E50

The heart and soul of any passive speaker and one of, if not the most important part of a passive speaker. This is sadly often forgotten or an afterthought where money is saved, as customers do not see it. We have spent so much time on testing different components over the years we have worked with speakers to achieve the sound that we wanted. We have worked with the respected manufacturer Janzten Audio since 2008, which is even before Buchardt Audio was officially launched. In comparison to our S400s, the parts quality has taken a good step up, where we have invested in Jantzen "Superior Z-Cap" and their thick 14 AWG copper foil "Cross Coils" as the only part (1-order) for the Purifi woofer. The tweeters resistor is a 1% tolerance wire wound high-end audio resistors also from Jantzen Audio. For the internal wiring, we use the finest oil- and cotton-insulated copper cables from Duelund Coherent Audio on the tweeters where the woofers use a thick 13 AWG pure OFC copper cable from Jantzen Audio.  

This is where you really see the E50 set itself far apart from competing speakers in this price range, and far above it as well. We wanted to spend money where we know it matters the most to the listener, even though no one would actually see it.

Some additional information on the Cross coils : 

The Cross Coil was developed in cooperation with Mr. Per Skaaning from Audio Technology™ (Denmark).

It is a high-performance foil inductor offering improved power handling and dynamic head room.

Using pure copper foil, we have insured a better surface for electron travel, a better distortion reduction, a higher power handling and improved dynamic headroom, compared to wire-based inductors.

The coil is wrapped in clear shrink foil to protect the outer layer of foil and to help maintain the integrity of the windings.

We know that with rising frequency, the electrons will move towards the surface.
This Phenomenon is known as power distortion. Therefore, we need as large a surface as we can get, to prevent the electrons from getting “squeezed" on their path to the surface. 

Some additional information on the Superior Z-Cap :

The Superior Z-Cap is a metalized polypropylene foil capacitor but made as special construction we call a “Super MPK Capacitor”.

Super MKP capacitors are made with a double lane of metalized polypropylene foil, hence a double foil construction.

By using special winding machines and winding techniques, two capacitors are connected in series within one capacitor housing, When making this type of capacitor you therefore need 4 times the foil used in standard type metalized polypropylene foil capacitors.

Compared to standard type metalized polypropylene foil capacitors, the Superior Z-Cap is on a higher audiophile level, where even finest nuance improvements can be heard.
An extremely well made and precise MKP capacitor with a capacitance tolerance of only +/- 2%.

We do not fill our capacitors with any dielectric fluid, which eliminates all risks of evaporation or leakage that can shorten longevity and quality of the capacitor.

All components are mounted on the highest-quality PCB boards with the thickest copper lanes possible.

The internal wires consist of a mix of Teflon-insulated, solid-core copper with silver plating and oil- and cotton-insulated copper cables from Duelund Coherent Audio for the tweeter.  

The PTT6.5X is a 6.5” driver that truly cracks the extended-stroke code. PURIFI’s research has identified the parameters that have so far prevented extended stroke drivers from breaking through in truly high performance audio. The distortion of the acoustic output of a driver is a combination of several separate distortion mechanisms in the motor, cone and suspension. When testing a complete driver with sine waves, a situation often arises where a small tweak seemingly improves harmonic distortion (HD) by letting two mechanisms counteract each other. This always leads to a clear worsening of intermodulation distortion (IMD) that becomes obvious when testing the unit with a more complex signal. This is why traditional HD tests fail to predict subjective sound quality.

PURIFI takes care to optimize the various distortion mechanisms separately, thus guaranteeing that any measured improvement truly reflects a real audible improvement no matter what the signal is. Accurate mathematical models are developed for the motor, suspension and the vibroacoustics of the dome and surround. These models clearly explain several distortion mechanisms in each domain, which provides fundamental insights into better ways of constructing the motor, cone and suspension. Finally, the same models are used to numerically fine-tune the geometry. This way of working reliably reduces multiple distortions mechanisms which secures low IMD for complex signals.

Low Force Factor Modulation

- Prevents voice coil current from modulating Force Factor (Bl). The PURIFI motor completely avoids this classical Achilles’ heel of long stroke drivers. This translates into low intermodulation (IMD): clean, undistorted midrange even in the presence of a heavy bass.

