Any point in running Kappa 9s with a Purifi 400 stereo amp?

[tmtomh]

I've unexpectedly got the opportunity to have a pair of good-condition Infinity Kappa 9s at no cost (except that of moving them to my location).

They were being run with an Adcom GFA-5800, but I have exactly zero desire to replace my current Purifi amp with a 60-pound space heater (and one that will almost certainly emit mechanical hum in my location because of DC on the AC line). I had a GFA-5400 for years and I liked it but was glad to replace it with the lower-noise Purifi and don't want to go back.

I'm impressed by the Kappa's soundstage height and the sheer ability of those 4x 12" woofers to move air. But I've never been into gigantic, room-dominating speakers - and more importantly, I'm leery of their bananas impedance curve.

I don't listen at terribly loud volume at home - typically 75-85dB. But with the Purifi I'd be running the Kappas at about 60% of the power of the Adcom GFA-5800. The Purifi is able to pump out about 90% of the Adcom's power at 1%THD, but at 1% THD the Purifi is already clipping (unlike the Adcom, which is spec'd to run at 1.8% THD), so that's not really sustainable. And I haven't really paid much attention to what a Purifi-based amp might do when presented with the very low-impedance load the Kappa 9 presents at certain frequencies.

So... should I:

1. Get a 2nd, identical Purifi amp and bi-amp the Kappas?

OR

2. Try replacing the Purifi with a Hypex NCx amp that has more power?

OR

3. Return to my plan before this opportunity arose, which was to get a pair of Genelec 8351s? I could sell the Kappas and my Purifi amp and put that money towards the Genelecs.

Comparing the cost, I'd estimate that transporting the Kappas and buying a 2nd Purifi amp could run me roughly $2k. On the other hand, if I sold the Kappas and my Purifi amp and put those funds towards the Genelecs, my net cost for the Genelecs would be something in the neighborhood of $4k-$4500. That's a significant difference, but not a deal-breaker difference when considering what I plan to be my forever setup.

I'm not a big bass-head and I don't listen at very loud volume as noted above. I have a decent-sized listening space (about 270 sq ft) and listen about 2.5M from the speakers.

@Doodski , I know you have a lot of experience with the Kappas - do you have a thought about this? Anyone else?

Thanks!

 

[Blumlein 88]

60% power is only about 2.26 db in loudness. I'd think what you have is going to be fine especially as you say you don't listen very loud.

As to whether Genelec 8351s are a better idea, only you can decide.

If the cost is low as you say, get the Kappa's , use them for a time. If you like them keep them. Owning something like the Kappa's is a good experience. If not investigate (hear) some 8351s.

PS-the Kappa 9's are big, but they seem even bigger in person. They aren't really that deep, but something about them makes them seem larger.

http://www.infinity-classics.de/technik/manuals/Kappa_9_technical_sheet.pdf

Some nice pictures.

Infinity Kappa 9, Top of the Line, Incredible Full-Range Classics - SOLD

Infinity was hitting its stride in the 1980s with a wide range of products from modest, yet impactful bookshelf speakers, to insane design innovations spawned from their EMIT/EMIM tweeter and midrange designs. These high-efficiency flat panel transducers provided amazing transparency in the...

holthill.com

 

[tmtomh]

60% power is only about 2.26 db in loudness. I'd think what you have is going to be fine especially as you say you don't listen very loud.

As to whether Genelec 8351s are a better idea, only you can decide.

If the cost is low as you say, get the Kappa's , use them for a time. If you like them keep them. Owning something like the Kappa's is a good experience. If not investigate (hear) some 8351s.

PS-the Kappa 9's are big, but they seem even bigger in person. They aren't really that deep, but something about them makes them seem larger.

http://www.infinity-classics.de/technik/manuals/Kappa_9_technical_sheet.pdf

Some nice pictures.

Infinity Kappa 9, Top of the Line, Incredible Full-Range Classics - SOLD

Infinity was hitting its stride in the 1980s with a wide range of products from modest, yet impactful bookshelf speakers, to insane design innovations spawned from their EMIT/EMIM tweeter and midrange designs. These high-efficiency flat panel transducers provided amazing transparency in the...

holthill.com

Thanks so much! My power-related concern isn’t about volume so much as whether the Purifi would take one look at the 1ohm load the Kappas apparently present around 30Hz and 10kHz and promptly shut down or blow up.

