drivers. Oh well.
coaxial horn
hi Scott,
how would you rate the BMS coaxial driver H4590 on 2230 horn?
http://www.lautsprechershop.de/pdf/bms/bms-4590.pdf
"http://www.lautsprechershop.de/pdf/bms/bms-4590.pdf"
It seems to have excellent FR, fairly low distortion up from around 1 kHz and FR at 30 degree goes down only around 10 dB from 1 kHz to 20 kHz in a flat and uniform manner.
Greetings
Michael
hi Scott,
how would you rate the BMS coaxial driver H4590 on 2230 horn?
http://www.lautsprechershop.de/pdf/bms/bms-4590.pdf
"http://www.lautsprechershop.de/pdf/bms/bms-4590.pdf"
It seems to have excellent FR, fairly low distortion up from around 1 kHz and FR at 30 degree goes down only around 10 dB from 1 kHz to 20 kHz in a flat and uniform manner.
Greetings
Michael
CSD
Hi MBK,
what kind of software do you use?
If you can not fix it you might try ARTA which is a no brainer for CSD and all the other loudspeaker measurements.
http://www.fesb.hr/~mateljan/arta/
"http://www.fesb.hr/~mateljan/arta/"
greeings
Michael
Hi MBK,
what kind of software do you use?
If you can not fix it you might try ARTA which is a no brainer for CSD and all the other loudspeaker measurements.
http://www.fesb.hr/~mateljan/arta/
"http://www.fesb.hr/~mateljan/arta/"
greeings
Michael
Member
Joined 2003
Lynn,
You might find pattern control more important in systems with significant directionality. For example, I found the 10NDA520 crossed to the DDS WG sounded "forward" crossed at 1.1k. A check of off-axis response showed the WG losing pattern control just above XO so there was a sharp off-axis response flare in that range. Moving the XO up to 1.5k put the WG in a range where the radiation pattern more closely matched the 520. So, even with the same on-axis response, a significantly different system sound. While "constant" directivity may not be on your list, smooth directivity vs frequency may yield more predictable results.
Agree the small BMS drivers are not an optimal solution below about 1.1k. The 1.4" 18 Sound MBK suggests looks very good if one wanted to go lower...maybe we can motivate MBK to move forward with his WG
Since there seems to be a general shortage of measurements, I volunteer to measure promising horn/WG candidates, on and off-axis, and post results in your thread...I'm curious too.
Paul
You might find pattern control more important in systems with significant directionality. For example, I found the 10NDA520 crossed to the DDS WG sounded "forward" crossed at 1.1k. A check of off-axis response showed the WG losing pattern control just above XO so there was a sharp off-axis response flare in that range. Moving the XO up to 1.5k put the WG in a range where the radiation pattern more closely matched the 520. So, even with the same on-axis response, a significantly different system sound. While "constant" directivity may not be on your list, smooth directivity vs frequency may yield more predictable results.
Agree the small BMS drivers are not an optimal solution below about 1.1k. The 1.4" 18 Sound MBK suggests looks very good if one wanted to go lower...maybe we can motivate MBK to move forward with his WG
Since there seems to be a general shortage of measurements, I volunteer to measure promising horn/WG candidates, on and off-axis, and post results in your thread...I'm curious too
. Paul
Awrite, then. I suppose I have to go ahead at some point... I'm just afraid my ignorance in horn design might make me waste other people's time (the ones with the tools).
I fiddled a bit with the design, made it into an insert for a flat baffle, with a recess in the back to accomodate a disk shaped adapter to bolt the driver on (with this shallow horn, there is no space for a flange and so any mounting bolt would have to go through to the front side of the horn, so I made space for a backplate disk that the driver attaches to, which can then be screwed to the backside of the horn/WG). Model attached...
Data still the same: 1.4" throat for compression driver or 1" dome+surround, WG has OS throat section for 120 degrees nominal coverage, merging into LeCleac'h flare with nominal 380Hz cutoff. Diameter ca. 14", depth ca. 3", expected to keep pattern control at least down to 1kHz (800 Hz hoped-for). One shall see if these predictions beat astrologers and crystal balls...
