Audio Note AX-Two stand-mounted loudspeakers

Audio Note AX-Two stand-mounted loudspeaker

I have to confess that initially I was impressed neither by their look nor by their sound. It was a year ago when I climbed the stairs up to my apartment carrying the 15 kg heavy box that Andy Whittle handed me after a short stop at my place on his way to Copenhagen. “These are your new speakers, give them some time to properly break in,” were his words.

At the time they arrived I was playing with the Micro Block DIY speakers and I really thought Whittle’s creations will have hard time against the Timmermanns’. And my expectations were confirmed on the first listen. They were disappointment and didn’t come nowhere near Micro Block’s dynamics, bass extension and sense of gravity. I didn’t want to waste my time with them but to continue to experiment with stuffing, port and crossover adjustments of Micro Block. So after a short listening I put them back in their box, sealed it off with a tape and called it a day. I realized that I don’t want to spend dozens of hours in front of these unimpressive speakers expecting them to improve with time when I have such an interesting project going. So I wrote to Peter that I am done with them and actually don’t like them:

I gave them AX Two a try yesterday, but got rather unsatisfactory results, they sound pretty unspectacular and cheap, rather big step backwards in comparison to my current speakers. They might improve after some more hours of use but I doubt that they will ever reach near the level of performance of Micro Block MK2.

But however impressive Micro Block sounded I eventually grew dissatisfied with them, there was a sort of glare in the midrange region I was not able to tame. Another thing that bothered me was the inconsistency in the detail retrieval across the frequency spectrum, the bass was lacking resolution and sounded sort of a one-note, they were simply putting some sort of signature upon the music that was drawing my attention constantly. And I confess I made few mistakes by deviating from the original design proposed by Bernd Timmermanns. The first one being the choice of enclosure material in favor of plywood instead of MDF. My advice to anyone who decides to build Micro Block is to keep to the origin and use MDF. It might sound counter-intuitive but in certain cases MDF or even chipboard is preferable to plywood. I had a conversation on that topic with the loudspeaker designer David Haigner and his opinion is that especially because of the inconsistency of the wood quality, plywood as an ever changing target with strong and narrow resonances is harder to “tune” than the higher damping MDF. He also considers that the popularity of plywood within the DIY circles is due to the fact that it presents a finished surface requiring little effort to look good. So I am inclined to think that the aforementioned coloration could also be contributed to the choice of enclosure material. This sort of glare effect became even more pronounced after I decided to glue together the internal braces. So my advice is – try not to be smarter than the designer but keep to the original concept.

Fast forward – few months later

Eventually I reached a state of burn-out when I was listening no more to music but to defects of the reproduction and that was the point I had no other choice but to give the AX-Two a second chance. And this time it worked out. I guess I should have gone through this struggle in order to appreciate the innate musicality of AX-Two. In fact they felt like a breeze, stepping out of the way, not drawing attention to themselves they simply allowed me to appreciate music. And I had no wish to fiddle with them at all. Not that they were perfect, but they simply let the music be, without putting a stamp on it. I felt sorry for my rash conclusions and I couldn’t believe I’ve judged them so badly at the beginning. Although they still lacked the sense of weight and sheer slam of Micro Block they sounded extremely coherent, almost like a single driver speaker. I also noticed the very well defined soundstage projected in a natural perspective way behind the speakers. I learned a lesson this time, an important one which Peter summarized with the following words:

Listening is a learning process, often what impresses initially is not right, so no need for excuses, I am happy you got to the right conclusion eventually, your journey should be written down in your blog as well, as it us a useful reminder to readers that first impressions are not always that valid against a longer term.

