Headroom and Tell me about 90 dB SPL... Is it enough?

Discussion in 'Archived Threads 2001-2004' started by altan, Jan 7, 2003.

  1. altan

    altan Stunt Coordinator

    Joined:
    Nov 19, 2002
    Messages:
    81
    Likes Received:
    0
    Trophy Points:
    0
    Using
    http://www.crownaudio.com/apps_htm/c...gn/amp-pwr.htm
    I've determined that at 3.65 (12 feet) from my mains (with 86 dB sensitivity 1W/1M), using 3dB headroom, I can get 90 DB SPL with 67 Watts.
    (I'm considering the HK 525 which is 70 Watts)
    Is 90dB enough? I know 105 is reference... Does 90dB blow your head off or is it not loud enough?
    Also, do I really need to include the 3dB for headroom? Looking at it another way, is the 105 dB reference a MAX and therefore the 3dB headroom is unnecessary?
    Thanks!
    ... Altan
     
  2. Yogi

    Yogi Screenwriter

    Joined:
    Jul 25, 2002
    Messages:
    1,741
    Likes Received:
    0
    Trophy Points:
    0
    105 db is max with the sub attaining 10 db over that. So if your system with the sub can attain 115 peak SPLs you will have full uncompressed theater experience. Normal dialogue levels are 85db with peak effects getting into the 105 level. So if you want to go to a max of 90db on your effects then you will be listening to dialogues at 70db which will be quite soft.

    Having said that I have listened to the HK 520 and felt it more than adequate to give you the full theatrical experience, so obviously there is more to the 70W rating that HK states. I would think that the 525 will output 70W RMS continuously but probably has a 3db headroom meaning it can output 140W for short bursts which is typically how long the movie special effects would last. To make a long story short I think the 525 will be more than adequate with your 86db speakers to play at reference levels so rest easy and buy that great piece of gear.

    Best of luck.
     
  3. John Kotches

    John Kotches Cinematographer

    Joined:
    Mar 14, 2000
    Messages:
    2,635
    Likes Received:
    0
    Trophy Points:
    0
    Altan,

    I'm not sure I agree with Crown's (and therefore) your overall SPL....

    Let's see. Drop is via inverse square for 3.65 m.... Approximately 11dB.

    Gain of amplifier, approximately 18dB.

    Assuming your room is an anechoic chamber, it would be more along the lines of 93dB at the seats at full rated output of the receiver.

    When you add in 3-4dB of room gain, it's closer to 96 or 97dB.

    BTW, 86dB is low sensitivity. What speakers are you using that are 86dB? That almost sounds like a Planar source, which has a different loudness decay.

    Regards,
     
  4. altan

    altan Stunt Coordinator

    Joined:
    Nov 19, 2002
    Messages:
    81
    Likes Received:
    0
    Trophy Points:
    0
    John,

    thanks for the response. The speakers are Paradigm Studio/60's. They are 87 dB anechoic and 90 dB in a "room" (I believe).

    I'm hoping 96 or 97 dB SPL is pretty good since a lot of people listen 6 or more dB lower than reference.

    ... Altan
     
  5. Brian L

    Brian L Cinematographer

    Joined:
    Jul 8, 1998
    Messages:
    2,937
    Likes Received:
    24
    Trophy Points:
    1,610
     
  6. altan

    altan Stunt Coordinator

    Joined:
    Nov 19, 2002
    Messages:
    81
    Likes Received:
    0
    Trophy Points:
    0
    Thanks Brian! I'll let you know how it works... I ordered the 525 today.

    ... Altan
     

Share This Page