I fiddled a bit with the design, made it into an insert for a flat baffle, with a recess in the back to accomodate a disk shaped adapter to bolt the driver on (with this shallow horn, there is no space for a flange and so any mounting bolt would have to go through to the front side of the horn, so I made space for a backplate disk that the driver attaches to, which can then be screwed to the backside of the horn/WG). Model attached...
Data still the same: 1.4" throat for compression driver or 1" dome+surround, WG has OS throat section for 120 degrees nominal coverage, merging into LeCleac'h flare with nominal 380Hz cutoff. Diameter ca. 14", depth ca. 3", expected to keep pattern control at least down to 1kHz (800 Hz hoped-for). One shall see if these predictions beat astrologers and crystal balls...
Attachments
The OS profile turns into a conical horn very quickly (read: straight line profile). The deviation from "straight" is then in the fractions of a millimeter. From then on all that's left to do with it is to terminate it somehow, into a flat baffle, or a complete roundover. One could choose a simple large radius, and many do just that. For this design I chose to merge the contour to a LeCleac'h profile of a size such that angle and diameter would exactly line up with the near-conical section of the OS WG, because the LeCleac'h, just as the OS WG profile, claim that the wavefront remains perpendicular to the horn walls at all times. Since it's physics it's all approximations of a complicated reality though (the physicists will wiggle in horror, but then again, I'll say, Lorenz, turbulence, chaos, I rest my case).
(the physicists will wiggle in horror, but then again, I'll say, Lorenz, turbulence, chaos, I rest my case).Lynn, I bet we hear VERY much the same. And while I like different designs as an exercise, I wouldn't be at all surprised if we like very similar attributes in a loudspeaker. (..again, I personally use a fullrange low mass driver (lower passband limited) with a pair of dipole midbasses and a supertweeter.)
The BBC school of design is actually quite in "keeping" with most of what I was suggesting, as was the Ariel.
Strange? But consider that both designs are wide dispersion at all freq.s but the top most octave. Figure 4 shows the horizontal off-axis response of a BBC monitor design:
http://stereophile.com/standloudspeakers/1293harbeth/index3.html
Its not a constant coverage design.. BUT it is a fairly wide dispersion design, AND there isn't a substantial loss of spl's off axis near the crossover (i.e. the horizontal response is reasonably uniform). Nor is the design a Horn-based one.
OK then.. why the suggestion of constant coverage for a Horn?
The perception of freq. balance and discontinuities in sp-levels (particularly near the crossover), as well as maintaining sp-levels throughout most fundamentals (specifically in the upper octave response) to "stabilize" imaging. (..not insignificantly, it also allows for a larger compression driver which in many circumstances can provide better sound.)
The first problem - freq. balance:
Paul's most recent post starts showing the subjective problems with the first problem (..and I believe thats with a LR 4th order slope and a fairly wide dispersion design, both of which can mitigate the problem).
Disregarding issues of hearing horn mouth problems, what happens is that the apparent sp-level of the horn/compression driver sounds significantly elevated when compared to the partnering direct radiator driver. The more directive the horn is - the worse the problem. At BEST it gives a forward sound with a reduced soundstage and compressed imaging. At WORST it becomes ear-bleedingly "bright" or "sharp", provides virtually no soundstage and no depth to images (..with nothing but the horizontal separation apparent - i.e. classic "pong" stereo).
Now you can, (to an extent) "get around" this problem IF you keep that highly directive tweeter out of the range of fundamentals. Alternativly, you can increase the the in-room freq. balance with either a bipole or dipole operation. I believe Bastani's do both - a high crossover freq. for the compression driver and an open back dipole radiation. Still, its suboptimal - precisely because it asks far to much from the 12 inch fullrange driver (..which I'm betting sounds a LOT like a planar design thats point-source rather than line-source sounding.)