Peter Qvortrup

With careful set-up and more run-in time behind their back AX-Two inevitably started also to impress. What I discovered and would like to share is that a key role of how extended a stand-mounted speaker will sound plays the stand itself. I use a heavy steel stands – Audio Note AN-K – that are not a welded design but assembled. Top and bottom plates of quite thick steel are attached to the hollow legs with bolts. The alloy from which the legs are made is quite inert and result of extensive experimentation. I got caught by surprise when I knocked them with a fingernail and there was no ringing whatsoever but a rather dull sound one usually does not associate with metal. I use them empty, coupled with the delivered spike sets to the floor and to the speakers respectively. I tried also Blue Tack and other putty material between the stands and the speakers but nothing came close to the dedicated spikes provided with the set in terms of bass response extension, clarity and natural build-up of harmonic overtones. The role of the spikes is to allow the stands to couple from one side to the floor, from the other to the speaker in order to serve as a mediator and channel the energy transfer between them. Using Blue Tack seems to impede this energy transfer by effectively cutting the speaker off the floor which to my opinion affects negatively the sense of realism. This effect is especially well observed when natural recordings with plenty of spatial cues are reproduced. But at the end, I think the way we set our speakers is part of the creative process most of us enjoy and see as an opportunity to express oneself and one’s understanding of what a good audio reproduction actually is. So I don’t want to claim this or that way is better but to encourage you to experiment in case you still feel there is a potential for improvement.

After a careful set-up what impresses the most is how transparent and open they sound while maintaining considerable bass extension and bloom – it is the transparency one usually gets with open baffle speakers combined with the full low-frequency extension of a ported box. It is really the key here – this sort of well balanced mixture of the best of both worlds, and I couldn’t stop wondering how is that possible. On the one hand it is the woofer itself – the venerable 6.5″ Vifa C17 featuring curvilinear paper cone, stamped steel basket and foam surround. This woofer has manifested itself in a range of commercially available loudspeakers during the 1980’s and 1990’s but most notably in the highly regarded Dali 104 loudspeakers. In fact these very same speakers were predecessors of the Living Voice Auditorium series of floor-standers started back in the early 1990’s. There is no wonder that this peculiarly looking woofer with its stamped metal chassis and short wave-guide extrusion is found also in Audio Note’s AX-Two stand-mounted loudspeakers. On the other hand it is that particular implementation I find very interesting and deserving a closer look.

Vifa C17WG-01 speaker driver

Trying to figure out what is the secret here I decided to check if the boxes are acoustically sealed, so I blew through the port and noticed that the air was escaping all around the woofer’s flange. And as it turned out there was no gasket between the woofer and the baffle. So the enclosure was “leaky”. But according to the theory in order to function properly a ported enclosure should be air tight. I realized that AX-Two behaves partly as bass-reflex, partly as aperiodic box and this should have been the main reason for the elegant amalgam of qualities it exhibits. Out of curiosity and to confirm my notion I decided to check how the speaker will behave if it is properly sealed. So I used the self adhesive foam gasket tape I had at hand to seal the woofers off and as you might guess – the magic was gone. Deprived of its aperiodic behavior this speaker sounded, let me say, quite typical. For me it was clear – we are talking here, as with everything Audio Note, for a rather unorthodox and well considered design that obviously leaves no place for dogmas. By carefully combining two distinct approaches to speaker design Audio Note has achieved what I perceive as an extremely transparent, dynamic and extended sound. The “leaky” enclosure seems to provide the Vifa C17 with ideal conditions to perform to its best, and on the other hand reduces the impedance peak at resonant frequency which makes it more amplifier-friendly.

Construction

The enclosure itself is made of 18 mm thick MDF finished in wood-grain vinyl and use a single sheet of 2 cm thick low density polyester felt covering the back and the sides. Sides, top and bottom panels are rabbeted so that they wrap around the front and the back panels with half of their thickness. There is no bracing of any sort. With a net volume of 11.5 liters and reflex-loading port dimensions of 3 cm in diameter and 10 cm length the enclosure is tuned at around 40 Hz resonant frequency which lays quite below the low frequency cut-off of the speaker which starts at 55 Hz. This is pretty unusual considering the fact that the vast majority of compact bass-reflex loudspeakers including Micro Block have their ported enclosures tuned at or slightly above the cut-off frequency. The fact is that AX-Two, as well as any other Audio Note speaker, is designed to work near room boundaries, thus the additional bass reinforcement from the nearby walls is part of the calculation. I can attest that this design concept works. Placed 15 cm from the wall, 2.40 meters apart these speakers produce an extremely clean and tuneful bass that makes Micro Block’s bass performance to sound kind of a one-note and lacking in resolution. True, the enclosure’s net volume and the woofer’s effective radiating area are other factors one have to consider, and they are all in favor of AX-Two, but here I talk about some substantial difference in quality that I think reflects the design principles behind.

