#12622 - 02/26/04 12:42 AM
One more time on amp selection and head room
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Gunslinger
Registered: 02/18/04
Posts: 20
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Guys, I'm sorry for bringing this up one more time, but I am really worried about which way to go. I have been reading about head room, and there's never too much power. ( within reason )and so on. The other side of the coin, is too little power will kill a speaker quicker than the blink of an eye, ( distortion ). Third, I have recently seen a little discusion about being so over powered, that the amp isn't working hard enough to run clean. Any thoughts on that theory? So, as many have been, and many will be, I'm at the fork in the road. 770, or 7100. I have Klipsch RF-7's and RC-7 for the mains, and will have RCW-5's, or RS 35's for surrounds. Two pair of either. Denon 3801 as pre amp for now. I wouldn't say I play everything loud, all the time, but action movies are sometimes, meant to be, loud, and multi channel audio, sometimes is meant to be, loud. I have fun with my system, when I get a chance. Thats why I built it. This is the first time I will have crossed over to separates, and I want to get it right, the first time. My experience, as does the Outlaw tech, tells me I'm on the edge with my surrounds, ( the in walls ) but I have this desire to go ahead and buy the 770 anyway. More so, being there is a chance I may end up with the better surrounds, ( RS 35's ) in the end. What do you all think?, Could I possibly get by with running the 770 on the in walls, if thats what I end up with? Again guys, Thanks so much for the help. I'm ready to put this upgrade into action. GRCRY,...>>>---> ps,..Posted in the Outlaw to Outlaw forum, hoping to get better exposure. The amp forums seem to be a little slow right now. Hope this is ok,....
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#12623 - 02/26/04 12:54 AM
Re: One more time on amp selection and head room
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Desperado
Registered: 04/10/02
Posts: 1857
Loc: Gusev Crater, Mars
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The difference in power is double - 100 watts verses 200 watts per channel. That equates to a 3db volume difference which is just noticable. You could probably go either way, but personally, I think that 100 watts with your speakers is plenty, considering their efficiency.
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#12624 - 02/26/04 02:24 AM
Re: One more time on amp selection and head room
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Gunslinger
Registered: 03/31/01
Posts: 129
Loc: las vegas, NV 89031
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Go ahead and get the 770. You will never need to purchase another amplifier. 'Nuff said.......
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#12625 - 02/26/04 06:37 PM
Re: One more time on amp selection and head room
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Gunslinger
Registered: 02/18/04
Posts: 20
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Thanks guys,..I'm with you on both thoughts. Is there anything to the idea, not running an amp to a fair amount of it's rated output, could introduce noise? I hadn't heard of this before. Thanks GRCRY,...>>>--->
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#12626 - 02/26/04 07:35 PM
Re: One more time on amp selection and head room
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Desperado
Registered: 04/10/02
Posts: 1857
Loc: Gusev Crater, Mars
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I wrote a long post on this subject that is buried somewhere in the archives. Basically, the more efficient your speakers are, the less gain you want from your power amplifier. A more powerful amplifier has more gain than a less powerful one, and the inherent noise from the amplifier is raised. A less efficient speaker will not make this noise as obvious as a very efficient speaker will, and horns are very efficient.
Also, the less of the available power your use from a class A/B power amplifier, the closer you are to the point where the "upper" and "lower" transistors hand over the signal. The area of this transistion can contain small amounts of what is known as crossover distortion, and this is made more audible by efficient speakers. A less powerful amplifier that is driven harder has less of it's signal residing in this crossover region. A powerful amplifier that is barely diriven spends most of it's time in this crossover region. The resulting sound can be harsher and grainier.
The best solution with speakers that are very efficient is a class "A" amplifier that has no crossover distrotion potential at all since a single output device or devices reproduce the entire signal. Vacuum tube class "A/B" power amplifiers are better than class "A/B" solid state amplifiers in regard to crossover distrotion because there is far more overlap between the upper and lower halves of the signal between the output tubes. The ulitmate solution is class "A" tube amplification for very efficient speakers, but this can be an expensive path.
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#12627 - 02/26/04 09:40 PM
Re: One more time on amp selection and head room
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Gunslinger
Registered: 02/18/04
Posts: 20
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soundhound,.. Thanks for that info. I thought I had read about this. Well shoot. Any idea if running the RS 35's or the RCW5's with the 770 would fall into this range. Is there a rule of thumb, so to speak, one can make judgement with, when pairing componants? I have this nagging desire to own the 770, but if I knew for sure the 7100 was a better mate to the speakers, that would over rule it. Thanks GRCRY,...>>>--->
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#12628 - 02/26/04 10:51 PM
Re: One more time on amp selection and head room
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Desperado
Registered: 04/10/02
Posts: 1857
Loc: Gusev Crater, Mars
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All I can say is that I have speakers that are 106db/watt efficient. I use a 50 watt tube amp for the woofers (which is overkill) and a 5 (five!) watt for the highs in an active bi-amped configuration. I can tear down the walls with this amount of power. If your main speakers are really 101db/watt efficient, you can draw your own conclusions. [This message has been edited by soundhound (edited February 26, 2004).]
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#12629 - 02/27/04 12:41 AM
Re: One more time on amp selection and head room
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Desperado
Registered: 12/29/02
Posts: 358
Loc: Central VA
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Ifyou go to the Klipsch web site, search for your speakers (RF-7) then click on FAQ and scroll down. They have a very good chart that shows a speakers effeciency and the amount of power needed to achieve different SPL's. Your RF-7's would need 64 watts to achieve 120dB, my inefficient NHT's would need 2048 watts to achieve the same SPL. Your center would need about 300 watts for the 120dB. In the larger picture I doubt you will listen to anything at such levels. Maybe the chart will help put SH's advice into perspective.
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#12630 - 02/27/04 07:43 AM
Re: One more time on amp selection and head room
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Gunslinger
Registered: 02/18/04
Posts: 20
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Guys, thanks for the info,..I made a chart like you mentioned myself. It's interesting to see each speaker's output levels when relating it to a consistant input. I'm use to car audio, and still have very high db,a nd spl levels stuck in my head. Thanks again,...GRCRY,...>>>--->
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#12631 - 02/27/04 10:16 AM
Re: One more time on amp selection and head room
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Gunslinger
Registered: 05/29/03
Posts: 297
Loc: Middle Earth
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Originally posted by soundhound: The ulitmate solution is class "A" tube amplification for very efficient speakers, but this can be an expensive path. It can be expensive but there seems to be an exception. GRCRYSTYK, look here http://www.decware.com/new%20site/mainmenu.htm
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