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Ah - the good old battleship grey Cambridge Audio livery. It was panned by the reviewers, as were the buttons on the CD player (they described them as reminiscent of poking dead flesh). Very unfair, b

R5s arrived:  

Maybe not Speaker Porn these days, but back In the day these were pretty hawt.  Altec Model 19. Woofer: 15” 416  , Mid/high compression driver: 802 , Sectoral horn: 811 Very efficient: rated

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Thanks guys.  There is actually a story here.  Four or five years ago I had a bout of flu, and to see how I was recovering I went for an early walk one day.  I fell to thinking about my old dad, who had always expressed an interest in learning to paint.

 

We bought him a starter kit, and in the end he went to his grave without ever having opened the box.  Actually, he was probably scared of trying and failing, and didn't book to go on a course to learn.

 

Anyway, one of the things I had always wanted to do was learn cabinetmaking - and that walk in the spring sunshine gave me the moment of clarity - I was not going to go to my maker without learning.  So I booked a course - in the end 6 weeks taken in 1 week chunks, with a cabinetmaker in Ross on Wye (UK).  I left there was a set of oak drawers, currently in our bedroom, hand cut dovetails etc etc - the kids are in competition who gets in when I pop my clogs.

 

The speakers are the latest think I've built.  Apart from the rear support frame and the tweeter sub-baffles, which are solid cocobolo, the rest is baltic birch marine ply.  The dipole bass unit is painted with black milk paint, and the top panel and bridge are veneered.  That gave me the opportunity to learn a new skill.  It is done traditionally using hot hide glue.  I then French polished them with lemon shellac - again a new skill.

 

Most importantly - my significant other likes them.  Mind you I've inflicted some pretty outrageous speakers on her over the decades, but it is something of a relief after so much work that they get the thumbs up!

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The LX521's blew my socks right off when I heard them at a friends place. The soundstaging was wonderful - also it was interesting to see the bass drivers doing slow, large excursions on some tracks.

 

As much as I'd hate say it - they are a steal at that price.

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I'll be able to tell you in a week or less - just finishing the second four-channel power amp; final wiring underway.  I can tell you that they are not a project to be undertaken lightly - it is an expensive and complex project.  Drive units are nearly a grand (in UK pounds) alone $1600 in the US.  The bass units are the most expensive of the drivers, because they were made to Linkwitz's spec.  

 

The woodwork is complex, but flat-pack kits are available from Madisound in the US https://www.madisoundspeakerstore.com/cabinets/lx521-linkwitz-lab-flat-pack-cabinets-%E2%80%93-pair/ and http://www.magiclx521.com/lx521-components.html in Europe.

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The woodworking is much easier than for example this. Not trivial by any means, but easily simplified by the use of said flat packs.

 

By the way - what's your plan for amping? I'd actually recommend different amps for different drivers. My friend had the best success with Class D for bass (due to 2 Ohm dips), class AB for mids and highs. I'd go as far as to say that highs can actually be done in class A for best results, they don't need that much power.

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Yeah flat pack would help.  But not for me - I started with two 8 x 4 sheets of marine ply and did it from first principles.

 

I've gone for Douglas Self blameless.  Each bass driver gets a load-invariant amp (four in all) with a measured output of 175W at 4 ohms each.  Mids and highs get a compact blameless, which still does 175W into 4 ohms, but with more distortion that the load invariant.  They are all Class B.  Measured distortion at 50W 8ohms, 80kHz bandwidth and RMS sensing is

 

1kHz 0.0028%

10kHz 0.0040%
20kHz 0.0056%
 
But the residual distortion of my set up is 0.0027%, so the actual harmonic distortion is pretty insignificant.
 
In hindsight I might have gone for his "trimodal" design.  That has a switch to select either Class B, or Class A/AB.  In A/AB mode it does 30W class A and then changes to AB from 30W to 100W.  So easily switched to Class A/AB for the tweeters.
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They look really interesting modules; loooong thread though, 127 pages in about a year.

 

Self is not without his quirks - he is very anti FET and anti AB - although the performance figures of the current modules in your link have superb performance.  Don't underestimate the influence of power supply wiring - the half wave rectified currents in +/- power supply leads to the amp can induce significant excess distortion.

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Yeah, I have spent some time at the linkwitz page and checked prices. They are not cheap but if they sound great I would not mind. One major hesitation I have had is not knowing anybody who has built them.

So looking forward for your opinion whether they are worth the money or not.

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Yeah flat pack would help.  But not for me - I started with two 8 x 4 sheets of marine ply and did it from first principles.

 

I've gone for Douglas Self blameless.  Each bass driver gets a load-invariant amp (four in all) with a measured output of 175W at 4 ohms each.  Mids and highs get a compact blameless, which still does 175W into 4 ohms, but with more distortion that the load invariant.  They are all Class B.  Measured distortion at 50W 8ohms, 80kHz bandwidth and RMS sensing is

 

1kHz 0.0028%

10kHz 0.0040%
20kHz 0.0056%
 
But the residual distortion of my set up is 0.0027%, so the actual harmonic distortion is pretty insignificant.
 
In hindsight I might have gone for his "trimodal" design.  That has a switch to select either Class B, or Class A/AB.  In A/AB mode it does 30W class A and then changes to AB from 30W to 100W.  So easily switched to Class A/AB for the tweeters.

 

Before Self touted optimally biased class AB stages to reduce crossover distortion it was common knowledge in the industry for a much longer time that higher bias in a class AB output stage sounded better. I don't believe that Self's publishing of these articles changed the way AB output stages sounded with respect to bias current. They were nice looking graphs however.

 

Really nice woodwork and great story about it also.

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Yeah, I have spent some time at the linkwitz page and checked prices. They are not cheap but if they sound great I would not mind. One major hesitation I have had is not knowing anybody who has built them.

So looking forward for your opinion whether they are worth the money or not.

I'm replacing Quad ESL 57's equipped with my own dipole subs, so I have a known and very neutral reference with which to compare.  The main problem with the ESL's is that to image properly needs very careful set up, and a sweet spot that needs your head fixed in a vice (or vise depending on the side of the pond). I seem to be making a habit of dipoles - going back from the Quads, Podum 1, Martin Logan something, Magneplanar something.  Mind you I have heard some spectacular box loudspeakers (the best was the Rockport Arrakis) in the airy price stratosphere, and way out of my pay grade.

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Got the LX521's fired up.  Apart from a temporary hum problem, everything connected up and worked right off.

 

I honestly have heard nothing remotely like them.  The first thing that hits you is the imaging (or "phantom acoustic scene" as Linkwitz terms it).  They are twitchy regarding positioning - I was underwhelmed first off until I used a tape measure to set them equally from side and end wall, and then frigged a little with toe in.  At which point I've spent 4 hours having my socks blown off.  They are punishingly neutral, to the extent that truly great recordings sound awesome, and ones that are poorly recorded sound desperately bad - like having a camera into the the head and stone deafness of the recording engineer.

 

Mind you, I overdid the amp heatsinks - they got slightly tepid after four hours solid at pretty high listening levels.

 

All interconnections are balanced, and colour coded throughout to prevent something dumb (like putting the bass output through the tweeter).  Amp to speakers is an 8-pole speakon, for the same reasons - regular speaker connectors offer too many possibilities for getting it wrong.

 

 

 

 

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Impressive work, Craig.  If you want to make them a bit more "idiot" proof on top of the already excellent color coding it wouldn't be a horrible amount of work to change the jacks to use 3, 4 and 5 pin XLRs so that truly one cable only works with the correct jack. 

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