LXMinis and Kii THREEs - findings so far

OK, it's been a couple of days. I can't do a proper A/B/X double-blind test, because I don't have the gear, so I've been just kind of socialising myself with everything. I have Radio 3 on , which I like a lot, they play lots of interesting live recordings with real s-p-a-c-e in them from places like Wigmore Hall. The music plays most of the day, and I either sit and listen or go about my usual stuff - this is pretty much what I usually do anyway! Because I've left them long enough, I can't recall which ones are working, so I try to guess (or perhaps work it out would be better).

Yes, it's that non-obvious. Maybe it's the kind of music. But the LXMinis seem to have a more holographic projection of the stereo field, with individuals in, say, an opera, almost standing out from the background. The Kiis seem more flat, but much more accurate. There's a kind of "phasiness" about the LXMinis if you move around them, presumably because of their much greater extraneous dispersion, reflections off the front wall etc., but this goes away as you move into the area of the listening position. The Kiis utterly kick ass (technical term) in every possible dynamic and response respect, but the LXMinis don't leave anything out either.

I've had a couple of interesting experiences:

• Wife and I listened to Ashkenazy's 60s recording of Chopin Nocturnes on the Kiis, prior to setting up both sets, so I couldn't compare them. I wouldn't have anyway - this was utterly jaw-dropping. We were both in tears - no, really, we were hanging on every single note, the incredible skill and musicality of Vlad, blah blah blah, I'll stop now before I lose it! Pianos are amazing.
• I've been listening to Iggy Pop's Post-Pop Depression from 2016, having seen the American Valhalla film of its making. Again, this was prior to comparison capability. Hearing it on the Kiis I actually "understood" it in a way I haven't before - it's very, er, brutal in some respects, and pretty full on, and the Kiis just unpeeled it and laid it out in front of me. Even the vocals were clearer and more comprehensible! Weird. But good.

Of course, these mean nothing really, because I can't control for my emotional state, hormones, physical tiredness etc etc. But if it isn't about an emotional experience, what is it about? That's all I got into all this for!

But I also recall being astounded in similar ways, albeit with different drivers, when I first heard the newly constructed LXMinis. Their stereo presentation was incredibly engaging, rendering the sound of a hall with people and instruments in a way I'd only glimpsed with my Quads previously. 

The jury is out. I'll get Taiji Dave to come round for a listen - I've promised to play him the whole of Queen Live at Wembley '85!

LXMinis and Kii THREEs compared

This is a dangerous topic, because I've dropped lots of £££ on the Kii THREEs. However, if they're to keep their place, they need to have something better, more than different, about them, compared to the LXMinis.

Setup:

• 3-way analogue switch box used in reverse, so with RPi streamer (or anything else handy) as input, it selects
• Kii Analogue inputs
• LXMini miniDSP inputs
• Pink noise, from the HFN&RR Test Disk (HFN003), -20dB average level
• Radio Shack Sound Level Meter, showing 68dB (C weighted, fast response) on both systems at the listening position 

From the literature, getting the levels exactly the same is critical, even 1dB can cause listeners to prefer the louder system. Hopefully I've got it close enough.

Here goes...

LXMinis and Kii THREEs - how DO they work?

The excellent in-room sound of good speakers (LXMinis, Kii THREEs) is due to their control of the dispersion pattern of the speaker energy. In both cases this is achieved by inter-speaker unit interference, such that peaks and troughs of output from one unit coincide with troughs and peaks from the other, resulting in no effective output in certain directions. To achieve this, they use different  but related techniques (I think...):

• LXMinis 
• Use the mid-range (MR) and full-range (FR) units at right angles to each other, with the MR wired out of phase relative to the FR and SW
• There is also some delay of the signal to the FR relative to the MR, about 0.06ms, or 21mm, according to miniDSP app
• Checking this: speed of sound 21deg, sea level = 1238 km/h => 343.88889 m/s => 0.349 m/msec => 0.06*349mm = 20.63mm, so pretty close
• I'm not sure the delay has anything to do with the cardioid output in this case, as it represents only 2cm, which isn't anywhere close to the distance between the speaker centres
• Kii 3s
• Two pairs of woofers, with DSP delays applied between the units in each pair, between the pairs, and between the pairs and the MR unit
• See SL's note below for how these work

The amazing Siegfried Linkwitz's website discusses many useful things, cardioid output speakers being one of them:

A cardioid speaker can be made with two opposite polarity monopole sources separated by a distance D, and with the signal to one of the sources delayed by a time T = D/c. An implementation of this concept could be a driver in a box of depth D where the rear wall is an acoustic resistor R. At long wavelengths the box internal air volume behaves as a compliance or acoustic capacitor C. The acoustic output from the rear of the box is low-passed by the RC filter and delayed relative to the front output by T = RC.