Speaking about the bass performance I should not forget to mention the twitter – the 3/4″ silk dome Vifa D19 – also a long time favorite with long production history. I can’t help but think that this kind of perfect coherency I experience has something to do with the integration of both units within the crossover design. Throwing an eye on the circuit board I can see a neatly conceived dividing network featuring a second order 12 dB/Octave low-pass filter and a third order 18 dB/Octave high-pass one. Pretty straightforward design, no Zobel network or anything of that sort, 6 elements in total (in fact 7, due to space limitation two parallel connected capacitors are used instead of one). What impresses me most is the placement of the attenuation resistor in the high-pass section which is at the very start before the filter group. I have never seen Bernd doing this, in all of his projects the resistor or the voltage divider is always the last element placed after the filter group and just before the twitter. Judging by how seamless the integration feels I think placing the resistor at the very beginning is aimed at achieving a maximum phase linearity. I am impressed.

Audio Note AX-Two crossover board

Interestingly enough the Micro Block dividing network uses the same constellation of second order low-pass and third order high-pass filters but while Micro Block uses 12 elements to achieve that (without counting the elements in the recommended impedance linearization network) AX-Two as I said needs only 6. Where Micro Block resorts to Zobel network to electrically address phase angle anomalies AX-Two resorts to mechanical means by judicious mix of aperiodic and bass-reflex driver loading. Chasing simplicity by keeping the parts’ count low as the only way to achieve perfection is reflected in the whole philosophy of the British company and it could be traced across its entire product range. It is something that gives the brand consistency and characteristic signature. As a user I can attest that keep it simple but not simpler principle works here, AX-Two wins against Micro Block in all disciplines that are essential to communicate the emotional impact, the artistic message and aesthetic value of a record.

My amazement continues to grow by the fact that even though the cheapest electrolytic capacitors are used, ferrite core inductor and a ceramic resistor, despite all these cost-cutting measures these speakers exhibit such coherency and dynamic prowess. I can’t help thinking – what if the crossover boards are out of the enclosures where the constantly changing pressure, relentlessly pounding airwaves and mechanical vibrations are taking their lot, what if parts of higher quality are used, foil instead of electrolytic capacitors, air core instead of ferrite core inductor and metal-oxide instead of ceramic resistor, what if … I simply cannot stop myself, I know it is not reviewers job poking his nose, and especially modifying a component sent for review is a heresy, it is something one should never do, but I can’t stop myself, it’s that passion that burns and tells me these speakers have an enormous potential that should be released. I ought to give them what they deserve and in return they might allow me to have a glimpse of heaven.

Bringing the crossovers out

As I already said I couldn’t resist the temptation to try the sonic outcome of just one simple move – bringing the existing crossover boards out of the enclosures. Generally speaking putting the crossover board within the enclosure is a serious compromise dictated by production costs and convenience considerations. For that experiment I decided to use the same Kimber 4PR bi-wired set of cables I already used for a week. What I did was to unsolder the boards from the binding posts and the speaker driver’s cables and then solder the speaker driver’s cables directly to the binding posts. Then I soldered the Kimber cables to the crossover boards at the respective points (the filtered out signals for the twitter and woofer) and replaced the original short pieces of cable that used to connect the crossover’s inputs with the binding posts while maintaining the bi-wired configuration and taking care of the correct polarity. The only difference now was that the crossover boards were out of the enclosures, closer to the amplifier and further away from the speakers.

Audio Note AX-Two crossover board

I remember the first listen with the outboard crossovers as if it was yesterday. It was Chet Baker & Paul Bley collaboration Diane (LP, SteepleChase SCS 1207). I was simply shocked by the effect of this relatively simple tweak. The tone of the Baker’s trumpet was shimmering in the air with real brassy sheen while the deep bass notes produced by Bley’s piano, rich and dense with harmonics, were unfolding in the space around, an electrifying, goose bumps experience. I instantly noticed the gain in clarity and immediacy, it was simply scary. I couldn’t stop to listen before the needle hit the lead-out groove, it was mesmerizing. I got so excited that few hours later I was writing an email to my pal Oscar telling him about the outcome of the experiment:

I just want to tell you that I brought the crossovers out of the enclosures, this was the only change I made, using the same Kimber double run cable I was using lately. I am speechless, these speakers are performing now on a level I didn’t think it’s possible, amazing stuff. It turns out something I suspected a long time ago is true – bringing the crossovers out gains a massive improvement, bigger than simply changing capacitors or wires.

