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Celestion Axi2050 2" compression driver on K-402 horn and Jubilee bass bin


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The Celestion Axi2050 is a new 2" throat compression driver with a very large diameter ring radiator diaphragm that uses advanced design techniques to avoid the problems of other dome-type titanium diaphragm 2" throat drivers.  More on this subject can be found on the web in the form a fairly lengthy YouTube video.  This is the driver that Roy has announced will be the compression driver used in the new upcoming "The Jubilee" that's slated to be released this summer, again using the K-402 horn and a redesigned bass bin with an internally ported single 12" driver.

 

1586062941719-png.57268

 

 

Some plots of the Celestion Axi2050 on a K-402 horn on top of my right Jubilee bass bin follow.  First the raw, uncorrected response of both drivers.  I use this plot to help determine the best crossover frequency:

 

2037477515_CelestionAxi2050onK-402andJubileeBassBinRawSPLResponse.jpg.6ac4783b844bf21fab64153f6bd7cc94.jpg

 

and the phase plot of the same data:

 

1288701644_CelestionAxi2050onK-402andJubileeBassBinRawPhaseResponse.jpg.050c8e9211aee43ace90d35a61bb906b.jpg

 

Note the suggested crossover point between the bass bin and the K-402 is about 225 Hz by these plots.  I've found that 225 Hz frequency is a fairly good place to cross, or a little higher--about 300 Hz.  There is a tradeoff in harmonic distortion levels at crossover, but it's not a strong factor, in my opinion. 

 

You might not be aware of the issue with the "W" section bass bins that have a truncated mouth (i.e., a flat baffle between the two horn mouths side-by-side).  This introduces polar coverage issues above the frequency where the separation distance of the two horn mouths is more than 1/4 wavelength.  For the Jubilee bass bin, that frequency is about 225 Hz.  So crossing over at that low frequency (225 Hz) has the advantage of avoiding the narrowing of the bass bin polars that occurs in the current two-way home Jubilee, and the polar coverage of the K-402 and the bass bin are roughly about 90-100 degrees included angle. 

 

I can see why Roy liked the Axi2050, since it easily crosses about an octave below the other 2" compression drivers and can avoid the polar narrowing problems of the "W" section bass bins.

 

The phase plot also shows the large overlap between the two horns/drivers, which indicates the design flexibility of where the crossover point can be located.  From that plot, the crossover frequency can be about 190 Hz (where the Axi2050 on a K-402 horn really begins to lose on-axis SPL response) all the way up to about 800-900 Hz, where the Jubilee bass bin begins to lose on-axis SPL response.  That's as wide a response overlap band that I've seen, and indicates great flexibility.  The reason, as I said above, to set the crossover frequency at 225 Hz is to avoid crossover interference band polar narrowing with the "W" section bass bin. 

 

In an MEH, the choice of where to put the crossover is dependent on the placement of the woofer ports (I call these the "off-axis ports").  In my K-402-MEH horn, I cut these ports so that the crossover frequency would be about 480-500 Hz (which is 1/4 wavelength axially from the beginning of the off-axis ports to the mouth of the K-402 horn). There is a natural acoustic cutoff frequency due to the placement of these off-axis ports that you determine by the port placements.  In an K-402-MEH using the Axi2040 drivers, this placement of the woofer off-axis ports could be about double the distance from the throat as my prototype MEH--about 5" axially presently to about 10" axially.  If you measure along to the horn wall (which is flat as a board in this area), it can move its beginning radius of the off-axis woofer ports from about 6" from the throat entrance to about 12". This is the reason why I tested the Axi2040 on a full K-402 horn (without off-axis MEH ports), because I had anticipated the low frequency performance of this compression driver to be quite a bit lower than all other 2" compression drivers--and it was: about full octave lower.