So let's have a go at modelling such a thing, and actually building something. I've got lots of DSP power, not least because I have a computer, some modelling software (gnuplot), a few amplifiers, lots of MDF (!), and some allegedly identical chassis speakers.

I used a base file for gnuplot (sinc.plot) - I'm using the sinc function to plot a simple sine wave in 3 dimensions, but not spherical - that's too hard to visualise, and plot!

# set terminal png transparent nocrop enhanced size 450,320 font "arial,8"
# set output 'surface1.16.png'
set dummy u, v
set view 70, 20, 1, 1
set samples 51, 51
set isosamples 101,101
set style data lines
set ztics -1.00000,0.25,1.00000 norangelimit
set xlabel "X axis"
set xlabel offset character -3, -2, 0 font "" textcolor lt -1 norotate
set xrange [ -1.00000 : 1.00000 ] noreverse nowriteback
set ylabel "Y axis"
set ylabel offset character 3, -2, 0 font "" textcolor lt -1 rotate by -270
set yrange [ -1.00000 : 1.00000 ] noreverse nowriteback
set zlabel "Z axis"
set zlabel offset character -5, 0, 0 font "" textcolor lt -1 norotate
set zrange [ -5.00000 : 5.00000 ] noreverse nowriteback
sinc(u,v) = sin(sqrt(u**2+v**2))
GPFUN_sinc = "sinc(u,v) = sin(sqrt(u**2+v**2))"
x = 0.0
## Last datafile plotted: "$grid"
w = 2 * pi
splot [-10*w:10*w] [-10*w:10*w] sinc(u,v)

This just sets up the plot display and a few variables to make it easier. The last command generates the following plot - pretty cool!

Single source output

Let's move the source, and see what that looks like...

Single source, moved 10 units

Now let's add these two sources.

splot [-10*w:10*w] [-10*w:10*w] sinc(u,v) + sinc(u, v+10)

giving

To be honest, I'm not quite sure what this is telling me at the moment. I have w = 2pi i.e. 1 Hz. I'd have to use fw where f = Hz. I also need to have the X/Y axes meaning something useful in relation to time or distance, otherwise it'll be incomprehensible.

Assume X/Y is seconds, so a 1Hz sine will show a full cycle every 1 unit => x*2*pi, y*2*pi:

splot [-10:10] [-10:10] sinc(u*w,v*w)

gives 

Single source, 1 Hz sine

Let's try a higher frequency (f = 10):

gnuplot> freq = 10gnuplot> splot [-1:1] [-1:1] sinc(freq*u*w,freq*v*w)

Single source, 10 Hz

Note the changed x- and y-axis labels - this is basically a 10x zoom on the previous shot. I found using the same axis limits too confusing. Let's assume that this is 100Hz, just multiply the x- and y-axis labels by 0.1. This is now interesting to play with, because this is the frequency area of Kii cardioid behaviour. At 100Hz, the wavelength is 3.44m!! The Kii rear drivers are about 200mm or 0.2m apart. Let's model this by having the sources that far apart in time, which is about 0.58msec or 0.00058 sec. Jeez, that's hardly even going to show, especially when I multiply by 0.1! But obviously it's critical. So I need (Unit 1) - (Unit 2) - they are out of phase i.e. one wired +/-, the other wired -/+.

splot [-1:1] [-1:1] sinc(freq*u*w,freq*v*w) - sinc(freq*u*w,(freq*v*w)+ 0.000058)

2 sources out of phase, 200mm apart, 100Hz

There's definitely something going on, but it's hard to see what it is... However, it is pretty interesting, because it's very different from the result of just applying the same signal out of phase, which results in no signal at all! Weird.

