"What a refreshingly honest blog about listening to music through hi-fi. So happy to see views based upon the enjoyment of music rather than so-called sound 'quality'." - Peter Comeau, Director of Acoustic Design at Mission / Wharfedale

Monday 27 June 2016

Dealer Visit: Hifi Lounge, Bedford. Chord Mojo DAC Review

This review is as a result of a visit to this dealer to pick up a demo pair of PMC speakers and is therefore written as a customer, not as a reviewer as such.  Hifi Lounge were not aware that I would be writing about the visit (in fact, neither did I at the time, it occurred to me later that it might be something worth writing about).  

Are the days of the high street hifi specialist numbered?  House of Linn is a large Victorian end terrace house in a residential area of a town just outside the M60 Manchester orbital, Cymbiosis are in converted farm buildings and there are many other examples.  As hifi polarises into mass market convenience and high priced specialist products, with those companies and dealers in the mid-range probably feeling increasingly squeezed, there is no need for the higher end dealers to remain in the high street.  “Passing traffic” is no longer likely to just drop in, rents are very high, customers want somewhere easy and convenient to park, and most auditioning is based on pre-arranged appointments.  Buying quality hifi is now more likely to be a long decision process that’s best done in comfortable, more home-like surroundings in a quiet location with none of the distractions and hassles of a town centre.
Which brings me to Hifi Lounge, based just outside Bedford.  The approach is along a gently winding country road and a smooth gravel drive that feeds a number of “units”.  But these are not units of the industrial variety, but converted brick-built former farm buildings.  The car park is surrounded by trees, well-kept grass and hedges.  As soon as I arrived I felt relaxed and I hadn’t even got through the door.  Hifi Lounge is identified by a discrete logo on one of the buildings and you enter through a lowish wooden door.  Paul greeted me with a friendly smile and handshake.  He’s an easy bloke to get on with, as is his partner Wendy and it feels more like going to visit some friends, or perhaps genial B&B hosts, rather than a retail environment.

On the left is the “office” area with desk and some stock.  This is also online central for web content and correspondence.  Straight ahead is the staircase and on the right is the smaller dem room and, importantly, the kitchen area.  A good mug of proper tea was soon in hand – appropriately in a PMC branded vessel.  This smaller dem room is arranged with kit along the longer wall and a sofa opposite, thankfully a good distance away from the wall behind the listener.  A good number of items of kit are lined up on racks and there are some pairs of speakers – one pair set up for listening, the others along the shorter end wall.  On the day of my visit there was much evidence of Naim, Rega, Bryston, Arcam and PMC in this room.  Whilst being the smaller room (I’m guessing its about 5m x 4m), it does represent a very realistic size for many homes and will therefore help a good number of customers get a decent impression of a realistic set up.  D├ęcor is both modern (with wall art mural), casual and comfortable.  The ceiling is lowish, giving a cosy feel.  Nice.

When I was there, another customer was listening to some amp options in the, much larger, upstairs dem room.  This is slightly larger in floor area but also enjoys a high vaulted ceiling with exposed beams.  There’s a projector available and this room will better suit larger speakers, customers with larger rooms and, at a guess, those with larger wallets too.  I appreciated the 12” picture frames containing album sleeves – apparently these are changed from time to time and were recently all filled with Bowie albums as a mark of respect and appreciation.  I didn’t spend much time up here as there was a dem in progress and we didn’t want to disturb the other customer.  Back downstairs and Paul and I chat for a while about music choices, my current system, why PMC, what I was looking for in terms of a performance upgrade etc.  Paul comes across as genuinely interested, willing to discuss stuff he doesn’t sell and understand its merits and is clearly enthusiastic about the location and facilities he has to offer customers.

The PMC speakers are the demo units, so Paul brings the boxes and we pack them up together, still chatting about music and hifi.  Shortly afterwards the other customer comes down and joins in the chatter and it seems we have some work colleagues – current and past - in common.  I live in North Wales and have worked in Scottish, Yorkshire and London locations and here I am discussing colleagues with a stranger in Bedfordshire.  Small World and all that.

Given that I’ve never done any business with Hifi Lounge before, I felt very welcome and that Paul was interested in what I’m looking for.  On top of that, with a refundable deposit sorted, Hifi Lounge were happy for me to take their pair of Twenty.26 speakers away to North Wales and audition them for a week in my own system.  Doing anything other than this would’ve been pretty pointless really, using a different room and electronics from a completely different supplier (ie, in the shop) would not have provided much information really – certainly no benefit over my existing experience with the 26s at hifi shows and from magazine reviews.  Hifi Lounge were positively keen for me to ensure that I got a good long home audition before spending with them.  There was no quibble or doubt about trusting me with the speakers, even as a stranger – they clearly understand their customers’ needs and how to support those needs. This is a great way to engage a customer and gain their trust, as well as their long term repeat business.