 

Another view of the difference between the two drivers in terms of their raw response on a K-402 horn.  Note that the relative drive level and resulting SPL of these two measurements are not the same:

 

1242018797_CelestionAxi2050RawResponse(Red)vs.TADTD-4002(Blue)onK-402Horn.jpg.f7069e07971adb83b8382a5f8ec1f1ce.jpg

 

Here is the corresponding phase response of the two drivers:

 

2109097268_CelestionAxi2050RawPhaseResponse(Red)vs.TADTD-4002(Blue)onK-402Horn.jpg.15a611b6b168eaf6d88857fe4c38bb10.jpg

 

and the step response (a one-to-one comparison here):

 

380598635_CelestionAxi2050RawStepResponse(Red)vs.TADTD-4002(Blue)onK-402Horn.jpg.8702519df67f00968b593e14e8db4d45.jpg

 

This shows that the moving mass of the Axi2050 is still higher than the TAD TD-4002, but the offsetting low end response and the lower cost of the driver (about 2.5x lower in new condition) is an offsetting factor.

 

Here is the "predicted SPL response", in other words, the response based on initial flattening of the two drivers' responses, without extra effort to extend their responses on either end of the spectrum (high or low) based on the REW EQ facility's initial responses that I ran:

 

447068583_CelestionAxi2050RawPredictedSPLResponse(Red)vs.TADTD-4002(Blue)onK-402Horn.jpg.ebd87c22c1eaf91642a13684a76dca65.jpg

 

This plot really shows you the relative response of each driver in as close to an "apples vs. apples" fashion as is possible.

 

Here is the present case of flattened SPL response of the Axi2050 vs. TAD 4002 compression drivers on the same K-402 horn in the same room/microphone position, with the orange trace having an "in-phase" bass bin with the Axi2050 and the green trace having flopped phase in order to pull the phase of the K-402 and bass bin closer together, using the same PEQs to flatten the response:

 

1300210300_Axi2050(GreenandOrange)vsTAD4002(Blue)SPLResponsewithJubBassBin.jpg.292c8a635b5ed68aad17c5165f2432bf.jpg

 

That isn't as remarkable as the following phase response, which tells a different story:

 

185341529_Axi2050(GreenandOrange)vsTAD4002(Blue)PhaseResponsewithJubBassBin.jpg.48ca5edff8806d7673867e5bab650b87.jpg

 

The step response of the three cases are shown below:

 

760241126_Axi2050(GreenandOrange)vsTAD4002(Blue)StepResponsewithJubBassBin.jpg.620be54eba61ff93d2bcc9d0486df9de.jpg

 

So the option of having flatter overall phase response also implies using more PEQs to push the SPL response back to flat SPL again (not compensated above).  In the traces above, no named crossover filters are used to cross the bass bin to the K-402 high frequency horn.  Perhaps more discussion on that trade to come.

 

Here are the Xilica settings that I used for the Axi2050 channel:

 

1090123242_Axi2050onK-402HornPEQsfromXilicaXConsole.thumb.GIF.ff343e587d06a1884eb7335ddedf4220.GIF

 

Here are the relative PEQ settings use for the TAD TD-4002 driver and plotted (yellow trace) over the top of Celestion Axi2050 driver PEQs on a K-402 horn (white trace):

 

1756239468_TAD4002PEQsusedvsCelestionAxi2050netPEQs.thumb.GIF.78b2a9add930f03cadec539b79d84380.GIF

 

Chris

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Listening Impressions:

 

As far as I can tell, the Axi2050 is pretty much a match for the TAD TD-4002, with the understanding that there is a very, very small apparent difference in "sparkle" or "air" on the very top end.  It is so small that I doubt I could pick it out on a blind-blind A-B comparison test, unless the test music used was very specific to show the differences. My guess is that no one else would hear it either since it would take a very careful and meticulous dialing-in process in both cases (in-room EQ and delays).  This implies to me that I could be making my judgment between the two based only on sighted bias.  I think the two drivers are fully interchangeable in terms of their resulting sound quality after being very carefully dialed in.  I have been playing the TAD TD-4002 on the left channel and the Axi2050 on the right channel for a couple of days now, and can make no observations about left-right sound quality/balance other than the sparkle comment I made above--subject to sighted bias.

