Eikona VTL loudspeaker from BK Electronics


Following on from the review of the BK Electronics VTL kit, we are pleased to be able to announce that BK now have a complete VTL speaker system available.

The loudspeakers are supplied in white or black, with satin or piano gloss finish and are fitted with magnetic, clip-on grilles. The result is very elegant.

Prices are £894.95 for satin finish and £1014.95 for gloss.

Full details on the BK website.


A history of Ted Jordan’s VTL Loudspeaker

eikona kit pair

Following on from last week’s customer testimonial to the BK Electronics VTL kit, we thought we’d go into further detail about the evolution of the design.

Ted Jordan designed the VTL loudspeaker enclosure in the early 1990s. It used the Jordan JX92S full-range drive unit and saw commercial success as the Konus Essence. It has enjoyed a long life among manufacturers and DIY constructors, and continues to do so with the arrival of the Jordan Eikona 2.

The transmission line loudspeaker is an evolution of the acoustic labyrinth, first produced commercially by Stromberg Carlson in the 1930s. Arthur Bailey added a port in 1965 (Non-Resonant Loudspeaker Enclosure Design, Wireless World 1965) and a new enclosure species was born. The advantages of the transmission line over a reflex or sealed enclosure include more extended bass, better suppression of resonances and greater power handling.

The basic idea is a speaker at one end of a pipe with a hole at the other. The pipe may be more or less heavily damped depending on design. The VTL is a type of transmission line known as a coupled cavity. The rear of the drive unit fires into a cavity which feeds into a long, damped pipe. Above a certain frequency, the cavity decouples the driver from the pipe and the enclosure behaves like an optimised sealed box.

Robert Fris is generally credited with inventing the coupled cavity TL with his Daline (The Daline, A Decoupled Anti-resonant Line Loudspeaker, Hi-Fi News, November 1974), but in fact Ted Jordan described something similar four years earlier. Ted’s article for Wireless World (Loudspeaker Enclosures, January 1971) showed the evolution of the infinite baffle via the sealed box, reflex and horn to a box with long, damped line (see diagram below).

More recently, George Augspurger’s AES paper (Loudspeakers on Damped Pipes, JAES, vol 48 no. 5, 2000) on computer-modelled TL alignments concluded that the coupled cavity is a very successful option.

The Eikona VTL remains as Ted envisaged it; a compact, floor-standing enclosure which is smaller and easier to accommodate than most transmission lines. The wide baffle goes against the modern trend of narrow-fronted enclosures, but it gives more weight and realism to the lower registers, particularly on piano and voice.

Ted enclosure evolution

BK Eikona VTL transmission line

VTL 04.1

Ted Jordan’s VTL transmission line remains our most popular enclosure for the Eikona 2 full-range loudspeaker. It is a compact,floor-standing design which is 30 cm wide but only 10 cm deep and very room-friendly. It is perfectly happy working near walls and room boundaries and is a neat solution to high quality music in the home.

One of our customers, Steve, has just completed a VTL kit from BK Electronics. Steve is a very experienced hi-fi enthusiast and has owned some of the best loudspeakers available, including the famous QUAD ESL63. We’ll let Steve take up the story as he began auditioning the Eikona VTL:

I’ve only had about an hour’s listening, I started with the subwoofer frequency sweep off YouTube to just see how low it would go, and it does go low! Solid output to below 40Hz and the lowest frequency reproduced is 32Hz and this is from a 4″ driver…

“I listened to a selection of my test tracks to listen for various different aspects of the sound quality. … Being a single driver speaker with no crossover to muck things up, the clarity and transparency are crystal clear and uncoloured. The stereo image and focus, even with just a few feet between the speakers, is superb.

“The midrange – particularly vocals and solo instruments like piano – have an amazing clarity and naturalness. Every aspect of their performance is as good as if not better than anything I’ve had before…

“I must admit to be a bit in awe as to what a 4” driver is capable of; these things reproduce percussion unlike any other speaker I’ve heard, drums and rim shots are so crisp and powerful, it’s a revelation, as for bass, these transmission line cabs just can move so much air, it seems like alchemy!

“The old adage of hearing stuff you’ve never heard before in your music is certainly true with these, the size of the soundstage and imaging is the best I’ve experienced in 40 years interest in hi-fi.”

Part 2 looks at the background to Ted Jordan’s VTL enclosure. Meanwhile you can see the plans here.

