Once upon a time ... That’s the start of a sentence we always liked to hear as children, since it was associated with the joyful anticipation of a (grand)mother’s sweet fairytale. Only much later did we realize that it also meant a departure, and that things were no longer the way we remembered them. We had to use those words often for more than a year whenever people asked us about the FirstTime 6, and our listeners were not always pleased. Again and again, they asked about a follow-up assembly kit, but unfortunately the W 148-4 doesn’t play well with band-passes, so it wouldn’t work as the interior driver. We also couldn’t come up with any usable results from simulations with the other cost-effective #15s in our product range. So we stuck our heads in the sand for a while and didn’t have any plans to redesign the box, until Gradient finally finished developing the W 176-4 and it fell into our hands. Despite the larger diameter, it didn’t take up any extra space, and it solved the problem that had so far successfully prevented us from making a follow-up box. Since there were also new playfellows in the mid-range and tweeter area, it would have been unfair just to attach an MK 3 to the FT 6 title – all of those changes deserved a new name: the FirstTime 12.
Once we had decided which bass would be housed in the future box, the only other issue was finding the right companions for it. Our experience with the FT 6 taught us that using components from the same family was the best approach. First its tweeters fell victim to the end of production, then the bass and mid-range speaker disappeared into the nirvana. That’s why we stayed with the Gradient Select series, which made choosing the tweeter very easy. Sesame Street’s Count von Count, whom people Udo’s age will remember well from their childhoods, would have responded to the command “Count the tweeters!” with a resounding “One! In any case, the GDT 104 N is still unrivaled. It’s already doing a good job in many assembly kits, so we used it. There was more to consider with the mid-range speaker, since both the W 148 and the W 115 were available, both of them in either four or eight ohms. The larger mid-range speaker has already been used in the FT 10, where it gives a bravura performance. Both versions do require a larger cabinet, though, in order to reach the 100 to 150 Hz needed for the band-pass connection without any exaggerations. That conflicts with the clear goal of seeing only tiny speakers while being completely blown away by their bass presentation. So we just had to choose between the two W 115s. The four-ohm version provides 3 dB more sound pressure at the same amplifier setting, but it does create a critical impedance dip under 3 ohms in the transition area to the band-pass, due to the considerable hot flashes often produced by do-it-yourselfers’ multiple amplifiers. So that took care of that part of the chassis selection; then we moved on to drawing the cabinet. The measurement data for the chassis in question can be found here, along with the downloadable zip files: (Quickly 18 update), (FT 11) and (Chassis test)
For the band-pass, LspCAD calculated 7 liters of enclosed volume and 5 liters of reflex volume, including the entire length of an HP 50 BR. With an additional 2.5 liters for the W 115-8, we had all the dimensions we needed so that SketchUp could turn them into a square box, nested inside one another. The goal was to move the internal boards around until they weren’t in each others’ way or in the way of the chassis. That was easy once I showed the mid-range speaker to its place in front of the closed band-pass chamber and stuck the reflex chamber under it. There was also plenty of room for the forward-facing reflex tube. Before the assembly, I sawed a hole in the middle board for the interior driver. In order to avoid installing the bass while we were still gluing the boards, we also put together a frame that could be screwed onto the floor board later. That gave us access to the belly of the box without damaging its stability. We didn’t take any pictures of these simple steps or the gluing, but the assembly plan should be enough to help you build the planking. The whole structure can be seen three-dimensionally in SketchUp, and turned in every direction. Any missing dimensions can also be measured easily in this free program.
The assembly plan file is provided in zip format.
The MDF was quickly shaped into the new form; once the joint glue was dry, we sanded it and made the cutouts. We used the shadow-gap router to trace all of the cut edges, which gives the box a slimmer figure. In order to hide the color of the MDF somewhat, we painted the boxes with a blue stain. There are a few pictures of this, with explanatory texts.
