Minimum wattage for the RF 7 II's or III's ?

[Dean HTD]

I was recently provided a set of 1999 RF 3's that were  "terribly" discarded due to a house flood.  Drivers were damaged but still work and i fell in love with these speakers.  The lower level room is quite large though, so i am interested in purchasing either of the RF 7's.  My concern is my amplifier's capacity.  It is a HTD DMA1240 that provides 40 w/ch,  or 120 w/ch (bridged).

 

Would this amplifier be capable of delivering the req'd wattage these speakers deserve for the quality of sound they are capable of?  If so,  is the 40w or 120w the preferred wattage to drive them at?

[Pete H]

Welcome Dean!  From my personal experience with RF7's, they can be driven with a smaller watt amplifier, although, you will notice improvements when they are driven with higher wattage SS amps.  Unless you have 2 of those amps, running it bridged will only drive one.  I have, for testing purposes, put the 7's on very modest receivers with 50-60 watt ratings and they sounded good, but mine are currently driven with amps that are 200+ per channel and I've had amps on them that were 350+ WPC, they just sound better with bigger amps.

[Emile]

Welcome again   Believe the RF-7's are rated at 250W.  Don't have any, but just got CF-3's which specs are pretty similar. Initially had them on a Marantz 1060 (30+wpc) and they sounded very good.  Just gave them a little more juice (Kenwood M2, 220wpc) ... nice improvement  

[garyrc]

Welcome to the forum!

 

How big a room (in cu. feet)?

 

How far away do you sit?

 

Will the RF 7 IIIs be near a wall or a corner so they will get boundary gain?

 

Do you use a sub?

 

How loud do you like it?  85 dB is medium level, but classical and other orchestral music can easily produce very brief peaks of 105 dB.  Rock is "all loud."  Paul W. Klipsch said that to get the blood stirring level of a full symphony orchestra, you need very, very brief peaks of 115 dB at your ears (he later characterized 115 dB continuous as "too damn loud!."   It will produce ear damage, if presented for a few minutes.  My Klipschorns (which are a little more efficient/sensitive than RF7 IIIs) need 88 watts to produce 115 dB if it were continuous, in my big room.   Since very brief peaks usually won't produce clipping I could probably get away with 44 watts.  I give 'em 150 watts "RMS," just in case.  According to Klipsch, the RF7 IIIs are 5 dB less efficient than the Klipschorns.  So, if we can validly make these conversions, for RF7 IIIs to produce, at my listening distance (13 feet), in my room ( ~~4,300 cu.ft.) 115 dB continuous (which you don't want to do) you would need almost 300 watts.  Since good amps can tolerate it, you might get away with 150 watts for the very, very, brief and somewhat rare 115 dB peaks.

 

As you may know, a difference of 3 dB requires double or half of the wattage, depending on whether you are going up or down.

 

See also, this calculator: https://myhometheater.homestead.com/splcalculator.html

 

[robert_kc]

Dean HTD:  Welcome!

I own RF-7II, and in my average size room, a 30 wpc push/pull tube amp works great for classical music at sane listening levels.

 
Here’s a quick summary of my thoughts – off the top of my head - regarding the need for amplifier power:

 

1. Speaker sensitivity is specified on a logarithmic scale, as garyrc explained.  RF-7II (and RF-7III) are fairly sensitive (101dB), meaning they require relatively little power to produce satisfying volume levels.  To put this in perspective, some owners of highly sensitive speakers (e.g., Klipschorn, 105dB) are satisfied with a 2 wpc tube amp.   The RF-7III require at least double that power - and possibly much more power - depending on the following considerations … 
    
2. Speaker/amp synergy.  This is black magic, as far as I’m concerned.  IMO, you basically have to audition amps and speakers together to hear if they “play well together”.   (Others can offer some technical explanations.)
    
3. Tubes vs. solid-state.   Analogies are dangerous, but in a sense, this is like the difference between a diesel vs. gas engine when pulling a heavy load.   Tube watts “go farther” than solid-state watts.
    
4. Room size.  If you double the length, width, and height, the room has 8 times the volume, meaning much more acoustic power is needed to fill the room.
    
5. Distance from listening chair to speakers.  Sound level is inversely proportional to the square of the distance – i.e., if you sit far away, you need more power.
    
6. Listening volume.  Some people listen at volume levels that causes hearing damage.  Again, logarithmic – meaning if you want insane volume level, it takes a lot of power.  FWIW, I don’t recommend that people damage their hearing, or be inconsiderate of neighbors.   (If you want “ear bleed” volume levels, then I suggest you read about Klipch’s products designed for commercial application (e.g., speakers designed for a movie theater or auditorium).  Some people install these in their home.  Hopefully their neighbors are miles away.)
    
