Klipsch Forte IV ... what amp ?

No , I am not asking for a particular amp style and brand here . Although I am not refusing any suggestions either !

What I would like to know first is what characteristics to look for in an amp to drive these speakers (Forte 4’s) to full performance .

Such characteristics as :

1.) What is needed to handle the low impedance of 4 ohms ?

2.) While the sensitivity is listed at 99 dbs. it is considered to be closer to @ 96 dbs,

3.) What about negative feedback ?

4.) Will the 12" woofer and 15 " rear radiator need special attention also ?

5.) Do the horns require special consideration ?

I feel that these considerations will go further to getting it right than , " hey , just get a tube amp and enjoy " .

Thank you & Be Safe .


Just about any amp will work with those. However it would help if we knew how big your room is and how loud do you want to play. And when you say amp do you mean a separate power amp using a preamp to drive it?

If an integrated amp serves your needs I’m really hot on the Rogue Sphinx right now. 100wpc should get the job done in most cases and it’s a sweet sounding amp. It is way better sounding than it’s price suggests.

I run a PrimaLuna Dialog Premium with my Heresys, works very well.

Hi All,

I bought a pair of Forte IV's about two weeks ago.

My system is PS Audio Memory player, EVO B4B DAC, Don Sachs DS2 and CJ 17LS2 preamps.

My other speakers are Thiel CS5i's so I have a McCormack DNA-500 on hand.

The Forte's were very harsh with the DNA-500. Really don't really know why, but not a good match.

I inserted my CJ LP66S, which is 60 wpc into 8 ohms. Much better sounding, most of the harshness is gone. And 60 watts could blow me out of my listening room (16 x 35 with speakers at one long end, listening spot about ten feet away, so half the room is behind me).

I have been reading everything I can find about the Forte's and amps. Lots of people seem happy with less than 100 wpc - tube and ss.

My opinion is that they would sound great with the right 30 wpc or less. Maybe Pass, First Watt, etc.

Read somewhere that horns do not like amps with a lot of negative feedback so you have to be careful with ss. Not a problem with tube amps, I believe. I am no expert.

I am finding the speakers hard to place in my room. The bass seems a bit tighter  and more nuances with the speakers about 14 to 20 inches from the front wall. Closer might give a bigger bass but it is not as refined to my ears.

They Fortes seem to be need volume to get a wide soundstage. Nothing I have tried provides a good depth of soundstage. Still playing with the toe in. 

Like the livliness and dynamics. 


Saki70, share your journey as you try different amps.







Hello and thanks for the response .

Actually the Forte's were for another system with a Primaluna Dialogue Premium !

But the Boss Lady wanted them in this streaming system that I am putting together. 

This system is running a Naim Unity Atom which is an integrated amp/streamer/DAC with a pre -out . Using the pre-out , we wanted to try something else for amplification .

We have about 400 sq. ft.in an 'L' shaped room with the listening position about 

10 ft. away . We listen from soft , just above a wisper , to loud , yelling across the street . I believe that the output impedance of the Naim pre-out to be 24 ohms .

Be Safe 


Actually the Forte's were for another system with a Primaluna Dialogue Premium

So, how does it sound?

If you mean the present setup ... it is quite good . We could easily live with it .

But... I don't think that I am allowed into this hobby without trying something

else . Always looking for something better , you know !

I am trying to keep our audio prejudices out of this discussion so as not to

taint the desired answers .

Thank you

I don't think that I am allowed into this hobby without trying something


The grass isn't always greener across the street. 

Saki70, I had two Prima Luna preamps - a Prologue and then traded up to the Dialogue Premium.

Ended up deciding that they were just not lively enough in my system with the Thiels and sold the Dialogue.

The interesting thing is that I was in an audio store listening to Dali speakers and a solid state amp about a month ago and I asked to hear the speakers with a Prima Luna EVO 300 or 400.

I was amazed at how similar the amp sounded to my old Dialogue preamp. For me, PL gives me the spit on the microphone but not the sizzle as as the spit hits the mike. My ears and my gear - YMMV.

My only point is that you owe it to yourself to listen to as many amps/preamps as you can. Different brands do not sound alike.I am fortunate to live in the Indianapolis area and there is a high end dealer that puts up with me and has let me audition used gear in my home. Hopefully, you can find a place like that where you are.

Thanks for listening,



The main thing that is worrying us is the low impedance and what requirements

a tube amp would need to handle it .

Thank you 

For me, PL gives me the spit on the microphone but not the sizzle as as the spit hits the mike.