Once the paint was dry, we packed two whole bags of Sonofil into the box, installed the chassis elements that were connected to the outside world by wires, and were then able to start building the crossover. The first idea behind the band-pass principle involved using the mechanical filter that is represented by every type of cabinet. The enclosed part limits too-deep frequencies to 12 dB/octave, and the reflex chamber does the same for the top range. According to this nice theory, the reflex tube then only transmits a narrow frequency band that can get by without an electrical filter. Unfortunately, things look different in practice, because of course the bass speaker also blares mid-range notes into the box And that’s exactly how it sounds when it has to make do without any other components. Using a core coil and an electrolytic capacitor, we roughly weakened the mid-range enough that it was more than 20 dB below the useful level.
The closed chamber behind the W 115-8 also acts as a mechanical 12-dB high-pass filter, which protects the mid-range speaker from large lifts at low frequencies. It is supported by a large electrolytic capacitor that creates an additional 6 dB of edge steepness. In order to make sure the W 115 doesn’t interfere with the tweeter’s work, I limited its audible activity in the upperrange using an upstream coil and a parallel capacitor.The GDT 104 N was also able to manage with a network of a capacitor and coil, as well as a potentiometer to adjust the volume.
Overall, the individual branches add up perfectly if the bass is welded onto its partners out of phase.
Since there are always questions about installing the components, we have provided photographic documentation.
Now all that’s missing are the measurement diagrams:
|Frequency response and phase||Impedance||Frequency response under 0/ 30/ 60°|
|Distortion for 90 dB||Step response||Waterfall|
Of course, things got exciting when the FT 12s were finally set up in the listening room, where they had to prove themselves with an AVR. We would have preferred to listen through an old stereo amplifier, which is more likely to be the sound source, but due to a lack of assets that wasn’t possible. Unfortunately, the range of CDs that the FT 12 will be asked to play is probably also fairly small in most cases. So we started by throwing Katie Melua into the machine, and she responded with pleasure. Her soft but well emphasized voice proved it, with good spatial resolution and without any of the sharpness that much more expensive calottes would have given us. Still, there was no shortage of detail – they just weren’t crammed inappropriately into the foreground. The bass goes lower than in the FT 6, which makes a subwoofer unnecessary for music even in my 42 m² of space. Its clear notes are located behind the singer, next to the short, dry beats of the drums – right where it belongs. Now, playing mellow cuddle music is not really a challenge for any halfway decent speaker; heavy rock music is more of a challenge, like the Rammstein that came crashing around my ears next. That needed to be a little louder without making my ears hurt, everything coming out a little more spectacularly. No problem for the FT 12, but a bit harder for the AVR, whose alleged 7 x 160 watts are missing the zero, realistically speaking. Peter Fox, on my Bravo Hits CD, required fewer simultaneous loud and soft notes. There were also plenty of stomping low notes to support the Pussycat Dolls, who followed on the heels of the bard. Even Madcon had no reason to complain that their bass, recorded slightly too loud, was hidden in the background. In order to avoid filling this report with almost-forgotten artist names, we put on something more contemporary at the end of our listening session, switching over to the built-in tuner to hear the latest news. In a clear voice, the announcer crisply told us what was going on in the world. We’ll save ourselves the trouble of explaining the contents this time – much of it was harder to understand than the announcer himself.
Short postscript: A user from a forum has just left the listening studio, the FT 12 assembly kits in his trunk. It was great to see his incredulous face when Yello’s “Baby” hit his ears. Naturally we asked if he would write up a sound description for us, but he was simply speechless. He looked like he had found himself in a fairytale.
|Chassis:||Gradient W 176-4||wood list in 16 mm MDF|
|Gradient W 115-8||per box:|
|Gradient GDT 104 N|
|39,0 x 32,0 (2x) Sides|
|Sales:||Intertechnik, Kerpen||39,0 x 18,0 (2x) Front/ back wall|
|Construction:||Udo Wohlgemuth||28,8 x 18,0 (4x) lid/ floor/ division board|
|23,2 x 18,0 (1x) mid range -clip board|
|Nominal impedance:||4 ohm||Milling depth:|
|Damping/insulation:||2 bags Sonofil||W115-4: 4 mm|
|Terminal:||T105MS/AU||GDT 104N: 3 mm|
|HP 50 BR unshortend|
Approx. cost per box:
|96,00 EUR/USD||Wood cutting: 12 EUR/USD|