 

The difference in crossing the K-402/Axi2050 an octave lower than the K-402/TAD TD-4002 is not generally audible, although I have lowered the K-402 on top of the Jubilee bass bins in both cases to minimize the vertical separation issues between the two horns.  It seems to me that the Axi2050 on the right, crossed an octave lower than the TAD TD-4002 on the left, makes a very, very subtle difference, and only if moving well outside of the listening position(s) laterally.  The right channel (Axi2050) may sound a little more "full" in the lower midrange (225-500 Hz) which is difficult to pick out, but I would expect this might become more audible over time if listened to extensively.  I can't make a judgment presently, but the idea (in my mind's eye) of crossing an octave lower is one that I would welcome--it's just that I'm not sure that I can really hear it presently.

 

I would say this driver can't really be beat in terms of sound quality, equal to the sound quality of the TAD TD-4002s, and having an extra octave of low end response that the K-402 horn can easily take advantage of.

 

One more point: I have seen no other horns that can fully take advantage of this driver's very broad-band performance than the K-402 horn.  Even the largest SEOS 30 horn isn't big enough to take advantage of the extended low end of this new Celestion Axi2050 driver.

 

Chris

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Now for a discussion of the relative advantage or differences using the Axi2050 on a K-402-based MEH:

 

Already, I think you can see that there probably won't be a way to measure and listen to the Axi2050 on a K-402-like horn until the off-axis ports are moved farther away from the horn throat toward the horn's mouth (about double the distance in order to cross over to the woofers an octave lower).

 

So what does moving the woofer off-ports closer to the mouth result in?  Well, the farther the woofer ports are from the horn throat, the lower the first-bounce cutoff frequency of the woofers to the throat return bounce (about an octave lower).  What's usually forgotten in this discussion is that the woofers themselves will gain lower end response due to the fact that they will be located at a point on the horn with a lower area expansion rate, which is a function of straight-sided horns, commonly called "conical horns" but which are more properly called "straight-sided" because their area expansion formulae along the central horn axis is not generally a strict  "x2" area expansion rate.

 

So what?  Well, this means that the K-402-MEH based on an Axi2050 driver can actually play a little lower than the equivalent horn using compression drivers that cross about an octave higher.  A plot of the distance along the central axis of the "loading frequency" of the woofers vs. their distance from the horn throat (as plotted by Danley):

 

striaght-sided horn off-axis port loading curve.JPG

 

It's not a lot of difference, especially considering the frequency decreases below the point at which the first 1/4 wavelength is fully contained within the K-402 horn.  Below that frequency, the first 1/4 wavelength begins to use the room boundaries to support the fundamental part of the wavelength formation.  But it turns out that every little bit helps, as is true with almost all considerations of woofers and horns below 200 Hz.

 

So to see and hear the effects of moving the woofer ports farther away from the horn throat, another K-402 horn will need to be modified with off-axis ports in the right places.

 

One more consideration: the horizontal off-axis polar coverage of the K-402-MEH prototype at and just below the internal crossover frequency suffers just a little.  In the prototype K-402-MEH, the off-axis polars are somewhat decreased from 450-500 Hz, as can be seen below in its horizontal polar sonogram a little below 500 Hz as a little local "waistbanding":

 

K-402-MEH horizonal normalized sonogram.jpg

 

The interesting thing is that by moving that little disturbance down one octave to just above 200 Hz, the ability of the human hearing system to pick out that polar disturbance is less discerning.  In the case of the Axi2050, it may well be that it becomes inaudible, since it might fall below your listening room' Schroeder (a.k.a. transition) frequency.  This is a very good thing.

 

So the first question might be: "do I need to move the ports closer to the mouth of the K-402-MEH?".  The answer is, "no", you can leave them where they are at and simply cross the Axi2050 compression drivers at a lower frequency to the woofers.  What is the effect?  Very, very small, in my estimation.