Once the speakers were loaded up into the car, there was one more thing I wanted to try whilst I was there.  I’d taken my FiiO X3 portable hi-res FLAC player and my Audioquest Nighthawk headphones along as I wanted to give the new Chord Mojo DAC / headphone amp an audition, and knew that Hifi Lounge are Chord dealers.  So Wendy took me over to the headphone room, opened it up, set the lighting ambiance and let me get on with trying the kit.  But first, what about the room?  A very long, slim room, totally dedicated to the pursuit of high quality sound strapped to your head.  I’m guessing, but the room is probably around 8m long with all the kit arranged along one wall, with tall narrow windows down the opposite wall.  The kit wall has a waist high shelf with headphone amps from one end to the other – above this is an equally long row of high quality headphones on headphone stands.  All the well-reviewed kit is there – Audioquest, Grado, Oppo, Audez’e, STAX, Audio-Technica, Sennheiser, Shure, AKG, BeyerDynamic etc. etc.  What an array of choice!

I settled into one of the sumptuous leather wing backed chairs with the FiiO / Mojo / Nighthawk combo and lined up some tunes.  Wendy left me to it, just saying I should take my time and come back to the main shop when I was ready.  The first thing that struck me about the Mojo is how tiny it is.  Somehow, even after reading that it’s about the same size as a pack of cards, it still came as a surprise that it is, actually, the size of a pack of cards.  I suppose I’m just used to so much hyperbole in the press these days that I thought this was rhetoric for effect rather than reality.  So there it is, tiny.  But beautifully built – the satin black anodised aluminium casing feels solid and machined (as opposed to pressed) – it feels much more expensive than the list price would suggest.  The Mojo accepts normal USB and coax SP/DIF digital inputs, but also those from iPhones and Android – so great for being on the move. The controls are OK – you soon get used to what long press vs short press does and the action is solid and “well oiled” so to speak – the only downside being the rather bright colours which could be distracting in a darkened room.  But once the tunes start playing this rather pales (sorry!) into insignificance.  

I hooked up the FiiO using the coaxial digital output and set the Mojo to a sensible listening level – so not too loud.  Last time I heard a Chord DAC / headphone amp was when I bought the Nighthawks – it was the larger and more expensive Hugo and I wasn’t impressed.  The Hugo receives very good reviews but sounded artificial to me – certainly the same headphones being powered by the Audioquest Dragonfly and a Trilogy 931 amp was a much better experience – that combination working well together to provide a more natural, flowing and musical result.  So what of the Mojo?  Well it is most definitely a more enjoyable listen than either of those I tried earlier – there’s oodles of detail, but its refined not forced, it doesn’t sound like you’re listening to something digital, in that edgy, gritty excessive brightness that so many low budget digital products deliver.  This is classy.  There’s slam, deep bass and great timing - the music bounces along with energy but control.  This little box of tricks is a revelation.  At the price it’s an absolute steal.  I don’t have one yet, but once the main system has settled down I’ll be investing, and certainly before some long flights I’m expecting later in the year (and I’ll go back to Paul and Wendy to get mine).  If you’re as old as I am then you’ll understand what I mean when I say I think the Mojo is probably this generation’s equivalent to the NAD 3020 – everyone should have one that’s looking for top quality listening on a reasonable budget.  I’ve heard a lot of headphone amps in the last 12 months, this is easily the one to beat up to at least £1000.  Brilliant.

So Hifi Lounge – great location, great facilities and a warm welcome from Paul and Wendy.  I enjoyed my visit there, which is not normally something I can say about retail experiences.  They’re helpful, friendly, relaxed, clearly keen to let the customer spend time and make their own decisions, they run interesting events from time to time and offer great service, even to new arrivals.  Oh, and one of the best headphone choosing experiences anywhere.

Hifi Lounge have kindly reviewed this post for factual accuracy, but have had no influence on the opinions expressed.

Friday 10 June 2016

Linn Exakt and PMC Twenty.26. World First Review Part Three - Set Up and Listening

Part Three of a Three Part Review

Part One Here

Part Two Here

If you’ve read the above first 2 parts of this mini-saga, then you’ll be aware that we’re part way through the story of moving Audiophile Musings’ system from passive Klimax electronics into Majik 140 speakers towards Linn Akurate Exakt and PMC Twenty.26 speakers.

The Exakt kit was a mix of new and ex-demo and consists of:
  • Akurate Exakt DSM (an Ethernet connected streamer, digital pre-amp and box of tricks that converts all digital signals into Exaktlink protocol before passing this along to the Exaktbox) – AEDSM; 
  • A Cat 7 cable to connect AEDSM to Akurate Exaktbox 10; 
  • Akurate Exaktbox 10 (a digital crossover which contains 2x Linn Exakt engine processors and 10 independent digital to analogue converters (DACs) and outputs 10 channels of analogue ready to be amplified) – AEBOX10; 
  • 6x Linn Silver analogue interconnects connecting the AEBOX10 to the power amps; 
  • 8x channels of Linn Akurate 4200/1 power maps (4200 has 4 channels so after moving from M140 speakers to PMCs, 2x channels are not used for the stereo parts of the system, the 2 spare channels are used to power the centre speaker of the complete 5.1 set up) – A4200/1;
  • 4x 2.5m of Linn K400 speaker cable to connect the power amps to the speakers (initially for the Majik 140s);
  • 2x 2.5m of Linn K600 speaker cable to connect the power amps to the speakers (later, for the PMC Twenty.26 speakers) 
  • Linn Konfig software running on a Windows laptop.