To add to this complexity - there are horns/waveguides that are wide dispersion designs near the bottom of their passband, but are NOT wide dispersion as freq.s increase (..i.e. they become increasingly directive). The waveguide that Paul uses is a minor varient of this. Strangely this can compound the (sp-elevated) problem IF a steep crossover is used AND the partnering driver is not of a similar dispersion pattern near the crossover. Even if well designed, the user virtually always must listen off-axis, otherwise the sound is to "bright". (..it not a matter of "do I want to or not" as it sometimes is for directive direct radiators, but rather "I MUST" listen at least some off-axis.)
Here is an example of a poorly designed loudspeaker with this problem (note figure 5):
http://stereophile.com/floorloudspeakers/951/index5.html
I'd bet that MOST of the bright character Fremer describes is NOT attributed to the elevated response, but rather IS attributed to the dispersion problem from waveguide to driver at 1.9 kHz and its difference from off-axis responses above and below this wide dispersion.
Second problem - image quality:
Lets say you have a *good* design. The design is wide in dispersion up to about 3-4 kHz, yet well away from the horn's cut-off freq.. The coverage angle/dispersion is a smooth transition from direct radiator to horn. It IS a little "forward" sounding because of its increasingly directive nature at higher freq.s, but it isn't something that would be deemed as universally objectionable.
Image location in such a design is usually quite precise, often described as "pin-point". Soundstaging CAN be wide (..if not particularly deep), IF you have the loudspeakers "toed-out". In fact with this design (and "toe-out"), imaging can be placed (recording dependent) "outside" of the loudspeaker's boundaries. Again though, field of depth is often compromised.
Now such a design probably uses a smaller diameter compression driver. To an extent this allows for less directivity as freq.s increase. There are however "prices" to be paid here.
Smaller compression drivers tend to sound more "compressed" than larger drivers at lower freq.s. This limits the ability of the loudspeaker to reproduce a 3D image (..or what reviewers typically refer to as "palpable presence"). IMO the suspension just isn't compliant enough with these smaller designs (even after "break in"). Sure, it dampens resonances for clean time domain behavior, but at the same time it also introduces signal loss. The same can be said for ring radiators like the BMS drivers.
IMO the "best" of the breed with regard to reproducing a 3D sound is:
1. a larger compression driver (typically 2 inch format)
2. a compliant suspension (relative to a compression driver anyway) after "break in" (..usually with a mylar surround).
3. specifically using high quality aluminum with its very low loss material level (ESPECIALLY for a given profile), but with a moderately high ability to react to change. (Note Titanium is fairly similar to Aluminum, slightly more loss but also with slightly more ability to change - HOWEVER the profiles that are often used with this material are substantially more "lossy" than they otherwise could be - as such, I've never heard a titanium compression driver that sounded good.)
..to me then, Radian is a "no-brainer" ..once the driver has been "broken in" and is used properly.
So getting back to "constant" coverage..
The problem then is that horns with larger diameter drivers have a more difficult time reproducing higher freq.s off-axis (..as indeed almost any driver does). This means that while even a relatively good design with an increasingly directive upper freq. response with a 1 inch driver - starts to become a poor design with a 2 inch driver.
A good constant coverage horn can trade a bit of low freq. wide dispersion to obtain higher freq. wider dispersion. With a limited vertical dispersion pattern (which can be good), it can often become fairly "constant" for most of its bandwidth, and HOPEFULLY most fundamentals. If the response suffers from a loss of "air" or dispersion at the highest freq.s.. well, then thats what a good super tweeter is for. So thats the "deal here"!
So again, while directivity might not seem important - it IS important, especially, when coupling a horn/compression driver to a direct radiator midbass. Moreover for any given horn-to-direct radiator based design there is a moderately precise location for a particular crossover. Its not like saying, I'd like it placed higher in freq. (..or lower). (..a 1st order crossover combined with a 2" compression driver, a low cut-off freq. horn, AND a very narrow vertical exit can be an exception.)
