[andyr]

I picked up this URL on "Cable Asylum" and thought it might be of interest to AKSAphiles:
http://www.qed.co.uk/contact/files/genrep.pdf

On the same topic, if any of you have the problem of what speaker cable to use if you want a 15+m (50+' to you Pommies/Yankees!) run to speakers in your bedroom or study - like I did - then you may be interested in some measurements I did recently.

Hugh told me the maximum speaker cable capacitance you really want to think about loading an AKSA up with is 2,000pF.  This is not generally a problem with "normal" speaker cable lengths in an audiophile system - ie. 2-4m - but can be a problem if you are feeding another room.

Because of the low cost of Cat5 cable and the good results which many people have had braiding it a la CvH, I decided to use one jacket for the '+' run (ie. 8x24awg insulated strands) and one jacket for the '-' run.

Anyway, in connecting up the two jackets going to each speaker, you have 3 options.  Each results in 8 wires being used for each banana plug:

1.  all 8 wires in one jacket to '+' and all 8 wires in the other to '-'.  The two jackets merely lie side-by-side in the electrical conduit in the wall space.

2.  2 pairs from each jacket for '+' and the other 2 pairs from each jacket for '-'.

3.  the coloured wire from each twisted pair in both jackets for '+' and the striped wires for '-'.

As you might expect, these configurations deliver different amounts of 'C' and 'L'.  As high 'L' causes a speaker cable to sound bad, the right result is the one which gives you the lowest 'L' while still having total 'C' < 2,000pF for the 15m run!!

Option 1 gave C=315pF and L=0.0115mH
Option 2 gave C=1,840pF and L=0.0026mH
Option 3 gave C=5,360pF but L=.0013mH.

With the lengths I had, I therefore had no option but to go for the simplest arrangement ... 1 jacket for each speaker terminal.  Perhaps I could have risked Option 2 - which would have been nice as its 'L' was about 1/5th of Option 1.  Anyway, it sounds good enough and I can be confident the AKSA is not going to self-destruct!

One final issue (if you do use Option 1) is to make sure the writing on the jacket goes in a reverse direction for the return wire ... so you have an "out and back" configuration.  Bob Crump on Cable Asylum says that wire definitely has a directionality, so you need to be able to switch directions to get the optimal arrangement.

The direction which gives the tallest sound stage is the correct one - which is probably irrelevant for the kind of speakers which you might typically use in your bedroom!  However, it does bear thinking about for your main system.

The third cable parameter which is relevant is R - for 15m, I thought the sum of the cross-sections of 8x24awg wires was sufficient to deliver a low enough R; if I was running more than 15m, I would use 2 runs for 'red' and 2 for 'black'.

And, yes, I used teflon-coated Belden 1585A.  However, this has a PVC outer jacket so, for the ultimate in sonics to your bedroom (d'ya really need this?), you should use Belden 1585LC which has a teflon outer jacket as well !!

Regards,

Andy

[PSP]

Andy,
Thanks for the cool post!  Those measurements are for a 15 m length?  If so, I suppose we could calculate L and C per meter for each configuration.

Peter

[andyr]

Andy,
Those measurements are for a 15 m length?  If so, I suppose we could calculate L and C per meter for each configuration.

Peter

Yes, absolutely, Peter!!

Regards,

Andy

[AKSA]

Hi Andy, Peter,

Many thanks to you Andy for your comprehensive analysis.

I've just done some number crunching on these choices.  It seems that for the additional inductance of Option 1, the 315pF/0.0115mH configuration, a 6R speaker such as the AKSonic will have it's reactance raised nominally by 1.08R at 15KHz, and this will reduce level at this frequency by 1.44dB, something most would be hard pressed to pick.  A portion of the population would pick it, but not too many, and certainly not if they didn't realize it.

Generally tweeters are slightly more efficient than woofers on modern speakers, and many, including the AKSonic, are slightly padded down to bring the efficiencies into line.  Thus it would be possible to easily tweak the tweeter to accommodate this drop in top end;  for those who like to get it exactly right, this is nice to know.

The effect of cable capacitance on speaker response is negligible.  For example, 2000pF has a reactance of 5300R at 15KHz, which is insignificant on a conventional speaker.  However, shunt capacitance on the output of any amplifier will introduce a small phase shift, which will directly bear down on the stability of the amplifier in the 500KHz range, where these things rear their ugly head.  For reasons discussed earlier, and because the AKSA is such a nimble beast with high sensitivity to phase shift, I support Andy's comment eschewing Options 2 and 3.  Quite right too!

Andy, my thanks for your post, and again my apologies for missing the appointment last Tuesday.....!  

Jens, I've rediscovered your CD and am listening over and over to Track 14 of 'My Music'.  I have to say it is absolutely sensational, a beautiful piece with wonderful sonic qualities, astonishing emotional engagement, and a marvellous test for any hifi!  It reminds me strongly of 'The Power of One', one of the best African percussion CDs I've ever heard.  Thank you!

Cheers,

Hugh

[Jens]

Hi Andy and Peter,

Great job! It will be most helpful to those of us without the knack for such mathematicial exigencies!

Hugh, happy to hear you rediscovered my compilation CD! I also love track 14 - it sort of takes you to another place, doesn't it? Peter, what do you think?

Cheers,

[SamL]

Andy,

Interesting finding. Will appriciate if you are able to do a subset of test 3 but with a single run of cat5 cable.
Connect 4 coloured wire for '+' and the other 4 striped wires for '-'.
I am thinking of wiring for HT surround and a single Cat5 will be nice and simple.

Cheers,
Sam

[andyr]

I may be able to, Sam, but not in the near future.

However, I would estimate that the result will be similar because it is the fact that we are using one wire from a pair for '+' and the other for '-' that is causing the high capacitance ... so it will be (almost) the same whether you have 2 pairs or 4 pairs.

Do the maths and see what the capacitance is going to be for the length of cable which U need for your HT surrounds.  You may be able to get away with Option 2 - which in your case would be using two twisted pairs for '+' and 2 for '-'.

However, if you go to:
www.vandenhul.com/artpap/awg.htm
you can get the resistance per metre (ie. per 3 feet) of different guage copper wires.  You may find that just 4 wires per run does not get the resistance down low enough for the length you need, and you have to use 8 wires like I did.

The "rule of thumb" is that R of the wire is no more than 0.1ohm, for best results - though for bedroom speakers, who cares!  For HT it is probably more significant.

Regards,

Andy

[PSP]

Jens,
That is an outstanding compilation you have there... a delicious tortuous road test of exceptional music and sound that I now use all the time to evaluate changes I make to my system.  

And cut 14... the music is trancendant, and the imaging of the purcussion is incredible.

My current favorites are #11, probably the best orchestral recording I've ever heard, and #3 is just plain crazy.

Many, many thanks / Peter

[AKSA]

Jens,

That track Peter commented on - #11 - I certainly agree with him, but I can't place it.  It sounds like either Shostakovich or Prokofiev;  can't pick it.  Can you tell me what it is?    

It is an absolutely ravishing recording, beautifully produced.
But then, I'm something of a musical tart, I like the lot;  love the Titanic recording too.    

Cheers,

Hugh

[PSP]

Hi Hugh,
It's a movement from Shostakovich's 5th Symphony....

Peter

[Jens]

Hi Hugh,

Peter is correct (thanks, Peter) - track 11 is the second movement of Shostakovich's 5th Symphony. It's an old Decca recording that is no longer available.

In that heap of CD covers you have lying around there is a cover for the CD. It has a bonsai tree on the front, on a greenish background. The playlist is on the reverse side.

The playlist is as follows:

1. Yello: Get On (from Motion Picture)
2. Eva Cassidy: Over the Rainbow (from Songbird)
3. Mussorgsky: Pictures at an Exhibition, Promenade/Gnomus (from Dorian DOR-99117, gold version)
4. Mickey Hart: Temple Caves (from Planet Drum)
5. Jennifer Warnes: The Panther (from The Well)
6. Johan Strauss: Die Fledermaus, Act III, excerpt (from Deutsche Grammophon 457 766-2, Original-Image Bit-Processing version)
7. Anúna: She Moved through the Fair (from the compilation The Celtic Circle)
8. Titanic: Hard to Starboard (from the original soundtrack)
9. Sinead O’Connor: In My Heart (from Universal Mother)
10. Kodo: O-Daiko (from Heartbeat Drummers of Japan)
11. Shostakovich: Symphony No. 5, 2nd Movement, Allegretto (from Decca 425 066-2)
12. Gladiator: The Wheat/The Battle (from the original soundtrack)
13. Patricia Barber: Romanesque (from Café Blue)
14. Bliss: Song for Olabi (from Afterlife)

About the last track: Bliss is a Danish group, just came out with their second CD (not nearly as good as their first one).

The above are all exceptional recordings - in one way or another. I thought they might inspire some of the other guys here in the forum.

Cheers,

[Seano]

Just to get back on topic.........

I'm just about to replace my DIY speaker cable (cheap Belden 9259 made up to the Risch recipe) for QED Silver Anniversary Bi-wire speaker cable.

The reasons for doing this are mostly practical.  I've just moved house to a large farmhouse which has an ideal stereo room - the breezeway.  This is a 6 metre by 20 metre room with 4 metre ceilings and glass/open double doors at both ends. Placement of the stereo cabinet on the side wall means that the speaker cable runs to the end wall where the speakers will be are up to 8 metres. And not only do I have sufficient material for a bi-amp set up but I couldn't be stuffed making it up (8 of 8 metre cables anyone? After buying 70 metres of base cable? No way). The other reason is that the QED cable was supplied and delivered from the UK for AU$20/m which is under half of what it can be had locally.

But now I'm reminded that the AKSA 100(N?) can cope witha max capacitance of 2,000 pF.  I'm not much of a stats person nor can I even pretend I understand the math and measurements behind audio gear. But I checked with QED and was told the parallel capacitance of the Silver Anniversary Bi-wire is 21.59 pF/m and a loop resistance of 0.0149 Ohm/m.  Am I right is guessing that for each 8 metres length left and right then the total capacitance is about 173pF and resistance is 0.1192 Ohm???

Or is the math a little different?

[andyr]

Seano,

Yez yore maths is correct.  Even if those QED people don't understand metric and they've quoted U the 'per foot' figure, 3 x 173pF is still waaay under the danger zone as far as an AKSA is concerned.

Now, before you've settled into your new listening room (and couldn't be buggared to change anything around) .... why don'tcha try a simple experiment to help the rest of us?  Are U man eneough ... coz the downside is U might have wasted the $20pm for the QED cable!!  

Go buy some Cat5 cable - Belden 1585A if possible - and compare this to your new QED cable.  Maybe the Cat5 will give you a more satisfying moosical experience??

Regards,

Andy

[Seano]

I've actually got a couple of bins (ie. many metres) of Cat5 kicking around the office.  More than enough to do the job in fact. But again I was being lazy. Plus it is the non teflon variety which people seem to poo-poo anyway. And I've never quite been able to get the hang of the construction method..........call me stupid but no-one seems to be sticking to a consistent recipe.

I have built speaker cable for a mate from this stuff for his Krix Brix bookshelf units.  But I simply took two sets of four twisted pairs from each end of 3m of cable and soldered them together without unpacking the actual cable. Never did test their performance electrically but the mate is happy.

In the new house there are just too many other jobs that need doing (did I mention nearly two acres of garden?) and there is nothing worse than working in silence.........

[AKSA]

Seano,

Yes, you are right.  No problem for the AKSA whatever.  Rock away!

Hmmm.  Your music must be thick and heavy.......

A farmhouse huh?  How far out of Bourke?

Jens, thank you for your playlist!  I have tidied up my heap!

Cheers,

Hugh

[Seano]

We are bout a half hour drive provided it's not raining, frequented by kangaroos or chewed up by traffic. Life at the end of a long dirt road is quite different. But it is proving to be fun despite all the work and travel.

You should see the size of my shed too. Plus I have the pick of new projects - either a Moke or a Morris Isis. Think I'll pick the Moke....  
Mind you I must finish and flog the Rangie first.........dammit!!