Are Klipsch RF-7 II's THX rated?

[gagelle]

I was looking at the QSC amps. They're inexpensive considering the amount of power they put out.

An interesting thing about vintage amps: All the Sansui amps and receivers that I'm familiar with have warnings that 4 ohm speakers may damage the unit. I have no idea why this is.

[JasonJCarney]

Here's my take on Bose vs THX: Bose is just a single company that aims to build and sell speakers that sound good to a large number of people while being stylish and unobtrusive. THX is a company that sets standards from the recording studio to the movie theater to your house. Because of this, they're in a unique position of being able to credibly claim that what you hear in your home with a full THX certified system is as close as is feasible (obviously the room is still a factor, but even that can be fixed with enough cash) to what the recording engineer heard when he mixed the soundtrack for whatever movie you're listening to. Is this a guarantee that you won't like another set of speakers or amplifier better? No, of course not. But all the same, it's a claim that no one else to my knowledge can match with the same kind of credibility.

I think I can agree with that.[D]

[Don Richard]

THX is a company that sets standards from the recording studio to the movie theater to your house.

If you think that knowing that THX Ultra 2 approved equipment can "fill a room with sound" is helpful to you, then buy such THX approved equipment. BTW, the so called THX Reference Level is 85 dB at the listening position, 12 to 14 feet for THX Ultra 2, with 20 dB headroom. Considering the room gain of a 3000 cu. ft. or so THX Ultra 2 room, a pair of RF-7IIs can do that with about 1/2 watts per channel and slightly less than 50 watts per channel for 20 dB headroom. It is not possible for me to give exact numbers here because there are no acoustic specifications for THX rooms other than room volume and a 50 dB noise floor. That can describe a room with solid concrete on all 6 surfaces, or an anechoic chamber. Here's what folks on another forum had to say about THX home specs, or the lack thereof:

http://www.avsforum.com/avs-vb/showthread.php?t=1048531

It is important to understand that THX specs for home are not a "gold standard of performance" but rather a minimum standard of compatibility.

You would not get that impression by reading the THX website's bombastic description in their home theater section:

"Only the best home theater products have what it takes to be THX certified"

Perhaps a more revealing statement, from the THX websites home theater section:

"Big audio, smaller package"

Seems a lot like Bose advertising, maybe not to you, but to me.

[Zen Traveler]

...Considering the room gain of a 3000 cu. ft. or so THX Ultra 2 room, a pair of RF-7IIs can do that with about 1/2 watts per channel and slightly less than 50 watts per channel for 20 dB headroom.

Aren't you focusing on the wrong thing? Isn't the problem you aren't addressing that the RF-7s have impedance dips that go as low as 2.8 Ohms and most AVRS can't deliver enough current to run RF-7s effeciently?

[StephenM]

BTW, the so called THX Reference Level is 85 dB at the listening position, 12 to 14 feet for THX Ultra 2, with 20 dB headroom.

To clarify, each individual channel must be capable of a 105dB peak, and the LFE channel must be capable of a 115dB peak. For 99.99% of the population, that's really, really loud. Heck, even in an informal poll of the population of this forum, only one solitary person actually claimed to listen to movies at that volume. http://forums.klipsch.com/forums/t/149979.aspx?PageIndex=1

a pair of RF-7IIs can do that with about 1/2 watts per channel and slightly less than 50 watts per channel for 20 dB headroom.

Surely the RF-7 IIs can deliver the volume, but they do not deliver the same frequency response or dispersion characteristics.

It is not possible for me to give exact numbers here because there are no acoustic specifications for THX rooms other than room volume and a 50 dB noise floor. That can describe a room with solid concrete on all 6 surfaces, or an anechoic chamber.

Again, THX will deal with the room if you're so inclined, just as they do in the professional line. Realistically however, the vast majority of people have neither the inclination nor the cash to address the issue, at least via THX certification.

You would not get that impression by reading the THX website's bombastic description in their home theater section:

Is there a business in the world that would advertise itself as anything other than the best at what they do?

[Don Richard]

...Considering the room gain of a 3000 cu. ft. or so THX Ultra 2 room, a pair of RF-7IIs can do that with about 1/2 watts per channel and slightly less than 50 watts per channel for 20 dB headroom.

Aren't you focusing on the wrong thing? Isn't the problem you aren't addressing that the RF-7s have impedance dips that go as low as 2.8 Ohms and most AVRS can't deliver enough current to run RF-7s effeciently?

That's why you need to listen to the equipment before you buy it. Besides adequate power capabilities you should audition equipment to see how it sounds. Powering a speaker adequately does not begin to define how it sounds to you. THX certification does not do that.

