My absolute reference speakers
When building these I tried to design everything for the best possible sound. They're the biggest, boldest and most uncompromised speakers I've built.
The whole speaker is built to serve as the best possible basis for the Voxativ full-range driver used. They're by far the cleanest, fastest and most resolving drivers I've heard.
It was clear that drivers as lightweight and as delicate as the Voxativs would show every single internal reflection of an enclosure, so the only way was to forgo the enclosure completely.
In order for the sound to be as coherent as possible it was clear from the start that the speaker had to be a mirror image in a MTM configuration and with time-aligned drivers.
It also required the fastest and most transparent sounding woofer. The obvious choice here would be the GPA Altec clones, but none have parameters suitable for OB use and they are still somewhat heavier than the woofer ultimately chosen. It turns out this woofer, although quite affordable, can beat some of the most expensive woofers made specifically for the OB application with some 20dB lower distortion in the subbass region at 90dB!
It is also the most efficient 15" woofer in the region of interest I have come across. Something that is of utmost importance for it to not sound lean. Remember - there is no level pad on the 100db/W Voxativ! Quite a challange to find woofers matching its sensitivity.
The crossover consists of a simple coil and an impedance correction circuit. No crossover parts for the Voxativ driver. The most transparent capacitor is simply no capacitor.
Both the coil and cap uesd here are overkill for this application, normally being used for midrange applications. The resistor is simply the best I could find.
Development was a challenge
In order to get accurate measurements of such large speakers many hours were spent on finding the most accurate way to measure them.
Since the floor is an integral part of the lower baffle lifting the speakers up high was not very uesful. In the end a compromise was found that produced accurate results and allowed a full 360° measurement.
The back of the frame
During development it becamse clear that a U-frame was needed to get the right amount of bass. However normally U-frames are plagued by resonances that also impact the sound towards the front. Still, this turned out to be preferable to an H-frame, which many objectivists consider superior, at least with the minimalist first order crossover used here.
Thus special care was taken to dampen both the resonances created by the wavefront leaving the back and also the resonances in the frame themselves.
For the baffles the weapon of choice was a massive plate of lead secured to a damping layer, glued with a special elastic and ultra-strong glue. Finally, the plates are then screwed to make it impossible for the heavy plate of lead to come flying down.
This novel approach was able to virtually eliminate a resonance the baffle had, while still keeping the quick character of the natural wood chosen as a baffle material. Combining both subjectivist principles and hard objectivist truths.
Both the components on the crossover board and the board itself are also fastened on a combination of vibration absorbing components. Finally the components are covered by the same mat of natural wool as the whole back of the speaker is.
So while the radiation pattern is still that of a dipole, the frontal lobe is a bit louder than the rear. Imaging was improved this way.
The Voxativ cables
are the only component between the incredibly resolving widebander and the amplifier.
Normally the cable for a widebander has to be somewhat warm sounding as fullrange speakers with such high efficiencies are a bit lean. Essentially the cable becomes what would normally be the baffle-step compensation filter.
But since Amon uses the woofers for this purpose - an approach that also drastically lowers distortion, I was free to chose the most transparent cable I could find.
After some trial and error I found silver-gold foil in natural cotton to be the best sounding option here. Very expensive, but this is what it had to be.
The woofer cables
have a very different requirement. Very thick cables are needed here and as such silver is out of the question. Thus the very musical sounding tinned copper in cotton was chosen, as a flat foil-like cable and with some 25mm^2 area. These are truly end-game woofer cables, easily allowing an effortless bass presentation while still allowing for a coherent sound.
The speaker feet
Since the distance to the floor can't exceed 2cm we can't use typical massive flagship speaker stands. Instead a solution was found with sorbothane disks underneath carbon fiber disks, upon which the speakers are placed using wide spikes.
The sorbothane was chosen for rigid coupling of the subbass transitioning to decoupling from the midbass and upper bass onwards. While this approach results in more subbass being transmitted to the floor, it also makes it rock solid sounding.
So while your neighbors might not like it - you're gonna love it.
The resulting response in my room
As can be seen we have useful extension down to 25Hz. In a larger room we could expect even deeper bass and a smoother response in the lower midrange, however we can already see that the upper midrange is very even keeled and the sound itself is never lean.
Impedance dips to just 3.5 Ohms, but is otherwise quite flat and benign.
If you prefer to biamp the load will be very easy on the amp for the Voxativs, while the woofers will be a normal 4 Ohm response.
Close to a Figure 8 radiation pattern, but with more energy towards the front.
Very good for what it is
Nominal Impedance: 4 Ohm (minimum: 3.5 Ohm at 150Hz)
Impedance rises smoothly towards high frequencies, slightly inductive load.
Frequency range (-10dB): 20Hz- 30kHz
Frequency range (-6dB): 25Hz - 25kHz
Frequency range (-3dB) 35Hz - 20kHz
Phase response: Excess phase of the whole system is identical to that of the Voxativ widebander itself
Dimensions W x H x D: 550mm x 1800mm x 440mm
Weight: heavy and large, requires two people to move
2-way speaker with an 8" full-range and two 15" woofers
Power rating: Circa 300W, they go loud
(Remember there is no high pass filter on the full-range driver)
Acoustical first order crossover at 360Hz, time aligned drivers
Bi-wiring terminals with an extra ground lug connected to the driver baskets and crossover components
12mm² tinned copper internal wiring
no crossover components on the Voxativs
Balanced woofer low-pass featuring foil coils with waxed paper dielectric
Woofer Zobel: Pathaudio resistors and MKP in oil capacitors, both connected to ground
Baffle construction featuring special shapes to flatten response irregularities
entirely wooden construction, featuring extensive bracing and natural wool damping