Building loudspeakers is not like throwing out requests at a concert, even if the obvious goal is to enjoy a lifelike concert once they’re finished. Quickly putting together a nice-sounding little two-way speaker with a #17 bass and tweeter is a full day’s work, and 85 dB/ 2.83 V is the general rule. Even a three-way speaker with similar sound pressure and a little more in the way of dynamics isn’t witchcraft; but live music depends on the volume level, the lively sound that slams every “P” blasted into the microphone and every bass drumbeat right into your ears. Creating that effect with amplifiers alone requires wattage in the high three figures, along with correspondingly high-capacity voice coils. As a result, a capacity level well above the 90 dB line, even without a horn reheater, turns out to be the path we have long been seeking. We undertook some tentative trials with the Power series, which consists of no fewer than two examples and whose success could be described as sporadic. Part of this was probably due to the PA chassis in the 225 and the large tweeter horn in the 220, both of which are uncommon for normal living areas and are both concessions to the task assigned to the boxes; still, regardless of the reason, not the ideal compromise for a shared living room. The hi-fi basses in the one and the magnetostat in the other could have been a solution, but it didn’t work at first without a GRT 175 A; later on, the obsolete basses made it unnecessary. So until now, all we had was a dream – which now can become a reality. With the Gradient Axis speakers and the Fountek ribbon, we finally have the appropriate ingredients to create a living-room-compatible power box.
We had already gathered some experience with the combination of the Gradient Axis and the Fountek ribbon in the Axis 34 Neo, which was already almost in the target range with just under 90 dB/ 2.83V. We were almost forced to try it out with the AXT-08, knowing full well that we would be earning criticism from theory-obsessed forum users (not ours, of course). An eight-incher can’t work with a two-way concept – it bundles the sound too early and has to hand over the reins to a suitable compatriot by 800 Hz at the latest. In addition, because of the volume level and the simpler two-way crossover, we also committed the sacrilege of a D’Appolito look, choosing the high Neo 2.0 CD ribbon as a partner because it can barely handle a separation below 2.5 kHz. However, there may have been an unconscious reason that we needed almost six months to hit on the idea of the eight-inchers. After all, even for us there are a couple of things that we wouldn’t voluntarily try under normal circumstances. Where this gets us in practice, you can see by the end of this report. In any case, we didn’t have to worry about our ears at any point.
Still, at least within the report, let’s continue along the normal paths, presenting the data for the Neo 2.0 CD – which has not been published in the magazine before – in the usual brief format. The data for the AXT-08 can be found in the chassis test in the here.
Neo 2.0 CD
Measurements as a zip-file
|Membrane:||Aluminum foil||Magnetg shielding:||no|
|Voice coil:||none||Pole piece hole:||no|
|Coil height:||none||Monting holes:||4|
|Pole piece thickness:||none||Outside diameter:||85 x 165 mm|
|Linear excursion:||not given||Installation opening:||61 x 144 mm|
|effective membrane surface:||9,6 mm²||Installation depth||74 mm|
|Magnet:||Neodymium||Milling depth:||5 mm|
In place of self-derived parameters, this time we are using the manufacturer’s information as an exception. In order to get at all of the data ourselves, we would have had to take things into our own hands and open the fancy outer casing. For reasons that are hopefully understandable, we couldn’t make ourselves do that.
|Frequency response and phase ||Impedance||Frequency response under 0/ 30/ 60°°|
|Distortion for 90 dB||Step response||Waterfall|
Now that we had established what needed to go into the boxes, all that was missing was the right cabinet size. LSPCad told us that just under 20 liters per bass would be ideal. However, since this otherwise very reliable simulation program had made quite a few mistakes with the Axis 85, we decided not to listen to it, and we clicked around in the corresponding window until we were happy with the simulated curve. When our gaze fell back on “Volume,” it showed a whopping 40. A bass above the Neo 2.0 CD, which in turn was at ear level, required an outer height of 1.2 meters with an enclosed space measuring 24 x 30.7 cm. We quickly added a few reinforcements and a board that brought the depth of the reflex channel, including the front, to 15.8 cm to the SketchUp drawing, and the simple assembly plan was created within just a few minutes.