Trevor of the House of Linn came to set up the system, starting with the Majik 140s. We had to do that as the Linn Exakt software filters for the PMCs weren’t available at the time – see Part One of the story for the thinking behind making the jump to Exakt, even before the PMC filters were available. After all the Klimax gear was disconnected, we started on unpacking all the boxes for the new kit and did a bit of shelf dusting whilst we were able. One of the aspects I really appreciate about Trevor’s work is the attention to detail around taking care of the kit. Everything is handled with care and respect, he removes his watch and nothing is left to chance in terms of laying everything out in a logical order etc.
So the DSM is set up on the rack to replace the KDS/2 streamer and the power amps and Exaktbox are installed on the centre rack between the speakers, under the TV. Of course, all installed on Cyrus Isoplats. The Linn software and documentation give diagrams on connecting up the power amp channels to the back of the Exaktbox. Because there are 10 channels on the Exaktbox and because there are many different speakers supported by the software, the connections to the power amps are very much dependent on the speaker in use. So the back of the Exaktbox is just labelled channels 1 to 10 – it’s the diagrams in Konfig that show you how to connect up. Konfig then needs the speaker serial numbers entering and it downloads the correct filter profiles for that particular make and model of speaker. The filters apply all the correct frequency cut-offs and phase corrections tailored through software for the speakers in use. For the Majik 140, channels 1 to 4 and 6 to 9 are used. These Exaktbox outputs were hooked up to 2x Akurate 4200/1 4 channel power amps using Linn Silver interconnects (these have silver coloured sleeves, but the conductors are copper). One power amp was used per left / right channel.

Akurate Exaktbox 10
Linn Konfig is fired up on the laptop and work starts on configuring the system. First up is to select the speakers for the Exaktbox – select the model from the drop-down lists and then enter the serial numbers – choosing which speaker (left or right) will use each set of channels (1 to 4 or 6 to 9). Then all the room information for SPACE room optimisation can be input (dimensions, materials, window positions etc etc), or the existing room information is retained, which is the position we were in. SPACE was left switched off and we spent the best part of an hour re-positioning the speakers in the room. There was only about 10-15mm change in position in the room to get the best sound from their previous position.
At this point, SPACE optimisation was calculated and applied. It was pretty much spot-on – a result which is markedly better than using SPACE in a non-Exakt system. In Exakt, the optimisation is called SPACE+ and is applied in the Exaktbox (rather than in the DS in analogue systems). This uses fewer compromises (for example, the position of individual bass / mid-range drivers and the bass ports are much more accurately modelled in SPACE+) and seems to give a great result. We messed a little with the SPACE settings, but ended up back at those calculated by the system. Impressive.
So the Exakted M140s using Akurate level electronics are a major improvement on the same speakers driven passively by the higher-up-the-range Klimax electronics. Some may find this difficult to take, particularly those heavily invested in Klimax gear. But here we have a system that performs both musically and technically far better and by selling on the Klimax components, actually left me financially better off. Why do I find it better? Well tighter timing, massively better imaging, bass control, a naturalness to the vocals and completely involuntary foot tapping. Given that Linn equipment already sounds very well controlled – to the point where some listeners find them too controlled and lacking in liveliness and wanting them to “let go” more – then its possible to see how Linn have developed Exakt to take this one step further. Did the electronics improve over time? Did they “burn-in”? I’m not sure that they did. Certainly, not enough for me to have noticed. But then it was only the AEDSM that was new – the Exaktbox and power amps were ex-dem and as such would’ve experienced “burn-in”, if such a thing exists with these systems. What is noticeably though, is the warm-up effect. The system sounds great when first switched on, but there’s definitely an improvement at somewhere between 20 and 30 minutes of use. The sound “fills out” and becomes both warmer, deeper in the bass and yet just as controlled. It’s a nice effect, but it would be much better if the system sounded this way from the start. I try to find the time to run the system for a while before sitting down to a focussed music listening session.

