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RF 82's just don't deliver enough bass :(


Bleeding

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It seems to me that a good 100 watt RMS per channel (all channels operating) receiver or power amplifier would be enough.

No offence, but I have practically experimented it. My RF-82 II sound fantastic on movies and better than before on stereo by moving the surrounds to an outboard amp, I still feel RF-82 II are underpowered. Even with 3 channels driven, Yamaha RX-V3900 is not pumping out more than maximum 120 watts per channel. Which means, these speakers are NOT efficient at all but, at the same time, they really are fantastic speakers for movies, at least. Both Yamaha and Klipsch specs are misleading on their own. Having said all that, I reckon adding a 170-200 wpc external amp like NAD, Emotiva, Rotel, etc and people here will be surprised how tremendous these speakers are.

My advice to everybody on the forum is that no matter which gear you spend your hard-earned money on, DO NOT go on the advertised specs. God knows which environment the manufacturers test their speakers in, but the real end-user's rooms are anything and everything but ideal. All those specs jump out of the window when a speaker has to go into a carpeted bedroom, with a bed, drapes, a dressing table, a couch, and a 6'x4' alley (btw that's the description of MY ROOM). So, all those specs in real world do not hold.

Overall ..... Yamaha RX-V3900 is fantastic but with only 80 watts speakers set if all channels are driven. 140 wpc on its specs sheet is extremely over-stated.

Klipsch RF-82 II are NOT efficient, but with 170-200 wpc external amp they are mind blowing and nothing less than extra ordinary coz they draw more current which RX-V3900, sorry to say, cannot offer with 5 channels driven, although it is a 7 channel AVR. I am only running 3 channels :(

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Klipsch specs are misleading on their own....God knows which environment the manufacturers test their speakers in

To the best of my knowledge, Klipsch tests sensitivity in their anechoic chamber and adds 4dB for room gain. From the third party measurements I've seen of some of their speakers, including several in the RF line, they seem to be reasonably accurate.

Klipsch RF-82 II are NOT efficient

Heh if you think they're not efficient, I'd hate to hear what you think of the bookshelves I've got in my bedroom. Per Audyssey and my SPL meter, they need about a 15dB boost relative to my RF-5s. That's inefficient.

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I think the midrange reflects this efficiency, but the woofers seem to need to be played rather loudly to "get going."

The woofers are likely to be as sensitive, but not necessarily as efficient as the horn tweeter. IOW, with 2.83 volts, they probably do approach the rated sensitivity, but they are also likely drawing much more than 1 watt to do so. How much more of course depends on the impedance curve.

Oh, now I get it. Thanks[:)]

How should this poster (or others) calculate how powerful an amp is needed? That is, above what power would more powerful amps begin to give diminishing returns? Is this the same as the maximum wattage drawn at the "worst" impedance for that speaker, and should it be specified at PWK's proverbial "115 dB at your ears for the blood stirring peaks of a symphony orchestra" at listening distance in a real room, rather than at a lower figure, like than the usual 90 - ~~ 105 dB at a measly meter? IOW, I'm saying let's ignore the handy fiqures for comparing speakers to one another (e.g., dB @ 1M, at 1 watt, OR at 2.83 volts, which I now know can produce different results), and use some other method to see how much power is really needed for a specific speaker in the real world, given one's listening habits.

Do you know how I would determine how much power my Klipschorns (with an AK4 upgrade) would need at the least favorable part of the impedance curve, for, say, 115 dB in a 3,000 cu. ft. room? I know that an old figure Klipsch came up with was 63 watts, no section of the impedance curve specified, so I guess it was at some kind of average impedance.

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Hi Gary,

Power will of course depend on the speakers (sensitivity, impedance), distance, and of course volume requirements. Starting with the speaker, you'll find that the rated voltage sensitivity is typically rated as XdB w/ 2.83 volts at 1 meter. Enter impedance. At 8 ohms, 2.83 volts equates to 1 watt and 0.3534 amperes; at 4 ohms, 2.83 volts equates to 2 watts and 0.7067 amperes; at 2 ohms, 2.83 volts equates to 4 watts and 1.413 amperes. So while a speaker could be rated at 98dB w/ 2.83 volts @ 1 meter, it could be demanding as little as half a watt (16 ohms) to more than 4 watts (2 ohms) depending on impedance. If you were to rate by 1 watt, the 8 ohm speaker would be 98dB sensitive with 1 watt, whereas the 2 ohm speaker would be 92dB sensitive with 1 watt.

Staying with a speaker for the moment, you'll notice that the current demand doubles when the impedance halves. This is not the case if you simply double power into the same impedance: 2 watts into 8 ohms calls for 0.5 amperes; 2 watts into 4 ohms as noted above calls for 0.7 amperes. Hopefully this helps to explain why lower impedance loads are so demanding.

