Is 70 watts enough power?

Discussion in 'AV Receivers' started by Alex_C, May 22, 2003.

  1. Alex_C

    Alex_C Stunt Coordinator

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    I have a room that's 22'x25'. The speakers I own have a sensitivity of 86. The receiver I'm thinking about is the H/K 525 with 70 watts per.

    I was looking at the home theater receiver buying guide and it indicated I should have a receiver with 76 watts per.

    The other system I'm looking at is the Denon 2802 which is 90 watts, but I like the H/K more.

    Do you think it's a bad idea to get the H/K?

    So, close to a decision, yet so far. . .
     
  2. Pablo Abularach

    Pablo Abularach Supporting Actor

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    Alex,

    I believe more Harman Kardon Ratings than Denon ratings. I think the AVR525 has more power than the 2803. But go and audion both.

    Check this forum, it might help you.

    H/K 525 vs. Denon 2803 strictly for HT? Page

     
  3. Angelo.M

    Angelo.M Producer

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    I'd take the h/k. It ought to have more than enough power for that room. Ignore the numbers.
     
  4. Alex_C

    Alex_C Stunt Coordinator

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    Thanks! That thread was very helpful.
    I think I'm going to order the H/K 525. First, I have to pick a DVD player to order at the same time.

    On to the next forum. . .
     
  5. Yogi

    Yogi Screenwriter

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    Neither the 2803 or the 525 (even if it did 150W/ch) is sufficient for your room. You have a fairly large room with fairly insensitive speakers. Remember the numbers quoted above are if you are listening at a distance of 1m from the speakers. As you double the distance the SPL falls off at about 3db (I think). So I take it you will be atleast sitting 18 feet from the speakers and so those numbers in the table above will drop by atleast 6-7 db which means you will only be able to achieve about 97 db SPL levels. To achieve THX reference levels of 105 db on mains you will need atleast 150W of power per channel. You can go to this nifty calculator here to compute the SPL levels you can achieve at listening position after entering some input data:

    http://www.myhometheater.homestead.c...alculator.html

    You will most definetly clip if you try to listen at reference levels. If you listen to lower levels you might be OK. If I were you I would atleast get a separate used amp for the mains with about 200w/ch. As for the Denon and HK they both are good musical receivers. The HK rates their amps conservatively but I frankly dont like the HK build quality. They both should function very well as preamps for the front two channels.

    Hope that helps.
     
  6. Darrel McBane

    Darrel McBane Second Unit

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    Every time I see that db to watts chart I just shake my head.

    It means nothing in the real world as far as deciding on how much power one needs in a system. [​IMG]
     
  7. Yogi

    Yogi Screenwriter

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    Darrel its just a convenient tool. Nothing fundamentally is being voilated here. To fully reproduce the 20 db dynamic range of DD tracks you need 100 times more power from dialogue levels. Its simple physics thats all. It doesnt take much for a 100W/ch amp to clip esp with insensitive speakers and low powers. Also I am afraid that the HK525 or the 2803 would be operating at or near its power limits with such insensitive speakers and this large room. There would be no head room left. I can bet my two cents that if he were ever to crank up his HT to listen at reference levels for extended periods of time he would be in for a treat. I would never do that to my speakers.

    MHO.
     
  8. Michael Yung

    Michael Yung Stunt Coordinator

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    What complicates this problem even further is the fact that manufacturer specs is not always correct. If you go to this site, someone had collected the S&V's test results and put it all into one clean table. And from this table, you can see that accroding to S&V, the Denon 2802 was rated at 71 watts instead of the advertised 90 watts.

    Generally I like both H/K and Denon receivers. I don't think your speakers will kill either receivers as long as you don't crank it up all the time. So try to audition both of them at home w/ your speakers if possible. It's the only way to tell for sure.
     
  9. Darrel McBane

    Darrel McBane Second Unit

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    I agree with you Yogi as far as it being a tool. But, I see people put that up like it's all one needs to know to determine how much power will work for someone else's room.

    If we all sat right next to our speakers. And played nothing but elevator music. We could all get by with a little more than 10 watts. [​IMG]

    But, a room 22'x25'x? is going to take a little more power than a 70wpc receiver. Unless you have several powerhouse subs IMO.
     
  10. Lee-M

    Lee-M Stunt Coordinator

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    If you are fairly picky about sound; if you like the idea of re-creating a live-sounding concert, or real theater-quality sound, do yourself a favor... get as much power as you possibly can.

    Your speakers, as others have commented, are pretty insensitive. And no, I don't mean that they are mean and will make you cry. I mean that they need a lot of power to even come close to meeting the goals I listed above.

    Separates are great, but not everyone can afford them at the start. If you must go with a receiver, do not settle for anything less than 120 watts per channel, 150 or more preferably. You will be doing your speakers, and your ears, and great disservice by powering them with anything less.

