High Current Amp/Pre-amp recommendation needed - Power for Infinity Kappa 9 pair

[edisonbaggins]

Hey QQ family,

You did such an amazing job (eventually) recommending what I needed to power a full-range Quad Station, that I'm coming to you once again!

I have inherited a pair of Infinity Kappa 9 speakers. They're behemoths. And certain frequencies can go below 1 ohm. They need a high current beast of an amp. Like, 1 ohm stable.

Of course, you know that I'm cheap. I want an amp that will make the Kappa 9's sing and not get fried, but as budget as possible!

I've been doing my research and checking craigslist and ebay. I have some ideas I'm kicking around, but I'd like to get unbiased advice!

Oh, I'm older and wiser now and know I'll need a pre-amp! I suppose this will all be sourced by a tuner, TT and/or CD player.

Thank you, kindly.

Baggy

 

[Sonik Wiz]

Hey QQ family,

You did such an amazing job (eventually) recommending what I needed to power a full-range Quad Station, that I'm coming to you once again!

I have inherited a pair of Infinity Kappa 9 speakers. They're behemoths. And certain frequencies can go below 1 ohm. They need a high current beast of an amp. Like, 1 ohm stable.

Of course, you know that I'm cheap. I want an amp that will make the Kappa 9's sing and not get fried, but as budget as possible!

I've been doing my research and checking craigslist and ebay. I have some ideas I'm kicking around, but I'd like to get unbiased advice!

Oh, I'm older and wiser now and know I'll need a pre-amp! I suppose this will all be sourced by a tuner, TT and/or CD player.

Thank you, kindly.

Baggy

That's a good purchase Sir!
I have Infinity Kappa 8's for the front Chs & Kappa 7 for the rear. The K7 is easier to drive then the K8's. Just like your new speaker the ohmage drops down very low & you are on the right path looking for an affordable high current high power amp to drive them, When I first set mine up I hooked them up to my old Kenwood integrated amp & they just sucked the life out of it.

I went shopping for something better. Top on my list at the time was Hafler cuz I really appreciated the FET output technology, and Adcom power amps. They both seemed good quality good value amps at the time.

Where I bought the speakers they also sold Hafler & Adcom. I was advised that if I want to get the most out of the Infinity's the Adcom was the way to go. At 200 WPC , very good damping ratio, & the bipolar outputs were able to dump loads of current as needed I went with the Adcom 555's. Another thing I like about them is they have whats called dual mono construction. The only shared component between the two chs is the transformer power primary winding. Individual secondary winding's, rectifiers & filter caps for each power amp boards.

All these years later it's been an excellent choice. I have no fried tweeters because my amps never clip & bass so deep you can feel it vibrate my basement's concrete floor.

On Ebay it seems the price for an Adcom 555 power amp is all over the place. But look around because obviously that's one power amp I can reccomend. You might also see if theres a lower power Adcom stereo amp that together might be less than the 555 and you could bridge for much higher output power.

Good luck, have fun & let me know how this unfolds!

 

[edisonbaggins]

That's a good purchase Sir!
I have Infinity Kappa 8's for the front Chs & Kappa 7 for the rear. The K7 is easier to drive then the K8's. Just like your new speaker the ohmage drops down very low & you are on the right path looking for an affordable high current high power amp to drive them, When I first set mine up I hooked them up to my old Kenwood integrated amp & they just sucked the life out of it.

I went shopping for something better. Top on my list at the time was Hafler cuz I really appreciated the FET output technology, and Adcom power amps. They both seemed good quality good value amps at the time.

Where I bought the speakers they also sold Hafler & Adcom. I was advised that if I want to get the most out of the Infinity's the Adcom was the way to go. At 200 WPC , very good damping ratio, & the bipolar outputs were able to dump loads of current as needed I went with the Adcom 555's. Another thing I like about them is they have whats called dual mono construction. The only shared component between the two chs is the transformer power primary winding. Individual secondary winding's, rectifiers & filter caps for each power amp boards.

All these years later it's been an excellent choice. I have no fried tweeters because my amps never clip & bass so deep you can feel it vibrate my basement's concrete floor.

On Ebay it seems the price for an Adcom 555 power amp is all over the place. But look around because obviously that's one power amp I can reccomend. You might also see if theres a lower power Adcom stereo amp that together might be less than the 555 and you could bridge for much higher output power.

