Product: EE 150 electrostatic hybrid speaker
Manufacturer: Van Medevoort - Holland
Cost: e4500 + VAT
Reviewer: Geoff Husband
Reviewed: December 2001

Introduction

Anyone following my series of loudspeaker tests may have noticed that I've tried to avoid the 'classic' ported box norm and go instead for more fringe designs. So we've had kits, sub-miniatures, TQWT's, horns, transmission lines and now at last an electrostatic. I'll also add that speakers are very characterful devices generally and that my reviews try to pick apart the performance of a speaker and pin down it's essential strengths and weaknesses in my system, and equally importantly my room, rather than to simply eulogise it's better points. Those used to the usual 'soft' reviews much of the paper press produce need to bare this in mind.

What's an electrostatic?

99% (OK I'm guessing) of commercial loudspeakers rely on dynamic drivers where a cone is driven back and forth by a 'motor' consisting of a coil and magnet - in effect a short throw linear motor. These things can run from pence to £1000+ for exotic fullrange drivers, but all use the same principle. There are alternatives, Mangers, Plasma tweeters etc, but only one has gained any major hold in the loudspeaker (and headphone) market and that is the electrostatic.

Ever rubbed a balloon on your hair and stuck it to the ceiling? (wot no kids?). It sticks because the balloon has taken up an electrostatic charge which attracts it to things with a different charge (e.g. the ceiling). It's a weak force and you'd think that compared with the sheer clout available from a big coil/magnet system it'd have no use. But then Quad commercialised it with the stunning ESL57 - over 40 years ago... By using a very thin plastic (mylar) film and giving it a charge, then discharging it, it could be made to move back and forth, if driven by a music signal this will produce an audible sound. In the case of the ESL57 this sheet of film is nearly a metre square, so though the movement is small and the force relatively weak it moves enough air to produce reasonable music levels.

Hey but why bother? Well the film is very, very thin and almost weightless, thus it stops and starts like nothing (and I mean NOTHING) else. The response to an impulse is immediate and then stops with no overhang, in comparison a conventional driver needs time to accelerate forward then springs back to wobble a couple of times before stopping. The only drivers that come close are very light full-range units with massive magnets, such as the Lowthers and Loth-x drivers and the Manger driver.

The other big advantage is that an electrostatic is a true 'planar' driver, that is the whole diaphragm moves forward at the same time* meaning that there's no time delay between different parts of the driver. With a conventional dynamic driver the centre of the cone is driven and the wave form propagates outwards like ripples on a pond, introducing time delays and various effects as the cone flexes to accommodate those waves. True 'pistonic' motion is marketing hype, it doesn't exist in dynamic speakers no matter how stiff they claim to be...

And lastly the Electrostatic, being a planar speaker, needs no box. So at a stroke all the problems associated with box loudspeakers, resonances, overhang, the difficulty of tuning the box etc are banished.

The down side.

With a sales pitch like that you'd wonder why anyone bothers with anything but an electrostatics. Indeed their fans would argue that their biggest disadvantage is cost so that all hi-end speakers should be electrostatic rather than dynamic - leaving the motor+cone brigade to fight over the mid -> cheap end of the market.

Ah! Would that it were that simple...

A quick glance at any full range electrostatic, and Quad are one of the few companies making them, show them to be big rectangular panels - the '57 the size of a big portable convection heater, the 63 the size of a front door. They are in effect 'flat baffles' and as with any flat baffle the bass roll-off is determined by the smallest dimension of the baffle, below which the front wave is cancelled by the reverse phase of the rear wave. So in order to get any kind of bass response the panel needs to be BIG, even the monster '63's roll off quickly below 50 hz.

So they need to big, not a problem if they could be used hard up against a wall, but no - an electrostatic is a 'dipole', that is it radiates equally forwards to the listener and backwards, (in opposite phase) away from the listener... So a large part of what you hear from a big electrostatic is in fact reflections from the rear wall, which may, or may not be in phase, will be dependent on the wall covering, will vary wildly in intensity depending on frequency and will be very dependant on where the listener sits. This will be particularly important in relation to bass and lower midrange performance as these frequencies are more easily reflected. So properly placed electrostatics are often to be seen a 1/3 of the way down a listening room with blankets covering a rear wall, hardly ideal in a domestic environment. In fact a full-range electrostatic is probably more demanding in terms of positioning than any other speaker.

Then there's the problem of dynamics... Though the film is very light and large it doesn't move that far and in the final analysis no electrostatic is going to shift the amount of air a big dynamic speaker will manage, let alone something like a big horn. This limits dynamic range and absolute spl's, real electrostatic junkies stack several 57's in an effort to overcome this.

So to sum up an electrostatic should be lightening fast, uncoloured and its preservation of phase information make it an open window to the atmosphere and soundscape of a piece. On the other hand it'll be expensive, big, very dependent on positioning, bass light and lacking in macrodynamics.