But if what you’re saying is that my Purifi amp will basically perform like the Adcom (which has happily driven the Kappas at moderate volume for about 25 years), except at 2.25dB lower max volume, that would indeed be fine given my usual listening volume level.

And yes, I’ve seen and heard these Kappas in person. They’re pretty graceful looking, but a 5-foot tall, nearly 2-foot wide speaker is enormous no matter how you slice it.

I’m particularly intrigued because they’ve been well cared for: the woofer surrounds have been professionally replaced, and the notorious disintegrating dome midranges have also been replaced. So they’re in tip-top shape. As long as I can run them safely with my Purifi amp, I am inclined to give them a try in my space.

 

[Deleted member 48726]

The emit tweeters are delicate even with loud and clean power they can be at risk so you do not want to clip those.

I would be hesitant to connect Kappas to an amplifier with unknown(?) behaviour out of it's comfort zone. I also believe the 9's have an "extended" switch on the back which pulls the impedance further down.

 

[voodooless]

Why would you need massive amounts of power with such an efficient speaker?

 

[Doodski]

I've unexpectedly got the opportunity to have a pair of good-condition Infinity Kappa 9s at no cost (except that of moving them to my location).

They were being run with an Adcom GFA-5800, but I have exactly zero desire to replace my current Purifi amp with a 60-pound space heater (and one that will almost certainly emit mechanical hum in my location because of DC on the AC line). I had a GFA-5400 for years and I liked it but was glad to replace it with the lower-noise Purifi and don't want to go back.

I'm impressed by the Kappa's soundstage height and the sheer ability of those 4x 12" woofers to move air. But I've never been into gigantic, room-dominating speakers - and more importantly, I'm leery of their bananas impedance curve.

I don't listen at terribly loud volume at home - typically 70-85dB. But with the Purifi I'd be running the Kappas at about 60% of the power of the Adcom GFA-5800. The Purifi is able to pump out about 90% of the Adcom's power at 1%THD, but at 1% THD the Purifi is already clipping (unlike the Adcom, which is spec'd to run at 1.8% THD), so that's not really sustainable. And I haven't really paid much attention to what a Purifi-based amp might do when presented with the very low-impedance load the Kappa 9 presents at certain frequencies.

So... should I:

1. Get a 2nd, identical Purifi amp and bi-amp the Kappas?

OR

2. Try replacing the Purifi with a Hypex NCx amp that has more power?

OR

3. Return to my plan before this opportunity arose, which was to get a pair of Genelec 8351s? I could sell the Kappas and my Purifi amp and put that money towards the Genelecs.

Comparing the cost, I'd estimate that transporting the Kappas and buying a 2nd Purifi amp could run me roughly $2k. On the other hand, if I sold the Kappas and my Purifi amp and put those funds towards the Genelecs, my net cost for the Genelecs would be something in the neighborhood of $4k-$4500. That's a significant difference, but not a deal-breaker difference when considering what I plan to be my forever setup.

I'm not a big bass-head and I don't listen at very loud volume - typically 75-85dB. I have a decent-sized listening space (about 270 sq ft) and listen about 2.5M from the speakers.

@Doodski , I know you have a lot of experience with the Kappas - do you have a thought about this? Anyone else?

Thanks!

I ran the Kappa 9s with these amps and had no issues. I'm a tone control adjuster and I pump the bass and treble and the amps handled themselves well. The Kappa 9 are a very intriguing speaker and they seem to be a love them or dislike them sort due to size and power requirements. I'm in the love them camp because they are so versatile with different music genres, they go pretty loud, have the thump that satisfies me with excellent top end. For free I would invest in shipping them and keep them or use them to fund your dream system. I think for a functioning set of Kappa 9s with non-rotted driver surrounds they will be snapped up immediately when a person that is in the market comes along. Go for it!
Luxman M-03