Good luck, have fun & let me know how this unfolds!

I've got my eyes peeled for a 555! Would it make sense to consider one amp for the bass woofers and another for the mids and highs? From what I understand, you can power the lower and upper end separately somehow?!
Also, any particular preamp recommended to get the most out of the Adcom?
Thanks!

 

[Sonik Wiz]

I've got my eyes peeled for a 555! Would it make sense to consider one amp for the bass woofers and another for the mids and highs? From what I understand, you can power the lower and upper end separately somehow?!
Also, any particular preamp recommended to get the most out of the Adcom?
Thanks!

Your Kappa 9 might be different from my K8, but, my speaker only allows for bi-wiring, not bi-amping. The former is based on the notion that certain cable designs one might be better for the highs & another be better for the bass. You know like Monster Cable liked to do. Others may differ but I think it's nonsense. Bi-amping does hold good value but you must make sure your speaker can do that or things will go KABOOM!

In all the years I've had the 555's I've only had to send 1 of them in once for repairs. When 5.1 came out I bought another one so I actually have 3, 555 power amps.

My pre-amp I also bought at the time, has run flawlessly all these years & it is the Adcom GFP-555:

You have a lot more choices & freedom in selecting a pre-amp. Maybe get one those with new fangled remote control?

How is the foam surrounds on the woofers? Only repair/maintanace I've needed is to have the woofs re-foamed.

So what are ya doing here, setting up a dedicated stereo only rig?

 

[DuncanS]

In the mid to late 70s we used to use H&H Power Amps to drive our PA rig speakers (Electrovoice Bass Horns, Mids & Tweeters). They seemed to be able drive/handle anything without going phut, including a Power Drill! Maybe not super-low distortion. They can be picked up relatively cheaply 2nd hand. Multi-amping is good, its also how we did our PA.

...... and Sonik I agree with you on cables/biwiring, mystical drivel peddled at daft prices! No physics behind any of it, but it means they sell more cables.

 

[edisonbaggins]

Your Kappa 9 might be different from my K8, but, my speaker only allows for bi-wiring, not bi-amping. The former is based on the notion that certain cable designs one might be better for the highs & another be better for the bass. You know like Monster Cable liked to do. Others may differ but I think it's nonsense. Bi-amping does hold good value but you must make sure your speaker can do that or things will go KABOOM!

In all the years I've had the 555's I've only had to send 1 of them in once for repairs. When 5.1 came out I bought another one so I actually have 3, 555 power amps.

My pre-amp I also bought at the time, has run flawlessly all these years & it is the Adcom GFP-555:
View attachment 55441

You have a lot more choices & freedom in selecting a pre-amp. Maybe get one those with new fangled remote control?

How is the foam surrounds on the woofers? Only repair/maintanace I've needed is to have the woofs re-foamed.

So what are ya doing here, setting up a dedicated stereo only rig?

I have my eyes on some GFP-555 and GFP-565 pre-amps.
Just inherited these and am seeing if I can get them working, on a budget, as a project. Out of curiosity, mostly.

It seems the Kappa 9's are truly designed to be able to bi-amp. They have separate posts for the high-end and the low-end.
Check out this guy's amping strategy. What I'm thinking is I might be able to save money and get better performance by dividing and conquering here, rather than looking for one BEAST amp that can handle these things full-range.

My K9 amping strategy that works for me:
1. Always divide and concur by bi-amping.
2. Put the higher fidelity / higher cost amp on the top. Don't worry about the high end impedance dip.
3. Never put an amp you care about on the bottom unless it is one you know is designed to handle the high current load of the low impedance dip.
4. You don't need a hi fidelity amp to drive woofers. Use a lower cost, high watt "class D" amp on the bottom. I use a Crown 2500 XLS that costs <$500 new and has a built in active crossover. I have to turn its gain down to 3/4 or it generates too much bass from my K9's.

https://audiokarma.org/forums/index.php?threads/kappa-9-bi-amp-strategy.736060/

So, let's get creative. One amp for the bottom, another for the top. Let's save me some $$, but make these puppies sing!
Can a GFP 555 or 565 work with 2 amps? Or do I need 2 pre-amps also?