7. Genre of music.   Large scale orchestral music can have tremendous dynamic range (e.g., Mahler Symphony 2), and powerful bass (e.g., bass drum, double bass, pipe organ), and therefore can place a relatively large demand on an amp and speakers.   Folk music – and most pop music - not so much – because it’s all the same volume level.
    
8. Mastering of a recording.   Modern hi-res recordings of classical music typically are not compressed.  OTOH, a lot of pop music is highly compressed, resulting in less dynamic range and less demand on an amp and speakers.  (In other words, you can listen at a lower volume level and hear everything, because there are no soft passages.  And there are no fff loud passages that require power reserves.)
    
9. Technology of the consumer deliverable.   Modern hi-res consumer deliverables like Blu-ray, 24bit/192kHz download, and SACD are capable of tremendous dynamic range.  OTOH, some consumer formats (e.g., LP) are capable of less dynamic range, and therefore place less demand on an amp and speakers.  
    
10. Whether or not a subwoofer cross-over is installed before the amp, thereby off-loading power-hungry bass from the main amp and speakers.  (I use my Oppo UDP-205’s bass management feature, and line-level subwoofer connection.)
     
11. Surround sound 5.1 vs. stereo.   If you have 3 identical speakers (LCR) across the front, plus rear speakers, and subwoofer, you’ll have more acoustic power than 2 speakers.   

 

In my basement system (average size room), I have no problems with dynamics or deep bass, for any music.   Front, center, and left speakers are Klipsch RF-7 II.  A single rear speaker is a Klipsch RF-7.   Subwoofers:  SVS SB16-Ultra, Klipsch R-115SW.  Source:  Oppo UDP-205 universal player, playing hi-res recordings of large-scale classical music.  (The Oppo provides the bass management function, meaning that the power-hungry bass is off-loaded from the main amp and speakers.)   I have multiple tube amps in this system.   If I use, for example, a Scott 296 to drive the left and right channels, and a Fisher KX-200 (or Scott 272) to drive the center and (single) rear channel, there is dynamic range and frequency range approaching symphony hall experience.   (These tube amps each produce approximately 30 - 40 wpc.  If I want real muscle, I’ll use my Scott LK150 which produces about 58 wpc.)   No problems with dynamics, or deep bass, for any genre of music.  For big-band music or folk, my 8 wpc single ended-amp is satisfying.

 

Bottom line, the answer to the question “how much power is needed” is “it depends”.  That’s my 2 cents.  Hope it helps.   
 

[glens]

4 hours ago, robert_kc said:

That’s my 2 cents.

 

That was more like a buck and a half.  There were a couple points I disagree with, but not enough to actually do it.  There's enough info there to arrive at a determination in this case.  If not, the question wasn't genuine.

[GuyIsDamGood]

What is the max input watts - (8-ohm stereo) the RF7-IIIs can handle? (before distortion)

[grendel23]

I owned RF-7IIIs. I had them on an amp that would deliver 600wpc at 8 ohms.

They didn't audibly distort even when the clip lights were blinking. My ears couldn't take more than a few seconds of that and the speakers wouldn't survive long either, but it was very impressive.

If you listen to music without much bass at normal volume, these would be happy with 50wpc, but why get these speakers unless you can feed them properly? I would invest in a good 200wpc amp.

[the real Duke Spinner]

37 minutes ago, grendel23 said:

I owned RF-7IIIs. I had them on an amp that would deliver 600wpc at 8 ohms.

They didn't audibly distort even when the clip lights were blinking. My ears couldn't take more than a few seconds of that and the speakers wouldn't survive long either, but it was very impressive.

If you listen to music without much bass at normal volume, these would be happy with 50wpc, but why get these speakers unless you can feed them properly? I would invest in a good 200wpc amp.

Thank you. 🙂

[GuyIsDamGood]

(thanks for the info/input)

 

I plan on purchasing the Yamaha PX8 (8-ohm - stereo - 800-watt amplifier).   But; now I believe that'll be too much power for the RF-7iiis (even though I don't plan on putting any bass on them - I let the two 15"-inch subwoofers handle the bass).

 

I agree.   They play Clear and Loud (with my current stereo 200-watt amp).   I would like to get more volume from them. . .if any.