Moving on to distance, going from 1 to 2 meters reduces output by 6dB; going from 2 meters to 4 meters subtracts another 6dB. This corresponds to 4x the power for each doubling of distance. Even moving from 9 feet to 12 feet is a difference of 2.5dB, which is nearly doubles your power requirements.

Finally there is the matter of volume/listener preference. Me, I don't have a use for 115dB peaks. I don't even really have a use for 105dB peaks. When watching movies, my volume doesn't exceed -20dB from reference, which equates to peak levels of 85dB from the satellite channels. I don't listen to music any louder either as verified with an SPL meter.

So for me, the numbers in question are: 99dB sensitivity (96dB to be conservative), 8 foot distance, impedance of 4 ohms (per Klipsch support), and 95dB of volume (just to give myself some margin for error/headroom). Under those conditions, worst case, I need ~9.4 watts per channel from my mains into a 4 ohm load. For my rears the numbers are: 90dB sensitive (87dB to be conservative), 6 foot distance, and an impedance again of 4 ohms (conservative guess). Again, worst case, this calls for 42 watts per channel from the rears into 4 ohms. So all 4 channels driven, and assuming a worst case of 4 ohms, I need ~103 watts total, comfortably within the limits of my receiver.

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This is not the case if you simply double power into the same impedance: 2 watts into 8 ohms calls for 0.5 amperes; 2 watts into 4 ohms as noted above calls for 0.7 amperes.

I don't seem to understand this part[:o]

In any case, loud passages in our room range from about 85 dB (f ) to an occasional 105 dB (fff ), so we probably do require 115 dB peaks. The rare fff levels occur in selections like Fanfare for the Common Man (timpani and tam-tam), The Great Gate of Kiev, and the last part of The Firebird in the exemplary recording of Fantasia 2000.



So looking at a Klipschorn, proceeding on a wattage only basis, would this be
a correct calculation of needed amplifier power at the lowest impedance
(which, I think, is about 4 Ohms, at least on Klipschorns older than mine)?




  1. Starting at 1 watt at 8 Ohms (2.83 volts) at 1 meter = 105 dB including
    estimated room gain of 4 dB (reputedly measures 101 dB in anechoic
    chamber, with 4 dB added for average predicted room gain, producing a
    room figure of 105 dB)

  2. We increase to 2 watts because the impedance falls to 4 Ohms somewhere in the curve
  3. The need increases to 32 watts due to moving back from 1 meter to 4 meters (two doublings, or 12 dB --see note below*).
  4. Those 32 watts are giving us about 105 dB at the listening position 4 meters back
  5. 64 watts would give us 108 dB

  6. 128 watts would give us 111 dB
    SPL




We have now
very nearly reached the rated power of my power amps (150 watts), so it
looks like I won't be getting those 115 dB peaks.


.... but I
suspect it is not as bad as all that, because isn't it true that the 6
dB decline for every doubling of distance falls to 50% when in a room,
as opposed to outside or in an
anechoic chamber? I think PWK measured a 9-10 db decline in moving a
microphone from 2 feet in front of a speaker to 16 feet, rather than the
18 dB to be expected outside. That's somewhere in The Dope from Hope,
perhaps in the article on direct/reflecting speakers (such as Bose 901)
in which he was trying to establish that one hears a good deal of
reflected sound with speakers of nearly any design.


.... So .... If we remove
the 4 dB estimate of room gain in step # 1 (to avoid counting room gain
twice) but change the 12 dB loss in step # 3 to a 6 dB loss, we get a
net gain of 2 dB, which would give us a maximum level of 113 dB. I'm
guessing all these figures are continuous power needed, with
instantaneous peaks power about 3 dB more.


The trouble with all this is that given the Klipschorn's unusually high efficiency, very few speaker/amp combinations would be able produce PWK's figure of 115 dB except for very brief peaks indeed.

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I don't seem to understand this partSurprise

Just how the relationships work out between power, voltage, impedance, and current. Power = Voltage * Current. Voltage=Current * Impedance. Power = Impedance*(Current^2). So if you've got 2 watts at 4 ohms, you're looking at 2=4*(X^2) or 0.5=X^2, or roughly 0.7 for current. If you've got 2 watts at 8 ohms, you're looking at 2=8*(X^2) or 0.25=X^2 or 0.5 for current.

So looking at a Klipschorn, proceeding on a wattage only basis, would this be a correct calculation of needed amplifier power at the lowest impedance (which, I think, is about 4 Ohms, at least on Klipschorns older than mine)?

Yes, although one would expect that your amplifiers do have additional headroom for momentary peaks (NAD especially being particularly well known for this), so even 115dB may well be attainable if that is your goal (presuming the speakers are physically capable of those output levels). Even my mid-line receiver can technically swing a peak of 12.5 amperes (part of the THX Select 2 spec) into a 4 ohm load, equating to 625 watts. If I didn't want to be conservative with my figures, and just ran with a 99dB w/ 2.83V input @ 1m sensitivity for my RF-5s, I could say that adjusting for 4 ohms down to 96dB w/ 1 watt, I could theoretically reach 116.2dB at the listening position. Of course, I'd expect my RF-5s do not have that kind of output capability either, but it's not something I plan to worry about.

