Long gone are the days when it was enough to create a loudspeaker that was purely meant for listening to music. SB 417 and the Little Princess are examples of well-intended projects – thanks to users with other ideas, though, they quickly advanced into the viewing arena too, in other words home theater. No, we’re not sorry about it – it’s not like our opinion is a standard that everyone has to follow without exceptions. We believe everyone should have the freedom to make their own decisions – we even expect it from them, as we have often written in our forum. The latest “victim” of this capriciousness is called the Audible 34, which was really intended for people listening to low-watt tubes. But to be perfectly honest, dynamic, high-efficiency boxes are also right at home when it comes to watching movies. So it only makes sense to introduce the matching rear speakers now, too. No one will be surprised that they are called the Audible 17, and this time they are being touted the other way around: as shelf loudspeakers that also work for music.
Loud compact boxes that also have an AVR-friendly 8-ohm impedance are fairly rare creatures these days. They were simply forgotten on the market because there was plenty of output available – even the smallest speakers were being forced down to the deep bass range, which naturally cost them in terms of volume and dynamics. It’s no problem, people figured, we’ll just step on the gas and it’ll be fine. What’s always left out here is the ability to pack in more dBs between the quiet and loud passages, but no matter, compressed music with a dynamic range of at most five to seven dBs doesn’t need it. This lack isn’t even relevant for watching movies – after all, we have a remote control that can easily adjust for thin quiet sounds and screaming loud sounds as needed. The only problem is when you’re supposed to be hearing both at once. That’s where the “modern” loudspeaker quickly reaches its limits, while the loud AXPs are in their element. To make a long story short, the Audible 17 is the perfect partner for every movie buff.
The LSPCad simulation for the AXP 06 asked us to compress roughly 16 liters of air into a wooden container, connected to the outside by a channel 16.5 cm long with a 38 cm² opening. This produced a box with internal dimensions of 34.8 (H) x 19 (W) x 24.2 (D). At the hardware store, we found a stack of 21-mm-thick Jerusalem pine to match the outside of the Audible 34, at a price of 10 euros per m². The nice man running the saw intentionally overlooked the unfriendly sign telling us that the 3 m² boards needed to be sold whole and taken home without being cut to size. He turned them into four car-friendly pieces for us, which our CNC router could handle from there. We didn’t take any pictures of the assembly process, so the assembly plan will have to do this time. The SketchUp drawing may also be helpful if something is unclear while you are gluing the eight boards together.
We don’t need any data sheets for the components AXP 06 and GAM 100 here, since the internet makes it very easy to look them up. A click on the chassis name will take interested readers directly to the corresponding individual tests. Since that means we are missing the usual assembly and data sheet passages to fill up this page, we will make a virtue out of necessity this time and give you a chance to focus on the crossover development step for a change. It started with stuffing a bag of Sonofil into the finished housing and screwing in the chassis elements so they could be supplied with components from the outside using a homemade biwiring socket. To do this, I drilled a hole in the T 105 and ran an additional cable to the tweeter while the bass was connected with the existing clamps. Hot glue made the hole air-tight, since we didn’t want the box to start whistling merrily during the bass measurements. We started with the bass, which was attached directly to the measurement amplifier without any other components.
A big step around 700 Hz required a ferrobar HQ40 coil to smooth out the hump (diagram 1, blue). In the next step, a parallel capacitor took care of the plateau between 2 and 8 kHz (diagram 2, blue). The last step was to insert an air coil with a 1.4 mm wire thickness, which provided a little more volume around 2 kHz in addition to the steeper decay above 3 kHz. At the same time, the resistance from the coil lowered the area under 1.5 kHz by about 1 dB (diagram 3, blue). Here we would like to discreetly point out that a crossover is a very complex construction that cannot be transformed into a “high-end version” by putting in “better” components. The resulting frequency curve depends on the right interactions between all of the components, especially the losses inherent in every component. Still, those who want to adjust for their own listening preferences can go wild with the resistors, which determine the volume for the tweeter, as shown below.