Then there is the subjective bit where we may well have different likes and dislikes..
Runing a 12 inch driver up that high in freq. does give a definite sound. As I mentioned before, the sound (to me) is rather like a point-source planar. Sure, it sounds good.. but thats not the question. What is the question is:
Will a "full range" 12" driver based design (..assuming you could get a properly functioning high freq. filler driver), sound better for you than a REALLY good horn-to-direct radiator sound?
THAT's a tough question - in that I doubt you have a suitable reference for comparison for the REALLY good horn combo (..played back on a system that you consider reference quality).
Quickest *good* answer would be to hop a plane over to Paris and ask Jean-Michel if you could listen to his system. Its a stretch.. but try getting what you can from the subjective comments toward the end of the page here:
http://www.arduman.com/aa/Sayfalar/lecleach/lecleach.htm
IMO what would suffer the most would be *ultimate* depth when compared to a "fullrange" 12" design. What you would gain would be clarity and precision (..the latter depending on how close you listen to speakers).
As to size..
Yes, its going to be big AND be even more restrictive on crossover freq.. (heck, you can read the dimensions for the 500 Hz Azurahorn. )
So if this isn't for you then stop now and look for other alternatives.. (and I can think of quite a few there as well).
And while I like different designs as an exercise, I wouldn't be at all surprised if we like very similar attributes in a loudspeaker. (..again, I personally use a fullrange low mass driver (lower passband limited) with a pair of dipole midbasses and a supertweeter.)The BBC school of design is actually quite in "keeping" with most of what I was suggesting, as was the Ariel.
Strange? But consider that both designs are wide dispersion at all freq.s but the top most octave. Figure 4 shows the horizontal off-axis response of a BBC monitor design:
http://stereophile.com/standloudspeakers/1293harbeth/index3.html
Its not a constant coverage design.. BUT it is a fairly wide dispersion design, AND there isn't a substantial loss of spl's off axis near the crossover (i.e. the horizontal response is reasonably uniform). Nor is the design a Horn-based one.
OK then.. why the suggestion of constant coverage for a Horn?
The perception of freq. balance and discontinuities in sp-levels (particularly near the crossover), as well as maintaining sp-levels throughout most fundamentals (specifically in the upper octave response) to "stabilize" imaging. (..not insignificantly, it also allows for a larger compression driver which in many circumstances can provide better sound.)
The first problem - freq. balance:
Paul's most recent post starts showing the subjective problems with the first problem (..and I believe thats with a LR 4th order slope and a fairly wide dispersion design, both of which can mitigate the problem).
Disregarding issues of hearing horn mouth problems, what happens is that the apparent sp-level of the horn/compression driver sounds significantly elevated when compared to the partnering direct radiator driver. The more directive the horn is - the worse the problem. At BEST it gives a forward sound with a reduced soundstage and compressed imaging. At WORST it becomes ear-bleedingly "bright" or "sharp", provides virtually no soundstage and no depth to images (..with nothing but the horizontal separation apparent - i.e. classic "pong" stereo).
Now you can, (to an extent) "get around" this problem IF you keep that highly directive tweeter out of the range of fundamentals. Alternativly, you can increase the the in-room freq. balance with either a bipole or dipole operation. I believe Bastani's do both - a high crossover freq. for the compression driver and an open back dipole radiation. Still, its suboptimal - precisely because it asks far to much from the 12 inch fullrange driver (..which I'm betting sounds a LOT like a planar design thats point-source rather than line-source sounding.)
To add to this complexity - there are horns/waveguides that are wide dispersion designs near the bottom of their passband, but are NOT wide dispersion as freq.s increase (..i.e. they become increasingly directive). The waveguide that Paul uses is a minor varient of this. Strangely this can compound the (sp-elevated) problem IF a steep crossover is used AND the partnering driver is not of a similar dispersion pattern near the crossover. Even if well designed, the user virtually always must listen off-axis, otherwise the sound is to "bright". (..it not a matter of "do I want to or not" as it sometimes is for directive direct radiators, but rather "I MUST" listen at least some off-axis.)
