The SB29Be measures better and it is easier to work with. Requires only very gentle EQ. It also sounds better than the radian tweeter strictly speaking. More holographic and also more analytical.
All of that is offset by the considerable broad advantages of a coax driver, which has a superior radiation pattern and if done well the xover is absolutely seamless. Blends with the 8” mid, No lobing patterns and true Constant Directivity in both vertical and horizontal planes. The Radian 8” coax Be is very transparent and after DSP correction measures great.
The Radian aluminum sounds very good. Most people will be extremely happy with it. The beryllium is still definitely better.
Horns in general are a more advanced game. It takes more skill to tame them and make them sound right. Personally I feel the coax approach wins in the end but if you’re into holographic ultra high def top end, you may prefer the SB.
All of that is offset by the considerable broad advantages of a coax driver, which has a superior radiation pattern and if done well the xover is absolutely seamless. Blends with the 8” mid, No lobing patterns and true Constant Directivity in both vertical and horizontal planes. The Radian 8” coax Be is very transparent and after DSP correction measures great.
The Radian aluminum sounds very good. Most people will be extremely happy with it. The beryllium is still definitely better.
Horns in general are a more advanced game. It takes more skill to tame them and make them sound right. Personally I feel the coax approach wins in the end but if you’re into holographic ultra high def top end, you may prefer the SB.
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Thanks, those are helpful descriptions! I'm intrigued by the Constant Directivity aspect and have never been into analytical-leaning tweeters. The fact that with the Radian you can get going with the Al and upgrade later to Be is pretty life-accommodating, too.
Sticking with tweeters if you don't mind, what are the differences between having a tweeter that's also open to the back (e.g. GR Research Neo 3) and a closed tweeter paired with a back-firing tweeter?
Sticking with tweeters if you don't mind, what are the differences between having a tweeter that's also open to the back (e.g. GR Research Neo 3) and a closed tweeter paired with a back-firing tweeter?
Open back tweeters are great to the extent that you can find one. The advantage of doubling up on closed back tweeters is:
There are hundreds to choose from instead of just a handful
You can get horn loading on both sides, which is impossible on any commercially available dipole tweeter that I am aware of
And you can adjust the SPL on each side as you wish with Lpads or crossover components, or even separate amplifiers, if you like
There are hundreds to choose from instead of just a handful
You can get horn loading on both sides, which is impossible on any commercially available dipole tweeter that I am aware of
And you can adjust the SPL on each side as you wish with Lpads or crossover components, or even separate amplifiers, if you like
Also none of the open back tweeters are Constant Directivity which IMHO is a major drawback.
Those are really helpful distinctions. I'm sure those points aren't relevant to everyone, but for me personally I'm intrigued to explore the Constant Directivity approach since I do quite a bit of casual listening at significantly oblique angles (e.g., listening music while eating dinner at the table that's well off to the side). I've also never been a fan of the notion that only one person get's the small sweet spot.
What are the ramifications of the comment about having horn loading on both sides? Could you explain more what that means (vs non-horn loading)? I probably don't understand horn loading period, to be honest. I do have to say that the conversations around these coaxial horns are deeply interesting since what I heard in the early 90's turned me off to the extent that I've avoided horns ever since, undoubtedly unfairly. Excited to learn more.
What are the ramifications of the comment about having horn loading on both sides? Could you explain more what that means (vs non-horn loading)? I probably don't understand horn loading period, to be honest. I do have to say that the conversations around these coaxial horns are deeply interesting since what I heard in the early 90's turned me off to the extent that I've avoided horns ever since, undoubtedly unfairly. Excited to learn more.
I used to hate horns. I remember going to a Klipsch dealer when I was 17 and the guy played the Klipschorns for me.
I thought the dynamics sounded impressive but strangely exaggerated. I saw a DBX Dynamic Range Expander and I bet you any amount of money he didn't think I would know what it was, but I did. I walked across the room and pressed the bypass button and now I knew I was listening to a fair demonstration.
He was playing "Money for nothing" by Dire Straits and the upper bass was thick and congested, the midrange was ragged and the highs were spitty. So while I appreciated the fact they had 104dB sensitivity and "great dynamics" and all that, I still thought they sounded horrible. I would have greatly preferred a KEF 105.
Fast forward to 4 years ago I built a simple set of dipoles using Faital 12HX230s and (setting aside the Open Baffle characteristics like soundstage) not only would they compete 100% with a classic British audiophile speaker in terms of accuracy, I was amazed at the "aliveness" that seemed to come from the high efficiency and lack of compression. It was the closest I'd ever heard to a drum set sounding like real drums.