What of the PMCs? Well at this point I was kind of thinking the M140s would be around for a while longer whilst saving up for Akubariks. But it wasn’t long (about 3 weeks) and the PMC filters were released. So time to give it a whirl. Some correspondence with Linn suggested that they had found the PMCs a little bright and tiring too and had tailored the Exakt filters to take out a fair amount of treble energy. So the work was done to convert the speakers (see part 2 here), the M140s were replaced by the PMCs.
But its not a straight swap of course – everything was powered down to start with. First, documentation was consulted and the PMC wiring diagram was identified. Now channels 1-3 and 6-8 of the Exaktbox are in action. 2 channels of the power amps were disconnected from the Exaktbox and the speaker cables were changed out from 2x K400 for K600 (3 pairs of cables in one sheath). Next the AEDSM and Exaktbox were powered up (NOT the power amps) – once they were visible on the network then Konfig was opened on the laptop, the correct PMC speakers (curiously, there is choice of 1x Twenty.26 or 2x Twenty.26 available – this is for those who wish to use one Exaktbox per channel – apparently for sound quality purposes, but I doubt that’s something I’m going to consider in the near future – one of the major benefits of the PMCs is the ability to run them off one Exaktbox, including the 6 channel Klimax version). So 2x Twenty.26 was selected and SPACE switched off. I then connected up the bass power amps to the bass drivers and powered up, listened to a couple of minutes of music to check bass information was coming out of the bass drivers. Then the mid-range was added, checked and finally the treble was connected up and checked for treble output. This sequence is important to make sure that drivers are not damaged. The great news was that everything worked as it should. A major relief that the speaker conversion has been a success.
The system was then played and speaker positioning commenced, taking about an hour to start with, then tweaked again after a couple of hours. Like the M140s, the .26s ended up positioned only 10 to 15mm away from their position when using a traditional system.

So a little time was spent listening with SPACE+ turned off, then the position of the PMCs entered into the Konfig room information and SPACE+ optimisation was applied. Like the M140s, the PMCs benefitted from the improved modelling in SPACE+. The room optimisation notches applied by the Linn calculations are excellent, again I found that tweaking them made no improvements, in fact, deviations messing stuff up really. After a few weeks of use, the only change I made at the room optimisation end of things (ie the bass) was to add a 0.9 dB bass “shelf” to add a little weight over the full bass range. What of that sometimes tiring top end? Well the effect of the Linn Exakt filters are easily spotted – with the treble much more in keeping with the rest of the frequency range. A nice change and one I stayed with for a week or so, but eventually dialled in a -1.8dB treble shelf (after much experimenting with values above and below this). Now we have, to my ears at least, a well-balanced frequency range.
One more area that didn’t sound right to me was a harsh edge on vocals – particularly female vocals. There’s nothing to play with here on Linn Konfig so I experimented with a few cables and found something quite astonishing – the supposed perfect digital signal going along the Exaktlinks makes a difference. This doesn’t make much sense, but its probably about noise getting into the Exaktbox – I’m sure its nothing to do with data corruption. So changing from a standard Cat 7 ethernet cable between AEDSM and the Exaktbox to a Chord C-stream (their most basic streaming cable) lost the sharp edge on the vocals and I can’t hear any downsides. Strange but true.

So what of the overall sound of the system? Well at this point, with SPACE+ set up and the cable change above, what we have is a very musical result. The changes I noted going from M140 to PMC in the traditional system are all relevant here, but without any noticeable downsides. The PMCs go deep but are better controlled, vocals really come across with nuances and texture and treble is both full of detail and subtlety. On top of this, Exakt brings a sense of the recording space, speed, masses of information and a step change in the separation between instruments. And I can listen for hours. And hours. And hours, and I do so.
From what I remember of the Exakted Akubariks (at this point about 5 weeks ago in a different room, and about 3 or 4 months ago in Canada), then the PMCs are at least their equal in terms of detail retrieval and subtleties. But they have a different approach to life – they’re very much more lively – they drive a rhythm along with more conviction and a sense of fun, but they do this without being out of control or aggressive. Perhaps the PMCs don’t go quite so deep as the Akubarik, but this is very room dependent so there’s no real direct comparison here. So all was well, but the story doesn’t stop there.
About 3 weeks after Exakt conversion, there was a new software release (for the detail people, it was Exakt compiler version 16). This made no changes to the filter settings for the PMCs, but it changed the way in which the Exaktbox processes and applies those filters. At first, I didn’t quite believe what I was hearing. It took the best part of a day to get past the initial size of the change. That this magnitude of change could happen through software, and to move on to all the little subtle changes that came with this release is an eye-opener. First, and most obviously, was the massive improvement in the sense of imaging and space of the sound. I’m guessing that this is down to much more effective phase alignment processing and it is astonishing in its effect. The speakers truly disappear and instruments and voices are absolutely defined in space – very stable and very believable. The context of the recording is much more obvious – particularly live tracks where the sense of the recording space is portrayed into the listening room. I would liken the size of this software driven improvement being equivalent to moving from ADS/1 to KDS/1. And it was free. Remarkable.
But all this separation, sense of space and believability allows through so much more detail and subtlety. And it’s across the frequency spectrum. Bass lines on Daft Punk’s "Giorgio Moroder" (from the Random Access Memories album) reveal themselves to be even more complex than before and as the crescendo builds at the end, all that complexity remains in control with no tendency towards harshness. Throughout the track there are numerous synth sounds that move from bleeps and blops to being clearly identified sounds that evolve within each note – adding texture and flavour to the track. At the end, the click evolution is much more obviously about a note generated with a very “square” profile. " Get Lucky" (also from Daft Punk's Random Access Memories) is revealed as being much more complex than just a good bit of dance-pop. The lead vocal is clearly more “breathy” with words like spinnin’ now being spinnin-uh, with the uh part only just discernable, but clearly there. Midway through the track the bass line drops out and there’s a buzzy synth underlying the main theme – but it is now audible as a vocoder vocal sample that’s been stretched and twisted. These might seem like minor points, but together they add up to a track that’s much more musically enjoyable – one worth sitting down and concentrating upon rather than being some kind of background or party track.
The echo of the venues on Fink’s live album (entitled "Wheels Turn Beneath The My Feet") is both more obvious and decays away for longer without crashing into or blurring the following notes. The sound of hammer on anvil is right there about 3 feet out from the speakers, just left of centre and about 3ft off the ground in Funkerman’s "Speed Up" (ATFC Remix from the Speed Up EP). Mary Gauthier’s hatred and ire in "Falling Out of Love" (on the "Mercy Now" album) are laid bare whilst the heat pipes hiss. On all of this music, even though there is this very clear separation of individual instruments, there’s no doubt about this being a presentation that still hangs very much together as a joined up performance. Very soon, you get wrapped up in the messaging and mood of the music, enjoying the expressions and flavours, ignoring the hifi, which tends to just disappear.