Here is an example of a poorly designed loudspeaker with this problem (note figure 5):
http://stereophile.com/floorloudspeakers/951/index5.html
I'd bet that MOST of the bright character Fremer describes is NOT attributed to the elevated response, but rather IS attributed to the dispersion problem from waveguide to driver at 1.9 kHz and its difference from off-axis responses above and below this wide dispersion.
Second problem - image quality:
Lets say you have a *good* design. The design is wide in dispersion up to about 3-4 kHz, yet well away from the horn's cut-off freq.. The coverage angle/dispersion is a smooth transition from direct radiator to horn. It IS a little "forward" sounding because of its increasingly directive nature at higher freq.s, but it isn't something that would be deemed as universally objectionable.
Image location in such a design is usually quite precise, often described as "pin-point". Soundstaging CAN be wide (..if not particularly deep), IF you have the loudspeakers "toed-out". In fact with this design (and "toe-out"), imaging can be placed (recording dependent) "outside" of the loudspeaker's boundaries. Again though, field of depth is often compromised.
Now such a design probably uses a smaller diameter compression driver. To an extent this allows for less directivity as freq.s increase. There are however "prices" to be paid here.
Smaller compression drivers tend to sound more "compressed" than larger drivers at lower freq.s. This limits the ability of the loudspeaker to reproduce a 3D image (..or what reviewers typically refer to as "palpable presence"). IMO the suspension just isn't compliant enough with these smaller designs (even after "break in"). Sure, it dampens resonances for clean time domain behavior, but at the same time it also introduces signal loss. The same can be said for ring radiators like the BMS drivers.
IMO the "best" of the breed with regard to reproducing a 3D sound is:
1. a larger compression driver (typically 2 inch format)
2. a compliant suspension (relative to a compression driver anyway) after "break in" (..usually with a mylar surround).
3. specifically using high quality aluminum with its very low loss material level (ESPECIALLY for a given profile), but with a moderately high ability to react to change. (Note Titanium is fairly similar to Aluminum, slightly more loss but also with slightly more ability to change - HOWEVER the profiles that are often used with this material are substantially more "lossy" than they otherwise could be - as such, I've never heard a titanium compression driver that sounded good.)
..to me then, Radian is a "no-brainer" ..once the driver has been "broken in" and is used properly.
So getting back to "constant" coverage..
The problem then is that horns with larger diameter drivers have a more difficult time reproducing higher freq.s off-axis (..as indeed almost any driver does). This means that while even a relatively good design with an increasingly directive upper freq. response with a 1 inch driver - starts to become a poor design with a 2 inch driver.
A good constant coverage horn can trade a bit of low freq. wide dispersion to obtain higher freq. wider dispersion. With a limited vertical dispersion pattern (which can be good), it can often become fairly "constant" for most of its bandwidth, and HOPEFULLY most fundamentals. If the response suffers from a loss of "air" or dispersion at the highest freq.s.. well, then thats what a good super tweeter is for. So thats the "deal here"!
So again, while directivity might not seem important - it IS important, especially, when coupling a horn/compression driver to a direct radiator midbass. Moreover for any given horn-to-direct radiator based design there is a moderately precise location for a particular crossover. Its not like saying, I'd like it placed higher in freq. (..or lower). (..a 1st order crossover combined with a 2" compression driver, a low cut-off freq. horn, AND a very narrow vertical exit can be an exception.)
Then there is the subjective bit where we may well have different likes and dislikes..
Runing a 12 inch driver up that high in freq. does give a definite sound. As I mentioned before, the sound (to me) is rather like a point-source planar. Sure, it sounds good.. but thats not the question. What is the question is:
Will a "full range" 12" driver based design (..assuming you could get a properly functioning high freq. filler driver), sound better for you than a REALLY good horn-to-direct radiator sound?