VTL 02.1

MLTL30 Eikona transmission line loudspeaker

Eikona MLTL30 v2

The MLTL38 transmission line loudspeaker is very popular with users of the Jordan Eikona 2 fullrange driver.

The name MLTL (mass-loaded transmission line) arises from work by Martin J King, comparing computer-generated loudspeaker models against built and tested transmission line speakers. Martin produced a set of MathCad spreadsheets which enabled users to virtually build, refine and measure of this type of enclosure.

The MLTL is an enclosure dominated by a combination of quarter wave resonance and port mass. Adding a port allows the designer to shorted the transmission line’s length. Other parameters can be adjusted in the software to arrive at optimum results. One advantage of the MLTL is that the area behind the speaker unit can be damped, suppressing mid- and high frequency reflections, in a manner which would be detrimental in a typical reflex enclosure.

It’s a system capable of very high quality results. The new MLTL30 is designed specifically for the Jordan Eikona 2. It doesn’t go as low as our MLTL38 but the shorter cabinet may be more domestically acceptable. The graph below gives the MLTL30’s calculated response.

Plans for the Eikona MLTL30 can be downloaded here. As always, if you build an enclosure we are happy to see photographs and feature them on our Facebook page.

ML30 blog graph

Eikona 2 Djinn Open Baffle speaker


The Open Baffle (or dipole) loudspeaker has a long history, with famous UK examples from Wharfedale and QUAD. At its most basic, an OB speaker consists of a drive unit on a flat board, the rear of the driver being open to the air. Whilst this may eliminate the colouration characteristic of some box enclosures, it has the disadvantage of introducing an acoustic short-circuit; sound from the front of the speaker saunters round to the back and happily cancels out all sound below a certain wavelength. The wider the board the speaker is mounted on, the lower in frequency the cancellation will take place.

In recent years, there has been a resurgence of interest in Open Baffles, particularly in the DIY community. At the end of 2016, one of our customers contacted us with details of his OB design, using the Jordan Eikona 2 and a Dayton Audio pro-audio 38 cm woofer.


It is a distinctive design, featuring slot-loading for the woofer and an unusual edge-of-baffle position for the Eikona 2. At first sight, it looks as though the design cannot possibly work. But the designer has begun with specific aims and a carefully considered rationale to achieve them. The end result is both clever and genuinely interesting.

The Djinn OB Project is currently being documented on this DIY thread on Audiocircle.


Firm Foundations – the Concrete Baffle

This is a contributed blog from Jonathan Espley of Matteis Loudspeakers. He has been a long-term user of Ted Jordan’s full-range drive units and is a passionate advocate of ultra-rigid, concrete baffles. These concrete baffles appear in his own range of loudspeakers but are also available to home constructors. Jonathan describes the background to their development.


 Back in April 1982, Hi-Fi News & Record Review published an article, Tone Arms And The Twist. It suggested an alternative way of making a pickup arm. The idea was to use strategically-placed mass to provide stability for the cartridge at audio frequencies. In so doing, it removed the need for an ultra rigid arm and highly engineered bearings and virtually eliminated structural resonances. I rebuilt a Hadcock Unipivot arm to test the principle and it worked superbly well.

The loudspeaker drive unit and cabinet has a lot in common with the moving coil cartridge and pickup arm. The arm/cartridge converts mechanical energy into an electrical signal whereas the loudspeaker converts the electrical signal into a sound wave. In each case, the transducer should be held absolutely stable at audio frequencies.

High end pick-up arm manufacturers go to great lengths to engineer the arm to be as rigid as possible in order to extract maximum information from the record groove. Loudspeaker manufacturers design some superb drivers only to stick them in a highly resonant wooden box.

It’s not difficult to see where the main problem lies with conventional loudspeakers. The cone is driven in a backwards/forwards motion to generate the sound wave. This puts great pressure on the baffle to resonate in the opposite direction to the movement of the cone. Any movement due to flexure must be subtracted from the cones movement. Hence there is an inevitable loss of energy.

When it comes to side panels, they are solid in the front to back dimension and any resonance does not directly affect the motion of the cone and so has minimal effect compared to the baffle. I have built speakers with concrete sides and, believe me, it’s not worth the compromise as it’s very difficult to get an acceptable finish. 