As you might have gathered, I’m very impressed with the implementation of Linn Exakt with PMC Twenty.26 speakers. The approach Linn has taken to produce digital crossover filters, phase correction between and within drive units and time-aligning the signal has paid massive dividends. The combination of Exakt and PMC really pushes these speakers to compete in a price bracket two or three above where they are as a passive speaker. They sound different to, but very much in the same performance league as Exakt Akubariks. And they’re different in a way that brings more life and fun to the music, but in a way that’s not tiring or wearing – but listenable for hours. And boy do those hours fly past quickly!

 Now we can look forward to Linn releasing this as an official conversion – it’s a pity that the Twenty.26 will be in the shadows a little now that Twenty5.26 is about to hit the market – the gestation time seems too long to have hit the market at the right time. On the flip-side, think of all those traded-in Twenty.26s that will be hitting the market ripe for the transformation that Exakt can bring to them…

For those that heard Exakt in the early days and weren’t impressed, or for those who thought/think that a Klimax badged system MUST be better than an Akurate badged system, I urge you to think again and give Exakt another listen.

Post Script: Since the initial implementation, my Klimax Twin amp has been added into the system – I use this for the mid-range where it seems to bring the best improvements, having tested it across the board. Taking the mid-range from Akurate level to Klimax level amplification has helped at a little more subtlety and detail, but its not a huge uplift – more of a nice to have, given that the amp was already in my possession. If another becomes available at a sensible price I would add it into the bass before the treble.

Now with added Twin
Post Post Script: I'm now wedded to the PMCs for the longer term, so Twenty.21 have replaced the Linn Katans (formerly there were Linn Majik 109s prior to this recent wholesale change) as rear speakers and a Twenty.C has replaced the Linn Tukan (again, formerly a Majik 112 for a number of years) as the centre to complete the 5.1 set up. I must say, the Twenty.C is in a different league to the Majik 112 - a very impressive centre speaker

Thursday 9 June 2016

Linn Exakt and PMC Twenty.26. World First Review Part Two - Converting The Speaker

Part Two Of A Three Part Review

EDITED 30 September 2016:  The official Linn conversion kit for the PMCs are now available from Linn dealers - there's now no need to convert DIY as per the described below - although the official kit still requires much of the same actions :)  Note that the PMC warranty will still be voided by the Linn kit.

After conversations with Linn about the timing of the conversion kit launch which is still not clear, back in April it was time to take the plunge.  So here's what is involved in the conversion from standard Twenty.26 to an Exakt compatible version. To be fair, this conversion could be done for any project to convert the PMCs to any form of active operation, it is not specific to Exakt.


The basic principle here is to remove all electronics that sit between the rear terminals and the drive units in the speaker. Fortunately, PMC have provided the .26 with pairs of terminals for each individual driver unit within the speakers. This is intended for bi-amp or tri-amp operation of the speakers, still in passive mode.  Exakt needs a direct connection to each drive unit within the speaker, so the 3x pairs helps considerably in this conversion. The latest Twenty5.26 from PMC has reverted to a single pair of terminals and uses a metal panel, so would be considerably more work to convert. The plan was to make the conversion reversible, so making as few modifications as possible whilst still achieving the objective.

Dismantling and Removing The Passive Crossover

The back panel with the vertical terminal links already removed - this is how the speaker would be used in a tri-amp passive arrangement.  Note the textured paint finish on the back panel shows every bit of dust and finger mark, but these are easily removed with a lightly dampened cloth, as you will see in the finished article pictures at the end of the post.