THAT's a tough question - in that I doubt you have a suitable reference for comparison for the REALLY good horn combo (..played back on a system that you consider reference quality).
Quickest *good* answer would be to hop a plane over to Paris and ask Jean-Michel if you could listen to his system. Its a stretch.. but try getting what you can from the subjective comments toward the end of the page here:
http://www.arduman.com/aa/Sayfalar/lecleach/lecleach.htm
IMO what would suffer the most would be *ultimate* depth when compared to a "fullrange" 12" design. What you would gain would be clarity and precision (..the latter depending on how close you listen to speakers).
As to size..
Yes, its going to be big AND be even more restrictive on crossover freq.. (heck, you can read the dimensions for the 500 Hz Azurahorn.
)So if this isn't for you then stop now and look for other alternatives.. (and I can think of quite a few there as well).
Hallo Michael,
have Arta too (demo/original sub- 1.0 version) , just didn't think of it
.
Usually I use Audiotester, it does almost everything and has nice data saving and curve operations, that make comparisons a lot easier than on Arta (I hear thar Arta is being improved in this respect though).
Audiotester is also maintained a lot but still, occasional problems remain. I think I have a delay problem, maybe also related to my M-Audio Pre with USB1.1 that I use. Signal propagation time is not constant from measurement to measurement and I suspect it just messes up the triggering/timing. So phase and decay measurements are a shot in the dark, but again it may be the M-Audio that's to blame.
have Arta too (demo/original sub- 1.0 version) , just didn't think of it
. Usually I use Audiotester, it does almost everything and has nice data saving and curve operations, that make comparisons a lot easier than on Arta (I hear thar Arta is being improved in this respect though).
Audiotester is also maintained a lot but still, occasional problems remain. I think I have a delay problem, maybe also related to my M-Audio Pre with USB1.1 that I use. Signal propagation time is not constant from measurement to measurement and I suspect it just messes up the triggering/timing. So phase and decay measurements are a shot in the dark, but again it may be the M-Audio that's to blame.
I have to reluctanctly concede the best horn HF I've heard came from 2" aluminum-diaphragm CD's. The two big Altecs (probably A5's) at the San Francisco meet I attended some years ago used theater-size multicell horns and had much more vivid and natural tone colors, along with a lot less A7-type squawk and harshness, than typical 1"-driver horns. Point taken. The 1-inchers sound like they're working hard, and the 2-inchers don't. More importantly, the 2-inchers were a lot more musical.
I visited the Radian site and the 850-PB compression driver seems to be the best one there, with smoother response than the 950-PB neodymium alternative. They do mention the 950-PB has lower distortion, though - choices, choices. Any thoughts on this?
I note that Radian recommends a 1.2 kHz crossover at 12 dB/octave. This begs the question - which and what size horn? I see Azura makes two reasonably obvious choices: the AH-340 and AH-550, the 340 having a diameter of 600mm while the 550 has a diameter of 300mm. What exactly does the larger horn with a lower cutoff accomplish - less HOM's and polar-pattern variation since the Radian compression driver is coming in at 1.2 kHz, and the horn cutoff is thus further away?
To maximize vividness of tone color, as you mention in the other forum, the 12" Alnico Tone Tubby is a good choice - the "plateau" region is not that important since the crossover is going to knock it out anyway. The new 15" Tone Tubby is a candidate for floor-mounting and the 1/f compensation driver.
I visited the Radian site and the 850-PB compression driver seems to be the best one there, with smoother response than the 950-PB neodymium alternative. They do mention the 950-PB has lower distortion, though - choices, choices. Any thoughts on this?
I note that Radian recommends a 1.2 kHz crossover at 12 dB/octave. This begs the question - which and what size horn? I see Azura makes two reasonably obvious choices: the AH-340 and AH-550, the 340 having a diameter of 600mm while the 550 has a diameter of 300mm. What exactly does the larger horn with a lower cutoff accomplish - less HOM's and polar-pattern variation since the Radian compression driver is coming in at 1.2 kHz, and the horn cutoff is thus further away?
