Does the RF-7 defy physics??

[TBrennan]

That's the key phrase Doc, less sensitive.

Used that Sonic Impact yet?

[jacksonbart]

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On 7/29/2005 12:41:59 AM TBrennan wrote:

That's the key phrase Doc, less sensitive.

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So Klipsch is lying on their claim of 102db @ 2.83 volts/1 meter sensivity? I am not technical, so perhaps a moderater can chime in here and defend the claim, that the RF7s are actually less/more or equal to the sensitivity stated in the specifications. Interesting discussion so far, but someone must be wrong and I would be interested in whom is correct. Are you saying that the sensitivity ratings for the heritage series determined on a whole set of different criteria that is perhaps more accrurate?

[djk]

"why are those sensitivities so low?"

That's the way it is.

"Surely you're going to get closer to 100dB of output with 2.83V. I just can't see klipsch overrating by 10 dB, so what gives?"

BS on somebody's part.

"I have a feeling that you're talking about "mechanical efficiency" or at least that's the term I use for it...dunno what the proper term is if there is one that describes output versus cone excursion."

The Cornwall figures in at 101dB/2.83V using the same equations. Nothing wrong with the math.

"The way I see it, the RF-7 has overkill motors which give more cone excursion per watt, so though not improving the mechanical nature of the system (thus not reducing distortion or anything like that) the system is still 102dB efficient because it will put out that much SPL for 2.83V"

While they may have high midband efficiency, low Qts drivers have no bass. Look at the JBL tech note, fig.5

http://www.lansingheritage.org/images/jbl/reference/notes/tech1-3a/page07.jpg

10 cu ft box, below 100hz they are all about the same. At 300hz or so they are 103, 98, and 93dB. The 93dB 2235 will have the greatest bass output because of the large x-max (6dB more that the 2225, 12dB more than the 2220).

3% FMD sounds vey bad; congested and compressed sounding on complex passages, female vocals sound like they are either gargling or singing through a fan. 3% is produced by only 5mm cone excursion with 35hz and 350hz mixed 1:1 (PWK).

The Heresy has 3% at 90dB, the Cornwall 3% at 100dB, the Klipschorn 1% at 10dB (about 3% at 110dB).

[Dylanl]

My RF7s used to clip my Marantz MM9000 5 channel amp on movies with large explosions at moderate listening levels. The Marantz was 150 watts x 5 channels, there should be no way a 102 sensitivity speaker should do this.

[Petrol]

EEK!

Wow, when all this dumping on the RF-7's gets out, I should be able to pick up a nice pair on ebay for cheap . . .

Note to all unhappy owners of 'mint' Black RF-7's: I got $500 that I'll trade you for your 'mint' pair . . . today!

[MrMcGoo]

It is no big deal that the RF-7s fall off like a rock below 50 Hz. The RF-7s fall off by 20 decibels from 50 Hz to 30 Hz per Home Theater Mag's tests.

The RF-7s are designed to be run with an RSW-15 with a 650 watt amp on the 15 inch driver. Why? Because they are intended to be used as a home theater speaker that will always have a subwoofer available. If they are run in this manner, there are none of the problems being discussed. And you still have the smaller size than Heritage speakers like the Cornwall.

Most of the distortion goes away when you run the RF-7s as small. Yet there are folks on this board that do not believe in running the RF-7s as they were designed to be used. They claim that it is a "waste" of the RF-7s bass. May be they like the distortion ot have lost their hearing or are expressing views on gear that they have never listened to.

Bill

[Dylanl]

I was running my RF7s with a SVS PCI+ 20-39 sub with a huge amp. To fess up this only happened when I ran the speakers on larger or sent the bass signal to both main and sub.

Still, making the clipping lights come on?

You want a great HT speaker try thr KSP 400. None of those problems. I think you do give up a little on the music side though.

[MrMcGoo]

Explosions played loudly on speakers set as large will clip most amps in my experience. The 30+ db peak requires 1,000 times the power for a brief time.

I get lots of flack for running an amp that will not clip explosions. "It's overkill and should not be needed on such sensitive speakers" they say.

It is simple math, but many folks do not bother to look due to the "sensitivity." They do not realize that Klipsch put the 650 watt amp in the RSW-15 because it is needed. They had originally planned a 1,000 watt amp, but used a 650 watter at the last minute.

Bill

[jacksonbart]

I run my RF7s with the RSW15 and a treated room and no complaints. I have a Denon and never any clipping in 2 channel with out the sub (its warm w/ a good source, but w/ out the punch) or 7 channels with the sub (btw the constraint on power w/ all channels driven is usually the plug/fuse, not the amp if the receiver any good). I set the crossover at 60hz and can easily hit 100 dbs peaks in music with ease, never measured peaks in movies (too dark). But I will tell you this, my wife (who is one tuff SOB) has only every cried, jumped out of her seat grabbed my hand, etc, watching movies in our basement system. I have neighbors who have leaved scary movies cause they can't handle it. There are some I can't watch alone. HDTV is always presenting IMAX movies (when will they learn, a six story picture and great sound will still suck with a piece of sh!t script.) and frankly sitting thought 3d Sharks on the Navy Pier IMAX Theater in Chicago, the sound was below par, however the sound I heard in Charlie and the Chocolate Factory was good.