The panel is held in place by multiple allen headed countersunk machine screws.  They're not particularly tight as they're threaded directly into the MDF of the main cabinet.

Once all the allen head screws are removed, the panel can be lifted out.  Here, a cloth has been used to support the panel on the speaker's stand without damaging the finish of the stand.  The panel is a fairly straightforward piece of machined MDF.  The crossover is very substantial and looks to be populated with good quality components. Along the top of the picture the cables go out to the individual drive units - these will need to be connected directly to the speaker's rear terminals to enable Exakt operation.  At this point they are kept connected until they can be correctly identified.
Here the damping foam for the Advanced Transmission Line can be seen.

Fortunately, the drive units for each cable are clearly identified and each cable has a clear + side marker on the cable itsself.  Before disconnecting the cables, the treble cable was given a single cable tie as a marker, the mid-range cable 2 cable ties and the bass cable 3 cable ties.  This makes them identifiable once they are removed from the passive crossover.  Note different gauges of cables used

The crossover circuit board is attached to the back panel by 4 crosshead corner screws and the mounting bolts for the 6 terminal posts.  Here an 8mm spanner is being used to loosen the terminal post nuts.  There are 6 nuts, washers and shakeproof washers to be removed.  Note these were only nipped up and not tight - presumably to avoid damage to the circuit board.

Once the 6 terminal nuts were removed, the corner crosshead screws were removed

The crossover board then just lifts off the terminals.  Here the plastic spacers that keep the crossover board supported away from the back panel can be seen.  This is all the dismantling completed - the posts and spacers all remain in place as this is where the cables that go to the individual drive units will need to be connected


At this point, all the passive crossover components have been removed.  The speaker cables that go from the passive crossover to the drivers have female spade terminals, but they now need to be connected to the back of the cylindrical terminal posts.  It would be easy enough to just cut off the female spades and solder on some loop terminals, but that would make the conversion back to standard passive more complex and that was something that was to be kept as straightforward and as standard as possible.  This maintains the future resale value of the speakers as there is a much bigger market for standard passive speakers than there is for Linn Exakt compatible speakers.

So a conversion from cylindrical terminal posts to male spades is required.
Parts required are 5mm gold plated loop terminals (its hard to find any of these. So here, 8mm are used ones and they're a little larger than ideal so stanless steel 5mm washers were also used to help with the fit), male gold plated 6mm spade terminals, some solder and tubes of insulation

On the left the 6mm male spade, on the right the 8mm loop.  Using pliers, the cable grip part of the male spade was gently squeezed together to the point at which it was a tight push fit into the cable tube on the loop terminal

Here the male spade has been push fitted into the loop terminal

Working through the 12 connectors - 6 for each speaker

Using a 45W soldering iron, heat was applied to the interface between the loop terminal and the spade terminal at this end of the loop terminal's cable tube.  Only once the flux would melt on the outside top of the loop terminal tube was the solder applied to the joint - this makes sure that all the surfaces are hot enough to receive the solder at the same time and eliminates the chances of dry joints.  Soldering is being carried out on a ceramic tile work surface

After cooling the male spade on each terminal was bent upwards to approx 45 degrees to assist with connecting to the speakers' internal cables.  Later, after fitting the loop terminal to the speaker terminal posts, the loop terminal was also bent upwards by about 20 degrees as other wise it would have been easy to trap the cables between the back panel and the speaker carcass

The terminals are then attached to each of the terminals on the inside of the speaker back panel using the stainless steel washers and the shake proof washers and nuts that originally held the crossover to the terminal posts

Then insulating soft plastic tubes were added over the male spades.  Probably not necessary.  Additional pencil markings show which way up the panel goes and which column of terminals is +ve

Here the panel is offered back up to the cabinet and the cables connected.  You can see the extra bend put into each of the loop terminals to move the cables away from the cabinet.  Tweeter to the top pair, mid to the middle pair and bass cables to the lowest pair, using the previously fitted cable ties to ensure correct connection order.  Note, the cables are only just long enough to reach the terminals.

Once the panel was refitted, a 1.5V AAA battery was used to ensure that the speaker cones all moved in the correct direction.  Put the positive of the battery onto the positive of the speaker and negative to negative and the speaker cone should move outwards,  Just a brief touch is enough to check but doesn't damage the drivers

The back panel was then masked up to create guides for adding a set of old Linn active system labels

Labels installed

So that was it, all done.  Checked, checked and checked again.  The connection sequence was as follows:

- Connect bass amp to bass terminals
- Play music quietly and ensure only bass info was coming out of bass drivers.
- Switch off amps
- Connect mid amp to mid terminals
- Play music quietly and ensure mid information is coming out of mid drivers
- Switch off amps
- Connect treble amp to treble terminals
- Play music quietly and ensure treble information is coming out of treble drivers

Enjoy the music.  Pack the passive crossovers carefully in bubble wrap and a strong box and store in cool dry place.

