I got them from the then UK dealer for £800 the pair.  Not sure if he still is?

The Lazy amorphous are normally IRO $800 in the states.

Cool:)

We got back from Scalford late on Sunday night.
Unloaded all into the garage. The following day I moved everything round the side of the house - the only way to get the big mid bass horns in (thought the double French doors of the music room).
I set it all up and had a good listen!

Soon after this I borrowed a pair of wave guides for the ribbon tweeters.



Whilst these were interesting they did not really improve the sound. They were designed for the smaller less efficient Raals

They covered up about 3/4" top and bottom of the Ribbon area - in spite of this they measured about 3-5dB more efficient!

This plot shows the difference and the 2nd one is of really high 1/40 octave. This shows just how flat the Raal Lazy ribbons are!



They didn't really do anything for the looks and made the stack even higher - wrong direction in my room..

Very soon after I got some tractrix upper mid horns to try - They are 600Hz horns cutoff freq and I crossed them at 1200Hz - rule of thumb is double the frequency of the cutoff to get them sounding right...



Note here I've gone for the classic Upper mid at the listening ear position and not the tweeter - this is how I have it too this day... 
Note also the sawn out section is repaired - good as new:)








I had / have no specific loyalty to conicals - just that I could make them for peanuts. These cost a lot more! The drivers were still the JBL2435Be's.
Very good drivers. Freq range ~1200 - 12000Hz

The difference was that the music flowed more and was easier to listen to. The upper mid range is the most ear critical - that's why I started there.

This gave the opportunity to drop the stack as the horn is a lots smaller in diameter.

I thanked the rack / threaded bar solution for it's flexibility.

I then started dabbling in DSP X/O's - I got 2 Behringer DCX2496's, they are only 3way but I configured them one for each channel to get 5 way and 1 spare;)



Drawbacks - Sound quality. No matter what I tried they sounded low res.
The gain structure was hard to reconcile too. As there was no digital volume control everything had to be analogue in - less than ideal...

Pete had a pair too and even with considerable modification and a line level post DSP / DAC volume control they still were somewhat lacking.

The Behringer DCX 2496's did have one redeeming feature - automatic time alignment. You just plug the Behringer mic into the designated socket press a button and off it went, making chuffing noises through each channel one at a time, over and over until it had figured it all out and then put delays in the signals for perfect 5 way time alignment! Took all of about 120secs to do it too! Pro Audio gear eh!


Here is an example - fantastic. 




This is the first time I'd heard time aligned sub bass - I liked it - subtle but everything just hung together slightly better.

I made a better shelf for the amps to go on



Next up - a lot happens in a short space of time - Exponential bass horns, Vitavox S2 upper mid drivers (perhaps the ultimate driver?) and back box experimenting... watch this space.

Yes John, the passives were back PDQ - I did enjoy playing with the X/O and some basic room correction though...

The S2's had landed - well, I'd had one for a while but it had a trashed diaphragm, so I waited until I could get another one and then sent them off to Vitavox in Bristol for their new diaphragms, alnico mag recharge and set up / test.

I'd made up the 2.610" 16TPI WW threaded adapters in birch ply.

They came back and so I plumbed them in and held my breath. 





They just look right and they measured superbly - this is on a 3uF cap only. It somehow magically takes care of the quite aggressive notch.

Romy the Cat is the one who publicised this and how good the latest diaphragms sound and in general how, although not without characteristic, magical they can be...


I was not disappointed in the least bit! They were brilliant  - faster and more dynamic than anything I'd heard yet so vivid and lush / sweet sounding and correct  / just right, all at once.
The speed and rightness of fast violin work, as on the Drottningholm baroque quartet works or the purity and life likeness of Regina Spektor's vocal was something to experience!

Measurement wise  - hard to beat this! This is 1st order 3uF cap and natural rolloff at the higher end.



I was also cracking on with the round exponential mid bass horns...

Jig sawing it umpteen concentric birch plywood rings..



Note the old conicals in the back ground, taking up space in the workshop!

I made this crude horn spinner to aid the smoothing.





Glued together then some 2 pack filler and smoothing with a drum sander - oh the dust! 



Here in brought in for a comparison







You can see how much the stack height could be dropped. Right direction..



Something was not right though - They sounded sluggish and a bit wayward - the conicals had just worked, straight out of the box.

These would need some refinement to be worthy of a place in the system...

Here was on candidate for improvement - reduced back box chamber volume. I had experimented with sand filled bags at first to get an idea of volume reduction needed. This was heavy!



Expanding foam would be light and achieve a customer fit - I could them reduce with a long knife easily.

The drivers are protected with grease proof paper and the chamber with double cling film.





This and making the throats larger cured the problem and they could take their rightful place...

Here's a Freq plot of the improvement!



Here they are finished



The sanitary ware white was now ivory silk. Spray painted.

I also refurbed the JBL2482's - these are worth a bit now!





It was all coming together nicely





Next up - more DSP explorations and risk taking!

Bloody Hell Steve you have the HiFi bug bad.

Hats off to you Sir - Quite astounding stuff......

The first trials were with it set in pass-through mode - all Najda would be doing was acting as a DAC (well 4 of them) and outputting 4 analogue line outputs to my amps.

At first I was using it set at 48KHz internal sampling. Hmm, not that impressed. Then I tried 96KHz and wow, this is good was the result. Then I tried 192KHz,

Hmm but tizzy on top. so I settled for 96KHz.  