The only reason I got "British audiophile speaker" accuracy was because I fixed a bunch of problems with DSP. It would be VERY hard to pull it off with passive xovers. But the Faitals are much better designed than anything Klipsch was doing in the 1980s and the problems (horn throat reflections and the like) are redeemable.
What does a horn do? Think of it like a 10 speed bike. Direct radiators are like a bike that can ONLY pedal in first gear. In 1st gear, if you want to ride fast down a hill, your feet have to be cranking furiously and you almost fall off from the commotion. In 10th gear your bike can be going extremely fast but you are still pedaling slowly and using force instead of fast foot motion to propel yourself. That's what a horn does for a speaker.
A direct radiator speaker expends 99% of its energy pushing the cone back and forth and only 1% of that energy gets transmitted to the air. The air is too "thin." If we lived on a planet where the normal air pressure was 100 bars instead of 1 bar it would be a different story. You wouldn't need horns and a 6.5" woofer would naturally have an SPL of 110dB 1 watt.
Since our atmosphere is thin, a horn is an acoustic "gear" that matches the small surface area of the driver (throat) to a much larger surface area of the room (mouth). So the driver feeding the horn is moving microscopic distances (large Xmax NOT required) and still moving tons of air. The voice coil is "pushing hard" with minimal stroke length, just like a 10 speed bike in 10th gear.
This translates to what subjectively sounds like "speed" and "immediacy" and "slam" and "authority" and "effortlessness" and "dynamics" and "dynamic range to burn."
When I was 17 I used to obsess about low mass drivers, tweeters with only 0.2g moving mass because I thought that would give you "fast transient response" and that certainly makes sense if you only think of a driver as a linear device that is supposed to move back and forth. = "lumped parameter model." But that is not an accurate way to think of it. A driver is really an impedance matching device (= a gear) connecting the electromagnetic force to surrounding air. And besides, when you do the math, the mass cancels out anyway and mass determines the efficiency of the driver, not the bandwidth.
So if a direct radiator is 0.5 to 1% efficient and a horn is 5-30% efficient, it means energy is being harnessed to moving air much more effectively and you can indirectly hear that. All things being equal, a more efficient speaker always sounds better for some reason, and that's the reason.
For most horn tweeters, below something like 10KHz, most of the force of the voice coil is expended in moving air, and not sloshing the mass of the diaphragm back and forth. At some high frequency the mass starts to predominate and this is why horns have a downward sloping curve which has to be corrected.
Well it also turns out that if you choose the right horn expansion profile you get Constant Directivity, which basically looks like this:
This of course is the Bitches Brew polar heat map, and everything above 1100Hz is the radiation pattern of the Constant Directivity horn formed by the aperture and the cone.
It turns out that Constant Directivity profile is a huge advantage for stereo imaging because as you move off axis, the level drops evenly and tilts slightly down so if you toe the speakers in, every seat in the house is great. Compare this to a more typical plot that I grabbed off the internet:
...where the polar pattern is wide at low frequencies and narrow at high frequencies.
So going to your original question about dipole tweeters, all the ones I know of are direct radiators with polar patterns like the one immediately above, and not like CD horns.
I can imagine having a coax with a horn on both sides. It might be kind of ridiculous but worth it for someone who wants to try. (It would have many difficulties which I don't care to get into.)
So that's why I put CD horns on both sides of my designs.
I thought the dynamics sounded impressive but strangely exaggerated. I saw a DBX Dynamic Range Expander and I bet you any amount of money he didn't think I would know what it was, but I did. I walked across the room and pressed the bypass button and now I knew I was listening to a fair demonstration.
He was playing "Money for nothing" by Dire Straits and the upper bass was thick and congested, the midrange was ragged and the highs were spitty. So while I appreciated the fact they had 104dB sensitivity and "great dynamics" and all that, I still thought they sounded horrible. I would have greatly preferred a KEF 105.
Fast forward to 4 years ago I built a simple set of dipoles using Faital 12HX230s and (setting aside the Open Baffle characteristics like soundstage) not only would they compete 100% with a classic British audiophile speaker in terms of accuracy, I was amazed at the "aliveness" that seemed to come from the high efficiency and lack of compression. It was the closest I'd ever heard to a drum set sounding like real drums.
The only reason I got "British audiophile speaker" accuracy was because I fixed a bunch of problems with DSP. It would be VERY hard to pull it off with passive xovers. But the Faitals are much better designed than anything Klipsch was doing in the 1980s and the problems (horn throat reflections and the like) are redeemable.