This time we took our wood list in to Hornbach – there is a large selection of hardware stores in our area. Coincidentally, another customer was just having some multiplex cut to size that had a nicer finish on one side than we had ever seen before. The surface was very similar to alder, but it didn’t have the same reddish color. “Does your multiplex always look like that?” we asked the cutter, who immediately apologized and pointed out the “normal” birch side. “You won’t see the other color when it’s on the inside,” he said, in an attempt to placate us. Ah well, beauty is in the eye of the beholder, and we had no objections at all to knotholes and a couple of small cracks in the outer layer. What we did object to, on the other hand, was the slight distortion in the boards, possibly caused by the different kinds of wood but more likely because they had been stored flat on narrow slats on the hardware-store shelf. Nothing is free, according to the hard and fast rule of physics, so we immediately started thinking about how we could easily glue the boards together at a right angle anyway. In the Wolfcraft department, we found a dowelling jig for 20 euros that was very easy to use – which isn’t always the case with those kinds of devices. We could have driven home at that point, fully satisfied, but there was still a gnawing doubt. Dowelling requires perfectly cut wood, and we didn’t want to assume that was the case. While the first three boards can usually be coaxed into shape without too much trouble, the fun usually stops by the time you get to the last board because the cut is only precise down to the millimeter. So that was a no, then? Well, where there’s a will, there’s a way! Maybe we could get some help from those practical corner clamps, sold in packs of two for just under 8 euros? Now we had a plan of attack in mind. The following photos prove that we weren’t too far off.
The boards and tools were assembled on the workbench before gluing. Counter to the “normal” procedure, we cut out the holes in the fronts ahead of time.
The provided drill-depth stop is set up so that the drill bit sticks out of the dowelling jig by 16 mm. We used it to drill two holes in the long cut edge of the lid, and inserted the dowels. The lid was placed on the side board with the help of the dowelling jig, which formed a guide for drilling the opposite holes in the exact right position. While drilling, we were looking at the outside of the lid and the inside of the side board. A view of our new tool:
Of the three drill guides, measuring 6, 8 and 10 mm, we chose the smallest one for the dowelling work. The knob on top rotates and allows you to set the distance to the outer edge of the board. The corresponding stop can be seen in the second picture above the drilling guides. There are practical grooves underneath them so that the matching dowels can stick into the opposite board without wiggling. All very easy.
Joint glue is applied to the dowel holes and to the cut edges of the lid, which can go on right away. Now it’s our solid rock in the storm – all of the other boards can hang on to it for dear life, literally as it turns out.
What began with the usual glue on the cut edges now continues with corner brackets between the lid and the rear wall. That not only creates a gap-free connection, but also guarantees a right angle. We also took a self-explanatory picture of the clamps.
The front and the reflex channel followed, with the back end defined by the centimeter measurement.
Once the reinforcements were marked, the glue had dried enough for us to take off the clamps and use them elsewhere. The reason for all the trouble we took in building the Axis 220 Neo is only clear once you see the following picture:
The back wall was a little bit distorted, nothing terrible in and of itself, but the floor would have lifted up at the front bottom if it had been flush with the back. Now we were able to pull it straight at the top with a clamp, and despite working quickly, we ended up with a clean floor line along all the edges.
After 20 minutes, we removed all of the tools and applied glue to the cut edges so that they would stick permanently to the second side. We also used two tie-down strips to press the boards together, eliminating all of those gaps that slightly bent boards tend to have. When we continued our work on the boxes in the basement the next morning, we basically only needed to sand off some glue residue. Three layers of hard-wax oil, sanding by hand between the layers, gave the boxes a final shine and strongly emphasized the color of the wood, which had seemed flat in its natural state. This was what we had pictured. All that was missing was putting insulation into the boxes, connecting the chassis elements to the outside world with a long cord through the reflex opening, and we were ready to start developing the crossover. We had already connected the two basses in parallel before screwing them on – that’s what you do with this kind of arrangement – so they had a shared cord. For the measurements, we placed a box at the measuring station that raised the tweeter about 1.3 meters above the floor. We put the microphone in the usual centered position right in front of it.
For starters, we had the two basses perform a duet made up of sine waves that revealed their strength as a team – in other words, they pushed a decent amount of sound pressure into the measurement chamber. Well, okay, most of it wasn’t really useful, since the volume increase above 400 Hz had to be sacrificed for the sake of a smooth frequency response (red). That was handled by a traditional third-order filter without any special features – a large coil in the front, a parallel electrolytic capacitor and a small coil at the end in front of the AXT-08 (blue). The tweeter was almost as frugal, but needed to be made a little bit quieter too. There were three possible spots for the necessary resistor, but it did best behind the wiring for the first capacitor and coil, and before the second C. A clean summary resulted when I set up the branches with reverse polarity. An impedance correction was needed, of course, so we used an electrolytic capacitor, a small air coil and a 10-watt Mox to connect a suction circuit parallel to the crossover input.