 

[edisonbaggins]

I think you can truly bi-amp these things:
http://www.infinity-classics.de/technik/manuals/Kappa_9_technical_sheet.pdf

 

[edisonbaggins]

Emotiva sales recommends their XPA-2 Gen 3.
I have a Crown D150A I could potentially press in to service. Just thought I'd throw those tidbits out there.

 

[edisonbaggins]

Brands that I'm looking at, because they might be enjoyable and in my price range are:

Crown
Emotiva
Kenwood (Basic Series)
Adcom
Nad

Any others I should be considering. Of those listed, any models I should particularly look at?

I wonder if, because of the possibility of bi-amping, if I can go down in wattage, while staying high current. E.g. can I look at the Adcom GFA 535 and 545, as well as the 555? That would open up much more stock.

 

[edisonbaggins]

Interestingly, the Kappa 9's can be run in "normal" mode or "extended" mode. Normal mode produces a bit less bass, but avoids the amp-killer nature of these beasts. I very well might try that first.

 

[DuncanS]

So, let's get creative. One amp for the bottom, another for the top. Let's save me some $$, but make these puppies sing!
Can a GFP 555 or 565 work with 2 amps? Or do I need 2 pre-amps also?

I think you can truly bi-amp these things:
http://www.infinity-classics.de/technik/manuals/Kappa_9_technical_sheet.pdf

Yes it does look like you can easily bi-amp as looking at the datasheet the Kappa 9 have the filters in-line with the connections, so one amp for Bass and one for Mid/Treble.

If you drive 2 amps from one pre-amp you will halve the impedance seen by the pre-amp, so the output level may well drop, depends on the driver capability of the pre-amp. So long as your power amps have a 'reasonable' input impedance (say a few to 10+ kOhms), then it is unlikely that the pre-amp output driver would suffer any ill effects. Worth trying.

 

[Sonik Wiz]

Interestingly, the Kappa 9's can be run in "normal" mode or "extended" mode. Normal mode produces a bit less bass, but avoids the amp-killer nature of these beasts. I very well might try that first.

As you & DuncanS said the K8/9 speakers can be used as bi-wired or bi-amped & I had to dig out my own owners manual to verify that. You have a good short list of amps there. I respect & tend to lean towards Adcom, Crown, Emotiva & also Anthem.

Even tho I highly approve of bi-amping it's not my thing & others are more qualified to comment. What I can contribute is if you are using different brands for bass/high try to dtermine if they invert the polarity from in to out or if they match the input. Otherwise there is the chance that the woofer will be opposite phase of the mids & highs & you will be quite disappointed. If you can't determine this from tech specs then a quck listen will show if something is wrong. In that case revrse the polarity on the bass or mid/treble (not both) & give a listen again.

Touching on something Duncan said, you can simply run two power amps from a single pre-amp & technically that is bi-amping. However it is much more beneficial to have a low pass/high pass filter at line level before the power amps. Otherwise you are running both the low/high amps at full bandwidth negating a large part of the benefit of bi-amping.

I run my Kappa 8's in the extended mode. It really makes a noticebable improvement. I'd say if you can't do that the you are using a poorly matched amp for the speaker.

I still remember a review on the Kappa 9's way back when. The author remarked that the Kappa 9's would be regarded as world class audiophile speakers if only they cost three times as much! At one point Infinity came out with remarkable collection of innovative designs including electrostatic hybrid models & the Prelude line, etc. In retrospect I think Nudell & team made a big effort to build the brand with the intent of selling out. Eventually they did to HK & the "reward" was crap like the Infinity Micro II HT speakers. Absolutely the worst speakers I've ever heard & that includes Chevy Belair AM radio with dashboard 6x9.

But I digress. Anyway, again, good purchase.

 

[JimHansonDC]

If you don't mind a bit vintage there are a number of Carver amps that deliver massive amounts of power and they are relatively inexpensive. Especially if you're going to bi-amp and need at least 4 power amps. You still only need one pre-amp just get a decent splitter cable.

Edit: I was assuming running these as mono amps, you can do with two otherwise.

 

[gene_stl]

I have been "quad amping" since 1977 and would never go back. This is a golden age for it because there are wonderful dsp systems almost for free that can do so many wonderful tricks besides just being a crossover. (dBx Drive Rack, Behringer DCX series, mini-DSP has multiples, all the pro companies have dsp input modules for their power amps. The pricing of these compared to "audiophool"products is a pittance.)