 

Chris

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One set of plots that I didn't plot above is harmonic distortion.  I see no real differences between the TAD TD-4002 and Axi2050 drivers across their respective passbands.  Since THD is basically only showing you second harmonic distortion, in order to see the higher order (and therefore, more audible) harmonics, I have to plot those separately.  First the TAD driver on a full-up Jubilee with bass bin at 93 dB (at one metre microphone distance, crossed at ~525 Hz) :

 

131912273_TADTD-4002JubileeHrmonicDistortionat93dB(1m).thumb.jpg.968532f39ccb23a92701c217711519f3.jpg

 

Then the same harmonic distortion levels at 93 dB for the Axi2050 with Jubilee bass bin (crossed at 225 Hz):

 

1781341983_CelestionAxi2050JubileeHarmonicDistortionat93dB(1m).thumb.jpg.3465db629f8be4d023623fdc095abf5a.jpg

 

Chris

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Good stuff here.  Interesting.  My opinion is that even as old a design as the TAD is it still hangs in there and does appear to have a small advantage at the top end.  I figured the Celestion being so new and with all the available new technology that it would really show the TAD up.  Which is not the case.  I guess I'll keep my TADs.  I have 4 and paid a lot less than the cost of these new Celestions.  I was just about to buy a pair just to try.  Now I will wait at least until I hear the new Jubs.  But it's nice to see there are equivalent drivers now, at any price.  Every other driver I tried never measured up to the realistic sound of the TADs.  Of course that is just my opinion.  Nice job!

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On 3/5/2021 at 5:14 PM, Chris A said:

The Celestion Axi2050 is a new 2" throat compression driver with a very large diameter ring radiator diaphragm that uses advanced design techniques to avoid the problems of other dome-type titanium diaphragm 2" throat drivers

 

I had been intrigued by the design since first learning about them, and when I saw that the New Jubilee is equipped with these Celestion drivers, I got a pair for my K-402 horns. 

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@mark1101 though there are parts of your statement I would have to agree with, there are a couple perspectives and even a question that may change one's thoughts.

 

Everyone trys to justify and upgrade or upgrade by price. One in most situations would have to look at this as if they were deciding on drivers if purchasing new. That being said, think the Celestion would be the better route, even if considering new Celestion over current market pricing of used TADs.

 

I was also under the impression that Roy designed a different phase plug for the Celestion. If that be the case, how much more of an improvement does that Celestion driver on the K402 offer? Also, was Chris able to obtain these versions to compare and if not, how much better than are the new Klipsch Celestion versions over the TAD? Is it possible that Roy designed a better driver/horn combo that is now serviceable, obtainable, and more cost effective?

 

I was chasing alot of those questions with BMS coaxial.

 

Sent from my SM-G986U using Tapatalk

 

 

 

 

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8 hours ago, The Dude said:

I was also under the impression that Roy designed a different phase plug for the Celestion.

Roy has apparently designed an in-throat acoustic lens to spread out the polars above 6-8 kHz and he's stated that it works in that regard only up to ~13-14 kHz.  The Axi2050's 3-part phase plug (which is extensive) is apparently untouched.

 

I think it's easier in a home environment just to point the loudspeakers at the listening position a little more because at those frequencies, they're not really bouncing off the room's boundaries and arriving at the listener's ears to increase the perception of "image broadening" that Toole refers to.  At those frequencies, you're only getting the direct arrivals, and you're not hearing very much from in-room reflections, anyway.  Pointing the loudspeakers at your listening position is much more effective in that regard. 

 

Now, if you're designing a loudspeaker for commercial cinema duty, that post-phase plug in-throat lens might make a lot more sense, since the audience needs uniform illumination across that frequency band at every seat in the auditorium.  They can't all be at a "sweet spot".  But in a home environment, the listeners (more than one) can easily accommodate being within 15-20 degrees on-axis by positioning the loudspeakers accordingly at the geometric center of the listener positions.

 

So in other words, that money may be spent better elsewhere--like with a bass bin that has a bit more driver area to reduce modulation distortion due to the higher excursions of the fully horn-loaded single 12" woofer (even with a rear wave rectifier--the internal bass reflex ports), or adding a nose to the bass bin to spread out those lower midrange polars more effectively.   YMMV.

 

8 hours ago, The Dude said:

That being said, think the Celestion would be the better route, even if considering new Celestion over current market pricing of used TADs.

