RF-7's for 2 channel listening

[sredmyer]

First the situation:

I have a 5.1 HT setup which includes RF-7's (front left) and right RC-7 (center) RS-7's (rears) and RSW-12 sub. These speakers are powered by a Harman Kardon AVR 7300 (125 wpc). I often use the system for 2 channel (+ sub) stereo listening. Sometimes this 2 channel listening is at extreme volumes (parties mostly). At these extreme levels it was obvious that the HK AVR's amps were not up to the challenge. To solve this problem I added an Adcom GFA-555 to drive the RF-7s. This worked quite well but I noticed that the Adcoms clipping indicators were blinking (during extreme listening). To solve this I added another Adcom. I now have two Adcom GFA-555's one to drive each of the two RF-7's. These Adcom amps, when bridged and run as monoblocks, produce 600wpc. Since the RF-7's are rated for only 250wpc I am concered about damaging my speakers.

Now the questions:

1) Is there anything I can put between the Adcoms and the RF-7s to protect the speakers from overdriving? If someone is going to suggest fuses then please indicate how I should calculate the amp rating of fuse required. Searching on the web I found these two devices
Powermax - Loud speaker protector
http://www.homestead.com/prosites-a...ndpowermax.html

Dynastar Electronics - Speaker-KnifeII
http://www.dynastarelectronics.com/
I am not an electronic guy and could not decide (from the web sites) how these devices actually worked and if they would do what I require. If anyone has any insight on either of these devices I would love to hear it.

2) Where can I find a device I can place between the amp and speaker that will show me how much power (in watts) is being drawn by the speakers. I am not interested in a typical VU meter but rather a true watt meter.

Thanx,

Steve

[wuzzzer]

600 watts PER RF-7 and you're worrying about damaging the speakers? How about damgaing your ears or the foundation of your house?? []

If you look at the Klipsch site they are actually rated at 250 wattsRMS/1000 watts peak. If you've got a capable enough amp (which you certainly do) don't worry about blowing the RF-7s.

[sredmyer]

I guess I should have mentioned that for these volume extremes the speakers are out on the deck and nobody is anywhere near them. They are yard speakers at that time.

And again since the amp is capable of providing 600 watts rms and the speaker only rated for 250 rms that seems like a recipe for some blown speakers to me.

Am I wrong about that?

[Fish]

I would not worry about the Adcom clip light only blinking.The clipping indicator lights up(blinks) long before damaging clipping,at least my 5500 said so in the manual.If it stayed on you would do some damage after awhile.That said 600 watts is gettin kinda far out and if you really crank and run long term not much could stand that.200 watts is plenty for all this speaker is capable of,nothin' wrong with more but you must use common sense.

[RTTR]

102db = 1w

111db = 8w

120db = 64w

126db = 256w

Trust me, you have nothing to worry about with your 600 watts driving the RF-7's you will greatly pass the comfort limit before you have to worry about doing that, unless you are sitting there with hearing protection on listening to your music.... Now stop worrying about it and go enjoy those RF-7's, Unless you want to give them to me. I'll be glad to take them off your hands.

[SteveRed]

102db = 1w

111db = 8w

120db = 64w

126db = 256w

I have heard these numbers many times and have always wondered where they come from. I assume they are theoretical. My experience is much different. As I explained in the origianl post, my RF-7's are in my HT as the front/mains (although they are used outside some). The sitting position is +/- 15 feet from them. With the preamp at 0db using the two Adcoms (600wpc) I experience 100db to 107db (measured with an RS SPL meter) at the listening seat while listening to a variaty of rock/metal. I have always wondered why my "real life" measurements are so far from the theoretical. Anybody know?

Trust me, you have nothing to worry about with your 600 watts driving the RF-7's you will greatly pass the comfort limit before you have to worry about doing that, unless you are sitting there with hearing protection on listening to your music.... Now stop worrying about it and go enjoy those RF-7's, Unless you want to give them to me. I'll be glad to take them off your hands.

As I said the speakers usually only get driven really hard when they are outside and nobody is really close. However, as I say above I do not get anywhere near the volume levels (SPLs) you suggest and therefore they (the RF-7s) do on occaision get driven hard inside.