Getting rid of the printed boards

Once you get on that road it is hard to stop, the gain in purity and immediacy is addictive, it brings you closer to the artist’s intentions. The interaction between both musicians became so palpable and transparent that one can get sense of every hesitation they encounter, every uncertainty, of every shade of expression. So after a few weeks of enjoyment I decided to move the crossover elements out of the original boards and by using point-to-point soldering to eliminate the printed circuit paths. I kept the original coils and one of the capacitors, but the rest I replaced with cheap film ones I had at hand while the ceramic resistor was replaced with a metal-oxide equivalent. I was anticipating some improvement to come but this time the effect was even bigger than expected. The music seemed to flow unbridled as if liberated, it was like a dam on the river has burst open and the stream was rushing with all its energy, the last obstacle was out of the way. Believe it or not but I had to reduce the loudness which now I perceived increased. I can’t tell why this happened and how exactly the dispense of the printed board affects the perceived loudness but I have the feeling that the speakers now are slightly more efficient.

DIY outboard crossover for Audio Note AX-Two loudspeaker

Honestly the AX-Two outboard crossover project exceeded all my expectations. I enjoy these crossovers for a few weeks now and they give me a glimpse of what AX-Two are really capable of. I am definitely going to continue this experiment and plan as a next step to replace the ferrite core coil and get rid of the last electrolytic capacitor. Afterwards I may try some better capacitors and cabling, finalize the layout and replace the provisional boards with dedicated ones.

Listening impressions

Balanced is the most accurate adjective I can come up with trying to describe Audio Note AX-Two. These speakers do not favor any particular genre but do equally well with acoustic or electronic music, vocal or instrumental, natural or studio recordings. Listening to Jan Garbarek’s classic I took up the runes (LP, ECM 1419) I am taken on a journey into fantastic landscapes created by Bugge Wesseltoft’s synthesizer, peaks and valleys traversed by Eberhard Weber’s unexpected and bold bass lines, rays of sunlight peeking through the clouds radiated out of Garbarek’s saxophone. The sound is spacious and densely saturated, very solid and liquid at the same time.

To check how AX-Two are dealing with human vocal range I give the Kenny Wheeler’s suite Mirrors (LP, Gearbox GB1513) a spin. Featuring Norma Winstone backed by the London Vocal Project this is a contemporary record conducted in the best analog traditions using Studer tape machines, vintage Haeco Scully cutting lathe with Westrex heads and all Audio Note monitoring equipment. Norma’s voice, soloing or backed by the 24 voice chorus, is as spooky present as I ever heard from a record. There is an unmistakable warmth radiated from a living being that only the best records played under the best conditions could deliver. I am enthralled, it is so charming and comforting to listen to this record, and it fully shows what a properly made vinyl has to offer.

Audio Note audio system with DIY outboard crossovers

Conclusion

AX-Two are exceptional speakers. Especially with the outboard crossovers they deliver on par with some of the best stand-mounted transducers I have ever encountered at a fraction of their price. Their relatively high sensitivity of 90 dB (2.83 V, 1 m), benign phase angle characteristics and 6 Ohms impedance make them perfect partner for low-power tube amplifiers. Featuring pair of posts per speaker driver the terminal plate allows for bi-wiring which I find beneficial. When bi-wired these speakers maintain the seamless integration of both driver units while bringing up some additional clarity and composure to the presentation. Power handling is pretty good and there is plenty of headroom before they start to compress dynamics which in fact I have never experienced. They are capable of playing very loud while keeping the whole picture intact. They keep the balance also at very low listening levels which make them perfect companion for the late hours when the neighbors are asleep. All in all an excellent speaker that has become my reference.

Thank you for stopping by and
Happy New Year!

23 thoughts on “Audio Note AX-Two stand-mounted loudspeakers”

  1. Hi
    I am listening to my AX Two as i read your blog. Fantastic results you got there! Have you changed the remaining caps and which ones do you use? I must try that mod! Thanks for a very interesting read!😃

    1. Hi Fredrik,

      Thanks, I am glad you liked the read and got inspired!