Also since power amps are pretty tough and long lived there are lots and lots of them available for almost free. As some may remember I sort of missed out on quad "back in the day" (never actually heard it neither in a store nor at anyones house in spite of being an active audio nut. I am sure I would have gotten the bug if I had. So I focused on building the best stereo I could build)

After deciding to get up to speed on things more modern and discovering multi channel and hi rez , I started looking around for power amps. Like @edison baggins I am very VERY cheep. I loathe and detest overpriced gear. In the year or two since I have gotten back into audio, without even trying, and spending what amounts to small change, I have collected a pretty giant stack of power amps. I recommend that you look at Crown professional PA amps. Some of them have dsp inputs that allow you to not have a crossover. There is a guy here in St. Louis that (see ebay "rescueaudio llc") who sells very reasonably and if you are active duty or a vet he will give you a killer deal. He donates a lot of his sales to veteran organizations.

even tho I got a stack of Crowns (from Tim at Rescue Audio) before that happened I found some other Crowns in the Wild for like $40 for a 300 wpc XLS 602
and got a couple of Haflers (great amps but no protection circuitry.) and a Carver pro amp and a Rotel power amp that is a thing of beauty internally.
So many ways to skin the cat. Haven't even mentioned and hardly thought about Class D amps which also are almost free.

I am a bi amping evangelist. I would be very happy to help you quad amp (or however many you want) this system.

 

[gene_stl]

Bi amp? post #6


This is a nice dated piece from 1986 which I have been referring people to since I got onto the internet.
https://www.audiocontrol.com/downloads/tech-papers/tech-paper-102.pdf
https://www.audiocontrol.com/downloads/tech-papers/tech-paper-104.pdf

Also read the March 1969 issue of Radio Electronics which has an article by the Late Great Norman H Crowhurst and English audio engineer.
https://www.americanradiohistory.co...ronics/60s/1969/Radio-Electronics-1969-03.pdf
I feel that I became an audiophile exactly when I read the above mentioned article. It explains how active crossovers eliminate intermodulation.
starts on Page 32.
That was in March. In October he showed you how to build one:
https://www.americanradiohistory.co...ronics/60s/1969/Radio-Electronics-1969-10.pdf
Pages 42,43,44
Those two articles changed my life.
I was in the process of home building an electronic crossover using op amps based on info in Walt Jung and Don Lancaster books.
I had etched and was drilling a circuit board.

Then I ran into THIS:
https://pdfs.semanticscholar.org/f3...417.1160101081.1558408539-44099534.1558408539
The famous Linkwitz 1976 article on how to do it right.

The Pioneer Series 20 (Pioneer Elite) D-23 was I believe the first commercial product to incorporate the Linkwitz criterion for preventing shift in the radiation pattern at the crossover. When the Pioneer came out I threw my project away. I think the Pioneer Elite/Series 20 D-23 crossover was designed by Pioneer engineers before the Linkwitz article(s) were published.

I don't have a mini DSP yet. But it is likely just a matter of time. The more time has gone by since the above the more ways there are to skin the cat. You can buy kit or assembled circuit boards from all over. mini DSP. mini DSP even lower priced clones from Dayton audio and China
Lots of folks make crossovers now.

In my opinion you should open the speaker box and wire straight to the drivers. You should include fuses and sometimes for tweeters series capacitors that don't affect the response in the drivers range. If you have more drivers than amplifiers (ie bi amping a three way) you need to leave part of the crossover in place. This may require careful examination of the speakers crossover network because engineers and manufacturers have gotten very sophisticated in that department. It really is better to remove the whole thing. In this day and age power amps and active crossovers are very inexpensive so if its a two way biamp it a three way tri amp and like I have done since 1977 quad amp a four way.

 

[gene_stl]

I think you can truly bi-amp these things:
http://www.infinity-classics.de/technik/manuals/Kappa_9_technical_sheet.pdf

I would want that crossover network gone asap. I would start having one amp channel with the super tweeter, the front and rear tweeter. maybe the MidRange and one straight into the wooofers.