I think that I said that, above.  The Axi2050 cost is lower (in general) than other well-designed 2" throat beryllium diaphragm drivers, and the f3 of the horn/driver is an octave lower than all other 2" compression drivers on a K-402 horn. 

 

If the affinity for "W" section dual mouth folded horn bass bins is still overriding, then using the Axi2050 addresses the one true Achilles heel of the Jubilee (present and future version): its lower midrange crossover interference band jump from the centerline of the K-402 to the centerline of the bass bin, which comes at a point that's in the middle of the vocal range (400-600 Hz) in the present model.  I simply move the K-402 horn closer to the centerline of the bass bin to reduce this issue, and while this is a significant improvement in that area, doesn't actually solve that issue. Crossing over an octave lower is another way to lessen this issue (and the related issue of the truncated horn mouths that do not rejoin).  Elimination of that issue is available by using a full-range MEH approach.

 

Chris

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3 hours ago, Chris A said:

Roy has apparently designed an in-throat acoustic lens to spread out the polars above 6-8 kHz and he's stated that it works in that regard only up to ~13-14 kHz.  The Axi2050's 3-part phase plug (which is extensive) is apparently untouched.

 

I think it's easier in a home environment just to point the loudspeakers at the listening position a little more because at those frequencies, they're not really bouncing off the room's boundaries and arriving at the listener's ears to increase the perception of "image broadening" that Toole refers to.  At those frequencies, you're only getting the direct arrivals, and you're not hearing very much from in-room reflections, anyway.  Pointing the loudspeakers at your listening position is much more effective in that regard. 

 

Now, if you're designing a loudspeaker for commercial cinema duty, that post-phase plug in-throat lens might make a lot more sense, since the audience needs uniform illumination across that frequency band at every seat in the auditorium.  They can't all be at a "sweet spot".

 

There is yet another consideration that is seldom mentioned -- the natural attenuation of high frequencies in air, see here, for example. Under typical conditions, the attenuation at 10 kHz is only 0.15 dB per meter, while at 20 kHz it's 0.51 dB per meter. In a living room, where listening distance is typically under 3 meters, the effect is minor. But in a theater or auditorium, where listening distance might be 10-100 meters, the attenuation at 10 kHz is 1.5 dB to 15 dB, while at 20 kHz it's 5.1 db to 51 dB.

 

My point is that extending the high frequency response of a tweeter driver only makes sense in a home listening situation, because in a commercial situation nature is fighting back ... and winning.

 

absorption.png

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32 minutes ago, Edgar said:

My point is that extending the high frequency response of a tweeter driver only makes sense in a home listening situation, because in a commercial situation nature is fighting back ... and winning.

 

What looks great on a glossy sales brochure (or an EASE data file, as the case may be) and what actually makes a difference to movie-goers scattered throughout a commercial cinema auditorium is always confounded (in the lean/six sigma sense) with human decision making and organizational behavior. 

 

I'm pretty well versed on that subject as that's a major portion of the decision making of what goes into the product and what doesn't (and how much it costs) in the field of system architecting.  You sell to one group of people (customer's decision makers and/or buyers), but another group takes delivery of the product/system (the system installation sites), and yet another group actually uses the products/systems (the users: you and I in this case), and all three groups do not have congruent needs/wants.  So the price of the product rises, but the utility of the product for the end users doesn't usually reflect their optimal needs.

 

In the case of cinema, unless the buyers are also sitting in the (fully populated) audience, the price rises or, considering lowest-cost acquisition approaches, the sound quality suffers accordingly. 

 

An observation: every cinema that I go into over the past 10 years or so that has the name "JBL" on the loudspeakers has been a big letdown in terms of the sound quality (for instance).  And what usually happens is that during the physical setup and dialing-in of large cinema loudspeaker arrays: somewhere in the center of the audience apparently gets the best sound, but the other seats...not so much. Even though the users don't really care about some capabilities of the components (e.g., very high frequency coverage), the loudspeakers chosen will have them, nevertheless, if the decision maker is reading or looking (with their eyes only)...instead of listening critically and thoroughly. 