      You should definitely try the outboard crossovers for they will give you an idea of what AX-Two are really capable of. Better keep the original crossover boards intact and build new ones from scratch. This way you will be able to restore the speakers to the original state if you decide to sell them later, which I really doubt. The parts used in the original crossovers are of basic quality and it doesn’t make sense to reuse them. Here is the schematic of the original network you can base your new build on. You can start with any budget foil capacitors first and later on switch to some more expensive ones. I usually use MKP foil capacitors from Audaphon during the prototyping stage, but for the final build I would go for Mundorf MCap Supreme. Two of the capacitors used in the original boards have values of 6µF and 12µF that are not standard, but you can use 5.6µF and 10µF instead. This will shift the tonal balance slightly, but later on you can always add some small caps in parallel to achieve the precise values. The 1.33mH coil in the low pass-filter has also non-standard value, but you can use 1.5mH one (any air core coil with wire diameter between 1.2mm and 1.4mm would do) and unwind few turns until it reaches an inductance value of around 1.35mH. For this you will need an LCR meter that doesn’t need to be expensive. Another alternative is to use two standard 0.68mH coils connected in series (something like this), which will bring the total inductance to 1.36mH and sounds pretty good. The 0.33mH coil in the high-pass filter is made out of 0.7mm wire and has a standard value. Hope this helps.

      Regards,
      Dimitar

  2. The original XO shows 4 caps, yet your XO shows 3. Can you explain? Were two of these caps on the original XO summed to form one of the values on your hand-drawn XO? Please advise.

    Thanks,
    Steven

    1. Yes Steven, two connected in parallel 6µF capacitors are used in the original crossover to form the single 12µF cap shown on the schematic.

      Cheers,
      Dimitar

  3. Hi Dimitar,
    I am most impressed with your Blog and I now own a nice pair of AX Twos. Their sound is wonderful and most af all coherent. The best result I surprisingly achieved with a cheap mm pick-up (Audio Technica ATVM 95-E) on my rebuild Lenco L75, which seems to strenghten the coherency even further (I also own a Rega Apheta and a DL-103, but the Audio Technica is more to my liking). My problem arose as I bought a cheap pair of Dali 104, took them apart, braced the inside and damped them with felt and bitumen. I brought the XO out and raised the speaker 12 cm. They sound different than the AX Two (of course!) even w/ the same drivers and a similar (?)tweeter. But they sound great too and have some of the same qualities (probably due to the Vifa c17). They have more space and presence than the AX Two. But, but, but… They lack the coherency and therefor I can´t forget the Audio Notes. Do you have any idea how to make the Dalis more coherent? Is the cabinet too large? I know, that you can´t turn a speaker into something it is not, but still, it´s a fun project and I´m curious if you have anything to say to this.

    1. Hi Peter,

      Thank you! Sounds like a very interesting project you ventured into. As I understand, you have increased the speaker’s volume by making it taller. This I think will alter the group delay response and should be addressed in the crossover. You can play around with the values of components in some systematic way but I doubt this will work out. You can also decrease the speaker volume to the initial state by placing some bags with sand inside the enclosure. This will tell you if the deterioration in coherency you have noticed is due to the increased volume or the reason is something else.

      Generally I would not expect a 2.5-way speaker to sound as coherent as a 2-way speaker; the same way I would not expect a 2-way speaker to sound as coherent as a single driver speaker. That’s the reason why Audio Note is not offering a 3-way speaker – because to integrate 3 drivers seamlessly is an impossible task. What they have accomplished with AX-Two in terms of coherency is nothing short of amazing, so no wonder that Dali 104 does not sound as integrated.

      Have you used the PTP kit to rebuild the Lenco or you keep the original top plate? I just recently stumbled upon Clinamen’s hot-rodded Lenco and I am stunned, I think this might easily be the ultimate Lenco.

      Cheers,
      Dimitar

  4. Hello,
    great review! So great that I grabbed a couple of these speakers and they are really something special.
    One question: in your tests, why is the optimal distance from the back wall?
    Thank you!

    1. Hello Sergio,
      Thanks for the kind words. I am glad you like these speakers, they are fantastic. I keep them really close to the wall behind – 3 to 5 centimetres away, wide apart and aimed at the listening position.