Try some Gold Lyon KT88s. 

I've used Prima Luna Dialogue Four, custom built 300B SET monoblocks and Coincident 845 SET amp with my Klipschorns which has impedance drop to around 3 ohm at 100hz, sensitivity is higher at 104db. I've also  auditioned Music Fidelity M2SI and Denafrips Hyperion amps, both class a/b solid state.


All have handled the impedance drop just fine. I do prefer tubes with Klipschorns, and expect all Heritage line better with tubes. As for sound quality, my favorite amp with the Klipschorns is the 300B's, sweetest sound which compliments Klipsch inherent qualities best. The one issue I could see in running 300B amps is handling your impedance curve, my 300B's monoblocks each have power supply equivalent to what one would normally see in stereo 300B, so no issues for me. 845SET should be no problem, and the push pulls fine as well.

I'm using a pair of Quicksilver Mid Monos to drive my Forte IV and they sound fantastic.   40 watts PP ,  they are EL34 based but can use any EL34 / 6l6 variant 

They have a 4 ohm tap but I drive them off the 8 Ohm tap and they don't break a sweat.   I will soon be replacing the Quicksilvers with a 8 watt 300b amp,  the Forte are so to easy to drive 

Oddiofyl ;

That is an amp that I have been considering , except for the biasing thing .

I am not able to do that . I have been wondering about the Horn mono's

which are auto biasing but only 25 amps .

It's always something !

Thanks for the info .

Be Safe

That is an amp that I have been considering , except for the biasing thing . I am not able to do that .

Learning to bias an amp (at least in this case) is VERY easy. You just need a cheap multi meter and a small screw driver. I'm no electrical genius by a long shot but if you can turn on a multimeter you can bias this tube amp. 

@russ69 For me, PL gives me the spit on the microphone but not the sizzle as as the spit hits the mike. Try some Gold Lyon KT88s.

Interesting thought. I am running Penta KT88's with the CH LP66S amp

I have two preamps, a Don Sachs DS2 and a CJ 17LS2. When I run the DS2, I get a horn treble at high volumes that is hard on the hearing; but the ultimate amount of aliveness is there. When I run the CJ 17LS2, I tame that treble edge at high volume but lose the last bit of liveness.

Not sure what I need to do. The Forte's provide some great dynamics, slam, and soundstage at higher volumes; the treble edge is killing me.

Wondering if some Quicksilver monos is the answer or maybe Pass/Fest Watt..

Thanks for listening,


Actually the Mid Monos don't even need a meter .  To bias you just turn each tubes bias pot fully counter clockwise . Old Mid Monos have one potentiometer per amp to bias and for those matched tube pairs for each amp are recommended.  The newest version has a bias pot for each tube which is better.   

So with all pots counter-clockwise, turn the amps on and let warm up for a few minutes

I recommend doing one amp at a time.   

After it has been on for a few minutes, press the bias test button, there are two for new units.   Press and hold the button as you slowly turn the pot clockwise.....slowly.  the LED will start to glow.  Just when it starts to glow, back off a little until it goes out.   Let the amp warm up for 15 , checking the single or both LEDs if so equipped to make sure it doesnt glow bright RED.  If it does back off counter clockwise a little.  

After the amp has been on for at least 15 or 20 min check bias and adj clockwise until the LED just starts to glow red.  REMEMBER TO PRESS THE LED CHECK BUTTON AND HOLD WHILE ADJUSTING.....

The goal is not to bias them hot for a long life.   If the LED barely glows the amp is in the correct range.  

I don’t have Forte’s but I have Heresy’s and Quartet’s. I run a Vincent sv500 but I assume most hybrids would yield similar results. Even my wife stops and comments when I use this setup. It is very smooth and takes the edge off the horns but does not reduce the live feel impact of the speakers. 

Oddiofyl ;

Can you compare your horn mono's to any other amps on the forte's ?

Primaluna and Quicksilver have caught our eye's .

OOps . now those prejudices . that I spoke of  . are out of the bag !

Be Safe ,

I've only had the Forte a little over a year.  The QS are really the only amps I've used except for a short period where I used an Acurus A150.   It sounded good with the Acurus but the QS were much better .   I had a bad tube,  thats really the only reason I hooked it up short term.

Rogue Atlas and a Mac240 here with my Heresy IV's. Love them both. What I'm gunning for now is bringing a Rogers into the mix


try a rogue stereo 100!  dont know how but it blows away the atlas, a much much more powerful amp with bigger bass despite the same 100 WPC. 

