Efficiency?

[browe1967]

What is good efficiency? If my speakers are 96db would 125 watts be enough? Or should I use the XPA3 for 200 watts? I know I have asked before but if my speakers are very efficient, do I really need the extra power? A single UPA5 would be a much easier purchase than a XPA3 and a UPA2 later. I just don't want to regret my purchase.

[iketremonti8]

that is a very high efficiency speaker whatever it is. Klipsch?? I'm not the Emo pro around here at all, but I can tell you that is very high efficiency at least. I'm guessing that most people would tell you that the 125 watts would be plenty..just my 2 cents

[Deleted]

I think I made a post before about your system. First it looks as if you are using the RVX-42's as LCR and the SS.5's as surrounds. The RVX-42's have an efficiency rating of 94 dB's and the SS.5's of 90dB's. The lower efficiency on the surrounds is fine because the volume is not usually as high in the surround channels. For music you will sometimes use the CF-1's which are rated at 96dB's in efficiency.

Here is the big difference. The CF-1 will handle more maximum power than the 5 speakers for your HT. Thus they will not only play louder to begin with because they are of higher efficiency, but they will also play at a higher maximum level because they can handle more total power. The other five speakers will run out of volume capability before the CF-1's will.

So you have got two rather different classes of speakers here even though they are from the same brand. Please correct me if I'm wrong but you plan to run both the 5 speaker system and the 2 speaker system from the same amp.

I recommend for your stated purposes that you buy the UPA-5 and here is why. When you are powering the 5 speakers you will have an amp that is an excellent match for these five speakers, their efficiency and their specified power handling. When you are powering the two CF-1's you will have only two channels operating of the UPA-5 total five channels and thus will get in excess of the specified 125 watts RMS (at 8 ohms). I estimate it to be about 30% more power and about 165 watts (at 8 ohms) into the CF-1.

Now I did find a review on the RVX-42's that measured the impedance at 4.34 ohms at 295Hz and an efficiency of 92dB's (remember in my other post I said I thought the specified efficiency rating of 94dB's might be a little high). So it looks like from the review by HT magazine we have the RVX-42 at about 92dB's and an estimated nominal impedance of 6 ohms or so. (just a guess here but it is apparently lower than the specified 8 ohms but not down to 4 ohms). So it will draw more like a maximum RMS from the UPA-5 of about 155 watts (6 ohms) but at a slightly lower efficiency which I would call a wash for producing relative volume. Klipsch specifies the maximum RMS and peak powers for the RVX-42 at 75/300 watts and for the SS.5 at 50/200 watts. It is optimum to have about double the estimated RMS power for extra headroom if possible for very high sound level peaks. Klipsch specifies the CF-1 at 150/600 watts for RMS/peak.

I would guess that the actual impedance of the CF-1's might also be closer to 6 ohms and thus draw more like 205 watts (6 ohms). With a efficiency of 96dB's that means that you would hit about 119dB's at one meter distance per speaker. In your room that would easily seem to be a very loud 110dB's or more at your listening area. The RVX-42's would hit about 114dB's at one meter and meet the movie maximum reference level at your listening position of 105dB's.

I would call the UPA-5 almost a perfect match for the 5 speakers and also for the CF-1's in two channel mode. The XPA-5 would be even more headroom but not at all necessary IMO. I would recommend this over the XPA-3 plus the RXV-665. (when you replace the RXV-665 with the UMC-1 you'll be glad you have the 5 channel amp ;D)

[browe1967]

thank you chuckienut. You have made my decision easy now. Thanks for the actual specs on my speakers. It is hard to know for sure if the makers are always right about specs. Do you have a link to that test of the speakers? I would like to read it sometime.

UPA-5, here I come.

[browe1967]

and yes, all speakers with one amp. I have an Adcom speaker selector switch to swap between the mains

[Deleted]

www.hometheatermag.com/floorloudspeakers/605klipsch/

[browe1967]

Thanks