In an ideal world it ought to be possible to get the best of both worlds and several companies have combined dynamic and electrostatic drivers to produce a hybrid.

The thinking behind this is seductive. Use an electrostatic element to cover only the mid and treble area. That way it can be smaller, the rear radiation made up only of higher frequencies which cause less room reflection problems and you leave the classic advantages of the electrostatic to come to the fore. At the same time a meaty bass system based on dynamic drivers provides the slam and bass extension.

Seductive - but with one big snag. Using two totally different speaker units, with totally different characteristics makes such designs a nightmare of tuning compromises, but get it right and the result could be spectacular...

The Van Medevoort EE 150

Construction

The EE 150 uses a tall thin electrostatic 'pod' on top of a 'bass bin'. The pod has an electrostatic element a mere 3cm or so across. Immediately this tells us that the element is designed to work in the mid-range and treble, the bass and even lower-mid is left to the 'bass bin'.

This bass bin consists of an active bass system, the amplifiers driving two 6" drivers per box with a downward firing port. As one of the drivers is hidden in the box it looks like VM have used some sort of 'bandpass' configuration, something which if done correctly can offer bass rolloff though I suspect an active crossover is more important.

Finish is perfect - but very much 'pro' in design. The drivers are protected by metal mesh and the covering is a sort of textured plastic/paint, all this combined with a 'computer white' colour scheme makes it look more like a very upmarket computer speaker system than a domestic hi-fi speaker. In my 300 year-old, stone built house the effect was like plastic wheeltrims on a vintage Bentley! In a more contemporary listening room the speakers could fit in nicely, here Kate's first reaction was "well they're not staying in my living room" - negative WAF doesn't remotely describe the effect... The pods on top can be angled towards the listener independently of the bass units but look so drunken doing this that I didn't even bother to show Kate...

In use

Packaging is excellent and it's the work of a moment to take out the electrostatic elements and bolt them to the bass unit using the supplied spanner. The bolt runs right down through the bass bin and are tightened at the bottom.

Here's a moan... The speakers are very tall and narrow. They also have a flat bottom with no threaded inserts for spikes or feet. VM recommend cones/spikes Quote "Placement on spikes is mandatory for stableness" - personally I find their absence baffling. However, adding cones or spikes further narrows this base. The result is the most unstable speaker I've yet come across. This isn't a problem sonically, the critical front/back footprint is long, but if you have carpets, small children, pets or even strong drafts (OK I exaggerate - a bit) you're going to be picking the VM's off the deck with monotonous regularity...

I have small kids and so unstable are the VM's I was forced to find a solution. In the end I used a granite slab and 'glued' the speaker to the slab using big lumps of blue-tac. The result was a total success both sonically and in terms of the speakers life expectancy... VM need to offer some extension to the footprint for 'normal' people... (*The manufacturer strongly disagrees with this comment)

Having sorted that little problem I plugged each speaker into the mains - it's an active speaker after all - and hooked it into my main system.

Sound...

When everything clicks this is one of the most open, detailed and uncoloured speakers I have had the pleasure of listening to. At their worse they can be disastrous.

I hope VM will forgive me for starting with the bad because as the EE 150's are so unusual it's important to understand where they are coming from. It's not inconceivable that you will be faced by a demonstration where the VM's sound like junk and that would not be doing them justice...

So - lets just treat them as a normal speaker, slap them into the system, give them 60 cm of space behind and settle into my normal listening position - fine tuning can come later. Nightmare. The most horrible boomy bass swamps whatever the electrostatic element is trying to do, bass bloom doesn't describe the half of it... It's slow and muddy, resonances reaching well into the mid range and nothing in the way of true deep bass. It sounds like a very cheap home-cinema sub turned up too loud - YUK!!!

I'm not even going to go on with this, there's no point in listing the effect with different tracks because the sound is so bad I'd rather listen to a ghetto-blaster.

All these problems are down to positioning. The bass box's port fires downwards, the bass drivers are close to the ground and so speaker/floor interaction is much greater than with a 'normal' floor stander where the bass driver is 1m above ground level. My listening room has typical floor/ceiling resonances and no speaker has ever wound them up like the VM. Playing a 200 hz tone and walking up the room caused the tone to boom and disappear as the direct sound was reinforced then cancelled in turn by the floor/ceiling interaction. Other speakers show a similar effect but nothing like as strongly. In my normal listening position this swamped the sound. Moving a metre forward produced a much better balance, 1.5 m and the sound became stripped dry and harsh. Interestingly the best balance was found at the manufacturers recommended ratio of a triangle with the listening distance being 1.5 x the distance between the speakers. Having sorted that it became apparent that the VM's were not too sensitive to the distance from the back wall, though at least a full metre proved the best compromise.

All the comments on the performance of the 150's are from the 'hot spot' listening position - anywhere else and the sound varies from mediocre to bloody awful.