I've just recently sold a set of Forte lV's and replaced them with Cornwall lV's. The Forte's require a lot more effort with placement, because of the 15" passive radiator and different room treatment arrangement.

As far as amplification, I'm using a First Watt SIT-3 combined with a Supratek Sauvignon which is a 6sn7 preamp. I think this combination is wonderful and has more than enough power/current for me. In the future I plan to buy a Coincident 300b tube amp to go along with the Coincident Statement pre I have now and experience that flavor. 

I am also using a 10 ohm 5 watt resistor on the speaker terminals, like Nelson has suggested.

For me, this combination has overcome the "Horn Shout" people commonly associate with Klipsch speakers. (I also have GIK room treatment)

Besides experimenting with Speaker isolation/Bars/Brass spikes/Iso-acoustics in the future, I plan to put Dynamat on both Horns... on the suggestion of Mr. Decibel and Don Sachs. (Boston Audiophile Video)


Forgot to add that Coincident has a new 300B amp coming out in June. From my understanding it is a single box design, not a dual mono like the Frankensteins.



funny you should mention, I have been thinking exactly that. Or saving and going for a pair of Rogue monoblocks 

I've tried several amps on my Cornwall IVs including the McIntosh MC275 VI, my friend's Rogue Stereo 100 with Dark upgrades and BoyuuRange A50 MKIII 300B, and my own Audio By Van Alstine 600R hybrid amp. 600R bested all of them until I tried my Enleum 23R.  I've had my 23R since mid December and I couldn't be happier with it driving my CWIV.

If I could use one word to describe the sound of the 23R it would be organic.  It's tubelike character is also very transparent, fast and dynamic without ever being fatiguing.  It's only 25 watts/ch and it's a world class headphone amp as well mating with my Susvara, Abyss 1266TC, Focal Utopia and ZMF Verite open.  Enleum is a new company formed by the former head of Bakoon International.  The amp has only been out for about 4 months but it's already been reviewed by 6 Moons, Darko on Youtube, Jason Kennedy and several others.  All the reviews have been very positive and in summary, they say the 23R is a fantastic amp for easy to drive sensitive speakers.  My CWIVs are rated at 102dB and they easily drive them with excellent dynamics and transparency.

Adding to my post above, I use the 23R as a power amp with my Van Alstine FET Valve CF vacuum tube preamp. The 23R can be used as an integrated amp without a preamp but I prefer the sound with my preamp. The rest of my system includes a REL S5 subwoofer, Rega P10/Apheta 3 turntable, Luxman EQ500 vacuum tube phono stage, Aurender W20SE streamer/server, Holo May KTE DAC, PS Audio PST SACD transport and Equi=Tech 2RQ power conditioner.

Hi All,

I posted this earlier in the thread: "...The Forte's were very harsh with the DNA-500. Really don't really know why, but not a good match...".

To set the record staright:

I reinserted the DNA-500 amp with my Forte's and was suprised. They do not sound at all like what would lead me to post the ealier comment.

Sound staging, dynamics, and a "like live" sound are all present now. And the hiss is pretty much gone.

Don't know if it is my hearing getting used tio the speakers or the speakers are breaking in...

Anyway, the DNA-500 sounds good,

I just purchased a pair of Forte 4’s a week ago, and the listening session I had with them was fantastic. I am driving them with a Music Reference RM 200 tube amp, coming from a Rotel 1590MK 2 preamp. (My other speakers are JBL L100 Classics) 

running Hegel H95 at the moment with Bluesound streamer

the amp was recommended by more than one Klipsch dealer that does not carry Hegel

seems to be a very good match




coachpoconnor wrote:  "I am also using a 10 ohm 5 watt resistor on the speaker terminals, like Nelson has suggested."


Coach, is the suggestion about the resistor Pass recommends particular to the Sit 3 or is it something I should look into for my two First Watt F3s I use with my triamplified DIY horn speakers?

Hi All,

Been runing a First Watt F7 for about three weeks now with my Forte iv's. Paired with a Don Sachs DS2 preamp, PS Audio Memory Transport, and Mojo B4B DAC.

To my ears, listening at low 70 dbl ten feet from speakers: seems like more detail and tonal texture with F7 compared to CJ LP66S or McCormack DNA 500 amps. Sounstage seems wider, can exceeed the outside of speakers if it's on the cd. Dynamic and has taken the too hot edge off the Klipsch treble.

My opinion: The Forte iv"s are good speakers if you pair them wth good equipment.

Thanks for listening,