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Thread: DBX DriveRack 4800

  1. #16
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    Quote Originally Posted by Eaulive View Post
    To put the level down is not a hack, but instead a proper way to setup gain structure.
    99% of the hiss problems when using DSPs are related to an improper setup.

    There are many threads discussing "gain structure" here and on many sites.

    I suspect your DBX 4800, even if it's a very good unit and better than the Behringer, will also introduce hiss in your HF if the gain of your amplifier is all the way up.
    They are not all they way up.. I think they are about 20% max. But how would you use the JBL presets for example? They assume, that the amp gains are set the same for both LF and HF. The same goes for the Synthesis systems which use SAM1HF/SAM2LF. The DBX should perform equally to the BSS London units (at least according to specs). But I'll try the DBX in a couple of weeks and see how bad the hiss is.

  2. #17
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    Quote Originally Posted by JBL 4645 View Post
    I’ve been going to Empire for 21 years since it had the original JBL 13KW Lucasfilm THX sound system that was damn hard edge hitting for Dolby Stereo 70mm!

    Well which screen at Empire Leicester square because they have I think its 8 or 9 screens now, screen 1 is the big THX 56KW JBL screen! All the other screens use JBL I think the horns are the ones used for JBL 3678 I think some screens have duel 15” while ones not big enough to swing a cat around have single 15”.

    I think you’ve set the HF far too high for small room. Try setting the level over LCR HF at 75db while using wideband pink noise. Use an RTA and SPL db metre to make sure each have the same pressure and that each tonally sound the same some might have more output in different parts of the frequency response only an RTA can see that where the SPL db metre can’t see it unless its plugged into an RTA!

    Mute the HF LCR and look at the level on LF LCR and set the level at 75db. The subs should be within a few db they should merge smoothly.

    They look kinder funky I could fit a model like that in my living room but not enough space for 5 fronts. I like the HF horn that I could easily fit in the room. How you managed it the LCR are far too close to each other where in small digital screen at Empire the spacing between LCR would be a lot greater to insure widest possible stereo.
    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!).

  3. #18
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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!).
    Why are you covering yourself up? Why not place the HF at head height at least then you’ll have some headroom.

    I find pink noise to be the best test signal than any film soundtrack! I use wideband first to set up then run the AVR pink noise that is narrow band cycling over LCR and I’m listening for the same tone on the LF or HF one at time then as whole! If the tone is out it could be only a few bands that need adjusting its no big deal. Its not conspiracy you know.

    I’d use a smaller 15” HF horn then if a set of them ever turned up the ebay for cheap price with compression driver and plastic horn.

    I’d use a smaller 15” HF horn then if a set of them ever turned up the ebay for cheap price with compression driver and plastic horn. But I’d still have the damn things turned down! I know what they sound like in cinema and often they sound too damn loud and that’s not good for the ears!

    LOL its no wonder you have hiss! I think you need DOLBY NR! One you have it up far too high! Two you’re far too close to them, where in cinema the front row would be at least 10 feet or more from the front of the screen and its only a few inches behind the screen where the JBL are! If you put you’re ear near to the screen before the films start between a music break I bet you’ll hear some type of hiss.

    Upon a visit a few years ago for Toy Story 3D in Empire #1 I took a few pictures of the small digital JBL screens. So a little peak behind one of the JBL screens.
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  4. #19
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    Quote Originally Posted by JBL 4645 View Post
    LOL its no wonder you have hiss! I think you need DOLBY NR! One you have it up far too high! Two you’re far too close to them, where in cinema the front row would be at least 10 feet or more from the front of the screen and its only a few inches behind the screen where the JBL are! If you put you’re ear near to the screen before the films start between a music break I bet you’ll hear some type of hiss.

    Upon a visit a few years ago for Toy Story 3D in Empire #1 I took a few pictures of the small digital JBL screens. So a little peak behind one of the JBL screens.
    What does hiss have to do with how high they are placed? Dont see the connection. I only have the hiss when the DCX is in the chain... With the amps alone, the speakers are dead silent. So I'm still pretty confident, that the DBX will remove the hiss - or at least bring it down to an acceptable level. I will update the thread when I have tried it. I'm not putting in another component to do Dolby NR.

    THe speakers in your picture are the 3678 as you mention. They have a tiny horn compared to the 4722, but the LF is pretty much the same. Just a little smaller, but same driver.