 - Equates to low impedance modulation, meaning that drive current is not distorted by cone motion.

Very Constant Force Factor over Excursion

- Prevents voice coil position from modulating the force factor. This is the classical cause of “burbling” i.e. amplitude modulation of the midrange by large low-frequency cone excursions.

Low Surround Radiation Distortion

- The surround contributes to sound output. Conventional surrounds produce distortion as they deform. PURIFI’s Neutral Surround geometry avoids this mechanism without constraining motion. This reduces harmonic distortion as well as intermodulation distortion.

Low Magnetic Hysteresis Distortion

- Hysteresis means that magnetic domains in iron retain traces of previous magnetization / demagnetization cycles which cause distortion when magnetized or demagnetized again. This distortion masquerades as benign harmonic distortion when tested with a sine wave but takes on a crackling or noisy character with more complex signals.

- Removing hysteresis distortion translates into a very “fluid” presentation with excellent front/back separation in the stereo image and a perfectly black background between instruments.

Cleaner than large-cone short-stroke drivers.

- The combination of the above characteristics results in a compact long-stroke driver that delivers complex sound with a clarity and lack of effort that was previously the exclusive province of large-cone short-stroke drivers. Additionally, thanks to the small cone size, the driver has excellent midrange reproduction. It is highly suited for two-way systems.

This is our first collaboration with Scan-Speak, one of the most recognized names in high-end audio. For those unfamiliar, Scan-Speak is a known and admired driver manufacturer, with all their drivers handmade right here in Denmark, just an hour away from our headquarters. A textile dome tweeter might not sound like the most exciting choice, but for us, it’s always about sound quality over fancy materials. We focus on what delivers the best audio performance to our ears and taste, and this tweeter was chosen for exactly that reason - it does the job beautifully.

We worked alongside the engineers at Scan-Speak to develop this custom-designed tweeter to match the newly engineered waveguide and the Purifi woofer. The foundation is based on Scan-Speak’s renowned and highly praised D2905/970000 Classic 28mm dome tweeter. For the E50, it has been optimized for waveguide loading, along with several additional modifications to suit our specific use case.The 28mm tweeter features Scan-Speak’s patented SD-2 symmetrical drive magnet system and a German-made textile dome diaphragm, coated in-house at Scan-Speak for optimum linearity up to above 30 kHz. Combined with its optimized rear chamber and long linear excursion, its resonance frequency is very low, allowing for a low crossover point between the tweeter and midwoofer. However, one of the modifications made to the tweeter was to enhance its performance at lower listening levels, enabling it to operate more "freely." This adjustment compromised the original D2905/970000's capability for very low crossover points, but this was not a concern for our design. Ultimately, it resulted in a better-sounding tweeter tailored to our requirements.

The goal with the new waveguide/tweeter combo was to achieve slightly wider dispersion than most similar designs and to deliver a sound that is easy to listen to, yet highly resolving for a textile based tweeter (also partly thanks to the exceptional crossover components).

The tweeter’s power handling was also important to us, ensuring that it never shows any strain while keeping up with the Purifi woofer. So despite being a rather large dome in a waveguide which naturally boosts its output capabilities, the crossover frequency is set relatively high thanks to the incredibly well behaved Purifi woofer. As a result, the tweeter does next to no work, keeping distortions incredibly low even at high output levels.

One of the key highlights of this model is the custom-designed waveguide, tailored specifically for the E50’s cabinet, tweeter, and woofer. Instead of casting the waveguide in aluminum like on our other speakers, the E50’s waveguide is CNC-machined directly into the 28mm solid wood front baffle, combining craftsmanship with acoustic precision.

Waveguides are something we have worked with for years. The benefit of waveguides are many, and depending on how well its designed, without drawbacks. 

Directivity matched to the woofer
When designing a waveguide properly, it's important to match it to the woofer you intend to use. This ensures that the off-axis performance is consistent around the crossover frequency, making the transition between the drivers smooth and allowing them to function almost as one.

Lowering the tweeter's workload
The waveguide reduces a lot of the stress on the tweeter by naturally boosting its lower frequencies, allowing the tweeter to produce more sound with less effort. This significantly lowers the tweeter's distortion and dramatically increases its output capabilities.

