do i really need a amp??????

Discussion in 'Archived Threads 2001-2004' started by David D. C., Jan 5, 2002.

  1. David D. C.

    David D. C. Stunt Coordinator

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    i am going to purchase a denon 2802 reciever which puts out

    the amplifier channel power is as follows

    front: 90 watts x 2 (8 ohms 20hz - 20khz, 0.05% thd)

    center: 90 watts (8 ohms 20hz - 20khz, 0.05% thd)

    surround: 90 watts x 2 (8 ohms 20hz - 20khz, 0.05% thd)

    surround back: 90 watts (8 ohms 20hz - 20khz, 0.05% thd)

    the speakers i have for my surround backs are sony ssm-b100h's the peak power handling is 100 watts at 8ohms.

    the speakers i have for my fronts are sony SSM-b300h's the peak power handling is 140 watts at 8ohms. with recommended rms power at 120 watts.

    the speakers i have for my surround's are sony SS-SR305's the peak power handling is 100 watts at 8ohms.

    the speaker i have for my surround center is sony SS-CN305 the peak power handling is 120 watts at 8ohms .

    First Question: If I add an amp, what power range should I look for on it?

    Second Question: Do I even need to add an amp?

    Third Question: Should I have better speakers if I decide to get an amp?

    There's a section called specifications for power amplifier section that reads as follows:

    rated output for the following;

    front: 90 watts x 2 (8 ohms 20hz - 20khz, 0.05% thd)

    135W x 2 (6ohms, 1khz, 0.7% thd)

    center: 90 watts (8 ohms 20hz - 20khz, 0.05% thd)

    135W (6ohms, 1khz, 0.7% thd)

    surround: 90 watts x 2 (8 ohms 20hz - 20khz, 0.05% thd)

    135W x 2 (6ohms, 1khz, 0.7% thd)

    surround back: 90 watts (8 ohms 20hz - 20khz, 0.05% thd)

    135W (6ohms, 1khz, 0.7% thd)

    Fourth Question: Is this the section that tells me what my max power would be with and amp, or is this the max output power if I had 6ohm speakers?

    Fith Question: If I decide to keep my speakers as listed earlier, is the chance of blowing them if I add an amp? I'm afraid they might.
     
  2. Arthur S

    Arthur S Cinematographer

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    Not with your previously mentioned "reference amps".
     
  3. Keith Mickunas

    Keith Mickunas Cinematographer

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    I'd think you'd be better off waiting until you have better speakers before buying an amp. The power rating on the speakers isn't really that significant. What's more important is the efficiency and impedance. Those speakers are probably average in that respect and won't be a problem for your amp. As for blowing them, only if you play it real, real loud. Regardless if you have a 90 watt or 500 watt amp, they put out the same wattage at the same volume. It becomes a matter of how clean those watts are and how much headroom you have. More than likely your Sony's will be distorting before you hit the maximum output of the Denon when it comes to really loud passages in action movies.
     
  4. David D. C.

    David D. C. Stunt Coordinator

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    if my memory serves my right the higher the independance the less likely you will have a roll over effect from another freq right????if the front operates at (lets say an independance of 90) this is good right? you want higher independance on your speakers right? not lower. do you want higher independance on all speakers?? i think so.

    im not sure i understand efficiency real well could some one inliten me on this
     
  5. Keith Mickunas

    Keith Mickunas Cinematographer

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    The impedance changes across frequencies, but I don't know a whole lot more about it. Most of your average speakers from places like Best Buy and the like are rated at 8 Ohms, and this is really more of an average or nominal ratings. Amps are rated rated into 8 Ohms also, as your Denon is. Most likely your Sony speakers are the same and a good match for the Denon. Some higher end speakers offer lower impedance which require more current. For instance Martin Logans are 2 or 4 Ohm, I don't remember which. This requires an amp that can maintain a lot of current. Good amps will be rated something like 200 watts into 8 Ohms, and 400 watts into 4 Ohms. However many receivers won't provide the 4 Ohm rating because they just can't pump out the current do to their limited power supply. That's about the best I can do for an explanation. All I know for sure is that when you get to the higher end speakers, you need the higher end amps to power them.

    As for efficiency, this is how much sound it produces at 1 meter with 1 watt. For instance, my Polk center channel (whose manual just happened to be sitting nearby) is 91dB. So with my amp giving it just 1 watt it should produce 91dB, which is pretty loud. You have to double the power to achieve an increase of 3dB. So 2 watts gives me 94dB, 8 watts for 100dB, 128 watts gets to 112dB.

    As for the rollover you mentioned, I know nothing about that. Mostly all I know is about what you need from your amps and speakers to get good sound, but I don't fully understand the theory behind it all.
     

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