What does a horn do? Think of it like a 10 speed bike. Direct radiators are like a bike that can ONLY pedal in first gear. In 1st gear, if you want to ride fast down a hill, your feet have to be cranking furiously and you almost fall off from the commotion. In 10th gear your bike can be going extremely fast but you are still pedaling slowly and using force instead of fast foot motion to propel yourself. That's what a horn does for a speaker.
A direct radiator speaker expends 99% of its energy pushing the cone back and forth and only 1% of that energy gets transmitted to the air. The air is too "thin." If we lived on a planet where the normal air pressure was 100 bars instead of 1 bar it would be a different story. You wouldn't need horns and a 6.5" woofer would naturally have an SPL of 110dB 1 watt.
Since our atmosphere is thin, a horn is an acoustic "gear" that matches the small surface area of the driver (throat) to a much larger surface area of the room (mouth). So the driver feeding the horn is moving microscopic distances (large Xmax NOT required) and still moving tons of air. The voice coil is "pushing hard" with minimal stroke length, just like a 10 speed bike in 10th gear.
This translates to what subjectively sounds like "speed" and "immediacy" and "slam" and "authority" and "effortlessness" and "dynamics" and "dynamic range to burn."
When I was 17 I used to obsess about low mass drivers, tweeters with only 0.2g moving mass because I thought that would give you "fast transient response" and that certainly makes sense if you only think of a driver as a linear device that is supposed to move back and forth. = "lumped parameter model." But that is not an accurate way to think of it. A driver is really an impedance matching device (= a gear) connecting the electromagnetic force to surrounding air. And besides, when you do the math, the mass cancels out anyway and mass determines the efficiency of the driver, not the bandwidth.
So if a direct radiator is 0.5 to 1% efficient and a horn is 5-30% efficient, it means energy is being harnessed to moving air much more effectively and you can indirectly hear that. All things being equal, a more efficient speaker always sounds better for some reason, and that's the reason.
For most horn tweeters, below something like 10KHz, most of the force of the voice coil is expended in moving air, and not sloshing the mass of the diaphragm back and forth. At some high frequency the mass starts to predominate and this is why horns have a downward sloping curve which has to be corrected.
Well it also turns out that if you choose the right horn expansion profile you get Constant Directivity, which basically looks like this:
This of course is the Bitches Brew polar heat map, and everything above 1100Hz is the radiation pattern of the Constant Directivity horn formed by the aperture and the cone.
It turns out that Constant Directivity profile is a huge advantage for stereo imaging because as you move off axis, the level drops evenly and tilts slightly down so if you toe the speakers in, every seat in the house is great. Compare this to a more typical plot that I grabbed off the internet:
...where the polar pattern is wide at low frequencies and narrow at high frequencies.
So going to your original question about dipole tweeters, all the ones I know of are direct radiators with polar patterns like the one immediately above, and not like CD horns.
I can imagine having a coax with a horn on both sides. It might be kind of ridiculous but worth it for someone who wants to try. (It would have many difficulties which I don't care to get into.)
So that's why I put CD horns on both sides of my designs.
I have hard time to understand why you call this speaker a constant directivity design with a polar response like this:
This is nowhere near constant directivity, IMO.
Many 2 way speakers advertised as "CD" have no directivity at all below 500Hz and increasing directivity above that. Do those count as CD?
Is it reasonable to label the Faitals as CD given that their directivity also extends below 100Hz?
At 75 degrees off axis the drop in SPL ranges from 5-10dB, up to 6KHz. Above 6K the pattern widens. I published the data for all to see. I acknowledge that it's far from perfect.
How would you categorize it?
Is it reasonable to label the Faitals as CD given that their directivity also extends below 100Hz?
At 75 degrees off axis the drop in SPL ranges from 5-10dB, up to 6KHz. Above 6K the pattern widens. I published the data for all to see. I acknowledge that it's far from perfect.
How would you categorize it?
I would call it simply "chaotic directivity" design. Just look at that rollercoaster polar response from about 1 kHz up to 20 kHz. The directivity below 1 kHz is constant-like, but have way too wide dispersion compared to the upper midrange-lower treble region and it becomes very wide (too wide, chaotic, diffracted) again from around 6-7 kHz.
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That's okay, but it's not a constant directivity speaker if we consider the whole audible spectrum (or just I am too nitpicking
). Anyway sorry for the off-topic!
Or a transformer. The impedance of the air is this - at 1 bar - and the speaker is that. So a lot of force at the little end matches up efficiently to little force spread across the big end.
I once remarked about the cones seen at the end of rocket engines. A friend who actually spent some time as a rocket engine designer told me that their shape changes, depending on what part of the atmosphere their intended use is in. They have a shape for the vacuum of space too, where I suppose the impedance you try to match is infinite.