[Don Richard]

Aren't you focusing on the wrong thing? Isn't the problem you aren't addressing that the RF-7s have impedance dips that go as low as 2.8 Ohms and most AVRS can't deliver enough current to run RF-7s effeciently?

How do you know that they don't have enough current to run those speakers without listening to that specific combination? Worst case the RF-7s will have 3 dB less peak output due to output current limiting. Those speakers are quite efficient and will play as loudly as another speaker rated as 8 ohms with 98 dB sensitivity, and louder than any speaker less sensitive than that. Depending on the subwoofer crossover point you may not be operating the RF-7 where the impedance falls that low. These are all real world considerations not addressed by THX certifications, which is why you need to listen to any electronics-speaker combination to see how it sounds to you.

[Don Richard]

You would not get that impression by reading the THX website's bombastic description in their home theater section:

Is there a business in the world that would advertise itself as anything other than the best at what they do?

THX is definitely out to make money and they are definitely targeting the lifestyle crowd. Why, don't you know they even have THX approved ring tones available? Ring tones, really? Next thing you know they will be selling auto, home and life insurance, all THX approved, of course.[8-)]

[StephenM]

THX is definitely out to make money

I'm shocked, just shocked!

they are definitely targeting the lifestyle crowd.

Them and everyone else with the slightest interest in watching/reproducing movies.

Why, don't you know they even have THX approved ring tones available? Ring tones, really?

Capitalism at its finest, what can you say.

[Zen Traveler]

Aren't you focusing on the wrong thing? Isn't the problem you aren't addressing that the RF-7s have impedance dips that go as low as 2.8 Ohms and most AVRS can't deliver enough current to run RF-7s effeciently?

...Worst case the RF-7s will have 3 dB less peak output due to output current limiting. Those speakers are quite efficient and will play as loudly as another speaker rated as 8 ohms with 98 dB sensitivity, ...

What you are reporting about RF-7s being easy to drive has been refuted by RF-7 owners owners since the originals were introduced....When you say "Those speakers are quite efficient and will play as loudly as another speaker rated as 8 ohms with 98 dB sensitivity," negates the fact that it actually is rated at 101 dB and is "8 Ohm Compatible." You are acting like they are the same kind of "8 Ohm speaker," as the Klipschorn when in fact their Frequency Response chart is considerably different given their design differences.

Just to make sure I am not missing something, are you saying that any AVR should be able to drive an RF-7 based home theater and that it should be able to hit THX Reference levels (or even 10 dB lower) with ease without damaging the speakers or the AVR?

EDIT: Btw, THX speakers can't dip below 3.2 Ohms in any frequency and that is a requirement that Speaker MFGs have to meet along with the privy information to be certified.

[Don Richard]

What you are reporting about RF-7s being easy to drive has been refuted by RF-7 owners owners since the originals were introduced....When you say "Those speakers are quite efficient and will play as loudly as another speaker rated as 8 ohms with 98 dB sensitivity," negates the fact that it actually is rated at 101 dB and is "8 Ohm Compatible." You are acting like they are the same kind of "8 Ohm speaker," as the Klipschorn when in fact their Frequency Response chart is considerably different given their design differences.

No, I am not saying they are 8 ohm speakers nor am I comparing them or anything else to a Khorn. What I am trying to make you understand is that if any current limited amplifier can deliver 3 amperes into an 8 ohm load it will also deliver that amount of current into a load of 3 ohms. Power =current squared X load impedance. For an 8 ohm load that is 72 watts, for a 3 ohm load that is 27 watts. That is approximately a 3 dB difference. Therefore a loudspeaker that is 3 dB more sensitive will play as loudly as the less sensitive unit. Even if it was 3 dB lower in output it would be hard to hear a difference as that is the point where most folks can hear a difference in volume on a wideband signal. Remember, this is on peaks, not average SPL. As far as some AVR recievers not being able to meet their advertised power output, that is quite common and there are test reports available from periodicals and on the internet that would identify those units. Or you could just, as I have said several times in this thread, listen to the combination that you want to buy and see if it works for you.

Does THX, Inc. publish test reports on equipment that they recommend or do they suggest compatible matches based on a minimal standard?

[StephenM]

For an 8 ohm load that is 72 watts, for a 3 ohm load that is 27 watts. That is approximately a 3 dB difference. Therefore a loudspeaker that is 3 dB <em>more sensitive</em> will play as loudly as the less sensitive unit. Even if it<em> was</em> 3 dB lower in output it would be hard to hear a difference as that is the point where most folks can hear a difference in volume on a wideband signal.

