EPOS ES-14N Standmount Loudspeakers (Pair)
BACK TO THE FUTURE!
A classic speaker returns to the future.
Concept
Restarting EPOS could only mean re-creating the most famous model, the ES-14. This was a 2-way speaker in a fairly big cabinet and classic looking cabinet, to be used on a dedicated stand. The design should be classic, not lifestyle, only doing things that help with the sound and as straightforward as possible.
Analyzing the old construction was interesting. It used a 7“ woofer with Polypropylene cone and an underhang coil with a huge magnet, but multiple layers of VC winding to make the whole coil heavy in order to get a sort of roll-off in the response curve of the woofer. The size of the woofer was not following any standard – too big for a 6.5“, but too small for an 8“. But it was a clever choice, because you could get more drive at lower frequencies more like an 8“ and a midband character closer to the 6.5“.
Cabinet
The cabinet itself is using more or less the same volume of the original ES-14. That’s not a big surprise, as the cabinet volume is the result of the driver configuration and the defined bandwidth of the speaker. However, the shape of the cabinet is different. The front baffle is tilted to the back in order to time align the woofer and the tweeter plus it can help with the standing wave mode between front and back. As the design is a reflex system, a port is of course needed. It’s located on the back of the cabinet and the whole shape of the port has been chosen to minimize air flow noise. In order to compensate for the open tube resonance of the port, some openings were added in the middle of the port. To avoid loss of low bottom end, those openings are covered with soft material, tuned to only kill the unwanted resonances of the port.
The cabinet uses a double layer MDF construction, glued together with the latest generation of damping glue. This latest generation is more consistent compared to older solutions and allows easier production. Additional bracing has been used to control the panel vibration modes and reduce the unwanted radiation of the whole cabinet. Only a little damping material is needed internally.
The front plate is an extra part to be glued and screwed on the main cabinet. It has a 45° chamfer around it to control diffraction effect in the 2000-3000 Hz region. The first prototypes used square cabinets and it was impossible to get a good frequency response on axis and out of axis. Rounding the corners was not really helping, only the chamfer made the diffraction error a lot smaller and helped balancing the upper midband. An old fashion way, but a useful solution. The speaker comes with front grille, but it is not recommended to use it when listening to music. It’s more a protector when not using the speakers. The tweeter itself is protected anyway and the PP cone is not easy to damage.
The alignment of the box is a flat 4th order alignment with a tuning frequency of 38Hz. It matches with the bottom end gain of many listening rooms and allows fast and precise bottom end when used in the right position in the room. The binding posts are 4mm banana sockets, mounted on a metal plate. Those banana sockets use very little metal internally to guarantee the best sound – that’s one of the nice ideas of the original design and better than using very expensive “High-End“ binding posts with little metal but a high price tag. Those single wiring sockets feed the amplifier signal to a crossover that sits on the rear panel of the speaker.
Crossover
The original crossover needed very little components and was extremely simple, the new ES-14N follows the experience of the last 20 years that electrical parts are easier to control than mechanical filtering in driver units. In earlier days, before Klippel, the multilayer coil of the original woofer was designed in a way that it rolled off the woofer with the weight and the high inductance of the windings.
The original crossover needed very little components and was extremely simple, the new ES-14N follows the experience of the last 20 years that electrical parts are easier to control than mechanical filtering in driver units. In earlier days, before Klippel, the multilayer coil of the original woofer was designed in a way that it rolled off the woofer with the weight and the high inductance of the windings.
Impedance and Distortion
Impedance:
- The speaker should be an easy load for amplifiers – that’s why the average impedance is higher than a usual 4 Ohm speaker. I also got a compensation in the midband to make it easier for tube amplifiers.
Distortion:
- Modern speakers should be capable to deliver low distortion even at higher levels. Below the measurements @87dB and at 96@
Mid/Bass Driver
In the new woofer, the coil is only 2-layer and with compensation rings, the impedance over excursion is very constant and that avoids modulation of the crossover. The coil is executed as air coil and adds no core distortion. A non compensated magnet, would indeed react with a crossover and that means the old idea made sense. However, the way to roll off the woofer with high inductance, added another set of problems – but we learned about it only in the last 20 years. There is a small resistance between the woofer and the amplifier in tower to make the design less sensitive to different damping factors. Instead a larger magnet controls the alignment.
Tweeter
The tweeter is using no Ferrofluid in the gap to suppress the resonance frequency of the tweeter. Ferrofluid sounds like a good idea, but it is a sort of oil that changes behavior when playing music. This is a very non linear process and modifies the sound depending on level and music style. Tweeters with no Ferrofluid are more open and natural and show less dynamic compression compared to standard tweeters with Ferrofluid. The other side of the coin: it needs a bit more crossover to be safe, but the total combination is a lot more linear. Even so the metal dome peak is shifted to around 30kHz, a new sort of filter has been added to notch it out without changing the level below 20kHz. The reason is that modern digital converters are shifting a lot of noise to higher frequencies.
Stand
To give the speaker a home to sit on, a dedicated stand is available. The middle part is made as a massive wooden bar, combining 4 layers of wood, glued together with same damping glue used internally in the ES14N. The top plate is a double layer steel plate with a Bitumen layer in between and the bottom plate is a thick steel plate to hold adjustable spikes. The Speaker can be shipped without a stand, so other 55cm high stands can be used as well.
Shipping typically 3-5 days