I started experimenting with a concrete mould for the front baffle then tried reinforcing it to obtain greater rigidity. To cut a long story short, I ended up with a mould (shown below) that has reinforcement right across the baffle. The concrete does not take the strain as it is not stable enough at 30mm thickness. Every improvement to the reinforcement brought an improvement to sound quality. The main difference is a sense of presence to music. Stereo image is more sharply defined, giving a much more realistic presentation of a musical performance.

There is still a small residual resonance as the pressure to drive the cone against atmospheric resistance is so great that the whole enclosure moves slightly. It helps if the enclosure is deep and narrow with the base as deep as possible, with spikes to pierce the carpet.

I have a new enclosure design formulated which I hope will overcome this problem. It has some novel features and will be the basis of a future blog.


Aurora 400 2-way system


One of the more unusual projects we’ve been involved with this year has been an two-way Aurora 400 system.

The initial enquiry came from a long-standing Jordan customer who was using one of Ted’s Linear Array designs. Each array consisted of four JXR6HD units crossed over to a JX150 Jordan bass system.

The electronic crossover was custom-designed by the customer and BBC engineer and is a first-order design, -3dB point at 275Hz. Our customer was intrigued by Ted’s claim that the Aurora reflector loudspeaker produces better stereo than the already superb imaging of the Linear Array.

As with all the Jordan Aurora designs, the cabinet was bespoke. Our customer chose contrasting veneers for the cabinet and reflector, an effect which is both striking and attractive.

The Aurora 400 takes the place of the Linear Array and is wall-mounted just above the bass enclosure. As sensitivity of the Auroras is lower than the array, gain adjustment of the crossover was needed to equalise the frequency response of the entire speaker system.

Our customer has connections to the audio industry and is a very critical listener so it was gratifying to receive his comments on the Aurora 400 system:

I’m impressed by the Aurora performance as bass reflex full-range speakers but as I don’t need the bass frequencies, I can put in much more stuffing than would work with a bass reflex design … “

“Impressions of the Aurora speakers is that they are better than the line array … the Auroras are quite special; very clean … they have better presence than the JXR6HD line array, so I’m impressed with the sound!”

For more details of the Jordan Auroras, see here.


A New Jordan Eikona Loudspeaker

Taliesin Side-by-Side

We have just received exciting news from our American dealer, Ars Harmonia.

In addition to selling the Jordan Eikona full-range drive units, Ars Harmonia manufacture high-quality loudspeaker enclosures. They have had great success with the Jordan VTL and now they have launched their own, exclusive design, the Taliesin.

This loudspeaker follows a similar form-factor to Ted Jordan’s elegant VTL transmission line but is slightly larger at 99 cm tall, 34.5 cm wide and 15.24 cm deep.

The unique Taliesin enclosure was designed by Paul Kittinger using Martin J King ‘s famous MathCad loudspeaker  modelling software. The cabinets – one in solid cherry with bird’s eye maple and the other in walnut – were hand-built by Bruce Pea.

The first two pairs are already at dealers. Contact Bruce at Ars Harmonia for more details.

Walnut Taliesin - No Grill

Classical Jordan DCR


A very nice email arrived this week from one of our customers. He has just completed building the Jordan Eikona DCR loudspeaker design and is thrilled with the results:

“They sound fantastic. Very natural on the human voice (my wife is a classical singer, so listens to lots of song, opera, etc). They fit really well in the kitchen, either side of a chimney breast. Sound is seamless, much improved on the stack of 4x 50mm Jordan units & bass each side they replaced. Very much enjoyed making them, now enjoying listening to them and plan to make another pair…”

The DIY plan for the Jordan DCR enclosure is available on our website here


Loudness Wars


For over a decade, music producers have been fighting a loudness war.

Louder is more exciting and superficially appealing. This is important when you are competing for the attention of the music-buying public. It also helps overcome ambient noise if you are listening to music whilst in a vehicle.

Rather than just boost the ultimate sound pressure level of a piece of music, the trick employed is to bring the quiet parts up to match the louder sections. In this way, the overall dynamic range is reduced. The listener loses a dimension that is part of the complexity and richness of music.

This may be one reason why some enthusiasts prefer original vinyl releases to CD or streaming counterparts; it’s nothing to do with the carrier format, it’s how the music has been mastered. It’s certainly true that in some recordings we’ve explored, the remastered, more modern release can lack the dynamic range of the earlier – to the extent that we default to the earlier version wherever possible.

Here is an excellent primer on the loudness wars, viewed from the production perspective and published in the recording industry magazine Sound-on-Sound.