To maximize vividness of tone color, as you mention in the other forum, the 12" Alnico Tone Tubby is a good choice - the "plateau" region is not that important since the crossover is going to knock it out anyway. The new 15" Tone Tubby is a candidate for floor-mounting and the 1/f compensation driver.
..and those multicells are FAR more flawed by comparison (..excellent drivers though).
Ah, into the weird world of driver spec.s! Its not just the impedance that can be misleading.
Here the problem is that the 1.2 kHz 2nd order is in part based on the horn they measure with it. The same is true for the freq. response as well. Unfortunately I can give you no better answer than that it is likely the more expensive unit sounds AND measures better with a better horn (and filter depending of the type of horn). (..note that the same holds true for TAD as well - the 2001 vs the 2002.) On the other hand I seem to remember someone mentioning that there is an .."audiophool" (..ehm... cough..) ENTHUSIAST working at Radian that would likely give you an unbiased response - so you might try contacting them to see if such an individual exists and could give you more information. (..after all, why spend more for less if thats the case?)
The end result is that larger horn buys you a lower crossover point and increased clarity as a result of the extended passband for the compression driver. As a result it also increases the number of drivers likely to work well (..at least technically) with a typical horn, because it gives a bit more freedom for using a 15" driver.
On the other hand though, you have heard the cr@p that people are using for drivers.
Geddes may have an excellent driver for low freq. extension, the correct polar response for the crossover, and tons of power handling - but "delicacy"/"finesse"/"nuance"? No, that 15" BMS driver was made for a "stage sub" for a reason, and it certainly didn't have anything to to with any of the above descriptors.
To go farther you have to think of low mass for a given sd. Both 12" drivers you are looking at have that (..and actually extend into what I term as the "exotic" range of drivers).
IMO, IF you get the right midrange driver and the right crossover in conjunction with an excellent horn & compression driver - then the "need" for a lower freq. passband for the compression driver is moot, UNLESS you are striving for VERY HIGH spl's (averaging over 105 db).
In addition to this however, is also the question of the driver's problems at resonance. Though I'm not sure, I suspect that the Radian's resonance is not nearly as clean as the BMS, and so a crosspoint of 1.2 kHz is more than an octave away and will effectively be inaudible with a good 2nd order driver (..in that there will be "masking" by the midbass driver).
The short answer then is:
Option 1: If you want to push the crossover from 1.2 down to a limit of 900 Hz,(probably more like 960 Hz), with a 2nd order electrical - then you would spec. the larger horn. (Actually, without regard for the resonance of the driver, the Le Cleac'h roundover exit profile should be able to go quit a bit lower than the mid 900's.)
Option 2: If you are OK with a 2nd order from 1.2 to 1.3, AND want the benefit of a more extended off-axis response at higher freq.s, then go with the smaller horn.
Pair it with either of those 12" drivers and I'd pick option 2 every time.
Of course I'd still opt for a CD design if possible.
EDIT: I suspect the 15" tone tubby would work very well for your open baffle compensation.
Ah, into the weird world of driver spec.s! Its not just the impedance that can be misleading.
Here the problem is that the 1.2 kHz 2nd order is in part based on the horn they measure with it. The same is true for the freq. response as well. Unfortunately I can give you no better answer than that it is likely the more expensive unit sounds AND measures better with a better horn (and filter depending of the type of horn). (..note that the same holds true for TAD as well - the 2001 vs the 2002.) On the other hand I seem to remember someone mentioning that there is an .."audiophool" (..ehm... cough..) ENTHUSIAST working at Radian that would likely give you an unbiased response - so you might try contacting them to see if such an individual exists and could give you more information. (..after all, why spend more for less if thats the case?)
The end result is that larger horn buys you a lower crossover point and increased clarity as a result of the extended passband for the compression driver. As a result it also increases the number of drivers likely to work well (..at least technically) with a typical horn, because it gives a bit more freedom for using a 15" driver.