.... but I suspect it is not as bad as all that, because isn't it true that the 6 dB decline for every doubling of distance falls to 50% when in a room,

as opposed to outside or in an anechoic chamber?

6dB is definitely a theoretical figure for a full space environment (anechoic), and real world should see less of a decline. However, I'd expect the actual magnitude of the decline would be fairly dependent upon the room.
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... even 115dB may well be attainable if that is your goal (presuming the speakers are physically capable of those output levels)

They are supposedly capable of 120 dB for an instant ... and about 114 dB for a slightly longer period of time. I wouldn't want to try music with a large amount of high treble content at this level, beause the tweeters are more delicate. Since most orchestral music (the kind I usually listen to) has the overtones at something like 20 dB below much of the rest of the spectrum (during the loudest passages), a 115 dB brief peak on the part of the orchestra as a whole would amount to about 95 dB out of the tweeters, which would require less than 1 watt at if the listener was sitting at 1 meter, but perhaps almost 4 watts at my actual listening position. That would be pushing it for many tweeters, including mine, so I won't push it. That being said, we are told that most tweeter failures are not because of well delivered clean peaks in the music, but due to amplifier clipping, a result of using an amplifier that is not powerful enough.

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That being said, we are told that most tweeter failures are not because of well delivered clean peaks in the music, but due to amplifier clipping, a result of using an amplifier that is not powerful enough.

A bit of light reading on that topic:

http://billfitzmaurice.info/forum/viewtopic.php?t=1886

Wow, I'm beginning to doubt anything I hear in an audio or home theater showroom, or in an audio magazine, for that matter.[:)]

I thought that clipping destroyed tweeters because the squareish wave produced not only much to much SPL within normal bandwidth, but also zapped the tweeter with ultra high frequency, high SPL, sound well above its range (like 30K or 40K???) I heard a set of square waves at the Mills College electronic music center, and they were very raspy and had tons of high frequency content (yet their tweeters survived). During a studio tour in the '70s, an engineer said they always turn down the volume when rewinding or fast fowarding tape, because of a similar abuse of tweeter voice coils, etc. imposed by the high frequency content octaves above normal (this, even though the tape is held away from the heads on ff or rew). Is this untrue, also?[:^)]

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During a studio tour in the '70s, an engineer said they always turn down the volume when rewinding or fast fowarding tape, because of a similar abuse of tweeter voice coils, etc. imposed by the high frequency content octaves above normal (this, even though the tape is held away from the heads on ff or rew). Is this untrue, also?

Can't claim to know anything about that, but the same rules apply in the end.

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  • 4 weeks later...

Hi Bleeding,

Since you have somewhat the same setup as I do, I feel pushed to help u. My late response was due the fact that I was in two minds whether to replace the reciever or add an external amp (NAD 275BEE) to the current setup. So, finally i went the cheaper way. I somehow managed to dispose off Yamaha RX-V3900 at a good price, added a lil more money, and got Onkyo TX-NR809.

Performance Review

AUDIO: Fantastic......rxv-3900 does not have enough on-demand current especially when the impedence drops. Onyko blows yammy outa the water in terms of power with 5 channels driven though rated at 135 wpc, which is less than yammy (140 wpc). Mind you, I was only running 3 channels on yammy and surrounds were outsourced to external amp. With Onkyo, I am running full 5.1 setup without external amp. Stereo + Movies, both are FANTASTIC. Channel seperation and listener encapsulation also are nothing less than tremendous. In my earlier post I was cursing Klipsch RF-82 II for not being detailed, I take it back. Yammy was the culprit. Klipsch rocks.

VIDEO: Awsome.....video chipset on onkyo is far superior to the same on yammy. Just set the upscaling to 1080p and enjoy tons better video quality of onkyo.

Overall: I was a big fan of yamaha for quite some time and this is my first Onkyo. Onkyo all the way it is. Yammies are extremely misleading on their specs. Although onkyo is only a tad over yammy in terms of weight, but it shows onkyo has a heavier power supply meaning thereby HIGH CURRENT. You don't need an external amp in 5.1 setup, at least. And trust me I am not a guy to settle for anything less, when it comes to attention to detail. Also, this onkyo x09 series recievers run fairly cool and do not get hot. My advice to you is to do away with yammy and go for onkyo. But i also reckon you audition onkyo before pulling the trigger. As far as I am concerned, I am extremely happy with Onkyo and now feel the bass in my gutts both in movies and stereo listening. One more thing.....AUDYSSEY is far superior to YPAO.

I hope it helps.....

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