Luxman M-03 Stereo Power Amplifier Manual | HiFi Engine

www.hifiengine.com

Luxman M-02

Luxman M-02 Duo-Beta/S Power Amplifier Manual | HiFi Engine

www.hifiengine.com

Yamaha M-85

Yamaha M-85 Stereo Power Amplifier Manual | HiFi Engine

www.hifiengine.com

Yamaha AX-900

Yamaha AX-900 Natural Sound Stereo Integrated Amplifier Manual | HiFi Engine

www.hifiengine.com

 

[tmtomh]

I ran the Kappa 9s with these amps and had no issues. I'm a tone control adjuster and I pump the bass and treble and the amps handled themselves well. The Kappa 9 are a very intriguing speaker and they seem to be a love them or dislike them sort due to size and power requirements. I'm in the love them camp because they are so versatile with different music genres, they go pretty loud, have the thump that satisfies me with excellent top end. For free I would invest in shipping them and keep them or use them to fund your dream system. I think for a functioning set of Kappa 9s with non-rotted driver surrounds they will be snapped up immediately when a person that is in the market comes along. Go for it!
Luxman M-03

Luxman M-03 Stereo Power Amplifier Manual | HiFi Engine

www.hifiengine.com

Luxman M-02

Luxman M-02 Duo-Beta/S Power Amplifier Manual | HiFi Engine

www.hifiengine.com

Yamaha M-85

Yamaha M-85 Stereo Power Amplifier Manual | HiFi Engine

www.hifiengine.com

Yamaha AX-900

Yamaha AX-900 Natural Sound Stereo Integrated Amplifier Manual | HiFi Engine

www.hifiengine.com

Thanks - this is so helpful! Two quick responses to your comment:

1. I read some of your earlier posts about the Kappa 9s where you mentioned running them with the higher power Yamaha and Luxman amps, but now, knowing that you also ran them with the lower power, 130-140wpc Yamaha and Luxman units, makes me feel much more secure, as the real-world 8-ohm power of my Purifi amp is more in-line with those.

2. As noted in my response above, yes, the dome midranges disintegrated and were replaced about 5 years ago; and the woofer surrounds were also re-done several years ago, I believe by Infinity. So these are definitely in good shape and I agree with you that they would be easy to sell if need be.

Oh, and I should also mention that the Kappas' current installation, with the Adcom GFA-5800 running them, has the listening position ridiculously far from the speakers, like 4 meters, and there's still more than enough volume to be had. I listen about a meter closer in my space, which should help offset some of that volume difference from having less power in the amp. Of course, there's also the matter of gain, but I can probably figure that out too.

Thanks again!

 

[Blumlein 88]

Well I don't know about shutting down. You could always buy some 10 watt 1 ohm ceramic power resistors. Parallel a couple for each channel, and connect in series with the speaker. Should prevent amp shut down. Would alter damping a bit.

The ones I heard were powered by the Yamaha M85 in Doodski's post. I also have one of those that belongs to my brother. They are good amps.

 

[Deleted member 48726]

Thanks - this is so helpful! Two quick responses to your comment:

1. I read some of your earlier posts about the Kappa 9s where you mentioned running them with the higher power Yamaha and Luxman amps, but now, knowing that you also ran them with the lower power, 130-140wpc Yamaha and Luxman units, makes me feel much more secure, as the real-world 8-ohm power of my Purifi amp is more in-line with those.

2. As noted in my response above, yes, the dome midranges disintegrated and were replaced about 5 years ago; and the woofer surrounds were also re-done several years ago, I believe by Infinity. So these are definitely in good shape and I agree with you that they would be easy to sell if need be.

Thanks again!

You need not only look at the watts but at the amplifiers behaviour at low impedances (are they rated at low Z) and that they are capable of sustaining high current.

 

[tmtomh]

You need not only look at the watts but at the amplifiers behaviour at low impedances (are they rated at low Z) and that they are capable of sustaining high current.

Thanks - that was really what my initial question was about.

 

[restorer-john]

Emits (tweeters) are a lot tougher than you'd think. But the super tweeters (Semits), I have no experience with. How fragile they are- who knows. How are they protected in the Kappa 9s? In the RSMs etc, it was just a 1-1/4A fast blow fuse. I've seen RSMs with alfoil wrapped around dead fuses and tweeters were still fine...

I honestly wouldn't be concerned with using the Purifi (single) into the Kappa 9s if you are sensible with volumes.

