October 2020: Recent update regarding speakers. Gone from traditional U-frame baffle to ladder frame to 'Scaffold Frame' ! Not to everyone's taste, admittedly, but after going baffle-less as an experiment. I was so shocked by the
result, there is no going back! Please click here to see more details on loudspeaker history.
The metal scaffold transfers much less energy into the old wooden ladder frame which I was always struggling with. Careful isolation was needed for the full range units. With this new design, the weight of the magnets (heaviest part) is now supported by a simple cable which provides the best isolation. Construction is also very simple.
Recent update to KEF HTS3001C which is actually going against the OB theme. However, the units are 'baffle-less' and the chassis are totally inert. They are also very efficient @ 90db and go loud with few watts. They employ a version of the famous UniQ driver and are a 3-way unit. Still partnered with a pair of reversed Dayton UM18 woofers (updated from 15"). Reversing the woofers adds directivity and reduces room modes.
The 18's allow me to play at greater volume without frying coils.
Went though a few stages to get to where I am now. The 18" AE (Acoustic Elegance) Dipole woofers were replaced by the Dayton 15" 390s a few years back, and now UM18's. These have much heavier fiber-glass cones and a more powerful motor. Arranged in series, they give more depth and slam, take more watts and yield higher SPL's without complaining. They generally take more abuse and dont bottom out as easily as the AE's. I found I get REAL deep bass (20hz) with heavier inefficient woofers vs lighter more efficient designs.
In this F.A.S.T. configuration
(FullRange Assisted Subwoofer Technology) or WAW (Woofer Assisted Wideband) there is no crossover to sap
efficiency and resolution. The FR connects direct to the main amp &
handles from 250Hz up to 16k.
Dispensing with the baffle has resulted in a clearer more open sound. I guess the baffle was contributing to some muddying. Also imaging has improved, and the bass couples better with the room creating fewer modes. As as a result I was able to push the speakers back closer to the rear wall.
I have found the UM18's need no eq to compensate for for bass baffle losses. This was a surprise to me as these units seem to deliver bass down to 20hz with amazing slam!
The disadvantage of using inefficient woofers is they need a lot of power, but watts come cheap with the Behringer NX6000D's. The built in Digital Signal Processor makes setting the crossover point a breeze & also iron out room modes.
A pair of Behringer NX6000D's power the 18" woofers. This is primarily PA concert venue Class D full range amp. Not sure what it sounds like full range, but from 20 - 300Hz & it sounds great! Delivers effortless distortion free power, control & resolution..........everything you want in a sub amp.
The DSP section just plugs into a laptop via USB & uses software available from the Behringer site. All relevant parameters can be adjusted in real time from your listening position. The crossover page allows seamless integration with the full range unit. There is a choice of 4 variable slopes, plus crossover point & gain. There is also an 8 filter Parametric EQ page to set compensation for room modes & baffle deficiencies.
Chord Qutest / Limetree combo is the latest upgrade. Music filed stored on Hard Drive hard wired to unit via USB connector. Easy to setup & control with its own app via wifi.
The Qutest unit is bullet-proof playing all formats reliably. Here it benefits from sitting on its own isolation platform. Sound really on a par or better than vinyl, so this has become my main go-to for playing music.Also realise now the importance of the power supplies and digital equipment. Been through a few of these as well, and settled on the Temple Supercaps supplies as one of the best with a solid, detailed and dynamic presentation, but no harshness. Both Qutest & Limetree have their own dedicated Supercharger power supply.
I would describe the sound from this system as dynamic, musical, but full of detail.
The KEFs are cheating a bit as they are a multi-driver sealed unit and tend to sound good with even poor recordings.....something I couldn't get away with using full rangers. As a result I am not using any eq. The small carbon cones are very light & fast, especially with percussive instruments. The tweeter has a 180 degree horizontal dispersion using only a high pass filter cap, no crossover. The unit delivers a huge soundstage which is behind the speakers and very Open Baffle-like in its presentation .....perhaps because they lack a baffle.
The KEFs have improved efficiency, dynamics, image focus and detail devoid of nasty peaks or troughs.
The woofers driven by the Behringers integrate seamlessly with the KEFs. They go floor-shakingly deep when the signal is present but there is no boom from room resonances such is the control from the PEQ. For serious bass I believe the woofer needs to be actively driven with PEQ. Control of the room modes is a necessity.
I can play a wide range of music on this system from softer acoustic jazz material to pumped up Level 42 playing at realistic levels. Modern electronic music which I was never too keen on makes sense now that I can hear/feel that bottom octave. Kraftwerk, Depeche mode never sounded so good not to mention the more modern Junior Boys and London Grammar. The system delivers it all in a musical, fatigue-free fashion.