Part Three Of The Review Is Here 

EDITED 30 September 2016:  The official Linn conversion kit for the PMCs are now available from Linn dealers - there's now no need to convert DIY as per the instructions below - although the official kit still requires much of the same actions :)  Note that the PMC warranty will still be voided by the Linn kit.

Wednesday 8 June 2016

Linn Exakt and PMC Twenty.26. World First Review Part One - Background

Part One of a Three Part Review

Part Two Here

Sometimes, a technology arrives that makes the previous technology instantly seem hopelessly inadequate and it makes you wonder how we ever put up with the older version. For example, DVD picture quality compared to VHS video tape. Or the jet engine compared to the turbo prop.

I'm not one for hyperbole, but there's a chance that Linn's Exakt is nearly there, but the World doesn't seem to have noticed. Lets hope its not superior in the way Betamax was superior to VHS.

Let's wind back about 2.5 years and see where we go from there. Back then (Meridian's DSP series not withstanding), the normal way to improve a Linn system was to go active. Active, in Linn terms, used to mean taking the output from a pre-amp, splitting it into the appropriate frequencies for the drive units in the speakers, feeding that driver specific frequency range to a power amp and connecting that directly to the drive unit. This is more accurate than using big clunky passive crossovers found inside traditional passive loudspeakers. Everything else being equal (sources, amps etc.) Linn's active systems sound better than their passive systems.

But on their 40th Anniversary in September 2013, Linn launched Exakt - a very different architecture for active systems.  The launch event is reported here:




So what's different? Well, in a traditional system, using a CD or network player for example, the digital signal is converted to analogue in the player and is then analogue through the pre-amp, power amp and speaker crossover (either active before the amps, or passive inside the speakers). Exakt keeps the signal digital for longer, with a proprietary protocol connecting sources to the digital crossover called Exaktlink. So the combined network player and pre-amp (called a DSM in Linn speak) plays network and internet music, accepts digital signals from other digital sources and converts analogue inputs (such as a turntable) to digital too.  It then converts these inputs into Exaktlink format and passes the signal to be played along to either an Exakt processor integrated into a pair of active loudspeakers or to an Exaktbox which includes Exakt processing and digital to analogue conversions (DAC) to send information to a power amp dedicated to a single driver in a loudspeaker.

For the purposes of this post, I'm going to ignore loudspeakers that have built-in Exakt processors as they are unique to Linn.  Of interest here are the Exaktboxes as they can be software configured to drive Linn's extensive range of speakers both past and present and they can be software configured to drive speakers from other manufacturers too, which is why this is about PMC and not about Linn.

So, an Exaktlink digital signal is sent from a DSM to an Exaktbox. Exaktboxes are available in the usual Linn hierarchy of Majik - Akurate - Klimax. The Majik Exaktbox-i has integrated power amplifiers, the Akurate and Klimax Exaktboxes need external amplifiers. To simplify here, I'm going to write about the Akurate Exaktbox 6, a system that can support speakers of up to 3 drivers per speaker (2x 3 channels = 6 of the name). This is very relevant here as the PMC Twenty.26 has 3 drivers in each speaker. What does the Exaktbox do with the incoming Exaklink signal?  A number of things:
  • Splits the signal into its right and left components
  • The Exakt processor also applies phase correction which corrects for phase errors between drivers AND within each driver
  • The Exakt processor applies a time adjustment to ensure the music arrives in sync at the listeners ear
  • For each of right and left, that signal is then sent to 3 separate digital to analogue converters (DACs) - 3 for the right, 3 for the left
  • Each of those DACs is dedicated to one driver in one of the loudspeakers
  • Each DAC applies the correct filtering for its allocated driver
  • For Linn drive units in the Akurate and Klimax ranges, individual drive units are measured at build time and Exakt corrects for any errors found to bring left to right matching to levels not seen before, regardless of speaker quality and price.
  • The Exakt processor and bass channel DAC also apply SPACE Optimisation+ room node adjustments to the output of the bass channel, inserting sharp dips in the output volume at the frequencies where the listener's room is known to have bass "humps", hence flattening out the low end frequency response

The effect of the calculated frequency dips on the under 100Hz signal (no changes are applied above 100Hz) plus a little manual tweaking
  • Each DAC then applies the volume control level before finally converting all of this into the analogue domain and passing the signal along to a power amplifier that is dedicated and has a direct connection to the appropriate drive unit in the speaker.
So for a pair of PMC Twenty.26 loudspeakers, a 6 channel Exaktbox is required, along with 6 channels of amplification, and the removal of the standard passive crossover inside the speakers to allow the amps to be directly connected to the driver units.
The really key thing about how the Exaktbox operates is that it is configured by software, using Linn's Konfig application run from a PC or MAC attached to the same network as the Linn DSM. This means that the same Exaktbox process0r / multiple DAC unit can be software programmed to support any speaker that Linn has provided profiles for - from their own range, from the ranges of others and from speaker manufacturers who have developed Exakt profiles and submitted them to Linn. So upgrading speakers is now possible without upgrading hardware crossovers - just load up the appropriate profile for your speaker, connect up and you have your system amended to suit. Very clever. Konfig also allows the input of room dimensions, listening position, speaker position and building material types to allow for the correction for room bass nodes to be applied to the music and for the time of flight to the listen to be adjusted.

