New speakers and bi-amp questions .

I bought some new  (at least to me) speakers  a few weeks ago . I’ve wanted them for
almost 25 years  but couldn’t find a store reasonably close that had them back when they
were for sale in the late 80’s.
A pair of Infinity kappa 9’s  .
I bought the stores last pair of kappa 8’s instead back then , I got a killer deal on them too !
But always wanted these babies  .

I planned on bi-amping these before I bought them because they need a lot of  hi-current
power  to work right . So I was going to use my FPB 300C to run the  lows  and was
thinking of getting a pair of M125’s for the  mid-high sections . But for the heck of it I
hooked my ST120 up on the mid-high section and I’m amazed at how well it works there
. I was sure the 60wpc from reading some would be not enough .  ( It wouldn’t run the full spectrum of  kappa
8’s very well  at all ) .  But so far they are sounding  pretty good like this .  So I might just
get another ST120 with the  Octal board for these instead of the M125's ? I have alot of extra 6SN7’s
from the SP14 builds .   
I’ve read a few posts where the designer of the speakers liked how they sounded when
run with  S.S. on the lows and tubes on the mid - highs .

 So.  Questions #1  I've read  when biamping , the amps should have the same or at least close
input sensitivity - gain to work right so you are not driving  one or other other amp and
speakers  to much ?  
So the ST120 needs  1-1.25v. to  drive the amp to 60 wpc and  the FPB needs 2.35v to
drive it  to 300 wpc . Full volumes .
Since my ST120 dosen’t have the attenuator in it could I just build like a passive
“preamp”  with just an attenuator and a pair of inputs and outputs and put it in at the
outputs of my SP14  before the ST120  to turn the gain down before it gets to the amp so it
doesn’t top out before the FPB does ?  Would that work ? Also is there a easy way to
measure the output voltage of the preamp so I could match the input voltages close ?
The way it is now the top end  does sound like it gets louder faster with the volume . And
the bass is a little weaker than I think it should be .  I  think it should sound right once  the
input bias are matched to the amps . But they still sound good . I don’t want to crank it up yet
and hurt anything .

Question #2 . How do the ST120’s hold up to some brief 2 ohm loads ? The speakers are
rated at 4 ohms but they briefly dip down to 1-2 ohms at one frequency on the top and on
the bottom  .  I don't normally listen to music real loud but I will sometimes crank it up  when
no one else is home .

The Speakers when I got them were WOOPED !  I wish I would have heard them in my
system before I bought them ! He had them hooked up to a little crappy reciever when I
auditioned them  and couldn’t properly power them.  I might not have bought them !
The grille cloth looked like they housed a moth collany for ten years. At least I knew that
before I bought them though . And the cases had some little water damage to them .  But
when I got them home and hooked them to my system   I heard  some dissapointing
sounds  coming from them . The woofers were supposedly refoamed  but one voice coil
was seriously scrapeing and the foams were comeing loose at the glue and  two dust cups
smashed in and crackaling ! One of the low tweeters was buzzing , the two high tweeters
were not working at all , and  the rear tweeters were  working very poorly. OH ! and
whoever  reinstalled the woofers wired them wrong! In parallel instead of series .
Needless to say the bass was almost non existant . So after  three weeks of messing
around  waiting for caps and foam kits .  Two grill re-cloths , two oak case repairs ,one
used woofer ,four woofer refoams ,voice  coil re-centers and all new dustcaps . One new
(used) low tweeter , one high tweeter and  complete crossover re-caps they are sounding
and looking   ALOT better .   I did get them for a decent price though, but I had to put alot
into them to get them sounding right .

Man the crossovers were a pain . Alot going on in there .  Alot of hot glue    and non standard  cap values .
Not dynaco but  ...   
Before.




After.






Thanks to some info here  and Building  my  ST-SP & PH builds  I was able to figure out what was wrong with these monsters . A couple years ago i would never have even attempted it .  There was a total of 6  bad or very out of spec capacitors in both crossovers  . From my research reading the electrolytics usually go out of spec from age and the  film Solons usually stay good .  But it was just  the opposite on these , the Electrolytics all checked in spec and  all the bad caps were the Solons. One of the 3uf caps actually read .02uf . Figures since I replaced the films  with new Solons    since I didn't want to spend  what  the Sonicaps would have cost !!



I have to find a place to put the ST120 now .



Kappa 9's on left   8's on right .

Wow! That's quite a complex crossover. I would've replaced every single one of those electrolytics and iron core inductors but that's me. Being on spec is only half of the issue. Film caps discharge faster with less resistance and just sound better. At the very least I would bypass every one of those electrolytics with a small (0.1uF) film cap.

Having way too much fun over there ...