You don't have to worry about "impedance dropping to one ohm " if you get rid of that crossover which by the way , one that complex eats probably 90 % of your power. And causes that complex impedance gyration. That can all be done better (and if you were building it new today with quality components) much more economically with multi amping and DSP. That is an impressive crossover for its day but that sort of thing is MUCH better done with multi amping these days. The impedance gyrations totally disappear when you get rid of all those capacitors and chokes (coils).

I was pleased to see they use 12 gauge wire and have protection fuses.

The woofer channel you can just bypass the internal crossover and do it with dsp/active crossover.
Four Way is better than Three Way which is better than two way (with a sub) which is better than two way which is better than single full range. (I dare you to argue that )

The more of that crossover you bypass the better you will like the sound.

 

[edisonbaggins]

Just a quick update:

1) I'm researching refoaming the 12" woofers, though I've been told it was done. I'll at least check soon. I hear you can accomplish the intent by applying latex to aging foam! I'm skeptical, but we'll see.
2) These were a gift from a friend, not a purchase.
3) I have purchased a very affordable Adcom GFA 5300. Might use it to power the mids/highs and my Crown D 150A to power the 4 x 12" woofers. Will try extended and normal modes.
4) I appreciate the knowledge and passion, but I'm highly unlikely to mess with the wiring of these speakers. Maybe adding a crossover makes sense, but altering the speakers, probably not.

5) Still need a pre-amp. I wonder if the one I use for my full-range 5.1 system can do double duty? Same room at least. I guess is depends on whether it has the available necessary inputs and/or outputs?

 

[edisonbaggins]

The 12"s appear to have been refoamed. Someone was a little sloppy with the glue! Not too terribly bad though.

 

[LuvMyQuad]

Still need a pre-amp. I wonder if the one I use for my full-range 5.1 system can do double duty? Same room at least. I guess is depends on whether it has the available necessary inputs and/or outputs?

Many have zone 2 outputs. I think that would work for what you are doing.

 

[par4ken]

I have been "quad amping" since 1977 and would never go back. This is a golden age for it because there are wonderful dsp systems almost for free that can do so many wonderful tricks besides just being a crossover. (dBx Drive Rack, Behringer DCX series, mine DSP has multiples, all the pro companies have dsp input modules. The pricing of these compared to "audiophool"products is a pittance.)

Also since power amps are pretty tough and long lived there are lots and lots of them available for almost free. As some may remember I sort of missed out on quad "back in the day" (never actually heard it neither in a store nor at anyones house in spite of being an active audio nut. I am sure I would have gotten the bug if I had. So I focused on building the best stereo I could build)

After deciding to get up to speed on things more modern and discovering multi channel and hi rez , I started looking around for power amps. Like @edison baggins I am very VERY cheep. I loathe and detest overpriced gear. In the year or two since I have gotten back into audio, without even trying, and spending what amounts to small change, I have collected a pretty giant stack of power amps. I recommend that you look at Crown professional PA amps. Some of them have dsp inputs that allow you to not have a crossover. There is a guy here in St. Louis that (see ebay "rescueaudio llc") who sells very reasonably and if you are active duty or a vet he will give you a killer deal. He donates a lot of his sales to veteran organizations.

even tho I got a stack of Crowns (from Tim at Rescue Audio) before that happened I found some other Crowns in the Wild for like $40 for a 300 wpc XLS 602
and got a couple of Haflers (great amps but no protection circuitry.) and a Carver pro amp and a Rotel power amp that is a thing of beauty internally.
So many ways to skin the cat. Haven't even mentioned and hardly thought about Class D amps which also are almost free.

I am a bi amping evangelist. I would be very happy to help you quad amp (or however many you want) this system.

I fully agree with you, I've been bi-amping since the late 70's. I now have two quad systems bi-amped. I'm sure that tri-amping or quad-amping would be even better, however there comes a time where the extra complexity makes that impractical. Back in the day I found that a lot of power amps were unreliable and many didn't sound that great, but agree that Crown professional amps are great sounding and almost indestructible, available used at reasonable prices. My rec room system contains most of my original equipment from the 70's, but I'm now using tube amps for the mid-highs (home brew KT-88's push-pull). I'm using mosfet amps from Audio Amateur magazine designed by Erno Borbely for the bass. Both amps sound great on their own and have been very reliable. The other system uses an eight channel Crown amp.