How would the 4 DACs compare to my 1 Dac of choice (DPA enlightment) and Puresound L10 Pre amp? Well very favourably - slightly and I mean slightly different tonal balance, which was to my liking! So no loss there. 
The volume control was great - either by pressing the up or down buttons of the 4 in a plus sign on the right, or by remote of choice - I used an all in one from Tesco's that can also select source and which preset DSP/XO settings you have (upto 8 are loadable).

After extensive listening and really convincing myself that the DACs and DSP going on was not losing anything I played my precious analogue signal though it!
All you read about "my analogue signal is precious and must be kept pure... etc" well BS to that! Either folk have not heard the right DSP or they are just saying that cos' they are stuck in the mud, head in the sand'ers 

Right, the next leap of faith was to remove the passive X/O's and connect the amps direct to the drivers! I'd already done this with the Behringer DCX and nothing had blown up.

At first I familiarised myself with the SW and interface and found it logical and easy to use to set up X/O's and filters.

Here's a pic of the X/O interface screen for a tapped horn channel.



Note the gain settings, you can cut dB to correct room mode issues and the fact that there are 10 channels but only the top 8 can be used. Full 5 way is a possibility, but the expansion board to do this is not yet designed... so 4 way it is, with the feed from the upper mid (has not upper X/O slope on it) line output looped to two amps, the first for the upper mid channel and the second for the tweeter channel.

As each of the channels is selected settings for that channel are shown on right. The one above is for the left mid horn. All X/O types are catered for and from 1st to 8th order.

 You can also review the slope - not that I bother with this usually.



I first set up the X/O's as I was used to them in passive land - I found some not massive changes produced better sound and measured better - but the passive X/O's were close and I liked their sound...


Applying room correction is simple - You measure see a massive suck out or room mode and attack it with a filter...

For example - before: the sub and mid bass channels measured together with no correction



With correction applied




In layman terms (in other words what I can understand), what this means is that for any given input frequency, the speakers will reproduce that frequency in the room at the ear position as it was intended. Room effects are removed so a bass line scale played will play down the range with each note at the same volume (SPL) all the way to 20Hz. Not many systems can actually do that!    
we are used to hearing a fat around 50Hz sound cos' it's what smallish box speakers can do easily. We are also used to significant roll off below this so that speaker manufactures do  not have to worry you with the bass traps etc you'd need - let alone the cabinet volume, driver size and amp power to it.
Bear in mind my tapped horn subs are 105dB/W efficient and they have a 650w driver in them.

I quickly found that Najda was adding masses of quality and texture to the bass that I could not have previously dreamt of!
Overhang is the enemy of nice bass. You want it where it should be, not flabbering around lingering either side of that.

I played around with the bass first - you can't blow these bass drivers if you get the X/O or gain wrong, you can stuff full power down them with no X/O and nothing will happen to them apart from they will play it as fed.

Very different to the compression drivers. Give a compression driver that's designed for 500Hz horn loaded and up, a 100Hz signal at significant volume and it's like feeding in DC - my Vitavox S2's are rated at 20W BTW. They will make PA loud volumes (or close to Concorde loud volumes) on that of course!

Next I put the mid horns on - just an X/O in DSP - No correction needed. Same with the upper mid horns - All worked fine.

Wow - I was liking what I was hearing - here's how it measured



Note that there is still significant SPL down to 10Hz! The rest was flat enough to make me happy. 

More work on the X/O slopes at the mid and top would see the sight peaks at 500 - 1K and 9K smoothed - This was a case of choosing the best type of X/O - Linkwitz Riley was order of the day in most cases.
  

I was impressed by Najda - enough to keep it and never want to part with it - I have even thought of buying a second board to keep as a spare in case anything should happen to this one...

Anyway. Now time to box it.

I chose a cheap case from China or was it HK - can't remember...

They would drill the holes for the buttons and LEDs - I did not know what display I was going to stick with at that time - Either the Yellow one, a white on black one or pay more and get a nicer OLED one... So I would cut the slot for the display...

Here it is, as it arrived











8mm thick ali front panel and all holes for about £65 landed!


Board in




LCD display cutout




All migrated and plumbed in it sound great and was easy to use.




A 4-1 remote controls volume, mute, which set up preset you want to load, up to 6 are storable.
You can also select source etc via the remote.


After all this, I took a long earned break and just used it, listening and enjoying with some minor tweaks...

I tried a passive 1st order cap again on the S2's (upper mid) and liked it and that's how it still is over a year later - if it ain't broke...

Next significant change would be to expand on my music serving input quality - watch this space

Ah, first up was some more woodwork, I do like a bit of woodwork...

I'd read on Romy the Cat's horn site the he rated wooded horns greatly - and that the upper mid horns on the S2's should really be 550Hz cut off - I had 600Hz glass fibre / composite on them at that time! - Hmmm, so last early spring I knocked up a pair of 550Hz

Done in two sections to start with, for ease of turining...

Cutting the throat section on my trusty 9" swing 1941 South Bend (all the way from Indiana USA - they could not send us guns and men, but they could ship lathes etc for the war effort. I wonder how many South Bends are at the bottom of the Atlantic along with all the more important merchant seamen etc - war is a terrible, terrible thing! 



Turning the flare / mouth







Now to make some proper throat adapters out of composite. Done on my smaller Warco long bed Mini lathe

Face plate mounted







Cutting a 2.160" diameter, 16 Threads per inch Whitworth thread on the Mini lathe. I had to buy an Imperial lead screw to do this...



Trial fitting the S2 - going, going, gone!







There's not much more satisfying in the DIY workshop than cutting your own big internal threads! 

The finished throat adapter




Horn on driver




Paint job to match to match the rest.



In system



Slightly larger than the 600Hz ones, and with a great mouth flare - they sounded good too.



The 600Hz horns were put on the market.