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Thread: DBX DriveRack 4800

  1. #31
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    Quote Originally Posted by grumpy View Post
    yes, appears to be ~$4000USD
    Denmark can be a pain when it comes to prices.. Even though one dollar is 5,5 Danish crowns, a rule of thumb says, that we can multiply the US price with 10 to get the Danish price. I actually think, that the one I got was bought in the US... Its a universal power supply, so it fits perfectly to our 230V power grid.

  2. #32
    Senior Member Lee in Montreal's Avatar
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    Quote Originally Posted by Jonas_h View Post
    Denmark can be a pain when it comes to prices.. Even though one dollar is 5,5 Danish crowns, a rule of thumb says, that we can multiply the US price with 10 to get the Danish price.
    Must be a very high import tax. Something's rotten in the kingdom of Denmark

  3. #33
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    Quote Originally Posted by Lee in Montreal View Post
    Must be a very high import tax. Something's rotten in the kingdom of Denmark
    Haha, yeah taxes are very high! But we get a lot of stuff for free then. But when you do not need all those things at the moment, you tend to think the money cuold have been spent better elsewhere (like new gear for the home theater ).

    But I am very happy for my purchase of the DBX. A week ago, I got a similar offer on 4 Crown CTs amps (just under half the price), so it has been a good couple of weeks... Bad for the bank account, but in the long run, I have saved a lot.

    You mention you have the DCX? Do you have any problems with the SN ratio?

  4. #34
    Senior Member Lee in Montreal's Avatar
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    Quote Originally Posted by Jonas_h View Post
    You mention you have the DCX? Do you have any problems with the SN ratio?
    I do have some floor noise, caused by the in/out digitsl amplification. I just reduce the input of my amps and increase the output of my preamp. BTW The noise is only audible when no music plays.

    Strangely, my analog Behringer CX3400 is exempt of such noise.

  5. #35
    Senior Member Eaulive's Avatar
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    Quote Originally Posted by Lee in Montreal View Post
    I do have some floor noise, caused by the in/out digitsl amplification. I just reduce the input of my amps and increase the output of my preamp. BTW The noise is only audible when no music plays.

    Strangely, my analog Behringer CX3400 is exempt of such noise.
    An analog crossover has physical attenuators at the output stage when a DSP has not.
    The output of the DAC is fed directly to the output driver and then to the output connector.
    Attenuation is done digitally, when you attenuate the output signal you're really not doing anything in the analog domain. You only have less headroom, that's why it's so important to set the gain structure properly with a digital unit, even more than with an analog one.
    You have to use all the headroom possible, meaning you have to feed the unit with the maximum signal. Most units will accept in excess of +20dBu., many times more than any consumer preamp is able to supply.

  6. #36
    Senior Member maxwedge's Avatar
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    Quote Originally Posted by Jonas_h View Post
    My horns are not the ones that are used on the 3678 if that is what you mean?

    As I said, I have level matched the HF and LF sections by setting them according to their sensitivity. I have verified this with REW, so no reason to turn down the HF

    Dont underestimate the size of the horns...:

    Almost same size as a 32" TV.
    I know that the space between them is not optimal, but my room is not big enough for more space. My next place, I will have a dedicated room for the home theater (currently its both living room and home theater), and hopefully it will be big enough to space out the speakers a little more. I'm getting good seperation of the sounds though. I can easily pinpoint the sound to the screen when the sounds travels from one speaker to the other. (The Pixar intro is a very good example!).
    Ah yeah, I like those! One day............................................... ....

  7. #37
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    A little update... Yesterday I hooked up the new amps and the DBX 4800... The gain on both amps are about 30% up for both the HF and LF driver, and there is absolutely no hiss. Im really satisfied with the DBX. S-sounds are now very good and not fatiging at all and it just sounds like, a thick fabric has been removed from the speakers.

  8. #38
    Senior Member Eaulive's Avatar
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    Excellent.
    Thanks for the update

  9. #39
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    In regards to gain structure... How is the best approach to ensure that this is done correctly? I can set the input/output sensitivity on the DBX. If I set the output sensitivity to 14dBu, the hiss is completely gone, but when I listen to movies on reference levels and there is a lot of action in the movie, the DBX almost hits the clipping point. This does not happen if I set the output sensitivity to 20dBu, but a small hiss is introduced though.

    Is the best approach to adjust the gains on the amplifiers? I dont like the idea of not being able to level match the HF/LF sections on the DBX only by using the sensitivities of the individual drivers. If the amp gains are not equal, then I cannot be 100% sure that they are level matches as they should be.

  10. #40
    Senior Member 1audiohack's Avatar
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    Hi Jonas;

    When you are at maximum signal level input, almost clipping is where you want to be, not clipping, but almost. That is where the device is capable of delivering maximum signal to noise.

    What is currently in you signal path?
    If we knew what the hell we were doing, we wouldn't call it research would we.

  11. #41
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    Quote Originally Posted by 1audiohack View Post
    Hi Jonas;

    When you are at maximum signal level input, almost clipping is where you want to be, not clipping, but almost. That is where the device is capable of delivering maximum signal to noise.

    What is currently in you signal path?
    My path is Onkyo PR-SC5508 (surround processor, balanced outputs) -> DBX Driverack 4800 -> Crown CTs amps.

    The gains on the amps are not set very high - I have read that Crown recommends setting them at 3/4 for best performance, so maybe they should be set higher for better performance?

    Would it be a good idea to send pink noise from my processor set at 0dbFS and make sure, that the DBX is not clipping (but at "almost" clipping)? Of course with the amps turned off - otherwise I would go deaf

    EDIT: The Crown gain comment edited.

  12. #42
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    The DBX makes me setup the sensitivities like this:


  13. #43
    Senior Member 1audiohack's Avatar
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    I can't see what you tried to post.

    The short of it is since everything in the chain makes its own noise and adds it to the signal as it goes, you want to get all the gain you need in as early as possible as not to amplify the self noise further down the chain.

    With the Onkyo wide open, you want the input stage of the 4800 almost clipping. I would just adjust the input of the 4800 by your listening trends, if you see it clipping when your running it hard, just pull some input gain out, it wont take long to get that set and if you clip it one in a while its not the end of the world.

    If you can then set the output levels of the 4800 to unity, zero dB gain or cut (found in the last page of the crossover parameters I believe) and still have adequate voltage (and it should) to drive the amps to satisfactory level (loudness) with out the amp input attenuaters wide open that will likely be as good as it gets.

    Keep me up on what and how you do with it. If I did a bad job at explaining let me know and I will try it again.☺
    If we knew what the hell we were doing, we wouldn't call it research would we.

  14. #44
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    That was a good explanation! I will try it as soon as possible. When you say, unity gain on the output, does this mean setting it to the same value as the input?

    I was linking to ths in the post before: http://www.martinloganowners.com/for...1&d=1211144106

    This is the options I have for setting the input/output sensitivity.

  15. #45
    Senior Member 1audiohack's Avatar
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    In the crossover section as you page through I think it's the last parameter, all it says is gain with a little arrow pointing to a number, 0.0 is unity meaning if one volt comes in, one volt goes out, so now your not amplifying anything done after the input stage, just passing whats there along to the amp.

    You can run that number from -60dB to +20dB if I remember right. If you can leave that at 0.0dB you will acheive the best signal to noise ratio while keeping the most dynamic range.

    This individual channel output gain stage is independant form the input gain stage.
    If we knew what the hell we were doing, we wouldn't call it research would we.

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