      Best Regards,
      Dimitar

      1. Thank you! Andy Whittle, the designer, wrote me suggesting to keep like 20 cm from behind wall and toed in about 20 degrees. Going to experiment a little:). I guess everything is very room depending. I am going to experiment a little and post here my findings!

        Best regards

        Sergio

        1. Thank you too! I am glad you are willing to share your experience with us. Sure, speaker positioning depends on the room acoustics and the associated equipment, but it is also a matter of personal preference and taste. At the beginning I used to keep them more then 10 centimetres away from the wall but with the time my tastes evolved and today I prefer them really close to the wall behind. I am sure they might sound quite appealing when placed further away from the wall but in the long run I prefer them closer to it.

          Best regards,
          Dimitar

  5. Hello Dimitar,
    I really understand your point. Actually close to the wall they do something really well. Can I ask a couple of questions?
    When you measure 3-5 cm from the wall you measure from the corner of the speaker nearest to the wall or from the center of the rear of the speaker?
    And finally, the distance between speakers is equal to the one from the listening point?
    Really thank you!
    Sergio

    1. Hello Sergio,
      yes, I mean the distance between the nearest corner and the wall, currently it measures 4.5 centimetres. My room is not well suited for equilateral triangle arrangement, so the distance between the speakers is roughly 3 metres while the distance from each speaker to the listening position is about 4.5 meters. It is still a very engaging presentation that works well for me.

      Happy listening,
      Dimitar

  6. Hi
    I’ve read your articles with interest numerous times.
    In the meantime having upgraded my AX TWO’s with better cabling and a small adjuster cap parallel with the 2 tweter caps.
    The idea of removing their x-overs from their cabs intrigue me.
    I have later learned what initially appeared to be a step forward with prolonged listening proved not to be.
    Does the same go for the sole removal of the TWO’s crossovers?
    If this also belong to your rejected suggestions.
    I won’t bother with “all” the hassle😄
    Have a nice day
    Henrik

    1. Hi Henrik,
      Glad to hear you are enjoying your AX-Two’s. Bringing the crossovers out of the speaker’s enclosure is a great way to improve their performance and there is no going back. Rebuilding them with better components and point-to-point wiring will boost the performance even further. I don’t know where you have learnt that with prolonged listening the improvement proved not to be an improvement, but it is definitely not on this website because I have never mentioned it. What turned out not to be an improvement in the long run was the series crossover version I developed as an alternative to the original parallel one. So stick to the original circuit if you decide to rebuild.

      Best Regards,
      Dimitar

      1. Hi Dimitar
        Thanks for your kind reply.
        I’ve written this the other day.
        But something apparently went wrong, and my initial inquiry was posted again twice. Sorry for that.
        – What I’d like to ask you is; did you substitute the original inductors too?
        Someone “in the know” told to me NOT to touch the inductors, when I upgraded a pair of Type K’s a couple of years ago.
        So I only did the capacitors then.
        (Their intern cables had already been changed to SPx long long time ago)
        If I really really like my AX TWO’s after their Xovers have been brought out.
        I might do the same to my K’s xovers -although it’ll take some more, not being as easily removed as the AX’s.
        Thanks again for taking your time to answer, much appreciated!
        Kind regards
        Hans-Henrik

  7. Ooops sorry!
    Dear Dimitar
    Thanks ever so much for coming back to me, and eventualy correcting my misconceptions.
    Must be too long time ago since I read about your different experiments.
    A case of false memory on my behalf.
    Sorry!
    I love my beautiful AX TWO’s dearly for what they bring:
    Lightning speed and unparallelled openness – compared to my other AN speakers (upscale K’s and E’s)
    So will get cracking shortly.
    Can’t wait to hear what it’ll bring
    One last thing:
    Have you experienced any discrepancies SQ-wise between the factory supplied inductors and your upgraded ones?
    (Or did you finally stick to upgrading capacitors only?)
    I ask this specifically because someone “in the know” told me NOT to touch/ substitute the original inductors.
    Telling me the ones that did. Eventually reverted to the speakers originally delivered inductors.
    With my TWO’s already playing rather sublime with my initial upgrades made to them (AN silver internal leads and a very small by pass/ adjuster cap on the D19s caps) I reckon I’ll be in for a treat, once they’re finished!
    Thanks again for your kind reply
    Hans-Henrik