    I own some of the most sensitive speakers on the market (Klipsch), but they did not even begin to show me what they were capable of until I started powering them with 185 clean watts. And while they do not always use, or need, that much power, the bass slam and live feel I gained put me back on the track of audio and video pursuit that I have enjoyed for a long time.
     
  11. John Dude

    John Dude Auditioning

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    Hello Alex,
    Is 70W enough, well, it depends. How loud do you want to play? As mentioned above, being your room is a good size, it will take more power to reach higher levels than most standard home rooms.

    For instance, to reach 85dB at your back wall, distance of 25' with 86dB sens. speakers, you will need about 46W. Now, if you pump that up to 105dB for the +20dB headroom, you will need 4,564W! And this is just counting distance, not room volume.
    Let say you are 18' as mentioned above. 85dB reference with your speakers will require about 24W. And then to reach a level of 105dB would only require about 2359W.

    One thing you should avoid is clipping. I know of no receivers that have a clip indicator. Now, if you were to get a separate amp, you may have such a indicator, especially if it is a pro amp. Hmmm, I would bet many people clip their system and don't even know it.

    So, is 70W enough? Yes and no, depends on what level you want.
     
  12. ChrisWiggles

    ChrisWiggles Producer

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    If you're setting everything small, there's no way you're gonna run out of power. You should be fine with the 525. You'll probably be sucking much more power for two speakers run full-range for stereo than you will with 5-7 crossed over for movies. All the heavy lifting is for the bass, and if all that is being taken care of by the sub there really should be no problem at all.
     
  13. Michael R Price

    Michael R Price Screenwriter

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    Well, if they are 86db sensitivity, unless they are big-time speakers (I mean the usual big inefficient tower type, as opposed to satellites) they might be the limiting factor in dynamics instead of amplifier power. Also, max power output isn't the only thing affecting your sound quality...

    Alex what speakers specifically are you using, and what's the crossover frequency?
     
  14. LanceJ

    LanceJ Producer

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    I think 70 watts will be fine, unless you have five really large floorstanders with 2 10" woofers in them or something similar [​IMG]. This misguided preoccupation (by the marketing departments) with the magic "100 watts per channel" figure is really misleading.

    And H/K amps are usually underrated anyway ("high-current" is NOT just a marketing gimmick).

    And personally speaking, listening to movies at reference level is too damn loud--I don't care what the movie industry says.

    LJ
     
  15. EdNichols

    EdNichols Second Unit

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    A really dumb question, what does clip mean? Is that the same thing as distort?
     
  16. Yogi

    Yogi Screenwriter

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    Clipping comes after distortion. Both are bad for tweeters. Clipping esp can be disastrous. When you hear loud pops from your speakers then your amp is clipping.

    Quote:
    "Let say you are 18' as mentioned above. 85dB reference with your speakers will require about 24W. And then to reach a level of 105dB would only require about 2359W."


    That is only true if he used one speaker. He is using 5 speakers so he gets an additional 7db of reinforcement from multiple drivers. Also if his speakers are within 2-4 ft from the walls (which would very likely be the case) he gets additional bass loading of 3db. So he gets a total of 10db gain. So his power requirements would drop by a tenth of the number you quoted, i.e., about 236W which I think is more like a real estimate of his power requirement. Any amp with 150+ watts/ch with a headroom of about 2db would be more than sufficient in his case, just to be on the safe side. That is not to say that he might be perfectly happy with a 525 and might never feel the need to upgrade to morepower. I just like to have spare power reserves for the occasional action flick that I might watch at reference level (even though I have never watched any movie at reference level for the full length).

    My 2 cents.
     
  17. Mark Dickerson

    Mark Dickerson Stunt Coordinator

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    Alex:

    h/k watts are worth more than Denon watts because of the beefier power supply (it is like horsepower ratings in cars--japanese horsepower is not as powerful as German or American horsepower because they all calculate horrsepower differently). I actually have a bigger room than you do and I auditioned the 525, which had no trouble driving my very inefficient Magnapans (84 db/watt/meter) to very nice levels (and I like my music loud!). Get the h/k
     
  18. Alex_C

    Alex_C Stunt Coordinator

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    I have Definitive Technology 2006 fronts. I don't know the crossover frequency. I don't even know what that is. [​IMG]
    I sit about 8-10 feet away from the TV/fronts/center.
    I will only be using this setup for home theater. No music.
     
  19. PeterCB

    PeterCB Agent

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    Alex,

    The Def Tech 2006s have a powered subwoofer with a built in 250 watt amp in each speaker, so I think you will be fine. If you have one of Def Tech's powered centers, like the 2300 C/L/R (150 watt built in amp), you will be even better.

    I run a similar setup with a receiver rated at 105 wpc, which in reality probably produces less than 70 wpc with all channels driven. I sometimes play movies as high as -5 db (my receiver maxes out at +18 db), and I haven't had a problem.

    Peter
     
  20. LanceJ

    LanceJ Producer

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