I would love it if some one could tell me why my SPLs differ so from theoretic.

[skonopa]

102db = 1w

111db = 8w

120db = 64w

126db = 256w

I have heard these numbers many times and have always wondered where they come from. I assume they are theoretical. My experience is much different. As I explained in the origianl post, my RF-7's are in my HT as the front/mains (although they are used outside some). The sitting position is +/- 15 feet from them. With the preamp at 0db using the two Adcoms (600wpc) I experience 100db to 107db (measured with an RS SPL meter) at the listening seat while listening to a variaty of rock/metal. I have always wondered why my "real life" measurements are so far from the theoretical. Anybody know?

These are indeed "theoretical" numbers. The RF-7s is rated at 102db at 1 watt at 1 meter. That is, ideally, if you sit exactly 1 meter (a tad more than 3 feet) away from one of the RF-7, fed it exactly 1 watt of power, it should be 102 dbs loud. To go up 3dbs, you need to feed it doulbe the power, thus 2 watts should yield 105 dbs at 1 meter, at 4 watts, 108 dbs, 8 watts - 111 dbs, and so forth.

Now what you actually get could be different, for example you say you are about 15 feet away - a good 3 meters or so. I cannot remember off the top of my head what the formula, but every so many feet, the sound diminishes by so many decibels. Also, other facters, such as the room treatment and so forth could effect the numbers as well. If you are playing them outside, that will also effect it as you don't have any boundery interactions (i.e., sound reflections from walls and so forth).

For comparison, I've cranked mine up to the 0 position on my Denon pre/pro (actually an AVR-3802 reciever being used as a pre/pro) with a B&K Reference 200.7 amp driving the RF-7s (200 watts/channel). I got a good solid 120 dbs at the listening postion about 11 feet or so away with peaks close to 130 (or whatever - it was pegging the needle on my RS SPL meter). That is friggan LOUD, and on top of that, there was no sign of distortion or strain! The music as still very clean and clear!

[cubdog]

My ears are bleeding.

cubdog

[oldtimer]

Just don't clip.

[MrMcGoo]

The only problem that I see is with the low impedance of the RF-7s. A bridged amp has half of its normal ability to drive low impedance loads. The RF-7s go as low as 2.8 ohms. Keep an eye on the clipping meter on loud transients. If the clipping indicators do not come on, you are good to go.

I regularly run 625 watt amps to my RF-7s. I do not hit peaks over 105 db from the RF-7s. The big amp has better bass control and much better mid range control. Big amps are not really about watts ( except when they turn on and blow the breaker); big amps are about better ability to drive difficult loads cleanly on transient peaks.

Bill

PS: For the folks all caught up on Klipsch sensitivity, those clipping lights going on are the relevant data points, not theoretical and simplistic analysis of sensitivity. By the way Klipsch rates its speakers at 2.83 volts, not one watt, since the speakers are never a perfect 8 ohm load. B

[sredmyer]

For comparison, I've cranked mine up to the 0 position on my Denon pre/pro (actually an AVR-3802 reciever being used as a pre/pro) with a B&K Reference 200.7 amp driving the RF-7s (200 watts/channel). I got a good solid 120 dbs at the listening postion about 11 feet or so away with peaks close to 130 (or whatever - it was pegging the needle on my RS SPL meter). That is friggan LOUD, and on top of that, there was no sign of distortion or strain! The music as still very clean and clear!

This is exactly why I started this thread...I figured I should be able to get those kind of SPLs out of my system but I am not.

It is not that I want to listen at those levels but rather I just want to know if my equipment is functioning correctly. If my equipment is not doing all that it should, I want to know so that I can track down the problem and get it fixed.

[sredmyer]

I regularly run 625 watt amps to my RF-7s. I do not hit peaks over 105 db from the RF-7s. The big amp has better bass control and much better mid range control. Big amps are not really about watts ( except when they turn on and blow the breaker); big amps are about better ability to drive difficult loads cleanly on transient peaks.

About that turning them on and blowing breakers, any suggestions to suppress the thump on start up and the one after shut down when the caps in the amps finally give up their last?