    1. Hi Hans-Henrik,

      no need for apologies. You brought a good point here regarding the inductors and I am glad you asked this question because this is topic often overlooked by DIYers. I must say you are absolutely right, if someone expects just to drop in a replacement coil of the same inductance as the original without paying closer attention to its DC resistance he is up for surprise, the speaker will sound nothing like the original. So the DC resistance of a coil is of crucial importance and we are talking here about resistance value close to a hundredth of an Ohm which is also really hard to measure. For example the original 1.33mH inductor in the low pass filter has DC resistance of approximately 0.50 Ohms and if you substitute it with a coil having DC resistance of let say 0.45 Ohms this will alter the speaker’s performance quite noticeably. One might say it is nothing much to worry about – some 0.05 Ohm of resistance – but seeing it as a percent of the total DC resistance of the coil we are talking about 10% difference from the nominal value and that is a lot. Regarding the DC resistance of the replacement coil one should really stay within the 5% tolerance as a maximum allowed deviation. And even then, small adjustments of the rest of the crossover’s components might be necessary to compensate for that deviation. So yeah, if you are not using the original coils, even if you try to match the DC resistance as closely as possible, it is quite probable that you’ll need to make some additional adjustments in order to match the response of the original.

      I must say I have tried dozens of coils having the same inductance but just slightly different DC resistance (this depends on the wire diameter and the geometry – core diameter and winding height) before I have found the right ones, and it was a long process but I can say it was well worth. You can see the coils that I am using here – low pass, high pass Although these coils have DC resistance very close to the original ones I needed to adjust the high-pass crossover section to compensate for the slight deviation of the coil’s DC resistance and to fine tune the speakers’ response to my room. I have upped the attenuation resistor from 4.7 Ohms (original) to 4.8 Ohms and the second high-pass cap from 12μF to 12.47μF in order to compensate for the slight DC resistance deviation of the new coils. Here you can see a pic of the crossover – top view and here the underside where you can see the adjustment resistor and the small .47μF adjuster cap – bottom view. You can see that I have two 10 Ohms resistors in parallel which make for a total of 5 Ohms resistance and then with a third resistor in parallel having a value somewhere between 100 and 150 Ohms one can fine tune the speakers to his own preference. I am using a 120 Ohm adjuster resistor there you can see at the underside. One might think that going from 4.7 Ohms attenuation resistor to 4.8 Ohms is nothing but I can assure you that even smaller increments of the vicinity of 0.05 Ohms have tremendous impact on the speaker’s response and dynamic behavior because it affects not just the twitter attenuation level but the system’s impedance and attenuation curves. All the rest stays as in the original – I am using a 1.8μF in parallel with a 1.5μF cap to get the 3.3μF value in the high-pass section (you can see them next to the big 12μF cap) and a 3.3μF in parallel to a 2.7μF cap to get the 6μF value in the low-pass section. These two caps – the first in the high-pass and the one in the low-pass sections should stay so.

      So my advice if you decide to go for external crossovers, which I highly recommend, is to forget about modifying the existing crossovers, but build new ones from scratch. You can keep the original crossovers as a reference and bring them first outside, just in order to assess the negative impact cabinet resonances and air pressure variations have on their performance. Then you can source the necessary parts, build new ones and substitute the originals. You can fine tune the crossovers afterwards by varying the values of the attenuation resistor and the second high-pass cap.

      Hope this helps.

      Cheers,
      Dimitar

  8. Dear Dimitar
    Thanks for your kind and thorough reply and explanation.
    Very much appreciated!
    Sorry for coming back to you so late, due to a rather late summer vacation.

    – I’ll take your recommendations in small increments in order better to hear what happens as I go along.
    With regard to all the hassle nailing just the right resistor value for the D19 tweeters I’m going to use what AN UK uses for their E, J and K speakers:
    A wirewound adjustable resistor.
    Found mine at “digikey.com” on line.
    (I think they are 10 ohm BROWN colored types – the color will help you to more easily sort out the “right” type for the job – as used by Snell as well)
    This type – besides sounding real great – makes you able to fine adjust the value with the utmost precison.
    I think I’ ll start out going back an forth setting the resistor value by ear, to see how it correlates to the known value – and the value you mention.
    And see what happens.
    The adjustability and the fact thar the crossovers are now out of the boxes and readily accessible, will make it a breeze to do so.
    Thanks again for taking your time to answer me!
    I’ll report back when I get going and come up with some results.
    Till then
    My best regards
    Hans-Henrik

    1. Hi Hans-Henrik,

      You are welcome. That’s a very useful information regarding the adjustable wire wound resistor used in some of the AN speakers I wasn’t aware of. If I knew it I might have used adjustable resistor instead of the paralleled Welwyn ones which are also very good. Looking forward to hear more from you and your findings as you progress with the crossover project.