Can't wait for a Klipsch to sign in on proof, I frankly think most of the stink is from a bunch of lonely old men who have too much time on there hands, but if they are right and the RF7s cant hit the posted stats, I will bow down and kiss their feet.

[sunnysal]

I think it would be safe to bow down now since DJK is not wrong. why is it so hard to believe that klipsch overstates numbers, or states numbers based on marketing needs? everyone is tempted to do that and since klipsch built its rep on high efficiency speakers (the highest in the market at the time) it is not surprising they do whatever they can to keep the numbers attractive. regards, tony

[MrMcGoo]

DJK's numbers are as bullet proof as Hoffman's Iron Law. In any case, it is best to let the subwoofer do what it does best, low bass.

There is no doubt that a Khorn, properly set up has better bass than my RF-7s. The other side of the situation is that the RF-7s are more flexible in placement, take up less space and easily keep up in a home theater.

The only caveat on the RF-7s is that they need an amp that will drive the 2.8 ohm minimum impedance. The Khorn is much easier to drive in terms of impedance.

With good amplification, the bass output of the RF-7s is prodigious. The fact that they are challenged to actually hit 32 Hz -3 db is no biggie IMO.

Bill

[Duke Spinner]

why buy a $ 1700 speaker ....

that needs a subwoofer ..???

[cjgeraci]

Heh, heh, heh....somehow, I knew someone would go there.

I've had RF-7s running in the same room as other Heritage speakers - and off of the same preamp - and I agree with Tony.

Carl.

[Erukian]

I know this might sound stupid, but could the fact that the RF7's go so low vs the heritage series and maintain it's efficiency be advancements in driver technology like bigger excursion without losing control before it hits the xover. Also the fact that the RF7 is ported and some heritage was not.

I could be wrong though.. I don't believe anything in the speaker business defy's physics, it's just a matter of understanding it.

-Joe

[Hardhead]

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On 7/31/2005 9:47:28 AM Erukian wrote:

I don't believe anything in the speaker business defy's physics, it's just a matter of understanding it.

-Joe

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Nothing in the speaker business defies physics? You haven't been listening to the marketing people, then, and that's what we're really talking about.

[DrWho]

But the fact of the matter is the RF-7 does go deep and sounds good doing it...and at least seems to be consistent with its posted specs, so who cares what the marketing department says, or what the tech department says for that matter...

[meuge]

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On 7/29/2005 1:42:45 PM MrMcGoo wrote:

It is no big deal that the RF-7s fall off like a rock below 50 Hz. The RF-7s fall off by 20 decibels from 50 Hz to 30 Hz per Home Theater Mag's tests.

Bill

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I find that hard to believe, given that my RF-3IIs are reasonably flat down to about 40Hz... and that's in my tiny room.

[MrMcGoo]

Well Eugene,it's on page 56 of the August, 2002 Home Theater Mag. A closer look at the scale shows it's only a 10 db drop like a rock, so I do stand corrected.

Bill

[meuge]

Well, I can see that, sort of. They are rated to 32Hz, after all... So under perfect conditions, they can be -3dB at 32... and more like -6dB under unfavorable conditions, with another -3dB down to 30. It's not unheard of. My room screws with my subwoofer so much, that even though anechoically (tested outside), its -10dB point is around 19Hz, it manages to drop from flat to nothing (at least -30dB) in the space between 32Hz and 26Hz.

[rockbobmel]

With no formal knowledge, but a bass player. I have had this similar discussion on the talk bass boards. It is a constant arguement of multi small drivers v. single/double larger drivers. 10s are in the middle somewhere. This is my take...... Larger drivers are more capable of producing the fundamental notes (31.5hz for low B, and 40hz for a low E) that CAN produce a lot of undefined rumble. They tend to be slower and CAN be mushy sounding. NOW, the 10s and 8s (like the sealed Ampeg 8-10 SVT), which was originally designed to use 2 of rated as 52Hz, for a 300W tube head, and the (ported SWR Henry the 8 x 8) which uses 8 Celestion 8s. is rated at 30Hz, are faster and more defined sounding. One big reason for this is that we HEAR mostly,-the harmonic content of the note,- not the fundamental. We feel more the fundamental and we hear more the harmonic content, and our brain puts these together. As a rough example for this, If you listen to someone on the phone, you recognize their voice and do not distinguish it from hearing them in person. However in person, you hear all the dynamic range of their voice as well as feel it. Over the phone you hear a portion of their vocal content (upper Hz), and your brain fills in the rest.