This is also a good opportunity to say a few words about our grossly undervalued pricing policy. Almost no one has noticed, let alone discussed the fact that a non-cyclical process has taken place at Intertechnik over the past few years. While all around us things have been getting more expensive and the same packages have less and less content, while raw-material prices have been rising along with the cost of living by up to 3% a year, here in the shadow of the Cologne Cathedral we have dropped our prices several times. That doesn’t just mean the components – most of the chassis elements and certainly all of the assembly kits are now cheaper than they were years ago. The Fountek is an especially good example. Since being distributed by Intertechnik, the prices for end customers have been nearly cut in half. (Just to point out, for fun: if you want, you can still buy the ribbons online at the old price, just with a different brand sticker on them.) Naturally, this isn’t a selfless act of Good Samaritanism, but the logical result of moving away from obsolete retail structures. Manufacturers, wholesalers and end retailers were passing on their none-too-small margins to the purchase price paid by the end customer. When we broke away from this nonsense, which is after all anachronistic in the internet age, we met with a lot of criticism from retailers who felt cheated of their unjust rewards for work they hadn’t performed. In their cobbled-together online shops, where the only motivating factor other than the price was some vague gazette blather about the parts, the kind of advice you used to get at brick and mortar stores was nowhere to be found. Instead of continuing to fill the pocketbooks of these unnecessary “boxmongers,” we set up the magazine, which gives customers much more information. That means consumers who don’t like making blind purchases or settling for shrinking violets can find not only assembly reports, but also advice from other people in the forum in addition to the seller. Even those who don’t buy anything will hopefully enjoy reading it. But caution is advised: constant exposure can lead to infection!
|Frequency response and phase||Impedance||Frequency response under 0/ 30/ 60°|
|KDsitortion for 90 dB||Step response||Waterfall|
We were in our element during the final listening test, where the Axis 220 Neo had a chance to show off its great strengths. Plenty of membrane surface and volume are the most important elements for playing music by rock bands from the ’60s and ’70s, whose music didn’t just consist of a couple of boring verses with three guitar chords plunked between them. In the absence of a tube amp with 2 x 12 to 18 watts, we applied our experience with KT 88 to the boxes, as usual. Now we had the 60 watts of power, but you don’t need to turn it up all the way just because it doesn’t sound restrained before that point. The volume knob was at 9 o’clock when we resurrected the zeitgeist of the hippie youth that one or two of us still belonged to in August of 1969, with my black Woodstock album. The “Star-Spangled Banner,” Jimmy Hendrix’ legendary take on the American national anthem, not exactly well recorded, but still impressive after more than 40 years, instantly turned our listening room into Max Yasgur’s farm where the festival famously took place – this despite a lifetime of saying no to drugs. No, we’re not going to tell you what we talked about with Mr. Hendrix when he suddenly showed up in our living room. That would be a bit of an exaggeration, and more worthy of an entertainment magazine, or in our case maybe unworthy. Once we had started, we could hardly skip over Alvin Lee and “I’m Going Home” – as we’ve often said before, the best rock and roll of all time. Still, music with better recording values makes it easier to talk about the quality of our boxes. We’ll leave it up to you to decide which one is more fun.
So after this wonderfully emotional warmup, we went back to the familiar old ways to measure their notes rather than their head-bobbing factor. Everyone’s tired of hearing it, but every other visitor requests it: “Hotel California” with that famous bass drum. It was short and dry, but with a powerful “dub” and a rolling echo from the drum, once the guitars and the audience lit up the width and depth of the stage. In “Keith Don’t Go,” we heard the wonderful fine resolution of the almost weightless ribbon in its full glory, and the interactions between the large basses left nothing to be desired, whatever all the theory might have said. The Axis 220 Neo cannot be accused of tonal colorations, sharpness or a lack of dynamics; the sweet spot wasn’t limited to a small section of the familiar sofa. The somewhat spectacular approach, with a snappy but not too deep bass, naturally requires some small trade-offs for large orchestras and classical music. Still, people whose musical taste tends in that direction are rarely looking for capacity from narrow boxes. The intended task of the Axis 220 Neo was to bring lifelike music into the listening room, even if the amplifier is a bit of a Scrooge in terms of wattage. And it does that beautifully.
Loudspeaker Axis 220 Neo
|Chassis||Gradient 2 x AXT-08||Wood list in 18 mm MDF|
|Fountek Neo 2.0 CD||or multiplex per box:|
|Sales and||Intertechnik||120,0 x 34,5 (2x) sides|
|Construction:||24,0 x 34,5 (2x) lid/ floor|
|Function principle||Bass reflex||24,0 x 116,4 (1x) back wall|
|Nominal impedance||4 Ohm||24,0 x 111,4 (1x) front|
|Terminal||T 105 MSAU||24,0 x 14,0 (1x) reflex channel board|
|Damping/insulation||7 bags Sonofil||24,0 x 10,0 (4x) reinforcement|
|Approx. cost per box:||Milling depth for all speakers: 5 mm|
|Assembly kit without wood||275,-|
|Wood cutting 18 mm MDF||30,-|