Regular readers will know I'm a serious Nirvana fan. As you'd expect that involves a lot of banging and crashing, but one Album, the MTV 'Unplugged' is very different... In this case 'unplugged' probably means 'no major mixing desk' as a lot is electrified but it is also subtle and intimate - strange how such a commercial happening can give an insight into a performance and on a superficial level into the characters of the group members themselves. Through the VM's you were taken into that small - studio, they really gave you that 'you were there' feeling, so much so that you sometimes feel an intruder in overhearing the quiet verbal exchanges between members of the group. I've heard this sort of insight twice before, once through the Loth-x Polaris and through headphones. The former were close to the VM's but there was still a veil between me and the artists, in the latter case the detail and insight was very similar but the totally artificial effect of 'cans' never made you feel you were present.

Time and time again, though a variety of recordings I was taken deep into the mix, the cliché of the 'open window' being wholly appropriate. As well as studio 'asides' this effect manifested itself in extra layers of backing vocals, or the identification of said singers. Sometimes an artist will overdub or harmonise with their own voice (Bowie does it a lot) other times a session musician will do the job, the VM's made such trickery obvious.

Soundstaging was good without being earth shattering, I'd expected such an uncoloured source to do better considering the high standard elsewhere. Tears For Fears - 'Seeds of Love' has a lot of studio effects which were laid bare, but the artificial depth generated was somewhat less than with the Cabasse Sloops, though the width was fully equal.

Played at moderate levels the standard was generally very high (in absolute terms), as the volume increased the delicate balance between the electrostatic element and the bass became less happy, the bass bin adding colourations further up the frequency scale, muddying the superlative electrostatic component - here perhaps the dynamic limits of the latter are being overtaken by the former? Often this effect could be balanced by moving the listening position a fraction - the ultimate tweek?

Given music that didn't tax the dynamic extremes, 'Take Five' being a prime example, it was almost impossible the fault the integration, Dave Brubecks piano being particularly seamless, though perhaps the cymbal lacked the last ounce of 'shine'. Female vocal too was delicious, Ricky Lee Jones being at her simpering best, but Baritones could catch the speaker out as they crossed from one element to another.

At the very bottom end, the speaker was a little bass light, but as the bass response was so even above this point it really didn't detract, though fans of the mighty concert organ might consider a sub to bolster the sub 40 hz output. For the rest of us the bass was fast and tight though never quite matching the impossibly high standard set by the Loth-x Polaris (albeit even more bass light).

Achieving the impossible?

VM have chosen to try and integrate the most accurate and uncoloured driver known to man with a ported bass box - albeit of high quality. Not only that, they've tried to do it right across the frequency range, at all volumes and throughout the room - and they've failed - OF COURSE!!! The character of the dynamic part inevitably changes in a different fashion to the electrostatic element as volume increases - the former gaining more and more resonance's as the box plays a bigger and bigger part, the latter perfect until it becomes dynamically challenged. Likewise the way the two parts interact with the room is inevitably different. The skill is in balancing the compromises in such a way so that for the majority of the time, and for the majority of music those compromises don't intrude. In this VM have succeeded with the proviso that they are very room and position dependent. My only criticism apart from the spikes/cone issue would be that perhaps if the bass unit were given level controls it might make integration easier - the thing is active after all so this should be very easy and cheap to implement?

Conclusion.

There are many ported speakers around at half the cost of the VM's that manage to be perfectly adequate (and more) for most people. To justify such an elevated price a speaker needs to do certain things exceptionally well, even at the cost of being 'difficult' - this is the unspoken truth of the 'high-end', where often some things are sacrificed in order to achieve 'perfection' elsewhere - horns being a classic example. The VM's do things, noticeable sheer transparency, better than anything else short of another electrostatic. This demands high quality ancillaries, and a commitment beyond that. These are speakers for the dedicated Audiophile, one who can allocate a room to the music system, who doesn't mind sitting in a particular place or even listening at a particular volume. For such an individual the VM EE150's offer headphone like detail and transparency in a room. If your listening room is simply a living room where the hi-fi happens to reside then perhaps better to look elsewhere.

Postcript

The review period became unexpectedly extended and this coincided with my setting up a second system in my bedroom. This is the same size as the living room, 6x4.5 m but with very different furnishings and floor material. Here I used an 8w 300B SE amp rather than my 30w Audions, however in that environment volume restrictions were less important. The effect was much drier, much of the bloom when in the wrong listening position vanished to be replaced by a rather lightweight presentation. Imaging was superior to the main system and the sound took on a particular beauty. But at the same time the 'beef' was missing.
This brief experience confirmed my belief that the VM EE150 are very system, room and particularly position dependent. To misquote the 'girl with the curl' "When they're good they're very, very good, but when they're bad they're horrid" :-)

*I know the '63 is more complex than that but there isn't scope to go into it here...