 

Each customer functional group gets what they want to some degree, and it's the acquirers/buyers that usually have the loudest voice in that process.  And they largely sit in the prime audience seats (I would imagine) when making those decisions--or they're sitting at their desks trying to figure out which offering has the best "technical merit" based on the EASE data, and make their decisions accordingly, perhaps without actually listening to the resulting systems in a full audience.

 

Chris

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15 hours ago, The Dude said:

@mark1101 though there are parts of your statement I would have to agree with, there are a couple perspectives and even a question that may change one's thoughts.

 

Everyone trys to justify and upgrade or upgrade by price. One in most situations would have to look at this as if they were deciding on drivers if purchasing new. That being said, think the Celestion would be the better route, even if considering new Celestion over current market pricing of used TADs.

 

I was also under the impression that Roy designed a different phase plug for the Celestion. If that be the case, how much more of an improvement does that Celestion driver on the K402 offer? Also, was Chris able to obtain these versions to compare and if not, how much better than are the new Klipsch Celestion versions over the TAD? Is it possible that Roy designed a better driver/horn combo that is now serviceable, obtainable, and more cost effective?

 

I was chasing alot of those questions with BMS coaxial.

 

Sent from my SM-G986U using Tapatalk

 

 

 

 

 

Not to be misunderstood............I bet the Celestions are terrific.  They should be the best you can get right now.   If I didn't have TADs I would already own the Celestions.  It's just that I have plenty of the TAD drivers at the moment, and I am happy with them........so no need to run out for something this soon that is likely a lateral move.  I trust Chris's measurements and impressions and they don't indicate any significant listening advantages initially, or in a room, or with any specific type of music.  Time may tell.  I did see that because they can cross so low they can reduce the beaming of the Jub cabinet..........but that it was difficult to hear that improvement.  That may change with different music or equipment.  So for now I am all for the Celestions.  However, I can wait awhile for them.

 

You should post your listening experience with them so far.

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23 hours ago, mark1101 said:

It's just that I have plenty of the TAD drivers at the moment, and I am happy with them........so no need to run out for something this soon that is likely a lateral move. 

Solid point, thanks for the follow up. 

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I tested the AXi2050 on K-402 in 2019 and did a direct comparison to Radian 950BePB. Back and forth for several days both in mono for quick comparisons and listening in stereo, though swapping for stereo takes time when you only have one pair of speakers. 

 

My experience was quite different from Chris'. The Radian with Be sounded considerably clearer and more open in both the upper midrange and tweeter. Distortion measurements confirmed this. Crossover lower was nice though and mye experience her was also different. While it didn't experience this as night and day, it was still more than a subtle improvement in a coherent sound stage and vocal presentation. But overall, the Axi2050 sounded dull in the upper frequencies making it boring to listen to compared to Radian. 

 

But I'm not surprised Klipsch is choosing such a driver for a commercial speaker and that solved issues with the bass bin they use.

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If I might ask, how flat did you EQ the top end of the Axi2050, @Bjorn?  The TAD 4002s actually require a little attenuating PEQ on the top end, and easily extend their response somewhat above 20 kHz (which I typically don't test beyond 21 kHz).  For younger folks that are still bothered by/can hear the ballast buzzing of fluorescent lights (about 16.5 kHz), I can understand that you might perceive this difference much more than I would. 

 

I added an 8 dB, 0.21 octave (BW) boost at 18 kHz, the differences between the TAD TD-4002 on the left and the Axi-2050 on the right were significantly decreased in terms of the high frequency "air" (for my hearing), but still present to a fairly subtle degree, which is what I reported. 

 

I typically don't hand out poor reviews on audio equipment based on very slight differences--like I perceive in this case--but I'm the first to acknowledge that presbycusis is a factor in the differences we're reporting.  For my ears, the difference is like listening to the TADs using a Crown D-75A amplifier vs. something with a much better bandwidth /slew rate (like the First Watt F3 that I use)--which is more of a subconscious difference rather than an overt difference.