On the other hand though, you have heard the cr@p that people are using for drivers.
Geddes may have an excellent driver for low freq. extension, the correct polar response for the crossover, and tons of power handling - but "delicacy"/"finesse"/"nuance"? No, that 15" BMS driver was made for a "stage sub" for a reason, and it certainly didn't have anything to to with any of the above descriptors.
To go farther you have to think of low mass for a given sd. Both 12" drivers you are looking at have that (..and actually extend into what I term as the "exotic" range of drivers).
IMO, IF you get the right midrange driver and the right crossover in conjunction with an excellent horn & compression driver - then the "need" for a lower freq. passband for the compression driver is moot, UNLESS you are striving for VERY HIGH spl's (averaging over 105 db).
In addition to this however, is also the question of the driver's problems at resonance. Though I'm not sure, I suspect that the Radian's resonance is not nearly as clean as the BMS, and so a crosspoint of 1.2 kHz is more than an octave away and will effectively be inaudible with a good 2nd order driver (..in that there will be "masking" by the midbass driver).
The short answer then is:
Option 1: If you want to push the crossover from 1.2 down to a limit of 900 Hz,(probably more like 960 Hz), with a 2nd order electrical - then you would spec. the larger horn. (Actually, without regard for the resonance of the driver, the Le Cleac'h roundover exit profile should be able to go quit a bit lower than the mid 900's.)
Option 2: If you are OK with a 2nd order from 1.2 to 1.3, AND want the benefit of a more extended off-axis response at higher freq.s, then go with the smaller horn.
Pair it with either of those 12" drivers and I'd pick option 2 every time.
Of course I'd still opt for a CD design if possible.
EDIT: I suspect the 15" tone tubby would work very well for your open baffle compensation.
CSD / OT
Hi
MBK, I also like and use AudioTester - its really good, easy to use, packed with features, not pricy and well maintained.
http://www.audiotester.de
"http://www.audiotester.de"
but as for CSD I didn't manage to come around with it either (I have different external soundcards too choose from) and so for CSD measuremants ARTA is the better choice for me.
By the way for those who are interested to perform stored energy measurements in the way like Siegfried Linkwitz does, I asked Ulrich Müller to implement a stimulus alike some time ago. As far as I can see, dipole and open buffle discussions are a lot connected to "philosophical" aspects of stored energy.
These dayes he finished his work and came up with AudioTester version 2.2b / build2. The signal can now be choosen under "Dual Sinus" with "Multiply" checked.
In the HELP file I also saw that stimuli can be stored to files, which is interesting when you would like to create CD's for testing.
I din't have time to check it out in detail as I am currently don't have access to my equippment.
Ivo Mateljan told me that he will come up with the next version of ARTA in June...
Both, Ulrich Müller and Ivo Mateljan are very responsive to feature requests and definitly like to get some good and precise feedback about their software.
Greetings
Michael
Hi
MBK, I also like and use AudioTester - its really good, easy to use, packed with features, not pricy and well maintained.
http://www.audiotester.de
"http://www.audiotester.de"
but as for CSD I didn't manage to come around with it either (I have different external soundcards too choose from) and so for CSD measuremants ARTA is the better choice for me.
By the way for those who are interested to perform stored energy measurements in the way like Siegfried Linkwitz does, I asked Ulrich Müller to implement a stimulus alike some time ago. As far as I can see, dipole and open buffle discussions are a lot connected to "philosophical" aspects of stored energy.
These dayes he finished his work and came up with AudioTester version 2.2b / build2. The signal can now be choosen under "Dual Sinus" with "Multiply" checked.
In the HELP file I also saw that stimuli can be stored to files, which is interesting when you would like to create CD's for testing.
I din't have time to check it out in detail as I am currently don't have access to my equippment.
Ivo Mateljan told me that he will come up with the next version of ARTA in June...
Both, Ulrich Müller and Ivo Mateljan are very responsive to feature requests and definitly like to get some good and precise feedback about their software.
Greetings
Michael
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