Edited February 8, 2023 by GuyIsDamGood

[GuyIsDamGood]

I know someone out here had or currently have the RF-7iiis and (put-in) / put's-in near 800 watts - (8 ohms) - stereo. . .Safely?     Is there anyone?

 

Thank you

[MicroMara]

strange , my RF7 EvoTec need only 3 to 5 watts amplifier power

[Zen Traveler]

37 minutes ago, MicroMara said:

strange , my RF7 EvoTec need only 3 to 5 watts amplifier power

Does that mean it's more about the current delivered than thinking in terms of watt-per-channel? Fwiw, I'm a multichannel music/home theater guy and feel the impedance dips in the RF-7s was what one should consider (along with max volume) when matching a power source. That's my 2 cents.

[MicroMara]

8 minutes ago, Zen Traveler said:

Does that mean it's more about the current delivered than thinking in terms of watt-per-channel? Fwiw, I'm a multichannel music/home theater guy and feel the impedance dips in the RF-7s was what one should consider (along with max volume) when matching a power source. That's my 2 cents.

When my RF7 EvoTec was still a series RF 7 MK II, they also needed more power to reproduce a powerful sound image despite the characteristic of a sensivity from 101 dB, since they´re working with a high quality modified X-Over design , 3 to 5 watt power is enough for me to be able to reproduce a powerful soundstage . A level of 55 dB is already sufficient for this  ......ym2c 😉

[GuyIsDamGood]

. . .(thanks for everyone's input)

 

The RF-7iii speakers (with original Klipsch crossover) have a RMS of 250-watts - and can handle up to 1,000-watts peak.

Will any wattage of power in the middle 250 - 1,000-watts somewhat damage the speaker(s)?

 

(Has anyone gave these speakers some Safe-Mean watts?)

 

Thank you

Edited February 11, 2023 by GuyIsDamGood

[wuzzzer]

You’ll go deaf in short order if you’re putting anywhere near that through them.

[MicroMara]

Power handling can be measured in different ways. In Europe, loudspeaker manufacturers are now obliged to determine the power handling in standardized tests (ISO IEC standards). The following three power handling values are decisive:

 

Nominal power handling: the loudspeaker is tested for a duration of 100 hours.

Continuous load capacity (long term): The loudspeaker is loaded for 1 minute with 10 repetitions. The pauses between the load phases are 2 minutes.

Impulse load capacity (short term): The speaker is loaded for 1 second each time it is repeated 60 times. The pauses between the load phases are 60 seconds.

 

The power of the amplifier and the load capacity of the loudspeaker must be matched. The relationship of the two components can be compared to the relationship between tires and the maximum speed of a car: Tires should always be designed for the maximum speed of a car, otherwise they can be damaged. If, on the other hand, they are designed for a much higher speed than the car can reach, you are leaving a lot of potential behind. This is not really sensible either.

 

So, analogous to tires, when it comes to watts and speakers, you should make sure that the latter can handle the power of the amplifier. Otherwise, in the worst case, the speakers can be damaged by overload - so-called clipping. Conversely, it is of little use if speakers that can be subjected to high loads cannot achieve their full sound potential, i.e. their actual "musical performance", due to an amplifier that is too weak.

 

If you gonna use a an amps with max. 250 Watt per Channel 8 Ohm will be more than enough. At a sensitivity from the RF7 III with 100 dB, one quickly reaches the threshold of discomfort, this begins at 110 dB sound pressure, the pain threshold begins at 130 dB soundpressure. I think you don´t want to destroy your hearing ability

 

[henry4841]

So many misconception of power needs of real efficient horn speakers. The truth is most never use more than a couple of watts period with our speakers. One question, if a $25K Japanese SET 300B amplifier with 5 to 7 watts is not good enough for our speakers just what in the world could they be good for. 

5 Watts with tube, slightly more quality watts with SS is what one truly needs. An amp that sounds great at millwatts not watts is a major concern as well. 

[the real Duke Spinner]

I measure +/-  500 watts on an instantaneous level. If  the amp don't have that. 😳

Well...

 

[MicroMara]

3 hours ago, henry4841 said:

So many misconception of power needs of real efficient horn speakers. The truth is most never use more than a couple of watts period with our speakers. One question, if a $25K Japanese SET 300B amplifier with 5 to 7 watts is not good enough for our speakers just what in the world could they be good for. 

5 Watts with tube, slightly more quality watts with SS is what one truly needs. An amp that sounds great at millwatts not watts is a major concern as well. 

That´s what I mentioned in my earlier posts above as well .. 3 > 5 Watt will be enough