You mentioned attenuating the ST120 when using it as a high side amp - sounds simple enough if you do that on the input side. You've already got a custom case, so what's a couple more holes? Wouldn't even need to be all that accessible as this is something you'd only need to do once to get the proper balance between the top and bottom ...

Something as simple as cutting the ends off a couple RCA cables and wiring in a 50-100k linear pot should be good for testing the system. You don't need much as we're only talking line level signal. You can go with a dual stepped attenuator, or use separate controls like I did for balance control. Here's what I use for a center channel from my Oppo SACD to drive a Carver Cube ...



PS ... that was just supposed to be temporary, but temporary has been a couple years now. I suppose one of these days I'll have to do a better job of cleaning the applesauce out of the custom case, but I think it actually adds a certain "app...peel" to the sound ...   

And not to forget, all your power gets sucked up by the low end. I assUme the crossover point the ST120 would be dealing with would be over 300hz and the amp should provide plenty of muscle for most any load up to wall breaking SPLs.

I'd also think one of the major reasons folk lean towards SS for the low side amps is that SS can provide great heaping gobs of raw power at much lower cost. Tradeoff is that SS tends to hard clip, and that's where cones go flying ... I'd consider trying your ST120 on the bottom also - the Kappa 8's are rated at 89db, and that's exactly the same as my McIntosh XR16's. The ST120 drives those to very strong levels with clarity and grunt using a quad of KT120's. I like it LOUD and regularly put the room in "hover mode", and have never had the dual attenuators up over 8, so there's room to spare.

corndog71 wrote:Wow!  That's quite a complex crossover.  

You said the same thing about mine if I remember right. And here I thought I was "special". Remember these?



Finally picked up the caps to do my XR16's - the D cell battery is for a point of reference ... them things is HUGE!




Be cracking the cases shortly, but still    about how to support those gargantuan ERSEs. I figure to stack them tall and add a sandwich board over the top of the existing board for additional support. Maybe even triple stack them so the BIG caps are supported both ends and run leads to the original board instead of mounting them directly. I may also relocate the crossovers to the bottom of the cabs and just run wire to the terminals - right now those are on the back of the board.

Nice thing about 100 pound speakers ... plenty of real estate inside.

sKiZo wrote:

In your case I would chuck the original board and rebuild it point-to-point.  You like doing it yourself.   

Just remember to keep the coils perpendicular to each other.  Use a chunk of peg board and lots of zip ties.  Once you get it all together screw the peg board down.

Oh, and get some better wire. 16 AWG and preferably solid core.   

I replaced all the caps on both crossovers , electrolytics included . I've read about  crossing over the caps with a small  .1uf cap but didn't know enough about why  to try it .  Three of the film caps were already crossed over with a .01uf cap though . I don't know  enough about this yet  to  start changing things like the inductors , that and the cost of all of them .  Doing the caps was it for now .  Besides they are all back together . I'm thinking of doing the kappa 8 crossovers  eventually  may be I'll do them up "right" .  
They used 12 ga wire on all the wireing in both of  these speakers too , even the tweets .

Skiz , It keeps me out of trouble .  
At least you have room for the big caps on those boards .  I can't imagine finding space on mine for the 2000uf of film caps that just each woofer section takes . That and the cost !  Just zip tie them down and get yourself a hot glue gun and  glue them down . Everything on mine was  hot glued and they were a pain to get loose !

I was thinking of just making a small enclosure  with just a  2 channel attenuator  and two pair of rca jacks in it  and putting it between the SP14 and ST120 so I can turn down the input to that amp ? That should work.  I  don't want to add any more to the pre amp thats all done    .

I can't remember where they get crossed over at , I think 80 Hz, 700 Hz, 5000 Hz, 10 kHz  , but the woofers do use the most power .
 I think they are being generous about the 89 db rating ?   I tried the ST120 on the kappa 8's  and they just didn't have it .  They sounded WEAK , not good at all .  They Run my kappa 6's nicely though , where the ST120 usually is . There is no way it would run  the 9's woofers .  For years I used my 200wpc Carver on the 8's and they sounded good , but when I put the 300wpc FPB300  (and the power doubles all the way down to 2 ohms I woln't ever clip this thing ) . on them they sounded like different speakers ! Sooo much better . They Like Power .  Thats why I figured on bi-amping the 9's , Give the lows all that power they need , and since the mid - highs don't need as much  use the  ST120 on them .  

You like the oppo? I'm thinking on getting one of their blu ray machines .

Since I didn't get many opinions on whether a attenuatur  between the pre  & the amp would  work to balance out the input sencitivity mismatch I built a simple with  box with an attenuator & inputs and outputs  in it . I worked out very well , the sound is much more balanced between the highs and lows  now rather than  the weak bass without the  attenuator now that I'm able to turn down the bias to the  ST120 .  
Its  a small Goldpoint case with a  old stereo attenuator  I had around . Since  I was too lazy to build a wooden box to match .