Tubes and Klipsch KG 5.2 loudspeakers

[mmuetst]

Hello all, I'am a new owner of a set Klipsch loudspeakers and I experiance some good and bad with this set.

The loudspeakers are Klipsch KG 5.2. I connect this set of speakers first to my 300B single end tube amp....not bad, but the sound in the high tones was not 100% satisfying.

This is only a 6 a 8 watt tube amp, so I connect my Prima Luna ProLogue Four. This sounded more terrible. Oke it was connected to the 8 ohm tab....let's try the 4 ohm....nop, still  terrible.

I bought this set KG 5.2 second-hand and one woofer was not oké,. So I send the woofer to a repair shop and I was temporarily unable to use the Klipsch. 

When the woofer was repaired and build back into the loudspeaker an audio friend came by and brought a small class D amplifier with him (FX-Audio FX252A). We were prepared for the worst, this must sound even worse. but no, this sounded much better. The high was now pleasant and nice to listen to. I connected my Classic transistor A/B amp no 8.0B  and it is getting even better.

What I now think is that the impediance of this Klipsch loudspeaker is not tube friendly. And when I see other curves of impediance of other Klipsch loudspeakers I think: This will also not be a happy loving couple with tubes....

 

Don't get me wrong...I'am verry happy with my Klipsch KG 5.2 and I use my tube amps on other loudspeakers (V-Vox and Translator).

Do other people share my experiance? 

[DirtyErnie]

KG 5.2 has the Tractrix horn.

Tractrix horn is a 'constant directivity' style, requires a 6dB/Octave rising slope for the horn to make accurate treble response, otherwise it would sound like the high frequencies are rolled off.

Klipsch crossover is probably set up to use the horn's natural high efficiency to provide this rising frequency response, by setting one of the crossover frequency points well above the actual crossover frequency. 

I own a set of CF2's,  the crossover high-pass are set for 2.5 KHz, but the first crossover capacitor is a 1.75uf, setting the crossover frequency at about 15KHz, and rolling off 6dB/octave below that point. This set-up does give a 2.5KHz crossover, but with a 6dB/Octave rising frequency slope up to the high treble, which is what the horn needs.  BUT, this arrangement also causes a very large spike in impedance (up to 20+ ohms) from about 4KHz to about 10KHz, and your tube amplifier does NOT like that.

 

If I was a betting man, that arrangement is where I'd put my money as far as what's causing your issues.

 

 

The solid-state amps are much less bothered by this impedance spike, and therefore sound better.

[mmuetst]

Hello DirtyErnie,

Thanks for the clear explanation. Then I think it is strange that people are looking for tube amps to combine with Klipsch loudspeakers.

If I see the curves of other models Forte or Cornwall, I also see no good match with tubes

I own a seperate listening room and have a collection of equipment. I really like tube amps, but my Magnepans also do not match.

My Translator Reflexion (this is an old dutch brand) are perfect in combination with tube's

http://www.translator-info.nl

 

Sounds really nice with

 

[DirtyErnie]

I'm pretty sure it's possible to re-design the crossover to provide both the rising response and the flat impedance, but the order of the capacitors needs to be reversed, and a series resistor-inductor would have to be added to balance the load properly.  I've not really had time to dig into it, beyond some basic proof-of-concept stuff in a crossover design simulator who's name escapes me right now... XSim?

[mmuetst]

The filter schema in on this website. I will dive into this modification. I just wonder if all these adjustments will also change the sensitivity of the speakers?

 

[mmuetst]

Or if someone has already a tube friendly mod of this filter...Info is welcome

Edited March 6, 2020 by mmuetst

[tube fanatic]

Generally, Klipsch speakers work extremely well with tube amps in my experience.  SETs are usually immune to speaker impedance variations, as are pentode based amps which employ negative feedback.  Can you provide details about your listening situation such as level, type of music you listen to, distance from the speakers when listening, size and characteristics of the room, etc.?  Of course, synergy between amps and speakers is important and it may be a case of those amps not providing the type of sound you enjoy due to their output transformer characteristics or other factors.

 

 

Maynard

[mmuetst]

Hello Maynard, 

Thanks for your comment.

Acoustics are well damped. It is a room wide = 440 cm, length = 600 cm and  height = 320 cm . Listening chair is on 270 cm from the speakers.

wooden ceiling, concrete floor with carpet.

Here a pictue of the setup.

 

The thing is that my Prima Luna that using a ultra linear circuit is sounding worse than my 300B single end without negative feedback. And when I switch to sollid state amp (class D or A/B) the harsh high tones are then gone.  The impedance change DirtyErnie describes kills the quality of the high tones in combination with my tube amps. The bass responce is fine, no complaints. It is pure the high tones that are killing. 

The music I play: lots of jazz, some world music (good recordings like: Será una noche La segunda https://youtu.be/hMgFJOQNme0) and pop (mostly old stuff like Tom Waits 😀 )

Also other speakers doing really great with my tube amps.