 

I can both hear and measure the effects of the decrease in crossover frequency--listening to voices and their relative fullness, but it's not a strong difference--more like something that I could hear after listening to them A-B over a period of more than a couple of days of listening.  The Jubilees have a tendency to sound a bit muffled when one is listening to them while laying on the floor between them about 6-8 feet away, vs. listening to them while seating properly in the reclining chairs just behind (i.e., vertical lobing), but not really in the horizontal direction, which seems basically unchanging from side wall to side wall (the room dimensions can be found in my profile page). 

 

Chris

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Good work, Chris as always. Thorough and compelling. I have been enjoying 300 Hz. crossover to my mid horns for over 10 years now. I never want to go back to higher Xover points, unless it's hybrid horn tops/direct radiator bottoms, but that would be for surround duty only, never mains.

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When using the TADs full range (no tweeter) I have a -3db PEQ at 16K (don't have the Q handy).  They are hot up top but clean and clear.

 

I have never heard the radians as of yet.

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54 minutes ago, Chris A said:

If I might ask, how flat did you EQ the top end of the Axi2050, Bjorn?  The TAD 4002s actually require a little attenuating PEQ on the top end, and easily extend their response somewhat above 20 kHz (which I typically don't test beyond 21 kHz).  For younger folks that are still bothered by/can hear the ballast buzzing of fluorescent lights (about 16. 5 kHz), I can understand that you might perceive this difference much more than I would. 

 

I added an 8 dB, 0.21 octave (BW) boost at 18 kHz, the differences between the TAD TD-4002 on the left and the Axi-2050 on the right were significantly decreased in terms of the high frequency "air" (for my hearing), but still present to a fairly subtle degree, which is what I reported. 

 

I typically don't hand out poor reviews on audio equipment based on very slight differences--like I perceive in this case--but I'm the first to acknowledge that presbycusis is a factor in the differences we're reporting.  For my ears, the difference is like listening to the TADs using a Crown D-75A amplifier vs. something with a much better bandwidth /slew rate (like the First Watt F3 that I use)--which is more of a subconscious difference rather than an overt difference.

 

I can both hear and measure the effects of the decrease in crossover frequency--listening to voices and their relative fullness, but it's not a strong difference--more like something that I could hear after listening to them A-B over a period of more than a couple of days of listening.  The Jubilees have a tendency to sound a bit muffled when one is listening to them while laying on the floor between them about 6-8 feet away, and listening to them while seating properly in the reclining chairs just behind (i.e., vertical lobing), but not really in the horizontal direction, which seems basically unchanging from side wall to side wall (the room dimensions can be found in my profile page). 

 

Chris

I'm certainly now talking about the frequencies around 16.5 KHz. I said upper midrange and treble. Obviously it's quite difficult to pinpoint what frequencies one is hearing the difference at, but my experience was this was also lower than only the very highest frequencies. Besides, my distortion measurements confirmed that the distortion already above 550 Hz was higher for the Axi2050. Below 180 Hz I saw lower distortion with Axi2050.

 

Actually, when listening to AXi2050 in the beginning I didn't notice it. When listening more I starting asking myself if something wasn't missing and it lacked some openness. I then started doing more serious AB listening tests and with various music material it became very evident. That being said, I'm a critical listener and details might be bigger for me than many others. So your mileage may vary. I know of two others in Norway have tested the AXi2050 with different horns and they came to the same conclusion as me by the way. One ended up using a tweeter crossed at around 4 KHz (bad place to cross IMO).

 

Below is a raw measurement of both drivers at 1 m distance. I need to look at EQ setting or measurements to answer your question, but I don't really think the super high frequencies are relevant here.

 

Red=Radian

Blue=Celestion

 

1/24 oct smoothing.

1768801292_CelestionAXi2050vsRadian951BePBiKlipschK40224octsmoothing1mdistance.thumb.jpg.979fac3fa72ec6c3360139564bf0ca91.jpg

 

The cancellation at 700-800 Hz for Radian seems to be something with the combination of the driver and K-402. I haven't seen that with other horns.

 

 

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