Controlled Directivity
In this design, we've taken a different approach from our CDC (Constant Directivity Control) waveguide design. This time, we allow the tweeter to play a bit wider and gradually narrow at the highest frequencies. This choice was made primarily to create a wider soundstage. However, it does come with a slightly higher room placement requirement compared to our other design, as the wider dispersion increases the room’s interaction, meaning higher requirements for your speaker placement. This also means that toe-in or toe-out positioning will have a bigger impact on the sound, depending on what intensity of the tweeter you prefer. In contrast, the CDC design is less affected by toe-in adjustments. 

Minimizing Edge Diffractions
Edge diffractions caused by the cabinet occur when sound from the tweeter reaches the edge of the cabinet, creating a diffraction that essentially acts as a secondary sound source. This is a common issue with most speakers and can lead to irregularities in the frequency response. Waveguides and horns can dramatically reduce these issues, resulting in a cleaner and less harsh sound.

We know this is an unusual choice for speakers. So why do it? Well, it's the real deal! It simply looks and feels way more superior to a veneered or painted MDF cabinet. It's more eco-friendly and is just a way higher quality cabinet overall, that can last forever if you treat it well. As soon as you get them in your hands, you will understand what we mean.

We are super proud to say that all of our solid wood cabinets are hand built at our own factory in the heart of Denmark, with wood sourced from a local FSC certified wood supplier. FSC ensures that for each tree used, a new one is planted. Instead of MDF, which is wood dust compressed and using a lot of glue, solid wood speakers require next to no glue in comparison. This is desirable if you wish to build a more eco-friendly product. Having our own production of cabinets is a big benefit, as we are in full control of the entire process. Like selecting a high quality furniture grade wood that is properly dried before it is treated. This is to ensure it will not contract or expand much in different climates. We are hands-on for the entire process to make sure the quality is just as we want it.

It's rare that we see speakers made from solid wood, as it is a lot more expensive to produce, which is the main reason why most companies choose another solution. Higher requirements for production are also needed, to make sure the cabinets can withstand the test of time, and different climates around the world. One thing to mention here is the way cabinets are put together, where we have a special tool to cut the wood, so the sides are locked together, not only glued like you normally have. We also build the cabinets a bit thicker than we usually do with MDF, and we dampen and brace them differently as well. It's a cabinet that does not provide any more coloration to the sound than an MDF/HDF cabinet would, contrary to what many might believe. From multiple testings, there has actually been a small improvement on resonance and decay control in comparison to MDF/HDF cabinets.

The longevity of cabinets was an aspect we wished to improve on using solid wood. With over 10 years in the business, one thing that is hard to fix on veneered or painted cabinets is the wear and tear cabinets can be exposed to over the years of owning them. Being able to fix scratches or dents on the cabinets is a huge benefit of having solid wood speakers. If you desire, you could even change the appearance of them completely. It's simply a much more forgiving and robust construction in comparison to your traditional speaker cabinets.

As you may or may not know, a passive radiator is a more expensive alternative to the usual bass reflex ports that you'll find in most loudspeakers. So why did we go with passive radiators instead of a port?

 - The passive radiator allowed us to reduce the size of the E50 by 30% in comparison to a bass reflex/ported design! Providing you with a smaller speaker, yet crazy good and deep bass performance.

 - The E50 would have no port noise, no time smearing of leaking upper bass/lower midrange back wave in comparison to a port.

 - No port = More forgiving of wall-boundary placement!

 - Lower time distortion / better damping

The passive radiators for the E50 were custom-designed specifically for this speaker. We aimed to create a radiator with an extreme peak-to-peak stroke of 28mm, while maintaining a low moving mass of 58 grams.

We have worked with passive radiators for over a decade. From our experience, we have learned that the lower the weight added to the passive radiator, the more agile and nuanced the bass response becomes. While adding more weight allows the speakers to reach deeper bass levels, it comes at the cost of a "muddier" bass response.

The development process for the E50 has been significantly longer than for any of our other products to date. We collaborated with multiple engineers and did extensive listening tests, to ensure we were fully satisfied with the outcome. Our speakers have always been objectively high-performing, so how they measure is a priority for us. However, with the E50, we made some compromises in the objective measurements to achieve what both we, and the listening panel, rated as a better overall sound.