Couple thoughts to add in there Don:
1. By my reckoing, it is a 4.3dB difference.
2. This difference will not be across the the spectrum, but at the specific frequencies where the impedance does dip.
3. If you turn up the volume knob past the point where the amplifier can adequately supply clean current at those few frequencies, one of a few things happens: distortion will rise considerably at those frequencies, the sound will become unbalanced, or the amplifier will go into protection. A listening test should be able to inform a user if this will be a problem; however, it isn't a guarantee that the material used for the audition will stress the specific frequencies either, and a user may get home, pop in a flick, and wonder why the heck his shiny new receiver is a POS.

Does THX, Inc. publish test reports on equipment that they recommend or do they suggest compatible matches based on a minimal standard?

They don't publish test reports on each piece of equipment, but a THX Ultra 2 amplifier must be stable down to 3.2 ohms on all channels, and swing peaks of up to 18 amperes on all channels. There are also proprietary requirements for things like crosstalk, output impedance, hum, etc to ensure that performance is of good fidelity. As far as matching with speakers go, THX Ultra 2 speakers and amplifiers are designed to complement one another. Obviously, the benefit of this arrangement is that the speaker manufacturers and amplifier manufacturers are working towards a common goal with a single entity providing the specifications for how the two components will interact. As far as I'm concerned, its a much better arrangement than manufacturers designing speakers without any regard for what amplifier may be used, and vice versa on the amplifier side.

[Zen Traveler]

No, I am not saying they are 8 ohm speakers nor am I comparing them or anything else to a Khorn. .... As far as some AVR recievers not being able to meet their advertised power output, that is quite common and there are test reports available from periodicals and on the internet that would identify those units. Or you could just, as I have said several times in this thread, listen to the combination that you want to buy and see if it works for you.

Does THX, Inc. publish test reports on equipment that they recommend or do they suggest compatible matches based on a minimal standard?

Okay, Don....You've lost me outside of we both agree that it's good for one to go and listen to what they are considering buying....Insofar as your last line is concerned, the difference in the THX standards that matters IN THIS THREAD as it pertains to RF-7s is that THX Ultra II AVRs are certified to drive speakers with dip down to 3.2 Ohms with all channels being driven (to Reference Level in a 3,000 cu ft room) whereas most AVRs cannot (that would make it NOT a minimum standard for AVR Mfgs)....The specs you are referring to weren't available on previous Yamaha and Denon models, however since Denon has chosen not to send their latest models in for THX testing they are actually listing on their site which AVRS can drive low impedance speakers and it appears you have to get to their mid-level 43xx series upper mid-level before you do....

That being said and getting back to your original example of "8 Ohm speakers and 98 db Sensitivity rating," I still contend people using those numbers and thinking the RF-7s would be easier to drive would start out as cheaply as possible and spend countless hours working their way up to an Expensive AVR or a Moderate Level AVR with an external amp and be curious why they needed so much horse power to drive such an efficient Home Theater...

Or they could read the countless threads in this and other forums and find out that they need a beefier power supply to drive RF-7s (Regardless of what one would surmise looking at the on-line specs)) and in an AVR, those are only going to come from upper-end units and/or if they have an THX Ultra II label it's been certified to do so (or the mfg put in writing that it will do so). With that information THEN I would go out and audition speakers and see if my research was fruitful.

[Zen Traveler]

2. This difference will not be across the the spectrum, but at the specific frequencies where the impedance does dip.
3. If you turn up the volume knob past the point where the amplifier can adequately supply clean current at those few frequencies, one of a few things happens: distortion will rise considerably at those frequencies, the sound will become unbalanced, or the amplifier will go into protection. A listening test should be able to inform a user if this will be a problem; however, it isn't a guarantee that the material used for the audition will stress the specific frequencies either, and a user may get home, pop in a flick, and wonder why the heck his shiny new receiver is a POS.

....but a THX Ultra 2 amplifier must be stable down to 3.2 ohms on all channels, and swing peaks of up to 18 amperes on all channels.

2 and 3 apply to the RF-7 and using Don's analogy they wouldn't be able to understand why their speaker isn't as easy to drive as Klipsch specs indicate and then they would spend hours researching and hopefully coming up with the scientific answer as they audition....Wait. That was me. [H]

[jacksonbart]

I have a pair of THX rated undies, they handle low ohms.

[Don Richard]

They don't publish test reports on each piece of equipment, but a THX Ultra 2 amplifier must be stable down to 3.2 ohms on all channels, and swing peaks of up to 18 amperes on all channels. There are also proprietary requirements for things like crosstalk, output impedance, hum, etc to ensure that performance is of good fidelity.

Do you have any links as to where those specs are listed?

[StephenM]

The bulk of what I know about THX comes from this article: http://www.hometheaterhifi.com/technical-articles/165-what-it-means-and-how-to-use-it.html