The high force idea is almost counterintuitive. People obsess about what their preamp has to drive; if it's 1k "Oh My God - it's going to effect how it sounds" when the preamp output is a few dozen Ohms. One would think blasting sound right up against a phase plug, then squirting through some narrow slits and then a venturi would cause all kind of havoc. Of course, the opposite happens. Audio...
Ah, that makes more sense. The engineering side of my brain translated this as the coupling efficiency between the impulse of the transducer and the desired movement of the medium (air). Thanks!
Ok, major digression here to build on @jjasniew's thoughts... in college I had to take compressible flow fluid mechanics to complete my degree. The only thing I remember out of that (for me) not particularly wonderful personal experience is why every kid learns to draw rocket engines as triangles that open out away from the rocket itself. Why?
It turns out that you can only use a funnel/nozzle to get a fluid up to mach 1 at those conditions. No matter how much pressure you have before the funnel, you won't exceed mach 1! This usually isn't good news for escaping gravity.
However, if you get a fluid to mach 1 and then add an appropriately designed diffuser (the triangle on the rocket) you can get the fluid way past mach 1 and generate enough force to drive that rocket a heck of a lot faster. Thus, as you pass mach 1 a diffuser is actually a hypersonic nozzle, and at > mach 1 a nozzle is a hypersonic diffuser.
So... could a compression driver make a sonic boom in my living room?
Back to normal programming, @jjasniew's description of the compression driver mechanics was delightful.
Is there actually a generally understood definition of what constitutes Constant Directivity?
It turns out that you can only use a funnel/nozzle to get a fluid up to mach 1 at those conditions. No matter how much pressure you have before the funnel, you won't exceed mach 1! This usually isn't good news for escaping gravity.
However, if you get a fluid to mach 1 and then add an appropriately designed diffuser (the triangle on the rocket) you can get the fluid way past mach 1 and generate enough force to drive that rocket a heck of a lot faster. Thus, as you pass mach 1 a diffuser is actually a hypersonic nozzle, and at > mach 1 a nozzle is a hypersonic diffuser.
So... could a compression driver make a sonic boom in my living room?
Back to normal programming, @jjasniew's description of the compression driver mechanics was delightful.
Is there actually a generally understood definition of what constitutes Constant Directivity?
Constant directivity speaker is that which exhibit the same spectral balance to all directions. In real world, it's not easy to create such a speaker from 20 Hz to 20 kHz, hence the more similar the off-axis responses to the on-axis response the more we can call it constant directivity. That's my defiintion, although maybe wrong.
This is a great definition right here: https://audioroundtable.com/forum/index.php?t=msg&th=18610&goto=76814&#msg_76814
In the last couple of days I've been skimming through a bunch of dipole and OB material, to the extent that I've completely lost track of which references were in which threads or even forums.
That said, with regards to Constant Directivity I recall reading some comments that those who were most interested in achieving CD were tending to converge on nude drivers, particularly for extending CD to higher frequency ranges. Or maybe my non-eidetic memory is mangling it and it was more that they discovered that the nude drivers were resulting in better CD?
Anyway, it's interesting that (at least with your Bitches Brew polar heat map above) you've achieved good results with what seems like the exact opposite of a nude driver, namely a coax driver in a wide plank of beautiful wood.
Are there multiple "recipes" for achieving Constant Directivity, which I'm realizing I've always been looking for in speaker implementations?
That said, with regards to Constant Directivity I recall reading some comments that those who were most interested in achieving CD were tending to converge on nude drivers, particularly for extending CD to higher frequency ranges. Or maybe my non-eidetic memory is mangling it and it was more that they discovered that the nude drivers were resulting in better CD?
Anyway, it's interesting that (at least with your Bitches Brew polar heat map above) you've achieved good results with what seems like the exact opposite of a nude driver, namely a coax driver in a wide plank of beautiful wood.
Are there multiple "recipes" for achieving Constant Directivity, which I'm realizing I've always been looking for in speaker implementations?
dayneger,
CD goal is very diffficult, and another aspect is polar pattern 0-180deg (also vertically) and third is level of Directivity Index DI.
MEH like Danley Synergy is very constant with very high DI.
With dipoles one will get CD with dipole pattern only below dipole nulling. This will lead to 4-way constuction... Here is good info in German, but English summary ia available
CD goal is very diffficult, and another aspect is polar pattern 0-180deg (also vertically) and third is level of Directivity Index DI.
MEH like Danley Synergy is very constant with very high DI.
With dipoles one will get CD with dipole pattern only below dipole nulling. This will lead to 4-way constuction... Here is good info in German, but English summary ia available