We worked through countless prototypes, including modifications to drivers, various crossover designs and components, internal damping, and more. Conducting listening tests for these changes is not an easy task—you must be familiar with the testing rooms, as room acoustics impact sound more than anything else. To ensure our subjective findings held up in different scenarios, we tested the speakers in multiple rooms of different size and character.

Prioritizing subjective taste over objective performance was a decision that we thought a lot about. As a direct-to-consumer brand, we recognize that people often rely on data, testimonials, and reviews before deciding to test the speakers in their homes. We understand that some in the objective HiFi community may be disappointed by this choice, but for those who value the objective performance highest, we recommend our active speakers, which are flexible and objectively superior to just about any passive speakers.

We want to be open and transparent about our development and decision process, so we would like to share some of the objective data on the E50 development process with our customers. So, if you are into all the technical details, you will find a lot of interesting information below.

Laying the foundation.

The first designs were based on 3 variants of a more conventional crossover design First we built a 4th order on both tweeter and woofer, which is a pretty common design choice on 2 way standmount speakers. This allowed for a really low crossover point with the new large and capable Scanspeak tweeter that is further helped by the waveguide. The result was a nice foundation, for an objectively well performing speaker:

The second iteration was with a more standard crossover point, which resulted in more pronounced phase issues at the crossover point, when looking at the vertical plot :

The third variant of the first drafts were a 1. order crossover, where you let the woofer and tweeter slowly drop in response over the crossover point. This crossover design is rarely used as it requires very good drivers that are well-behaved, far out from their normal operating frequency band. The Purifi woofer we use on the E50, is one of the few woofers that does not struggle with breakups, so our idea was to test this out, and take full advantage of the excellent performance of the woofer:

A bit about how we do some of our listening tests

With our setup in our listening room, we could swap between these crossover designs within 5 seconds. When conducting subjective A/B tests, the time between the comparisons is crucial to keep as short as possible! The tested designs were done in DSP, but constructed like you would do a passive crossover. This is to exclude any variations of crossover components and their tonal signature, all that come much later in the process when choosing individual components.

We were usually multiple people in the listening room, but only one knew what crossover design was used. People were placed differently in the room, with seats swapped, so all could experience the changes from different listening positions. There were multiple tests conducted over many days, both with single and multiple persons present, all varying in experience.

The surprising result and final measurements.

The result of the test was very surprising! There was a big contrast between the 4. orders designs and the 1. order design, with the 1. order design being everyone's favorite by a very significant amount. The general description of why it was preferred, were summed up to it being much more relaxed and easy going, without a big notice of changes in tonality. It was not considered “warmer” sounding, it just felt more natural and less constrained.

We did not expect the result, but decided to go with our subjective preferences. And over the next 8 months, we worked on multiple adjustments to find a crossover design and components selection that tonally, brought out what we wanted to achieve with the E50. We ended with a design using a 1st order filter on the Purifi woofer, only using one component in the signal path, being the Jantzen Crosscoil Foil inductor. For the tweeter, the end result was a 3. order filter. This crossover design has an easy impedance load of minimum 4.9ohm at 160hz, so the E50 does qualify as an 6 ohm speaker.

We did not expect the result, but decided to go with our subjective preferences. And over the next 8 months, we worked on multiple adjustments to find a crossover design and components selection that tonally, brought out what we wanted to achieve with the E50. We ended with a design using a 1st order filter on the Purifi woofer, only using one component in the signal path, being the Jantzen Crosscoil Foil inductor. For the tweeter, the end result was a 3. order filter. This crossover design has an easy impedance load of minimum 4.9ohm at 160hz, so the E50 does qualify as an 6 ohm speaker.

Final words.

Objectively, the E50 won't win any gold medals. But it's hands down the best subjectively sounding speaker we have done to date, and we feel it is worth the compromises to the objective performance. But don’t take our word for it, take a listen, and form your own opinion about its sound! We are super proud of the end result, and we hope you have enjoyed this insight in the process and our thoughts behind the E50 speakers.

Enjoy!