Entering room information into Konfig so the software can calculate where there will be bass humps in the room (there are many more dimensions to be entered not visible in this capture
In the Linn Konfig Software, selecting the appropriate loudpeakers from the drop-down list applies the correct profiles and filters to the Exaktbox
Right, if you've kept up with that lot, well done. Let's consider why Linn would support anything other than their own speakers. Surely this would impact on sales of their own speakers? Well I would suggest not. Linn speakers (with the exception of the Keilidh), probably don't sell in massive numbers, they appeal to a limited set of listeners (like lots of other speakers do too of course), and its fairly rare indeed to see Linn speakers used in non-Linn systems, whereas it is very common to see Linn electronics - particularly sources - used with all kinds of speakers from other manufacturers. Also, Linn probably see a market where they can massively improve the performance of other manufacturers speakers and generate a new group of buyers for Linn electronics. So it makes some sense to develop Exakt filters for third party speakers. There is also the possibility that a group of speaker manufacturers will see the benefits in Exakt making their speakers sound better and therefore make them stand out from the crowd - certainly Kudos have seen this benefit and grabbed hold of it very quickly.

Of course, modifications need to be made to these third party speakers to allow amplifiers direct access to each drive unit (although Kudos now include Exakt compatible connection options as standard on Super 20 and T-808), and that's the subject of part 2 of this review - how a pair of Twenty.26 speakers can be converted to work with an Exaktbox and multiple power amps.

So is this a game changer? Well back at the launch in September 2013 I have to say I was underwhelmed. Yes, I could hear some differences, but all that clever processing to correct phase errors, supposedly seamlessly integrate drivers and near enough correct all phase errors between and internal to each drive unit should really have been very obviously an upgrade. Subsequent demos of a variety of speakers (although, to be fair, mainly Akubarik and 350) over the following year left me uninspired. Enough to decide to look for non-Linn speakers (but ones supported by Exakt in order to keep options open). I auditioned Kudos Super 20 and PMC Twenty.26 speakers at home (both of which were on Linn's roadmap for Exakt) and settled on the PMCs as a major step up from my previous Linn Majik 140s. With Linn Klimax DS/2 streamer, Klimax Kontrol/1/D pre-amp and Klimax Twin/D power amp they were good, but eventually got a little tiring to listen to - more than 2.5 hours was too much.  So there was still some doubt about if they were right for the longer term.

What has changed since then? Well, I went to the launch of the Exaktboxes and Linn's lifestyle Series 5 speaker launch (these are Exakt only) in September 2015. It was a good event and some stuff was demonstrated that was interesting, but still didn't wow me in the way the technology is supposed to do. About 2 months later Linn quietly updated the Exakt filters for some of their speakers - a significant change to the way that they handle the bass roll-off and there was much excitement on the Linn forum about the effects of this change. This was the most obvious and major change on top of a gradual trickling out of small tweaks and changes.  An early 2016 visit to an integrated Exakt Akubarik owner in Canada allowed for lots and lots of listening to a system that was transformed. Now Exakt sounded significantly different and significantly better than the non-Exakt equivalent speaker. Instruments so clearly defined, located in 3D, no bass flabbiness, such clear highs and vocals with real texture and emotion. Suddenly, the technology seems to be delivering on the promise. Listening for 4.5 hours proved extremely enjoyable and not at all fatiguing. Was it launched too early? Have lots of people heard it once, were underwhelmed and never bothered again?  I don't suppose we'll ever know the answer.

Back in the UK I went for a visit to not-so-local Linn dealer House of Linn and had another listen to Exakt Akubariks, this time using the external Akurate Exaktbox and Akurate power amps to better simulate the way the electronics would work with PMCs. Initially I would be bringing the Majik 140s back into action as their Exakt filters were available at the time, whilst waiting for the filters for the PMCs. The plan was to run the Majik 140s whilst waiting, then find out if the PMCs could be tamed by Exakt when the filters were released. If not, the Majiks could stay a while longer, the PMCs could be sold on and I would save up for Akubariks.

Well going from Klimax electronics passively driving the M140s to Akurate level (theoretically one step down in the Linn hierarchy) was a big surprise. Driven by the Exakt Akurate boxes turned the M140s into something far better than I'd imagined. Faster, controlled, better imaging, tighter bass, quiet impressive. I would've been very happy to live with them whilst saving for the Akubariks. But then the PMC filters were released, but not the conversion kit to go with them. What to do? Wait? Take the plunge?  Check out part two: