A couple of questions: Stereomour wiring; Klipschorn impedance

lmalinofsky · 8010

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Offline lmalinofsky

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Hi all, I got my Stereomour kit last week and am about to start the point-to-point wiring underneath.  I notice the black and red hookup wire supplied is much narrower gauge than that shown in the manual.  I assume this nevertheless is going to work as well in terms of handling necessary current, etc.?   I'm certainly not complaining-- this wire looks easier to work with.

I have a pair of Klipsch corner horns manufactured in 1972, all original drivers and crossover.  I'm wondering what impedance I should wire the output transformers for...   I had always been told these were 16 ohm speakers, though I note the current production models are represented as 8 ohms.  I wonder whether anyone with K-Horns has experimented with 8 vs. 16 ohms to see which is better.  In the meantime I'm scratching my head wondering how to wire these things!

Any advice most welcome!

Thanks,

Leon


Leon Malinofsky


Offline Paul Joppa

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Reply #1 on: January 30, 2011, 11:37:59 AM
Is there a nameplate on the speakers, maybe in back or by the input terminals?

You can measure the DC resistance. Nominal impedance (at audio frequencies) is greater than the DCR, around 30% greater for direct radiators, more like 50% to 100% greater for horns.

Klipsch has an active forum, you might find some really knowledgeable experts there.
« Last Edit: February 02, 2011, 08:53:56 AM by Paul Joppa »

Paul Joppa


Offline lmalinofsky

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Reply #2 on: February 02, 2011, 06:51:47 AM
Paul, Thank you so much for the referral to the Klipsch forums.

Since I'm messaging you, and since (I think) you're one of the folks to whom mistakes in the manual should be reported, let me mention this one;  maybe it will help someone.  I took a screenshot of the manual page and posted it here:  http://plexipages.com/clip.jpg -- it shows the picture to be correct, but the descriptive text to be in error.  Basically, it specifies the wrong terminal number on the power transformer.

I don't know if a reply to this thread will necessarily come to your attention, so if you see the image by following the link and it makes sense, by all means let me know you got it.

I very much appreciate your help!

With best regards,

Leon Malinofsky

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Offline Paul Joppa

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Reply #3 on: February 02, 2011, 09:03:12 AM
Got it - thanks! I alerted Doc B who keeps the manual files.

I use the "show unread posts" whenever I check the forum, so I did see this. (You can also send me a PM by clicking on my name - the PM link as at the bottom.)

Have you found an answer to the impedance question yet?

Paul Joppa


Offline lmalinofsky

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Reply #4 on: February 02, 2011, 10:22:00 AM
Paul,

Thanks for routing the suggested change to The Man.  <g>

I have gotten a few responses so far to the impedance question.  I thought you might be interested, so here are all three:

Answer # 1: 
If you stay with the original xovers, I would use the 16 ohm tap.  If you switch to an xover that has a bi-wire strap connecting the LF and the HF, I would run the LF and HF on separate taps depending on room acoustics. 


Answer #2: 
For stock k-horns and crossovers I would say 8 ohm taps.  I have tried different taps pon amps with my k-horns and 8 ohms always seemed to work best for me.  IIRC the stock corssovers were designed for 8 ohms, of this I am pretty sure.  I am also sure someone will chime in very soon with a definitive answer.


Answer #3: 
If you are building some 2A3 amps, I would also take the time and spend the money to, at the very least, update the crossovers in your K-Horns. The basic change would be the capacitors, as these would have drifted out of spec over the years. hYou could actually do that first and compare the sound with your present amp.

The other possibility would be to build a totally new set of crossovers that are a constant impedance, something that your 2A3 amps (most tube amps) will like. I built a low order, constant impedance set of crossovers for my La Scalas, and power them with my 2A3 amps and they are simply magic.

The lower order crossovers work for me for a couple of reasons. I don't play music at extreme volumes, which means they still sound good. At higher levels, the driver overlap can get a little mushy and blurred. The crossovers that are higher order or extreme slope, for most people don't sound as good until they are driven at higher levels. Since the 2A3 amps are only 3.5 watts, this is more difficult and the amps will give out...


-------------------------------------------------


I have to admit I like answer #3-- this is the kind of thing I would do, and it has been tested by a K-horn user.  I don't know whether the fellow who recommended eight ohms had current crossovers, or my crossovers, however.  I think I am going to wire them at 8 ohms for now, though I'm not sure what happens when you wire output transformers to 8 ohms and the speaker is really 16.  I seem to remember one fellow on these forums asking about Z-out for the various impedance wirings, and his experience was the lower impedance he wired for, the better his Hereseys sounded.  From this I conclude, probably erroneously, that it is better to wire for too low than too high.  Hence, 8 ohms....

We will see!  [grin]

Leon Malinofsky


Offline JC

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Reply #5 on: February 02, 2011, 10:39:48 AM
As a general rule of thumb, having the amp at lower output impedance than the speaker the amp is driving is safer than the other way around.  A lower amp output impedance will mean a slight loss of power, but the amp will be happy.

If the amp output impedance is higher than the speaker load impedance, you run the risk of asking the output of the amp to supply more current than it wants to.  At the least, the output tube will be less happy than it would otherwise be, and possibly have a shorter life-span.

Again, just a general rule of thumb.

Jim C.


Offline Jim R.

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Reply #6 on: February 02, 2011, 04:16:09 PM
Leon,

I'd also vote for number 3, especially the part about the caps in the x-overs being way out of spec now if they have not been replaced in the last 20 years or so.

I'm not really sure about the constant-load crossovers, but in theory they should be better, though I suppose that in practice, the average listenig volume as well as the design of the amp will be the determining factor.

BTW, I have a completely stock pair of 1977 cornwalls that I'm definitely planning on overhauling the crossovers on, as well as a few other tweaks.

-- Jim

Jim Rebman -- recovering audiophile

Equitech balanced power; uRendu, USB processor -> Musette DAC -> 5670 tube buffer -> Finale Audio F138 FFX -> Cain and Cain Abbys near-field).

s.e.x. 2.1 under construction.  Want list: Stereomour II

All ICs homemade (speaker and power next)