      All the best,
      Dimitar

      1. Dear Dimitar
        Thanks for your kind and thorough reply and explanation.
        Very much appreciated!
        Sorry for coming back to you so late, due to a rather late summer vacation.

        – I’ll take your recommendations in small increments in order better to hear what happens as I go along.
        With regard to all the hassle nailing just the right resistor value for the D19 tweeters I’m going to use what AN UK uses for their E, J and K speakers:
        A wirewound adjustable resistor.
        Found mine at “digikey.com” on line.
        (I think they are 10 ohm BROWN colored types – the color will help you to more easily sort out the “right” type for the job – as used by Snell as well)
        This type – besides sounding real great – makes you able to fine adjust the value with the utmost precison.
        I think I’ ll start out going back an forth setting the resistor value by ear, to see how it correlates to the known value – and the value you mention.
        And see what happens.
        The adjustability and the fact thar the crossovers are now out of the boxes and readily accessible, will make it a breeze to do so.
        Thanks again for taking your time to answer me!
        I’ll report back when I get going and come up with some results.
        Till then
        My best regards
        Hans-Henrik

  9. Sorry for fumbling around – again🙈!
    Hi Dimitar
    Finished work last week removing the xovers and soldering my AN SPx internal wires directly to the boxes binding posts.
    Next I bought two small plastic boxes the size of the factory crossovers lendng me the opportunity to have a place to mount 2 sets of new binding post for my Kondo KSL SPc bi wiring speaker cable going to the AX TWO’s. And 4 short runs of AN SPx per side going to my AN Cobra’s speaker binding posts.
    Bummer!! –
    A big disappointment met me:
    Sound coming from the left bass/ mid only. Nothing else…
    Immediately thinking I’d somehow messed up the different connections.
    I left the project for later.
    Later being the day before yesterday.
    After going through both crossovers again finding them to be correctly terminated, I finally turned my attention to the other cables in my set up.
    Realizing I’d somehow f..ked around to much with an IC and one of the bi wiring cables, thus barking up the wrong tree.
    After correcting the bad connections Heureka!
    Finally sound coming from ALL 4 driveunits!!
    And what a sound!
    What first springs to mind; is an elevated sense of perfect TIMING.
    Crystal clear with a very transparent and very clean soundstage further freed from the cabinets.
    With a heightened sense of dynamic contrast, sounding so much more free, distinct and delineated, from only freeing the cabinets of their internal crossovers. The internal AN SPx loom as well as a tiny adjuster cap following over from the previous solution.
    So before even making further changes a very worth while job of just freeing the cabs of their crossovers.
    It might as well be a bone having them just beside my amp with treble and bass/ mids being divided and sent along their separate speaker cables.
    Instead of both bi wiring cables sharing the whole signal up until the AX TWO’s speaker binding posts.
    I don’t know all this correlates with your own findings at this stage?
    I’ll leave it at that for a while.
    Before making upgrades to the xovers themselves.
    Thanks for inspiring me to take the plunge.
    I’ll come back if and when I have done further work on my TWOs
    Thanks Dimitar
    Best regards
    Hans-Henrik

    Hans-Henrik

    1. P.S.
      Or I could just boil it down and make an analogy:
      Bringing the xovers outside the speaker cabinets is akin to taking your prized handheld reflex camera, and putting it on a tripod before shooting
      Cheers
      Hans-Henrik

      1. Hi Hans-Henrik,

        Thanks for the nice feedback!
        I am very glad you enjoy the positive effects of bringing the crossovers out of the speakers’ enclosures.
        I prefer them single-wired with the crossovers placed closer to the speakers, that way the total length of cable used is at minimum and to my ears gives the best overall performance. Of course your preference may vary.
        I think your tripod analogy is spot on.

        Happy listening!

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