The tweeter, too, is initially measured in the box without any components. For this measurement, we set the lower limit for the measurement range to 500 Hz in order to avoid putting unnecessary stress on the Airmotion transformer (diagram 1, green). An Audyn MKP-Q4 with increasing resistance at lower frequencies reduces the volume under 7 kHZ, but of course that alone is not enough (diagram 1, red). As a result, we also add a coil with 0.71-mm-thick wire parallel to the GAM 100; that creates a steeper slope under 3 kHz on the one hand, and slightly increases the volume between 4 and 12 kHz (diagram 1, blue). In the second diagram, the 12 dB filter is now shown in green; the red line shows the influence of another Q4, which works with the previously installed components to create a 3rd-order filter. Since the AMT’s volume is still too high, a resistor was placed in front of the switching mechanism (diagram 2, blue). The 3rd diagram shows how important the position of this resistor is. In order to preserve the blue curve, R was placed between the crossover and the tweeter (HT). The last step for the tweeter was a suction circuit, which did its work between 5 and 12 kHz (diagram 4, blue).
Now we were able to put all of the branches together to obtain the red line, which produced clear cancellations between 1.5 and 7 kHz in the separation range with the same phase position. So we quickly connected the tweeter the “wrong way around,” and now the curve was right – with nearly 93 dB in the middle and a 2 dB +/ - deviation from the guide line. The peak around 18 kHz didn’t bother us too much, since it almost disappears at our preferred listening angle of 30 degrees (boxes parallel to the walls). Since we weren’t satisfied with 10 components for just two chassis elements, we went with a baker’s dozen for all those tube listeners out there and threw in an impedance correction in front of the crossover.
|Frequency at 0/ 30/ 60°|
|Distortion for 90 dB||Step responce||Waterfall|
But that was really all, so now we can move on to the uncommented pictures of the installation.
Don’t get the wrong idea: we didn’t combine our four Audibles into a home theater consortium to see whether they would work for movies. Fortunately, as we mentioned above, the new #17s are by no means designed to cater solely to watchers – they are equally, if not more, suited for listeners. That is why we set them up on stands in our listening room and connected them to an Experience KT 88. The first thing that fell into our hands was the friend ’n fellow CD “Covered,” which our user malchuth had luckily left behind in the studio the week before. The old Louis Armstrong piece “What a wonderful world” may have been covered many times already, but the version for voice and guitar was obviously recorded with the little Audibles in mind. The female singer’s expressive voice was tangibly located right between the boxes, and the wide range of noises made by the guitar player’s fingers stays right with the instrument. The quiet notes weren’t thin, and the loud ones weren’t screaming; the tonal color is identical at every volume level, the stage is wide and deep, and every facet of the music is completely believable. Wasn’t that the exact definition of the Blues Class?
The testing continued with Hugh Masekela’s “Stimela,” from the CD “Hope.” His flugelhorn came to the ears with a pleasant warmth, and sounding not at all tinny. The drum heads were taut, and always the right size. After that, we ventured into somewhat “deeper” pieces. We jumped a little bit when a voice asked, “Yello?” Our neighbor, attracted by the fairly high, but not uncomfortably loud volume, joined us on the familiar sofa. We listened to a couple of rock songs on vinyl, from the good old days when music was still handmade. They definitely benefited from the slight PA character of the Audible 17. In contrast, the bass lost something in depth that it had gained in tightness. But we can give you a quick preview in that regard: the AXPs will be getting some big brothers soon. Then we can stop fielding questions about a matching Audible subwoofer. And yes, we’re coming up with a center, too.
|Speakers||Gradient AXP 06||Wood list in 21 mm Multiplex|
|Gradient GAM 100||per box in in millimeters:|
|Sales and||Intertechnik, Kerpen||390 x 284 (2x) sides|
|Construction||190 x 284 (2x) lid/floor|
|190 x 348 (1x) back wall|
|Function principle||Bass reflex||190 x 328 (1x) baffle (front)|
|Nominal impedance||8 ohms||190 x 144 (1x) reflexboard|
|Connection terminal||T104 LC||190 x 100 (1x) reinforcement|
|Insulation/damping||1 bag Sonofil|
|woofer: 5 mm|
|tweeter: 6 mm|