And the decreased residual noise in the Purifi might well be a major audible benefit too.

Excellent score!

 

[restorer-john]

The biggest issue IME with Infinity loudspeakers is not driver failures at all, but the connections to the drivers failing. They used spade terminals which were tin plated copper and the tin turns to wispy spider webs, makes poor contact and many audiophiles think they have dead tweeters or drivers. As most of the ranges were sealed designs, the atmosphere inside the cabinet was comprised of gassed off particle/mdf adhesives, glues and fibreglass wadding binders- some pretty toxic chit I reckon. Some of the reactions with the terminals and connectors have to be seen to be believed after ~40 years.

Cutting off the spade terminals and directly soldering all the internal cabling to the speaker drivers is a very good measure.

 

[Deleted member 48726]

Emits (tweeters) are a lot tougher than you'd think. But the super tweeters (Semits), I have no experience with. How fragile they are- who knows. How are they protected in the Kappa 9s? In the RSMs etc, it was just a 1-1/4A fast blow fuse. I've seen RSMs with alfoil wrapped around dead fuses and tweeters were still fine...

I honestly wouldn't be concerned with using the Purifi (single) into the Kappa 9s if you are sensible with volumes.

And the decreased residual noise in the Purifi might well be a major audible benefit too.

Excellent score!

The real question is; could you be sensible with volume with Kappa 9's ?

I couldn't. Hence I have a' plenty of power on tap.

 

[Deleted member 48726]

The biggest issue IME with Infinity loudspeakers is not driver failures at all, but the connections to the drivers failing. They used spade terminals which were tin plated copper and the tin turns to wispy spider webs, makes poor contact and many audiophiles think they have dead tweeters or drivers. As most of the ranges were sealed designs, the atmosphere inside the cabinet was comprised of gassed off particle/mdf adhesives, glues and fibreglass wadding binders- some pretty toxic chit I reckon. Some of the reactions with the terminals and connectors have to be seen to be believed after ~40 years.

Cutting off the spade terminals and directly soldering all the internal cabling to the speaker drivers is a very good measure.

Exactly! I thought one of my emits have died on me a while back but it was the connection on the driver that had come loose. I just gave it a gentle squeeze with a sidecutter. I should solder them, now I come to think of it.

 

[Doodski]

wispy spider webs

Those are danger zone things. Tin whiskers are a subject NASA has taken up.

 

[Doodski]

The real question is; could you be sensible with volume with Kappa 9's ?

I couldn't. Hence I have a' plenty of power on tap.

The Kappa 9s bass gets addictive combined with that snappy top end. I always cranked them up and loved every second of it. We had the B&W 801 Matrix in the same room and I preferred the Kappa 9s. I did what I did with the Kappa 9s and I damaged the voice coil former on the 801 woofer. Covered under warranty.

 

[Mnyb]

There is a purifi module for lower impedance speakers 1ET7040SA

 

[Deleted member 48726]

Those are danger zone things. Tin whiskers are a subject NASA has taken up.

I've only ever seen that phenomenon on old stuff in sheds..

 

[tmtomh]

Emits (tweeters) are a lot tougher than you'd think. But the super tweeters (Semits), I have no experience with. How fragile they are- who knows. How are they protected in the Kappa 9s? In the RSMs etc, it was just a 1-1/4A fast blow fuse. I've seen RSMs with alfoil wrapped around dead fuses and tweeters were still fine...

I honestly wouldn't be concerned with using the Purifi (single) into the Kappa 9s if you are sensible with volumes.

And the decreased residual noise in the Purifi might well be a major audible benefit too.

Excellent score!

Thanks John - much appreciated. Despite the allure of the Kappa 9’s bass, I actually have no problem with being sensible with volume. I can’t really tolerate anything over about 90dB for more than a few minutes, so 85-88dB is my “loud” listening volume for any extended period, no matter how seductive the thump.

 

[Doodski]

I've only ever seen that phenomenon on old stuff in sheds..

I have had really weird issues when attempting to repair gear. I would get to the point where I would whip out the isopropyl alcohol or methyl hydrate, thoroughly/lightly scrub the PCB with a toothbrush and voila they worked after. Whiskers could have been be the issue.