Edited March 6, 2020 by mmuetst

[DirtyErnie]

Maynard,

 

I'll agree, triodes do have a pretty wide range of reflected impedance that they can deal with, but a 4x impedance jump through one crossover band or another is definitely not a happy thing for a load line.  Some amps are more tolerant of this than others, and the infinite number of amplifier /speaker combinations out there, every one becomes a rule unto itself. So, really, who knows what the issue is in mmuetst's situation.  But, I know where I'd put my money.  If I wasn't planning to go biamp/active at some point, I'd put more effort into mine.  

 

What a fun hobby, eh?

[mmuetst]

I did get a nice answer back from Danny from GR Research:

 

Hey Michael, 

There is no resistor inline with the tweeter to make the top end have that higher impedance. It is just caused by the actual impedance's of the drivers. 

We can design an impedance trap that will knock out the hump that is at 3.5kHz. That will allow the amp to see a more balanced load. 

You can also try a 47 ohm to 30 ohm resistor across the tweeter terminals to knock the tweeter level down a little bit and bring it's impedance down a little at the same time. 

Thanks,
Danny

 

Danny did some  updates on Klipsch loudspeakers RP-8000F, Forte III and RP-600M. Normal to design an new filter by this man means to ship the speakers to te shop...But I live in the Netherlands and those KG-5.2 are to big to ship 😀

I will try his option with the parallel resistor. Als will i check if I can upgrade the cabinet by making it stronger and damp more.

Edited March 9, 2020 by mmuetst

[MechEngVic]

So is your problem with the sound of the tube amps that the highs are too harsh? Or are the highs too rolled off? Can you measure frequency response? There is a phone app named "Spectroid" that can make simple frequency response diagrams that might help you see the troubled frequencies. You can use youtube to play frequency sweeps. 

[mmuetst]

Hello MechEngVic, thanks for your comment, The highs are too harsh. But only with Tube amps. When I use class D or transistor A/B there is no harsh sound.

My next step is to change the filter:

Good tip about the app, I will try it.

[DirtyErnie]

I like this page:  Capacitors at the Crossover Design Cookbook, cross-referenced with this:  KG x.2 Family which says a 5.2 has a 1,600 Hz crossover point.

There's a graph there that shows impedance -vs- frequency of a given capacitor value.  If we're assuming that's an 8-ohm tweeter, we get these values (assuming the frequency break-point is where the capacitor impedance crosses the 8-ohm line)

 

2.5uf = ~8KHz

8uf   =  ~2.5KHz

 

and the inductor + Resistor here Inductors at the Crossover Design Cookbook:

 

1mH + 4ohms = either 630 hz or ~1,800.  I'm going to choose the lower value.  Either way, the inductor's break-point is below that of either of the capacitors.

 

My thought about doing an impedance trap was to swap the positions of the 8uf and the 2.5uf, and put the trap between the inductor and the second capacitor.  this way, you wouldn't need to add the additional capacitor, and you haven't changed your frequency break-points.  By the inductor chart linked above, you'd be looking at a .15mH inductor and an 8 or 10 ohm resistor to trap down the impedance rise of the 2.5uf cap.  Try that set-up in xsim and see what impedance you get vs. the stock crossover.

[Rick P]

I've used my KG 5.2's with both the McIntosh MC240/MX110 (all tubes) and with the MC2100/MX113 (solid state).  The tube system was part of an estate so had to be sold. Both systems drove the KG 5.2's just fine but I had the opposite complaint when I switched to the solid state system.  The solid state MC2100 exhibited a firmer bass response, which made the 5.2 sound really solid, but overall the sound severely lacked that wonderful "tube" warmth I had with the MC240.  I found the KG 5.2's sounded poor with the solid state equipment vs. the tube equipment and wasn't happy.

 

I learned way way, WAY back in school that tubes add harmonics to sound, which at that time was considered a negative because tubes tend to color the original sound so that it's no longer the original sound.  During that time everything was pushing toward solid state as the superior reproductive sound systems, and I was taught that in school!

 

Well that might be nice on paper but I personally missed that warm sound with the MC2100 and considered selling it.  But I had a thought.  Since I was using a front end mixer (I have 5 input devices) I purchased a simple tube preamp which I placed between the mixer and the MX113.  It was an amazing fairly inexpensive solution.  It returned that tube warmth sound and made the MC2100 sound just like the more valuable tube amp/preamp I had sold!  In fact I no longer miss the tube amp and perfectly happy with the solid state MC2100 and my KG 5.2's.

 

I concluded logically that you really don't need the entire pre-amp/amp to be tubes to get that signature tube sound.  Just a couple tubes on the front end of a solid state system will gave that same warm sound as the tube amp.  The solid state system simply replicates the harmonic's provided by that front end tube.  That was my experience.

 

So my theory on the KG 5.2's is that they seem to respond vastly different, depending on your equipment.