We have yet to add the delay to the second signal to correspond to the distance between them. Basically, as a peak from Unit 1 passes Unit 2, Unit 2 will be emitting a trough of exactly the same depth as the peak's height, because of the delay. How do we do that?? I think I'm missing something, because I need to take off the factor I added to move Unit2 over. Hmm.

Time for some sleep.

Ah, but that's cheating... Kii THREEs arrive!

Firstly...

RIP Siegfried Linkwitz!! He died around 11 September, 2018, at home with his family. Prostate cancer apparently, form which he'd been suffering for a few years. Another drops off the conveyor... and huge thanks to him for all his work and thinking, cogently expressed and in the public domain.

One of the reasons I looked into building the LXMinis was that they were a concerted effort to control in-room dispersion, and thus manage the actual listening experience in a real room, not an anechoic hellhole. This thinking on my part was partially inspired by discovering the existence of Kii THREEs, via the Rational Audiophile's blog. And they were pretty expensive, so although I auditioned a pair, and was absolutely smitten, there didn't seem to be a justification for spending quite that much money, especially if I could build LXMinis and they'd be pretty darned good.

Well, dear reader, I did build them, and they were good! Quite staggering, for the outlay and the relative effort. Earned me big kudos with friends and relatives, too - how could someone make something that sounded like that with a few plastic pipes, crappy MDF and a very secondhand Sony receiver?

However, in the light of the realisation that I'm going to be dead, and they won't give a toot (pretty much... 7x10^9 - ~100??), and after I found some for sale at a greatly reduced price from a pro audit dealer in Paris, I ratched around in the cupboard and found some cash. They were delivered this morning, along with the stands and Kii Control I'd sourced separately.

This is the story of the unboxing, for those who like this kind of thing.

Provided they have the cash...

They arrived in two large brown cardboard boxes, which I checked for external damage, and photographed the several dents and dings before opening, just in case. Apparently the FedEx goon complained about carrying the 15kg boxes to the door - good job he didn't have my job of carrying the stand boxes, at 25kg each!

Interesting lift-out handles for speakers from boxes

There were two tricky bits to the unpacking:

• Getting the white Kii labelled boxes out of the brown cardboard sheaths - involved wiggling them on their sides
• Using the handles pictured above to get the inner speaker carrier out of the Kii boxes - these were very heavy and pretty air-tight, so I had to lock the core and use my feet to hold the outer box down! 

Speaker on box base with accessory box

Once out, the inner box had the bagged speaker and in one case, the accessory box. Removing the speaker from the base was also tricky - I didn't want to put my hand through one of the speakers by accident, so undid one end of the base and slid it off carefully.

Two Euro-cables, 5m Cat6, reviews, Roon trial sub and...  stickers!

The accessory box is very sweet:

• Two Euro plug mains cables
• One 5m Cat6 cable to link the speakers
• Reprints of favourable reviews
• Manual
• A 6 month free sub to Roon for registering for the 5 year warranty
• Stickers!! Where to put these...

Wow. Bigger than I expected...

Although these are "bookshelf" speakers, they are not small! Hopefully when they make it onto a stand they'll be less imposing.

Stand boxes - at 25kg, 10kg more than the speakers!

Building the stands was more complicated, but not especially difficult. Basically, bolt the top and bottom on the legs, fit the spikes, stand them up, put the speakers on the shaped top plate with its decoupling neoprene strips. Some bozo on the computer audiophile forum reckoned he struggled to do this... sigh.

Stand boxes look empty...

Base and top

Sheathed stand tube

Stand tubes, showing cable management hole

First one up, beside LXMini + 1

And they really make the LXMinis look small! Ee. Was this a mistake?

Second base, showing spikes

First tests, with USB and laptop

Connected up with the Kii Control, and they work! Plugged in laptop, and played Tidal stuff to start with, because I could get that to play through the USB port.

The Kii Control

Shortly after that, I switched to plugging in the RPi Rune streamer using USB - it recognised it and switched to using it immediately. Amazing.

Initial setup was about 80cm from the front wall. Sounded good. Moved to about 10cm from the front wall, as this would be handier for safety etc. Still sound good. The Bass Correction was already at -6, which is the recommended setting for Wall placement, so I left it there. Now let's play...