    EDIT: The hiss with the Behringer DCX is not as bad as you make it sound... I'm just annoyed that its noticeable when I am listening for it! But when watching a movie, I dont notice it.

  5. #20
    JBL 4645
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    Quote Originally Posted by Jonas_h View Post
    What does hiss have to do with how high they are placed? Dont see the connection. I only have the hiss when the DCX is in the chain... With the amps alone, the speakers are dead silent. So I'm still pretty confident, that the DBX will remove the hiss - or at least bring it down to an acceptable level. I will update the thread when I have tried it. I'm not putting in another component to do Dolby NR.

    THe speakers in your picture are the 3678 as you mention. They have a tiny horn compared to the 4722, but the LF is pretty much the same. Just a little smaller, but same driver.

    EDIT: The hiss with the Behringer DCX is not as bad as you make it sound... I'm just annoyed that its noticeable when I am listening for it! But when watching a movie, I dont notice it.
    That was joke about the Dolby NR.

    Easy the level down or place a few equal HP filters over LCR HF and cut the level back. I trust the LF gives planet of bass mid and often deep lows around the 40Hz range.

    The soundtrack level will mask the noise of hiss because its running many db higher over the hiss!

  6. #21
    JBL 4645
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    The soundtrack level will mask the noise of hiss because its running many db higher over the hiss!

    Currently I have the levels on the amps set at like this a few nights ago the levels on the Alesis RA300 was at full but the levels on the MDX4600 was set differently. The levels for the HF on the Marantz 1050 for LCR HF are set way, way low I need to put my ear up to tweeter horns to hear any kind of hiss.

    Set the levels for a computable level if the soundtrack level is higher than the hiss how high is the HF on its own over LCR with LF muted and all other channels as well is the HF within a peak of 85db (90db or over) will be far too bright I'll be reaching for the volume for mine.

    I’m going to do a simple test! I’ll be back in jiffy!
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  7. #22
    Senior Member Eaulive's Avatar
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    This thread is too noisy, I quit.

  8. #23
    JBL 4645
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    I guess you hasn't got DOLBY SR type

  9. #24
    Senior Member 1audiohack's Avatar
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    Quote Originally Posted by Eaulive View Post
    This thread is too noisy, I quit.
    Well said, sadly incredible isn't it.
    If we knew what the hell we were doing, we wouldn't call it research would we.

  10. #25
    Senior Member Mctwins's Avatar
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    Hi
    What is this fuzz about hiss thing

    I am running my M/T with McIntosh MC252 and for my subs two Crown MAi5000 and have no problem with hiss no matter where my volume knob is. My system is dead silence even if I use dbx260 in the signal chain.

    There is alot of reason that can create hiss like power supply or bad interconnect or ground loop and so on....

    Jonas.. with your new Crown amps and dbx4800 you will have a brand new system and with no hiss.

    Thanks

  11. #26
    JBL 4645
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    Jonas_h

    Why don't you make a video so we can hear the hiss first hand. I made a quick video because I had one idea I haven't yet tried.


  12. #27
    Senior Member Lee in Montreal's Avatar
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    Just curious about the DBX 4800. What is the current street price?

  13. #28
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    Quote Originally Posted by Lee in Montreal View Post
    Just curious about the DBX 4800. What is the current street price?
    In Denmark where I live, its about $6000.. but Denmark is very expensive with electronics! I got it for $1800, so it was a no-brainer for me when I was looking for a new speaker processing component anyway. I dont know the price in The US.. Probably $4000-$4500?

  14. #29
    Obviously... not a golfer grumpy's Avatar
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    yes, appears to be ~$4000USD
    It's uh... uh... it's down there somewhere, let me take another look...

  15. #30
    Senior Member Lee in Montreal's Avatar
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    Quote Originally Posted by Jonas_h View Post
    In Denmark where I live, its about $6000.. but Denmark is very expensive with electronics! I got it for $1800, so it was a no-brainer for me when I was looking for a new speaker processing component anyway. I dont know the price in The US.. Probably $4000-$4500?

    $1800 is a gooood price considering it sells for more than three times this amount in your area. You got yourself a great deal. I like the fact that the 4800 is an 8 channel crossover. I wished my DCX had an extra channel for summed subs. But hey, for $340.00cad I can't complain.

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